• Proceedings of the KIEE Conference
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1054-1056
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• 2003

The slotless Permanent-Magnet Linear Synchronous Motors (PMLSM) have been developed for factory automation, transportation applications, wafer steppers, conveyance system, and so on. The current analysis and design are treated in air-cored PMLSM. This paper presents a design and analysis solutions for the general class of iron-cored Permanent magnet Linear Synchronous motor (PMLSM). In our design and analysis, rotor consisting of permanent magnets and slot less iron-cored coil stator are treated in a uniform way via vector potiential. For one such motor structure we give analytical formulas for its magnetic field, opitimal permanent magnet and winding coil thickness, trust force. We also provide comparisons of three types in Halbach, vertical, and horizontal magnet array.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제66권12호
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• pp.1895-1898
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• 2017

This paper discusses methods for the torque ripple and noise reduction of DC motors for automotive air-conditioning based on electromagnetic field analysis. The target of the motor is a blower motor, and to reduce cogging torque and the torque ripple, the optimum model was selected by deforming the brush or commutator shape. In addition, to reduce the cogging torque, the model design was carried out by applying the skew method and the magnetization method of a magnet to the rotor. For optimization, the shape, material, and drive system of the motor were selected using an electromagnetic field as the analysis tool, and the method of reducing the cogging torque was applied to 4-pole, 12- and 13-slot motors considering the mechanical part. Lastly, this paper confirmed thatthemethod, which proposed how much noise, cogging torque, and vibration are reduced, improves through practical analysis.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.756-758
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• 2010

Fixed frame size is used in the RFID system with the frame-based slot ALOHA algorithm. Therefore, it is anticipated that the tag identification performances will highly depend on the number of tags within the reader's identification range and the frame size. In this paper, we propose a tag number estimation scheme and analyze the performance with the computer simulations. The proposed scheme is based on the status of slots that the tags respond during a query round as well as the probabilistic calculations.

• Journal of Information Processing Systems
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• 제17권3호
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• pp.615-629
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• 2021

With the development of mobile edge computing, how to utilize the computing power of edge computing to effectively and efficiently offload data and to compute offloading is of great research value. This paper studies the computation offloading problem of multi-user and multi-server in mobile edge computing. Firstly, in order to minimize system energy consumption, the problem is modeled by considering the joint optimization of the offloading strategy and the wireless and computing resource allocation in a multi-user and multi-server scenario. Additionally, this paper explores the computation offloading scheme to optimize the overall cost. As the centralized optimization method is an NP problem, the game method is used to achieve effective computation offloading in a distributed manner. The decision problem of distributed computation offloading between the mobile equipment is modeled as a multi-user computation offloading game. There is a Nash equilibrium in this game, and it can be achieved by a limited number of iterations. Then, we propose a distributed computation offloading algorithm, which first calculates offloading weights, and then distributedly iterates by the time slot to update the computation offloading decision. Finally, the algorithm is verified by simulation experiments. Simulation results show that our proposed algorithm can achieve the balance by a limited number of iterations. At the same time, the algorithm outperforms several other advanced computation offloading algorithms in terms of the number of users and overall overheads for beneficial decision-making.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4364-4384
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• 2021

The dynamic network state and the mobility of the terminals make the service function chain (SFC) orchestration mechanisms based on static and deterministic assumptions hard to be applied in SDN/NFV mobile edge computing networks. Designing dynamic and online SFC orchestration mechanism can greatly improve the execution efficiency of compute-intensive and resource-hungry applications in mobile edge computing networks. In order to increase the overall profit of service provider and reduce the resource cost, the system running time is divided into a sequence of time slots and a dynamic orchestration scheme based on an improved column generation algorithm is proposed in each slot. Firstly, the SFC dynamic orchestration problem is formulated as an integer linear programming (ILP) model based on layered graph. Then, in order to reduce the computation costs, a column generation model is used to simplify the ILP model. Finally, a two-stage heuristic algorithm based on greedy strategy is proposed. Four metrics are defined and the performance of the proposed algorithm is evaluated based on simulation. The results show that our proposal significantly provides more than 30% reduction of run time and about 12% improvement in service deployment success ratio compared to the Viterbi algorithm based mechanism.

• Journal of Broadcast Engineering
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• 제27권7호
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• pp.999-1010
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• 2022

The increase in vehicle purchases worldwide is having a very significant impact on the availability of parking spaces. In particular, since it is difficult to secure a parking space in an urban area, it may be of great help to the driver to check vehicle parking information in advance. However, the current parking lot information is still operated semi-manually, such as notifications. Therefore, in this study, we propose a system for detecting a parking space using a relatively simple image processing method based on an image taken from the sky and evaluate its performance. The proposed method first converts the captured RGB image into a black-and-white binary image. This is to simplify the calculation for detection using discrete information. Next, a morphological operation is applied to increase the clarity of the binary image, and a template mask in the form of a bounding box indicating a parking space is applied to check the parking state. Twelve image samples and 2181 total of test, were used for the experiment, and a threshold of 40% was used to detect each parking space. The experimental results showed that information on the availability of parking spaces for parking users was provided with an accuracy of 95%. Although the number of experimental images is somewhat insufficient to address the generality of accuracy, it is possible to confirm the possibility of parking space detection with a simple image processing method.

• Proceedings of the Korea Information Processing Society Conference
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• 한국정보처리학회 2010년도 춘계학술발표대회
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• pp.782-785
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• 2010

본 논문은 연속된 음성 신호를 전송로 상에 전송하기 위해 음성 신호를 G.711 표준 권고인 PCM으로 다중화한 후 고정 타임슬롯을 배정하여 전송하는 시스템에서 PCM 화된 디지털 음성 데이터를 실시간으로 암호화하여 전송하는 스트림 암호화 기법에 관한 것이다. 실시간으로 처리되는 음성 데이터의 암호화 시에는 하드웨어 방식이 적합한 데, 본 논문에서는 고정 타임슬롯을 배정받는 음성 데이터의 실시간 암호화 기법에 관한 것이다. 일반적으로 아날로그 음성 신호 코딩 시에 국내에서는 북미 방식인 ${\mu}-law$ 코딩 기법을 적용하는 데 이는 표본화한 음성 데이터를 양자화전에 압축하고 복호화 후 신장하는 비선형 양자화 기법을 적용하는 것으로 표본화된 값을 8 비트의 PCM 데이터로 변화하여 E1(2.048Mbps) 급 속도로 전송한다. 본 논문에서는 PCM 전송로 상에 전송되기 전의 직렬 입력 데이터를 암호화 장치를 거쳐 해당 타임슬롯에 해당하는 8 비트의 데이터를 실시간으로 암호화하여 전송로 상으로 전송하고 역으로 수신 단에서는 PCM 전송로를 거친 직렬 입력 데이터를 암호화된 타임슬롯을 판별하여 해당 타임슬롯의 데이터를 복호화하여 원래 데이터를 복원한다. 본 논문에서는 고정 타임슬롯을 배정받은 PCM 데이터를 암호화하여 전송한 후 수신 단에서 복호화 과정을 거친 후 타임슬롯 단위로 데이터 암호화/복호화가 가능함을 보여준다.

• Progress in Superconductivity and Cryogenics
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• 제8권4호
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• pp.12-14
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• 2006

YBCO coated conductors have been fabricated by the reel-to-reel processing using TFA-MOD method. In this work, the fluorine-free Y & Cu precursor solution was synthesized to shorten the calcining time by reducing the evolution of HF gas, thus the meter-long YBCO precursor films can be made within few hours by the continuous slot-die coating & calcination step using the F-free Y & Cu precursor solution. The annealing step was followed to make the YBCO films by the reel-to-reel method with the vertical gas flow system onto the moving tape. To increase the growth rate of the YBCO films by enhancing the removal of HF gas, the low total pressure was adopted in the annealing processing. And the water partial pressure and the oxygen partial pressure were varied to optimize the growth conditions of the MOD-YBCO films on the buffered metal tape. FE-SEM and XRD were used to investigate the surface morphologies and the texture of the meter-long YBCO films. The end-to-end critical current $(I_c)$ of 63A/cm-width and the critical current density $(J_c)$of $0.9MA/cm^2$ with the thickness of $0.7{\mu}m$ were obtained in the 0.42m long coated conductor.

• Annual Conference on Human and Language Technology
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• 한국정보과학회언어공학연구회 2021년도 제33회 한글 및 한국어 정보처리 학술대회
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• pp.353-360
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• 2021

음성 대화 시스템에서는 사용자가 잘못된 슬롯명을 말하거나 음성인식 오류가 발생해 사용자의 의도에 맞지 않는 응답을 하는 경우가 있다. 이러한 문제를 해결하고자 말뭉치나 사전 데이터를 활용한 질의 교정 방법들이 제안되지만, 이는 지속적으로 사람이 개입하여 데이터를 주입해야하는 한계가 있다. 본 논문에서는 축적된 로그 데이터를 활용하여 사람의 개입 없이 음악 재생에 필요한 슬롯을 교정하는 자기 학습(Self-learning) 기반의 모델을 제안한다. 이 모델은 사용자가 특정 음악을 재생하고자 유사한 질의를 반복하는 상황을 이용하여 비지도 학습 기반으로 학습하고 음악 재생에 실패한 슬롯을 교정한다. 그리고, 학습한 모델 결과의 정확도에 대한 불확실성을 해소하기 위해 질의 슬롯 관계 유사도 모델을 이용하여 교정 결과에 대한 검증을 하고 슬롯 교정 결과에 대한 안정성을 보장한다. 모델 학습을 위한 데이터셋은 사용자가 연속으로 질의한 세션 데이터로부터 추출하며, 음악 재생 슬롯 세션 데이터와 질의 슬롯 관계 유사도 데이터를 각각 구축하여 슬롯 교정 모델과 질의 슬롯 관계 유사도 모델을 학습한다. 교정된 슬롯을 분석한 결과 발음 정보가 유사한 슬롯 뿐만 아니라 의미적인 관계가 있는 슬롯으로도 교정하여 사전 기반 방식보다 다양한 유형의 교정이 가능한 것을 보였다. 3 개월 간 수집된 로그 데이터로 학습한 음악 재생 슬롯 교정 모델은 일주일 동안 반복한 고유 질의 기준, 음악 재생 실패의 12%를 개선하는 성능을 보였다.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.1273-1278
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• 2005

In this thesis, a 2 stage 6-pole bandpass filter(BPF) is designed and implemented by using triple-mode cavity for satellite payload system. The BPF has a 100MHz bandwidth at the center frequency of 14.5GHz(Ku-band) and the response of the filter is the Chebyshev function. The cavity filter uses two orthogonal $TE_{113}$ modes and one $TM_{012}$ mode. The coupling between the adjacent cavityes(intercavity coupling) results in a Chebyshev response and is accomplished by only H-filed component of TE modes. The size and location of intercavity slot is determined by the coupling equation from E- and H-field of TE and TM resonant modes in circular cavity. The 2-stage 6-pole triple-mode cavity BPF has the insertion loss of 2.4dB and the reflection loss of 15dB in the passband. The triple-mode BPF proposed in this thesis can be used as channel filters for satellite payload system and can minimize filter assembly in general wireless communication system.