Efficient signal enhancement scheme for adaptive antenna arrays in DS-CDMA systems

김경석 University Surrey 2001 해외박사

Adaptive antenna array technology will undoubtedly form a vital part of third generation cellular systems owing to not only confining the radiated energy associated with a mobile to a small volume on the downlink but also reducing the interference due to cochannel users on the uplink. The objective of this thesis is to develop signal enhancement schemes for adaptive antenna arrays for the purpose of enhancing the quality and capacity of direct sequence code division multiple access (DS-CDMA) systems. Firstly, The signal enhancement scheme using a real symmetric array covariance matrix (RSACM) method was proposed. This proposed scheme is composed of a unitary and persymmetric transformation methods. A real symmetric array covariance matrix has the same Toeplitz-plus-Hankel matrix structure that is produced by almost total noiseless data sequence. The second proposed signal enhancement scheme consists of the rotation of signal subspace (RSS) and Toeplitz matrix approximation (TMA) methods. This proposed scheme improved the system performance by reducing the interference-plus-noise effect from the complex array covariance matrix of the pre-correlation received signal vector. The third proposed signal enhancement scheme is a modified linear signal estimator (MLSE) which involves the rank N approximation by reducing total noise eigenvalues (RANE) and TMA methods. The aim of this proposed scheme is to improve the system performance by effectively reducing the interference-plus-noise effect from the post-correlation received signal. Secondly, the computational complexity and the performance for all proposed signal enhancement schemes in this thesis are investigated and compared. The signal enhancement scheme using the RSS+TMA and MLSE methods was also proposed for a multi-rate and multicell DS-CDMA systems. The relative other-cell interference factor was analysed for a multicell condition. Finally, the performance of all proposed signal enhancement schemes is shown to be much better than that of no signal enhancement method under a single cell, multicell, single rate, and multirate conditions.

EVALUATING THE VALUE CHAIN MODEL FOR SERVICE ORGANISATIONAL STRATEGY : INTERNATIONAL HOTELS

최기탁 UNIVERSITY OF SURREY 2000 해외박사

The Role of tourism for regional economic planning : a case study of Harz mountain areas in the process of German unification

최영민 University of Surrey 1995 국내박사

System Reliability-Based Bridge Assessment Using Response Surface Methods

조성일 University of Surrey 2005 해외박사

The objective of the present research was to develop a system reliability-based bridge assessment method for damaged composite bridges. A response surface method was adopted in combination with the nonlinear finite element analyses, which provided a powerful tool for the evaluation of the reliability of a bridge system. Using the method, investigation was made into the effects of corrosion on the reliability of a bridge system. A numerical bridge model used for the present study was developed using an actual composite bridge in the UK. Commercial FE programmes such as ABAQUS and DIANA were used for the development of the model. In order to validate the use of these FE programmes in the present study, simulations on the full-scale bridge test were carried out. Of the three, 40-tonne vehicle loading given in BD 21, the vehicle loading which caused the worst resistance was selected as a reference loading model. In the present study, the failure of the load redistribution system due to punching shear was addressed in detail. It was found that punching shear in the concrete slab may prevent the total collapse of a whole bridge system taking place. This is because the system cannot reach the ultimate state in such a case. It was proposed that such cases be excluded from the evaluation of the failure probability of a whole system. This approach is expected to provide a more rational basis for the evaluation of the reliability of a global bridge system than simply suppressing such failure. The system reliability-based assessment was developed based on the response surface method in combination with the nonlinear finite element analyses. In the present study, reliability analyses were carried out for both intact and damaged bridges. Corrosion on steel girders was simulated by reducing the thickness of the web and the flange. The present study shows that the two-lane loading case governs the total failure probability (reliability) of the present bridge model. In addition, it was found that the traffic loading for the evaluation of load effects has a significant influence on the results. It was also found that the failure of a bridge is most likely to take place due to extremely heavy trucks for the intact state. It seems that this has a close connection to the high uncertainty of the traffic loading. However, the failure is likely to be governed by reduced dimension for severely damaged model. This is because the uncertainty related to the dimension and ultimately the resistance becomes bigger as corrosion proceeds. Results of this research revealed that this assessment methodology is less conservative. This may lead to rational use of a limited resources. It was clearly demonstrated through the reliability analyses that a system reliability-based bridge assessment methodology developed in this research may provide a tool for more rational bridge assessment.

International Hotel Firms Development : Influence on Choices of Entry Mode

홍정화 UNIVERSITY OF SURREY 2001 해외박사

Once firm decides to enter a foreign market, it has to choose a mode of entry, that is, select an institutional arrangement for organizing and conducting international business transactions. Since entry modes have a major impact on the firm's overseas business performance, their selection is regarded as a critical international business decision. Especially, for hotel business mode of entry is most difficult and complex process since hotel investment occur high capital. This research effort was designed to investigate the influential factors in the envirornment of foreign country and international lodging company. Once identified, an attempt was made to determine if there were any relationships which existed between these factors and entry mode choices when these international hotels attempted expansion into new international markets. This effort was initially influenced by the transaction cost analysis (TCA) which insists firm chooses an entry mode which minimise the all costs associated with its integration. The TCA stresses the importance of firm-specific assets, uncertainty variables, and free-riding potential. Certain unique characteristics of lodging business have been considered when selecting the variables for the empirical research. A conceptual framework with 12 hypotheses has been established. However, after data collecting process, 4 variables were eliminated due to data unavailability. A total of 591 international hotel openings are included and ordered probit/logit models are used to analyse the sample. The findings from the research included eight propositions that explain the relationships among the influential variables and entry mode choices in the international hotel firms. Although numerous variables appear to influence a firm's particular choice of entry mode in a given situation, uncertainty variables seem to be particularly important.

The Interaction between soil and large diameter rigid pipe

김시우 University of Surrey 1999 해외박사

본 논문의 목적은 흙과 대구경 강성관의 문제에 있어서 실무지침을 제공하기 위한 numerical modelling을 사용하는데 있다. 또한, 기존설계법에 대한 세심한 검토 및 비평과 함께 대안으로서의 일반적인 설계 및 시공기준들을 제시하였다. 주지하다시피 현재 관습적으로 사용하고 있는 설계법은 대체로 1920년대에 소구경 콘크리트관을 대상으로 개발하였던 Marston-Spangler theory에 기초하고 있으며, 이방법은 실제 사용된 재료의 특성이라든지 구조물의 실형상 및 현장시공방법 등을 제대로 반영하지 않고 있다. 이러한 문제점들을 해결하기 위해서 실제 규격의 현장매설 및 삼점지지하중실험을 통해 얻은 자료들과 함께 지방공학용 유한요소 프로그램 (CRISP)을 사용하여 수치해석을 수행하였다. 다양한 시공여건을 감안한 실무지침을 제시하였고 매설강상관의 거동에 영향을 주는 주요요인에 대한 개략적인 사항들을 정리하면 다음과 같다. 1) 매설관과 주변 흙의 탄성특성 2) 관 주변에 사용할 흙의 타설, 다짐 및 부수적으로 발생하는 체적변화 3) 관 상부의 성토고, 매설조건에 따른 굴착 및 되메움 형상 및 기초부의 지지조건 4) 관 내부에 흐르는 물의 중량 및 압력과 관 외부에 감은 pc강선에 의한 프리스트레스효과 본 연구를 통해, 지중에 매설한 대구경 강성관의 거동에 관한 문제는 다른 강성관의 거동과는 구별하여야 하며, 특히, 프리스트레스 콘크리트관은 일반적인 철근콘크리트관의 거동과 같은 방법으로 취급할 수 없음을 지적 하였다. 결론적으로, 기존설계법을 대구경강성관에 적용할 경우 비경제적인 설계를 초래하는 상당한 결함을 않고 있으므로 이를 극복하기 위해 유한요소법에 의한 설계지침을 추천하며, 이러한 유한요소법은 현장성을 고려한 기술적인 문제점들을 해결할 수 있는 유용한 단서를 제공할 뿐만 아니라 설계시에 불필요한 요소들을 제거하고 보다 우수한 설계를 할 수 있는 지침을 제공한다.

Interference management and code planning in WCDMA UMTS

Ahn, Dae-young University of Surrey 2002 해외박사

Universal Mobile Telecommunications System (UMTS) is one of the third-generation mobile communication systems based on Wideband Code Division Multiple Access (WCDMA). Its multiple access function is accomplished via the Orthogonal Variable Spreading Factor (OVSF) code and uplink and downlink scrambling codes, which are assigned to the users and base stations. In this thesis, Multi-rate signals are transmitted through the Variable Spreading Factor (VSF) scheme where the data rate controls the spreading factor (SF) such that all users spread their signals to the spreading bandwidth regardless of their data rate. This thesis addresses the impact of the usage of the codes on the Multiple Access Interference (MAI) optimisation in WCDMA UMTS. Following the WCDMA UMTS standard, in relation to the codes applied (in this case, it is referred to as the standard OVSF code allocation scheme), it is demonstrated that the average MAI power carries distribution properties and approximately follows the Gaussian form for the Multi-rate service. In the uplink with the short scrambling code, the mean of the average MAI power is larger than that with the long scrambling code. In the downlink, the average MAI power also displays a kind of distribution properties for the Multi-rate services. We propose a novel OVSF code allocation scheme for the Multi-rate service users in the uplink and downlink. In the uplink, for the short and the long scrambling codes, the average MAI power with the proposed OVSF code allocation scheme is lower than that with the standard OVSF code allocation scheme. In addition to the OVSF code allocation scheme, a downlink scrambling code allocation method is also proposed. The downlink scrambling code is referred to as the primary scrambling code and to each base station, different primary scrambling codes are assigned to discriminate each base station. If the proposed OVSF code allocation scheme is applied to the real system, together with the downlink primary scrambling code allocation method, the average MAI power will be reduced and results in the improvement of the WCDMA UMTS performance. Based on the OVSF code and primary scrambling code allocation schemes applied, the reduction of the average MAI power is quantified in the form of the system capacity and the service coverage gains. This shows how the OVSF code and primary scrambling code allocation methods contribute to the capacity increase and coverage extension. In order to reduce the average MAI power among the active users, changing SF scheme is considered in the uplink. In the scheme, until the system reaches the intermediate MAI power limit, only the service with the lower SF (higher data rate) is provided. When the system reaches the intermediate MAI power limit, the number of active users with the lower SF is fixed and as new users come in, the higher SF (lower data rate) is assigned to them until the system reaches the maximum MAI power and provides the required QoS. The scheme allows more users by sacrificing the number of users with lower SF, rather than sticking to the same lower SF for all the active users. As the required QoS for the higher SF service is getting more strict than that with the lower SF service, the increase of the MAI power per higher SF user rises and the total number of active users decreases. The changing SF scheme can be applied to the data only service, in particular, the channel data rate of the service does not affect the requirement of the system performance.

Modernism and postmodernism in contemporary Korean art : implications for art education reform

박정애 University of Surrey 1997 해외박사

1945년 이후 우리나라 미술교육에대한 검토는 한국의 미술교육 과정이 서양의 모더니스트 미학에 기초하고 있음을 밝혀준다. 우리나라의 교육과정을 갱신하기위한 목적으로, 그리고, 한 시대의 미술교육 방법이 당시의 미술 관습과 이론에서 유래된다는 명제를 토대로 이 연구는 한국에서의 미술 교육과정 개혁을 위해 포스트모더니즘이 이에 함축하고 있는 점을 검토하였다. 이 연구는 또한 최근 우리나라 사회 현실을 토대로 자생적으로 일어난 국제화교육의 요구에 부응하고 있는데 국제화 교육의 부상에 내재된 배경이 포스트모더니즘의 다원론 현상이기 때문이다. 질적 방법의 묘사적 성격을 지닌 본 연구는 개념 분석과 에트노그래픽 연구를 활용하였다. 연구의 첫 단계에서는 현대의 교육과정의 체계를 발전시킬 목적으로 서부 유럽과 북아메리카의 문헌분석이 이루어졌다. 그리고 다음 단계에서는 예술가의 미적가치와 믿음, 미술계 (국내와 국제 미술계 모두)의 영향과 그들의 문화적 이문화적 정체성의 관점에서 현대의 한국 미술계를 연구하기위해 21명의 한국 예술가에 대한 인터뷰가 행해졌다. 포스트모더니즘 이론의 개념 분석의 연구는 포스트모더니즘이란 문화 기초이며 그것의 시간 지향은 순환적인 것임을 알려준다. 그것은 대화술 보다는 작은 화술을 선호한다. 포스트모더니즘이 주창하는 인식의 구조는 학습에의 통합적 접근을 유도하는 격자형의 구도이다. 예술가들과의 인터뷰 연구 결과는 다음과 같다. 중진 작가와 원로 작가에 의해 주로 실행되고 있는 한국에서의 미술의 모더니즘은 예술가들이 한국의 전통적 내용과 한국의 형이상학적 이상의 추구 혹은 그 과정이기 때문에 절충적 성격을 띠고 있다. 포스터모던 가치를 받아들이고 있는 젊은 작가들의 작품은 이들의 작품에비해 좀더 표현적이며 양식적으로 또한 절충적이며 현대의 한국 생활에서의 사회 문제의 메시지와 의미를 전하고자 한다. 예술가들은 미술을 자아 표현의 형태이며 도구적으로 기능하며 한 특별한 문화적 환경에서의 상징 작용으로 이해한다. 그들은 또한 미술이 상호 의사소통과 지식 체계의 형태로 간주하고 있다. 이상의 연구 결과는 우리나라 교육과정의 미술 교육의 목표가 자아 표현의 목표 그 이상으로 확대되어야 함을 주창한다. 그리고 현재 감상이라 불리는 것 보다는 미술의 지식과 이해가 좀더 적절한 개념체계임을 시사한다. 또한 현대 미술의 문화적 이문화적 성격을 이해하기 위해서 미술 교수법은 통합적 교육과정이 주창되는 방법으로 문화적 사회적 접근에 기초할 필요가 있다.

Trellis decoding of reed Solomon codes

김수영 University of Surrey 1994 해외박사

리드 솔로몬 코드는 멀티레벨 시클릭 블럭 부호의 한 종류로서 강력한 오류 정정 능력을 가지고 있으며, 대수적인 복호방법이 적용될 경우 복호화 하는데 걸리는 시간이나 계산적인 측면에서 볼 때 상당히 효율적이다. 그러나 길쌈 부호와 비교해보면, 가우시안 채널에서 보통 적당하다고 여겨지는 오류율(10 에서 10사이)에서는 다소 약세를 보인다고 할 수 있다. 이것은 주로 리드 솔 로몬 코드에 연 판정 복호화 방식을 적용하기가 힘들다는데 기인한다고 할 수 있다. 반면에 길쌈 복호기는 연 판정 정보를 쉽게 적용할 수 있기 때문에 경 판정 방법과 비교해 볼때, 큰 어려움 없이 유용한 부호화 이득을 얻을 수 있 다. 비록 길쌈 복호화 방법이 길쌈부호에 주로 사용되어 왔으나, 블럭 보호 에도 사용될 수 있음이 밝혀져 왔다. 본 연구에서는 연 판정 방법을 사용하여 리드 솔로몬 코드를 효율적으로 복 호화 하는 방법을 개발하는데 주력하였다. 먼저 최우 복호법의 하나로써 비 터비(Viterbi) 복호화 방법을 리드 솔로몬 코드에 적용하였다. 그러나 이 방 법은 그 계산의 복잡성 때문에 실지 구현 가능성은 거의 없고 다만 여기에 개 발된 다른 효율적인 복호기의 성능을 가늠하기 위하여 사용되었을 뿐이다. 본 연구에서는 여러가지 계산상 효율적인 길쌈 복호기가 개발 되었으며, 이 것들은 최우 복호기의 성능에 근접하는 성능을 배출하였다. 여러가지 복호기의 성능 검증을 위하여 Importance Sampling 시뮬레이션 방 법을 이용하였으며, 이론적인 성능을 나타내는 수식을 설립하여 성능 검증에 사용하여 일치하는 결과를 얻었다. 개발된 각 복호화 방식에 대해서는 장· 단점을 기술하여, 원하는 부호 방식과 요구되는 오류율에서의 최적 방식을 제시하였다. In this thesis we present a multiple capture model for common spreading cod; ZDMA packet radio systems, in which a finite number of mobile radios cornmu-! nicate with a single central receiver in a slotted random-access mode. Three basid Lpproaches to multiple capture, namely, coherent, differential, and envelope headei, detection, are considered at the central receiver. The problem of multiple header detection is addressed in the presence of multi4 user interference. Our approach is to find good header sequences which can received with small probability of false alarm and a high probability of correc(detection. We use Chernoff bounds to derive the probabilities of false alarm and I missed detection of the header, and then determine a proper randomization timk that minimizes these bounds for several system parameters. Basic equations for the multiple capture probability and throughput performanc4 are derived at the central receiver. At the link-level, we evaluate two key desigd parameters in common spreading code systems, namely, the expected number 0: packets captured at the receiver and the allowable number of simultaneous missions that are supportable at a specified data bit-error rate and probability of packet capture. for the central receivers with coherent, and envelope header, and results from the simulations are compared with theoretical evaluations the multiple capture probability. It is shown that for a threshold approximatio io the probability of data packet success, the multiple capture model significant] .mproves system throughput. A random spreading code assignment scheme for enhancing channel efficient presented in centralized spread-spectrum packet radio networks which emplot multiple capture receiver. Compared to th e common code case, this approac requires modest increase in receiver complexity, but the number of distinct spreadin codes being used is considerably less than the number of radios in the network. The capture and throughput performance of the random assignment scheme is evaluate for various sets of codes, and compared with the theoretical results from the comma code scheme.

Sport and politics in the Republic of Korea

김선종 University of Surrey 2000 해외박사

본연구는 스포츠의 정치, 사회, 경제적 부문과의 연관성에 관하여 조사하였으며 특히 올림픽의 정치, 사회, 경제적 영향력에 대하여 조사하였다. 그리고 스포츠에 대한 정부의 중재에 대하여 살펴보았으며 1960년대이후 한국정부의 스포츠 정책에 대해 살펴보았다. 특히 정부가 어떻게 그리고 왜 스포츠를 장려하였으며 북한과의 스포츠 대화는 어떻게 이루어 졌는지 각 공화국별로 조사하였다. 이러한 관점에서 개발도상국의 스포츠 정책이 어떻게 변화하였는지 살펴보았다.