Transition temperature control of liquid crystalline poly(heptene sulphone)s

Liquid crystalline poly(heptene sulphone)s containing cholesteryl undecylenic ester and cholestanyl undecylenic ester were synthesized. The polymers displayed cholesteric mesophases during thermal transition. The clearing temperatures were from 114 to 172 °C depending on the molar ratio of mesogenic esters in the polymers. Received: 27 March 1997/Revised: 24 June 1997/Accepted: 27 June 1997     

多探头扫描探针显微镜系统

虽然扫描探针显微镜具有高分辨率等优异性能，但不足之处也显而易见。较低的扫描和采样速度使工作效率不高。多探针或多探头的概念就是为提高扫描探针显微镜的工作效率而提出的。为了摸索多探头扫描探针显微镜的特点和解决半导体工业晶片检测的实际需求，我们设计了四探头SPM。本文主要介绍我们研制的四探头扫描探针显微镜系统，并探讨多探头SPM的设计方法。     

Perinatal candidiasis and transient maternal candidemia: report of one case

It has been postulated that acute appendicitis is the first serious disease to emerge with the adoption of fibre-depleted diets. The incidence of acute appendicitis is rising in Africa and this has been attributed to socio-economic advancement and the adoption of low residue diets. The aim of this study was to determine whether income levels and the level of dietary fibre intake play any role in the rising incidence of acute appendicitis in Ghana. Between June and November 1997 patients aged 13 years and above with acute appendicitis were studied. Their monthly net income levels or those of their parents if they were minors were ascertained and a dietary fibre questionnaire completed on each patient in order to assess his or her dietary fibre intake. The clinical details of each patient were recorded on a proforma. One hundred and seventy-three patients, 128 males and 45 females, mean age 29.2 (range 13-75) years were studied. 14 percent presented within 6 h, 46.8 percent within 24 h and 41.6 percent after 2 or more days. 53.2 percent had acute appendicitis and 42.8 percent presented with complicated appendicitis. The appendix was normal in 4.0 percent. Two patients died (1.2 percent). 61.3 percent of patients were low income earners and 38.7 percent were high income earners. The overall dietary fibre intake was 39.4 g per day with no significant difference in fibre consumption between low income earners (39.0 g/day) and high income earners (43.5 g/day). We conclude that dietary fibre may not be the important factor in acute appendicitis and other luminal and/or morphological factors may be predisposing factors.     

An experience of teaching for learning by observation: Remote-controlled experiments on electrical circuits

In order to facilitate senior primary school students in Hong Kong to engage in learning by observation of the phenomena related to electrical circuits, a design of a specific courseware system, of which the interactive human–machine interface was created with the use of an open-source software called the LabVNC, for conducting online remote-controlled experiments was developed in this study. The statistically significant results of a pre-test–post-test evaluation study showed that the LabVNC-based system has potential to promote students to learn the target topic under the approach of learning by observation. The assertion of the teacher on the pedagogical value of the remote-controlled experimentation and the enthusiasm of students in using the LabVNC-based system reveal the potential to integrate the use of the LabVNC-based system with the practice of scientific experiments. Based on the feedback from the teacher and students, the existing LabVNC-based system will be refined under the design-based research approach.     

Explication and sharing of design knowledge through a novel product design approach

At the beginning of the 21st century, the emergence of knowledge management is viewed as a natural evolution. Knowledge management is defined as the formal management of knowledge for facilitating creation, access, and reuse of knowledge, typically by using advanced technology. To be easily communicated and shared, tacit knowledge has to be explicated as explicit knowledge (e.g., in product specification or a scientific formula or production rules); and this explicit knowledge has to be shared as applicable data through the use of information technology. Product design is such a business process that a great part of the design knowledge is often a tacit type, being difficult to share, or available only in forms of natural language documents. However, the expertise recorded in these documents is an essential resource of successful competition in the market. This paper presents a knowledge explication and sharing approach; specifically focusing on the knowledge management of modular product design. The solution approach involves modeling modular products, formulating the explicit knowledge, discovering new design knowledge with data mining, and sharing the knowledge with web services technology. The proposed approach is to be applied to an actual case of motherboard design/assembly in one of the largest PC manufacturing enterprises.     

Dynamic programming approach for analyzing delayed product differentiation

Cutting down lead-time and expanding product variety are two essential means to improving customer service. To recognize the specific requirements of markets, many computer companies are adopting a build-to-order (BTO) policy. Under this policy, original equipment manufacturing (OEM) companies that are component suppliers for these computer companies are compelled to offer their components near the end-users within shortened lead-times. This forces the OEM companies to develop their branches and warehouses that can implement some assembly operations for the products that have been semifinished at the central company. The main problem faced by these OEM companies is determining the differentiation point of the production processes where the products are diversified at the central company. In this paper, a dynamic approach is proposed to construct an analysis framework for this problem. This approach can deal with situations that do not differentiate all products at the same time. This is especially relevant when the investment cost or processing cost for process normalization and modularization of process redesigning is dependent on products in common parts or sets or on their differentiation sequence. This approach is different from the results claimed in previous research. An example of a real case is then applied to illustrate the applicability of the model.     

A novel method of composite electroplating on lap in lapping process

A lapping machine with the composite electroplating to dress the lap in-process has been developed. Mirror surface lapping operations on silicon wafers were conducted by plating tin with 0.3 μm Al₂O₃ particles on the lap surface in-process. During the lapping process, the cathode current density ranged from 0.28 to 1.68 A/dm². Results showed that the removal rate of the silicon wafer for this process ranges from 0.12 to 0.18 μm/min, which is about 2.5–3.5 times higher than those without dressing in-process. This indicates that this novel method can produce sharp new edges on the lap surface continuously. It is found that the growth rate for the coating thickness of the lap is almost equal to its wear rate at the cathode current density of 0.28 A/dm². Hence, it is not necessary to replace and dress during the lapping by using this method. The silicon wafer can be lapped to a surface roughness, R_a=2 nm in this novel method.     

Tungsten doped chromium nitride coatings

Chromium tungsten nitride films were deposited using magnetron sputtering with ion beam assistance. The content of the films was controlled through the power supplied to the chromium and tungsten targets. Results indicate that the tungsten atoms incorporated into chromium nitride films and formed the chromium tungsten nitride solid solution phase. Moreover, results of this study provide further insight into how various concentrations of tungsten affect the lattice constant, preferred orientation, crystallite size, surface morphology, hardness, internal stress, and adhesion of the films.