Excess noise measurement in In0.53Ga0.47As

The excess noise due to impact ionization has been measured explicitly for the first time in In/sub 0.53/Ga/sub 0.47/As. By using a phase sensitive detection technique, the noise due to avalanche current was determined even in the presence of high tunneling currents. The excess noise due to pure electron injection measured on a series of thick In/sub 0.53/Ga/sub 0.47/As p/sup +/-i-n/sup +/ diodes suggests large electron to hole ionization coefficient ratio between 3.7 at electric field of 310 kV/spl middot/cm/sup -1/ to 5.3 at 260 kV/spl middot/cm/sup -1/. Excess noise was also measured at fields as low as 155 kV/spl middot/cm/sup -1/ suggesting that significant impact ionization occurs at these low fields. The multiplication and excess noise calculated using published ionization coefficients and ignoring dead space effects, gave good agreement with the experimental data for mixed and pure electron injection

Fire Hazards of Refrigerants in Air Conditioning Control System

Air conditioning control systems are commonly installed in restaurants, commercial buildings, office buildings and institutional buildings in Hong Kong. The systems invariably involve the use of fans for moving the air, filters for cleansing, ducts for air distribution, a control system for regulating the amount of heating or cooling automatically and a refrigerating plant connected to the heat exchange surface. The ducts in turn present the possibility of spreading fire and smoke throughout the building or areas served. According to the local Code of Practice for Minimum Fire Service Installations and Equipment [1], when a ventilation or air conditioning control system to a building is provided, it shall stop mechanically induced air movement within a designated fire compartment. In order to fulfil such requirement, the architects and building services engineers will design to install associated equipment of air conditioning control systems to satisfy the relevant fire safety requirements of the local authority, which includes the provision of fire resisting ducting, fire dampers, smoke detectors and fire resisting cables, etc. However, lessons learned from past experience reveal that owners or property management staff of the buildings or covered areas and maintenance contractors will mainly concern the efficiency and energy saving of the systems without paying much attention to the fire hazards arising from the use of refrigerants. It is also noted that fire or explosion incidents [2] involving air conditioning control systems are often attributed to improper maintenance work conducted by maintenance contractors, such as refilling the refrigerating plant with poor quality refrigerants, recharging refrigerants incompatible with the metal parts of the system, refilling refrigerants at high pressure resulting in bursting of piping and joints, valves contaminated by grease, presence of an ignition source in close proximity of the refrigerating plant, etc. In general, refrigerants present two basic hazards [3], namely toxicity and flammability. Refrigerants mix readily with air and if flammable, may reach flammable concentrations ready to be ignited by an ignition source. As diffusion may not take place rapidly enough to avoid the hazards in the event of leakage, fire or explosion may occur. With reference to a recent fire with explosion incident involving air conditioning control system in a restaurant in Hong Kong, this paper will outline and discuss the fire hazards of refrigerants in air conditioning control systems

Temperature dependence of breakdown and avalanche multiplication in In0.53Ga0.47As diodes and heterojunction bipolar transistors

The avalanche multiplication and impact ionization coefficients in In/sub 0.53/Ga/sub 0.47/As p-i-n and n-i-p diodes over a range of temperature from 20-400 K were measured and shown to have negative temperature dependence. This is contrary to the positive temperature dependence of the breakdown voltage measured on InP/In/sub 0.53/Ga/sub 0.47/As heterojunction bipolar transistors (HBTs) in this and previous works. It is shown that the collector-base dark current and current gain can be the overriding influence on the temperature dependence of breakdown in InP/In/sub 0.53/Ga/sub 0.47/As HBTs and could explain previous anomalous interpretations from the latter

Factors of Entrepreneurial Personality Characteristics on Business Failure of SMEs

The purpose of this research is to identifythefactorofentrepreneurialpersonality characteristics that can lead to the business failure of Small and Medium Enterprises (SME) in Melaka, Malaysia. This research used the Big Five Personality Model or OCEAN Model as the independent variables which include openness, conscientiousness, extraversion, agreeableness, and neuroticism. The quantitative method had been conducted by the researcher to collect the data through the questionnaire that was distributed and answered by the respondent of this research. A total of 379 Small and Medium Enterprises (SME) that established and operate in the business in Melaka, Malaysia had been participating in this data collection process. The result of the analysis showed that openness, conscientiousness, extraversion, and neuroticism have significant relationship with the factors of entrepreneurial personality characteristics on business failure of Small and Medium Enterprises (SME) in Melaka, Malaysia. There is one factor of entrepreneurial personality characteristics which is agreeableness has no significant relationship with factors of entrepreneurial personality characteristics on business failure of Small and Medium Enterprises (SME) in Melaka, Malaysia. The result of this study contributes in improve the rate of business success among SME in Melaka, Malaysia by eliminating the possibility of business failure.Keywords—Entrepreneurial personality characteristics, Big Five Personality Model, business failure, Small and Medium Enterprises (SME), Melaka.

Proposed fire safety strategy on airport terminals

Fire safety strategy for airport terminals will be proposed in this paper. The local airport terminal is taken as an example. Special features of airport terminals will be outlined. The retail areas are identified as places with higher fire risk. Standards, codes and design guidelines used overseas are reviewed and compared with the local codes. Based on the study, fire safety strategy is suggested to have four parts: passive building construction for fire safety; active fire protection systems or fire services installation; fire safety management; control of risk factors. All four parts will be discussed in this paper. Suggestions are made to give a fire safe airport terminal.Department of Building Services Engineerin

Molecular Beam Epitaxy of Ga(In)AsN/GaAs Quantum Wells towards 1.3µm and 1.55µm

In this article, we report an attempt of extending the InGaAsN materials towards 1.3µm and 1.55µm wavelength. All these InGaAsN samples are grown in a plasma-assisted solid-source molecular-beam epitaxy (SS-MBE) system. Our experiments revealed that the nitrides could be grown with both direct nitrogen beam and dispersive nitrogen. The nitrogen incorporation rate could be reduced by the presence of indium flux. The interaction between nitrogen and indium might lead to 3D growth mode and growth dynamics. It is proved that the increasing growth rate reduces the nitrogen incorporation efficiency. The data for nitrogen sticking coefficient are somewhat contradictive. The growth with dispersive nitrogen source causes the improvement of material quality. Fixed indium flux is a better way for the wavelength control. Also, we report some growth optimization work for better PL property and the annealing effect on the samples. Literature is sometimes reviewed for comparison.Singapore-MIT Alliance (SMA

Stability of Pharmaceutical Cocrystal During Milling: A Case Study of 1:1 Caffeine-Glutaric Acid

yesDespite the rising interest in pharmaceutical cocrystals in the past decade, there is a lack of research in the solid processing of cocrystals downstream to crystallization. Mechanical stress induced by unit operations such as milling could affect the integrity of the material. The purpose of this study is to investigate the effect of milling on pharmaceutical cocrystal and compare the performance of ball mill and jet mill, using caffeine-glutaric acid (1:1) cocrystal as the model compound. Our results show that ball milling induced polymorphic transformation from the stable Form II to the metastable Form I; whereas Form II remained intact after jet milling. Jet milling was found to be effective in reducing particle size but ball milling was unable to reduce the particle beyond certain limit even with increasing milling intensity. Heating effect during ball milling was proposed as a possible explanation for the difference in the performance of the two types of mill. The local increase in temperature beyond the polymorphic transformation temperature may lead to the conversion from stable to metastable form. At longer ball milling duration, the local temperature could exceed the melting point of Form I, leading to surface melting and subsequent recrystallization of Form I from the melt and agglomeration of the crystals. The findings in this study have broader implications on the selection of mill and interpretation of milling results for not only pharmaceutical cocrystals but pharmaceutical compounds in general

Lung cancer in Chinese women: Evidence for an interaction between tobacco smoking and exposure to inhalants in the indoor environment

10.1289/ehp.0901587Environmental Health Perspectives11891257-126

Meromorphic traveling wave solutions of the complex cubic-quintic Ginzburg-Landau equation

We look for singlevalued solutions of the squared modulus M of the traveling wave reduction of the complex cubic-quintic Ginzburg-Landau equation. Using Clunie's lemma, we first prove that any meromorphic solution M is necessarily elliptic or degenerate elliptic. We then give the two canonical decompositions of the new elliptic solution recently obtained by the subequation method.Comment: 14 pages, no figure, to appear, Acta Applicandae Mathematica