检索结果-南通市图书馆

Numerical Analysis of Nozzle Clearance's Effect on Turbine Performance

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2011年第4期24卷 618-625页

作者： HU liangjun yang Ce SUN harold ZHANG Jizhong lAI Mingchia School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China FordMotor Company Michigan 48124 USA National Key laboratory of Diesel Engine Turbocharging Technology Datong 037036 China Wayne State University Michigan 48122 USA

Variable nozzle turbine （VNT） has become a popular variable geometry turbine （VGT） technology for the diesel engine application. Nozzle clearance, which can＇t be avoided on the hub and shroud side of the VNT turbine due to the pivoting stators, can lead to turbine performance deterioration. However, its mechanism is still not clear. In this paper, numerical investigation, which is validated by experiment, is carried out to study the mechanism of the nozzle clearance＇s effect on the turbine performance. Firstly, performance of the mixed flow turbine with fixed nozzle clearances tested on flow bench. Performance of the tested turbine with the same nozzle clearance is numerically simulated. The numerical result agrees well with the test data, which proves correct of the numerical method. Then the turbine performance with different nozzle clearances is numerically analyzed. The research showed that with nozzle clearance, flow loss in the nozzle increases at first and it reaches the maximum value when the clearance ratio is 5%. Flow at the exit of the nozzle becomes less uniform with nozzle clearance. The negative incidence angle of the rotor also increases with nozzle clearance and leads to more incidence angle loss in the rotor. The low energy fluid formed in the nozzle due to the nozzle clearance migrates from hub to shroud side in the rotor, which is another main reason for the rotor＇s performance degradation. The present research exposed the mechanism of the dramatically decrease of the turbine performance with nozzle clearance：（a） The loss associated with the nozzle leakage increases with the nozzle clearance; （b） The flow loss grows up quickly in the rotor due to the incidence angle loss and migration of the low energy fluid from hub to shroud side.

关键词： nozzle clearance variable nozzle turbine (VNT) mixed flow turbine

Treatment of hyperkalemic emergencies

在线全文

学校读者我要写书评

暂无评论

World Journal of Emergency Medicine 2022年第3期13卷 232-236页

作者： Yao Wu yang-yang Fu Hua-dong Zhu Jun Xu Joseph harold Walline Emergency Department State Key Laboratory of Complex Severe and Rare DiseasesPeking Union Medical College HospitalChinese Academy of Medical Science and Peking Union Medical CollegeBeijing 100730China Centre for the Humanities and Medicine the University of Hong KongHong KongChina

Hyperkalemic emergency(HE)refers to life-threatening hyperkalemia consisting of a high serum potassium level with severe complications(e.g.,dysrhythmias,cardiac arrest,or myopathy).^([1])Hyperkalemic emergencies(HEs)a... 详细信息

关键词： cardiac potassium arrest

role of seed size, phenology, oogenesis and host distribution in the specificity and genetic structure of seed weevils (Curculio spp.) in mixed forests

在线全文

学校读者我要写书评

暂无评论

Integrative Zoology 2018年第3期13卷 267-279页

作者： harold ArIAS-lEClAIrE raúl BONAl Daniel GArCÍA-lÓPEZ Josep Maria ESPElTA CrEAF Centre for Ecological Research and Forestry ApplicationsCerdanyola del Vallès08193Spain Exact and Natural Sciences School State Distance University of Costa RicaUNEDMercedes de Montes de OcaSan JoséCosta Rica Forest research Group INDEHESAUniversity of ExtremaduraPlasenciaSpain DITEG research Group University of Castilla-La ManchaToledoSpain Zoology Department Autonomous University of BarcelonaCerdanyola del VallèsSpain

Synchrony between seed growth and oogenesis is suggested to largely shape trophic breadth of seed-feeding insects and ultimately to contribute to their co-existence by means of resource partitioning or in the time when infestation *** we investigated:(i)the role of seed phenology and sexual maturation of females in the host specificity of seed-feeding weevils(Curculio spp.)predating in hazel and oak mixed forests;and(ii)the consequences that trophic breadth and host distribution have in the genetic structure of the weevil *** analyses were used to establish unequivocally host specificity and to determine the population genetic *** identified 4 species with different specificity,namely Curculio nucum females matured earlier and infested a unique host(hazelnuts,Corylus avellana)while 3 species(Curculio venosus,Curculio glandium and Curculio elephas)predated upon the acorns of the 2 oaks(Quercus ilex and Quercus pubescens).The high specificity of *** coupled with a more discontinuous distribution of hazel trees resulted in a significant genetic structure among *** addition,the presence of an excess of local rare haplotypes indicated that *** populations went through genetic expansion after recent ***,these effects were not observed in the more generalist Curculio glandium predating upon ***,co-existence of weevil species in this multi-host-parasite system is influenced by both resource and time *** what extent the restriction in gene flow among *** populations may have negative consequences for their persistence in a time of increasing disturbances(*** in Mediterranean areas)deserves further research.

关键词： Corylus avellana Curculio spp. genetic structure Quercus spp. trophic breadth

revision of failed transoral incisionless fundoplication by subsequent laparoscopic Nissen fundoplication

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2014年第45期20卷 17115-17119页

作者： Awais Ashfaq Hyun K (Daniel) rhee Kristi l harold Department of Surgery Mayo Clinic Phoenix AZ 85054 United States

AIM: To evaluate the feasibility and outcomes of laparoscopic Nissen fundoplication after failed transoral incisionless fundoplication (TIF).

关键词： Transoral incisionless fundoplication laparascopic Nissen fundoplication laparoscopy Gastroesophageal reflux disease Surgical complications

First‐mode of negative streamers:Inception at liquid/solid interfaces

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

High Voltage 2021年第6期6卷 1069-1078页

作者： David Ariza Abderrahmane Beroual ralf Methling Sergey Gortschakow harold r.Chamorro School of Electrical Engineering KTH Royal Institute of TechnologyStockholmSweden Ecole Centrale de‐lyon Ampère CNRS UMR 5005EcullyFrance leibniz Institute for Plasma Science and Technology INP GreifswaldGermany

An experimental study of the inception of the first‐mode negative streamer at liquid/solid interfaces is presented in this *** study is performed with a point‐plane configuration under square high voltage *** electrode configuration is immersed in mineral oil and the liquid/solid interface is assembled in contact with the point electrode or in its *** polymers and two impregnated papers have been tested as solids of the liquid/solid ***,it is possible to compare the influence of different parameter of the solid and the interface on the streamer *** example:Permittivity,solid surface roughness,chemical composition,*** has been observed that streamer inception voltages at interfaces with solids of higher permittivity to that of the mineral oil are statistically ***,streamer inception voltages of streamer initiated free in the oil(no liquid/solid interface)are similar to that of the inception voltage of cases with solids with high *** contrast,the inception voltage of streamers initiated at permittivity matched interfaces are shown to be highest of the *** streamer inception voltage is also studied for different distances be-tween the liquid/solid interface and the point electrode with a permittivity matched *** results show a dependency of the inception voltage and the distance be-tween the point electrode and the ***,an analysis of the observation is performed to show that the Townsend‐Meek criterion cannot predict the obtained results.

关键词： solid liquid electrode

Pancreatic ductal adenocarcinoma: risk factors, screening, and early detection

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2014年第32期20卷 11182-11198页

作者： Andrew E Becker Yasmin G Hernandez harold Frucht Aimee l lucas Henry D. Janowitz Division of Gastroenterology Icahn School of Medicine at Mount Sinai New York NY 10029 United States Division of Digestive and liver Diseases Columbia University College New York NY 10032 United States

Pancreatic cancer is the fourth most common cause of cancer-related deaths in the United States, with over 38000 deaths in 2013. The opportunity to detect pancreatic cancer while it is still curable is dependent on our ability to identify and screen high-risk populations before their symptoms arise. risk factors for developing pancreatic cancer include multiple genetic syndromes as well as modifiable risk factors. Genetic conditions include hereditary breast and ovarian cancer syndrome, lynch Syndrome, familial adenomatous polyposis, Peutz-Jeghers Syndrome, familial atypical multiple mole melanoma syndrome, hereditary pancreatitis, cystic fibrosis, and ataxia-telangiectasia; having a genetic predisposition can raise the risk of developing pancreatic cancer up to 132-fold over the general population. Modifiable risk factors, which include tobacco exposure, alcohol use, chronic pancreatitis, diet, obesity, diabetes mellitus, as well as certain abdominal surgeries and infections, have also been shown to increase the risk of pancreatic cancer development. Several largevolume centers have initiated such screening protocols, and consensus-based guidelines for screening high-riskgroups have recently been published. The focus of this review will be both the genetic and modifiable risk factors implicated in pancreatic cancer, as well as a review of screening strategies and their diagnostic yields.

关键词： Pancreatic neoplasms Pancreas cancer screening Genetic predisposition to disease Hereditary breast and ovarian cancer syndrome lynch syndrome Peutz-Jeghers BrCA PAlB2 p16 Pancreatitis

Human impact on fish sensory systems in the long term: An evolutionary perspective

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Integrative Zoology 2015年第1期10卷 83-90页

作者： harold H.ZAKON Sections of Neurobiology and Integrative Biology The University of TexasAustinTXUSA

Humans have severely impacted global ecosystems and this shows few signs of *** aspects of an animal’s biology,including its sensory systems,may be adversely influenced by pollutants and environmental *** review focuses on whether and/or how various environmental disturbances disrupt the sensory systems of *** critical as it is to document and understand the current effects of the human footprint,it is also important to consider how organisms might adapt to these impacts over the long *** present paper outlines the sources of genetic and genomic variation upon which natural selection can act and then reviews examples of known genetic contributions of variation in fish chemosensory,visual and acoustico-lateralis systems.

关键词： evolution fish genes sensory receptor

Tuning the electrons at the laAlO_3/SrTiO_3 interface: From growth to beyond growth

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2013年第12期22卷 1-9页

作者：谢燕武 Hwang harold Y Geballe laboratory for Advanced Materials Department of Applied Physics Stanford University Stanford Institute for Materials and Energy Sciences SLAC National Accelerator Laboratory

recently, the quasi-two-dimensional electron gas （q2DEG） confined at the interface between laAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been used to tune the carrier density and mobility of this q2DEG. These methods can be classified into two categories： growth-related tuning （i.e. substrate, growth temperature, oxygen pressure, post-annealing, laAlO3 thickness, stoichiometry, and capping layers） and post-growth tuning （i.e. electrostatic field gating, conductive atomic force microscopy and surface adsorbates）. Taken together, these methods enable the broad tuning of the electronic properties of this interface.

关键词： laAlO3/SrTiO3 strontium titanate oxides two-dimensional electron gas interface

Global climate change is confounding species conservation strategies

在线全文

学校读者我要写书评

暂无评论

Integrative Zoology 2012年第2期7卷 158-164页

作者： harold KOOPOWITZ Bradford A.HAWKINS Department of Ecology and Evolutionary Biology University of CaliforniaIrvineCaliforniaUSA

Most organisms face similar problems with respect to their conservation in the face of global climate ***,we examine probable effects of climate change on the hyperdiverse plant family *** the 20th century,the major concerns for orchid conservation revolved around unsustainable harvest for the orchid trade and,more importantly,land conversion from natural ecosystems to those unable to support wild orchid pop*** conversion included logging,fire regimes and forest conversions to agricultural ***though those forms of degradation continue,an additional suite of threats has emerged,fueled by global climate *** climate change involves more than responses of orchid populations to increases in ambient *** temperature induces secondary effects that can be more significant than simple changes in *** these new threats are extended and prolonged fire seasons,rising sea levels,increases in cyclonic storms,seasonal climate shifts,changes in orthographic wind dew point and increased *** long-term outlook for orchid biodiversity in the wild is dismal,as it is for many animal groups,and we need to start rethinking strategies for conservation in a rapidly changing world.

关键词： biodiversity climate change conservation biology ex situ conservation orchids