Performance of residential air-conditioning systems with flow maldistribution in fin-and-tube evaporators

Refrigerant and airflow maldistribution in fin-and-tube evaporators for residential air-conditioning was investigated with numerical modeling. Fin-and-tube heat exchangers usually have a pre-defined circuitry. However, the objective in this study was to perform a generic investigation of each individual maldistribution source in an independent manner. Therefore, the evaporator and the condenser were simplified to be straight tubes for the purposes of this study. The numerical model of the R410A system, its verification and an investigation of individual maldistribution sources are presented in this paper. The maldistribution sources of interest were: inlet liquid/vapor phase distribution, feeder tube bending and airflow distribution. The results show that maldistribution reduced the cooling capacity and the coefficient of performance of the system. In particular, different phase distribution and non-uniform airflow distribution reduced the performance significantly. Different feeder tube bendings only caused a minor decrease in performance.     

The link between built environment, pedestrian activity and pedestrian-vehicle collision occurrence at signalized intersections

This paper studies the influence of built environment (BE) – including land use types, road network connectivity, transit supply and demographic characteristics – on pedestrian activity and pedestrian–vehicle collision occurrence. For this purpose, a two-equation modeling framework is proposed to investigate the effect of built environment on both pedestrian activity and vehicle–pedestrian collision frequency at signalized intersections. Using accident data of ambulance services in the City of Montreal, the applicability of our framework is illustrated. Different model settings were attempted as part of a model sensitivity analysis. Among other results, it was found that the BE in the proximity of an intersection has a powerful association with pedestrian activity but a small direct effect on pedestrian–vehicle collision frequency. This suggests that the impact of BE is mainly mediated through pedestrian activity. In other words, strategies that encourage densification, mix of land uses and increase in transit supply will increase pedestrian activity and may indirectly, with no supplementary safety strategies, increase the total number of injured pedestrians. In accordance with previous research, the number of motor vehicles entering a particular intersection is the main determinant of collision frequency. Our results show that a 30% reduction in the traffic volume would reduce the total number of injured pedestrians by 35% and the average risk of pedestrian collision by 50% at the intersections under analysis. Major arterials are found to have a double negative effect on pedestrian safety. They are positively linked to traffic but negatively associated with pedestrian activity. The proposed framework is useful for the identification of effective pedestrian safety actions, the prediction of pedestrian volumes and the appropriate safety design of new urban developments that encourage walking.     

Seismic performance assessment of steel moment frames with generic Locally Reinforced connections

Seismic performance of Steel Moment-Resisting Frames (SMRFs) with generic Locally-Reinforced (LR) connections has been investigated incorporating both earthquake-induced and modeling uncertainties. The LR connections were numerically modeled following the suggestions made by previous researches and were used to numerically model three buildings with various heights which were designed regarding the specifications of current standards. For reflecting the record-to-record (RTR) variability, the Incremental Dynamic Analysis (IDA) procedure was utilized within the Performance-Based Earthquake Engineering (PBEE) methodology. In this regard, the structures’ performance in a multitude of structural response levels was probabilistically assessed in “considering” and “neglecting” conditions of modeling uncertainties. For performing the modeling uncertainty analysis, a number of modeling parameters that best reflected the structures’ variability due to lack of knowledge were selected as random variables. Perturbing the modeling variables from their median values, a set of sensitivity IDAs were performed and a polynomial response surface was established. Incorporation of the response surface in conjunction with Monte Carlo simulation led, finally, to a fully probabilistic performance evaluation of the studied structures in varied structural response levels. The effect of modeling uncertainties in altering the predicted performances was found to be insignificant in the range of buildings and structural elements studied in this article.     

工欲善其事 必先利其器——BIM实践案例及经验体会

通过对BIM实践案例解析,指出BIM在建筑设计行业的应用前景,并总结了设计人员在工程实践中的经验体会。     

Electrical characterization of controlled and unintentional modified metal–organic contacts

A method to characterize metal–organic contacts subjected to controlled technological treatments or unintentional degradation processes is proposed. The procedure is useful to characterize different fundamental aspects of a metal–organic structure such as the height of the interface energy barrier, the presence of impurities or trapping effects and the carrier mobility. Current–voltage curves in organic diodes are analyzed and the value of the free carrier density at the metal–organic interface is extracted and discussed. The charge carrier density is chosen for this analysis as this is one of the key physical parameters in the understanding of the physical processes involved in the device operation. The extracted charge, when described as a function of the current density, gives information about the doping and impurity concentration, the effective barrier seen by the carriers at the metal–organic interface or effective barriers seen by the carriers in the hopping processes across the organic material. An important advantage of the proposed procedure is the low computational time. Also, the procedure aims to provide a quick analysis for researchers on how the physical properties of the devices are evolving when they are technologically altered or degraded.     

Study on the transformer equivalent circuit of eddy current nondestructive evaluation

The modeling of a practical configuration of nondestructive evaluation (NDE) by eddy currents (EC) generally requires extended analytical or numerical developments. This is a drawback to any understanding of the EC NDE principle and of its basic features. Nevertheless, it is possible to exploit a simple equivalent circuit based on an analogy with the operation of an electrical transformer. In this model the EC sensor constitutes the primary of the transformer whereas the evaluated conductive plate forms the transformer secondary and its electrical load. In this paper, thanks to the transformer analogy, the author obtains a simple analytical expression of the impedance of the EC sensor by using a distributed constant representation of the evaluated plate. This expression allows to exhibit some fundamental features of the EC NDE method.     

中国与欧盟、美国和日本食品标签法规标准的比较研究

食品标签包括食品的内在质量、营养、时效和食用指导等方面的信息,是消费者选择食品的重要依据之一,在日常生活中起到了维护消费者知情权,保护消费者的作用。本文通过总结欧盟、美国和日本3个地区的现行食品标签法规标准,比较分析了它们与中国食品标签法规标准的异同点,主要包括覆盖范围、法规体系形式和致敏原标识等方面,结合我国食品标签法规及标准现状,提出了一些对国外食品标签法规的借鉴性意见。      

BIM技术在水厂工程建设管理中的应用

随着工程建设管理的数字化、信息化、智慧化方向的发展趋势,应用BIM技术提高项目建设和管理过程中的智慧化和精细化,成为当前建设工程行业研究及应用的热点。以深圳某市政水厂改扩建项目为例,研究基于云端部署的BIM+互联网管理平台在水厂改扩建工程实施中的管控模式和流程,实现对工程全过程中进度、质量、安全、费用等各方面的可视化管理,提升BIM和数字化技术的应用价值。     

Activated Hepatic Stellate Cells in Hepatocellular Carcinoma: Their Role as a Potential Target for Future Therapies

Hepatocellular carcinoma (HCC) is a global healthcare challenge, which affects more than 815,000 new cases every year. Activated hepatic stellate cells (aHSCs) remain the principal cells that drive HCC onset and growth. aHSCs suppress the anti-tumor immune response through interaction with different immune cells. They also increase the deposition of the extracellular matrix proteins, challenging the reversion of fibrosis and increasing HCC growth and metastasis. Therapy for HCC was reported to activate HSCs, which could explain the low efficacy of current treatments. Conversely, recent studies aimed at the deactivation of HSCs show that they have been able to inhibit HCC growth. In this review article, we discuss the role of aHSCs in HCC pathophysiology and therapy. Finally, we provide suggestions for the experimental implementation of HSCs in HCC therapies.     

基于BIM和移动定位的施工质量管理系统

本研究基于建筑信息模型(Building Information Modeling, BIM)技术和室内移动定位技术, 研制施工质量管理系统, 用于建筑工程施工质量验收, 以解决目前施工质量验收中规范实施过程中存在的漏检、数据二次转录等问题。本研究从施工质量验收相关规范出发, 分析了施工质量验收的标准化过程与要求, 并在此基础上设计了系统功能, 建立了系统架构。然后提出了基于BIM的验收任务生成算法、移动定位集成方法等关键技术与方法, 研制了施工质量管理的原型系统。最后, 该原型系统在实际工程施工中进行了试用, 验证了该系统的可行性。