Selecting superior performance improvement policies

The changing trends in the Asian construction sector are creating both new opportunities for and threats to the domestic construction organizations. To improve the competitiveness of these organizations, senior managers are tasked with the responsibility of selecting and implementing improvement policies to enhance organizational performance. This study utilizes the system dynamics methodology to provide a careful and holistic evaluation of the policies. A model is built to represent an average performing construction organization listed on the Kuala Lumpur Stock Exchange. Long-term simulation of the validated model produces the forecasted organization performance. Three improvement policies recommended by CIDB (2000) that have different cost and benefit impact profiles are selected for evaluation. Taking into consideration the impact of the economy on the construction industry, simulated results of the policies and combination of the policies indicate that the implementation of short-term improvement policies produces superior improvement in organization performance when compared with other policies.     

Thermal properties of poly(pivalolactone)

Polypivalolactone (PPVL) is a highly crystalline polyester formed either by nucleophilic or electrophilic ring-opening polymerization of 2,2-dimethyl-β-propiolactone, commonly known as pivalolactone (PVL). The thermal properties and crystallization kinetics of the polymer formed under reaction injection molding (RIM) conditions were studied. The crystallization kinetics of PPVL were measured using differential scanning calorimetry (DSC), and Avrami theory was used to interpret the bulk crystallization kinetics. A comparison was made with commercially prepared PPVL. The kinetics data indicate laboratory prepared PPVL, which is of lower molecular weight, has similar crystallization rates compared to the higher molecular weight commercial material. The kinetics data also indicate the rate of crystallization is relatively rapid overall for PPVL, with low activation energies of crystallization. The calorimetric studies also utilized DSC and simultaneous ther-mogravimetric analysis/differential scanning calorimetry (TGA/DSC). Thermal analysis showed a clear difference in melting behavior between high and low molecular weight material, possibly a reflection of the presence of the α and γ-crystal forms of the polymer.     

A comparison of the hazard perception ability of accident-involved and accident-free motorcycle riders

Hazard perception is the ability to read the road and is closely related to involvement in traffic accidents. It consists of both cognitive and behavioral components. Within the cognitive component, visual attention is an important function of driving whereas driving behavior, which represents the behavioral component, can affect the hazard perception of the driver. Motorcycle riders are the most vulnerable types of road user. The primary purpose of this study was to deepen our understanding of the correlation of different subtypes of visual attention and driving violation behaviors and their effect on hazard perception between accident-free and accident-involved motorcycle riders. Sixty-three accident-free and 46 accident-involved motorcycle riders undertook four neuropsychological tests of attention (Digit Vigilance Test, Color Trails Test-1, Color Trails Test-2, and Symbol Digit Modalities Test), filled out the Chinese Motorcycle Rider Driving Violation (CMRDV) Questionnaire, and viewed a road-user-based hazard situation with an eye-tracking system to record the response latencies to potentially dangerous traffic situations. The results showed that both the divided and selective attention of accident-involved motorcycle riders were significantly inferior to those of accident-free motorcycle riders, and that accident-involved riders exhibited significantly higher driving violation behaviors and took longer to identify hazardous situations compared to their accident-free counterparts. However, the results of the regression analysis showed that aggressive driving violation CMRDV score significantly predicted hazard perception and accident involvement of motorcycle riders. Given that all participants were mature and experienced motorcycle riders, the most plausible explanation for the differences between them is their driving style (influenced by an undesirable driving attitude), rather than skill deficits per se. The present study points to the importance of conceptualizing the influence of different driving behaviors so as to enrich our understanding of the role of human factors in road accidents and consequently develop effective countermeasures to prevent traffic accidents involving motorcycles.     

Three‐Dimensional Branched Nanowire Heterostructures as Efficient Light‐Extraction Layer in Light‐Emitting Diodes

A facile method to fabricate three‐dimensional branched ZnO/MgO nanowire heterostructures and their application as the efficient light‐extraction layer in light‐emitting diodes are reported. The branched MgO nanowires are produced on the hydrothermally‐grown ZnO nanowires with a small tapering angle towards the tip (≈6°), by the oblique angle flux incidence of MgO. The structural evolution during the growth verifies the formation of the MgO nanoscale islands with strong (111) preferred orientation on very thin (5–7 nm) MgO (110) layer. The MgO nanobranches, then grown on the islands, are polycrystalline consisting of many grains oriented in specific directions of <200> and <220>, supported by the nucleation theory. The LEDs with the branched ZnO/MgO nanowire arrays show a remarkable enhancement in the light output power by 21% compared with that of LEDs with pristine ZnO nanowires. Theoretical calculations using a finite‐difference time‐domain method reveal that the nanostructure is very effective in breaking the wave‐guiding mode inside the ZnO nanowires, extracting more light especially in radial direction through the MgO nanobranches.     

Optimization of indoor climate conditioning with passive and active methods using GA and CFD

This study aims at the development of an optimal design tool using a genetic algorithm (GA) and computational fluid dynamics (CFD). Random variables (fluctuating outdoor conditions), passive design elements (model variables) and active design elements (HVAC system) were set up to represent a realistic building environment. A combination of designs is determined based on the relationship between fluctuating outdoor conditions and the HVAC system in the optimal design search. Building environment designs should consider both active and passive design elements because the HVAC system keeps adjusting the supply air flow rate until the indoor climate reaches target conditions when outdoor conditions are changing.     

铜引线键合中影响焊球硬度因素的研究

铜丝球焊由于其经济优势和优越的电气性能近来得到了普及,然而,在引线键合工艺中用铜丝取代金丝面临着一些技术上的挑战。多年来,IC芯片焊盘结构已经逐步适应了金丝球焊。铜在本质上比金硬度高,因此以铜线取代金线便引出了有关硬度的问题。研究了用25．4μm铜丝球焊中与键合机参数有关的铜焊球硬度特性。采用电子打火系统不同的电流和打火时间设置,用5％氢气和95％氮气组成的惰性保护气体形成了一个典型的25．4μm大小的铜焊球,研究了维氏硬度的焊球。用实验设计建立了第一和第二键合参数,进行了无空气焊球基本数据调整。通过改变电子打火系统参数。对硬度特性进行了进一步的测试。典型的键合球的大小和厚度的第一键合响应证实铜键合球的生产实力与电子打火系统的电流和打火时间有关．     

HPLC-ELSD analysis of 18 platycosides from balloon flower roots (Platycodi Radix) sourced from various regions in Korea and geographical clustering of the cultivation areas

An effective HPLC method to analyse platycosides from the balloon flower root was developed using ELSD. The optimum resolution of the platycosides was achieved on an ODS column with gradient elution of eluent A, 30 mM ammonium acetate buffer (pH 4.81): methanol: acetonitrile = 75:5:20 (v/v/v), and B, 69:5:26 (v/v/v). Amongst 18 platycosides, platycoside E showed the highest content, followed by polygalacin D₂ and 3″-O-acetylplatyconic acid A. The sum of these three compounds was recommended for quality control of balloon flower root for medicinal purposes. The samples could be clustered into groups based on platycoside content. Group I, characterised by a high concentration of platycosides, was located near the west coast of Korea, whereas group II, characterised by a low concentration of platycosides, was located inland or in mountainous area. The method could be used to control the quality of balloon flower root.     

Integrating rapid prototyping and tooling with vacuum casting for connectors

Connectors are developed to satisfy the needs of advanced technology in telecommunication switching systems and companies have several products designed to fulfil the needs of the many switching networks available. The Four-wall-header is one such product from one company. The traditional manufacturing line relies heavily on hard tooling which is both expensive and time-consuming. This paper presents an alternative method of integrating rapid prototyping technologies, in particular, stereolithography apparatus (SLA), with a vacuum casting system to produce a wide range of polyurethane parts. Altogether, three approaches are analysed and evaluated for making the moulds: rapid pattern, rapid tooling and a hybrid approach.     

Expanding the structural diversity of polyelectrolyte complexes and polyzwitterions

Charged (macro)molecules are essential components in natural materials and organisms; thus the rational design of biomimetic materials requires a holistic understanding of structure–property relationships in charged systems. We discuss recent progress in uncovering such relationships for polyzwitterions and polyelectrolyte complexes, with emphases on the synthetic strategies that were employed in systematic studies. For polyelectrolytes, discussion is confined to the effects that structural variations in polycation and polyanion structure have on the fundamental phase behavior of the corresponding polyelectrolyte complexes. In the field of polyzwitterions, both fundamental and applied properties are discussed in relation to chemical structure. Finally, we present an overview of promising chemistries that will expand the structural landscape of charged macromolecules with the aim of stimulating new research to further uncover and understand the fundamental design principles for these materials.