Design and implementation of an integrated safety management system for compressed natural gas stations using ubiquitous sensor network

To increase awareness of safety in facilities where hazards may exist, operators, managers, and executive officers on the site should be able to monitor such facilities. However, most compressed natural gas (CNG) service stations in Korea use only local-mode monitoring, with only on-site operators to monitor the facility. To complement this local-mode monitoring, an online safety management system called Ubiquitous-gas safety management system (U-GSMS) was developed. The U-GSMS consists largely of software and hardware. The software consists of systems that can manage safety and operations, while the hardware consists of sensors installed in the gas facility and wireless communication systems using a ubiquitous sensor network (USN) technology that facilitates communication between sensors as well as between sensors and other devices. As these systems are web-based, on-site operators as well as managers and executive officers at the headquarters can more effectively and efficiently perform monitoring and safety management.     

Triethyl and tributyl phosphite as flame-retarding additives in Li-ion batteries

This study examined the influence of triethyl and tributyl phosphite (TEP and TBP) additives on the electrochemical performance of lithium-ion cells. The cell performance of the TEP- and TBP-containing electrolytes was evaluated by cyclic voltammetry, thermogravimetric analysis, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The flammability of the electrolytes was also investigated by measuring the self-extinguishing time of the electrolytes. The results showed that the TEP and TBP additives suppressed the flammability of the electrolyte, with a significant improvement in cell performance observed for the TEP additive. In addition, TEP and TBP additives improved the thermal stability of the battery and its electrochemical cell performance. Overall, 5 wt% TEP and TBP can be used as a flame-retarding additive to improve the cell performance of Li-ion batteries due to the decrease in cell impedance and SEI formation.     

Extraction of landslide-related factors from ASTER imagery and its application to landslide susceptibility mapping

The aim of this study is to extract landslide-related factors from remote-sensing data, such as Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery, and to examine their applicability to landslide susceptibility near Boun, Korea, using a geographic information system (GIS). Landslide was mapped from interpretation of aerial photographs and field surveying. Factors that influence landslide occurrence were extracted from ASTER imagery. The slope, aspect and curvature were calculated from the digital elevation model (DEM) with 25.77 m root mean square error (RMSE), which was derived from ASTER imagery. Lineaments, land-cover and normalized difference vegetation index (NDVI) layers were also estimated from ASTER imagery. Landslide-susceptible areas were analysed and mapped using the occurrence factors by a frequency ratio and logistic regression model. Validation results were 84.78% in frequency ratio and 84.20% in logistic regression prediction accuracy for the susceptibility map with respect to ground-truth data.     

Magnetic Polishing of Titanium-Nickel Alloy Stents: Surface Characterization and Catheter Deployment Test

We report here for the first time the use of magnetic polishing to improve the surface finish of titanium-nickel (TiNi) stents for better performance. We investigated the effects of polishing time and rotational speed on the average surface roughness, surface chemical contents, and push-out load of stents. The magnetically polished stents show a decrease of 2.3 to 17.9?pct in surface roughness and a lower push-out load for stent deployment from the catheter.     

Determination of Johnson-Cook constitutive equation for Inconel 601

Due to their superior thermal and mechanical properties, super alloys widely used in the aerospace industry have been well-documented in terms of AdvantEdge-based analysis of cutting characteristics rather than experimental methods. However, the well-known super alloy Inconel 601 does not have any database of its material properties in AdvantEdge, which underscores the urgency to build such a database. Hence, the current study uses the Johnson-Cook equation to build a database of Inconel 601’s material properties in AdvantEdge. To that end, drawing on a room temperature tensile test, elevated temperature tensile test and orthogonal cutting test, the current study determines the Johnson-Cook constitutive equation for Inconel 601, and verifies the reliability of the determined Johnson-Cook constitutive equation by comparing the experimental values with the analytical values.     

A study on thermal analysis of MgH2 powder made by hydriding chemical vapor deposition method

The desorption kinetics of Mg hydride made by the HCVD method was assessed by thermal analysis in order to study desorption behavior. Desorption kinetics was analyzed by the theoretical equation which was derived on the basis of a continuous moving boundary model. At various initial hydride wt% from 1.65 to 7.42, the sample was heated to 573 K at a rate of 1.0 K/min. The starting temperature of evolution of hydrogen rises higher as the initial hydride wt% increases. The number of thermal desorption peaks corresponds to the occupation sites of hydrogen. As the heating rate was increased, the peak temperatures increased; the peak temperatures for heating rates 1, 2, 3 and 4 K/min were 667, 683, 690 and 698 K, respectively. The pressure range is 0.1 to 0.2 atm for measuring. The activation energy for the decomposition of Mg hydride made by HCVD method was 166 kJ/ mol.     

The optimal design scheme of an SUGV for surveillance and reconnaissance missions in urban and rough terrain

In this paper, we propose the optimal design scheme for designing an SUGV (Small Unmanned Ground Vehicle) for the purpose of surveillance and reconnaissance in urban and rough terrain, tunnels, sewers, and caves. In general, an SUGV for military operations must be light-weight and small in size to attain portability, and must be able to overcome a variety of obstacles including stairs, curbs, and ramps in urban terrain. Consequently, we propose the optimal design scheme to find the optimal size and optimal actuation system of such an SUGV. The scheme is composed of three parts. The first is to find the optimal body length of the SUGV through estimating the CG point moving path in geometrical coordination when climbing stairs. The second is to find material having the required static friction coefficient by estimating the required traction force and wheel moment. The third is to find the actuation load by estimating the wheel load while it climbs up a ramp with ??. From this scheme, we find an optimally designed SUGV for the purposes of military operations. In this paper, to prove the efficiency of the proposed design scheme, we build an SUGV and experiment its mobility performance. The experimental results demonstrate its stair climbing performance on 20cm high and 40degree inclined ramps. The SUGV weighs 21kg and has a minimum body length of 625mm.     

Experiments and theoretical approaches on the burning behaviors of single n-heptane droplet

This study was conducted to improve the theoretical prediction of the burning characteristics of an n-heptane droplet by comparing them with experimental results. To achieve this, numerical approaches were conducted by assuming that the droplet combustion can be described by both quasi-steady behavior for the region between the droplet surface and the flame interface, and transient behavior for the region between the flame interface and ambient surrounding. Comparisons were considered for droplet diameter (d _t ), flame diameter (d _f ), flame standoff ratio (FSR), and viscous drag induced fluxes which are Stefan flux and thermophoretic flux for various initial droplet diameter (d ₀ ) and oxygen (O ₂ ) concentration conditions. It was revealed that the flame diameter (d _f ) and flame standoff ratio (FSR) initially increase dramatically and approach quasi-steady behavior within the observation period, and the flame standoff ratio (FSR) increases a little with the initial droplet diameter (d ₀ ) both experimentally and theoretically. The value of flame diameter (d _f ) decreases from its maximum value when oxygen (O ₂ ) concentration is increased from a value of 18% to 40%. The burning rate (K) constant becomes higher as the oxygen (O ₂ ) concentration increases since the increase of oxygen (O ₂ ) concentration produces a higher maximum flame temperature (d _f ) which enhances the effective thermo-physical properties of the gas-phase bounded by droplet and flame front.