检索结果-南通市图书馆

Earthquake Engineering and Engineering Vibration 2018年第1期17卷 125-138页

作者： Wang Gang Wei Xing john Zhao Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing University School of Civil Engineering Chongqing University School of Civil Engineering Southwest Jiaotong University

The acceleration records at some liquefied sand deposits exhibit a distinctive spiky waveform, characterized by strong amplification and high-frequency components. A comprehensive constitutive model was used to analyze the mechanism of such spiky acceleration responses. An idealized single-degree-of-freedom（SDF） system was constructed, in which the force-displacement relation of the spring follows the stress-strain behavior of saturated sand during undrained shearing. The SDF system demonstrated that the spikes are directly related to the strain-hardening behavior of sand during post-liquefaction cyclic shearing. Furthermore, there exists a threshold shear strain length, which is in accordance with the limited amplitude of the fluid-like shear strain generated at instantaneous zero effective stress state during the post-liquefaction stage. The spiky acceleration can only occur when the cyclic shear strain exceeds the threshold shear strain length. It is also revealed that the time intervals between the acceleration spikes increase gradually along with the continuation of shaking because the threshold shear strain length increases gradually and then more time is needed to generate larger shear strain to cause strain hardening. Records at the Kushiro Port site and Port Island site during past earthquakes are simulated through the fully coupled method to validate the presented mechanism.

关键词： spiky acceleration cyclic mobility post-liquefaction seismic response sand

Mechanisms, prevention and clinical implications of nonsteroidal anti-inflammatory drug-enteropathy

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2013年第12期19卷 1861-1876页

作者： john L Wallace Farncombe Family Digestive Health Research Institute McMaster University Inflammation Research Network University of Calgary

This article reviews the latest developments in understanding the pathogenesis, detection and treatment of small intestinal damage and bleeding caused by nonsteroidal anti-inflammatory drugs (NSAIDs). With improvements in the detection of NSAID-induced damage in the small intestine, it is now clear that this injury and the associated bleeding occurs more frequently than that occurring in the stomach and duodenum, and can also be regarded as more dangerous. However, there are no proven-effective therapies for NSAID-enteropathy, and detection remains a challenge, particularly because of the poor correlation between tissue injury and symptoms. Moreover, recent studies suggest that commonly used drugs for protecting the upper gastrointestinal tract (i.e., proton pump inhibitors) can significantly worsen NSAID-induced damage in the small intestine. The pathogenesis of NSAID-enteropathy is complex, but studies in animal models are shedding light on the key factors that contribute to ulceration and bleeding, and are providing clues to the development of effective therapies and prevention strategies. Novel NSAIDs that do not cause small intestinal damage in animal models offer hope for a solution to this serious adverse effect of one of the most widely used classes of drugs.

关键词： Anti-inflammatory Ulcer Prostaglandin Non-steroidal Bleeding Intestinal Bile Enterohepatic Bacteria Hydrogen sulfide Aspirin Hemorrhage

Proto-South China Sea Plate Tectonics Using Subducted Slab Constraints from Tomography

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Earth Science 2018年第6期29卷 1304-1318页

作者： Jonny Wu john Suppe Department of Earth and Atmospheric Sciences University of Houston

The past size and location of the hypothesized proto-South China Sea vanished ocean basin has important plate-tectonic implications for Southeast Asia since the Mesozoic. Here we present new details on proto-South China Sea paleogeography using mapped and unfolded slabs from tomography. Mapped slabs included： the Eurasia-South China Sea slab subducting at the Manila trench; the northern Philippine Sea Plate slab subducting at the Ryukyu trench; and, a swath of detached, subhorizontal, slab-like tomographic anomalies directly under the South China Sea at 450 to 700 km depths that we show is subducted ‘northern proto-South China Sea’ lithosphere. Slab unfolding revealed that the South China Sea lay directly above the ‘northern Proto-South China Sea’ with both extending 400 to 500 km to the east of the present Manila trench prior to subduction. Our slab-based plate reconstruction indicated the proto-South China Sea was consumed by double-sided subduction, as follows：（1） The ‘northern proto-South China Sea’ subducted in the Oligo–Miocene under the Dangerous Grounds and southward expanding South China Sea by in-place ‘self subduction’ similar to the western Mediterranean basins;（2） limited southward subduction of the proto-South China Sea under Borneo occurred pre-Oligocene, represented by the 800–900 km deep ‘southern proto-South China Sea’ slab.

关键词： seismic tomography plate tectonics South China Sea proto-South China Sea subducted slabs Borneo Oligocene–Miocene

Simulation of Fragment Impact on Multi-Layer Targets Using Contact Method

在线全文

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2006年第B09期12卷 152-157页

作者： CRAWFORD john E Karagozian & Case 2550 N.Hollywood WaySuite 500BurbankCA 91505USA

Cased explosives generate highly energetic fragments as their casing breaks up. Due to the complexity of casing fragment related behavior such as embedment, perforation and ricochet, it may be insufficient to use equivalent triangular pressure loading in fragment impact simulations. This simplified method may over- or under-predict the target response. Recently, a procedure using contact techniques has been proposed to overcome such difficulties. It has been shown that the new method has the inherent capability in modeling the multi-piece and multi-hit fragment impact problems in a more realistic way. To investigate the applicability of the proposed method to simulations involving multi-layer penetration, the selected problems of fragment impact on multi-layer targets are described in this paper. It is demonstrated that this method is capable of predicting the complicated multi-layer structural response caused by fragment impact and penetration. Modeling procedures and some technical issues are also discussed.

关键词： contact finite element fragment impact multi-layer penetration simulation

Effects of the plenum chamber volume and distributor geometry on fluidized bed hydrodynamics

在线全文

学校读者我要写书评

暂无评论

Particuology 2010年第1期8卷 2-12页

作者： Kiarash Vakhshouri john R. Grace Department of Chemical and Biological Engineering University of British Columbia

Most hydrodynamic fluidized bed models, including CFD codes, neglect any effects of the plenum chamber volume. Experiments were performed in a 0.13 m ID fluidization column to determine plenum chamber volume effects on fluidized bed hydrodynamics for FCC and glass particles. Two low-pressure-drop distributors were used, one with a single orifice, and the other with 33 orifices and the same total open area as the single orifice. The results show two peaks in the frequency spectra for the single-orifice distributor, one representing bubble eruption at the bed surface and the other of higher frequency corresponding to the bubbling frequency at the distributor. The latter decreased slightly with increasing plenum volume and with increasing bed depth. For the multi-orifice distributor, broad frequency spectra from pressure measurements became narrower and moved towards higher frequency with decreasing plenum volume.

关键词： Fluidization Bubble Distributor Plenum chamber Hydrodynamics Pressure drop

The Ethico-Political Universe of ChatGPT

在线全文

学校读者我要写书评

暂无评论

Journal of Social Computing 2023年第1期4卷 1-11页

作者： john Levi Martin john Levi Martin is with the Sociology Department University of ChicagoChicagoIL 60637USA

There have been widespread concerns about two aspects of the current explosion of predictive text models and other algorithm-based computational *** one hand,it is often insisted that Artificial Intelligence(AI)should be made“ethical”,and software providers take this seriously,attempting to make sure that their tools are not used to facilitate grossly criminal or widely condemned *** the other hand,it is also widely understood that those who create these tools have a responsibility to ensure that they are“unbiased”,as opposed to simply helping one side in political contestation define their perspectives as reality for ***,these two goals cannot be jointly satisfied,as there are perhaps no ethical prescriptions worthy of notice that are not contested by *** I investigate the current ethico-political sensibility of ChatGPT,demonstrating that the very attempt to give it an ethical keel has also given it a measurably left position in the political space and a concomitant position in social space among the privileged.

关键词： algorithmic bias values machine ethics human-machine interaction

Radiative life time of an exciton confined in a strained GaN/Ga_(1-x)Al_xN cylindrical dot:built-in electric field effects

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 2011年第7期20卷 367-372页

作者： Chang Woo Lee A.john Peter Department of Chemical Engineering and Green Energy Center College of EngineeringKyung Hee University1 SeochunGihungYonginGyeonggi 446-701Republic of Korea Department of Physics Government Arts and Science CollegeMelur-625106India

The binding energy of an exciton in a wurtzite GaN/GaAlN strained cylindrical quantum dot is investigated theoretically. The strong built-in electric field due to the spontaneous and piezoelectric polarizations of a GaN/GaAlN quantum dot is included. Numerical calculations are performed using a variational procedure within the single band effective mass approximation. Valence-band anisotropy is included in our theoretical model by using different hole masses in different spatial directions. The exciton oscillator strength and the exciton lifetime for radiative recombination each as a function of dot radius have been computed. The result elucidates that the strong built-in electric field influences the oscillator strength and the recombination life time of the exciton. It is observed that the ground state exciton binding energy and the interband emission energy increase when the cylindrical quantum dot height or radius is decreased, and that the exciton binding energy, the oscillator strength and the radiative lifetime each as a function of structural parameters （height and radius） sensitively depend on the strong built-in electric field. The obtained results are useful for the design of some opto-photoelectronic devices.

关键词： quantum dot donor bound excitons oscillator strength

Sub-regional dimensions of agricultural and environmental nitrogen:The case of Asia

在线全文

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2005年第z2期48卷 738-744页

作者： john Keith Syers School of Science Mae Fah Luang University Chiang Rai 57100Thailand

Asia embraces a wide range of cropping environments, largely related to the diversity of climate. To meet the high food requirements of a very large population (some 59% of the earth's total) large inputs of mineral N fertilizer are required (44.2 Tg ***-1 in the mid 1990s).However, because of the low (20%-50%) overall efficiency of use of fertilizer N, sometimes coupled with heavy use in intensively-farmed areas (for example in parts of China), losses of fertilizer N from agricultural land are expected to be high. Part of the N lost is thought to cause pollution of the atmosphere and water resources.A sub-regional approach, based on the FAO Agroecological Zone (AEZ) concept, has the potential to provide meaningful assessments of the agricultural and environmental dimensions of *** AEZ concept can also provide the rationale for locating Sub-regional Centers of the International Nitrogen Initiative (INI) by basing the considerations, as far as practicable, on agroecological conditions.

关键词： fertilizer nitrogen, loss processes, use efficiency, atmospheric and water pollution, agroecological zones.

Host RNA circles and the origin of hepatitis delta virus

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2014年第11期20卷 2971-2978页

作者： john M Taylor Fox Chase Cancer Center PhiladelphiaPA 19111United States

Recent reports show that many cellular RNAs are processed to form circular species that are relatively abundant and resistant to host *** some cases,such circles actually bind host *** depletion of available microRNAs appears to have biological roles;for instance,in homeostasis and *** findings regarding host RNA circles support a speculative reappraisal of the origin and mode of replication of hepatitis delta virus,hepatitis delta virus(HDV),an agent with a small circular RNA genome;specifically,it is proposed that in hepatocytes infected with hepatitis B virus(HBV),some viral RNA species are processed to circular forms,which by a series of chance events lead to an RNA that can be both replicated by host enzymes and assembled,using HBV envelope proteins,to form particles some of which are *** a model also may provide some new insights into the potential pathogenic potential of HDV *** return,new insights into HDV might provide information leading to a better understanding of the roles of the host RNA circles.

关键词： Hepatitis B virus Hepatitis delta virus Circular RNA Ribozymes MicroRNA

Evaluation of WEPP versus EGEM and empirical model efficiencies in predicting ephemeral gully erosion around Mubi area,Northeast Nigeria

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Soil and Water Conservation Research 2021年第1期9卷 11-25页

作者： Ijasini john Tekwa john Mathew Laflen Abubakar Musa Kundiri Abdullahi Bala Alhassan Department of Soil Science&Land Resources Management Federal University WukariP.M.B1020Wukari Taraba StateNigeria USDA-ARS National Soil Erosion Research LaboratoryPurdue UniversityLafayetteINUSA Department of Soil Science Faculty of AgricultureUniversity of MaiduguriP.M.B1069Borno StateNigeria

Evaluation of prediction models is crucial to achieving valid information on erosion processes and their management *** model efficiency in predicting ephemeral gully(EG)erosion was recently tested and compared with both EGEM and empirical *** models abilities to predict EG erosion were validated using measured estimates at the 6 eroding locations around Mubi area in Northeast Nigeria between April 2008 and October *** location consisted of 3 watersheds where data on soils,climate,slope,management practices,EG shapes and dimensions were *** on relevant soil properties were collected in the field and then analyzed in *** mass of soil loss(MSL)predicted by empirical,EGEM and WEPP models were compared with the measured using paired T-test,regression graphs(r^(2)-values),error analysis,and analysis of variance(ANOVA)in a completely ran-domized *** EG erosion losses varied significantly(P≤0.05)between sites and *** sig-nificant(P≤0.05)differences were observed between measured and the empirically predicted aggregate *** measured aggregate MSL strongly correlated with those predicted by empirical(r^(2)=0.67),than with EGEM(r^(2)=0.57),and WEPP(r^(2)=0.53)*** over and under-prediction instances against the measured erosion were noted with all the *** WEPP model was found to slightly over-predict MSL when compared to either the empirical or EGEM *** prediction quality of the models was generally *** works should focus more on local inputs such as climate,plants,management,and tillage data for use with WEPP.

关键词： Empirical EGEM WEPP Ephemeral gully erosion Soil loss Mubi Northeast Nigeria