• Journal of KIISE:Information Networking
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• 제35권5호
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• pp.409-414
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• 2008

In mobile ad hoc networks, most of on demand routing protocols such as DSR and AODV do not deal with traffic load during the route discovery procedure. To solve the congestion and achieve load balancing, many protocols have been proposed. However, the existing load balancing schemes has only considered avoiding the congested route in the route discovery procedure or finding an alternative route path during a communication session. To mitigate this problem, we have proposed a new scheme which considers the packet bursting mechanism in congested nodes. The proposed packet bursting scheme, which is originally introduced in IEEE 802.11e QoS specification, is to transmit multiple packets right after channel acquisition. Thus, congested nodes can forward buffered packets promptly and minimize bottleneck situation. Each node begins to transmit packets in normal mode whenever its congested status is dissolved. We also propose two threshold values to define exact overloaded status adaptively; one is interface queue length and the other is buffer occupancy time. Through an experimental simulation study, we have compared and contrasted our protocol with normal on demand routing protocols and showed that the proposed scheme is more efficient and effective especially when network traffic is heavily loaded.

• Journal of the Institute of Electronics Engineers of Korea TC
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• 제42권8호
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• pp.33-40
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• 2005

This paper presents a structure of the searcher using a diversity in array antenna systems operating in the cdma2000 1x signal environments. The new technique exploits the fact that the In-phase and quadrature components of interferers can respectively be viewed as an independent gaussian noise at each antnna element in most practical cdma signal environments. The proposed PN acquisition scheme is a singles-dwell PN acquisition system consisting of two stages, that is, the searching stage and the verification stage. The searching stage independently correlates the receiver multiple signals with PN generator of each antenna element for obtaining the synchronous energy at the entire region. Then, the searching results of each antenna element are non-coherently combinind. The verification stage compares the searching energy with the optimal threshold, which is predesigned in the lock detector, and decides whether the acquisition is successful or fail. In this paper, we analyzed the effect of tile diversity order to determine the mean acquisition time. In general, it is known that the mean acquisition time significantly decrease as the number of antenna elements increases. But, as the diversity order goes up, the enhancement of the performance is saturated. Therefore, to decrease the mean acquisition time of the searcher, we must design the optimal array antenna systems by considering the operating SNR range of the receiver, the probability of detection $P_D$ and that of false alarm $P_{FA}$ . The Performance of the proposed PN acquisition scheme is analyzed in frequency selective Rayleigh fading channels. In this paper, the effect of the number of antenna elements on PN acquisition scheme is shown according to the probability of detection $P_D$ and that of false alarm $P_{FA}$.

• Journal of Biomedical Engineering Research
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• 제16권2호
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• pp.231-238
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• 1995

Tc-99m-MIBI (Sestamibi) myocardial SPECT along with TI-201 tomographic Imaging has demonstrated wide application and high image quality sufficient for the diagnosis of myocardial perfusion defect, which consequently reflects regional myocardial blood flow. The qualitative values of myocardial SPECT with Tc-99m-MIBI as well ds the quantitative cases depend in some degree on the reconstruction techniques of multiple projections. Filtered backprojection (FBP) Is the common standard method for reconstruction rather than the complicated and time-consuming arithmetic methods. In FBP it is known that the distribution of radioactivity in reconstructed transverse slices varies with the selected litter parameters such as cutoff frequencies and order (Butterworth case) The cutoff frequencies used in clinicAl practice partially remove and decrease the true radioactive distribution and alter the pixel counts, which lead to underestimation of true counts in specific myocardial regions. In this study, we have investigated the effect of cutoff frequencies of reconstruction filter on the artifactually induced perfusion defects, which are often demonstrated near inferior and/or inferoseptal cardiac walls due to the intense hepatic uptake of Tc-99m-MIBI. A computerized method for Identifying the relative degree of artifactual perfusion defect and for comparing those degrees along with the relative amount of hepatic uptake to myocardium was developed and patient images were studied to observe the quantitative degree of underestimation of myocardial perfusion, and to propose some reasonable threshold of cutoff frequency in the diagnosis of perfusion defect quantitatively. We concluded that from the quantitative viewpoint cutoff frequencies may be used as high as possible with the sacrifice of homogeneity of image quality, and those frequencies lower than the common 0.3 Wyquist frequency would reveal severe degradation of radioactive distribution near inferior and/or inferoseptal myocardium when applying Butterworth or low pass filter.

• Korean Journal of Remote Sensing
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• 제33권5_1호
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• pp.507-519
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• 2017

The applications of NDVI (Normalized Difference Vegetation Index) as a vegetation index has been widely used to understand vegetation biomass and physiological activities. However, NDVI is not suitable way for monitoring vegetation stress because it is less sensitive to change in physiological state than biomass. PRI (Photochemical Reflectance Index) is well developed to present physiological activities of vegetation, particularly high-light-stress condition, and it has been adopted in several satellites to be launched in the future. Thus, the understanding of PRI performance and the development of analysis method will be necessary. This study aims to interpret the characteristics of light-stress-sensitive PRI in shadow areas and to evaluate the PRI calculated by other wavelengths (i.e., 488.9 nm, 553.6 nm, 646.9 nm, and 668.4 nm) instead of 570 nm that used in original PRI. Using airborne-based hyperspectral image, we found that PRI values were increased in shadow detection due to the reduction of high light induced physiological stress. However, the qualities of both PRI and NDVI data were dramatically decreased when the shadow index (SI) exceeded the threshold (SI<25). In addition, the PRI calculated using by 553.6 nm had best correlation with original PRI. This relationship was improved by multiple regression analysis including reflectances of RED and NIR. These results will be helpful to the understanding of physiological meaning on the application of PRI.

• Proceedings of the Korean Society of Medical Physics Conference
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• 한국의학물리학회 2004년도 제29회 추계학술대회 발표논문집
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• pp.91-95
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• 2004

Several MRI studies have reported reductions in temporal lobe volumes in Alzheimer's disease (AD). Measures have been usually obtained with regions-of-interest (ROI) drawn manually on selected medial and lateral portions of the temporal lobes, with variable choices of anatomical borders across different studies. We used the automated voxel-based morphometry (VBM) approach to investigate gray matter abnormalities over the entire extension of the temporal lobe in 10AD patients (MM5E 22)and 22 healthy controls. Foci of significantly reduced gray matter volume in AD patients were detected in both medial and lateral temporal regions, most significantly in the right and left posterior parahippocarmpal gyri. At a more flexible statistical threshold (P<0.01, uncorrected for multiple comparisons), circumscribed foci of significant gray matter reduction were also detected in the right amygdala/enthorinal cortex, the anterior and posterior borders of the superior temporal gyrus bilaterally, and the anterior portion of the left middle temporal gyrus. These VBM results confirm previous findings of temporal lobe atrophic changes in AD, and suggest that these abnormalities may be confined to specific sites within that lobe, rather than showing a widespread distribution.

• The Korean Journal of Nuclear Medicine
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• 제26권1호
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• pp.40-48
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• 1992

Gated blood pool scan is frequently used for evaluating the change in cardiac function in various cardiac diseases. But resting gated blood pool scan using only LVEF as a cardiac index has been consitently shown to have a low sensitivity, which is about 50%, in detecting coronary artery disease. So it is recommended to compare exercise gated blood pool scan to resting gated blood pool scan. Exercise tests, however, are not always possible, especially in patients with musculoskeletal diseases, recent myocardial infarction and in elderly persons. We studied the usefulness of resting gated blood pool scan using multiple indices in evaluating the patients with coronary artery disease. Studied cases were 185 patients with coronary artery disease (angina pectoris 31, myocardial infarction 154) and 25 normals with low likelihood of coronary artery disease. We used $^{99m}Tc-labeled$ RBC, 740 MBq labeled by in vivo method. The data were evaluated by Micro DELTA computer program. The results were as following: 1) The ejection rates (PER, AER) and filling rates (PFR, AFR) were different in normls and patients with angina pectoris or myocardial infarction. 2) Mean phase angle, ejection rates and filling rates could separate normals from coronary artery disease patients with normal LVEF. 3) Regional ejection fraction was decreased at the site of the infarct in patients with myocardial infarction. 4) Peak filling rate was the the most detectable index in evaluation of cardiac function in patients with coronary artery disease. 5) The threshold at 1.5 standard deviation of normal range was considered as the most reliable cut-off value from ROC analysis. These data suggest that the resting gated blood pool scan has an important role in the evaluation of cardiac functional changes using various cardiac indices in patients with coronary artery disease.

• Journal of KIISE:Computer Systems and Theory
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• 제26권8호
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• pp.918-929
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• 1999

동기식 스트림 암호통신 방식을 사용하는 암호통신에서는 암/복호화 과정 수행시 암호통신 과정에서 발생하는 사이클슬립으로 인해 키수열의 동기이탈 현상이 발생되고 이로 인해 오복호된 데이타를 얻게된다. 이러한 위험성을 감소하기 위한 방안으로 현재까지 암호문에 동기신호와 세션키를 주기적으로 삽입하여 동기를 이루는 주기적인 동기암호 통신방식을 사용하여 왔다. 본 논문에서는 CDMA(Cellular Division Multiple Access) 이동망에서 데이타서비스를 제공할 때 사용되는 점대점 프로토콜의 주소영역의 특성을 이용하여 단위 측정시간 동안 측정된 주소비트 정보와 플래그 패턴의 수신률을 이용하여 문턱 값보다 작은경우 동기신호와 세션키를 전송하는 비주기적인 동기방식을 사용하므로써 종래의 주기적인 동기방식으로 인한 전송효율성 저하와 주기적인 상이한 세션키 발생 및 다음 주기까지의 동기이탈 상태의 지속으로 인한 오류확산 등의 단점을 해결하였다. 제안된 알고리즘을 링크계층의 점대점 프로토콜(Point to Point Protocol)을 사용하는 CDMA 이동망에서 동기식 스트림 암호 통신방식에 적용시 동기이탈율 10-7의 환경에서 주기가 1sec인 주기적인 동기방식에서 요구되는 6.45x107비트에 비해 3.84x105비트가 소요됨으로써 전송율측면에서의 성능향상과 오복호율과 오복호 데이타 비트측면에서 성능향상을 얻었다. Abstract In the cipher system using the synchronous stream cipher system, encryption / decryption cause the synchronization loss (of key arrangement) by cycle slip, then it makes incorrect decrypted data. To lessen the risk, we have used a periodic synchronous cipher system which achieve synchronization at fixed timesteps by inserting synchronization signal and session key. In this paper, we solved the problem(fault) like the transfer efficiency drops by a periodic synchronous method, the periodic generations of different session key, and the incorrectness increases by continuing synchronization loss in next time step. They are achieved by the transfer of a non-periodic synchronous signal which carries synchronous signal and session key when it is less than the threshold value, analyzing the address field of point-to-point protocol, using the receiving rate of address bits information and flag patterns in the decision duration, in providing data services by CDMA mobile network. When the proposed algorithm is applied to the synchronous stream cipher system using point-to-point protocol, which is used data link level in CDMA mobile network, it has advanced the result in Rerror and Derror and in transmission rate, by the use of 3.84$\times$105bits, not 6.45$\times$107bits required in periodic synchronous method, having lsec time step, in slip rate 10-7.

• Journal of the Institute of Electronics Engineers of Korea SC
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• 제47권6호
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• pp.86-96
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• 2010

In this paper, we propose stereo vision-based obstacle detection and vehicle verification methods using U-disparity map and bird's-eye view mapping. First, we extract a road feature using maximum frequent values in each row and column. And we extract obstacle areas on the road using the extracted road feature. To extract obstacle areas exactly we utilize U-disparity map. We can extract obstacle areas exactly on the U-disparity map using threshold value which consists of disparity value and camera parameter. But there are still multiple obstacles in the extracted obstacle areas. Thus, we perform another processing, namely segmentation. We convert the extracted obstacle areas into a bird's-eye view using camera modeling and parameters. We can segment obstacle areas on the bird's-eye view robustly because obstacles are represented on it according to ranges. Finally, we verify the obstacles whether those are vehicles or not using various vehicle features, namely road contacting, constant horizontal length, aspect ratio and texture information. We conduct experiments to prove the performance of our proposed algorithms in real traffic situations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제12권5호
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• pp.11-16
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• 2012

Opportunistic transmit cooperative relaying (OTR) system has been interested for its ability to mitigate the fading in wireless channel without multiple antennas in a small terminal. In OTR system, only the relays that the received Signal-to-noise ratio (SNR) from a source is greater than the threshold transmit to the destination. However, the receiving branches of a destination in a realistic system is fixed, the excess number of signals from the transmit relays does not improve the system performance and consequently increases power consumption. In this paper, we adopt Double Opportunistic Transmit (DOT) cooperative diversity system which controls the average number of transmit relays. Although the average number of the transmit relays can be controlled by adjusting the two thresholds in DOT system, the instantaneous number of transmit relays is varying in fading channel. Thus we propose Maximal Ratio Combining (MRC) or Generalized Selection Combining (GSC) according to the number of the signals from relays at the destination. The outage probability of the proposed system is derived in closed form. The analytical results show that the system performance is improved with the number of the branches. Also it is noticed that when the number of the branches is fixed, the outage probability decreases with the increase of the average SNR of S-R path and R-D path.

• Journal of agricultural medicine and community health
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• 제37권3호
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• pp.156-166
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• 2012

Objectives: This study aimed to identify the relationship among health-related quality of life of the Cheon-nam region elderly with low back pain. Methods: Data were obtained from cross-sectional surveys conducted as a part of the Community Health Survey 2008. The final analysis included data from 7,003 of the 7,070 elderly participants (aged over 65 years), as 67 responses were excluded since they were inaccurate. Data were analyzed with SPSS for Windows (ver. 19.0), using a ${\chi}^2$-test, a t-test, an ANOVA, and multiple liner regression. The significance threshold was set as p<0.05. Results: Factors related to the health-related quality of life of the elderly were low back pain, age, education level, occupation, subjective health status, subjective stress, drinking status, number of chronic diseases, and sleep duration. Further, health-related quality of life was significantly lower in elderly adults with low back pain. Conclusions: In order to improve health-related quality of life of the elderly and the development of the program for the management of low back pain will be needed to determine, it is considered necessary to study more to follow through the various analysis of in the elderly and health-related quality of life.