Quantification of Polycyclic Aromatic Hydrocarbons in Tea and Coffee Samples of Mumbai City (India) by High Performance Liquid Chromatography

This paper describes a method for quantification of sixteen polycyclic aromatic hydrocarbons (PAHs) in tea and coffee samples of Mumbai City with the help of reversed phase high performance liquid chromatography with UV-VIS detector. This method is based on liquid–liquid extraction followed by clean up with C-18 cartridge. Concentration of total PAHs in different brands of tea and coffee samples varied from 18.79 to 31.37 μg/L and from 16.47 to 18.24 μg/L, respectively. Mean concentration of total PAHs was 27.56 μg/L in tea and 17.20 μg/L in coffee. Recoveries at different concentration levels were higher than 68% in samples of tea and coffee. Detection limit was found to be low (0.0006 ng) for anthracene and highest (0.174 ng) for naphthalene with relative standard deviation between 0.4%–7%.     

实验室能力验证中的分割水平检测样品与稳健统计技术

论述了分割水平检测样品和稳健统计技术在对实验室能力验证活动中的应用,并对导致CNAL T040水中金属元素检测能力验证计划中部分结果异常的原因进行了分析。     

某大型装备液冷机组振动测试及减振优化

目的了解大型装备液冷机组振动情况;评估工作环境人员舒适性;采取合理措施,降低大型装备的液冷机组振动对装备可靠性及装备中工作人员的身体健康的影响。方法对某大型装备的液冷机组开展振动测试及舒适性评估工作,并依据振动分析结果对原有减振方案进行减振优化。结果对比原有减振方案和优化方案对应测点的振动响应,发现优化方案的振动响应明显减小,最大衰减5.55 dB。减振优化后,振动量值从0.555m/s~2下降到0.295m/s~2,根据国家标准GB/T13441.1-2007中的规定,人员在此环境工作时,不会感到不舒适,人员舒适性满足标准要求。结论工作环境人员舒适性满足相关标准要求,减振优化方案效果明显。装备服役后,使用情况良好,进一步证明了减振优化的有效性。     

A Parallel Computation Tool to Enable Dynamic Sensitivity and Model Performance Analysis of APEX: Evapotranspiration Modeling

Global sensitivity analysis can be used for assessing the relative importance of model parameters on model outputs. The sensitivity of parameters usually indicates a temporal variation due to variation in the environmental conditions (e.g., variation in weather or plant growth). In addition, the size of averaging window by which the outputs of a model are aggregated or averaged may impact parameter sensitivities. In this study, temporal variation of parameters sensitives, model performance, as well as the impact of the size of time‐averaging window on evapotranspiration (ET) prediction using the Agricultural Policy/Environmental eXtender (APEX) model are investigated. To achieve these goals, an open‐source package named PARAPEX was developed in R and used to perform dynamic sensitivity and model performance analysis of APEX using parallel computation. PARAPEX reduced the computation time from 5,939 to 379 s (using 20 and 1 computation nodes, respectively). The sensitivity analysis results indicated the parameters accounting for the reducing effect of plant cover on evaporation from the soil surface, the effect of soil on the plant root growth, and the effect of cycling and transformation dynamics of organic matter at the top soil layer as the top sensitive parameters based on the mean daily simulated ET and the Nash–Sutcliffe model performance measure. The dynamic performance analysis indicated poor ET predictions by APEX during the growing seasons. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Thermal performance of ice-making machine with a multi-channel evaporator

An experimental investigation is presented in this paper on the vapor compression refrigeration cycle used in an ice-making machine with a multi-channel evaporator. To study the operation performance of the refrigeration system in the ice-making machine, the fluid temperature distribution in multi-channel evaporating coils are tested and the dynamic variations in each cooling loop are investigated during the ice-generating phase. The results show that the external cooling loops have the largest temperature fluctuations caused by the large initial refrigerant injecting mass flow and the external environmental disturbances. For the inner cooling loops, the related temperature profiles of different test points have relative stable variations. To reduce the temperature fluctuations of the outside loops, it is suggested to reduce the initial refrigerant mass flow and adjust the initial opening of the thermal expansion valve. Moreover, it is the normal phenomenon for the slight temperature variations for the temperature curves of different test points, caused by the adjustment of thermal expansion valve. During the ice-making process, both the sensible heat removal phase and latent heat removal phase are experienced successively. To remove the sensible heat of water, the refrigerant system is operating in high efficiency with test points having a rapid linear temperature reduction. While for eliminating the latent heat of ice, it requires much more power supply, the relating test points have a temperature decrease with fluctuations. To improve the operation performance of ice machine, some suggestions and improvements are proposed.     

Can real-life driving ability be predicted by the Maintenance of Wakefulness Test?

Objective: Drowsy driving is a profound road safety issue. In patients with excessive daytime sleepiness (EDS), the Maintenance of Wakefulness Test (MWT) is commonly used to evaluate driving ability. However, there is little evidence that MWT predicts driving performance, and several sleep latency cutoffs have been suggested.

Methods: Based on a retrospective chart analysis of patients with an MWT and a driving ability assessment between January 2006 and November 2014, we identified 63 studies in 60 patients. The driving ability assessment judged the patients as qualified or disqualified for commercial driving. MWT latencies to 3?s of alpha activity, 3?s of drowsiness (microsleep), and sleep onset were compared between qualified and disqualified patients and their validity to identify driving qualification was evaluated.

Results: Disqualified patients had shorter alpha, microsleep, and sleep latencies, but the latency distributions were widely overlapping. MWT accuracy to predict driving performance was poor: two thirds of short sleep latencies were false positives. Adding information from alpha and microsleep latencies added little extra accuracy.

Conclusions: MWT results correlate poorly with driving performance in a 2-h test irrespective of sleep latency cutoff or added alpha/microsleep latency data. Better diagnostic tools are needed to evaluate driving performance in patients with EDS.     

基于Windows DEA模型的我国自然灾害应急公共投入绩效研究

为提升自然灾害应急公共投入绩效评价的精准性、科学性,运用动态绩效评价Windows DEA模型,结合应急处置结果,对我国近年来自然灾害领域的应急公共投入绩效进行全面系统评价,研究结果表明:我国应急公共投入效率不高且有较大改善空间;应急公共投入效率较高的省（区、市）未能产生辐射效应;我国应急公共投入效率呈现“滞后性”,即当年投入的应急公共投入在当年未得到相应产出。     

新型环保水基渗透探伤剂的配制及性能研究

渗透探伤是一种重要的无损探伤技术。研究渗透性液体物性参数影响渗透过程的机制对渗透剂新产品的研发具有重要指导意义。配制了一种水基探伤用渗透性液体,探究了其表面张力、黏度和所用表面活性剂的HLB值对其铺展能力、毛细爬升高度、平衡渗透面积和渗透速度的影响。结果表明,液体的表面张力主要影响其铺展能力、毛细爬升高度和平衡渗透面积。表面张力越大,铺展能力越差,毛细爬升高度越大,平衡渗透面积越大。液体的黏度主要影响其渗透速度,黏度越大,渗透速度越慢。液体所用表面活性剂的HLB值对渗透效果没有明显的影响。     

A comparative analysis of safety management and safety performance in twelve construction projects

IntroductionSafety management in construction is complicated due to the complex “nature” of the construction industry. The aim of this research was to identify safety management factors (e.g., risk management and site management), contextual factors (e.g., organisational complexity) and combinations of such factors connected to safety performance. Method: Twelve construction projects were selected to compare their safety management and safety performance. An analytical framework was developed based on previous research, regulations, and standards where each management factor was defined. We employed qualitative comparative analysis (QCA) to produce case knowledge, compare the cases, and identify connections between the factors and safety performance. The material collected and analyzed included, for example, construction planning documents, reports from OHS-inspections, safety indicators, and interviews with project leaders and OHS experts. Results and conclusions: The research showed that: (a) the average score on 12 safety management factors was higher among projects with high safety performance compared to projects with low safety performance; (b) high safety performance can be achieved with both high and low construction complexity and organizational complexity, but these factors complicate coordination of actors and operations; (c) it is possible to achieve high safety performance despite relatively poor performance on many safety management factors; (d) eight safety management factors were found to be “necessary” for high safety performance, namely roles and responsibilities, project management, OHS management and integration, safety climate, learning, site management, staff management, and operative risk management. Site management, operative risk management, and staff management were the three factors most strongly connected to safety performance. Practical implications: Construction stakeholders should understand that the ability to achieve high safety performance in construction projects is connected to key safety management factors, contextual factors, and combinations of such factors.     

Rivals or allies: How performance‐prove goal orientation influences knowledge hiding

Previous research suggests that performance‐prove goal orientation is positively related to knowledge hiding. However, we argue that this effect depends on the focus of performance feedback (i.e., individual‐ and group‐focused feedback), which shapes the nature of the competitive expression of performance‐prove goal orientation (i.e., intragroup and intergroup oriented). We conducted three studies to test our theoretical model. The results of Study 1 with time‐lagged data from 128 part‐time MBA students showed that performance‐prove goal orientation was positively related to knowledge hiding when performance feedback focused more (vs. less) on individual performance but was negatively related to knowledge hiding when performance feedback focused more (vs. less) on group performance. Study 2 replicated these moderation findings in an experimental study of 210 undergraduate students. Study 3 again replicated the moderation effects using multisource data from 317 employees and their supervisors. It also included creativity as an outcome of knowledge hiding and illustrated the distal consequence of the moderation effects of individual‐ and group‐focused performance feedback. We then discussed the implications for the theory and practice of performance‐prove goal orientation and knowledge hiding.