Earticle

In military applications, mobile ad hoc networks are commonly used due to the autonomy, self-configuration, and flexibility. In addition, spectrum sharing-based communication protocols are being actively considered due to spectrum shortage. We propose a cooperative phase-steering (CPS) technique for a spectrum sharing-based military mobile ad hoc network which consists of a single secondary source (SS) node, multiple secondary relay (SR) nodes, a single secondary destination (SD) node, and multiple primary destination (PD) nodes. In the proposed technique, the SR nodes that succeeded the packet decoding cooperatively adjust the phase of their transmit signals such that the received signals at the SD node from the SR nodes are aligned to a certain angle, while the SR nodes control the transmit power such that the received power at all PD nodes is lower than a certain threshold. Through extensive computer simulations, it is shown that the proposed technique outperforms the conventional cooperative relaying scheme in terms of outage probability.

Spread ALOHA systems that combine the spread spectrum techniques with the ALOHA system (a simple random access protocol without carrier sensing function) have been investigated as Mobile Ad-hoc Network (MANET) protocols. This paper presents the effect of the nonorthogonal Code Shift Keying Spread Spectrum (CSK/SS) ALOHA system on improving the throughput and delay performances of the spread ALOHA system under the MANET environment. The nonorthogonal CSK/SS system, which uses systematically-constructed nonorthogonal sequences, is one of the multilevel modulation systems for the spread spectrum technique with increasing the number of bits per frame. Optimum parameters can be used to obtain the best system performance; thus, this paper gives analytical expressions of the data transmission efficiency and delay property of the proposed scheme as a function of the system parameters under the assumption of no power control. Numerical results show that the nonorthogonal CSK/SS ALOHA system is useful in the MANET environment, compared with the conventional spread ALOHA systems.

본 연구에서는 인공지능 프로그램인 SOM (Self Organizing Maps)를 이용하여 하천의 유량과 수질의 관계를 분석하였으며, 국내 K 연안으로 유입되는 T하천에 대해 과거 4년 자료의 유량 및 수질에 관해 조사를 하였다. 조사기간 중 K 연안으로 유입되는 T하천의 평균 유량 834,850 m3/d, 수온 16.6oC, pH 7.8, DO 10.5mg/l, BOD 1.8mg/l, COD 4.6mg/l, SS 9.0mg/l, T-N 1.356mg/l, T-P 0.071 mg/l를 나타내었다. 시계열에 따른 연도별로 유량 변화에 따라 SS, T-N, T-P 농도가 영향을 많이 받는 것으로 나타났으나 유량 변화와 하천의 전체 수질 항목간의 연관성을 일괄적으로 파악하는 것은 어려웠다. 패턴분석 결과 T하천의 경우 BOD와 COD 및 T-N과 T-P 가 서로 유사한 패턴을 보였으나, 유량과는 일관된 패턴 형태를 찾기가 어려웠다. 그러나, 하천 유량과 SS, pH, DO는 밀접한 관계를 가지고 있으며, SS와는 비슷한 패턴을 pH 및 DO 와는 상반된 패턴을 보이는 것으로 나타났다. T하천의 경우 유량이 높고, DO가 낮을 때 COD, SS, T-N, T-P 및 수온이 높은 패턴을 보인 바, 강우 시 및 여름철에 수질이 악화되는 것을 시사하였다.

The pattern analysis of correlation between the river flow and water quality using an artificial intelligence program, SOM (Self Organizing Maps) technique were analysed in this study. The past four years of data flow and water quality of the T river flowing into the domestic K coast had been collected. Average flow of the T river flowing into the K coast was 834,850 m3/d, average water temperature was 16.6oC, average pH of 7.8, DO of the 10.5 mg/l, BOD of the 1.8 mg/l, COD of the 4.6 mg/l, SS of the 9.0 mg/l, T-N of the 1.356 mg/l, T-P was 0.071 mg/l. Changes in flow rate due to the time series by year appeared to be frequently affected to the SS, T-N, and T-P concentrations, but inter-relationship between overall items of water quality and river flow changes was difficult to identify. SOFMs (Self Organizing Feature Maps) of BOD and COD in T river, and SOFMs of T-N and T-P showed a similar pattern to each other, respectively, but a relationship between flow pattern and them was difficult to find. However, river flow and SS, pH, DO has a close relationship, river flow and SS was analysed to have showed a positive correlation, but the negative correlation between river flow and pH, DO. SOFMs pattern of river flow and DO, and them of COD, SS, TN, TP, and temperature suggested that water quality in T river is deteriorating during rainfall period and summer season.

본 연구는 전통 옻칠 기법을 이용하여 금속표면을 코팅하고, 물성을 평가하여 옻칠의 금속코팅 적용성 여부를 알아보고자 했다. 이를 위해 SS275 금속 시편(60*60 mm)과 원주 생칠을 이용하였다. 또한 칠 횟수(1, 2, 3)와 가열온도(120℃, 150℃)를 변이조건으로 설정하여 총 6개의 시편을 제작하였다. 분석은 색도측정, 접촉각 및 표면에너지 측정, 내약품성 시험, Cross-cut 시험 을 이용하였다. 분석결과 부식성이 개선되고 금속표면에 대한 옻칠의 밀착력이 우수함을 확인 하였다. 접촉각 및 표면에너지는 큰 변화를 보이지 않았다. 또한 색도 역시 큰 차이는 보이지 않았다. 본 연구를 통해 금속 표면에 옻칠이 진행되면 방수성 및 방식성이 좋아짐을 확인하였으 며, 적정한 옻칠 횟수와 가열온도를 확인하였다. 차후 경도와 마모율과 같은 물리적인 특성 연구 와 일정한 두께로 옻을 칠하는 방안을 연구하여 금속의 적용 가능성을 확인하고자 한다.

This study uses traditional lacquer techniques to coat the metal surface and evaluates its physical properties to check the applicability of the lacquer coating. For this purpose, a total of six specimens were produced by setting the variation conditions for the number of times (1, 2, 3) and the heating temperature (120℃, 150℃) using SS275 metal(60*60 mm) and ‘Wonju lacquer’. For analysis, chromaticity measurements, contact angle/surface energy measurements, Chemical Resistance, and cross-cut tests were used. The analysis showed that the corrosivity was improved and the adhesion of lacquer to the metal surface was excellent. There was no significant change in contact angle/surface energy. Also, there was no significant difference in color. Through this study, it was confirmed that lacquer on metal surfaces improves waterproofing and has a anticorrosion effect. We could also check the proper number of lacquer and heating temperature. Additional physical characteristics such as hardness and wear rate should be studied. It is also necessary to study how lacquer can be painted with a certain thickness.

본 논문은 DVB-RCS +M 표준에서 제안된 직접수열기반의 대역확산기술 중 코드 동기 기술에 관한 것이다. 직접수열기반의 대역확산기술은 다중반송파기반의 대역확산기술에 비해 비선형증폭기의 영향을 덜 받으나 수신단에서 코드 동기 시간 측면에서 불리하다. 이러한 어려움을 개선해보고자 초기 코드 포착을 위한 강인한 상관기 구조가 제안되고 코드 추적을 위한 비동기 DLL(Delay Lock Loop)이 제안된다. 본 기법을 바탕으로 평균 포착 시간 등의 결과를 제시하고 샘플 클럭 타이밍 오차에 영향을 받지 않는 2 오버샘플기반의 코드 추적회로의 구조와 결과도 제시한다.

This paper proposes the specific code synchronization technique for DS-SS(Direct Sequence-Spread Spectrum transmission in the DVB-RCS +M standard. DS-SS is better than multi-carrier transmission method under nonlinear channel but imposes a long acquisition time. To improve the synchronization aspect, the robust correlation structure is introduced for acquisition and the nonlinear delay lock loop is done for tracking. MAT(Mean Acquisition Time) performances is shown to validate its superiority. In addition, code tracking and jitter performances are done when code tracking algorithm based on 2 oversamples which is not influenced by sampling clock timing offset and carrier freq. offset is used.

This study compared the effects of two dynamic stretching techniques, namely the contract- relax (C-R) method of proprioceptive neuromuscular facilitation (PNF) and the mobilization with movement (MWM) technique with Mulligan movement, with static stretching (SS) on the gastrocnemius muscle in healthy adult males and females. The average age of the participants was 22.21 years (with a standard deviation of 2.11 years), and a total of 33 participants (14 males and 19 females) voluntarily participated in the study. The participants were divided into three groups: SS, C-R, and MWM, each group consisting of 11 individuals. Outcomes were evaluated through ultrasound, hand-held dynamometer, gastrocnemius muscle pennation angle, muscle tone, and ankle joint dorsiflexion strength and range of motion (ROM) measurements. Measurements were taken before and after applying the SS, C-R, and MWM techniques. Significant differences were observed in gastrocnemius muscle pennation angle, muscle tone, ankle dorsiflexion strength, and ROM before and after the interventions (p < 0.05). When comparing the results between groups, significant differences were found in muscle tone, ankle dorsiflexion strength, and ROM (p < 0.05), while there was no significant difference in the pennation angle (p > 0.05). Therefore, based on the results of this study, it is recommended that for increasing ankle joint strength and ROM while reducing gastrocnemius muscle tone, the application of dynamic stretching techniques such as C-R and MWM is more advisable over using SS as a stretching method.

Neural Network Learning (NNL) is compute-intensive. It often involves a dropout technique which effectively regularizes the network to avoid overfitting. As such, a hardware accelerator for dropout NNL has been proposed; however, the existing method encounters a huge transfer cost between hardware and software. This paper proposes Slightly-Slacked Dropout (SS-Dropout), a novel deterministic dropout technique to address the transfer cost while accelerating the process. Experimental results show that our SS-Dropout technique improves both the usual and dropout NNL accelerator, i.e., 1.55 times speed-up and three order-of-magnitude less transfer cost, respectively.

Spread Spectrum technique transmits the information message (signal) over a bandwidth much larger than its frequency contents or the original bandwidth of information message. In SS technique, a signal (having a specific bandwidth) is spread in the frequency domain and results in a signal having wider bandwidth. Remember, the new resulting bandwidth of a signal is much larger than the minimum required frequency spectrum. In Direct Sequence Spread Spectrum, i.e., DSSS (one of the common techniques of SS) the transmitting information signal is multiplied or combined with the spreading signal (usually Barker code) of wider bandwidth and results in a modulation signal that take up the wide bandwidth of the spreading signal. This new consequential signal is then combined with a carrier signal before transmission. The most important advantage of DSSS technology is the accepted transmission security. In this paper, a novel scheme is proposed that helps out the traditional DSSS system to enhance the transmission security by using random selection of multiple spreading codes in DSSS. In this paper the 11-bit spreading (Barker’s) code is taken under the consideration as the spreading code.

Purpose: The purpose of this study was to assess the effect of the proprioceptive neuromuscular facilitation (PNF) relaxation technique (hold relax; HR, contract relax; CR) and static stretch (SS) on hamstring flexibility and vertical jump performance in healthy adults over a four-week period. Methods: Twenty-four healthy adults volunteered to participate in PNF and static stretch sessions. The subjects were divided into three groups as follows: 8 subjects in the SS group, 8 subjects in the HR group, and 8 subjects in the CR group. In the HR and CR groups, contractions lasted 15 seconds per trial and consisted of 5 sets of 15 seconds of hamstring contraction immediately followed by 15 seconds of passive static hamstring stretching. For the static group, the participants were asked to stretch by hanging a leg over a table for 30 seconds. Subjects in all groups performed the exercises three days per week for 4 weeks. The active straight leg raising (ASLR) test, active knee extension (AKE) test, and vertical jump test were performed before the intervention and after 1, 2, and 4 weeks. Results: The SS, HR, and CR techniques effected positive improvement in hamstring flexibility and vertical jump performances but neither of the stretching methods had any statistically significant different effects according to group, although there were interactions (between group and time) in the ALSR group from 1 week to 2 week and in the AKE test from pretest to 1 week. Conclusion: Based on the results of the current study, SS, HR, and CR were shown to affect hamstring flexibility and vertical jump performance in healthy adults. In particular, it was determined that within a short period, hamstring flexibility could be attributed more to CR than to SS.

Spectrum sensing is a key functionalities of Cognitive radio networks (CRN). There are several methods to improve sensing techniques. In this paper, we present a robust detector using signal to noise ratio (SNR) with adaptive threshold (ADT) scheme in Cognitive Radio Networks (CRN). This technique has two detectors, energy detector (ED)&EDwithADT detector, out of these two detectors only one will perform sensing operation at a time. Selection of detector depends on condition between estimated SNR value (Se) and threshold (γ). Numerical results show that proposed ESNR_ADT scheme optimizes detection performance and outperforms the cyclostationary based sensing method and adaptive spectrum sensing (SS) by 30.5 % and 30 % at – 10 dB signal to noise ratio (SNR) respectively. It is also shown that the proposed scheme yields lesser sensing time than cyclostationary detection and adaptive SS scheme in the order of 5.2 ms and 1.0 ms at - 20 dB SNR respectively.

브랜드는 기업의 핵심적 경영자원으로서 경쟁력 확보와 유지에 결정적 역할을 하는 것으로 알려져 왔다. 그러나 자원 기반 관점 이론과 역동적 능력이론에서는 자원의 단순한 보 유가 기업의 경쟁력과 성장으로 이어지는 것이 아니라, 해당 자원을 조직 내의 다양한 유·무형자원과 결합하여 활용할 때 기업의 경쟁우위 향상에 도움이 된다고 주장하고 있다. 따라 서 본 연구에서는 브랜드 자원이 경영성과에 직접적 영향을 미친다는 이전의 관점에서 벗어나, 브랜드 능력과 경영성과 의 관계를 살펴보는 한편, 브랜드 자원-경영성과 사이에서 브랜드 능력이 매개효과를 가지는지를 분석하였다. 한국 벤 처기업협회에서 실시한 심층설문 자료를 PLS 기법으로 분석 한 결과, 브랜드 능력은 기업의 전반적 경영성과(매출액, 시 장점유율, 미래성장가능성)에 유의적 영향을 미치는 것으로 나타났다. 브랜드 능력이 브랜드 자원과 경영성과의 관계를 유의적으로 매개하는지를 추가적으로 분석한 결과, 회계성 성과지표인 매출액과 시장점유율 사이에는 유의적 매개효과 가 없는 것으로 나타났으나, 비회계성 성과지표인 미래 성장 가능성에 대해서는 완전 매개효과를 보였다. 결론적으로 본 연구는 브랜드 능력에 대한 이해를 향상시키는 한편, 브랜드 자원-브랜드 능력-경영성과로 이어지는 인과관계에 이론적, 실증적 타당성을 더하였다.

It is widely believed that a brand as a critical business resource, can paly a significant role in earning and sustai ning competitive advantages. However, resource-based v iew and dynamic capability theory suggest that acquiring resources does not automatically generate competitivene ss for firms. Rather, when a firm is capable of exploiting a resource by combining with other resources internally resided in the organization, it would help the firm elevate competitiveness and performance. Therefore, going beyo nd the prior view focusing on the direct effect of brand resource on performance, this study is to examine not onl y the relation between brand capability and business perf ormance, but the mediating effect of brand capability bet ween brand and performance. With the secondary data co llected from in-depth questionnaire survey by Korea Ven ture Business Association in 2020, this research employe d PLS (partial least squares) technique to test the reasrc h model. The PLS results show that brnad capability has a positive impact on revenues, market shares, and growt h potentials. Additional tests on the mediating effects sug gest that brand capability did not have a significant medi ating effect between brand accounting performance mea sures such as revenues and market shares. It is also foun d that brand capability has a full mediating effect on non -accounting performance measure, growth potential of a firm. Consequently, this study provides a statistical evide nce that brand capability rather than brand resource has a greater impact on business performance, particularly on growth potentials. Further, the research results not only expand our theoretical understandings of brand capabilit y, but managerial insights on the causal link of brand-br and capability-performance.

Cognitive radio network is one of the prime solutions of band width crises problem. To resolve band width crises firstly we have to sense primary user (PU) licensed signal. To sense PU signal there are various sensing techniques which have been proposed by researchers, but each of them are having some limitations. In this paper we present a two stage detector for spectrum sensing (SS) in cognitive radio (CR). It comprises of a weighted-energy detector (W-ED) and a correlated-generalized likelihood ratio test (C-GLRT). The first stage detects the energy and then if required, the C-GLRT makes the final decision in second stage. Performance of the proposed two stage detector is compared with the existing energy detector (ED), generalized likelihood ratio test (GLRT), and adaptive spectrum Sensing (ASS) detectors. The numerical results show that proposed sensing technique has better detection performance and require less sensing time.

Electrical discharge machining (EDM) is one of the most extensively used nonconventional material removal process. The Taguchi method has been utilized to determine the optimal EDM conditions in several industrial fields. The method was design to optimize only a single performance characteristic. To remove this limitation, the Grey relational theory has been used to resolve the complicated interrelationship among the multiple performance characteristics. In the present study, we attempt to find the optimal machining conditions under which the Material removal rate(MRR) to be maximize and Tool wear rate(TWR) to be minimize. This paper summarizes the Grey relation theory and Taguchi optimization technique in order to optimize the cutting parameters in EDM for SS304. The Taguchi method was used to determine the relations between the machining and Response parameters. GRA was used to investigate the optimal machining parameters, among which the pulse on-time, pulse off-time are found to be the most desirable. Finally optimal machining conditions are pulse on time (50 μs), pulse off time (35 μs), discharge current (12A), and voltage (50V). Experimentation was planned as per Taguchi’s L9 (33) orthogonal array. Analysis of variance (ANOVA) is applied to identify the level of importance of the machining parameters on the multiple performance characteristics considered. Finally confirmation result was carried out to identify the effectiveness of this proposed method.

본 논문은 회색(Gray-scale) 이미지를 기반으로 (2, 2) 비밀 공유(Secret Sharing) 계획을 제안한다. 일반적으로 비밀 공유 방법은 비밀 이미지를 두개이상의 이미지 (그림자 이미지: Shadow Image)로 분배한 후, 그림자 이미지를 참가자(비밀 공유하는 사람)에게 나누어준다. 이 후 참가자들이 비밀을 보기위해 k(k<n) 명이 모여서 이미지 를 투명 용지에 프린트 한 후 이미지를 순서대로 쌓으면 비밀이 잡음이미지 (Noise Image)로 드러난다. 본 논문에서 제안하는 비밀 공유 계획은 데이터 은익과 멀티플렉서 (Multiplexer)를 활용하여 비밀을 두 개의 자연 친화적인 이미지(256 회 색영상)에 분배한다. 비밀을 은닉한 이미지는 두 명의 참가자에게 분배한다. 제안한 비밀 공유방법(Scheme)은 스테가 노그래피(Steganographic)의 장점을 갖고 있기 때문에 공격자의 공격에 쉽게 노출되지 않는다. 실험결과는 제안한 방 법이 확실하며 성능 면에서 높은 성능을 보임을 입증하였다.

We presents a novel (2, 2) secret sharing (SS) scheme for all grayscale images. Generally, a secret image is distribute more than two shadow images, which are dealt out among participants. In order to find out secret image, participants print shadow images to transparent papers. Then, a secret image will appear as stacking transparent papers. The secret sharing scheme in this paper distribute secret image into natural grayscale images using multiplexer and data hiding scheme. After then, two participant have two shadow images respectively. The merit of the proposed scheme is that shadow images have small loss in aspect of the quality with steganographic features. Therefore, the proposed secret sharing scheme in this paper is not easily detected by attackers. The experiment result verified that the proposed scheme, obviously outperforms previous SS schemes.

본 연구에서는 SS41 불림재와 M.E.F. 복합 조직강에 대해서 파괴 역학 파라미터와 X-선 파라미터 사이의 관계를 규명하였다. 피로 균열 진전 실험이 수행되었고, X-선 회절 방법이 피로 파단면에 적용되었다. 피로 파단면을 순차적으로 전해 연마하면서 깊이에 따른 X-선 파라미터(잔류응력, 반가폭)의 변화를 관찰하였다. 최대 소성역 깊이 $w_y$는 SS41 불림재에서는 반가폭의 분포로, M.E.F. 복합 조직강에 대해서는 잔류 응력의 분포로 결정할 수 있었다. 피로 파단면의 깊이 방향에 따른 X-선 파라미터의 분포로부터 $K_{max}$과 $w_y$의 관계식이 실험 데이타로부터 얻어지고, 이 식들으로부터 $K_{max}$은 $w_y$의 측정에 의하여 추정되어질 수 있다.

This study verified the relationship between fracture mechanics parameters and X-ray parameters for normalized SS41 steel with homogeneous crystal structure and M.E.F. dual phase steel(martensite encapsulated islands of ferrite). The fatigue crack propagation test were carried out and X-ray diffraction technique was applied to fatigue fractured surface. The change in X-ray parameters(residual stress, half-value breadth) according to the depth of fatigue fractured surface were investigated. The depth of maximum plastic zone, $w_y$, were determined on the basis of the distribution of the half-value breadth for normalized SS41 steel and that of the residual stress for M.E.F. dual phase steel. $K_{max}$ could be estimated by the measurement of $w_y$.

현재 디지털 이동통신에서 사용되고 있는 DS(direct sequence)/CDMA 방식은 멀티미디어 통신과 같은 고속 데이터 전송에 적용할 경우 다중경로 페이딩 채널하에서 인접심볼간 간섭 및 다중접속간섭이 심해지는 문제점을 갖고 있다. 이러한 문제들을 보완하기 위해, 본 논문에서는 다원 접속 간섭을 억제하는 멀티코드 시스템에 인접 심볼간 간섭을 줄여주는 하이브리드 DS/FH(frequency hopping) SS(spread-spectrum)기술을 접목하여 멀티코드 하이브리드 DS/FH SS 시스템을 고안하였고, 기존의 멀티펀드 시스템이 가지는 문제점을 해결하고자 sub-code 기술을 이용하여 sub-code멀티코드 하이브리드 DS/FS SS 시스템을 제안하였다. 제안한 시스템의 성능을 분석하고자 다양한 채널 환경 하에서 컴퓨터 시뮬레이션을 실시하였다.

The existing mobile communication system called DS/CDMA system, which is serviced widely nowadays, has some problems such as the severe ISI and multiple access interferences under the multi-path fading channel when applied to high-speed data transmission like multimedia transmission. To compensate these problems, we propose a sub-code multi-code hybrid DS/FH (Frequency Hopping) SS (Spread Spectrum) System by combining the multi-code system that restrains the multiple access interference with the hybrid DS/FH SS technique that reduces ISI(Intersymbol Interference) effect for high-speed transmission. Moreover, we implement and propose the sub-code technique to remedy the problems of the generic multi-code system. To verify the performance of the proposed system, the computer simulations are executed under the various channel environments.

전력선 통신은 전력선 채널의 특성이 전력선에 연결된 부하에 의해 변화하는 문제점을 가지고 있다. 이러한 문제점을 극복하기 위한 한 가지 방법으로 대역확산(Spread Spectrum) 방식이 사용되어 왔으며, 그 중 DS/SS (Direct Sequence/Spread Spectrum)은 별다른 Hardware의 추가 없이 구현할 수 있다는 장점을 가지고 있다. DS/SS 시스템에서는 의사잡음(PN code)의 Chip수가 길어질 수 록 에러율이 감소하게 되지만, 저속 전력선 모뎀의 경우 긴 Chip수를 사용할 경우 원하는 데이터 전송 속도를 얻어내기 힘들다. Dual-processing Gain을 가지는 Spread Spectrum 시스템은 전력선 잡음의 주기적 특성을 반영하고자 하였다. 그러나 제안되었던 시스템은 잡음의 형태가 전원전압의 1/4주기를 기준으로 대칭적이라는 가정 하에서 적용되어 실제 여러 형태의 전력선 잡음을 반영하지 못하였다. 따라서 본 논문에서는 여러 잡음의 형태에 따라 PN code의 Chip수가 주기적으로 변경되도록 알고리즘을 구현하여 시스템을 구성 후 시뮬레이션 하였다. 시뮬레이션 시 부하의 잡음을 측정 및 모델링하여 시뮬레이션 하였으며, 구성된 시스템은 여러 전력선 채널의 잡음상황 하에서 실제 데이터 전송 속도를 적게 감소시키면서 에러율은 효과적으로 감소시키는 것을 확인하였다.

The power line communication channel has characteristic variation problems which are caused by load. The spread spectrum technique has been used to overcome these problems. One of that is the direct sequence spread spectrum(DS/SS) system which is not necessary to additional hardwares. The BER of DS/SS system is decreased by longer length of PN code, but data transfer rate is decreases, so data transfer rate is hard to satisfies their own specifications especially in narrowband PLC systems. Spread Spectrum system with Dual-processing Gain tries to reflect cyclic characteristics of power line noise. But that system assumes that shapes of power line channel are symmetrical with respect to the 1/4 point of main frequency(60Hz in Korea), therefore cannot achieves various shapes of real power line noise. Thus in this paper, noise adaptive DS/SS system which PN code is changed by noise levels for various channel noises is proposed and simulated. The different kinds of noises are modeled and measured for simulation, the proposed system is verified that has lower data transfer rate and lower error rate than conventional system by simulation results.

CT 시험편을 사용하여 평면응력 파괴인성치를 산정하는 간단하고 새로운 방법론을 제안하였다. 평면응력 조건하의 균열선단에서 발생하는 좌굴을 방지하는 판을 부착하여 SS304와 SS316의 평면응력 파괴인성치를 정확하게 결정하였다. SS304와 SS316의 피로균열 전파거동이 피로하중 주파수에 미치는 영향을 영상해석법(LAT)을 사용하여 규명하였다.

A simple and relatively new experimental method is proposed to estimate the plane stress fracture toughness by using compact tension (CT) specimen. The anti-buckling plates (fabricated to prevent the buckling caused by the 45 plastic yielding around crack tip under the plane stress condition) help to determine the relatively accurate plane stress fracture toughness of two stainless steels (SS304 and SS316). The fatigue crack propagation behavior of two stainless steels under two different loading conditions such as 10Hz and 5Hz frequency fatigue loadings was investigated by using image analysis technique (IAT) which renders several technical advantages over various conventional measuring methods. It was found that the IAT could be used to estimate fatigue crack lengths more effectively. Furthermore, it was suggested that we might control the measuring time interval for fatigue crack propagation by nearly automatically controlled technical process with the help of IAT.

본 논문에서는 이미지 데이터의 저작권 보호를 위해 워터마크 삽입시 워터마크 영상에 DM-SS 기법을 적용하고 DM-SS 방식에서의 Burst성 에러에 강인한 Reed-Solomon 부호화를 적용하여 워터마크 복원에 대한 성능 개선을 하였다. 그리고 영상에 대한 외부 공격으로는 OFDM/QPSK 전송 시스템을 이용하여 전송 시 생기는 여러 가지 요인을 고려하였다.

In this paper, we propose OFDM/QPSK technique for copyright protection of image data to insert watermark. And, we improve performance of restoration watermark by Reed-Solomon coding that robust burst error. In here, we consider several factors about external effect of image over OFDM/QPSK transmission system.

본 논문은 현재 IEEE 802.11연구 그룹의 기본 시스템 중에 하나인 주파수 대역 확산 LAN을 통하여 개선된 형태의 기술과 서비스를 제공하는 무선 LAN을 실현하는 것이 목적이고 직접 확산 변조에 의한 SS방식을 이용한 주파수 대역 확산 LAN의 구현을 위해 무선 LAN의 하드웨어를 설계 및 제작하고 임의의 스테이션간의 데 이타 전송을 보장하기 위한 CSMA 소프트웨어 프로그램과 대역통과 필 타를 설계하였다. 이 시스템을 사용하여 PC 무선LAN을 설치할 수 있다.

In this paper. we aim at accomplishment of wireless LAN system providing more advanced skills and services by realizing frequency band spread LAN that Is one of the systems on the basis of present IEEE 802.11 standard system. Including BPF. we realized hardware of wireless LAN and CSMA software program. Using this system, we can establish the PC wireless LAN.