An experimental reactor for kinetic studies: continuously-fed batch reactor

The use of a continuously-fed batch reacter (CFBR) as an experimental tool for the kinetic studies is presented for liquid- and gas-phase reactions, and noncatalytic gas-solid reactions. An experimental CFBR run is demonstrated using the reaction involving sucrose conversion to substantiate the theoretical results. The concept used for the CFBR is the fact that at an extremum of concentration the rate of concentration change is zero. For the liquid- and gas-phase reactions, the CFBR can be used as an alternative to the CSTR. For slow reactions, the rate determined from a CFBR run is more accurate than the rate determined from a CSTR run. Determination of the rates over the entire conversion range is made easy for fast reactions with the use of the CFBR. Results are extended to noncatalytic gas-solid reactions. It is shown that the fractional change of reacting surface area of the solid reactant can be obtained using the CFBR under the limiting condition of negligible effect of mass transfer.     

Case-Based Reasoning in Construction Management

Case-based reasoning (CBR) is a highly effective technique in the artificial intelligence (AI) domain capable of solving or providing suggestions for the current problem by storing and retrieving results of previous cases. In the experience-oriented construction industry, knowledge and assessments of previous experience are critical to resolving problems that may reoccur. Applying CBR to construction management overcomes some drawbacks of other AI technologies and adheres to computer application needs in industry. CBR provides an alternative in solving experience-oriented problems. This article not only presents a typical CBR approach but also investigates its potential applications in construction management. An example shows how CBR can be used to estimate construction duration and costs of building construction projects at the preliminary design stage.     

Evaluating unauthorized appendages in private apartment buildings

Hong Kong is a densely populated city where high-rise buildings are common. In such an environment, building failures can pose a serious threat. Unauthorized building works, which are constructed without prior approval and consent from the government, are responsible for certain building-related accidents. In particular, those unauthorized building works attached to the external envelopes of buildings endanger the lives not only of their occupants, but also of passers-by and they cause damage to properties themselves. An overview of the proliferation of unauthorized building works in Hong Kong is provided followed by the first known empirical study on this topic. After inspecting 323 apartment buildings in two districts, the factors affecting the proliferation of unauthorized building works were analysed. It was found that buildings with amenities incorporated into their designs generally had fewer unauthorized building works on their external envelopes. However, owners associations or property management companies did not have any influence on unauthorized building work numbers for their buildings. These findings have far-reaching implications on the formulation of government policies for building safety. The formation of statutory owners associations or the engagement of property management companies is not effective in containing the unauthorized building work problems in Hong Kong. Community education and stricter law enforcement would be more effective.

Hong Kong est une ville très peuplée où les bâtiments de grande hauteur sont très répandus. Dans un tel environnement, les défauts de construction peuvent constituer une menace sérieuse. Les travaux de construction non autorisés, exécutés sans l'approbation préalable et le consentement du gouvernement, sont responsables d'un certain nombre d'accidents liés aux constructions. En particulier, les travaux non autorisés sur les enveloppes extérieures des bâtiments mettent en danger non seulement la vie des occupants mais aussi celles des passants; elles peuvent aussi provoquer des dégâts sur les bâtiments proprement dits. Cet article contient une vue générale de la prolifération des travaux de construction non autorisés à Hong Kong ainsi que la première étude empirique connue concernant ce sujet. Après inspection de 323 immeubles d'habitation dans deux quartiers, on a analysé les facteurs concernant la prolifération des travaux de construction non autorisés. Il en ressort que les bâtiments avec des commodités intégrées à la conception comportent généralement moins de travaux non autorisés sur leurs enveloppes extérieures. Toutefois, les associations de propriétaires ou les sociétés de gestion immobilière n'ont eu aucune influence sur le nombre de travaux de construction non autorisés en ce qui concerne leurs bâtiments. Ces conclusions ont des implications lourdes de conséquences sur la formulation des politiques officielles en matière de sécurité des bâtiments. La constitution d'associations légales de propriétaires ou l'engagement d'entreprises de gestion immobilière ne sont pas efficaces et ne parviennent pas à résoudre le problème des travaux de construction non autorisées à Hong Kong. Il serait plus efficace de former les communautés et de faire respecter la loi avec une plus grande vigueur.

Mots clés: immeubles d'habitation, sécurité des bâtiments, gouvernance, bâtiments résidentiels, annexes non autorisées, travaux de construction non autorisés, Hong Kong     

On using a communication-mapping model for environmental management (CMEM) to improve environmental performance in project development processes

This paper examines the existing environmental management communications practice among project participants in project development processes. There is a growing pressure for all project participants to extend their traditional business objectives of only lowering cost and shortening project duration to improve environmental performance. In achieving better environmental performance, it is essential to collect responses from project participants including project clients, consultants, contractors and various sub-contractors to build up collaboration. As this collaboration is based largely on communications among various parties, the validity and effectiveness of the communications are essential to enable effective collaboration. By investigating practical applications, this paper identifies gaps of communications among project participants, and shows that these gaps present barriers to the improvement of environmental performance in construction. Possible solutions to communication gaps are investigated, leading to the proposal of a communication-mapping model for environmental management (CMEM). The CMEM is proposed as a method aimed at effectively implementing environmental management in construction practice. Data used for this study are collected from six construction projects in Hong Kong. A free-flow mapping approach is also employed to assist the investigations. It is believed that this study can help improving communications among project participants and environmental performance in the construction industry.     

X-ray Powder Diffraction Structural Phase-Transition Study of La(Cr1-xMnx)O3 (x = 0 to 0.25) Using the Rietveld Method of Analysis

The La(Cr_1-xMn_x)O₃ (x = 0 to 0.25) system exhibited a displacive phase transformation from an orthorhombic to a rhombohedral structure at temperatures ranging from about 256°C at x = 0 to 305°C at x = 0.25. The Rietveld method of X-ray analysis was used to determine structural characteristics and to assay phase concentrations when multiple phases were present. Indications were that the Mn ions on the B site affected the transition temperature through an ionic size effect; i.e., Mn³⁺, with a larger ionic size than Cr³⁺, increased the transition temperature while the presence of the smaller Mn⁴⁺ ions reduced it. A hysteresis was also observed with respect to the phase transformation as a function of temperature. The phase transformation was associated with a change in the rotation of the oxygen octahedra from an antiphase to an in-phase tilt sequence.     

Stability of tapered bars of circular cross-sections under semi- and quasi-tangential torques

A torque may be classified as semi- or quasi-tangential, depending on whether it is generated by two couples or one couple of direct forces. Both types of torque may cause a torsionally loaded bar to buckle at certain critical values. This paper presents an analytical approach for investigating the instability of tapered bars of circular cross-sections subjected to torques of the semi- or quasi-tangential type. The analysis results indicate that a distinction must be made in practice between the two types of torque, as their critical loads have a difference of a factor of two. For the special case of a bar with constant cross-sections, the present results reduce to those given by Ziegler.     

Incorporation of (1-14C)oleic acid and (1-14C)arachidonic acid into lipids in the subcellular fractions of mouse brain

The response of the astroglial population of the dentate gyrus molecular layer to removal of that region's primary afferent was investigated using Cajal's gold sublimate method. Deafferentation caused the astrocytes to hypertrophy, an effect which was detectable at 24 hr and maximal at 72-96 hr post-lesion. Following this, the astroglia entered a lengthy period of gradual atrophy. Counts of the astrocytes in the various sublayers of the molecular layer led to the conclusion that these cells migrate into denervated dendritic areas from neighboring, nondeafferented zones.     

Simulation and experimental analysis for hysteresis behavior of a piezoelectric actuated micro stage using modified charge system search

The main goal of this study is to investigate the hysteresis behavior of a piezoelectric actuated micro stage. The hysteresis of piezoelectric actuators (PA) is formulated using the generalized Duhem model (GDM) and a modified charge system search (CSS) is proposed to identify the hysteresis model. Different from the present CSS method, the proposed method applies a construction factor to prevent converging to a local optimum. The modified CSS is used to evaluate the parameters of the GDM to compare with the particle swarm optimization (PSO). The use of MCSS-based optimization is superior to the CSS and the PSO for identification of the GDM. The experimental result also validated the modeling correctness using the proposed method.