• Title, Summary, Keyword: Nozzle Pressure

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Fabrication of PCL Scaffolds According to Various Pore Patterns Using Polymer Deposition System and Design of Experiments (폴리머 적층 시스템과 실험계획법을 이용한 다양한 공극 패턴에 따른 PCL 인공지지체의 제작 연구)

  • Sa, Min-Woo;Choi, Sun-Woong;Lee, Jae-Wook;Kim, Jong Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.7
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    • pp.645-653
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    • 2017
  • In bone tissue engineering, polycaprolactone (PCL) is one of the most widely used biomaterials in the manufacturing of scaffolds as a synthetic polymer having biodegradability and biocompatibility. The strut width in the fabrication of scaffolds is an important part of tissue regeneration in in-vitro and in-vivo experiments, because it affects not only the pore size but also the porosity. In this study, we used polymer deposition system (PDS) and design of experiments (DOE) to explore the optimal process conditions to achieve a systematic and efficient scaffold manufacturing process, using temperature, pressure, scan velocity, and nozzle tip height as the parameters for the experiments. The aim of this research was to fabricate a 3D PCL scaffold having a uniform strut width of $150{\mu}m$ using DOE; it was proved that the strut width was constant in all the experimental groups by fabricating the PCL scaffolds according to various pore patterns as well as one pore pattern.

An Experimental Study on Flow Distributor Performance with Single-Train Passive Safety System of SMART-ITL (SMART-ITL 1 계열 피동안전계통을 이용한 유동분사기 성능에 대한 실험연구)

  • Ryu, Sung Uk;Bae, Hwang;Yang, Jin Hwa;Jeon, Byong Guk;Yun, Eun Koo;Kim, Jaemin;Bang, Yoon Gon;Kim, Myung Joon;Yi, Sung-Jae;Park, Hyun-Sik
    • Journal of Energy Engineering
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    • v.25 no.4
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    • pp.124-132
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    • 2016
  • In order to estimate the effect of flow distributors connected to an upper nozzle of CMT(Core Makeup Tank) on the thermal-hydraulic characteristics in the tank, a simplified 2 inch Small Break Loss of Coolant Accident(SBLOCA) was simulated by skipping the decay power and Passive Residual Heat Removal System(PRHRS) actuation. The CMT is a part of safety injection systems in the SMART (System Integrated Modular Advanced Reactor). Each test was performed with reliable boundary conditions. It means that the pressure distribution is provided with repeatable and reproducible behavior during SBLOCA simulations. The maximum flow rates were achieved at around 350 seconds after the initial opening of the isolation valve installed in CMT. After a short period of decreased flow rate, it attained a steady injection flow rate after about 1,250 seconds. This unstable injection period of the CMT coolant is due to the condensation of steam injected into the upper part of CMT. The steady injection flow rate was about 8.4% higher with B-type distributor than that with A-type distributor. The gravity injection during hot condition tests were in good agreement with that during cold condition tests except for the early stages.

The Study on the Countermeasure Plans about Leakage, Explosion and Fire Accidents of Atmospheric Storage Tank (옥외저장탱크 누출, 폭발 및 화재사고 대응방안에 관한 고찰)

  • Lee, Gab-Kyoo
    • Fire Science and Engineering
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    • v.30 no.6
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    • pp.48-56
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    • 2016
  • A crude oil leakage from a large atmospheric storage tank occurred on 4 April 2014 at 14:50 in Ulsan City, while storing the crude oil in the tank. Emergency Rescue Control Group was deployed in the scene. The company, Fire Service Headquarters and associated agencies got together in Command Post (CP) for discussing an effective corresponding strategy. Many solution plans were drafted in the debate such as power down, stopping the facilities, checking the density of inflammable gas, suppressing oil evaporation, moving the leaked crude oil to a nearby tank and a processing plant and avoiding marine pollution. All the solutions were carried out in cooperation with several agencies and partners. The oil leakage accident was successfully settled up within the process of responding, The Fire Service Headquarters and the company thought that the most important thing was the suppression of oil evaporation and the elimination of ignition source. With Fire Service Headquarters and several agencies' every effort, an explosion and a fire didn't occurred in the scene. This study suggest the improvement of the operating system in Emergency Rescue Control Group in case of petroleum leakage, explosion and fire accidents of atmospheric storage tank, different from a ordinary disaster. Assuming that petroleum leakage in atmospheric storage tank develop the explosion and fire accidents, the spreading speed of the flame and the burning time was experimented and compared with each other. Furthermore, this study concentrates on the effective field response plan prepared for the afterward explosion and fire accidents from petroleum leak in a storage tank, with the database experimented and analyzed in accordance with the angle of radiation in the foam nozzle and the pressure of pumping in a fire engine.

A Numerical Study on the Geometry Optimization of Internal Flow Passage in the Common-rail Diesel Injector for Improving Injection Performance (커먼레일 디젤인젝터의 분사성능 개선을 위한 내부유로형상 최적화에 관한 수치적 연구)

  • Moon, Seongjoon;Jeong, Soojin;Lee, Sangin;Kim, Taehun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.2
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    • pp.91-99
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    • 2014
  • The common-rail injectors are the most critical component of the CRDI diesel engines that dominantly affect engine performances through high pressure injection with exact control. Thus, from now on the advanced combustion technologies for common-rail diesel injection engine require high performance fuel injectors. Accordingly, the previous studies on the numerical and experimental analysis of the diesel injector have focused on a optimum geometry to induce proper injection rate. In this study, computational predictions of performance of the diesel injector have been performed to evaluate internal flow characteristics for various needle lift and the spray pattern at the nozzle exit. To our knowledge, three-dimensional computational fluid dynamics (CFD) model of the internal flow passage of an entire injector duct including injection and return routes has never been studied. In this study, major design parameters concerning internal routes in the injector are optimized by using a CFD analysis and Response Surface Method (RSM). The computational prediction of the internal flow characteristics of the common-rail diesel injector was carried out by using STAR-CCM+7.06 code. In this work, computations were carried out under the assumption that the internal flow passage is a steady-state condition at the maximum needle lift. The design parameters are optimized by using the L16 orthogonal array and polynomial regression, local-approximation characteristics of RSM. Meanwhile, the optimum values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance (ANOVA). In addition, optimal design and prototype design were confirmed by calculating the injection quantities, resulting in the improvement of the injection performance by more than 54%.

Patent Technologies for Reducing Micro-Dust (미세먼지 저감을 위한 특허기술들)

  • Cho, Taejun;Kim, Tae-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.2
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    • pp.9-14
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    • 2020
  • Four developed patents have applied for a new type of Composite Cyclone Scrubber followed by the previous research (Cho and Kim, 2017), including dust reducing fan with filters. Regarding target installation and maintenance cost, 64% reduction for investment costs (6.2 billion won vs. 17 billion won) compared to existing road pollution reduction system, while social benefit costs increase by 43% compared to existing road pollution reduction measures (72.6 billion won vs. 50.8 billion won). The composition of the device is an air blower type spiral guide vane, and an injection pressure collecting dust efficiency. A nozzle varies Injection angle and contact range, spray liquid species (waterworks, salty water). The proposed patent tests are circulation water Time-by-Time Spray and collected 41.4% more increased micro dust since the sprayed water meets contaminated gas due to the 45° degree colliding, which is 141% increased conventional dust collector. (Ratio of collection over 85%). As regards the source of collection liquid, circulated rainwater and well water, we expect a huge amount of energy and economically saved eco-friendly system in our patent. Finally, the guided vane and metal filter reduced over 90% micro-dust, while sprayed water cleans the vane and filters, resultantly minimizing the maintenance budget. The preliminary evaluations of the developed design make it possible to reduce not only cheaper maintenance budget due to the characteristic water spraying but the cost of water comes from mainly rain and underground.

Influence of the Amount of Conductive Paste on the Electrical Characteristics of c-Si Photovoltaic Module (전도성 페이스트 도포량 변화에 따른 결정질 태양광 모듈의 전기적 특성에 대한 영향성 분석)

  • Kim, Yong Sung;Lim, Jong Rok;Shin, Woo Gyun;Ko, Suk-Whan;Ju, Young-Chul;Hwang, Hye Mi;Chang, Hyo Sik;Kang, Gi-Hwan
    • Korean Journal of Materials Research
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    • v.29 no.11
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    • pp.720-726
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    • 2019
  • Recently, research on cost reduction and efficiency improvement of crystalline silicon(c-Si) photovoltaic(PV) module has been conducted. In order to reduce costs, the thickness of solar cell wafers is becoming thinner. If the thickness of the wafer is reduced, cracking of wafer may occur in high temperature processes during the c-Si PV module manufacturing process. To solve this problem, a low temperature process has been proposed. Conductive paste(CP) is used for low temperature processing; it contains Sn57.6Bi0.4Ag component and can be electrically combined with solar cells and ribbons at a melting point of $150^{\circ}C$. Use of CP in the PV module manufacturing process can minimize cracks of solar cells. When CP is applied to solar cells, the output varies with the amount of CP, and so the optimum amount of CP must be found. In this paper, in order to find the optimal CP application amount, we manufactured several c-Si PV modules with different CP amounts. The amount control of CP is fixed at air pressure (500 kPa) and nozzle diameter 22G(outer diameter 0.72Ø, inner 0.42Ø) of dispenser; only speed is controlled. The c-Si PV module output is measured to analyze the difference according to the amount of CP and analyzed by optical microscope and Alpha-step. As the result, the optimum amount of CP is 0.452 ~ 0.544 g on solar cells.

A Study on the Development of Fire Extinguishing Agent and Extinguishing System for ESS Fire (ESS 화재전용 소화약제 및 소화시스템 개발에 관한 연구)

  • Lee, Yeon-Ho;Lee, Joo-Hyung;Kim, Soo-Jin;Chon, Sung-Ho;Choi, Byoung-Chul;Oh, Seung-Ju;Kim, Si-Kuk
    • Fire Science and Engineering
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    • v.34 no.2
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    • pp.147-155
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    • 2020
  • This paper presents a study on the development of a fire extinguishing agent and extinguishing system for an energy storage system (ESS) fire. The fire extinguishing agent designed to extinguish an ESS fire is a highly permeable fire extinguisher that reduces the surface tension and viscosity while bringing about cooling action. This is the main extinguishing effect of this type of wetting agent, which displays the characteristics of fire extinguishing agents used for penetrating the battery cells inside the ESS module. For the fire extinguishing system, a local application system was designed to suppress fire on a rack-by-rack basis. A 360° rotating nozzle was inserted into the rear hall of the ESS module, and general nozzles were installed in the rack to maximize the fire extinguishing effect. The fire extinguishing agent was strongly discharged by virtue of the gas release pressure. Experiments on fire suppression performance with ESS module 1 unit and module 3 units showed that all visible flames were extinguished in 8 s and 9 s, respectively, by the fire extinguishing agent. In addition, based on confirming reignition for 600 s after the fire extinguishing agent was exhausted, it was confirmed that the ESS fire was completely extinguished without reignition in all fire suppression performance experiments.

Remote field Eddy Current Technique Development for Gap Measurement of Neighboring Tubes of Nuclear Fuel Channel in Pressurized Heavy Water Reactor (중수로 핵연료채널과 인접관의 간격측정을 위한 원거리장 와전류검사 기술개발)

  • Jung, H.K.;Lee, D.H.;Lee, Y.S.;Huh, H;Cheong, Y.M.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.2
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    • pp.164-170
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    • 2004
  • Liquid Injection Nozzle(LIN) tube and Calandria tube(CT) in pressurized Heavy Water Reactor (PHWR) are .ross-aligned horizontally. These neighboring tubes can contact each other due to the sag of the calandria tube resulting from the irradiation creep and thermal creep, and fuel load, etc. In order to judge the contact which might be the safety concern, the remote field eddy current (RFEC) technology is applied for the gap measurement in this paper. LIN can be detected by inserting the RFEC probe into pressure tube (PT) at the crossing point directly. To obtain the optimal conditions of the RFEC inspection, the sensitivity, penetration and noise signals are considered simultaneously. The optimal frequency and coil spacing are 1kHz and 200mm respectively. Possible noises during LIN signal acquisition are caused by lift-off, PT thickness variation, and gap variation between PT and CT. The simulated noise signals were investigated by the Volume Integral Method(VIM). Signal analysis on the voltage plane describes the amplitude and shape of LIN and possible defects at several frequencies. All the RFEC measurements in the laboratory were done in variance with the CT/LIN gap and showed the relationship between the LIN gap and the signal parameters by analyzing the voltage plane signals.

Effects of Swirl and Combustion Parameters on the Performance and Emission in a Turbocharged D.1. Diesel Engine (선회유동 및 연소인자가 터보과급 디젤엔진의 성능 및 배기가스특성에 미치는 영향)

  • 윤준규;차경옥
    • Journal of Energy Engineering
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    • v.11 no.2
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    • pp.90-98
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    • 2002
  • The effects of swirl and combustion parameters on the performance and emission in a turbo-charged D.I. diesel engine of the displacement 9.4L were studied experimentally in this paper. Generally the swirl in the combustion process of diesel engine promotes mixing of the injection fuel and the intake air. It is a major factor to improve the engine performance because the fuel consumption and NO$_{x}$ is trade-off according to the high temperature and high pressure of combustion gas in a turbocharged D.I. diesel engine, it's necessary to thinking over the intake and exhaust system, the design of combustion bowl and so on. In order to choose a turbocharger of appropriate capacity. As a result of steady flow test, when the swirl ratio is increased, the mean flow coefficient is decreased, whereas the gulf factor is increased. Also, through engine test its can be expected to meet performance and emissions by optimizing the main parameter's; the swirl ratio is 2.43, injection timing is BTDC 13$^{\circ}$ CA, compression ratio is 16, combustion bowl is re-entrant 5$^{\circ}$, nozzle hole diameter is $\Phi$0.28*6, turbocharger is GT40 model which are compressor A/R 0.58 and turbine A/R 1.19.

TREATMENT OF COMPOSITE RESIN RESTORATION WITH THE AIR ABRASIVE TECHNIQUE (Air abrasive technique을 이용한 복합레진 수복 증례)

  • Lee, Chang-Woo;Jang, Ki-Taeg;Lee, Sang-Hoon;Hahn, Se-Hyun
    • JOURNAL OF THE KOREAN ACADEMY OF PEDTATRIC DENTISTRY
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    • v.24 no.4
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    • pp.763-770
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    • 1997
  • The air abrasive technique is a non-mechanical method by which teeth are treated before restoration and stains and calculi are removed from tooth surfaces using the kinetic energy of small particles. The air abrasive technique in dentistry was first introduced in the 1950's with as instrument called 'Airdent'. But, as the main restorative materials of the period were amalgam and gold, and the instrument's inability to control the flow of particles caused the particles to be spread throughout the clinics, widespread use was not possible. In the 1990's, as these techincal problems were solved and more interest in new restorative materials rose in an effort to preserve sound tooth structure, new developements took place in instruments related to the air abrasive technique. The air abrasive technique produces less pressure, vibration and heat that might cause patient discomfort and facilitates the preservation of sound tooth structure. It also reduces the need for anesthesia and is less harmful to the pulp. Other advantages include increase in dentin bonding strength of composite resin, lower possibility of saliva contamination and maintenance of a dry field. But there is not direct contact between the nozzle and the tooth, the operator cannot use his or her tactile sense and must rely solely upon visual input. Other disadvantages are: the tooth preparation depends on the operator's ability; alpha-alumina particles, after bouncing off the tooth surface, cause damage to dental mirrors; the equipment is expensive and takes up a certain amount of space in the clinic. The author conducted case report using the air abrasive technique on patient visiting the Department of Pediatric Dentistry at Seoul National University Dental Hospital and arrived at the following conclusions. 1. The tooth preparation capability of different air abrasive devices varied widely among manufacturers. 2. It was more effective in treating early caries lesions and stains compared to lesions where caries had already progressed to produce soft dentin. 3. The cold stream and noise caused by the evacuation system was a major cause of discomfort to pediatric patients. 4. As there is no direct contact with tooth surface when using the air abrasive technique for tooth preparation, considerable experience and skill is required for proper tooth preparation.

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