9,463 research outputs found
The electronic properties of doped single walled carbon nanotubes and carbon nanotube sensors
We present ab initio calculations on the band structure and density of states
of single wall semiconducting carbon nanotubes with high degrees (up to 25%) of
B, Si and N substitution. The doping process consists of two phases: different
carbon nanotubes (CNTs) for a constant doping rate and different doping rates
for the zigzag (8, 0) carbon nanotube. We analyze the doping dependence of
nanotubes on the doping rate and the nanotube type. Using these results, we
select the zigzag (8, 0) carbon nanotube for toxic gas sensor calculation and
obtain the total and partial densities of states for CNT (8, 0). We have
demonstrated that the CNT (8, 0) can be used as toxic gas sensors for CO and NO
molecules, and it can partially detect Cl toxic molecules but cannot detect
HS. To overcome these restrictions, we created the B and N doped CNT (8, 0)
and obtained the total and partial density of states for these structures. We
also showed that B and N doped CNT (8, 0) can be used as toxic gas sensors for
such molecules as CO, NO, Cl and HS.Comment: 12 pages, 13 figure
Scale Model Experiments of Toxic Gas Production from the Combustion of Polymers when Applied with Different Droplet Sizes of Water Mist
This research experimentally investigated the combustion of polymeric materials with water mist application in an enclosure, with an emphasis on the production of toxic gases. Two different diameters, ~100 and ~260 μm, were tested. The experimental conditions were determined based on Froude similarity laws for low drop Reynolds number conditions. Droplets and polymers’ physical and chemical properties influence the burning/extinguishing behavior and toxic-gas evolution. In general, larger droplets can extinguish a fire in a shorter time, and toxic gas concentrations in a test chamber decreased more rapidly. However, the large droplets tended to cause the flame expansion phenomenon for thermoplastics by splashing molten polymer. This flame expansion phenomenon led to a rapid increase in toxic-gas production rate. For a smaller size of water droplets, the formation of a char layer tended to slow down the fire-extinguishing process, which caused continuous CO production
Early clinical, pulmonary function and blood gas studies in victims of Bhopal tragedy
Clinical, Pulmonary function and blood gas studies carricd out in 129 symptomatic toxic gas exposed
individuals 1-3 months after exposure had revealed that pulmonary function measurements such as
FVC, FEV1 and FMF 25-75% were significantly lower in toxic gas exposed subjects and 57 subjects
(44.2%) had ventilatory impairment. The predominant type of ventilatory defect was combined
obstruction and restriction. Of these 57 subjects, 5 (9%) had severe respiratory impairment. With
increasing severity of exposure, there was a tendency for a higher proportion of subjects to have
increasing impairment in pulmonary function and this trend was significant statistically (P<0.001).
Isolated small airway disease was present in 9 (7%) subjects. 20.3% of patients with normal physical
findings and 19.1% with normal chest roentgenograms had abnormal pulmonary junction. Arterial
hypoxemia and ventilatory abnormalities were predominant in severely exposed patients. Further
studies are required to identify the subgroup o/patients with Reactive Airways Dysfunction Syndrome.
Long term follow-up is essential to categorise the pulmonary syndromes due to toxic gas exposure
Design of pulse jet coolant delivery system for minimal quantity lubricant (IP MQL) operation
Minimum quantity lubrication (MQL) machining is one of the promising solutions to
the requirement for reducing cutting fluid consumption. The work here describes MQL
machining in a range of lubricant consumption of 2.0-2.355ml/s, which is between 10–
100 times lesser than the consumption usually adopted in industries. MQL machining in
this range is called pulse jet coolant delivery system. A specially designed system, the
IP MQL, was used for concentrating small amounts of lubricant onto the cutting
interface. The performance of concentrated spraying of lubricant in pulse jet coolant
delivery system design was simulated and compared with that of current ‘Pulse Jet
MQL’ systems. The concentrated spraying of lubricant with a specially designed system
was found to be effective in increasing tool life in the pulse jet coolant delivery system
range
Evolution engine technology in exhaust gas recirculation for heavy-duty diesel engine
In this present year, engineers have been researching and inventing to get the optimum of less emission in every vehicle for a better environmental friendly. Diesel engines are known reusing of the exhaust gas in order to reduce the exhaust emissions such as NOx that contribute high factors in the pollution. In this paper, we have conducted a study that EGR instalment in the vehicle can be good as it helps to prevent highly amount of toxic gas formation, which NOx level can be lowered. But applying the EGR it can lead to more cooling and more space which will affect in terms of the costing. Throughout the research, fuelling in the engine affects the EGR producing less emission. Other than that, it contributes to the less of performance efficiency when vehicle load is less
Organic-Based Microwave Frequency Absorbers Using Corn Stover
Commercial antenna test chambers (anechoic) currently use polyurethane foam absorbers on chamber interiors to eliminate undesired radio-frequency (RF) reflections. While effectively absorbing microwave signals, polyurethane material particulates over time adding contaminants to clean rooms and reducing absorber lifetime. These absorbers also release toxic gas when operating under high temperatures and pose a health risk to direct-contact personnel. This paper presents reflectivity analysis and performance of alternative organic-based (corn stover) microwave frequency absorbers for use in anechoic chambers. These absorbers are composed of renewable materials and eliminate the toxic gas release problem for polyurethane materials under high power test conditions. Preliminary results show that the organic absorbers perform at levels comparable to commercially-available absorber panels
High frequency Alternating Current (AC) tangent delta
Power cables are constantly subjected to thermal, electrical and mechanical stresses during their service life which leads to ageing of the insulation material. Ageing of the insulation means that the insulator degrades or gets older. When the insulation is degraded it does not have the same physical properties as compared to the new cables, which basically means that the risk of failure has been increased. So, it is necessary to carry out a diagnostic test to resolve the possible problem that may occur in cable insulation so that precautionary action can be taken to avoid unnecessary in-service failure of the underground cable [1]. Dissipation factor or tangent delta measurement in either time or frequency domain are used to identify water tree degraded XLPE cables with high moisture content or moisture ingression through poor jointing, diagnostic tests based on [2], [3]. In practice, standard laboratory electrical test equipment utilizing power frequency (PF) i.e. 50Hz to 60Hz testing is used. Hence, large static transformer was installed in the laboratory to cater any large capacitance test sample for high voltage testing. These existing tangent delta diagnostic test methods are bulk assessment technique that cannot sectionalize or pin point the water tree or any other conductive defect. In addition, both this tangent delta measurement technique which utilizes standard 0.1Hz and 50Hz equipment is not capable to extract the tangent delta values of accessories from the bulk assessment. It can only diagnose the overall condition of the complete cable system that includes cable, joints and terminations. Since medium voltage underground (MVUG) cables in utilities are in service for many years, it is crucial to develop a method to sectionalize or identify the defective components
Fireworthiness of transport aircraft interior systems
The key materials question is addressed concerning the effect of interior systems on the survival of passengers and crew in the case of an uncontrolled transport aircraft fire. Technical opportunities are examined which are available through the modification of aircraft interior subsystem components, modifications that may reasonably be expected to provide improvements in aircraft fire safety. Subsystem components discussed are interior panels, seats, and windows. By virtue of their role in real fire situations and as indicated by the results of large scale simulation tests, these components appear to offer the most immediate and highest payoff possible by modifying interior materials of existing aircraft. These modifications have the potential of reducing the rate of fire growth, with a consequent reduction of heat, toxic gas, and smoke emission throughout the habitable interior of an aircraft, whatever the initial source of the fire
Numerical Evaluation of Wind Speed Influence on Accident Toxic Spill Consequences Scales
This study aims to evaluate numerically the influence of wind speed on scales of environmental harmful consequences caused by accidentally spilled toxic liquid evaporated from the surface of a free-form outlined spill spot. A coupled problem of the gas-dynamic movement of a toxic air-mixture cloud in the surface layer of the atmosphere under the influence of wind and a negative toxic inhalation impact on a human in an accident zone is solved by means of mathematical modelling and computer experiment. Physical processes of toxic liquid evaporation from the spill spot, formation of a mixture of toxic gas with the incoming air, and further dispersion of a hazardous gaseous chemical in the atmosphere under various wind speed conditions are investigated. A three-dimensional non-stationary mathematical model of the turbulent movement of a gas-air mixture is used for obtaining distribution of relative mass concentration of toxic gas impurities in time and space. The model takes into account the complex terrain, compressibility of the gas flow, three-dimensional and non-stationary nature of actual physical processes, different toxic properties of chemical substances, and arbitrary contour shape of the toxic spill spot. A probabilistic harmful impact model based on using a modernized probit analysis method is used to obtain fields of the conditional probability of a fatal human injury resulting from toxic gas inhalation. This model extracts relative mass concentration of toxic gas that could cause negative impact on humans at any control point during calculation time step exposition, collects integral toxic dose values from the multicomponent gas mixture dynamics model, calculates a value of the probit function for the corresponding toxic inhalation dose dangerous factor, and automatically assesses the human fatal injury conditional probability using partial cubic Hermitian spline. This technique allows environmental safety experts assessing the scale of considered type technogenic accident consequences numerically depending on wind speed conditions and elaborating the means to mitigate them to acceptable levels
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