• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.666-675
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• 2008

The IEEE 802.22 standard is being developed with the target of improving the efficiency of spectrum utilization and importing the new wireless communication service. The WRAN standard based on Cognitive Radio is being processed for sharing TV bands. In this paper, the efficient spectrum allocation scheme and the optimal power allocation scheme, Partial Constant Power Water Filling (PCPWF), are proposed to maximize the channel capacity and spectrum efficiency and minimize the interference between adjacent cells. And we maximize the system throughput and fairness by using proposed dynamic cell plan that efficiently allocates channel. The results of the simulations are presented to verify the utilization of our proposed scheme.

• Journal of Communications and Networks
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• v.14 no.1
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• pp.51-62
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• 2012

The exponential growth in wireless services has resulted in an overly crowded spectrum. The current state of spectrum allocation indicates that most usable frequencies have already been occupied. This makes one pessimistic about the feasibility of integrating emerging wireless services such as large-scale sensor networks into the existing communication infrastructure. Cognitive radio is an emerging dynamic spectrum access technology that can be used for flexibly and efficiently achieving open spectrum sharing. Cognitive radio is an intelligent wireless communication system that is aware of its radio environment and that is capable of adapting its operation to statistical variations of the radio frequency. In ad hoc cognitive radio networks, a common control channel (CCC) is usually used for supporting transmission coordination and spectrum-related information exchange. Determining a CCC in distributed networks is a challenging research issue because the spectrum availability at each ad hoc node is quite different and dynamic due to the interference between and coexistence of primary users. In this paper, we propose a novel CCC selection protocol that is implemented in a distributed way according to the appearance patterns of primary systems and connectivity among nodes. The proposed protocol minimizes the possibility of CCC disruption by primary user activities and maximizes node connectivity when the control channel is set up. It also facilitates adaptive recovery of the control channel when the primary user is detected on that channel.

• Journal of the Korean Institute of Gas
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• v.14 no.6
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• pp.44-50
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• 2010

Vibration responses of a centrifugal pump required dynamic analysis for seismic qualification, were calculated by using spectrum analysis, which is known to be very simple compared with time domain analysis. Modal analysis was performed and the results were utilized in the spectrum analysis. The vibration responses calculated from the spectrum analysis were more conservative than those from the time domain analysis, that is, the former can be used as safer in design process. The pump was qualified for the specified seismic service conditions as specified in IEEE 344-1987. The maximum stresses were less than allowable stress limits. Based on the analysis results, it is concluded that the pump meets all the dynamic requirements of the applicable codes, standards, and technical specification.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.160.1-160
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• 2001

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.267-275
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• 2009

This paper presents the behavior of column-removed double-span beams in welded steel moment frames and proposes a simplified nonlinear dynamic analysis method for the preliminary evaluation of progressive collapse potential. The nonlinear finite element analysis and the associated analytical study showed that the column gravity load and the beam span-to-depth ratio govern the maximum dynamic deformation demand of the double-span beams. Based on these results, the concept of a collapse spectrum, which describes the relationship between the gravity load parameter and the maximum chord rotation of the double-span beams, was newly proposed. A procedure for the application of the collapse spectrum to multi-story welded steel moment frames was then suggested. The inelastic dynamic finite element analysis results showed that the proposed method gives satisfactory prediction of the nonlinear progressive collapse behavior of welded steel moment frames.

• Journal of applied mathematics & informatics
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• v.33 no.1_2
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• pp.211-217
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• 2015

A dynamic spectrum access scheme with channel partitioning for secondary handover calls in cognitive radio networks is proposed to reduce forced termination probability due to spectrum handover failure. A continuous-time Markov chain method for evaluating its performance such as blocking probability, forced termination probability, and throughput is presented. Numerical and simulation results are provided to demonstrate the effectiveness of the proposed scheme with channel partitioning.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.7
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• pp.599-611
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• 2016

This paper proposes a cognitive engine platform that enables dynamic spectrum access(DSA) based on a spectrum sharing system for the military tactical network environment. The current military tactical wireless communication system is increasing need to secure a supplementary wireless spectrum to ensure that multiple wireless networks for different weapon systems co-exist, so that tactical wireless communication between the same or different systems can be operated effectively. This paper examined policy development and research activities engaged by the U.S. and European countries on wireless spectrum sharing to secure more spectrum. It also introduces the current status of cognitive engine development, which is the core technology of tactical wireless communication for DSA. In addition, based on the investigation performed into the latest trends, we propose a platform structure for a cognitive engine based on a spectrum sharing method where more frequencies can be added for tactical radio communication, so that DSA can be realized, and wireless networks of different weapon systems can co-exist.

• Journal of KSNVE
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• v.6 no.3
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• pp.317-323
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• 1996

This paper proposes the method of experimental structural dynamic modification of fixture for environmental vibration test control. This method can predict the responses at any points on the fixture utilizing the experimental data, and structural dynamic modification of fixture is made using the predicted responses for the spectra at the specimen attachment points to meet the specified reference spectrum. From the results of controlling the fixture before and after modification by conventional control method and optimal reference spectrum, which has been previously reported by the authors, the proposed method is shown to be an effective one.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.120-124
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• 2017

This paper describes the product of search and rescue system with dynamic model. This spread spectrum system based new standard of COSPAS-SARSAT is results of RF signal generation and transmission. we will test performance evaluation which implement signal process adapting Dynamic model and we will adapt the CAF model using TDOA and FDOA relationship.

• Macromolecular Research
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• v.10 no.2
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• pp.60-66
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• 2002

The morphology, dynamic mechanical behavior and fracture behavior of polyetherimide (PEI)/dicyanate semi-interpenetrating polymer networks (semi-IPNs) with a morphology spectrum were analyzed. To obtain the morphology spectrum, we disported PEI particles in the procured dicyanate resin containing 300 ppm of zinc stearate catalyst. The semi-IPNs exhibited a morphology spectrum, which consisted of nodular spinodal structure, dual-phase morphology, and sea-island type morphology, in the radial direction of each dispersed PEI particle due to the concentration gradient developed by restricted dissolution and diffusion of the PEI particles during the curing process of the dicyanate resin. Analysis of the dynamic mechanical data obtained by the semi-IPNs demonstrated that the transition of the PEI-rich phase was shifted toward higher temperature as well as becoming broader because of the gradient structure. The semi-IPNs with the morphology spectrum showed improved fracture energy of 0.3 kJ/$m^2$, which was 1.4 times that of the IPNS having sea-island type morphology. It was found that the partially introduced nodular structure played a crucial role in the enhancement of the fracture resistance of the semi-IPNs.