• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.11
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• pp.1-10
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• 2007

In this paper, we proposed channel estimation scheme for LR-UWB system which has low data rate for WPAN in IEEE 802.15.4a. At the transmitter, we proposed dynamic power level allocation depends on channel condition in specific period when we modulate signal. We use two orthogonal code to estimate channel at once. It can estimate channel more accurately by using two code which shows good correlation characteristic then it can estimate more accurately by spreading gain. Using estimated channel condition, we synchronize symbol timing of transmitted signal. Then determined power allocation scheme and channel information is transmitted to transmiter side. Finally, using these information, transmiter side change the power level of repeated pulse to adopt to channel condition. Simulation is performed under S-V channel for LR-WPAN in IEEE 802.15.4a and we compare the performance with a different type of receiver type. We use coherent and non-coherent method at the receiver. Simulation result shows us at the NLOS channal performance evaluation is greater than that of LOS channel and the result is independent of receiver type. In the NLOS channel, as the signal delay spreading is big, performance evaluation is also increased.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.19-32
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• 2010

Electrolytic reduction technology is essential for the purpose of adopting pyroprocessing into spent oxide fuel as an alternative option in a back-end fuel cycle. Spent fuel consists of various metal oxides, and each metal oxide releases an oxygen element depending on its chemical characteristic during the electrolytic reduction process. In the present work, an electrolytic reduction behavior was estimated for voloxidized spent fuel based on the assumption that each metal-oxygen system is independent and behaves as an ideal solid solution. The electrolytic reduction was considered as a combination of a Li recovery and chemical reactions between the metal oxides such as uranium oxide and the produced Li metal. The calculated result revealed that most of the metal oxides were reduced by the process. It was evaluated that a reduced fraction of lanthanide oxides increased with a decreasing $Li_2O$ concentration. However, most of the lanthanides were expected to be stable in their oxide forms. In addition, a semi-empirical model for describing $U_3O_8$ electrolytic reduction behavior was proposed by considering Li diffusion and a chemical reaction between $U_3O_8$ and Li. Experimental data was used to determine model parameters and, then, the model was applied to calculate the reduction yield with time and to estimate the required time for a 99.9% reduction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.699-705
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• 2015

Aircraft needs high lift-to-drag ratio and weight reduction of the structure for long endurance flight with a small power. Generally high aspect ratio wing is applied to HALE(High Altitude Long Endurance) aircraft. Also high modulus, and high strength CFRP(Carbon Fiber Reinforced Plastic) has been used in primary structures. and thin mylar(membrane material) film has been applied to skin of wing. As a result, wing is more flexible than the other structures. and the stiffness of thin mylar film has an affect on dynamic stability. In this study, the membrane characteristic of mylar film has been simulated using nonlinear gap elements. And equivalent modeling method using shell elements is presented using the nonlinear simulation result. The linear equivalent model has verified using the results of nonlinear membrane method. Proposed linear equivalent shell model has applied to mode analysis for estimate the effect of mylar mechanical properties on natural frequency.