The current method for determining the flammable limits for a gas in a closed spherical vessel is based on a specification of the maximum pressure increase during the combustion, usually from 5 to 10% of the initial ambient pressure. This approach is completely arbitrary and is not fundamentally based. For most hydrocarbons this pressure boundary and hence the flammable limit is easy to determine experimentally since an abrupt pressure drop occurs at the flammable limit as the fuel concentration in air is adjusted. However, for some species, particularly hydrogen mixed with air, the drop in maximum combustion pressure is not very abrupt and the fuel concentration can range several percentage points depending on the arbitrary criterion used for the flammable limit.
This paper will discuss a new approach for determining the flammable limits for a gas in a spherical vessel. The approach is based on the maximum second derivative of pressure rise. The second derivative is indicative of an acceleration of the combustion rate and is, hence, fundamentally based. Furthermore, we have identified a new approach to determine the downward propagating flammable limits based on the combustion time, that is, the time that the gas actually burns in the vessel.

Taguchi gas sensors are commonly used sensors to measure gas concentration. The detection method utilizes only sensor DC resistance changes for determination of various gases concentration. Unfortunately, such technique leads to false results due to cross-sensitivity of gas sensors at presence of other gases. Such adverse effects can be reduced by applying fluctuation enhanced sensing and temperature modulation of sensor which gather more information about ambient atmosphere than the DC resistance. The measurement setup of voltage fluctuations across the gas sensor as well as the selected measurement results are presented. New indicators of gas detection have been proposed. The indicators utilize fluctuations and DC resistance measurements at two different temperatures of the gas sensor.

Cosmic-ray-induced neutrons are important to estimate the environmental dose for the aircraft crews. New Bonner spheres were designed for high-energy neutrons up to 10 GeV and their response functions were evaluated using the MCNPX transport code. The spheres consisted of an inner polyethylene shell covering the ³He-filled spherical proportional counter, an outer polyethylene shell, and an inlet metal shell. Cosmic-ray-induced neutrons were measured at Korea Research Institute of Standards and Science together with the 10 existing Bonner spheres. Results of the neutron spectra showed that the response functions of the multi-shell Bonner spheres were calculated accurately.

Cloud base height is an important parameter for climate studies as well as aviation safety. Ceilometers or LIDARs can measure this parameter but are usually expensive instruments. In this paper, a low-cost method to measure cloud base height based on consumer digital cameras and stereophotogrammetry is presented. The performance of the system is evaluated by comparison with LIDAR measurements. It is shown that the prototype can also measure the wind speed and direction at cloud height.

Pollutant measurement prediction is a topic of great interest in the area of environmental measurements and health protection. Stationary description of pollutants is an approach in which the amount of pollutant per time unit is considered constant. But in many circumstances, this quantity is subject to a flow delay. In this paper we introduce a novel pseudo-stationary modeling based on Delay Differential Equations (DDE) that can better reflect forced and spontaneous emissions of pollutants from industrial plants and natural processes respectively. Emissions of Volatile Organic Compouund (VOC) from industrial plants and leakage of decayed radioactive wastes are respectively a concrete example. The concentration of VOC that are present in the atmosphere can be predicted by using mathematical models. Among the deterministic models that utilize an Eulerian approach, the Gaussian model can be interpreted as a simple solution to the problem. However, the variables that are present in such model, and which are subjected to simplifying assumptions, may not objectively represent reality.
The purpose of this work is to utilize a delay logistic equation for the modeling of the data regarding VOC emissions, and to demonstrate its efficiency through a comparison with the classical Gaussian Plume Model.