Showing papers by "Hong Kong Polytechnic University published in 1993"

Schirmer test. I. A review

Abstract: Since its introduction by Schirmer in 1903, the Schirmer test has been widely used for the assessment of the adequacy of tear production. Although the faults of the Schirmer test have been well documented, it is nevertheless still being used to assess tear production, especially in the diagnosis of keratoconjunctivitis sicca (KCS) and for screening potential contact lens wearers. We summarize the findings and conclusions of some of the previous studies.

Review of the tear break-up time and a closer look at the tear break-up time of Hong Kong Chinese

Abstract: The technique of assessing tear stability using the fluorescein instillation technique has been widely used in the clinical diagnosis of "dry eye" and in the screening of potential contact lens wearers. Various inconsistencies in the application of the tear break-up time (TBUT) techniques and the results obtained were noted in the literature and this review summarizes the differences and the conclusions of various investigators. The reliability of this technique using two different methods of observation was examined and the mean TBUT of Hong Kong Chinese subjects (HK-Chinese) was determined. We conclude that the TBUT can be measured reliably using either the scanning or full beam method in most patients. The mean TBUT of HK-Chinese is approximately 8 s and about 70% of HK-Chinese have TBUT's less than 10 s.

Optical characteristics of a ruthenium(II) complex immobilized in a silicone rubber film for oxygen measurement

Abstract: The optical characteristics of tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate immobilized in a silicone rubber film were studied for its application to the measurement of oxygen. The luminescence intensity and the degree of quenching of the ruthenium complex by oxygen were shown to be affected by the concentration of the complex in the silicone rubber film. The optimum concentration was found to be about 0.2 mmol dm–3. At this concentration, the silicone rubber film containing the immobilized ruthenium complex emits the highest luminescence intensity and is able to undergo a high degree of quenching of the luminescence by oxygen. The quenching curves for 20 samples containing various concentrations of the ruthenium complex were correlated with high accuracy by using a modified form of the Stern–Volmer equation. The film preparation procedure and the solvent used were found to be critical for performance. The effect of the film thickness on the luminescence intensity and the dynamic response was also studied.

Repeated visual acuity measurement: establishing the patient's own criterion for change.

Abstract: We measured visual acuity in 10 young subjects, 10 times each over a period of approximately 3 weeks, using Bailey-Lovie charts. We used a consistent end-point criterion and scored each letter read on the chart. We derived the mean and standard deviation of visual acuity measures for each subject, and for the group. The standard deviation for the group was about 3 times that of the individuals in the group. We calculated the criterion for reduction of visual acuity for the group, as group mean plus 1.96 group standard deviations; use of this criterion would consistently fail to detect patients with clinically significant reductions in visual acuity. We recommend that visual acuity be measured to threshold for every patient. Measuring visual acuity between three and five times provides an estimate of the patient's variability and allows a criterion for reduction of visual acuity to be established for the individual patient. Use of this criterion will enhance the sensitivity of visual acuity measurement as a diagnostic tool.

A theoretical analysis of the effect of crystallographic orientation on chip formation in micromachining

Abstract: The effect of crystallographic orientation on the shear zone formation in micromachining has been analysed with a single crystal cutting model. Based on the minimum shear strength criterion, a range of shear angle values is found to exist. The most likely shear plane is the one that has the most negative texture softening factor among the ones with the same minimum shear strength. Theoretical findings for the shear angle and cutting force variations compare well with published experimental data. The significance of the microplasticity analysis to the understanding of chip formation in micromachining is discussed.

Schirmer Test. II. A Clinical Study of Its Repeatability

Abstract: In most parts of the world, the Schirmer test (ST) is still the main test used by optometrists for the assessment of tear adequacy in the screening of potential contact lens wearers and as an aid in the diagnosis of "dry" eye. We tested the reliability of a 1-min ST in nine normal Hong Kong-Chinese (HK-Chinese) subjects during five to seven visits over a period of 2 weeks. For 4 of the subjects, the test consistently measured 0 mm/1 min, and 68% of the test results were less than 6 mm/1 min, a value suggested as the lower limit for normal asymptomatic eyes. The results obtained were inconsistent and it is concluded that the ST is unreliable and of little clinical value in this population.

Age, gender, and tear break-up time

Abstract: We investigated the effect of age and gender on the tear break-up time (TBUT) of 2 groups of normal, asymptomatic subjects [92 Hong Kong-Chinese (HK-Chinese) and 76 Singapore-Chinese (S-Chinese)] using the conventional fluorescein-instillation technique. The mean TBUT (+/- SD) is 6.5 (+/- 4.0) s for the S-Chinese and 7.8 (+/- 2.4) s for the HK-Chinese. The mode was 7.0 s for HK-Chinese and 5.0 s for S-Chinese. About 80% of the subjects of each group have TBUT less than 10 s. The TBUT of both groups of Chinese decreases with age. It was found that TBUT was significantly different between the two sexes in the S-Chinese but no equivalent effect was observed in the HK-Chinese.

Biaxial bending design of arbitrarily shaped reinforced concrete column

Abstract: The paper presents an iterative procedure to perform the exact design of arbitrarily shaped reinforced concrete members against a combination of axial force an biaxial bending moments. The suggested method is believed to be divergence-proof and is capable of handling sections with reinforcement layout so unsymmetrical that the origin of the Mx-My reference axes falls outside the iso-load contour corresponding to the applied axial load. The rate and reliability for convergence in this method make it suitable for use in practical design. Oddly shaped concrete sections commonly adopted in bridge abutments and core wall systems can be handled, and the minimum steel area required in resisting the design loadings is determined. This leads to a more economical and safer design for reinforced concrete structures.

Luminescent dicyanoplatinum(II) complexes as sensors for the optical measurement of oxygen concentrations

Abstract: The emission spectra of [Pt(L)(CN) 2 ] (L=4,7-diphenyl-1,-10-phenanthrolline or 4,4'-di-tert-butyl-2,2'-bipyridine) immobilized in silicone rubber are concentration dependent. At low concentrations of platinum complex a single emission peak is observed. Oxygen quenching of the emission is shown to be a sensitive method for measuring oxygen concentraions in the gas phase. The polymer films containing the platinum complex are very stable, and no photochemical degradation was observed when they were subjected to step changes in the oxygen concentration. The films are not sensitive to alkyl halides such as chloroform and dichloromethane

Spectroscopy, molecular structure, and electrochemistry of rhenium(V) oxo and imido complexes of 1,4,8,11-tetraazacyclotetradecane (cyclam)

Abstract: trans-[ReO 2 (cyclam)]ReO 4 1 / 2 H 2 O, trans-[ReO(OEt)(cyclam)](ClO 4 ) 2 , and trans-[Re(NPh)(OH)(cyclam)](ClO 4 ) 2 (cyclam=1,4,8,11-tetraazacyclotetradecane) were prepared and structurally characterized by X-ray crystallography The structure of trans-[ReO 2 (cyclam)]ReO 4 1 / 2 H 2 O is quite similar to that of the previously reported trans[ReO 2 (cyclam)]Cl and trans-[ReO 2 (cyclam)]PF 6

Halogenated platinum porphyrins as sensing materials for luminescence-based oxygen sensors

Abstract: Luminescent platinum porphyrins with halogen substituents on the meso-aryl and pyrrole rings Pt(TDCPP), Pt(TFMPP) and Pt(Br8TMP)[TDCPP =meso-tetra(2,6-dichlorophenyl)porphyrin, TFMPP =meso-tetra(3,5-bis(trifluoromethyl)phenyl)porphyrin, Br8TMP =meso-tetramesityl-β-octabromoporphyrin] were immobilized inside silicone rubber films and tested as sensors for optical measurement of oxygen concentrations in the gas phase. The presence of halogenated substituents was found to increase the photostability of the metalloporphyrins. On the other hand, heavy halogen atoms such as bromine cause a decrease in the quantum yield and lifetime. The films have a moderately fast response towards changes in oxygen concentration and are immune to common gaseous interferents such as chlorine, sulfur dioxide and halothane at concentrations well above those normally encountered.

Application of field modelling technique to simulate interaction of sprinkler and fire-induced smoke layer

Abstract: The interaction between the sprinkler water spray and the fire induced convective air flow is studied using the field modelling technique. A system of equations describing conservation of momentum, enthalpy and mass is used to simulate the physical picture. Solution of the problem. is divided into two parts: gas phase and liquid phase. In the gas phase, a two-equation k – e model is used to account for the turbulent effect with the solid wall boundary described by the traditional wall functions. Numerical finite difference method is employed to solve the system of coupled non-linear partial differential equations. The equations are firstly discretized by the Power Law scheme and then solved using the Pressure Implicit with Splitting of Operators (PISO) algorithm. For the liquid phase, the sprinkler water spray is described by a collection of water droplets with different values of initial velocity components and diameter calculated from the Rossin-Rammler distribution function. The motion of each...

The cotton thread test: a brief review and a clinical study of its reliability on Hong Kong-Chinese.

Abstract: Fifty-four asymptomatic Hong Kong-Chinese subjects were recruited and their lacrimation was assessed using a modified cotton thread test (CTT). The CTT was performed once on each subject and, for seven subjects, the test was repeated seven times on different days over a period of 2 weeks to test the reliability of the CTT. The mean (+/- SD) CTT value (length of wetting of thread in millimeters for a 1-min testing period) of this group of subjects was 22.8 (+/- 9.4) mm/min. Repeated measures analysis of variance revealed no significant difference in the CTT values made on different days. The CTT was found to be superior to the conventional Schirmer test in terms of comfort and consistency of results obtained. A brief review of some studies and results reported by previous investigators using the CTT is also presented for comparison.

Intraocular pressure in a selected sample of myopic and nonmyopic Chinese children.

Abstract: The intraocular pressure (IOP) measurements for 30 myopic and 30 nonmyopic children between 6 and 9 years of age were extracted from eye examination records. The mean IOP of 30 myopic children was 13.69 mm Hg (SD 3.4) and that of 30 nonmyopic children was 11.55 mm Hg (SD 2.06). The difference between the two is significant. These results suggest that IOP may play a role in the determination of refractive error.

A new zero-voltage switching DC/DC boost converter

Abstract: A pulsewidth-modulated (PWM) zero-voltage-switching quasi-resonant boost converter operating at constant switching frequency is presented. In contrast to the frequency-modulated (FM) zero-voltage-switching quasi-resonant boost converter, this converter possesses better controllability and higher operating performance, and overcomes the instability caused by the parasitic oscillation. The principle of operation and performance of the converter are presented. Its two-dimensional state trajectories and steady-state characteristic curves are derived which are useful for the converter design. Both the SPICE simulation and experimental result agree with the theoretical prediction. >

Refractive errors in Hong Kong Chinese pre-school children.

Abstract: Five hundred and seventy Chinese children aged between 36 and 65 months were recruited for refractive examination. The results show that both the spherical and cylindrical components of the refractive error tend to decrease with increasing age, although the changes were not statistically significant. The results of the present study, together with those of earlier studies carried out on Hong Kong Chinese children of different ages, show a pattern in the change of refractive errors in local children during the first 17 years of life. The combined results show that the average spherical refractive error decreases rapidly in hyperopic power during the 1st and the 6th to the 10th years of life; the astigmatic power decreases rapidly in the 1st year of life and remains thereafter rather constant until the age of 17 years.

Thailand's tourism and Hotel industry:

Abstract: Thailand's tourism industry, which surged in the 1980s, may collapse if appropriate planning measures aren't undertaken

Antisymmetric bifurcations in a compressible pressure- sensitive circular cylinder under axisymmetric tension and compression

Abstract: This paper examines antisymmetric bifurcations of geometric diffuse modes, including buckling and surface rumpling modes, for a cylinder of finite length under axisymmetric loadings. The analysis includes the effects of nonnormality, transverse isotropy, and confinig stress on the appearance of antisymmetric geometric diffuse modes and their relationship to the onset of localization

On the simulation of atrium fire environment in hong kong using zone models

Abstract: This article is a report studying the potential fire risk in atrium buildings in Hong Kong. The general shapes of the atrium buildings are sur veyed and classified into three types. Fire environments in those three types of atria are simulated using three mathematical fire zone models, the FIRST, the ASET and the FAST, developed at the Building and Fire Research Laboratory, NIST, U.S.A. In addition, simulations on four actual atria are also performed. All the results show that smoke will bring many problems, and controlling smoke is essential to providing safety in the atrium spaces.

An efficient three-dimensional semi-implicit finite element scheme for simulation of free surface flows

Abstract: An efficient semi-implicit finite element model is proposed for the simulation of three-dimensional flows in stratified seas. The body of water is divided into a number of layers and the two horizontal momentum equations for each layer of water are first integrated vertically. Nine-node Lagrangian quadratic isoparametric elements are employed for spatial discretization in the horizontal domain. The time derivatives are approximated using a second-order-accurate semi-implicit time-stepping scheme. The distinguishing feature of the proposed numerical scheme is that only nodal values on the same vertical line are coupled. Two test cases for which analytic solutions are available are employed to test the proposed scheme. The test results show that the scheme is efficient and stable. A numerical experiment is also included to compare the proposed scheme with a finite difference scheme.

A simplified Newton Iteration Method with linear finite elements for transient unsaturated flow

Abstract: A simplified Newton iteration method with Galerkin linear finite elements is developed for the solution of the nonlinear transient unsaturated flow equation in “mixed” form. The use of the Galerkin linear finite element method in the spatial discretization produces a recurrence equation in which the interaode hydraulic conductivity is represented by an integrated average expression which generates the exact Darcy flow flux through each element under the steady horizontal flow condition. The numerical computation of the integrated average hydraulic conductivity using Simpson's 1/3 rule leads to an accurate solution even in the presence of a sharp front. In the time discretization using a backward Euler scheme, the standard Newton iteration method is simplified by taking account of the integrated average expression of the hydraulic conductivity and the diffusion-dominated nature of the flow process. The resulting two-level scheme is of the same efficiency on a per-iteration basis as the modified Picard scheme but converges at a faster rate.

Medical Clothing: A TUTORIAL PAPER ON PRESSURE GARMENTS

Abstract: Pressure therapy is generally accepted as an effective means of preventing and controlling hypertrophic scarring after burn injury. Pressure treatment based principally on the use of pressure garments is widely used in Hong Kong and many other countries. These garments are tailor‐made to the individual patient's measurement to provide a uniform and firm support to body contours, and they are designed individually for the area of injury. Attempts to review the existing practice of the various kinds of pressure garments on patients, and to provide a better understanding of the present use of fabric and production methods employed in the manufacturing of the garments. Includes a brief account of the problems encountered by both the patients and the medical staff.

Photophysical properties, electrochemistry and crystal structure of nitridoosmium(VI) complexes of 2,3-diamino-2,3-dimethylbutane

Abstract: The complex [OsN(H2L)2Cl]Cl2·2H2O 1 was prepared by the reaction of [NBu4][OsNCl4] with 2,3-diamino-2,3-dimethylbutane (H2L) in methanol Treatment of 1 with CF3SO3H under argon gave [OsN(H2L)2][CF3SO3]32 which on prolonged standing in acetonitrile yielded [OsN(HL)(H2L)2][CF3SO3]23 The crystal structures of 1 and 3 have been determined by X-ray crystallography: 1, triclinic, space group, P(no 2), a= 7176(1), b= 7273(2), c= 10823(2)A, α= 10120(2), β= 10688(2), γ= 9796(2)°, Z= 1; 3, monoclinic, space group, C2/c(no 15), a= 15810(3), b= 12766(3), c= 16225(4)A, β= 11025(2)°, Z= 4 The emission spectrum of 1 at 77 K shows vibrational progression with spacing of 1050 cm–1 characteristic of the ground-state ν(OsN) stretch In 01 mol dm–3 CF3CO2H the cyclic voltammogram of 2 displays a 3H+–3e– reduction wave at –034 V vs saturated calomel electrode assignable to the reduction of OsVIN to OsIII–NH3

Physical properties of a sprinkler water spray

Abstract: This paper reports an experimental study on the physical properties of a sprinkler water spray. The mass flux density, shape of spray pattern, size distribution and velocity of water droplets discharged from two types of 15 mm orifice sprinkler heads were measured. Three operating flow conditions of the sprinkler system, including one specified for the Ordinary Hazard class under the LPC rules for sprinkler design, were set. The sprinkler head was installed above finished floor levels of either 2 m or 2.2 m. The median droplet size was found to be related to the water pressure and the orifice diameter of the sprinkler head as proposed by Dundas. The droplet size distribution function can be fitted by a Rosin–Rammler function.

Banking Services for Young Intellectuals

Abstract: Reports a survey on the banking behaviour of 300 college students in Hong Kong which confirms several findings from Western countries. These include: limited banking demand of students; popularity of split banking in account ownership; price‐consciousness of students; and importance of locational convenience and on‐campus promotion. Argues that in order to turn this segment into a lucrative one, bankers need to adopt a long‐term perspective and place more emphasis on service quality and promoting the concept of “one‐stop banking”.