Channel Estimation Scheme for WLAN Systems with Backward Compatibility

IEEE 802.11n standards introduced a mixed‐mode format frame structure to achieve higher throughput with multiple antennas while providing backward compatibility with legacy systems. Although multi‐input multi‐output channel estimation was possible only with high‐throughput long training fields (HT‐LTFs), the proposed scheme utilizes a legacy LTF as well as HT‐LTFs in a decision feedback manner to improve the accuracy of the estimates. It was verified through theoretical analysis and simulations that the proposed scheme effectively enhances the mean square error performance.     

Synthesis of Mg2FeH6 by hydrogenation of Mg/Fe powder mixture prepared by cold roll milling in air: Effects of microstructure and oxygen distribution

Herein, we describe the synthesis of Mg₂FeH₆ by hydrogenation of a 2.1 Mg:Fe (mol/mol) powder mixture prepared by cold roll milling (CRM) in air. The thickness of Fe layers and the amount and distribution of oxygen with number of CRM passes were systematically analyzed. CRM-induced microstructural changes were shown to play an important role in Mg₂FeH₆ formation. Although repeated CRM effectively decreased the Fe layer thickness to values sufficient for the fast formation of Mg₂FeH₆, too much CRM passes decreased the total degree of hydrogenation due to inevitable oxidation of Mg in air. Both microstructure refinement and minimal oxidation are the prerequisites for efficient Mg₂FeH₆ synthesis, with the former condition being achievable by optimizing the number of milling passes, and the latter one requiring CRM under an inert atmosphere.     

Discrimination of palm olein oil and palm stearin oil mixtures using a mass spectrometry based electronic nose

To discriminate mixing ratios for mixtures of palm olein oil and palm stearin oil, an electronic nose based on mass spectrometer (MS-electronic nose) and GC were used. The intensities of each fragment from the palm olein oil and palm stearin oil by the MS-electronic nose were used for discriminant function analysis (DFA). When palm olein oil is mixed with palm stearin oil, more than 3% of stearin oil can be estimated by DFA. The obtained data were used for DFA. DFA plot indicated a significant separation of pure palm olein oil and palm stearin oil. The added concentration of palm stearin oil to palm olein oil was highly correlated with the first discriminant function score (DF1). When palm stearin oil was added to palm olein oil, it was possible to predict the following equation; DF1= −0.112×(conc. of palm stearin oil)+0.416 (r²=0.95). When palm stearin oil was added to palm olein oil, peak area of GC was correlated to DF1 by MS-electronic nose with ratio of palm olein oil vs palm stearin oil. The MS-electronic nose system could be used as an efficient method for the authentication of oil.     

Effect of Cr addition on room temperature hydrogenation of TiFe alloys

This paper discusses the effect of AB₂ (Ti(Cr, Fe)₂) phase on the hydrogenation properties of a Ti–Fe–Cr alloy system. Five Ti–Fe–Cr based alloys were fabricated by varying the Cr content. The microstructural analysis results revealed that the fraction of the Ti(Cr, Fe)₂ phase increased with the increasing Cr content. The first hydrogenation test results indicated that all the alloys could absorb a significant amount of hydrogen at room temperature (30 °C) without a separate activation process. This behavior improved when the Ti(Cr, Fe)₂ phase existed in the AB phase; the kinetics of the first hydrogenation tended to increase with the fraction of Ti(Cr, Fe)₂ phase. The enhancement in the first hydrogenation kinetics of the Ti–Fe–Cr based alloys was attributed to the synergetic effect of the interface between the AB and Ti(Cr, Fe)₂ phases and the inherent fast hydrogenation of the Ti(Cr, Fe)₂ phase. However, the total hydrogen storage capacity decreased when the fraction of Ti(Cr, Fe)₂ phase increased.     

Systematic planning to optimize investments in hydrogen infrastructure deployment

The introduction of hydrogen infrastructure and fuel cell vehicles (FCVs) to gradually replace gasoline internal combustion engine vehicles can provide environment and energy security benefits. The deployment of hydrogen fueling infrastructure to support the demonstration and commercialization of FCVs remains a critical barrier to transitioning to hydrogen as a transportation fuel. This study utilizes an engineering methodology referred to as the Spatially and Temporally Resolved Energy and Environment Tool (STREET) to demonstrate how systematic planning can optimize early investments in hydrogen infrastructure in a way that supports and encourages growth in the deployment of FCVs while ensuring that the associated environment and energy security benefits are fully realized. Specifically, a case study is performed for the City of Irvine, California – a target area for FCV deployment – to determine the optimized number and location of hydrogen fueling stations required to provide a bridge to FCV commercialization, the preferred rollout strategy for those stations, and the environmental impact associated with three near-term scenarios for hydrogen production and distribution associated with local and regional sources of hydrogen available to the City. Furthermore, because the State of California has adopted legislation imposing environmental standards for hydrogen production, results of the environmental impact assessment for hydrogen production and distribution scenarios are measured against the California standards. The results show that significantly fewer hydrogen fueling stations are required to provide comparable service to the existing gasoline infrastructure, and that key community statistics are needed to inform the preferred rollout strategy for the stations. Well-to-wheel (WTW) greenhouse gas (GHG) emissions, urban criteria pollutants, energy use, and water use associated with hydrogen and FCVs can be significantly reduced in comparison to the average parc of gasoline vehicles regardless of whether hydrogen is produced and distributed with an emphasis on conventional resources (e.g., natural gas), or on local, renewable resources. An emphasis on local renewable resources to produce hydrogen further reduces emissions, energy use, and water use associated with hydrogen and FCVs compared to an emphasis on conventional resources. All three hydrogen production and distribution scenarios considered in the study meet California's standards for well-to-wheel GHG emissions, and well-to-tank emissions of urban ROG and NO_X. Two of the three scenarios also meet California's standard that 33% of hydrogen must be produced from renewable feedstocks. Overall, systematic planning optimizes both the economic and environmental impact associated with the deployment of hydrogen infrastructure and FCVs.     

Development of a Traceable Fire Alarm System Based on the Conventional Fire Alarm System

Many countries use conventional fire alarm control panels (FACPs) and conventional detectors as fire alarm systems (FASs) because of economic advantages. This study analyzes several problems with conventional FASs and describes an advanced FAS, the traceable FAS, that we developed to solve these problems. The traceable FAS can trace the exact location of a fire, can detect multiple fires that occur simultaneously, and can be used with conventional detectors without disrupting the other detectors operation. The traceable FAS consists of a traceable FACP based on the conventional FACP and a traceable heat detector based on the rate-of-rise spot-type conventional heat detector. The new system offers traceability in addition to all the features of the conventional FAS. The traceable FACP has 40 zones; one zone can connect up to 20 traceable heat detectors. Thus, this FACP can connect up to 800 traceable heat detectors, all of which can detect and trace exact fire locations in sequence. Furthermore, the traceable FACP can be used with both traceable heat detectors and conventional heat detectors in the same zone. Even if one detector (either traceable heat detector or conventional heat detector) detects a fire first, other traceable heat detectors in the same zone can also detect it and display the results on the traceable FACP. Prototypes of the traceable FACP and traceable heat detector (rate-of-rise spot-type) have officially received model approvals for use in South Korea. Conventional FASs can be upgraded to traceable FASs simply by changing to the traceable FACP and traceable heat detectors, without any rewiring.     

Adaptive interactions in shared virtual environments for heterogeneous devices

In this research, we propose a method to adapt the interfaces and interaction processes of heterogeneous devices. The proposed method models the interaction capability of the devices. The interaction is modeled by categorizing elementary actions and measuring its effect in semantic behaviors. With this model, an interaction process can be modified to a given device by changing sequence of elementary actions for each behavior. In the pilot test, we showed the possibility of interaction adaptation for different situations. With the proposed adaptation mechanism, interface and interaction can be modeled for the device independently and can be transferred over different interaction environments. Copyright © 2010 John Wiley & Sons, Ltd.     

Numerical study on flow and heat transfer characteristics of air-jet cooling system

Journal of Mechanical Science and Technology - The present study aims to numerically analyze the cooling characteristics of the air-jet array in designing more efficient air-cooling system. Heat...     

Luminescent properties of Pr doped ZrSiO4 phosphors

Mixtures of ZrO₂, SiO₂, Pr₂O₃, and H₃BO₃ were fired at the temperature of 1150–1350 °C under H₂ atmosphere. A single phase ZrSiO₄:Pr phosphors could be achieved at the firing temperature above 1150 °C. Crystallinity and PL properties strongly depended on the flux amounts, firing temperature, and dopant concentrations. ZrSiO₄:Pr phosphors showed a strong red emission at 615 nm and a weak red emission at 622 nm with an excitation wavelength of 295 and 450 nm, respectively. Two sets of the emission bands and excitation spectra originated from Pr³⁺ ions at Zr and Si sites, respectively.