Enhancement of thermal performance in a sintered miniature heat pipe

Abstract

The performance of a sintered miniature heat pipe is enhanced. With the capillary limitation, porosity takes priority over the wick structure parameters that would affect the heat transfer capacity. Since sintered dendritic copper powder has higher porosity, it is used to mix with pore former (Na₂CO₃) in experiments for increasing porosity, and hence enhancing the thermal performance. The results show that, for a heat pipe with a 3mm outer diameter and 200 mm effective length, the heat transfer rate is up to 16.5W and the thermal resistance is 0.9°C/W. In comparison with the unmixed case, the performance increases about 40%.     

Variations in BOLD response latency estimated from event‐related fMRI at 3T: Comparisons between gradient‐echo and Spin‐echo

Functional magnetic resonance imaging (fMRI) commonly uses gradient‐recalled echo (GRE) signals to detect regional hemodynamic variations originating from neural activities. While the spatial localization of activation shows promising applications, indexing temporal response remains a poor mechanism for detecting the timing of neural activity. Particularly, the hemodynamic response may fail to resolve sub‐second temporal differences between brain regions because of its signal origin or noise in data, or both. This study aimed at evaluating the performance of latency estimation using different fMRI techniques, with two event‐related experiments at 3T. Experiment I evaluated latency variations within the visual cortex and their relationship with contrast‐to‐noise ratios (CNRs) for GRE, spin echo (SE), and diffusion‐weighted SE (DWSE). Experiment II used delayed visual stimuli between two hemifields (delay time = 0, 250, and 500 ms, respectively) to assess the temporal resolving power of three protocols: GRE_TR1000, GRE_TR500, and SE_TR1000. The results of experiment I showed the earliest latency with DWSE, followed by SE, and then GRE. Latency variations decreased as CNR increased. However, similar variations were found between GRE and SE, when the latter had lower CNR. In experiment II, measured stimulus delays from all conditions were significantly correlated with preset stimulus delays. Inter‐subject variation in the measured delay was found to be greatest with GRE_TR1000, followed by GRE_TR500, and the least with SE_TR1000. Conclusively, blood oxygenation level‐dependent responses obtained from GRE exhibit greater CNR but no compromised latency variations in the visual cortex. SE is potentially capable of improving the performance of latency estimation, especially for group analysis. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 215–221, 2013     

Combining singular points and orientation image information for fingerprint classification

Fingerprint classification is crucial to reduce the processing time in a large-scale database. Two popular features used are the singularities and orientation information and they are complementary. Therefore, an algorithm based on the interactive validation of singular points and the constrained nonlinear orientation model is proposed. The final features used for classification comprises the coefficients of the orientation model and the singularity information. This resulted in very compact feature vector which is used as input to an SVM classifier to perform the classification. The experiments conducted on the NIST database 4 show the effectiveness of the proposed method in producing good classification result.     

Development of an assessment framework for green highway construction

Abstract

The objective of this research is to develop a framework for the assessment of green highway projects. Highway construction is chosen from among the various types of large‐scale infrastructure because they cover broad areas and take up a large share of a nation's infrastructure development. After completing a literature review we employ the Max‐Min Fuzzy Delphi method to identify the major categories and their corresponding items most suitable for assessing the “greenness” of a highway project. The five major categories identified are: preservation of the eco‐system, plantations to reduce CO₂ emission, preservation of material resources, waste reduction, and water conservation. The Analytical Hierarchy Process (AHP) is then employed to determine the weighting of the major categories as well as the sub items in each category. The end result is an assessment rating framework to assess the “greenness” of a highway construction project.     

On the Anti-social Behaviour Control in Hong Kong's Public Housing

In 2003, the Housing Department launched a marking scheme which aimed to improve environmental hygiene in public housing estates in Hong Kong. Although the scheme can potentially stop anti-social behaviour and other misconduct in public housing estates, the choice of public housing tenants as the sole target of control has not been clearly explained. Therefore, this study attempts to justify this administration-driven marking scheme. It appears that welfare conditionality cannot fully justify the scheme because public housing tenants are not the only recipients of housing welfare in Hong Kong. In addition, discriminating between public housing tenants and the most deprived is not defensible. More importantly, not all the offences prescribed in the marking scheme are socially undesirable. However, the substance of the scheme seems to match the ideologies of Chinese legalism quite well, and the scheme appears to be an initiative by the Hong Kong Housing Authority to strengthen its sovereignty over public housing resources in the city.     

Microcomputer loop communication network design

Abstract

An optical illumination method was used to examine the relationship between the variation of capacitance and the interface trap states of an MOS capacitor after various charge‐temperature agings. The peaks in the illumination‐induced capacitance‐voltage curves were found to be caused neither by the lateral nonuniformities of interface charges nor by the nonuniformities of the illumination intensities, but by the existence of interface trap states. This can be used as a quick method to directly identify the interface trap states.     

Generalization and evaluation of vectorial tolerances

In recent years, vectorial tolerancing has emerged as a new alternative for representing workpiece tolerances. In contrast to conventional geometric tolerances which originated from hard gauging practices, vectorial tolerancing follows the working principle of coordinate measuring machines and CAD/ CAM systems. Moreover it provides feedback from measurement directly to manufacturing process control. Many believe it is a better tolerancing method to tie design, manufacuturing, and measurement together. However, the current proposal of vectorial tolerancing has some limitations. First, the currently adopted orientation vector is not sufficient for representing true 3D orientations. As a result, the orientation of a free form surface cannot be properly established. Second, there is lacking a unified and consistent method for the evaluation of vectorial tolerances. This paper proposes a new orientation vector which provides a more general mathematical basis for representing vectorial tolerances. It enables true 3D orientation representation and relates tolerances to the functional requirement. With the improved mathematical definition, a systematic tolerance evaluation approach becomes possible for both analytical geometric elements and free-form surfaces. Computer simulations and real-world applications are studied to validate this new approach.     

Risk factors associated with traffic violations and accident severity in China

With the recent economic boom in China, vehicle volume and the number of traffic accident fatalities have become the highest in the world. Meanwhile, traffic accidents have become the leading cause of death in China. Systematically analyzing road safety data from different perspectives and applying empirical methods/implementing proper measures to reduce the fatality rate will be an urgent and challenging task for China in the coming years. In this study, we analyze the traffic accident data for the period 2006–2010 in Guangdong Province, China. These data, extracted from the Traffic Management Sector-Specific Incident Case Data Report, are the only officially available and reliable source of traffic accident data (with a sample size >7000 per year). In particular, we focus on two outcome measures: traffic violations and accident severity. Human, vehicle, road and environmental risk factors are considered. First, the results establish the role of traffic violations as one of the major risks threatening road safety. An immediate implication is: if the traffic violation rate could be reduced or controlled successfully, then the rate of serious injuries and fatalities would be reduced accordingly. Second, specific risk factors associated with traffic violations and accident severity are determined. Accordingly, to reduce traffic accident incidence and fatality rates, measures such as traffic regulations and legislation—targeting different vehicle types/driver groups with respect to the various human, vehicle and environment risk factors—are needed. Such measures could include road safety programs for targeted driver groups, focused enforcement of traffic regulations and road/transport facility improvements. Data analysis results arising from this study will shed lights on the development of similar (adjusted) measures to reduce traffic violations and/or accident fatalities and injuries, and to promote road safety in other regions.     

A numerical study of secondary flow and large eddies in a driven cavity

This paper reports on the application of a newly developed LES flow solver to compute a true three-dimensional flow. The research also investigates the behavior of turbulence statistics by comparing transient simulation results to available data based on experiments and simulations. An extensive discussion on the results such as energy spectrum, velocity profiles and time trace of velocities is carried out in the research as well. Based on the results obtained, the application of the flow solver for a turbulent three-dimensional driven cavity flow by using three grids with varying densities is proven. In addition, the research successfully verifies that in many instances computational results agreed reasonably well with the reference data, and the changes in the statistical properties of turbulence with respect to time are closely related to the changes in the flow structure and strength of vortices. The focus of this study is on the prediction of a subgrid scale Reynolds shear stress profiles, and the results show that the standard model is able to reproduce general trends measured from experiments. Furthermore, in certain areas inside the cavity the computed shear stress values are in close agreement with experimental data.