Rolling Wave ClBt - Geskiedenis

Rolling Wave ClBt - Geskiedenis



We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Rolling Wave

(ClBt: t. 112)

Rolling Wave, 'n kanaalboot, is deur die vloot in Philadelphia aangekoop, gelaai met klip, en via Baltimore na die James River gestuur om op die kroeg in Trent's Reach, Va.


Vreemde, skaars wolke en die fisika daaragter

Om hierdie artikel weer te gee, besoek My profiel en bekyk dan gestoorde verhale.

Om hierdie artikel weer te gee, besoek My profiel en bekyk dan gestoorde verhale.

In Augustus plaas ons 'n foto van 'n paar vreemde, skaars wolke bekend as Morning Glory -wolke sonder om 'n verduideliking te gee van hoe dit vorm. In reaksie op lesersbelangstelling het ons opgevolg met die weerkundige Roger Smith van die Universiteit van München, wat die vorming daarvan bestudeer het.

"Deur die jare het ons 'n goeie begrip daarvan ontwikkel," het Smith gesê. 'Dit is nie meer 'n raaisel nie, maar steeds baie skouspelagtig.'

Die Morning Glory -verskynsel is die gevolg van die besondere opset van die land en die see op die Cape York -skiereiland, in 'n afgeleë deel van Australië. Die skiereiland tap af van ongeveer 350 myl breed tot 60 myl terwyl dit noord strek tussen die Golf van Carpentaria in die weste en die Koraalsee in die ooste. Die oostelike passaatwinde stoot bedags die seebries oor die skiereiland, wat laataand die seebries van die weskus af ontmoet. Die botsing veroorsaak 'n golfstoornis wat na die suidweste van die binneland beweeg, wat 'n belangrike deel van die wolkformasie is.

Namate vogtige seelug na die kruin van die golwe gelig word, word dit afkoel en kondensasie vorm 'n wolk. Soms is daar net een golf, maar Smith het al tien saam in 'n reeks gesien.

'As u na die wolke kyk, lyk dit asof hulle agteruit rol,' het Smith gesê. 'Maar in werklikheid word die wolke voortdurend aan die voorkant gevorm en aan die agterkant geërodeer. Dit gee 'n rollende voorkoms. ”

Hierdie wolke kom wel elders voor, insluitend München, waar dit ongeveer een keer in 'n dekade vorm. Cape York is uniek omdat dit gereeld in die herfs bokant die klein dorpie Burketown gebeur. En hulle kan ook daar veral indrukwekkend wees en tot 600 myl lank word. Vlieëniers vlieg elke jaar die gebied binne in die hoop om die interessante wolke te sien.

Nie baie wetenskaplikes bestudeer dit nie, of eintlik vreemde wolke, omdat dit uiters skaars is dat hulle relatief onbelangrik is om neerslag of klimaat te bestudeer. Die vorming daarvan word dus dikwels swak verstaan.

"Dit is moeilik om geld te kry om iets te bestudeer wat netjies lyk," het die wolkfisikus Patrick Chuang van die Universiteit van Kalifornië, Santa Cruz, gesê.

Op die volgende bladsye het ons foto's van 'n paar van die vreemdste, mooiste wolktipes versamel en wetenskaplikes gevra om ons te help verstaan ​​hoe dit vorm.

Hierdie vreemde, sakagtige formasies, wat bekend staan ​​as mammatuswolke, kom dikwels voor in samewerking met 'n donderstorm. Hulle is op baie plekke gesien, insluitend die midweste van die Verenigde State.

"Dit is wolke wat baie vreemd lyk," het die wolkfisikus Patrick Chuang gesê.

Maar wetenskaplikes het wel 'n paar teorieë oor mammoetwolke. 'N Ander wolkfisikus, Daniel Breed van die National Center for Atmospheric Research, sê dryfkrag en konveksie van lug is die sleutel.

"Hulle is soortgelyk aan onderstebo konveksie," het Breed gesê.

Konveksie is soos 'n lewendige borrel, het hy gesê. In mammutuswolke veroorsaak verdamping sakke van negatiewe dryfkrag, aangesien dit die lug in die wolk afkoel. Dit laat die wolke afwaarts blaas in plaas van omhoog soos kumuluswolke, en dit word uiteindelik soos onderstebo borrels.

Die rede waarom hulle glad is, is die termiese struktuur reg onder hulle. Die spoed waarteen die temperatuur daal met verhoogde hoogte, bekend as die 'quot -terugval -tempo', moet naby neutraal wees, het hy gesê. Met ander woorde, as u 'n warm borreltjie lug op 'n spesifieke plek plaas, sal dit glad nie styg of daal nie - geen hitte gaan in of uit nie. Dit is tipies van die termiese struktuur van donderstorms. Sonder hierdie omstandighede kry u meer algemene wolke wat uitgestrooi lyk of troebel struikelblokke uitkom.

"Waar jy ook al donderweer kry, kan dit beslis gebeur," het Breed gesê. 'U hoef nie donderstorms te hê nie, maar u moet atmosferiese toestande hê met 'n mate van dryfkrag.'

Soms word dit met UFO's vergelyk, maar lensvormige wolke word gewoonlik deur swaartekraggolwe geskep. Chuang roep los skokbrekers op om te beskryf wat swaartekraggolwe is.

'Neem u u ouma se Cadillac en ry dit oor 'n spoedhobbel, en daarna gaan dit 'n rukkie op en af,' het hy gesê. Die rede waarom jy gaan, is as gevolg van swaartekrag, en dan is daar bronne in die vering wat jou terugstoot. & quot

In die geval van lensvormige wolke is die spoedhobbel gewoonlik 'n soort topografie, soos 'n berg, wat die vloei van die lug in die pad steek. As die lug langs die berg afkom, is dit geneig om te oorskiet en dan weer op te spring. Dit ossilleer 'n rukkie so, en op die opwaartse deel van die golwe vorm wolke as stygende lug afkoel.

"Wolke is die hoogste deel van die ossillasie," het Chuang gesê.

Lentikulêre wolke kan ook veroorsaak word deur ander spoedwalle, soos hoë donderwolke, maar omdat dit dikwels aan die wind se kante van berge vorm, staan ​​dit ook bekend as leewolke, golfwolke of leewolfwolke.

'N Bergreeks kan 'n reeks langgolfwolke vorm, maar as die spoedhobbel meer geïsoleerd is, soos 'n enkele berg, kan dit 'n ovaalvormige wolke wees wat soos UFO's lyk. Soms word verskeie ovale gevorm wat soos 'n stapel pierings lyk.

"Ek hou van golfwolke omdat ek dit so gereeld hier sien," het Breed gesê oor Boulder, Colorado, waar NCAR is. Ek het baie gunstelinge, maar dit is die een wat ek op my skermbewaarder het. & quot (hieronder).

Beelde: Bo: Flickr/cardiffjackie. Onder: 1) Daniel Breed. 2) Betsy Mason, Wired.com. 3) NCAR/UCAR.

Hierdie mal wolke wat soos 'n ry golwe lyk, staan ​​bekend as Kelvin-Helmholz-golwe. Hulle vorm wanneer twee lae lug of vloeistof van verskillende digthede teen verskillende snelhede by mekaar verby beweeg, wat skeuring by die grens veroorsaak.

"Dit kan soos olie en asyn wees," het Chuang gesê. In die see is die bokant warm en die onderkant regtig koud. Dit is soos 'n dun lagie olie op 'n groot plas water. & Quot

As hierdie twee lae by mekaar verby beweeg, word 'n Kelvin-Helmholz-onstabiliteit gevorm wat soortgelyk is aan 'n golf. Dele van die grens beweeg op en dele beweeg af. Omdat die een laag vinniger as die ander beweeg, veroorsaak die skeer dat die golwe se toppe horisontaal beweeg, wat lyk soos 'n seegolf wat op die strand neerstort.

"Dit is regtig soos om golwe te breek," het Chuang gesê. 'n Golf breek as die water bo -op soveel vinniger beweeg as die water daaronder dat dit op sigself ophoop. & quot

Hierdie skouspelagtige foto van die uitbarsting van die Sarychev -vulkaan op die Kuril -eilande, noordoos van Japan op 12 Junie, toon 'n interessante voorbeeld van 'n pileuswolk. Dit lyk asof die aspluim 'n gladde wit dop het terwyl dit deur die wolkbedekking hierbo breek.

Hierdie tipe wolk word veroorsaak deur sterk, relatief vinnige opwaartse beweging. Situasies waar dit voorkom, sluit in vinnig groeiende donderkoppe, vulkaniese uitbarstings en selfs kernontploffings. In elke geval druk iets warm, klam lug vinnig opwaarts.

"U kan dit baie gereeld sien bo donderstorms, en dit omdat die lug so vinnig daarheen beweeg dat die lugvloei daarbo versteur word," het Breed gesê. En sodra dit genoeg afkoel om 'n wolk te vorm, kry u hierdie wolkdoppe. & quot

Chuang sê pileuswolke lyk soortgelyk aan die gladde kappies wat soms bo -op cumuluswolke gesien word, wat eintlik yskappe is.

"As jy 'n baie sterk konveksie het, wat vinnig en baie hoog stoot, vorm dit meer 'n yswolk omdat dit hoog genoeg is om die kristalle te vries," het Chuang gesê. "Dit is niks meer geheimsinniger as dinge wat vries nie."

Ons het in Julie hier bewus geword van nagtelike wolke by Wired Science toe die vreemde gloeiende wolke oor die Verenigde State en Europa begin verskyn het, veel verder suid as wat hulle normaalweg gesien word.

Hierdie "nagskynende" wolke word gevorm deur ys op die grens van die aarde se atmosfeer en ruimte, 50 myl hoog. Hulle skyn omdat hulle so hoog is dat hulle deur die son verlig bly, selfs al het dit onder die horison gegaan. Dit is nie duidelik waarom hierdie wolke van die pole af migreer nie, of waarom meer daarvan ook in die poolstreke verskyn en helderder skyn.

Niemand weet seker nie, maar die meeste antwoorde dui blykbaar op menslike atmosferiese veranderinge wat deur die mens veroorsaak word.

Die wolke vorm by temperature rondom minus-230 grade Fahrenheit, wanneer stof wat van onder opblaas of uit die ruimte in die atmosfeer val, oppervlaktes bied waarop waterdamp kan kondenseer en vries. Op die oomblik, gedurende die somer van die noordelike halfrond, word die atmosfeer warm en brei dit uit. Aan die buitekant van die atmosfeer beteken dit eintlik dat dit kouer word omdat dit verder in die ruimte gestoot word.

"Die heersende teorie en die mees aanneemlike verklaring is dat CO2 -opbou, 50 myl bo die oppervlak, die temperatuurverlaging sou veroorsaak," sê James Russell, 'n atmosferiese wetenskaplike aan die Hampton Universiteit en die hoofondersoeker van 'n lopende NASA -satellietsending om die wolke. Hy waarsku egter dat temperatuurwaarnemings onoortuigend bly.

Maar die waarheid kan baie meer kompleks wees, en daar is baie ander teorieë oor hierdie wolke.

Beelde: Bo: Mike Hollingshead, uiterste onstabiliteit. Onder: NCAR/UCAR

Morning Glory wolke is 'n spesifieke en meer ongewone tipe rolwolke, wat meer gereeld voorkom, en gewoonlik nie so lank nie.

Rolwolke kom tipies voor in die onderste atmosfeer voor 'n stormfront. Warm opstuwings in die stormfront druk koue lug op, wat dan langs die kante van die opwaartse kant afvloei. Die koue neerslag spring dan 'n bietjie terug en stel 'n golfagtige struktuur voor die storm op.

Met die opswaai vorm die koue lug 'n wolk. Verdamping van die wolk veroorsaak 'n afdraai aan die rande wat die wolk erodeer en 'n rol vorm. As die golf voortduur, kan 'n reeks rolwolke, 'n straat, genoem word.


10 Groot skeepswrakke

Ongelukke met vaartuie is nie nuut in die oseane en seë oor die hele aarde nie. Storms, ysberge en vele ander redes het duisende skeepswrakke op die seebodem laat lê.

Dit is egter net nie die oseane en seë waar die vaartuie ongelukke ondervind nie. Sommige van die varswaterliggame regoor die wêreld het ook gesien hoe 'n aansienlike aantal vaartuie jare lank onder die water sink en rus.

Die Groot Mere van Noord-Amerika is een van sulke prominente varswaterliggame.

Die Great Lakes, geleë in Noord -Amerika op die grens van Kanada - VSA, vorm 'n belangrike interne bevaarbare kanaal in die Sentraal -Noord -Amerikaanse streek.

Die Great Lake, wat die Atlantiese Oseaan verbind deur die Saint Lawrence -rivier, bestaan ​​uit vyf watermassas, waaronder Lakes Superior, Huron, Michigan, Erie en Ontario.

Omdat dit die grootste groep varswatermere ter wêreld is volgens hul totale oppervlakte, het die Great Lakes 'n geskiedenis van mariene vervoer sedert die 17de eeu.

Dit is egter nie maklik om deur hierdie watergebiede te reis nie en baie skepe in die verlede het geswig en onherroeplik in hul wervelende dieptes verloor.

Hierdie watermassas, ook bekend as binnelandse see, bied seevormige kenmerke soos golwende golwe, sterk strome en groot dieptes, en bied 'n moeilike tyd vir matrose wanneer hulle deur die streek reis.

Ontelbare skeepswrakke van sulke ongelukkige vaartuie is ontdek in die Groot Mere, wat aanleiding gegee het tot die konnotasie - Skeepswrakke van die Groot Mere, met selfs noemenswaardige museums wat as 'n opvoedkundige gedenkteken vir hierdie skeepswrakke van die Groot Mere gevestig is.

Volgens die Great Lakes Shipwreck Museum het die mere tot ongeveer 6 000 skepe laat sink en 30 000 mense is dood.

Die historikus Mark Thompson, die skrywer van Begraafplaas van die mere het beraam dat daar meer as 25000 skeepswrakke aan die onderkant van die Groot Mere is.

Met die fassinerende verhale agter hul insinking, is sommige van die skeepswrakke in die Groot Mere nou gewilde duikbestemmings. Hier is 'n lys van tien sulke noemenswaardige skeepswrakke van die Groot Mere.

1. Le Griffon

Le Griffon, 'n 17de-eeuse bakkie, is een van die grootste raaisels van die Groot Mere. Le Griffon is vermis in 1679 in Lake Michigan, en is vermoedelik die eerste grootseilskip wat op die boonste groot mere van Noord-Amerika geloop het.

Daar is egter in die verlede meer as twintig bewerings gemaak oor die ontdekking daarvan, en die meeste bewerings is verkeerd bewys.

Le Griffon, gebou deur die Franse ontdekkingsreisiger René Robert Cavelier, Sieur de La Salle, het in 1679 'n eiland in die Michiganmeer bereik nadat hy die Erie -meer en die Huron -meer oorgesteek het.

Tydens sy terugreis van die eiland na Nigerië, het die vaartuig vermis geraak in 'n gebied wat nou bekend staan ​​as Green Bay.

In 2001 beweer 'n beroemde Great Lakes -skeepswrakjagter Steve Libert die ontdekking van sy wrak in die Noordelike Lake Michigan naby Poverty Island.

Net so het die skattejagters Kevin Dykstra en Frederick J. Monroe in 2014 die ontdekking van die wrak naby Frankfort, Michigan, geëis.

2. Edmund Fitzgerald

Die sage van die vaartuig Edmund Fitzgerald is een van die gewildste verhaaltjies oor die skipbreuk van die Great Lake. Fitzgerald, wat in 1958 gelanseer is, was dertien jaar lank, tot 1971, die grootste skip op die Great Lakes.

Die Amerikaanse Great Lakes -vragskip is gedurende die wintermaand November in die jaar 1975 op die Lake Superior noodlottig verongeluk met al sy bemanning wat hul lewens verloor het.

Die vaartuig het 'n hewige storm ondergaan terwyl hy van Superior, Wisconsin, na 'n staalfabriek naby Detroit gereis het en in Kanadese waters gesink het.

Die wrak van Edmund Fitzgerald is in November 1975 deur 'n Amerikaanse Navy Lockheed P-3 Orion-vliegtuig ontdek terwyl dit ongeveer 25 kilometer wes van Deadman ’s Cove, Ontario, gelê het.

'N Opvallende vonds uit die wrak bly die vaartuig se gong, wat nou met trots uitgestal word in die skipbreukmuseum wat spesiaal toegewy is aan sulke ongevalle en wrakke van die Groot Mere.

3. Carl D. Bradley

SS Carl D. Bradley, 'n Great Lakes -vragskip, is in 1927 gebou en staan ​​bekend as die "Queen of the Lakes ”" vir die volgende 22 jaar sedert dit die langste en grootste vragskip op die waters van die Great Lakes was gedurende die periode .

Hierdie self-los vragskip wat as ysbreker en vragskip gebruik is, het in 1957 met 'n ander vaartuig, die MV White Rose, gebots en sy romp beskadig.

In die volgende jaar het die vaartuig in 'n storm beland en in Lake Michigan gesink en 33 bemanningslede doodgemaak.

Die sink van die vaartuig is veroorsaak deur strukturele skade. Die wrak van Carl D. Bradley, wat 360 voet onder die water lê, is in 1959 deur die Army Corps of Engineers ontdek.

4. Fedora

Die 282 voet lange grootmaat vervoerder Fedora was een van die groter klasse vragmotors gedurende daardie tydperk. Die vaartuig het in 1901 'n brandongeluk beleef toe hy van Duluth na Ashland onderweg was om ystererts te bring.

Een van die sterkste vaartuie wat destyds gebou is, het die Fedora sy ongekende lot bereik as gevolg van 'n brand in die enjinkabine aan die begin van die 20ste eeu.

Alhoewel niemand van die bemanning aan boord van die vaartuig hul lewens verloor het nie, het die Fedora spoedig 'n verlore saak geword toe dit heeltemal in die waters van die Creek Chicago in Buffalo Bay verdrink het.

Die skipbreuk van die Great Lake van die vaartuig Fedora lê in die dieptes van Lake Superior.

5. John B. Cowle

Dit val onder die grootvragte grootvragmotors, bekend as “ blikpanne, ”het die sewejarige John B. Cowl in 1909 met haar reis na 'n ramp begin. John B. Cowle was noodlottig verpletter toe 'n ander skip daarmee bots en 14 van haar 24 bemanningslede in die buiteland doodmaak.

Dik misvelle verhoed duidelike sigbaarheid wat gelei het tot die botsing van die vaartuie, hoewel die botsende vaartuig 'n belangrike rol gespeel het in die redding van baie van die oorlewende lede van die vernielde Cowle -skip.

Die wrak van die vaartuig is in 1972 ontdek en dit is een van die opmerklik goed bewaarde wrakke in Lake Superior.

Onmiddellik na die sinking van John B. Cowle, is 'n tweede John B. Cowle in gebruik geneem in 1910. Die tweede vaartuig is tot 1978 suksesvol bedryf.

6. Wene

Vir ewig verlore in die waters van Lake Superior, het die stoomskip Wenen in September 1892 noodlottig neergestort nadat dit teen 'n ander stoomskip per ongeluk uit die teenoorgestelde rigting op haar afgekom het.

Wene, wat in 1873 ingebou is, het gedurende haar 19-jarige loopbaan verskeie ongelukke beleef, waaronder 'n insinking na drie jaar se bekendstelling.

Tydens die finale ongeluk was beide die vaartuie, Wene en Nipigon, swaar met 'n vrag ystererts.

Deurdat die ander vaartuig die Wene in veiligheid probeer trek het, verhoed die stelle 'n suksesvolle reddingsoperasie. Die wrak van die vaartuig is in 1975 ontdek en lê 120 tot 148 voet onder die water.

7. Lady Elgin

Lady Elgin, 'n houtskip-stoomskip, was 'n skip wat in 1851 gebou is en dien as passasierskip op die Groot Mere. Op 6 September 1860, tydens sy terugkeer uit Chicago saam met die lede van Milwaukee's Union Guard na 'n veldtogrede deur Stephen A.

Douglas, die 252-voet Lady Elgin, staar 'n sterk storm in die gesig en word deur die skoener Augusta van Oswego gestamp. As gevolg van die skade wat deur die botsing veroorsaak is, het die vaartuig later gesink, wat die dood van meer as 300 mense tot gevolg gehad het.

In 1989 is die wrak van die Lady Elgin by Highwood, Illinois, deur Harry Zych ontdek.

Die wrakplek van Lady Elgin, waarin vier hoofafval van die vaartuig wat in 50-60 voet water lê, deur die Underwater Archaeological Society of Chicago gekatalogiseer is.

8. Samuel Mather

Die Samuel Mather is nog 'n voorbeeld van twee vaartuie wat in die gevaarlike waters van Whitefish Bay teen mekaar bots.

Terwyl hy koring uit die hawe Duluth gestuur het, het Samuel Mather vroegoggend in November 1981 met die stoomskip Brasilië gebots weens dik mis in Whitefishbaai, Lake Superior.

Die hele bemanning van die Samuel Mather is veilig gered deur die stoomboot Brasilië. Tans lê die wrak van die Mather in 180 voet water, 30 myl van die hawe by Whitefish Point.

Samuel Mather is een van die belangrikste ondersoekende en duikvakke vir entoesiaste, veral vanweë die posisie in die water.

9. Prins Willem V

Die 258 voet lange vragskip Prins Willem V sak in Oktober 1964 in die Michiganmeer nadat hy sedert 1949 vir die Orange Line jare tussen Europa en die Verenigde State gevaar het.

Die Nederlandse vragskip het drie myl van die hawe van Milwaukee omgeslaan nadat hy met Sinclair Oil Company Barge gebots het. Alle bemanningslede aan boord van die vaartuig is gered.

Na die ongeluk was daar baie pogings om die vaartuig in 1958, 1961 en sommige na 1965 op te hef, maar almal het misluk.

Die wrak van Prins Willem V, bekend as die 'Willie', is ongeskonde aan stuurboordkant van ongeveer 80 m, en is een van die gewildste wrakke in Milwaukee.

10. John M. Osborn

Die laaste vaartuig in hierdie lys van skeepswrakke van die groot mere is die houtstoomboot John M. Osborn, wat in 1884 in die Whitefish Point verwoes is.

Net soos baie van die bogenoemde vaartuie, het wasige en mistige toestande die kennis van 'n naderende vaartuig verhinder, wat veroorsaak dat beide John M. Osborn staalomhulsel Alberta met die Osborn bots.

'N Paar bemanningslede is dood aan die ongeluk wat teen die einde van die 19de eeu plaasgevind het. Die wrak van John M. Osborn is 100 jaar na die ongeluk, in 1984, ontdek en in 165 meter water in Whitefish Bay van Lake Superior gelê.

'N Skipbreukmuseum saam met 'n stigtingsvereniging om entoesiaste toe te laat om meer oor hierdie wrakstukke te verstaan, is gevestig.

Deur sulke tasbare organisasies word 'n groter wydverspreide bereik oor die besonderhede en die bevindings van hierdie skeepswrakke verwag.

U sal ook graag wil lees:

Vrywaring:Die skrywers se standpunte in hierdie artikel weerspieël nie noodwendig die standpunte van Marine Insight nie. Data en kaarte, indien gebruik, in die artikel is verkry uit beskikbare inligting en is nie deur 'n statutêre owerheid geverifieer nie. Die skrywer en Marine Insight beweer nie dat dit akkuraat is nie, en aanvaar ook geen verantwoordelikheid daarvoor nie. Die menings vorm slegs die menings en vorm geen riglyne of aanbeveling oor die optrede wat die leser moet volg nie.

Die artikel of beelde kan nie in enige vorm gereproduseer, gekopieer, gedeel of gebruik word sonder die toestemming van die outeur en Marine Insight

Op soek na praktiese maar bekostigbare maritieme hulpbronne?

Kyk na die digitale gidse van Marine Insight:

e -boeke vir dekafdeling - Hulpbronne oor 'n verskeidenheid onderwerpe wat verband hou met dekmasjinerie en -bedrywighede.

e -boeke vir motorafdeling - Hulpbronne oor 'n verskeidenheid onderwerpe wat verband hou met die masjinerie en werking van die motorruimte.

Bespaar groot met kombinasiepakkette - Bundels met digitale hulpbronne wat u help om groot te spaar en ekstra gratis bonusse bevat.

eBoeke oor mariene elektriese stelsels - Digitale hulpbronne vir ontwerp, onderhoud en probleemoplossing van mariene elektriese stelsels


Inleiding

Veselversterkte komposiete word wyd gebruik in nywerhede soos lugvaart, ruimtevaart, motorvoertuie en robotte [1], [2], [3], [4], [5], [6], omdat hierdie materiale hoë sterkte het -gewig, styfheid-tot-gewig-verhoudings en hul strukturele gedrag hang af van die vesel-oriëntasie daarvan en die aard van die stapel-stapelvolgordes [1], [3], [4], [5], [6]. Een van die praktiese toepassings is saamgestelde lemme in moderne rotorsisteme. 'N Ander toepassing is die slim saamgestelde strukture met ingeboude toestelle, soos mikro-aandrywers, sensors en elektronika. Dit is dus moontlik om gepaste lamineringsparameters te ontwerp en skuifvervormingseffekte te benut of te vermy om die kwaliteit van saamgestelde strukture te verbeter en bied talle voordele [2], [4]. Vanweë hul anisotropiese aard kan die afskuiwingsvervormingseffekte nie geïgnoreer word tydens die berekening van gelamineerde komposietmateriaal [7] nie, veral beïnvloed dit die akkuraatheid van die ontleding van die dinamika -respons van gelamineerde komposietmateriaal en hul strukture. Daarom is dit belangrik om 'n nuwe ontledingsmodel op te stel om die verbygaande reaksies van gelamineerde saamgestelde strukture akkuraat te voorspel. En een van die belangrikste probleme is om 'n geskikte ontledingsmetode te vind om die kortstondige dinamika -antwoorde op te los.

Daar is 'n paar literatuur wat die verbygaande dinamika -reaksie en impakgedrag van saamgestelde balke bestudeer het, gebaseer op die klassieke lamineringsbundelteorie (CLBT). Byvoorbeeld, Maiti et al. [8] ondersoek die impakgedrag van gelamineerde saamgestelde balke met eindige element metode (FEM). Dit word bevestig dat die golf -voortplantingsbenadering 'n belangrike manier is in dinamiese analise van strukture. Doyle [9] het die spektrale elementmetode (SEM) ontwikkel en die SEM [10] gebruik om die golfverspreiding in staaf- en bundeltipe strukture te ontleed. Mahapatra et al. gebruik SEM om die golfverspreiding en verbygaande dinamiese reaksie van vermenigvuldig gekoppelde asimmetries gelamineerde saamgestelde balke [11] te ontleed. Abramovich et al. [12] bestudeer vrye vibrasie van nie-simmetriese dwarslaag gelamineerde saamgestelde balke. Chakraborty et al. [13] het ondersoek ingestel na vrye vibrasie en golfpropagasie in asimmetriese saamgestelde balke met FEM. Hierdie resultate gebaseer op CLBT verwaarloos die dwarsskuifvorming heeltemal, wat die toediening daarvan slegs tot dun gedeeltes beperk. Vir die anisotrope balke en hul strukture, omdat die verhouding van die uitbreidingsmodulus tot die dwarsskuifmodule hoog is, kan die vervorming as gevolg van afskuiwing egter nie geïgnoreer word nie, selfs vir 'n redelik groot slankheidsverhouding (L/h) [14], [15], die analise van die verbygaande dinamika -antwoorde gebaseer op CLBT is nie genoeg akkuraat nie, veral by hoë frekwensies. Boonop kan ply-stacking-rye ook die gedrag van komposiete aansienlik verander. Die effekte van skuifvervorming van laagstapel is duidelik. As die lae byvoorbeeld oneweredig om die middelvlak van die komposiete gestapel is, bestaan ​​daar gekoppelde aksiale-buigeffekte. Daar is baie verteenwoordigende literatuur oor hierdie aspek, soos Teoh et al. het die invloed van skuifvervorming en roterende traagheid op die vrye vibrasies van veselversterkte, saamgestelde balke ondersoek op grond van 'n teoretiese ontledingsmetode. 'N Illustratiewe voorbeeld is uitgewerk om die effek van skuifvervorming en veseloriëntasie [16] aan te toon. Ömer het 'n diskrete enkelvoudige konvolusie (DSC) metode ontwikkel vir statiese ontleding van dik simmetriese dwars-gelaagde saamgestelde plate wat gebaseer is op die eerste-orde skeer vervormingsteorie [17]. Chandrashekhara et al. presiese oplossings gekry het vir die vrye vibrasie van simmetries gelamineerde saamgestelde balke, wanneer die eerste orde skuifvervorming en roterende traagheid in die analise [1] in ag geneem word. Abramovich [18] het presiese oplossings aangebied vir simmetries gelamineerde balke met tien verskillende randvoorwaardes, insluitend skuifvervorming en roterende traagheid, maar die gesamentlike werkingsterm van die twee effekte word weggelaat. Eisenberger et al. het die dinamiese styfheid van gelamineerde saamgestelde balke afgelei en die presiese vibrasie frekwensies bepaal met behulp van die eerste-orde skuifvervormingsteorie, insluitend die effek van roterende traagheid en skuifvervormings [19]. Die skuifvervormingseffekte in gelamineerde balke is meer betekenisvol as in homogene balke, omdat die verhouding van rekstyfheid tot die dwars skuifstyfheid hoog is. Chakraborty et al. het 'n nuwe verfynde, sluitingsvrye eerste-orde skeer-vervormbare eindige element aangebied om die vrye vibrasie en golfverspreiding in gelamineerde saamgestelde balkstrukture met simmetriese sowel as asimmetriese laagstapeling [13] op te los. 'N Nuwe manier om strukturele diskontinuïteite te modelleer word gegee, wat die modelleringspoging van die bepaling van dinamiese en golf -voortplantingsreaksies vinnig en akkuraat aansienlik verminder. Mahapatra et al. het die effekte van aksiale -buiging -skuif in golfpropagasie in gelamineerde saamgestelde balke met behulp van die spektrale eindige element -metode aangebied. In hul werk is die omvang van geldigheid van die eerste-orde skuifvervorming in die konteks van hoër-orde lamgolfmodusse bespreek [13], [20]. Dit is egter moeilik om die inverse matriks van 'n styfheidsmatriks te identifiseer deur SEM en FEM te gebruik tydens die oplosproses.

Reverberation-ray matrix (RRM) analise is 'n frekwensie-domein matriks metode, wat voorgestel word deur Howard et al. [21]. Dit is geskik vir die evaluering van die verbygaande reaksies van truss-tipe strukture en vir die bestudering van verbygaande elastiese golftransmissie in strukture. Die meeste frekwensie domein matriks metodes ly aan sekere probleme as gevolg van frekwensie-afhanklike matrikselemente, wat singulariteit by die resonante frekwensies van strukture aanbied. Om hierdie probleme op te los, gebruik RRM -analise 'n uitbreidingstegniek van die Neumann -reeks [22]. RRM-analise kan ook gebruik word om akkuraat en effektief die verbygaande reaksies van oneindige lae media [23], [24], vlakke kappe [25] en ruimtebakke [26], [27] te ondersoek. Pao et al. [25] het die verbygaande reaksies van plat kappe met stywe of vasgemaakte gewrigte ondersoek deur suksesvol RRM -analise te gebruik. Guo et al. [26], [27] het die tegniek toegepas om die verbygaande reaksies van ruimtetakke effektief en gemaklik te kry. Chen et al. [28] het RRM -analise gebruik om die effek van kousaliteit op verbygaande respons te analiseer. Die outeurs het ontdek dat die oorsaaklike toestande die vroeë korttermyn-reaksies van strukture natuurlik beïnvloed, maar dat dit 'n minimale langtermynreaksie het. Pao et al. [29] het die eienskappe van RRM hersien en vergelyk met dié van die oordragmatriksmetode. Eersgenoemde verkry vroeë korttermyn-antwoorde akkuraat, terwyl laasgenoemde sulke antwoorde onakkuraat bereken, gegewe sy numeriese onstabiliteit tydens omkeringsoplossing. Liu et al. [30] het RRM-analise en die veralgemeende straalmetode (GRM) gebruik om die vroeë korttermyn-verbygaande respons van 'n L-vormige plaat [31], [32] te bestudeer. Die reaksies afgelei deur RRM -analise is dieselfde as die wat deur GRM verkry is. Miao et al. [33] het 'n nuwe model -analise metode aangeneem volgens die RRM analise. Daar word bevind dat die natuurlike frekwensies van kussings bepaal word deur die frekwensieresponsfunksie (FRF), en die vibrasiemodusse word opgetel uit die aangrensende matriks van die koëffisiëntmatriks van die RRM -vergelykings. Dit kan duidelik gesien word dat RRM -analise meer uitgebreide toepassings het.

Soos bekend aan navorsers, kom gekoppelde effekte in die gelamineerde saamgestelde balke en hul strukture gelaaide slagkragte uit. Die gekoppelde effekte is een van die belangrikste punte om verbygaande reaksies en golfverspreiding van gelamineerde saamgestelde balke te ondersoek. 'N Paar ondersoeke na die gekoppelde effekte in gelamineerde saamgestelde balke en in die struktuur van 'n truss-tipe gemaak van gelamineerde saamgestelde balke is gerapporteer [1], [2], [3], [11], [12], [13], [ 14], [15], [34], [35]. Byvoorbeeld, Chai et al. [34] ondersoek die gekoppelde effekte van buig-, buig- en vrytrillings op algemeen toegepaste gelamineerde saamgestelde balke. Daar is gevind dat die gekoppelde reaksie 'n belangrike veranderlike is wat by die berekening van die effektiewe buigstyfheid van gelamineerde saamgestelde balke ingesluit moet word. Hajianmaleki [35] het aanvaar dat 'n aanvaarbare benadering om gekoppelde parameters in te sluit, die styfheidsparameters herdefinieer, sodat ander koppelings by die oplossing ingesluit word. Die koppelingsprobleme kan opgelos word deur ekwivalente styfheidsparameters in plaas van die normale definisies vir A11, B11, en D11. Mahapatra et al. [20] demonstreer 'n spektrale eindige elementmodel om die aksiale-buig-skuif-gekoppelde golf-voortplanting in gelamineerde saamgestelde balke aan te bied, en definieer twee nie-dimensionele aksiale-buig-gekoppelde parameters en 'n nie-dimensionele buig-skuif gekoppelde parameter, en onthul dus die die essensie van die kenmerke van golfverspreiding en die oorgangsreaksies akkuraat voorspel in gelamineerde saamgestelde balke wat impakkragte belaai het.

In ons vorige studies het ons die dinamiese reaksie en aksiale -buig -gekoppelde effekte van klassieke gelamineerde saamgestelde balke suksesvol ontleed met behulp van RRM -analise metode, in vergelyking met die eindige element metode (FEM), die ondersoekde resultate van RRM en FEM analise toon goeie ooreenkoms, die oplossing van die RRM is nie net eenvoudiger en vinniger nie, maar benodig ook minder rekenaarelemente [36]. Daarom is dit geïnteresseerd om die RRM-analise te ontwikkel op die gebied van verbygaande reaksies, gekoppelde effekte en gekoppelde golfpropagasie in gelamineerde saamgestelde balke wat beskou word as die eerste orde skuifvervormingseffekte. Daar is egter geen werk gedoen om RRM -analise te gebruik om die gevolge van skuifvervorming, aksiale -buig -skuif gekoppelde en verbygaande reaksies in gelamineerde saamgestelde balke en hul strukture te bepaal nie. As 'n voorlopige benadering vir die bepaling van die verbygaande reaksies van truss-tipe strukture gemaak van gelamineerde saamgestelde balke, ondersoek hierdie navorsing die gedrag van asimmetries gelamineerde saamgestelde balke wat aan impulskragbelasting blootgestel word, en strek die RRM-analise tot die asimmetries gelamineerde balk om dit te doen. Ons lei die verstrooiings- en nagalmmatrikse van die gelamineerde saamgestelde balke op grond van die eerste-orde skuifvervormingsteorie (FSDT), soos uiteengesit in afdeling 2.

In die huidige werk bevestig ons ons analise-benadering volgens die eerste-orde skeer vervormingsteorie (FSDT) wat die effek van skuifvervorming en traagheid insluit. This study deals with the behavior of asymmetrically laminated composite beam subjected to pulse type load. The scattering and reverberation matrix of the laminated composite beams based on FSDT are derived through RRM analysis. In Section 3, to validate the analysis the velocity response of a laminated cantilever beam under a smoothed triangular force pulse are obtained and compared with the results of spectral finite element method and finite element method of Ref. [13]. Then, the velocity response of a laminated cantilever beam with different ply-stacking sequence under a half-cycle force pulse and a rectangular force pulse are respectively solved. Natural frequencies of a laminated simply supported beam are investigated by RRM analysis. Coupled of axial–flexural–shear effects are discussed. Furthermore, the effects of beam models, slenderness ratio of the beam and beam theory (CLBT and FSDT) are analyzed and discussed by RRM analysis. In addition, we obtain spectral relation for various axial–flexural–shear coupled coefficients by RRM analysis.


State Voting Bills Tracker 2021

State lawmakers continue to introduce voting and elections bills at a furious pace.

In conjunction with the Brennan Center’s rapporteer on state voting proposals, below is a list of the restrictive and expansive bills that we are tracking to date.

As of May 14, 2021, legislators have introduced 389 bills met restrictive provisions in 48 states. Twenty-two bills with restrictive provisions have already been enacted. In addition, at least 61 bills with restrictive provisions in 18 states are moving through legislatures: 31 have passed at least one chamber, while another 30 have had some sort of committee action (e.g., a hearing, an amendment, or a committee vote).

Note that, in some cases, a single bill can have provisions with both restrictive and expansive effects.


Oceanography has all the answers to the classic surfing questions and enigmas. Science teaches surfers how ocean waves are formed en why they break as they do.

There are multiple variables at stake: sun, wind, energy, geographical obstacles, tides, and many other factors.

Experienced surfers know how and when the waves are breaking perfectly.

For avid wave hunters, perfect waves are waves that peel continuously from left to right, or vice-versa, rather than closing out abruptly.

Surfers can be picky. Wave explorers need the right swell angle, a special ocean bottom, and favorable wind speed and direction to ride long joyful waves.

There is a huge difference between taking off on a wave and riding it for 100 yards (91.4 meters) and surfing a wave for five seconds.

There are four types of breaking waves: spilling, plunging, collapsing, and surging. And that's all we can expect from Mother Nature. It's all there is.

Discover them, and improve your surfing:

Spilling Waves

Spilling waves are waves that are produced when the ocean floor has a gentle slope.

As the wave approaches the shore, it slowly releases energy, and the crest gradually spills forward down its face until it is all whitewater.

These waves take more time to break than any other wave. Surfers usually call these waves "mushy waves."

Plunging Waves

Plunging waves are formed when the incoming swell hits a steep ocean floor or a sea bottom with sudden depth changes.

As a result, the wave's crest curls over and explodes on the trough. The air under the lip of the wave is compressed, and a crashing sound is often heard.

Plungers are more common in offshore wind conditions.

Surging Waves

Surging waves are produced when long period swells arrive at coastlines with steep beach profiles.

The base of the wave moves fast and does not allow the crest to evolve. As a result, the wave almost doesn't break, and there is little whitewater.

Surging waves look friendly but can be quite deadly because of the backwash associated with them.

Collapsing Waves

Collapsing waves are a blend between surging and plunging waves.

The crest never completely breaks, and the bottom face of the wave gets vertical and collapses, resulting in whitewater.


Bowen, S., Chawla, N., Collins, S. E., Witkiewitz, K., Hsu, S., Grow, J., et al. (2009). Mindfulness-based relapse prevention for substance use disorders: a pilot efficacy trial. Substance Abuse, 30(4), 295–305.

Bowen, S., Chawla, N., & Marlatt, G. A. (2010). Mindfulness-based relapse prevention for addictive behaviors: a clinician’s guide. Guilford Press.

Bowen, S., Witkiewitz, K., Clifasefi, S. L., Grow, J., Chawla, N., Hsu, S. H., et al. (2014). Relative efficacy of mindfulness-based relapse prevention, standard relapse prevention, and treatment as usual for substance use disorders. JAMA Psychiatry, 71(5), 547–556.

Brewer, J. A., Sinha, R., Chen, J. A., Michalsen, R. N., Babuscio, T. A., Nich, C., et al. (2009). Mindfulness training and stress reactivity in substance abuse: results from a randomized, controlled stage I pilot study. Substance Abuse, 30(4), 306–317.

Chawla, N., Collins, S., Bowen, S., Hsu, S., Grow, J., Douglas, A., & Marlatt, G. A. (2010). The mindfulness-based relapse prevention adherence and competence scale: development, interrater reliability, and validity. Psychotherapy Research, 20(4), 388–397.

de Dios, M. A., Herman, D. S., Britton, W. B., Hagerty, C. E., Anderson, B. J., & Stein, M. D. (2012). Motivational and mindfulness intervention for young adult female marijuana users. Journal of Substance Abuse Treatment, 42(1), 56–64.

Elwafi, H. M., Witkiewitz, K., Mallik, S., Thornhill IV, T. A., & Brewer, J. A. (2013). Mindfulness training for smoking cessation: moderation of the relationship between craving and cigarette use. Drug and Alcohol Dependence, 130(1), 222–229.

Enkema, M. C., & Bowen, S. (2017). Mindfulness practice moderates the relationship between craving and substance use in a clinical sample. Drug & Alcohol Dependence, 179, 1–7.

Feldman, G., Hayes, A., Kumar, S., Greeson, J., & Laurenceau, J. P. (2007). Mindfulness and emotion regulation: the development and initial validation of the Cognitive and Affective Mindfulness Scale-Revised (CAMS-R). Journal of Psychopathology and Behavioral Assessment, 29(3), 177–190.

Flannery, B. A., Volpicelli, J. R., & Pettinati, H. M. (1999). Psychometric properties of the Penn alcohol craving scale. Alcoholism: Clinical and Experimental Research, 23(8), 1289–1295.

Garland, E. L., & Howard, M. O. (2018). Mindfulness-based treatment of addiction: current state of the field and envisioning the next wave of research. Addiction Science & Clinical Practice, 13(1), 14.

Garland, E. L., Roberts-Lewis, A., Tronnier, C. D., Graves, R., & Kelley, K. (2016). Mindfulness-oriented recovery enhancement versus CBT for co-occurring substance dependence, traumatic stress, and psychiatric disorders: Proximal outcomes from a pragmatic randomized trial. Behaviour Research and Therapy, 77, 7–16.

Glasner, S., Mooney, L. J., Ang, A., Garneau, H. C., Hartwell, E., Brecht, M. L., & Rawson, R. A. (2016). Mindfulness-based relapse prevention for stimulant dependent adults: a pilot randomized clinical trial. Mindfulness, 1–10.

Gossop, M., Darke, S., Griffiths, P., Hando, J., Powis, B., Hall, W., & Strang, J. (1995). The Severity of Dependence Scale (SDS): psychometric properties of the SDS in English and Australian samples of heroin, cocaine and amphetamine users. Addiction, 90(5), 607–614.

Grant, S., Colaiaco, B., Motala, A., Shanman, R., Booth, M., Sorbero, M., & Hempel, S. (2017). Mindfulness-based relapse prevention for substance use disorders: a systematic review and meta-analysis. Journal of Addiction Medicine, 11(5), 386.

Grow, J. C., Collins, S. E., Harrop, E. N., & Marlatt, G. A. (2015). Enactment of home practice following mindfulness-based relapse prevention and its association with substance-use outcomes. Addictive Behaviors, 40, 16–20.

Hayes, A. F., & Rockwood, N. J. (2017). Regression-based statistical mediation and moderation analysis in clinical research: observations, recommendations, and implementation. Behaviour Research and Therapy, 98, 39–57.

Hoeppner, B. B., Kelly, J. F., Urbanoski, K. A., & Slaymaker, V. (2011). Comparative utility of a single-item versus multiple-item measure of self-efficacy in predicting relapse among young adults. Journal of Substance Abuse Treatment, 41(3), 305–312.

Kabat-Zinn, J. (1990). Full catastrophe living: Using the wisdom of your body and mind in everyday life. New York: Delacorte.

Kazdin, A. E. (2007). Mediators and mechanisms of change in psychotherapy research. Annual Review of Clinical Psychology, 3, 1–27.

Khoury, B., Lecomte, T., Fortin, G., Masse, M., Therien, P., Bouchard, V., & Hofmann, S. G. (2013). Mindfulness-based therapy: a comprehensive meta-analysis. Clinical Psychology Review, 33(6), 763–771.

Koob, G. F., & Volkow, N. D. (2016). Neurobiology of addiction: a neurocircuitry analysis. Lancet Psychiatry, 3(8), 760–773.

Li, W., Howard, M. O., Garland, E. L., McGovern, P., & Lazar, M. (2017). Mindfulness treatment for substance misuse: a systematic review and meta-analysis. Journal of Substance Abuse Treatment, 75, 62–96.

McHugh, R. K., & Barlow, D. H. (2010). The dissemination and implementation of evidence-based psychological treatments: a review of current efforts. American Psychologist, 65(2), 73–84.

McKay, J. R. (2009). Treating substance use disorders with adaptive continuing care. Amerikaanse sielkundige vereniging.

McLellan, A. T., Lewis, D. C., O’Brien, C. P., & Kleber, H. D. (2000). Drug dependence, a chronic medical illness. JAMA, 284(13), 1689–1695.

McLellan, A. T., McKay, J. R., Forman, R., Cacciola, J., & Kemp, J. (2005). Reconsidering the evaluation of addiction treatment: from retrospective follow-up to concurrent recovery monitoring. Addiction, 100(4), 447–458.

Mermelstein, L. C., & Garske, J. P. (2015). A brief mindfulness intervention for college student binge drinkers: a pilot study. Psychology of Addictive Behaviors, 29(2), 259–269.

Muthén, L. K., & Muthén, B. O. (1998). Mplus user’s guide (8th ed.). Los Angeles: Muthén & Muthén.

Nunes, E. V., Gordon, M., Friedmann, P. D., Fishman, M. J., Lee, J. D., Chen, D. T., et al. (2018). Relapse to opioid use disorder after inpatient treatment: protective effect of injection naltrexone. Journal of Substance Abuse Treatment, 85, 49–55.

Raes, F., Pommier, E., Neff, K. D., & Van Gucht, D. (2011). Construction and factorial validation of a short form of the self-compassion scale. Clinical Psychology & Psychotherapy, 18(3), 250–255.

Segal, Z. V., Williams, J. M. G., & Teasdale, J. D. (2002). Mindfulness-based cognitive therapy for depression: a new approach to preventing relapse. New York: Guilford Press.

Shorey, R. C., Elmquist, J., Gawrysiak, M. J., Strauss, C., Haynes, E., Anderson, S., & Stuart, G. L. (2017). A randomized controlled trial of a mindfulness and acceptance group therapy for residential substance use patients. Substance Use & Misuse, 52(11), 1400–1410.

Ware Jr., J., Kosinski, M., & Keller, S. D. (1996). A 12-Item Short-Form Health Survey: construction of scales and preliminary tests of reliability and validity. Medical Care, 34, 220–233.

Whiteford, H. A., Degenhardt, L., Rehm, J., Baxter, A. J., Ferrari, A. J., Erskine, H. E., et al. (2013). Global burden of disease attributable to mental and substance use disorders: findings from the Global Burden of Disease Study 2010. The Lancet, 382(9904), 1575–1586.

Wilson, A. D., Roos, C. R., Robinson, C. S., Stein, E. R., Manuel, J. A., Enkema, M. C., et al. (2017). Mindfulness-based interventions for addictive behaviors: Implementation issues on the road ahead. Psychology of Addictive Behaviors, 31(8), 888.

Witkiewitz, K., Warner, K., Sully, B., Barricks, A., Stauffer, C., Thompson, B. L., & Luoma, J. B. (2014). Randomized trial comparing mindfulness-based relapse prevention with relapse prevention for women offenders at a residential addiction treatment center. Substance Use & Misuse, 49(5), 536–546.

Zemestani, M., & Ottaviani, C. (2016). Effectiveness of mindfulness-based relapse prevention for co-occurring substance use and depression disorders. Mindfulness, 7(6), 1347–1355.


What Happens When It Hits Land

A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. This retreating of sea water is an important warning sign of a tsunami, because the wave’s crest and its enormous volume of water typically hit shore five minutes or so later. Recognizing this phenomenon can save lives.

A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore. People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable locations.

Some tsunamis do not appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas.

The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea. Similar systems are proposed to protect coastal areas worldwide.


California blackouts are Public Utilities Commission’s fault, grid operator says

California’s power grid operator delivered a blistering rebuke Monday to the state’s Public Utilities Commission, blaming the agency for rotating power outages — the first since the 2001 energy crisis — and warning of bigger blackouts to come.

In their first public comments since the blackouts began Friday evening, officials at the California Independent System Operator described a “perfect storm” of conditions that caused demand to exceed available supply: scorching temperatures in California and across the western United States, diminished output from renewable sources and fossil-fueled power plants affected by the weather, and in some cases plants going offline unexpectedly when electricity was needed most.

But Stephen Berberich, the grid operator’s president, said the state could have been prepared for that perfect storm if only the Public Utilities Commission had ordered utility companies to line up sufficient power supplies.

During the grid operator’s board meeting Monday, Berberich faulted the commission for failing to ensure adequate power capacity on hot summer evenings, when electricity from the state’s growing fleet of rooftop solar panels and sprawling solar farms rapidly drops to zero but demand for air conditioning remains high. It’s a challenge that will only intensify as California adds more solar panels and wind turbines to meet its targets of 60% renewable electricity by 2030 and 100% emissions-free power by 2045.

“For many years, we have pointed out to the [Public Utilities Commission] that there was inadequate power available during the net peak,” Berberich said, referring to the evening period when solar production dries up but cooling demand remains high. “The situation we are in could have been avoided.”

He added, “It’s near certain that we will be forced to ask the utilities to cut off power to millions today to balance supply and demand — today, tomorrow and perhaps beyond.”

Your guide to our clean energy future

Get our Boiling Point newsletter for the latest on the power sector, water wars and more — and what they mean for California.

You may occasionally receive promotional content from the Los Angeles Times.

Asked about the grid operator’s criticism, commission spokeswoman Terrie Prosper said the agency is “working with our sister agencies to better understand why this occurred.”

“The question we’re tackling is why certain resources were not available,” she said in an email.

Blackouts were ultimately avoided Monday evening, with the grid operator crediting lower-than-expected temperatures and energy conservation by homes and businesses. But additional outages could still come later in the week.

Customers of Southern California Edison, Pacific Gas & Electric and San Diego Gas & Electric had their power briefly shut off Friday and Saturday. Several municipal electric utilities that operate their own systems have not been affected, including the Los Angeles Department of Water and Power, which has been able to share excess power with the rest of the state.

Extreme weather across California has spurred fire tornadoes, rare lightning storms, record heat and rolling blackouts.

Even before this week’s heat wave, which saw temperatures reach a record-shattering 130 degrees in Death Valley, California’s power system was in flux.

So much solar power is generated during the afternoon that California sometimes pays other states to take its excess supply. But there are fewer gas-fired power plants than in past years to pick up the slack each evening. And coal plants have been shutting down across the West because of competition from cheaper natural gas and renewables, meaning there may be less energy available for California to import in a pinch.

All of those changes are manageable, experts say. Several studies have shown that running a large power grid using mostly renewable energy is technically possible and could save money because solar and wind power have gotten so cheap.

“We’re moving forward with a low-carbon grid,” Mary Leslie, a member of the Independent System Operator’s board of governors, said during Monday’s meeting. “I think the direction is really clear, and we’re not going backward. We’re going to move forward.”

But this week’s energy emergency dramatizes the urgency of filling the evening gap.

Last year the Public Utilities Commission ordered Edison, PG&E and other utilities to buy thousands of megawatts of new power capacity. Most if not all of those resources are expected to be four-hour lithium-ion batteries that can store solar energy during the afternoon and distribute it when the sun goes down.

But none of those batteries are online yet — and the need will only grow when the massive Diablo Canyon nuclear power plant begins shutting down in 2024.

Jim Caldwell, a former assistant general manager at the Los Angeles Department of Water and Power, said the Public Utilities Commission should be acting much more aggressively to bring new supplies online. He echoed the grid operator’s call to look beyond batteries, and to build enough additional solar power to keep those batteries charged.

“Knowing what we know and where we’re going as a state, knowing that we’re going to need a lot of investments in renewables in order to meet the climate goals, what the hell’s going on?” Caldwell asked. “We know it’s cheaper, we can get the [federal] tax credits now. Ons. need the economic activity.”

Your support helps us deliver the news that matters most. Subscribe to the Los Angeles Times.

The Independent System Operator, which runs the power grid for most of the state, warned in September that California could face evening power shortages as early as summer 2020, with much larger shortfalls coming in later years as several Los Angeles-area coastal gas plants retire. One of the system operator’s top officials said at the time that the summer 2020 gap could probably be resolved by importing power from other states, “as long as it’s not hot across the West.”

But this week, it is extremely hot across the West, with Las Vegas, Los Angeles, Phoenix, Sacramento and Seattle all breaking daily temperature records Sunday, and high temperatures expected to continue for several more days.

Coupled with stay-at-home orders necessitated by the COVID-19 pandemic, the heat wave could be even deadlier than usual for people stuck at home without air conditioning — a dynamic that may be worsened by California’s rotating power outages.


Inhoud

EMDR therapy was first developed by Francine Shapiro after noticing, in 1987, [5] that eye movements appeared to decrease the negative emotion associated with her own distressing memories. [6] [7] [8] She then conducted a scientific study with trauma victims in 1988 and the research was published in the Journal of Traumatic Stress in 1989. [9] Her hypothesis was that when a traumatic or distressing experience occurs, it may overwhelm normal coping mechanisms, with the memory and associated stimuli being inadequately processed and stored in an isolated memory network. [10]

Shapiro noted that, when she was experiencing a disturbing thought, her eyes were involuntarily moving rapidly. She further noted that her anxiety was reduced when she brought her eye movements under voluntary control while thinking a traumatic thought. [11] Shapiro developed EMDR therapy for post-traumatic stress disorder (PTSD). She speculated that traumatic events "upset the excitatory/inhibitory balance in the brain, causing a pathological change in the neural elements". [11]

Shapiro over time developed an eight-stage process for EMDR, with various additions being made to the core EMDR practice itself. [12] EMDR is typically undertaken in a series of sessions with a trained therapist. [13] The number of sessions can vary depending on the progress made. A typical EMDR therapy session lasts from 60-90 minutes. [14]

Self-administration also occurs. [15] [16] [17] [18] [19]

Trauma and PTSD Edit

The person being treated is asked to recall distressing images while generating one of several types of bilateral sensory input, such as side-to-side eye movements or hand tapping. [1] [3] The 2013 World Health Organization practice guideline says that "Like cognitive behavioral therapy (CBT) with a trauma focus, EMDR aims to reduce subjective distress and strengthen adaptive beliefs related to the traumatic event. Unlike CBT with a trauma focus, EMDR does not involve (a) detailed descriptions of the event, (b) direct challenging of beliefs, (c) extended exposure, or (d) homework." [2]

Evidence of effectiveness Edit

While multiple meta-analyses have found EMDR to be as effective as trauma focused cognitive behavioral therapy for the treatment of PTSD, these findings have been regarded as tentative given the low numbers in the studies, high risk rates of researcher bias, and high dropout rates. [20] [21] [22]

  • A 2020 systematic review and meta-analysis was the "first systematic review of randomized trials examining the effects of EMDR for any mental health problem." The authors raised concerns about bias in previous studies, concluding:

Despite these limitations, the results of this meta-analysis aid us in concluding that EMDR may be effective in the treatment of PTSD in the short term and possibly have comparable effects as other treatments. However, the quality of studies is too low to draw definite conclusions. Further, it is evident that the long-term effects of EMDR are unclear and that there is certainly not enough evidence to advise its use in patients with mental health problems other than PTSD. [22]

  • A 2013 systematic review examined 15 clinical trials of EMDR with and without the eye movements, finding that the effect size was larger when eye movements were used. [23][20] Again, interpretation of this meta-analysis was tentative. Lee and Cuijpers (2013) stated that "the quality of included studies was not optimal. This may have distorted the outcomes of the studies and our meta-analysis. Apart from ensuring adequate checks on treatment quality, there were other serious methodological problems with the studies in the therapy context." [20] A meta-analysis in 2020, could not confirm the results of this 2013 study, due to "differences in inclusion criteria." [22]
  • A Cochrane systematic review comparing EMDR with other psychotherapies in the treatment of Chronic PTSD, found EMDR to be just as effective as Trauma-Focused Cognitive Behavior Therapy (TFCBT) and more effective than the other non-TFCBT psychotherapies. [21][24] Caution was urged interpreting the results due to low numbers in included studies, risk of researcher bias, high drop out rates, and overall "very low" quality of evidence for the comparisons with other psychotherapies. [21]
  • A 2010 meta-analysis concluded that all "bona fide" treatments were equally effective, but there was some debate regarding the study's selection of which treatments were "bona fide". [25]
  • A 2009 review of rape treatment outcomes concluded that EMDR had some efficacy. [26] Another 2009 review concluded EMDR to be of similar efficacy to other exposure therapies and more effective than SSRIs, problem-centered therapy, or "treatment as usual". [27]
  • Two meta-analyses in 2006 found EMDR to be at least equivalent in effect size to specific exposure therapies. [20][28]
  • A 2005 and a 2006 meta-analysis each suggested that traditional exposure therapy and EMDR have equivalent effects immediately after treatment and at follow-up. [29][28]
  • A 2002 meta-analysis concluded that EMDR is not as effective, or as long lasting, as traditional exposure therapy. [30]
  • A 1998 meta-analysis found that EMDR was as effective as exposure therapy and SSRIs. [31]

Some smaller studies have produced positive results. [32]

Position statements Edit

The 2009 International Society for Traumatic Stress Studies practice guidelines categorized EMDR as an evidence-based level A treatment for PTSD in adults. [33] Other guidelines recommending EMDR therapy – as well as CBT and exposure therapy – for treating trauma have included NICE starting in 2005, [34] [4] [35] Australian Centre for Posttraumatic Mental Health in 2007, [36] the Dutch National Steering Committee Guidelines Mental Health and Care in 2003, [37] the American Psychiatric Association in 2004, [38] the Departments of Veterans Affairs and Defense in 2010, [39] SAMHSA in 2011, [40] the International Society for Traumatic Stress Studies in 2009, [41] and the World Health Organization in 2013 (only for PTSD, not for acute stress treatment). [2] The American Psychological Association "conditionally recommends" EMDR for the treatment of PTSD. [42]

Kinders Redigeer

EMDR is included in a 2009 practice guideline for helping children who have experienced trauma. [43] EMDR is often cited as a component in the treatment of complex post-traumatic stress disorder. [44] [45]

A 2017 meta-analysis of randomized controlled trials in children and adolescents with PTSD found that EMDR was at least as efficacious as cognitive behavior therapy (CBT), and superior to waitlist or placebo. [46]

Other conditions Edit

Several small studies have indicated EMDR efficacy for other mental health conditions, [47] but more research is needed. [22]

Depression Edit

Studies have indicated EMDR effectiveness in depression. [48] [49] A 2019 review found that "Although the selected studies are few and with different methodological critical issues, the findings reported by the different authors suggest in a preliminary way that EMDR can be a useful treatment for depression." [50]

Anxiety related disorders Edit

Small studies have found EMDR to be effective with GAD, [51] OCD, [47] other anxiety disorders, [52] and distress due to body image issues. [53]

Other conditions Edit

EMDR may have application for psychosis when co-morbid with trauma, [47] Other studies have investigated EMDR therapy’s efficacy with borderline personality disorder, [54] and somatic disorders such as phantom limb pain. [55] [56] EMDR has also been found to improve stress management symptoms. [57] EMDR has been found to reduce suicide ideation, [58] and help low self-esteem. [59] Other studies focus on effectiveness in substance craving [60] and pain management. [61] EMDR may help people with autism who suffer from exposure to distressing events. [62]

Resensies wysig

  • A 2020 review found EMDR "is a safe and economical therapeutic option." [63]
  • A 2020 systematic review and meta-analysis was the "first systematic review of randomized trials examining the effects of EMDR for any mental health problem." The authors concluded: "it is evident that the long-term effects of EMDR are unclear, and. there is certainly not enough evidence to advise its use in patients with mental health problems other than PTSD." [22]
  • A 2013 overall literature review covered research up to that time. [64]

Possible mechanisms Edit

Incomplete processing of experiences in trauma Edit

Many proposals of EMDR efficacy share an assumption that, as Shapiro posited, when a traumatic or very negative event occurs, information processing of the experience in memory may be incomplete. The trauma causes a disruption of normal adaptive information processing, which results in unprocessed information being dysfunctionally held in memory networks. [65] According to the 2013 World Health Organization practice guideline: "This therapy [EMDR] is based on the idea that negative thoughts, feelings and behaviours are the result of unprocessed memories." [2]

EMDR allowing correct processing of memories Edit

EMDR is posited to help in the correct processing of the components of the contributing distressing memories. [66] [67] EMDR may allow the client to access and reprocess negative memories (leading to decreased psychological arousal associated with the memory). [68] This is sometimes known as the Adaptive Information Processing (AIP) model. [69] [70] [ unreliable medical source ]

EMDR has been found to lead to reduced connectivity between some brain areas. [71]

Proposed mechanisms by which EMDR achieves efficacy Edit

The mechanism by which EMDR achieves efficacy is unknown, with no definitive finding. Several possible mechanisms have been posited

  • EMDR impacts working memory. [72] By having the patient perform a bilateral stimulation task while retrieving memories of trauma, the amount of information they can retrieve about the trauma is limited, and thus the resulting negative emotions are less intense. [73] This is seen by some as causing a distancing effect which enables the client to 'stand back' from the trauma. The client is enabled to re-evaluate the trauma and their understanding of it, and thus process it correctly, because they can re-experience it whilst not feeling overwhelmed by it. [47]
  • EMDR enables ‘dual attention’ (recalling the trauma whilst keeping ‘one foot in the present’ assisted by BLS). This allows the brain to access the dysfunctionally stored experience and stimulate the innate processing system, allowing it to transform the information to an adaptive resolution. [47]
  • Connectivity among several brain regions has been found to be changed by bilateral eye movement and by EMDR. These changes may cause EMDRs efficacy. [74][75]
  • EMDR efficacy has been linked to the Zeigarnik effect (i.e. better memory for interrupted rather than completed tasks). [76]
  • Horizontal eye movement triggers an evolutionary 'orienting response' in the brain, used in scanning the environment for threats and opportunities. [77]
  • EMDR gives an effect similar to the effects of sleep, [78] and posit that traumatic experiences are processed during sleep.
  • Trauma can be overcome or mastered, and EMDR facilitates a form of mindfulness or other form of mastery over the trauma. [47]

A 2013 meta-analysis focused on two mechanisms: (1) taxing working memory and (2) orienting response/REM sleep. [20]

It may be that several mechanisms are at work in EMDR. [47]

Bilateral stimulation, including eye movement Edit

Bilateral stimulation is a generalization of the left and right repetitive eye movement technique first used by Shapiro. Alternative stimuli include auditory stimuli that alternate between left and right speakers or headphones, and physical stimuli such as tapping of the therapist's hands. [79] Research has attempted to correlate other types of rhythmic side-to-side stimuli, such as sound and touch, with mood, memory and cerebral hemispheric interaction.

Research results and opinions have been mixed on the effectiveness and importance of the technique

  • 2020 research showed that bilateral alternating stimulation caused a significant increase in connectivity between several areas of the brain, including the two superior temporal gyri, the precuneus, the middle frontal gyrus and a set of structures involved in multisensory integration, executive control, emotional processing, salience and memory. large emotional neural networks. [80]
  • A 2020 review questioned the consistency and generalizability of the technique. [81]
  • A 2013 meta-study found the effect size of eye movement was large and significant, with the strongest effect size difference being for vividness measures. [20][47]
  • A 2012 review found that the evidence provided support for the contention that eye movements are essential to this therapy and that a theoretical rationale exists for their use. [77]
  • A 2002 review reported that the eye movement is irrelevant, and that the effectiveness of EMDR was solely due to its having properties similar to CBT, such as desensitization and exposure. [82]
  • A 2001 meta-analysis suggested that EMDR with the eye movements was no more efficacious than EMDR without the eye movements (Davidson & Parker, 2001). [23][83][84]
  • A 2000 review found that the eye movements did not play a central role, and that the mechanisms of eye movements were speculative. [85]
  • A small 1996 study found that the eye movements employed in EMDR did not add to its effectiveness. [86]

Francine Shapiro noticed that eye movements appeared to decrease the negative emotion associated with her own distressing memories. [87] [88] [89] Bilateral stimulation seems to cause dissipation of emotions. [90] [91]

EMDR has historically been controversial within the psychological community. [92] [93]

Effectiveness and theoretical basis Edit

Concerns have included questions about its effectiveness and the importance of the eye movement component of EMDR. In 2012, Hal Arkowitz, and Scott Lilienfeld summed up the state of the research at the time, saying that while EMDR is better than no treatment and probably better than merely talking to a supportive listener,

Yet not a shred of good evidence exists that EMDR is superior to exposure-based treatments that behavior and cognitive-behavior therapists have been administering routinely for decades. Paraphrasing British writer and critic Samuel Johnson, Harvard University psychologist Richard McNally nicely summed up the case for EMDR: "What is effective in EMDR is not new, and what is new is not effective." [94]

Client perceptions of effectiveness are also mixed. [95]

Pseudoscience Edit

Past skeptics of the therapy argued that EMDR is a pseudoscience, because the underlying theory is unfalsifiable. Also, the results of the therapy are non-specific, especially if the eye movement component is irrelevant to the results. What remains is a broadly therapeutic interaction and deceptive marketing. [85] [30] According to Yale neurologist Steven Novella:

[T]he false specificity of these treatments is a massive clinical distraction. Time and effort are wasted clinically in studying, perfecting, and using these methods, rather than focusing on the components of the interaction that actually work. [96]

Excessive training Edit

Shapiro has been criticized for repeatedly increasing the length and expense of training and certification, allegedly in response to the results of controlled trials that cast doubt on EMDR's efficacy. [97] [85] This included requiring the completion of an EMDR training program in order to be qualified to administer EMDR properly, after researchers using the initial written instructions found no difference between no-eye-movement control groups and EMDR-as-written experimental groups. Further changes in training requirements and/or the definition of EMDR included requiring level II training when researchers with level I training still found no difference between eye-movement experimental groups and no-eye-movement controls and deeming "alternate forms of bilateral stimulation" (such as finger-tapping) as variants of EMDR by the time a study found no difference between EMDR and a finger-tapping control group. [97] Such changes in definition and training for EMDR have been described as "ad hoc moves [made] when confronted by embarrassing data". [98]


Kyk die video: Fergal Scahills fiddle tune a day 2017 - Day 68 - The Rolling Wave