The efficiency of direct integration methods in elastic contact-impact problems

A comparison of direct integration methods is madeand their efficiency is investigated for impact problems.New-mark,Wilson-θ,Central Difference and Houbolt Methodsare used as direct integration methods.Impact analysisincludes that of elastic and large deformation based uponupdated Lagrangian including buckling check.The resultsshow that the direct integration methods give differentresults in different contact-impact cases.

The Impact of Directly Observed Therapy on Preventive Treatment for Latent Tuberculosis Infection among Students in Dalian, China

Preventive treatment has an essential effect on latent tuberculosis infection(LTBI)[purified protein derivative(PPD)induration≥15 mm].Between2010 and 2013,there were 6 tuberculosis(TB)outbreaks in the universities in Dalian,China.So far,in Dalian,the directly observed therapy(DOT)and

Strain-rate effect on initial crush stress of irregular honeycomb under dynamic loading and its deformation mechanism

The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored.The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.

Direct impacts and spatial spillovers:How does the multilateral resistance affect China-Africa agricultural trade?

The changes of one region’s trade barriers will affect other regions’trade volume.These spatial correlations caused by explanatory variables also constitute another part of“the multilateral resistance”,which tend to be ignored in traditional gravity equations.This paper takes this inconsistency between theoretical basis and empirical analysis as the breakthrough point of research.A multilateral gravity model is built,which has the feature of generalized spatial correlation.Then,frontier techniques of spatial econometrics are used to construct an empirical equation,and to conduct an empirical analysis,which scientifically estimate the magnitudes of bilateral direct impacts and the magnitudes of spatial spillovers on multilateral neighbors.The decomposition of the effects that provides reference for the directional operations of trade policy shows as follows:The negative factors that have significant spatial spillover effects would bring about multilateral resistance on China-Africa agricultural trade,which are caused by relatively poor social and economic conditions,corruption,and ethnic conflicts in some African countries.Energy production may cause crowding-out effects on agriculture of neighboring regions.In addition,the conflicts between African countries would hinder the development of agricultural trade between China and African countries not only because they have negative direct impacts on China-African agricultural trade but also because they have significant spatial spillover effects.When China promotes China-Africa agricultural trade by means of investment or aid,China should pay close attention to some direct or indirect impacts on the stable development of the China-African agricultural trade,which are caused by factors such as the developments of non-agricultural industries,peace,cultural consensus and efficient government.

The Impact of Foreign Direct Investment on Chinese Auto Industry

3.5 Foreign investors madding about assembling cars while localization of cars neglected. What the most foreign partners are mad about in China is to assemble cars with CKD parts to seek money. Few of them care about the localization, especially when their Chinese partners are not strong enough. 3.6 Controlling on Development of Product Although the Chinese sides are holding the stock shares in most joint ventures, the foreign partners often hold back the development of new products by means of intellectual property rights. When developing new products, the foreign investors are likely to transfer the

人类活动和气候变化对多维度水文情势影响的量化研究--以中国岷江上游为例

Dual factors of climate and human on the hydrological process are reflected not only in changes in the spatiotemporal distribution of water resource amounts but also in the various characteristics of river flow regimes. Isolating and quantifying their contributions to these hydrological alterations helps us to comprehensively understand the response mechanism and patterns of hydrological process to the two kinds of factors. Here we develop a general framework using hydrological model and 33 indicators to describe hydrological process and quantify the impact from climate and human. And we select the Upper Minjiang River(UMR) as a case to explore its feasibility. The results indicate that our approach successfully recognizes the characteristics of river flow regimes in different scenarios and quantitatively separates the climate and human contributions to multi-dimensional hydrological alterations. Among these indicators, 26 of 33 indicators decrease over the past half-century(1961–2012) in the UMR, with change rates ranging from 1.3% to 33.2%, and the human impacts are the dominant factor affecting hydrological processes, with an average relative contribution rate of 58.6%. Climate change causes an increase in most indicators, with an average relative contribution rate of 41.4%. Specifically, changes in precipitation and reservoir operation may play a considerable role in inducing these alterations. The findings in this study help us better understand the response mechanism of hydrological process under changing environment and is conducive to climate change adaptation, water resource planning and ecological construction.