消音器의 音響減衰에 關한 硏究

윤화중,홍은숙,전관수 충남대학교 자연과학연구소 1989 忠南科學硏究誌 Vol.16 No.2

In order to investigate the acoustical attenuation effects from simple expansion chamber type muffler the following experiments were carried out ; the spectrum analyzer which has 25Hz analyzing frequency intervals was devised. The changing of acoustical attenuation frequency intervals was devised. The changing of acoustical attenuation effects were observed by varying the diameter and the length of the muffler. The diffuser was attached to the muffler in order to decrease the sound pressure levels more and then the acoustical attenuation effects were investigated. The phenomena on the sound wave surface was curvatured and visualized by the diffuser was confirmed in photographic developing of the attenuation wave.

중년여성의 여가생활 경험

허제은(Heo, Je eun),전윤화(Jeon, Yun wha1),태영숙(Tae, Young sook) 고신대학교 전인간호과학연구소 2015 전인간호과학학술지 Vol.7 No.-

Purpose : This study was conducted to understand leisure life experiences in middle-aged women. Methods : In order to do this, I interviewed 8 middle-aged women who actually participate in B metropolitan city and analyzed the result in ‘Colaizzi’s seven specific procedure. Results : The analyses revealed nine subject cluster. Those were ‘Healing in the life’, ‘In addition to switching to another’, ‘Organizing heart in the process of living’, ‘The Fix two hearts swaying’, ‘Show off your own like getting prettier’, ‘Was granted to keep health’, ‘Together enjoy’, ‘Living with thanks’, ‘Take care of the surrounding neighborhood’ and 26 subjects were found. Conclusion : The meaning of Leisure Life Experiences in Middle-aged women was based that will be encouraged to live a life where you can enjoy their leisure in her spare time, travelling as a family, be beautiful, keeping health. These findjngs suggest that It s needed special leisure program for middle-aged women.

An Advanced Quiet-Period Management Scheme for Cognitive Radio Systems

Wha Sook Jeon,Dong Geun Jeong IEEE 2010 IEEE Transactions on Vehicular Technology VT Vol.59 No.3

<P>In cognitive radio (CR) systems, the efficiency of the primary user detection scheme directly affects the system performance. In this paper, we consider CR systems adopting quiet period for primary user detection. Specifically, we propose an enhanced quiet-period management scheme that utilizes two types of sensing intervals and two detection thresholds for energy detection, and can be used with and without feature detection. By using Markov analysis, we derive some performance measures for the system using the proposed scheme, including the channel utilization of CR systems and the detection delay of a primary user. Numerical results show that the proposed scheme heightens the maximum channel utilization of CR users, sustaining the miss-detection probability to be below the predefined value.</P>

Efficient Resource Allocation for OFDMA-Based Two-Hop Relay Systems

Wha Sook Jeon,Sang Soo Jeong,Dong Geun Jeong IEEE 2011 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.60 No.5

<P>We propose an efficient resource allocation scheme for the downlink of orthogonal frequency-division multiple-access (OFDMA)-based two-hop relay systems. The proposed scheme reuses the subchannels within a single cell in the frequency-selective fading environment by allocating a subchannel to multiple links simultaneously. We first formulate a preliminary subchannel allocation problem in consideration of the quality-of-service (QoS) requirements for both real-time traffic and nonreal-time traffic. We also design an efficient postprocessing algorithm that modifies the solution obtained by solving the preliminary problem so that it can be used in practical OFDMA systems. Numerical results show that the proposed scheme can significantly improve system performance.</P>

Collaborative Sensing Management for Cognitive Radio Networks with Reporting Overhead

Wha Sook Jeon,Dong Heon Lee,Dong Geun Jeong IEEE 2013 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.12 No.2

<P>Many cognitive radio (CR) networks adopt the collaborative sensing strategy that combines the sensing results of multiple CR stations, for getting the better primary user (PU) detection performance. In the practical CR networks with collaborative sensing, since a station reports the sensing result to a fusion center through a message, the reporting overhead is not negligible. In this paper, we design a sensing management scheme for CR networks, while taking this reporting overhead into account. First, we formulate an optimization problem that aims at finding the optimal number of sensing stations which collaborate to maximize the PU detection probability for given sensing/reporting time. Then, we propose a heuristic scheme to efficiently select the collaborative sensing stations, without a priori information for the locations of stations. Furthermore, we determine the optimal sensing interval for minimizing the PU detection delay while maintaining the CR channel utilization to a target value, by using a Markov analysis. The simulation results show that the proposed sensing management scheme significantly improves the PU detection performance.</P>

Combined Channel Access and Sensing in Cognitive Radio Slotted-ALOHA Networks

Wha Sook Jeon,Dong Geun Jeong IEEE 2015 IEEE Transactions on Vehicular Technology VT Vol.64 No.5

<P>The cognitive radio slotted-ALOHA (CR S-ALOHA) network is a CR system that consists of two or more secondary users (SUs) utilizing S-ALOHA as the channel access technique. In the CR S-ALOHA network, a sequence of transmission failures can implicate the possibility of primary user (PU) appearance as well as the consecutive collisions between SUs. By exploiting this property, we design a combined channel access and sensing scheme for CR S-ALOHA networks, with which both packet transmission and channel sensing can be controlled together. We analyze the performance of the proposed scheme by formulating a 5-D Markov chain. The numerical results show that the CR S-ALOHA network with the proposed scheme achieves good performance in throughput and delay while protecting the PU properly.</P>

A Hybrid CSMA / CD-Token Bus Protocol for Local Area Networks

Wha Sook Jeon,Chong Sang Kim 대한전자공학회 1997 TENCON 87 - Computers and Communications Technolog Vol.- No.-

Distributed Resource Allocation for Multi-Cell Relay-Aided OFDMA Systems

Wha Sook Jeon,Jeong Ae Han,Dong Geun Jeong IEEE 2014 IEEE TRANSACTIONS ON MOBILE COMPUTING Vol.13 No.9

<P>We propose an efficient resource allocation (RA) scheme for downlink of relay-aided orthogonal frequency division multiple access systems. To mitigate excessive computational complexity of the centralized RA where the base station (BS) is responsible for resource allocation of the entire cell, we take a distributed RA strategy with which each relay station (RS) and BS perform resource allocation for their respective receivers by themselves. The proposed RA scheme is composed of two parts, RS resource allocation (RS-RA) and BS resource allocation (BS-RA). Considering that multiple RSs compete for radio resource in a distributive manner, we design the RS-RA scheme according to noncooperative game framework. The proposed RS-RA scheme aims at allocating less resource to two-hop transmission via RS so that more resource can be used for one-hop (direct) transmission. This RA strategy greatly heightens the system performance. Simulation results show that the proposed RA scheme provides the high cell throughput and the low outage probability. In addition, we devise a heuristic RA scheme that can lower the computational complexity further with much smaller reporting overhead and also suggest an iterative algorithm that can easily implement the proposed RA scheme.</P>

Downlink Radio Resource Partitioning with Fractional Frequency Reuse in Femtocell Networks

Wha Sook Jeon,Juhee Kim,Dong Geun Jeong IEEE 2014 IEEE Transactions on Vehicular Technology VT Vol.63 No.1

<P>Femtocell and fractional frequency reuse (FFR) techniques have received wide attention as the solutions to the data surge problem in mobile networks. With FFR, the frequency band of a macrocell is divided into several frequency partitions (FPs), and the transmission power levels assigned to FPs differ from each other. In this paper, we propose a downlink resource partitioning scheme for two-tier networks, where macrocells adopting FFR are overlaid with the femtocells. With the proposed scheme, every FP is divided into the macro-dedicated, the shared, and the femto-dedicated portions. The ratio of these three portions is different for each FP. We suggest a method to determine a proper ratio of portions in each FP by using an optimization approach. Simulation results show that the proposed scheme maximizes the whole system capacity while satisfying the constraints on the minimum capacity requirement for both macrocell and femtocell.</P>

Optimal Sensing Strategy Against Collision With Primary User in Cognitive Radio Systems

Jeon, Wha Sook,Gu, Junrong,Jeong, Dong Geun IEEE 2015 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.64 No.3

<P>The cognitive radio (CR) system needs to optimally set the sensing period and sensing time, to efficiently utilize the channel while protecting a primary user (PU). The optimal sensing period for maximizing the effective throughput of the CR system depends on not only the on/off pattern of the PU and the sensing error probabilities but also the size of a data packet, the transmission rate, and the forward error correction capability. In this paper, we mathematically derive the optimal sensing period while taking all of these factors into account. On the basis of this optimal period, we design the sensing strategy under which the CR user has the breaks for sensing during a data packet transmission. With the proposed sensing strategy, the CR system can protect the PU very well while achieving the high effective throughput.</P>