PV/디젤 하이브리드 시스템 전력계통에서 부하변동 시 전압특성

류연수(Ryu Yeon-Soo),윤진수(Yoon Jin-Soo) 한국태양에너지학회 2010 한국태양에너지학회 학술대회논문집 Vol.2010 No.4

The Complex Generating System, which uses parallel connection of Photovoltaic System and other generating systems, is divided into 2 types. One is AC parallel system and the other is DC parallel system. AC parallel system consists of alternating generator (diesel generator) and direct generator (wind power or solar power generator), which are connected through 2-way invertor so that the generated power can be transformed into AC power and finally covers the power load. In case it generates surplus electricity, the residual power is to be charged in batteries to raise the performance and the power balance. This study is to explore the electric characteristics such as power voltage, and the change of power load when operating both Utility Interactive Photovoltaic System and Diesel AC Generator connected to the system in alternating current and with influx of residual power from the Photovoltaic System. As a result of Road Variation and supplying 10.7 ㎾, 13.5 ㎾ of residual power, it has been found that Synchronous Generator takes the power input only as reactive power, because it was electrically stable with high voltage of 221[㎾] even when power factor was -0.901. Thus, load share of Revolving Field Type Synchronous Generator reduces according to the supply of Photovoltaic System to the load power. In this experiment, 200[㎾] of Synchronous Generator and 40[㎾] of Photovoltaic System were operated in parallel. The load share was 20% in maximum, and fuel was saved. Utility Interactive Photovoltaic System and Diesel Engine Revolving Field Type Synchronous Generator are usually implemented in remote regions like islands and mountains where KEPCO Distribution network does not reach. This thesis is to present effective ways of control for A.C. parallel operation by researching electrical, mechanical characteristics of it.

PVFS에서 동적 I/O 연산 로깅 시스템 설계

윤여중(Yeo-joong Yoon),최지우(Ji-Woo Choi),채종수(Chae-Jong Soo),서창호(Chang-Ho Seo) 한국정보기술학회 2010 Proceedings of KIIT Conference Vol.2010 No.-

네트워킹 기법을 이용하여 다수의 디스크 또는 스토리지를 연결하고 I/O처리를 분산시키는 병렬 파일 시스템의 개념을 만들었다. 즉, 다수의 컴퓨터에 장착된 디스크나 스토리지를 네트워크로 연결하여 하나의 논리적인 파일 시스템으로 구성함으로써 유휴 자원의 활용, I/O 처리 대역폭 증대 등의 효과를 기대할 수 있다. 특히 PVFS(Parallel Virtual File System)의 경우 클러스터 시스템의 확산과 함께 병렬 파일시스템 연구에 활발히 이용되고 있다. 본 논문에서는 기존의 파일 시스템들의 로깅 방법들을 알아보고, 클러스터 시스템에서 널리 이용되고 있는 파일 시스템인 PVFS(Parallel Virtual File System)에서 동적 I/O연산 로깅 시스템을 설계하였다. The concept of a parallel file system which connects multiple disks or storages and distributes I / O processing by using networking techniques. In other words, we can expect an effect of applying unused resources and increasing bandwidth I/O for processing through organizing one logical file system by connecting disks or storages attached many of computers with network. Especially, PVFS(Parallel Virtual File System), is widely used in research of parallel file system with spread of cluster system. In this paper, we surveyed the logging methods of the existing file systems and designed and implemented logging system of dynamic I/O arithmetic in PVFS(Parallel Virtual File System) cluster system.

A Feasibility Design of PEMFC Parallel Operation for a Fuel Cell Generation System

Hyun-Soo Kang,Gyu-Yeong Choe,Byoung-Kuk Lee,Jin Hur 대한전기학회 2008 Journal of Electrical Engineering & Technology Vol.3 No.3

In this paper, the parallel operation for a FC generation system is introduced and designed in order to increase the capacity for the distributed generation of a proton exchange membrane fuel cell (PEMFC) system. The equipment is the type that is used by parallel operated PEMFC generation systems which have two PEMFC systems, two de/de boost converters with shared de link, and a grid-connected dc/ac inverter for embedded generation. The system requirement for the purpose of parallel operated generation using PEMFC system is also described. Aspects related to the mechanical (MBOP) and electrical (EBOP) component, size, and system complexity of the distributed generation system, it is explained in order to design an optimal distributed generation system using PEMFC. The optimal controller design for the parallel operation of the converter is suggested and informative simulations and experimental results are provided.

Comparison of a Newly-designed Stack-up Collimator with Conventional Parallel-hole Collimators in Pre-clinical CZT Gamma Camera Systems: A Monte Carlo Simulation Study

이영진,김희중 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.7

Recently, many studies have been conducted with pixelated semiconductor detectors that usecadmium zinc telluride (CZT) because these detectors have many advantages in pre-clinical gammaimaging. Collimators play an extremely important role in the imaging performance of pixelatedsemiconductor gamma cameras. In our previous study, based on the pixelated semiconductor gammacamera system we recommended the use of a pixelated parallel-hole collimator with equal hole andpixel sizes; this approach improved both the sensitivity and the spatial resolution. However, thepixelated parallel-hole collimator had two major limitations: (a) Although its sensitivity was higherthan that of pinhole systems, the pixelated parallel-hole collimator may have still resulted in apartial loss of sensitivity due to its small collimator hole size. (b) The pixelated parallel-holecollimator with an adequate septal height was difficult to manufacture due to its small holes. Here,we present a new design for a parallel-hole collimator, which uses the stack-up method and aCZT pixelated semiconductor gamma camera system. The purpose of this study was to comparethe performances of various geometric designs of our newly-designed parallel-hole collimator withthose of conventional parallel-hole collimators [low-energy high-resolution (LEHR) and low-energyhigh-sensitivity (LEHS)]. The detector was modeled as an eValuator-2500 (eV MicroelectronicsInc., Saxonburg, PA, USA) (3-mm thick, 0.5-mm pixel size) by using a Geant4 Application forTomographic Emission (GATE) simulation. The proposed parallel-hole collimator consisted of twooverlapping parallel-hole collimators. The size of each hole in the proposed parallel-hole collimatorwas four times that of the hole in the pixelated parallel-hole collimator. The overlap ratios of thesecollimators were 1 : 1, 1 : 2, 2 : 1, 1 : 5, and 5 : 1. To evaluate and compare the performancesof these systems, we evaluated the sensitivity and the spatial resolution of each system. Theaverage sensitivities of the proposed parallel-hole collimators with overlap ratios of 1 : 1, 1 : 2 or2 : 1, and 1 : 5 or 5 : 1 and of the LEHS conventional parallel-hole collimator were 2.17, 3.45,13.90, and 3.68 times higher than the average sensitivities of the LEHR conventional parallel-holecollimator, respectively. The average spatial resolution also varied depending on the distance fromthe collimator. In conclusion, we successfully designed a novel parallel-hole collimator for pre-clinicalimaging; this novel collimator employs the stack-up method with a CZT pixelated semiconductorgamma camera.

영상처리를 위한 Pipelined 병렬처리 시스템

이형,김종배,최성혁,박종원,Lee, Hyung,Kim, Jong-Bae,Choi, Sung-Hyk,Park, Jong-Won 한국전기전자학회 2000 전기전자학회논문지 Vol.4 No.2

In this paper, a parallel processing system is proposed for improving the processing speed of image related applications. The proposed parallel processing system is fully synchronous SIMD computer with pipelined architecture and consists of processing elements and a multi-access memory system. The multi-access memory system is made up of memory modules and a memory controller, which consists of memory module selection module, data routing module, and address calculating and routing module, to perform parallel memory accesses with the variety of types: block, horizontal, and vertical access way. Morphological filter had been applied to verify the parallel processing system and resulted in faithful processing speed. 본 논문에서는 영상 응용프로그램의 처리 속도를 향상하기 위한 병렬처리 시스템을 제안한다. 병렬처리 시스템은 Pipelined SIMD 구조를 갖고 있으며, 다수개의 처리기와 다중접근 기억장치로 구성된다. 다중접근 기억장치는 메모리 모듈들과 메모리 제어부로 구성되며, 메모리 제어부는 메모리 모듈 선택 모듈, 데이터 라우팅 모듈, 그리고 주소 계산 및 라우팅 모듈로 구성되어 있으며, 블록, 행, 그리고 열 내의 데이터를 동시에 접근할 수 있는 기능을 제공한다. 제안한 병렬처리 시스템을 검증하기 위해서 형태학적 필터를 적용하여 기능 검증 및 처리속도를 확인하였다.

System Control Methods for Energy Efficiency Improvement of Parallel Pump Systems: A Review

Chenchen Hua,Maosen Xu,Jiegang Mou,Junlei Wang,Peijian Zhou,Xuelong Yang 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.4

With the consistent pursuit of global countries for the goal of carbon neutrality, the urgency of energy saving and emission reduction is self-evident. Considering the critical proportion of pump consumption in the total energy consumption, improving its energy efficiency is significant to energy saving and emission reduction. Recently, many researches have aimed to improve parallel pump systems' energy efficiency. Due to the inflexibility of the existing parallel pump systems structure and the difficulty of equipment modification, the research methods mainly focus on improving the system control methods to enhance the system performance further. This paper introduces the latest research progress in modeling and control methods for parallel pump systems, firstly analyzing the energy consumption of existing parallel pump systems and proposing the possibility of energy saving in parallel pump systems. Then the system modeling and control methods are discussed in detail, comparing the traditional control methods with the emerging control optimization methods and discussing the parallel pump systems structure and monitoring. This review is expected to provide insights for future research on improving the performance of parallel pump systems.

평지붕 PV거치 시스템의 형태에 따른 풍압영향에 관한 기초연구

윤두영(Yun Doo-Young),이응직(Lee Eung-Jik) 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.5

The new renewable energy became popular as a clean and sustainable alternative energy under the circumstances that the entire world is facing severe abnormal climate due to the use of fossil fuel, and among which, solar energy can be obtained anywhere and is not difficult to apply it into the existing buildings, which makes it possible to be widely distributed. However, as PV module is installed into a single plate system, it shows structural weaknesses which are vulnerable to wind load and give loss to design elements in external appearance. Accordingly, this study planned one-step parallel system to complement the problems occurring from a single plate system and used STAR-CCM+V.8 made by CD-Adapco, a computational fluid dynamics(CFD) simulation tool to measure wind load stability and support based on the design standards for a single plate system and one-step parallel system. Building height was limited to less than 10m and wind speed was given when increasing from 35㎧ to 50㎧ by 5㎧ on PV system installed into the flat roof. In this case, our analysis suggested that step-one parallel system was inclass7-9 according to Beaufort’s wind power classification, which did not have an impact on the fixed PV system, and the single plate system is considered to cause risks in designing wind speed in central districts because it is more than wind power class12.

A Feasibility Design of PEMFC Parallel Operation for a Fuel Cell Generation System

Kang, Hyun-Soo,Choe, Gyu-Yeong,Lee, Byoung-Kuk,Hur, Jin The Korean Institute of Electrical Engineers 2008 Journal of Electrical Engineering & Technology Vol.3 No.3

In this paper, the parallel operation for a FC generation system is introduced and designed in order to increase the capacity for the distributed generation of a proton exchange membrane fuel cell (PEMFC) system. The equipment is the type that is used by parallel operated PEMFC generation systems which have two PEMFC systems, two dc/dc boost converters with shared dc link, and a grid-connected dc/ac inverter for embedded generation. The system requirement for the purpose of parallel operated generation using PEMFC system is also described. Aspects related to the mechanical (MBOP) and electrical (EBOP) component, size, and system complexity of the distributed generation system, it is explained in order to design an optimal distributed generation system using PEMFC. The optimal controller design for the parallel operation of the converter is suggested and informative simulations and experimental results are provided.

근관장 측정에서 방사선 사진술의 정확도

조은영,박창서 大韓口腔顎顔面 放射線學會 1998 Imaging Science in Dentistry Vol.28 No.2

For the successful endodontic treatment, root canal should be cleaned thoroughly by accurate mechanical and chemical canal preparation and sealed completely with canal filling material without damaging the periapical tissues. The accuracy of the root canal length measurement is a prerequisite for the success of the endodontic treatment, and the root canal length is often determined by the standard periapical radiographs and digital tactile sense. In this study, the accuracy and the clinical usefulness of Digora, an intraoral digital imaging processor and the conventional standard radiographs were compared by measuring the length from the top of the file to the root apex. 30 single rooted premolars were invested in a uniformly sized blocks and No.25 K-file was inserted into and fixed in each canal. Each block was placed in equal distance and position to satisfy the principle of the bisecting angle and paralleling techniques and Digora system's image and standard periapical radiographs were taken. Each radiograph was examined by 3 different observers by measuring the length from top of the file to the root apex and each data was compared and analyzed. The results were as follows; 1. In the bisecting angle technique, the average difference between the Digora system and standard periapical radiograph was 0.002 mm and the standard deviation was 0.341 mm which showed no statistically significant difference between the two systems(p>0.05). Also, in the paralleling technique, the average difference between these two system was 0.007mm and the standard deviation was 0.323mm which showed no statistically significant difference between the two systems(p>0.05). 2. In Digora system, the average difference between the bisecting angle and paralleling technique was -0.336mm and the standard deviation was 0.472mm which showed a statistically significant difference between the two techniques(p<0.05). Also, in the standard periapical radiographs, the average difference between the bisecting angle and paralleling technique was 0.328mm and the standard deviation was 0.517mm which showed a statistically significant difference between these two techniques(p<0.05). 3. In Digora system and the standard periapical radiographs, there was a statistically significant difference between the measurement using the bisecting angle technique and the actual length(p<0.05). But there was no statistically significant difference between the measurement using the paralleling technique and the actual length(p>0.05). In conclusion, the determination of the root canal length by using the Digora system can give us as good an image as the standard periapical radiograph and using the paralleling technique instead of the bisecting angle technique can give a measurement closer to the actual canal length, thereby contributing to a successful result. Also, considering the advantages of the digital imaging processor such as decreasing the amount of exposure to the patient, immediate use of the image, magnification of image size, control of the contrast and brightness and the ability of storing the image can give us good reason to replace the standard periapical radiographs.

Performance evaluation of a small CZT pixelated semiconductor gamma camera system with a newly designed stack-up parallel-hole collimator

Lee, Y.,Kim, H.J. North-Holland 2015 Nuclear Instruments & Methods in Physics Research. Vol.794 No.-

Gamma ray imaging techniques that use a cadmium zinc telluride (CZT) or cadmium telluride (CdTe) pixelated semiconductor detectors have rapidly gained popularity as a key tool for nuclear medicine research. By using a pinhole collimator with a pixelated semiconductor gamma camera system, better spatial resolution can be achieved. However, this improvement in spatial resolution is accomplished with a decrease in the sensitivity due to the small collimator hole diameter. Furthermore, few studies have been conducted for novel parallel-hole collimator geometric designs with pixelated semiconductor gamma camera systems. A gamma camera system which combines a CZT pixelated semiconductor detector with a newly designed stack-up parallel-hole collimator was developed and evaluated. The eValuator-2500 CZT pixelated semiconductor detector (eV product, Saxonburg, PA) was selected for the gamma camera system. This detector consisted of a row of four CZT crystals of 12.8mm in length with 3mm in thickness. The proposed parallel-hole collimator consists of two layers. The upper layer results in a fourfold increase in hole size compared to a matched square hole parallel-hole collimator with an equal hole and pixel size, while the lower layer also consisted of fourfold holes size and pretty acts as a matched square hole parallel-hole collimator. The overlap ratios of these collimators were 1:1, 1:2, 2:1, 1:5, and 5:1. These collimators were mounted on the eValuator-2500 CZT pixelated semiconductor detector. The basic performance of the imaging system was measured for a <SUP>57</SUP>Co gamma source (122keV). The measured averages of sensitivity and spatial resolution varied depending on the overlap ratios of the proposed parallel-hole collimator and source-to-collimator distances. One advantage of our system is the use of stacked collimators that can select the best combination of system sensitivity and spatial resolution. With low counts, we can select a high sensitivity collimator with a 1:5 or 5:1 overlap ratio. For high counts, a 1:1 overlap ratio collimator combination is the best selection at this time. In addition, if a higher system spatial resolution is needed, we can increase the spatial resolution by stacking additional thin collimators. These results demonstrate that the developed small pixelated semiconductor gamma camera system has high potential as an effective instrument for low energy gamma ray imaging.