Variation in the effect of system usage and individual impact: A meta-regression of empirical findings

The relationship between system usage and individual impact has received considerable attention in prior studies. However, the results for the relationship have been mixed. This study hypothesizes that the variation in the effect of system usage on individual impact may be attributed to characteristics of the research contexts. This research examines the effects of voluntariness of use, number of organizations, number of respondents, type of respondents, and information system type, while controlling for geographic region and industry sector using meta-regression methods to examine the findings from 74 studies published between 1992 and 2018. Implications for research and practice are discussed.     

Comparative analysis of energy absorption behavior of tapered and grooved thin-walled tubes with the various geometry of the cross section

ABSTRACT

In this paper, Crush force efficiency (CFE), Specific Energy Absorption (SEA), Energy Absorption per Crush Length (E_cl), Maximum and average crush forces of straight and grooved tapered thin-walled tubes with various cross-section shapes (circle, ellipse, square, rectangle, hexagon, and octagon) have been studied. The effects of taper, the groove (as initiator) and their interaction have been presented in the current study using Finite Element Method as a numerical method. The tubes have the same volume, height, average cross-section area, thickness and material and have been subjected to axial and oblique dynamic loading. The results of simulations show that the section's geometry, taper and groove addition have a significant effect on energy absorption behavior and the hexagon cross section have better energy absorption behavior compared with other considered geometries. On the other hand, it was found that the behavior of these structures could improve against dynamic axial and oblique impact loading with the cost-effective geometry modifications. These results could help to improve and choose appropriate energy absorber structure based on desirable crush force and energy absorbing characteristics.     

飞机撞击下高温气冷堆乏燃料厂房损伤研究

本文针对典型高温气冷堆乏燃料厂房在双发商用飞机撞击载荷下的响应及结构完整性开展研究，并探讨结构特性对撞击损伤的影响。对乏燃料厂房及飞机分别建立有限元模型，通过弹体-目标相互作用分析模拟了飞机撞击过程，综合IAEA与NRC的评价准则对乏燃料厂房在飞机撞击下的损伤程度进行评估。数值结果表明：厂房上对应于机身及发动机的撞击位置发生可接受的局部损伤；乏燃料贮存井墙体对于提高构筑物抗飞机撞击能力有重要作用。此外，构筑物外形对损伤有很大影响，圆柱形壳体的抗飞机撞击能力显著强于方形厂房，是核电厂厂房设计的优化方向之一。     

危废填埋场地下水环境影响评价研究

危险废物具有各种危害性,不仅对人体健康有着威胁,对于环境治理来说也有着极大的消极影响。就目前来说,虽然安全填埋技术已经较为成熟,但在实际实施过程中还是容易出现渗漏事故,渗漏液在地下容易穿透防渗层,从而影响地下水,所以这也是我们需要重视的问题之一。     

Urine and fecal excretion patterns of dairy cows divergent for milk urea nitrogen breeding values consuming either a plantain or ryegrass diet

Environmental degradation has been attributed to inefficient nitrogen utilization from pastoral dairy production systems. This degradation has especially been associated with the urine patch, which has been identified as a key component of nitrate leaching to waterways. However, a lack of information exists regarding the pattern of urination events and individual urination characteristics across the day, which would help inform strategic management decisions. The aim of this study was therefore to evaluate and report the patterns and characteristics of fecal and urination events throughout the day for cows divergent for milk urea nitrogen breeding values (MUNBV) on either a plantain [Plantago lanceolata L. (PL)] or ryegrass [Lolium perenne L. (RG)] diet as ways to reduce environmental impact. Sixteen multiparous lactating Holstein Friesian × Jersey cows divergent for MUNBV were housed in metabolism crates for 72 h, with all excretion events captured and analyzed. Cows selected as low for MUNBV consistently had a 65.2-kg lower urinary urea nitrogen (UUN) load (kg/ha) than high MUNBV cows for all hours of the day when consuming RG. The association between lower urinary urea loading rates and less N leaching implies a reduced environmental impact from low MUNBV cows consuming RG. When cows consumed PL, regardless of MUNBV, they had on average a 137.5-kg (UUN/ha) lower loading rate compared with high MUNBV cows on RG and a 72.2-kg (UUN/ha) lower loading rate compared with low MUNBV cows consuming RG across the day. Cows on PL also exhibited a different diel pattern of UUN load compared with cows consuming RG. Differences in the diel pattern of N excreted in feces were also detected based on MUNBV and by diet, with low MUNBV cows excreting on average 3.06 g more N in feces per event for the majority of the day compared with high MUNBV cows when consuming RG. Lower UUN loading rates and more N excreted in feces indicate a potentially lower environmental impact from low MUNBV cows when consuming RG compared with high MUNBV cows. The use of the PL diet also resulted in lower UUN loading rates and greater levels of N excreted in feces compared with RG, therefore also indicating its ability to reduce environmental impact compared with RG.     

基于Copula函数的郑州市夏季双重城市热岛及其影响因素关系分析

城市热环境变化影响城市小区域气候，探究影响因子与其作用机制，可有效减缓城市热岛现象。利用郑州市1960～2017年长序列数据，从相对热岛（RHI）和绝对热岛（AHI）两个层面探究驱动因子降雨（R）、蒸发（E）、建成区面积(B_BUA)、城镇化率(U_UR)的影响关系，利用交叉小波和小波相干探究热岛与降雨的雨热关系，采用Copula函数计算影响因子在不同取值条件下与热岛的遭遇概率。结果表明，相对热岛-相对降雨在短中周期、绝对热岛-降雨在短周期上均呈负相关关系，雨热关系不同步，且绝对热岛-降雨的关系最为显著；影响因子B_BUA、U_UR取值越大，R取值越小，则与RHI、AHI的遭遇概率越大；不同影响因子在不同评价层面，敏感性强弱不同，E在不同层面的反馈机制也不同，可见选取合适评价分析层面，有利于准确量化影响程度。     

低速冲击下的界面响应和磨损行为*

为探究低速冲击下界面响应与磨损行为之间的联系，开展多周次的低速冲击磨损实验；通过分析冲击过程中的接触力峰值、接触时长、接触力冲量、动能耗散等，研究冲击速度对接触界面的力学响应的影响；通过对冲击磨痕的磨损轮廓和形貌、磨损体积的检测分析，以及对磨痕区域元素组分变化的测试，研究冲击速度对接触界面磨损损伤行为的影响。结果表明：冲击速度的增加会导致接触界面在更短的时间内受到更强烈的力学作用；能量吸收率对冲击速度的变化不敏感，但冲击速度的提高会导致单位能量造成的磨损损伤逐渐降低；冲击磨痕可分为以塑性变形和以剥层磨损为主要损伤形式的2种区域；磨损区内经历了严重的摩擦氧化，并随着冲击速度的增加发生冲击副材料转移。因此，冲击速度越高，接触界面间的摩擦越剧烈，形成的表面氧化层避免了冲击副与基底材料的直接接触，延缓了磨损损伤的进一步发展。