• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.62-67
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• 1997

This paper reprdsents a new scheme of neural network control system analysis the robustues of robot manipulator using digital signal processors. Digtal signal processors, DSPs, are micro-processors that are particularly developed for fast numerical computations involving sums and products of variables. Digital version of most advanced control algorithms can be defined as sums and products of measured variables, thus it can be programmed and executed through DSPs. In additions, DSPs are a s fast in computation as most 32-bit micro-processors and yet at a fraction of their prices. These features make DSPs a viable computational tool in digital implementation of sophisticated controllers. Durng past decade it was proposed the well-established theorys for the adaptive control of linear systems, but there exists relatively little general theory for the adaptive control of nonlinear systems. The proposed neuro network control algorithm is one of learning a model based error back-propagation scheme using Lyapunov stability analysis method.

• Journal of Astronomy and Space Sciences
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• 제24권4호
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• pp.261-268
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• 2007

We have studied the temporal variation in the North-South asymmetry of the sunspot area during the period from 1874 to 2007. Though the 9-year periodicity is commonly reported, shorter periodicities is still under study. We employ the cepstrum analysis method to analyze the noisy power spectrum of the North-South asymmetry. We demonstrate that the cleaned power spectrum shows reduction of the spurious back-ground noise level. Some of short period peaks in the power spectrum disappear after deconvolution. It should be, however, pointed out that power spectrum might look less noisy because of a filtering process during deconvolution. We conclude by pointing out that a more sophisticate filtering algorithm is required to produce a precise and reliable periodicity estimate.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권1호
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• pp.16-22
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• 2013

This paper presents the analysis and optimization of air-core permanent magnet linear synchronous motor with overlapping concentrated windings to achieve high thrust density, high thrust per copper losses and low thrust ripple. For the motor design, we adopt equivalent magnetizing current (EMC) method to analyze the magnetic field and give analytical formulae for calculation of motor parameters such as no-load back EMF, dynamic force, thrust density and thrust per copper losses. Further, we proposed a multi-objective optimization by genetic algorithm to search for the optimum parameters. The design optimization is verified by 2-D Finite Element analysis (FEA).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.500-504
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• 1995

A neural network based upon the back propagation algorithm was designed and applied to acoustic power spectra of electrohydraulic total artificial hearts in order to diagnose mechanical failure of devices. The trained network distinguished spectra of the mechanically damaged device from those of the undamaged device with overall success rate of 63%. Moreover, the network correctly classified more than 70% of spectra in the frequency bands of 0-100 Hz and 700-950 Hz. Consequently, the neural network analysis was useful for the diagnosis of mechanical failure of a total artificial heart.

• Structural Engineering and Mechanics
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• 제30권6호
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• pp.679-698
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• 2008

On marine vessels, delicate instruments such as navigation radars are normally mounted on ship masts. However the vibrations at the top of mast where the radar is mounted often cause serious deterioration in radar-tracking resolution. The most serious problem is caused by the rotational vibrations at the top of mast that may be due to wind loading, inertial loading from ship rolling and base excitations induced by the running propeller. This paper presents a method of semi-active vibration control using magneto-rheological (MR) dampers to reduce the rotational vibration of the mast. In the study, the classical optimal control algorithm, the independent modal space control algorithm and the double input - single output fuzzy control algorithm are employed for the vibration control. As the phenomenological model of an MR damper is highly nonlinear, which is difficult to analyse, a back- propagation neural network is trained to emulate the inverse dynamic characteristics of the MR damper in the analysis. The trained neural network gives the required voltage for each MR damper based on the displacement, velocity and control force of the MR damper quickly. Numerical simulations show that the proposed control methods can effectively suppress the rotational vibrations at the top of mast.

• 한국항해항만학회지
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• 제26권2호
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• pp.183-188
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• 2002

컨테이너 물동량 예측은 항만과 항만의 개발에 있어서 매우 중요하다. 일반적으로 이동평균법, 지수평활법, 회귀분석과 같은 통계적인 방법들은 물동량 예측에서 많이 사용되어졌다. 하지만, 컨테이너 물동량 예측에 영향을 주는 여러 가지 요소들을 고려해 보면 다중병렬처리시스템인 신경망을 이용하는 것이 효과적이다. 본 연구는 신경망의 역전파학습알고리즘을 이용하여 컨테이너 활동량을 예측하였다. 신경망을 이용하여 영향력 있는 요소들을 선별하였으며, 선별된 요소들을 이용하여 물동량 예측을 하였다. 또한 제안된 신경망 알고리즘과 통계적인 방법의 예측들을 비교하였다.

• 한국정보통신학회논문지
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• 제12권2호
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• pp.360-368
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• 2008

본 논문에서는 다중 서비스 다중 사용자 OFDMA 시스템의 임의 접근채널에서 차별화된 서 비스 품질을 제공하기 위하여 backoff기반 임의 접근 알고리즘을 제안하고, 임의 접근 채널의 주 자원인 부채널의 수와 PN-코드의 수가 주어진 경우, 제안된 알고리즘의 성능을 각 서비스 클래스 접속 확률의 함수로서, 각 서비스 클래스의 접속 성공 확률, 처리율, 블로킹 확률, 접속 지연관점에서 분석한다. 수치적 분석을 통하여 제안된 backoff 기반 임의 접근 알고리즘이 서로 다른 서비스 클래스의 임의접근 시도들에게 차등한 서비스 품질을 제공할 수 있음을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권2호
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• pp.312-334
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• 2023

In large-scale computing, cloud computing plays an important role by sharing globally-distributed resources. The evolution of cloud has taken place in the development of data centers and numerous servers across the globe. But the cloud information centers incur huge operational costs, consume high electricity and emit tons of dioxides. It is possible for the cloud suppliers to leverage their resources and decrease the consumption of energy through various methods such as dynamic consolidation of Virtual Machines (VMs), by keeping idle nodes in sleep mode and mistreatment of live migration. But the performance may get affected in case of harsh consolidation of VMs. So, it is a desired trait to have associate degree energy-performance exchange without compromising the quality of service while at the same time reducing the power consumption. This research article details a number of novel algorithms that dynamically consolidate the VMs in cloud information centers. The primary objective of the study is to leverage the computing resources to its best and reduce the energy consumption way behind the Service Level Agreement (SLA)drawbacks relevant to CPU load, RAM capacity and information measure. The proposed VM consolidation Algorithm (PVMCA) is contained of four algorithms: over loaded host detection algorithm, VM selection algorithm, VM placement algorithm, and under loading host detection algorithm. PVMCA is dynamic because it uses dynamic thresholds instead of static thresholds values, which makes it suggestion for real, unpredictable workloads common in cloud data centers. Also, the Algorithms are adaptive because it inevitably adjusts its behavior based on the studies of historical data of host resource utilization for any application with diverse workload patterns. Finally, the proposed algorithm is online because the algorithms are achieved run time and make an action in response to each request. The proposed algorithms' efficiency was validated through different simulations of extensive nature. The output analysis depicts the projected algorithms scaled back the energy consumption up to some considerable level besides ensuring proper SLA. On the basis of the project algorithms, the energy consumption got reduced by 22% while there was an improvement observed in SLA up to 80% compared to other benchmark algorithms.

• 대한기계학회논문집A
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• 제29권3호
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• pp.395-402
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• 2005

Recently Multidisciplinary Design Optimization Based on Independent Subspaces (MDOIS), an MDO (multidisciplinary design optimization) algorithm, has been proposed. In this research, an MDO problem is defined for design of a belt integrated seat considering crashworthiness, and MDOIS is applied to solve the problem. The crash model consists of an airbag, a belt integrated seat (BIS), an energy absorbing steering system, and a safety belt. It is found that the current design problem has two disciplines - structural nonlin- ear analysis and occupant analysis. The interdisciplinary relationship between the disciplines is identified and is addressed in the system analysis step in MDOIS. Interdisciplinary variables are belt load and stiffness of the seat, which are determined in system analysis step. The belt load is passed to the structural analysis subspace and stiffness of the seat back frame to the occupant analysis subspace. Determined design vari- ables in each subspace are passed to the system analysis step. In this way, the design process iterates until the convergence criterion is satisfied. As a result of the design, the weight of the BIS and Head Injury Crite- rion (HIC) of an occupant are reduced with specified constraints satisfied at the same time. Since the system analysis cannot be formulated in an explicit form in the current example, an optimization problem is formu - lated to solve the system analysis. The results from MDOIS are discussed.

• 한국방사선학회논문지
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• 제17권4호
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• pp.541-549
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• 2023

본 연구는 CT 촬영 시 금속으로 인해 발생한 금속 인공물 감소를 위한 알고리즘 적용에 따른 영상 화질에 대한 정량적 비교를 하고자 한다. Spectral detected-based CT와 CT ACR 464 팬톰을 이용하여 일반적인 필터보정역투영 알고리즘을 적용한 기준 영상을 10장 획득하고, 동일 팬톰에 금속 인공물을 발생시켜 일반적인 필터보정역투영 알고리즘을 적용한 영상을 10장 획득하였다. 금속 인공물을 발생시켜 획득한 영상의 원시 데이터에 metal artifact reduction 알고리즘, 가상 단일 에너지 알고리즘, metal artifact reduction 알고리즘 적용 후 추가로 가상 단일 에너지 알고리즘을 적용한 영상을 각각 10장씩 획득하였다. 알고리즘 적용에 따른 hounsfield unit 비교를 위해 CT ACR 464 팬톰 module 1에 위치한 폴리에틸렌, 뼈, 아크릴, 공기, 물에 관심영역을 설정하고, 전체 영상 화질 평가를 위해 평균 제곱근 오차, 평균 절대 오차, 신호 대 잡음비, 최대 신호 대 잡음비, 구조적 유사도 지수 지표를 통해 알고리즘 별 비교하였다. 알고리즘 적용 영상 별 hounsfield unit 비교 결과 알고리즘 적용 영상 간 유의한 차이를 보였으며(p < .05), 아크릴을 제외한 관심영역에서 가상 단일 에너지 알고리즘 적용 영상에서 큰 변화를 나타냈다. 영상 화질 평가 지표 결과 metal artifact reduction 알고리즘 적용 영상 화질이 가장 높았으나, 구조적 유사도 지수는 metal artifact reduction 알고리즘 적용 후 추가로 가상 단일 에너지 알고리즘이 동시에 적용된 영상이 가장 높았다. CT 촬영 시 금속 인공물 감소에 metal artifact reduction 알고리즘이 가상 단일 에너지 알고리즘에 비해 효과적이었지만, 양질의 CT 영상 획득을 위해 알고리즘 적용에 따른 이점과 영상 화질 변화를 파악하고 효율적인 활용이 필요하다고 사료된다.