• 전기전자학회논문지
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• 제26권1호
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• pp.67-76
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• 2022

In this paper, we propose a new algorithm to improve the accuracy of the Wi-Fi access point (AP) positioning technique. The proposed algorithm based on evaluating the trustworthiness of the signal strength quality of each measurement node is superior to other existing AP positioning algorithms, such as the centroid, weighted centroid, multilateration, and radio distance ratio methods, owing to advantages such as reduction of distance errors during positioning, reduction of complexity, and ease of implementation. To validate the performance of the proposed algorithm, we conducted experiments in a complex indoor environment with multiple walls and obstacles, multiple office rooms, corridors, and lobby, and measured the corresponding AP signal strength value at several specific points based on their coordinates. Using the proposed algorithm, we can obtain more accurate positioning results of the APs for use in research or industrial applications, such as finding rogue APs, creating radio maps, or estimating the radio frequency propagation properties in an area.

• Smart Structures and Systems
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• 제10권4_5호
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• pp.313-329
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• 2012

A challenging issue in design and implementation of an effective structural health monitoring (SHM) system is to determine where a number of sensors are properly installed. In this paper, research on the optimal sensor placement (OSP) is carried out on the Canton Tower (formerly named Guangzhou New Television Tower) of 610 m high. To avoid the intensive computationally-demanding problem caused by tens of thousands of degrees of freedom (DOFs) involved in the dynamic analysis, the three dimension finite element (FE) model of the Canton Tower is first simplified to a system with less DOFs. Considering that the sensors can be physically arranged only in the translational DOFs of the structure, but not in the rotational DOFs, a new method of taking the horizontal DOF as the master DOF and rotational DOF as the slave DOF, and reducing the slave DOF by model reduction is proposed. The reduced model is obtained by IIRS method and compared with the models reduced by Guyan, Kuhar, and IRS methods. Finally, the OSP of the Canton Tower is obtained by a kind of dual-structure coding based generalized genetic algorithm (GGA).

• 전자공학회논문지SC
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• 제39권1호
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• pp.33-41
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• 2002

본 논문에서는 기존의 주파수하중 균형절단 기법과 주파수하중 한켈노옴 근사화 기법에 비하여 더 작은 H∞ 하중 축소오차를 가지는 새로운 알고리듬을 제시한다. 제시한 알고리듬은 제한 실 보조정리로부터 반복적인 두 단계의 선형행렬부등식 형태로 유도한다. 또한 제안한 알고리듬을 성능보장을 위한 제어기 차수축소기법에 적용한다. 수치적 예를 통하여 제안한 알고리듬의 타당성을 보이고 기존의 모델 차수축소기법과 비교 분석하며 HIMAT(highly maneuverable aircraft technology) 시스템의 예를 통하여 성능보장을 위한 제어기 차수축소 기법에 적용할 수 있음을 보인다.

• 대한전자공학회논문지SD
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• 제41권4호
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• pp.57-66
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• 2004

본 논문에서는 RNS(residue number systems) 몽고메리 모듈라 곱셈기 기반의 2,048 비트 RSA 설계를 제안한다. RNS는 긴 워드에 대한 모듈라 연산을 짧은 워드로 분할하여 고속 병렬 모듈라 연산을 처리하는 시스템으로써 본 논문에서는 RNS 몽고메리 모듈라 곱셈 연산을 위해 Wallace 트리 모듈라 곱셈기 기반의 Montgomery reduction method(MRM)［1］와 33개의 64 비트 RNS base 를 도입하였다. 또한, 고속 RNS 모듈라 곱셈 연산을 위해 Chinese remainder theorem(CRT)［2］기반의 개선된 base extension 알고리즘을 제안한다. 본 논문에서 제시한 RNS 기반의 2,048 비트 RSA는 삼성 0.35㎛ 공정을 사용하여 기능을 검증하였으며 100㎒에서 2.53㎳ 연산 속도 결과를 얻었다.

• 한국위성정보통신학회논문지
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• 제3권2호
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• pp.48-53
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• 2008

In the future, satellite communication systems, such as ISDB in Japan and DVB in Europe, are required to support higher transmission date rate for providing multimedia services including HDTV, high rate data communication etc. Considering the effectiveness of OFDM technique in efficient usage of frequency bandwidth and its robustness to the multi-path fading, several OFDM based standards have been proposed for satellite communication. However, the problem of high Peak to Average Power Ratio is one of the main obstacles for the implementation of OFDM based system. Many PAPR reduction schemes have been proposed for OFDM systems. Among these, the partial transmit sequences (PTS) is attractive as they obtain better PAPR property by modifying OFDM signals without distortion. In this paper, considering the complexity issue, we present a simplified minimum maximum (minimax) criterion and Sub-Optimal PTS algorithm to optimize the phase factor. This algorithm can be dynamically made tradeoff`f between performance and complexity on demand. In addition, we integrate guided scrambling (GS) with this method. Simulation in multiple antenna based OFDM system proves that the proposed Hybrid schemes can get much more PAPR reduction and do not require transmission of side information (SI). Thus it is helpful when implementing OFDM technique in satellite communication system.

• Journal of Construction Engineering and Project Management
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• 제5권2호
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• pp.24-34
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• 2015

The complexity arises in defining the construction quality due to its perception, based on inherent market conditions and their requirements, the diversified stakeholders itself and their desired output. A quantitative survey based approach was adopted in this constructive study. A questionnaire based survey was conducted, for the assessment of construction quality perception and expectations in the context of quality improvement technique. The survey feedback of professionals, from the leading construction organizations/companies of Pakistan were analyzed. The financial capacity, organizational structure, and construction experience of the construction firms formed basis for their selection. After statistical analysis of survey feedback it was found reliable and valid for the inferential purpose to the target population of construction professionals. The quality perception was found to be project scope oriented, considered as an excess cost for a construction project and keeping the rework minimum by qualifying the required quality tests, keeping the defects minimum by ensuring the specifications of supplied material. Any quality improvement technique was expected to address the financial aspects of the construction project for the employer and contractor, by increasing the profitability through reduction in overall cost, reduction in time, reduction in defects and improving the productivity in a construction project. The study is beneficial for the construction professionals to assess the prevailing construction quality perception and the expectations from implementation of any quality improvement technique in construction projects.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1128-1133
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• 2003

A gas driven heat pump (GHP) core design comprises internal combustion engine, compressors incorporated to a cooling/heating system, rubber mountings and belt transmissions. Main excitation farces are generated by an engine, compressors themselves and belt fluctuation. It leads to high vibration level of the mount that can cause damage of GHP elements. Therefore an appropriate design of the mounting system is crucial in terms of reliability and vibration reduction. In this paper oscillation of the engine mount is explored both experimentally and analytically. Experimental analysis of natural frequencies and operational frequency response of the GHP engine mounting system enables to create simplified model for numerical and analytical investigations. It is worked out criteria f3r vibration abatement of the isolated structure. Influence of bracket stiffness between engine and compressors, suspension locations and damper performance is investigated. Ways to reduce excitation forces and improve dynamic performance of the engine-compressor mounting system are considered from these analyses. Implementation of the proposed approach permits to choose appropriate rubber mountings and their location as well as joining elements design A phase matching technique can be employed to control forces from main exciters. It enables to changing vibration response of the structure by control of natural modes contribution. Proposed changes lead to significant vibration reduction and can be easily utilized in engineering practice.

• 한국정보처리학회논문지
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• 제4권3호
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• pp.846-858
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• 1997

순수 함수형 프라그래밍 언어는 명확한 어의와 많은 특성에도 불구하고 상태의 표현이 어렵다는 문제점을 가지고 있다 이와 같은 문제로 인힝순수 함수형 언어에 상태를 표현 하기 위한 많은 연구가 진행되었으나 형시스템이나 감축규칙이 복잡하기 때문에 구현이 어렵다는 문제점이 발생된다. 따라서 효율적인 구현기 위해 감축규칙을 단순화시키고 상태를 효율적으로 관리할 수 있는 방안이 요구 된다. 본 논문에서는 순수 함수형 언어 의 성질을 침해함이 없이 상태를 표현할 수 있으며 감축규칙을 단순화 시킨 함수형 언어의 수행모델st-계산을 제안하고, 제안된 모델이 church-roser 정리를 만족함을 증명 하였다. 제안된 방법을 통해 구문구조의 표현력을 높일 수 있었으며, 감축규칙을 단순화 함으로써 구현이 용이할 것으로 기대된다.

• Communications for Statistical Applications and Methods
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• 제23권3호
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• pp.259-268
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• 2016

High-dimensional survival data with large numbers of predictors has become more common. The analysis of such data can be facilitated if the dimensions of predictors are adequately reduced. Recent studies show that a method called sliced inverse regression (SIR) is an effective dimension reduction tool in high-dimensional survival regression. However, it faces incapability in implementation due to a double categorization procedure. This problem can be overcome in the right-censoring type by transforming the observed survival time and censoring status into a single variable. This provides more flexibility in the categorization, so the applicability of SIR can be enhanced. Numerical studies show that the proposed transforming approach is equally good to (or even better) than the usual SIR application in both balanced and highly-unbalanced censoring status. The real data example also confirms its practical usefulness, so the proposed approach should be an effective and valuable addition to usual statistical practitioners.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3803-3810
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• 2022

OpenMC is a community-driven open-source Monte Carlo neutron and photon transport simulation code. The Weight Window Mesh (WWM) function and an automatic Global Variance Reduction (GVR) method was recently developed and implemented in a developmental branch of OpenMC. This WWM function and GVR method broaden OpenMC's usage in general purposes deep penetration shielding calculations. However, the Local Variance Reduction (LVR) method, which suits the source-detector problem, is still missing in OpenMC. In this work, the Weight Window Generator (WWG) function has been developed and benchmarked for the same branch. This WWG function allows OpenMC to generate the WWM for the source-detector problem on its own. Single-material cases with varying shielding and sources were used to benchmark the WWG function and investigate how to set up the particle histories utilized in WWG-run and WWM-run. Results show that there is a maximum improvement of WWM generated by WWG. Based on the above results, instructions on determining the particle histories utilized in WWG-run and WWM-run for optimal computation efficiency are given and tested with a few multi-material cases. These benchmarks demonstrate the ability of the OpenMC WWG function and the above instructions for the source-detector problem. This developmental branch will be released and merged into the main distribution in the future.