• Title/Summary/Keyword: Flows Control

Search Result 680, Processing Time 0.039 seconds

A study on digital locking device design using detection distance 13.4mm of human body sensing type magnetic field coil (인체 감지형 자기장 코일의 감지거리 13.4mm를 이용한 디지털 잠금장치 설계에 관한 연구)

  • Lee, In-Sang;Song, Je-Ho;Bang, Jun-Ho;Lee, You-Yub
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.17 no.1
    • /
    • pp.9-14
    • /
    • 2016
  • This study evaluated a digital locking device design using detection distance of 13.4mm of a human body sensing type magnetic field coil. In contrast to digital locking devices that are used nowadays, the existing serial number entering buttons, lighting, number cover, corresponding pcb, exterior case, and data delivery cables have been deleted and are only composed of control ON/OFF power switches and emergency terminals. When the magnetic field coil substrates installed inside the inner case detects the electric resistance delivered from the opposite side of the 12mm interval exterior contacting the glass body part, the corresponding induced current flows. At this time, the magnetic field coil takes the role as a sensor when coil frequency of the circular coil is transformed. The magnetic coil as a sensor detects a change in the oscillation frequency output before and after the body is detected. This is then amplified to larger than 2,000%, transformed into digital signals, and delivered to exclusive software to compare and search for embedded data. The detection time followed by the touch area of the body standard to a $12.8{\emptyset}$ magnetic field coil was 30% contrast at 0.08sec and 80% contrast at 0.03sec, in which the detection distance was 13.4mm, showing the best level.

A Study on the ZVZCS Three Level DC/DC Converter without Primary Freewheeling Diodes (1차측 환류 다이오드를 제거한 ZVZCS Three Level DC/DC 컨버터에 관한 연구)

  • Bae, Jin-Yong;Kim, Yong;Baek, Soo-Hyun;Kwon, Soon-Do;Kim, Pil-Soo;Gye, Sang-Bum
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.16 no.6
    • /
    • pp.66-73
    • /
    • 2002
  • This paper presents ZVZCS(Zero-Voltage and Zero-Current Switching) Three Level DC/DC Converter without primary freewheeling diodes. The new converter presented in this paper used a phase shirt control with a flying capacitor in the primary side to achieve ZVS for the outer switches. A secondary anxiliary circuit which consists of one small capacitor, two small diodes and one coupled inductor, is added in the secondary to provide ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages include simple secondary auxiliary circuit topology, high efficiency, and low cost make the new converter attractive for high power applications. Also the circulating current flows through the circuit so that it causes the needless coduction loss to be occurred in the devices and the transformer of the circuit The new converter has no primary auxiliary diodes for freewheeling current. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1[㎾] 50[KHz]IGBT based experimental circuit.

The Study of the Influence on Long Term Streamflow Caused by Artificial Storage Facilities Based on SWAT Modeling Process (SWAT모형을 이용한 인공저류시설물의 하류장기유출 영향분석 기법에 관한 연구)

  • Shin, Hyun-Suk;Kang, Du-Kee
    • Journal of Korea Water Resources Association
    • /
    • v.39 no.3 s.164
    • /
    • pp.227-240
    • /
    • 2006
  • In the several decades, various storage facilities have been developed and operated to supply water resource, flood control or environmental preservation etc. Then, how those man-maid storage facilities affect on the downstream water and environment and how the hydrologists can evaluate those features for water resources problem-solving are high-concentrated problems in this field. Most large watersheds in Korea contain various types of artificial facilities such dams, reservoirs, in-land ponds, wetlands etc. But the study to develop the technology for achieving the effect of the variances and properties of the long term streamflow caused by the artificial storage facilities have been on the simple watershed models and experimental modeling in the real fields. In this paper, we introduce the procedure and methods to consider the above problems based on continuous and semi-distributed featured SWAT model. At the first, we describe the elements and mechanisms of storage facilities in SWAT model to see how we can apply that in proper and appropriate manner for real field problems. Then, we applied the process to a sample watershed, Taewha River basin which covers the most of Ulsan region. Specially, we concentrate on our effort to the effect of upper reservoirs on down stream long term flows based on various scenario basis. The result was described and analysed in spacial and temporal variations on that basin using the precise manner.

The Macroscopic Model for Signalized Intersections to Consider Progression in relation to Delay (지체시간과 연동성을 동시에 고려하는 신호교차로 시뮬레이션 모형의 개발)

  • Han, Yohee;Kim, Youngchan
    • The Journal of The Korea Institute of Intelligent Transport Systems
    • /
    • v.11 no.6
    • /
    • pp.15-22
    • /
    • 2012
  • A performance index of singalized intersections is a standard to optimize signal control variables and to manage traffic flow. Traffic delays is generally used to minimize the average delay time on intersections or networks, progression efficiency is used to improve travel speed of main cooridors or to provide transit signal priority. We manage traffic flows with only selecting one index between delays and progression according to the objective of traffic management and field characteristics. In real field, the driver's satisfaction is high in any performance criteria when the waiting time is shorter and the unnecessary stop in front of traffic is smaller. This paper aims to develop simulation model to represent real progression with concurrently considering delays and progression. In order to reflect an effect of level of traffic volumes and residual queues which don't be considered in prior progression model, we apply shockwave model with flow-density diagram. We derive Cell Transmission Model of Daganzo in order to develop the delay index and the progression index for the macroscopic simulation model. In order to validate the effect, we analysis traffic delays and progression efficiency with comparing this model to Transyt-7F and PASSER V.

Study of Riverline Change around Sannam Wetland in the Hangang River Estuaty using LANDSAT Image Processing (LANDSAT 위성사진을 활용한 한강하구 산남습지 인근 하안선 변화 연구)

  • Youn, Sukzun;Lee, Samhee;Jang, Changhwan
    • Journal of Wetlands Research
    • /
    • v.23 no.2
    • /
    • pp.154-162
    • /
    • 2021
  • The naturally opened Han river estuary is a place where the flows of the Han river, Imjin river, Yaesung river meet with West Sea of Korea, so the hydrodynamic mechanism(Impact-Response) structure of Han river estuary is complex. Continuous observation and measurement due to the morphological characteristics at the estuary are required to maintain the estuary environment and river management facilities. However, the Sannam wetland(the study area) is in the military operation area. Therefore, Sannam wetland has the limited access under the control from military office. In 2020, there had a natural disaster due to flooding in August and COVID-19, and it made a survey hard. The noncontact survey technique, the analysis of LANDSAT images at Sannam wetland, was applied to analyze riverbed fluctuation and morphological transformation around Sannam wetland. LANDSAT images obtained from EarthExplorer, USGS and analyzed by QGIS. The analysis was performed based on the area and the distance near Sannam wetland. As a result, an erosion was happened on the downstream of the study area, and the upstream of the study area did not have any serious sediment transport. Considering the resolution of LANDSAT images, this noncontect survey technique is applicable to manage the study area. From the analysis of LANDSAT images, it is assumed that the tidal effect is greater than the inflow from the upstream. The pattern change of tidal response causes the damage of the river facilities near the Hangang river estuary.

A Study on Modeling of Leakage Current in ESS Using PSCAD/EMTDC (PSCAD/EMTDC를 이용한 ESS의 누설전류 모델링에 관한 연구)

  • Kim, Ji-Myung;Tae, Dong-Hyun;Lee, Il-Moo;Lim, Geon-Pyo;Rho, Dae-Seok
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.22 no.2
    • /
    • pp.810-818
    • /
    • 2021
  • A leakage current of ESS is classified mainly by the occurrence from a PCS(Power Conditioning System) section and an unbalanced grid current. The reason for the leakage current from the PCS section is a voltage change by IGBT (Insulated Gate Bipolar Transistor) switching and stray capacitance between the IGBT and heatsink. The leakage current caused by the grid unbalanced current flows to the ESS through the neutral line of grid-connected transformer for the ESS with a three limb iron type of Yg-wire connection. This paper proposes a mechanism for the occurrence of leakage current caused by stray capacitance, which is calculated using the heatsink formula, from the aspect of the PCS section and grid unbalance current. Based on the proposed mechanisms, this study presents the modeling of the leakage current occurrence using PSCAD/EMTDC S/W and evaluates the characteristics of leakage currents from the PCS section and grid unbalanced current. From the simulation result, the leakage current has a large influence on the battery side by confirming that the leakage current from the PCS is increased from 7[mA] to 34[mA], and the leakage current from an unbalanced load to battery housing is increased from 3.96[mA] to 10.76[mA] according to the resistance of the housings and the magnitude of the ground resistance.

Effect of ammonia nitrogen and microorganisms on the elevated nitrogenous biochemical oxygen demand (NBOD) levels in the Yeongsan river in Gwangju (광주지역 영산강의 NBOD 발생에 대한 암모니아성 질소 및 미생물 영향 연구)

  • Jang, Dong;Cho, Gwangwoon;Son, Gyeongrok;Kim, Haram;Kang, Yumi;Lee, Seunggi;Hwang, Soonhong;Bae, Seokjin;Kim, Yunhee
    • Journal of Korean Society of Water and Wastewater
    • /
    • v.36 no.2
    • /
    • pp.81-95
    • /
    • 2022
  • The present study was performed to investigate the effects of NH3-N and nitrifying microorganisms on the increased BOD of downstream of the Yeongsan river in Gwangju. Water samples were collected periodically from the 13 sampling sites of rivers from April to October 2021 to monitor water qualities. In addition, the trends of nitrogenous biochemical oxygen demand (NBOD) and microbial clusters were analyzed by adding different NH3-N concentrations to the water samples. The monitoring results showed that NH3-N concentration in the Yeongsan river was 22 times increased after the inflow of discharged water from the Gwangju 1st public sewage treatment plant (G-1-PSTP). Increased NH3-N elevated NBOD levels through the nitrification process in the river, consequently, it would attribute to the increase of BOD in the Yeongsan river. Meanwhile, there was no proportional relation between NBOD and NH3-N concentrations. However, there was a significant difference in NBOD occurrence by sampling sites. Specifically, when 5 mg/L NH3-N was added, NBOD of the river sample showed 2-4 times higher values after the inflow of discharged water from G-1-PSTP. Therefore, it could be thought other factors such as microorganisms influence the elevated NBOD levels. Through next-generation sequencing analysis, nitrifying microorganisms such as Nitrosomonas, Nitroga, and Nitrospira (Genus) were detected in rivers samples, especially, the proportion of them was the highest in river samples after the inflow of discharged water from G-1-PSTP. These results indicated the effects of nitrifying microorganisms and NH3-N concentrations as important limiting factors on the increased NBOD levels in the rivers. Taken together, comprehensive strategies are needed not only to reduce the NH3-N concentration of discharged water but also to control discharged nitrifying microorganisms to effectively reduce the NBOD levels in the downstream of the Yeongsan river where discharged water from G-1-PSTP flows.

A Study of Energy Security Cooperation and its Integration Potential in South America through Brazilian Leadership (남미지역 에너지안보 협력과 통합 가능성 연구 : 브라질의 리더십 역할 고찰)

  • Ha, Sang-Sub
    • Journal of International Area Studies (JIAS)
    • /
    • v.15 no.1
    • /
    • pp.83-108
    • /
    • 2011
  • South America has vast energy resources with the renewable and non-renewable sources. However, many countries in the region are unable to guarantee adequate energy security both of energy supply and demand. Currently the possibility of energy security is high through regional energy integration based on the potential economic benefits. The difference of regulation system with the individual countries in the region impose strong barriers to integration process. Security of energy supply and its demand as well is fundamental issues in this region and regional energy cooperation is essential for getting rid of the insecurity of energy supplies. Despite of this problem, currently Latin American countries made a great effort to make multilateral energy security regime through projecting great energy infrastructure network(e.g. IIRSA) or mechanism especially in South America, which can give countries access to the region's reserve supplies by providing regulations and pricing mechanism with a shared energy market in this region. Brazil's active leading in the formulation of such movement toward energy security integration and participation of energy infrastructure network is good initiative to enforce this great energy security change. Politically and economically, Brazil's geographical position and the level of market size and oil and natural gas resources, in addition the leadership in renewable energy sources make it a sound candidate to take over the coordination of the secure integration of region's energy market. However, on the conditions of existing many obstacles such as, control of the output of the region's power plant, energy flows, the environmental matter within local community must be overcome to make more advance process and steps. Finally, to secure more institutional approach, this region must settle regional disputes resolution regime urgently.

Effectiveness of a Wave Resonator under Short-period Waves and Solitary Waves (공진장치를 이용한 단주기파랑과 고립파의 제어)

  • Lee, Kwang Ho;Jeong, Seong Ho;Jeong, Jin Woo;Kim, Do Sam
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.30 no.1B
    • /
    • pp.89-100
    • /
    • 2010
  • The performance evaluation of a conventional Wave Resonator at the entrance of harbors against solitary wave has been performed using 3D numerical wave flume. A wave resonator has been designed for the attenuation of the transmitted wave energy by trapping the short periodic incident waves only. In this study, however, the controlled performance of the wave resonator by its various widths has been numerically investigated for solitary waves. Source distribution method based on the Green function and the 3D one-field Model for immiscible TWO-Phase flows (TWOPM-3D) using 3D numerical wave flume were used for the short-periodic waves and the solitary waves, respectively, and these models were verified through the comparisons with the previous experimental and numerical results by other researchers. It was confirmed that the wave resonator is effective enough to control the solitary waves as well as the periodic waves when it compares with the case of no resonance system. Further, it was found that there is the optimal width of a wave resonator to attenuate the target solitary waves.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.26 no.12
    • /
    • pp.605-619
    • /
    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.