• International Journal of Railway
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• 제5권1호
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• pp.29-37
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• 2012

The rail sector, despite its potential for curtailing the present chaotic transport situation in Lagos, remains inefficient and underutilized. In spite of past initiatives and the current attempt by the Lagos State Government to provide a mass transit rail service in Lagos, the share of rail mode in the transport sector has not been encouraging and the railway plays an insignificant role in urban mass transit in Lagos at present. This paper sets out to assess the usage of the Lagos mass transit trains. Hence, the paper determines the passenger traffic flow along the rail route in Lagos and the number of passengers carried between 2000 and 2009 by the Lagos Mass Transit Trains (LMTT) with a view to assessing the usage of the present LMTT. This paper also discusses the historical development of Nigerian railway and describes rail transport in Lagos. Data were obtained through secondary sources coupled with review of literature. The result of this study shows that for a period of 10 years (2000-2009), Lagos mass transit trains carried a total of 9,870,101 passengers, which gives an average of 987,010 passengers annually. This suggests that the service of the Lagos mass transit train is grossly underutilized. However, LMTT contributes enormously to NRC by carrying 68.5% of the total passenger traffic of NRC between 2000 and 2009. In terms of passenger traffic flow along the route of LMTT, for a period of 1 year, Agbado station recorded the largest number of passengers (393,811), followed by Ijoko (163,652) and Iddo (120,787), while Iganmu station has the lowest number of rail commuters (16,919). This study also discloses that the major commodities hauled by Lagos district of NRC from Lagos to the northern parts of the country in 2007 are Cars, Cement, Billet and Wheat.

• 대한전자공학회논문지SP
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• 제42권2호
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• pp.151-160
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• 2005

본 논문에서는 연속제거 알고리즘(successive elimination algerian)을 기반으로 하여 H.264 부호화기의 복잡도에서 가장 큰 비중을 차지하는 가변 블록에 대한 움직임 추정을 효율적으로 생략함으로써 고속으로 움직임 벡터를 탐색하는 기법을 제안한다. 제안된 기법은 7가지 모드의 가변 블록에 대하여 기존의 SEA를 계층적으로 적용한다. 즉, SEA를 사용해서 $4\times4$ 블록 단위로 SAD 또는 sum norm을 조합하고 이것을 각 모드의 최소 SAD 값과 비교 검색함으로써 불필요한 SAD 계산을 줄이는 방식이다. 그러므로 SEA의 SAD와 sum norm의 부등 관계에서 경계범위를 좁게 만들 수 있다. 단위 블록의 크기를 $4\times4$ 이하로 할 경우에는 경계 범위를 더욱 좁게 만들 수 있으나 계산량이 증가하는 단점이 있다. 제안된 기법을 적용했을 때에 각 실험영상에 따른 전체적인 계산량은 H.264의 고속 전역 탐색 방식에 비하여 약 $60\%\~70\%$의 일관된 감소가 있었다.

• 대한기계학회논문집B
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• 제21권8호
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• pp.1068-1076
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• 1997

Emission control of acid exhaust gases from coal-fired power plants and waste incinerators has become an increasing concern of both industries and regulators. Among those gaseous emissions, SO$_{2}$ has been eliminated by a Spray Drying Absorber (SDA) system, where the exhaust gas is mixed with atomized limestone-water slurry droplets and then the chemical reaction of SO$_{2}$ with alkaline components of the liquid feed forms sulfates. Liquid atomization is necessary because it maximizes the reaction efficiency by increasing the total surface area of the alkaline components. An experimental study was performed with a laboratory scale SDA to investigate whether the scrubbing efficiency for SO$_{2}$ reduction increased or not with the application of a DC electric field to the limestone-water slurry. For a selected experimental condition SO$_{2}$ concentrations exited from the reactor were measured with various applied voltages and liquid flow rates. The applied voltage varied from -10 to 10 kV by 1 kV, and the volume flow rate of slurry was set to 15, 25, 35 ml/min which were within the range of emission mode. Consequently, the SO$_{2}$ scrubbing efficiency increased with increasing the applied voltage but was independent of the polarity of the applied voltage. For the electrical and flow conditions considered a theoretical study of estimating average size and charge of the atomized droplets was carried out based on the measured current-voltage characteristics. The droplet charge to mass ratio increased and the droplet diameter decreased as the strength of the applied voltage increased.

• Journal of Welding and Joining
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• 제31권1호
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• pp.43-50
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• 2013

The spot welds of Transformation Induced Plasticity (TRIP) steels are prone to interfacial failure and narrow welding current range. Hard microstructures in weld metal and heat affected zone arenormally considered as one of the main reason to accelerate the interfacial failure mode. There fore, detailed observation of weld microstructure for TRIP steels should be made to ensure better weld quality. However, it is difficult to characterize the microstructure, which has similar color, size, and shape using the optical or electron microscopy. The atomic force microscope (AFM) can help to analyze microstructure by using different energy levels for different surface roughness. In this study, the microstructures of resistance spot welds for AHSS are analyzed by using AFM with measuring the differences in average surface roughness. It has been possible to identify the different phases and their topographic characteristics and to study their morphology using atomic force microscopy in resistance spot weld TRIP steels. The systematic topographic study for each region of weldments confirmed the presence of different microstructures with height of 350nm for martensite, 250nm for bainite, and 150nm for ferrite, respectively.

• 소성∙가공
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• 제24권1호
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• pp.44-51
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• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.

• 농촌계획
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• 제24권3호
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• pp.73-86
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• 2018

Agricultural or rural landscape provides various ecosystem services. However, the ecosystem services function is declining due to various environmental problems such as climate change, land use change, stream intensification, non-point pollution and garbage. The A1B scenario predicts that the mean air temperature of South Korea will rise $3.8^{\circ}C$ degrees celsius in 2100. Agricultural sector is very vulnerable to climate change, so it must be thoroughly predicted and managed. In Korea, the facility horticulture complex is 54,051ha in 2016 and is the 3rd largest in the world(MAFRA, 2014). Facilities of horticultural complexes are reported to cause problems such as groundwater decrease, vegetation and insects diversity reduction, landscapes damage and garbage increase, compared with the existing land use paddy fields. Heat island phenomenon associated with climate change is also accelerated by the high heat absorption of horticultural sites. Therefore, we analyzed the heat island phenomenon occurring in the facility of horticultural complex in Korea. As an improvement measurement, I examined how much air temperature is reduced by putting the channel and the open space. In the case of the Buyeo area, the Computational Fluid Dynamics (CFD) simulation was analyzed for the average summer temperature distribution in the current land use mode at $38.9^{\circ}C$. As an improvement measurement, CFD simulation after 10% of 6m water channel was found to have an effect of lowering the summer temperature of about $2.7^{\circ}C$ compared with the present average of $36.2^{\circ}C$. In addition, CFD simulations after analyzing 10% of the open space were analyzed at $34.7^{\circ}C$, which is $4.2^{\circ}C$ lower than the present. For the Jinju area, CFD simulations were analyzed for the average temperature of summer at $37.8^{\circ}C$ in the present land use pattern. As an improvement measure, CFD simulations after 10% of 6m water channel were found to have an effect of lowering the summer temperature of about $2.6^{\circ}C$ compared to the current average of $35.2^{\circ}C$. In addition, CFD simulations after analyzing 10% of the open space were analyzed at $33.9^{\circ}C$, which is $3.9^{\circ}C$ lower than the present. It can be said that the effect of summer temperature drop in open space and waterway has been proven. The results of this study are expected to be reflected in sustainable agriculture land use and used as basic data for government - level policy in land use planning for climate change.

• 방송공학회논문지
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• 제24권3호
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• pp.463-471
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• 2019

본 논문에서는 양방향 화면 간 예측에서 LIC(Local Illuminance Compensation)의 복잡도 감소를 위한 방법을 제안한다. LIC는 화면 간 예측의 정확도를 높이기 위해 현재 블록과 참조블록의 주변 복원샘플을 이용하여 지역 조명 보상을 수행한다. 지역 조명 보상을 위해 필요한 가중치와 오프셋을 주변 복원 샘플을 이용하여 부/복호화기 양측에서 계산하기 때문에 별도의 정보 전송 없이 부호화 효율이 향상되는 장점이 있지만 부호화 예측 단계 및 복호화 단계에서 가중치와 오프셋을 구하기 때문에 부/복호화 복잡도가 높아지는 단점을 가지게 된다. 따라서 본 논문에서는 저 복잡도 LIC를 위해 크게 두 가지 방법을 제안한다. 첫 번째 방법은 양방향 예측 시 가중치 없이 오프셋만으로 조명보상을 적용하는 방법이고, 두 번째는 양방향 예측에서 LIC를 양방향예측을 통해 구해진 참조 블록의 가중 평균 단계 이후 적용하는 방법이다. 제안하는 방법의 성능 평가를 위하여 RA(Random Access) 조건에서 MPEG 표준 실험 영상의 B, C, D 클래스를 이용하여 BMS-2.0.1과 BD-rate 성능을 비교한다. 실험결과로서 본 논문에서 제안하는 방법이 BMS-2.0.1 대비 BD-rate 성능 관점에서 Y, U, V 각각에 대하여 평균 0.29%, 0.23%, 0.04%의 BD-rate 결과를 보이고 부/복호화 시간은 거의 동일하다. BD-rate의 손실이 있었지만, LIC 파라미터 유도과정에서 곱셈 연산이 제거되고 덧셈 연산이 절반으로 감소됨에 따라 LIC의 계산 복잡도가 크게 감소되었다.

• 전자공학회논문지SC
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• 제44권6호
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• pp.57-65
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• 2007

본 논문에서는 DSP(TMS320F2812)를 사용하여 단상 역률개선을 디지털로 설계하였다. 이러한 승압형 역률개선 컨버터를 디지털로 구현하기 위하여 DSP는 컨버터의 입력전압과 인덕터전류, 컨버터의 출력전압이 필요하며 이를 DSP 내부에 있는 12비트 A/D변환기로 구현하였다. 승압을 위한 스위칭소자인 FET가 ON/OFF 될 때 심한 고주파 노이즈와 스위칭 리플이 발생한다. DSP에 의해 구현시 어느 시점에서 A/D 변환을 시작할지 결정하는 것은 대단히 중요하며 스위칭 노이즈가 발생하지 않는 곳에서 A/D 변환을 할 필요가 있다. PWM의 시비율(duty ratio)은 약 5 %에서 95 %까지 가변적이기 때문에 A/D 변환의 고정된 시작점을 찾을 수는 없다. 따라서 본 논문에서는 25 us 마다 PWM의 ON/OFF 폭을 미리 예측한 후 타이머를 이용하여 A/D 변환을 하도록 하였다. 실험 결과들로부터 광범위한 입력전압에 대하여 약 0.99의 역률과 80 Vdc 출력 전압에 대한 리플이 약 5 Vpp임을 확인하였다. 또한 윈도우즈 Xp 환경 하에서 수행되는 응용프로그램을 작성하여 원격에서 단상 PFC 컨버터의 각종 파라미터들과 전압 및 전류 제어기의 이득들을 모니터링하며 원격제어가 가능함을 보여 상용화의 가능성과 유용성을 제시하였다.

• 한국정보통신학회논문지
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• 제10권9호
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• pp.1663-1670
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• 2006

펄스 전기증착법에 의해 단결정 Fe 박막을 n-Si(111) 기판위에 직접 성장시켰다. CV 분석 을 통해 $Fe^{2+}n-Si(111)$ 계면은 쇼트키 장벽 형성에 따른 다이오드 특성을 가진다는 사실을 알 수 있었다. 또한 인가 전압에 따른 전기용량의 변화를 보여주는 Mott-Schottky chottky(MS) 관계식을 이용하여 전해질 내에서 n-Si(111) 기판의 flat-band potential(EFB)을 조사하였으며, 0.1M $FeCl_2$ 전해질 내에서 EFB와 산화-환원 전위는 각각 -0.526V 과 -0.316V 임을 알 수 있었다. Fe/n-Si(111) 계면반응 시, Fe 증착 초기 단계에서의 핵 형성과 성장 운동학은 과도전류 특성을 이용하여 조사하였으며, 과도전류 특성을 통해 Fe 박막의 성장모드는 "instantaneous nucleation and 3-dimensional diffusion limited growth"임을 알 수 있었다. 주파수가 300Hz, 최대 전압이 1.4V인 펄스 전압을 이용하여 n-Si(111) 기판위에 Fe를 직접 전기 증착 시켰으며, 형 성 된 Fe 박막은 단결정 ${\alpha}-Fe$로 Si 기판위에 ${\alpha}-Fe(110)/Si(111)$의 격자 정합성을 가지고 성장하였음을 XRD 분석을 통해 확인하였다.

• Journal of Power Electronics
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• 제11권4호
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• pp.408-417
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• 2011

The plug-in hybrid electric vehicles (PHEVs) are specialized hybrid electric vehicles that have the potential to obtain enough energy for average daily commuting from batteries. The PHEV battery would be recharged from the power grid at home or at work and would thus allow for a reduction in the overall fuel consumption. This paper proposes an integrated power electronics interface for PHEVs, which consists of a novel Eight-Switch Inverter (ESI) and an interleaved DC/DC converter, in order to reduce the cost, the mass and the size of the power electronics unit (PEU) with high performance at any operating mode. In the proposed configuration, a novel Eight-Switch Inverter (ESI) is able to function as a bidirectional single-phase AC/DC battery charger/ vehicle to grid (V2G) and to transfer electrical energy between the DC-link (connected to the battery) and the electric traction system as DC/AC inverter. In addition, a bidirectional-interleaved DC/DC converter with dual-loop controller is proposed for interfacing the ESI to a low-voltage battery pack in order to minimize the ripple of the battery current and to improve the efficiency of the DC system with lower inductor size. To validate the performance of the proposed configuration, the indirect field-oriented control (IFOC) based on particle swarm optimization (PSO) is proposed to optimize the efficiency of the AC drive system in PHEVs. The maximum efficiency of the motor is obtained by the evaluation of optimal rotor flux at any operating point, where the PSO is applied to evaluate the optimal flux. Moreover, an improved AC/DC controller based Proportional-Resonant Control (PRC) is proposed in order to reduce the THD of the input current in charger/V2G modes. The proposed configuration is analyzed and its performance is validated using simulated results obtained in MATLAB/ SIMULINK. Furthermore, it is experimentally validated with results obtained from the prototypes that have been developed and built in the laboratory based on TMS320F2808 DSP.