• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.459-461
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• 2022

One of the big differences between Network-on-Chip (NoC) and the existing parallel processing system based on an off-chip network is that data packet routing is performed using a centralized control scheme. In such an environment, the best-effort packet routing problem becomes a real-time assignment problem in which data packet arriving time and processing time is the cost. In this paper, the Hungarian algorithm, a representative computational complexity reduction algorithm for the linear algebraic equation of the allocation problem, is implemented in the form of a hardware accelerator. As a result of logic synthesis using the TSMC 0.18um standard cell library, the area of the circuit designed through case analysis for the cost distribution is reduced by about 16% and the propagation delay of it is reduced by about 52%, compared to the circuit implementing the original operation sequence of the Hungarian algorithm.

• Wind and Structures
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• v.11 no.4
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• pp.257-273
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• 2008

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package $CFX^{TM}$ was used. It has been found that dramatic reductions in coefficient of drag ($C_D$) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended.

• ETRI Journal
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• v.37 no.6
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• pp.1143-1153
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• 2015

In this paper, we propose an efficient architecture for a real-time image stitching engine for vision SoCs found in motor vehicles. To enlarge the obstacle-detection distance and area for safety, we adopt panoramic images from multiple telegraphic cameras. We propose a stitching method based on a fixed homography that is educed from the initial frame of a video sequence and is used to warp all input images without regeneration. Because the fixed homography is generated only once at the initial state, we can calculate it using SW to reduce HW costs. The proposed warping HW engine is based on a linear transform of the pixel positions of warped images and can reduce the computational complexity by 90% or more as compared to a conventional method. A dual-core SW/HW image stitching engine is applied to stitching input frames in parallel to improve the performance by 70% or more as compared to a single-core engine operation. In addition, a dual-core structure is used to detect a failure in state machines using rock-step logic to satisfy the ISO26262 standard. The dual-core SW/HW image stitching engine is fabricated in SoC with 254,968 gate counts using Global Foundry's 65 nm CMOS process. The single-core engine can make panoramic images from three YCbCr 4:2:0 formatted VGA images at 44 frames per second and frequency of 200 MHz without an LCD display.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.908-910
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• 1998

Modern AC electric car has PWM(Pulse Width Modulation) -controlled converters, which give rise to higher harmonics. The current harmonics injected from AC electric car is propagated through power feeding circuit. As the feeding circuit is a distributed constant circuit composed of RLC, the capacitance of the feeding circuit and the inductance on the side of power system cause a parallel resonance and a magnification of current harmonics at a specific frequency. The magnified current harmonics usually brings about various problems. That is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. Furthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. From these point of view, this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current. The proposed algorithm is applied to a standard AT(Auto-transformer)-fed test system in which electric car with PWM-controlled converters is running.

• Journal of Navigation and Port Research
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• v.27 no.1
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• pp.81-86
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• 2003

In the paper, the power amplifier using active biasing for LDMOS MRF-21060 is designed and fabricated. Driving amplifier using AH1 and parallel power amplifier AH11 is made to drive the LDMOS MRF 21060 power amplifier. The variation of current consumption in the fabricated 5 Watt power amplifier has an excellent characteristics of less than 0.1A, whereas passive biasing circuit dissipate more than 0.5A. The implemented power amplifier has the gain over 12 dB, the gain flatness of less than $\pm$0.09dB and input and output return loss of less than -19dB over the frequency range 2.11~2.17GHz. The DC operation point of this power amplifier at temperature variation from $0^{\circ}C$ to $60^{\circ}C$ is fixed by active circuit.

• Journal of Korean Society on Water Environment
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• v.22 no.4
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• pp.711-719
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• 2006

The effluent from anaerobic digestion process of slurry-type piggery waste has a characteristic of very low C/N ratio. Because of high nitrogen content, it is necessary to evaluate nitrogen removal alternative rather than conventional nitrification-denitrification scheme. In this study, two parallel treatment schemes of SBR-like partial nitritation reactor coupled with anaerobic ammonium oxidation (ANAMMOX) reactor, and a nitritation reactor followed by nitrite denitrification process were evaluated with a slurry-type piggery waste. The feed to reactors adjusted with various $NH_4-N$ and organics concentration. The nitrite accumulation was successfully accomplished at the loading rate of about $1.0kgNH_4-N/m^3-day$. The $NO_2-N/NH_4-N$ ratio 1~2.6 in nitritated effluent that operated at HRT of 1 day indicated that SBR-like partial nitritation was applicable to ANAMMOX operation. Meanwhile, the nitrite accumulation of 87% was achieved at SBR operated with HRT of 3 days and $0.4mgO_2/L$ for denitritation. Experimental results further suggested that HRT (SRT) and free ammonia(FA) rather than DO are an effective control parameter for nitrite accumulation in piggery waste.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.23-27
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• 2012

This paper aims to evaluate the feasibility of using no-insulation High Temperature Superconducting (HTS) coil in persistent current mode system. A HTS coil in persistent current mode system usually includes one or more non-superconducting joints in its circuit. And the current decaying rate of the coil is affected by the resistance of joint in persistent current circuit. If the resistance of joint is large, decaying rate of the current drastically increases. Therefore, reducing the joint resistance of the HTS coil is very important in persistent current mode system. In this paper, the no-insulation HTS coil is suggested as a way to reduce the joint resistance with the embedded parallel contact resistance naturally made by no-insulation winding method. Two small coils are fabricated with insulation and no-insulation winding method, and persistent current mode system experiment of each coil is preformed and analyzed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.10
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• pp.1426-1431
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• 2015

Piezoelectric pump can be considered as R-C load and it needs something special driver because the output voltage does not become 0 even though the applied voltage is 0 with common converter. This operating system consists of fly-back converter to increase the input voltage and energy recovery inverter to apply square voltage to the piezoelectric pump. The energy recovery inverter can charge and discharge the energy of capacitive load. In this paper, to enhance performance of the driver, a few elements or circuits are added and modified. To drive the inverter safely, current limit resister is added and adjusted the value to valance the charging and discharging current. In addition, a current limit inductor is added to the input side to limit the input current and enhance the efficiency. Inductor only may make oscillation and another resister is added parallel to the inductor to solve this problem. The converter and inveter are assembled to one board for compactness. The appropriateness is proved with simulation and experiments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.6
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• pp.293-299
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• 2015

In Korea, it is the law that an apartment building which consists of over 100 households must have a ventilation system installed, either natural or mechanical. The heat recovery ventilator (HRV) is great way to reduce energy consumption. In this research we confirmed that based on site's construction plan and existing diffuser form, performed purpose CFD which simulates operation in temperatures below $-5^{\circ}C$ to circumstances of installation of an HRV in an apartment. As a result of this research we found that when the diffuser's aperture area was adjusted, the distribution of air temperature and residence time of air was more equally distributed and air temperature was higher, compared to when the diffuser has an identical aperture area. We also found that we are able to increase even more air temperature and air distribution of air temperature and residence time of air was even more equally distributed when run in parallel with a splitter damper.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.438-440
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• 2006

포항가속기 연구소의 선형가속기와 빔 전송선에는 22개의 솔레노이드 전자석, 38개의 사극전자석 그리고 전자빔의 궤도 조절을 위한 29개의 2극 전자석이 있다. 전자빔의 정밀 제어를 위한 전자적 전원장치는 고정도, 고안정도 출력 특성을 가져야 한다. 이를 위하여 풀-브릿지 4-상한 DC-DC 컨버터 토플로지의 4단 병렬운전을 채택하였다. 전원장치의 입력전압은 직류 40V이고, 최대 출력전류는 직류 50A이며 그리고 스윗칭 주파수는 50 kHz이다. 고정밀, 고안정도 출력전류를 얻기 위하여 입력단의 전원 노이즈 및 전력변환부의 스윗칭 노이즈를 제거하여야 한다. 이를 위하여 채택된 low-pass 필터의 cut-off 주파수는 입력과 출력단 각각 26 Hz와 4.5 kHz 이다. 출력전류에서 전원장치로부처 발생하는 주파수 성분을 완벽하게 제거하였다. 출력전류의 분해능은 1mA 이하이며, 안정도는 10시간 이상 장시간의 경우 +/-15 ppm 이하이고 1시간 이하 단시간의 경우 +/-10ppm 이하이다. 본 논문에서는 풀-브릿지 4-상한 DC-DC 컨버터 토플로지의 4단 병렬운전을 채택한 전자석 전원장치의 구성, 특성 그리고 실험결과에 대하여 기술하였다.