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Chi Xu,Choi. L. Law 보안공학연구지원센터 2009 International Journal of Hybrid Information Techno Vol.2 No.2
UWB signal reception in a ranging system can be accomplished by either coherent receiver or non-coherent receiver. Correlation receiver is a type of coherent receiver while energy detection (ED) receiver falls into the non-coherent category. In this paper, we evaluate their ranging performances using the channel profiles measured in various indoor environments. The effects of important system parameters such as sampling rate and threshold on the ranging performance are also investigated. Results show that ranging accuracy is heavily dependent on the system parameters settings, especially in LOS environment. The correlation receiver requires much higher sampling rate to achieve the same ranging accuracy as compared to ED receiver. The study also shows that regardless of receiver type used, the resultant ranging error for NLOS environments can be described by a unified model. The proposed model is validated by measurement data.
Annealing Effects on Ultra thin MOS Capacitors
Ng, Alvin Chi-hai,Xu, Jun,Xu, J.B.,Cheung, W.Y. The Korean Institute of Electrical and Electronic 2003 전기전자재료 Vol.16 No.9
Silicon oxide with thickness lee than 9 nm is fabricated by tube furnace oxidation. Nitrogen is added to dilute the oxidation rate. Aluminum dots with radius of 0.05 cm are deposited on the oixde. High frequency capacitance-voltage(HF C-V), conductance-voltage(G-V) and current-voltage(I-V) characteristics are measured. Annealing under nitrogen atmosphere is carried out with different time and at different temperature. Densities of the interface states before and after annealing are compared. After annealing, a decrease in density of the interface states is found. Experiments show that 45$0^{\circ}C$ annealing for 30 minutes has the lowest density of the interface states.
Improved strut-and-tie method for 2D RC beam-column joints under monotonic loading
Xu Long,Chi King Lee 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.5
In the previous analytical studies on 2D reinforced concrete (RC) beam-column joints, the modified compression field theory (MCFT) and the strut-and-tie method (STM) are usually employed. In this paper, the limitations of these analytical models for RC joint applications are reviewed. Essentially for predictions of RC joint shear behaviour, the MCFT is not applicable, while the STM can only predict the ultimate shear strength. To eliminate these limitations, an improved STM is derived and applied to some commonly encountered 2D joints, viz., interior and exterior joints, subjected to monotonic loading. Compared with the other STMs, the most attracting novelty of the proposed improved STM is that all critical stages of the shear stress-strain relationships for RC joints can be predicted, which cover the stages characterized by concrete cracking, transverse reinforcement yielding and concrete strut crushing. For validation and demonstration of superiority, the shear stress-strain relationships of interior and exterior RC beam-column joints from published experimental studies are employed and compared with the predictions by the proposed improved STM and other widely-used analytical models, such as the MCFT and STM.