• Title/Summary/Keyword: Regenerative system

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Performance Characteristics of a Combined Regenerative Ammonia-Water Based Power Generation Cycle Using LNG Cold Energy (LNG 냉열을 이용하는 암모니아-물 복합 재생 동력 사이클의 성능 특성)

  • Kim, Kyounghoon;Oh, Jaehyeong;Jeong, Youngguan
    • Journal of Hydrogen and New Energy
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    • v.24 no.6
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    • pp.510-517
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    • 2013
  • The ammonia-water based power generation cycle utilizing liquefied natural gas (LNG) as its heat sink has attracted much attention, since the ammonia-water cycle has many thermodynamic advantages in conversion of low-grade heat source in the form of sensible energy and LNG has a great cold energy. In this paper, we carry out thermodynamic performance analysis of a combined power generation cycle which is consisted of an ammonia-water regenerative Rankine cycle and LNG power generation cycle. LNG is able to condense the ammonia-water mixture at a very low condensing temperature in a heat exchanger, which leads to an increased power output. Based on the thermodynamic models, the effects of the key parameters such as source temperature, ammonia concentration and turbine inlet pressure on the characteristics of system are throughly investigated. The results show that the thermodynamic performance of the ammonia-water power generation cycle can be improved by the LNG cold energy and there exist an optimum ammonia concentration to reach the maximum system net work production.

Static Analysis of AT Feeding Systems considering the Limited Rise of Regenerative Voltage (회생 차량의 전압 상승 한도를 고려한 AT 급전시스템 정태해석)

  • Kim, B;Moon, Y.-H
    • Proceedings of the KSR Conference
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    • 2004.10a
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    • pp.1322-1327
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    • 2004
  • There are some previous studies that utilize constant impedance models or constant current models for electric trains to perform the static analysis of AT feeding systems. These mentioned models have some merits of linear systems but yield erroneous results because of the innate restraints of the models since linear models cannot represent the features of constant power in inverter-driven trains. From these reasons, it is suitable that the train be considered as a constant load model when it drives or as a constant source model when it applies regenerative brake. However, excessive rise of regenerative voltage during the braking may damage the vehicle itself and the feeding systems so the voltage must be restricted below a certain value. Keeping these facts in minds, we suggest new methods of analyzing AT feeding systems using the constant power models with the conditions of voltage constraints. The simulation results from a sample system using the proposed method illustrate both the states of system variables and the supply-demand relation of power among the trains and the systems very clearly, so it is believed that the proposed method yields more accurate results than conventional methods do.

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A Study on the LRE Thrust Chamber Regenerative Cooling Design (액체로켓엔진 추력실의 재생냉각 기관 설계)

  • Kim, Ji-Hoon;Park, Hee-Ho;Kim, Yoo;Hwang, Soo-Kwon
    • Journal of the Korean Society of Propulsion Engineers
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    • v.6 no.4
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    • pp.25-35
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    • 2002
  • A calculation procedure for designing LRE regenerative cooling system is introduced. In LRE thrust chamber, heat is transfered from the hot gas to the wall by convection and radiation, then conduction through the wall and finally convection to the liquid coolant. A cooling channel is designed on the basis of heat transfer rate calculated by using criterial method and integral method. The result is compared with existing Russian cooling channel design code. Also a design logic and quantitative effect of various parameters were introduced to help better understanding for those who is not familiar to LRE system.

Liquid Rocket Regerative Cooling (액체로켓의 재생냉각)

  • Kim Yoo
    • 한국전산유체공학회:학술대회논문집
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    • 2002.10a
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    • pp.1-7
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    • 2002
  • Liquid rocket regenerative cooling design procedure is introduced with the example of the 250 kg thrust, LOx/kerocine experimental test rocket system. The presentation may be useful for numerical analysists who have limited experiences with real rocket system.

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A Retrospective Study of Critical Success Factors in Regenerative Endodontic Treatment (재생근관치료의 성공에 영향을 미치는 결정 요인에 대한 후향적 연구)

  • Jeong, Hwakyong;Lee, Nanyoung;Lee, Sangho
    • Journal of the korean academy of Pediatric Dentistry
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    • v.44 no.1
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    • pp.47-55
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    • 2017
  • This study evaluated critical factors influencing the success of regenerative endodontic treatment for necrotic immature permanent teeth. The study enrolled patients who had regenerative endodontic treatment in a necrotic immature permanent tooth through 1-year follow-up. Possible explanatory variables related to the success rates for 46 teeth were age, gender, dental stage at the initial appointment, etiology, treatment information, and clinical and radiographic outcomes. The dental stage at the time of regenerative endodontic treatment did not influence the success rate. The success rate was significantly related to the etiology of the necrotic immature tooth. The success rate according to etiology decreased in the following order: dens evaginatus, caries, and trauma. There was also a significant difference according to the type of antimicrobial. The success rate was influenced by appropriate disinfection of the root canal system, provision of a scaffold, and coronal sealing. Above all, careful case selection is necessary for treating a necrotic immature permanent tooth, especially in cases of trauma.

Performance Prediction of Heat Regenerators with using Spheres: Relation between Heat Transfer and Pressure Drop (구형 축열체를 사용한 축열기의 성능예측: 압력손실과 열전달의 관계)

  • 조한창;조길원;이용국
    • Journal of Energy Engineering
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    • v.12 no.1
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    • pp.35-41
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    • 2003
  • Heat regenerator occupied by regenerative materials improves thermal efficiency of regenerative combustion system through the recovery of heat of exhaust gaset. By using one-dimensional two-phase fluid dynamics model, the unsteady thermal flow of heat regenerator with spherical particles, was numerically simulated to evaluate the heat transfer and pressure drop and thereby to suggest the parameter for designing heat regenerator. It takes about 7 hours for the steady state of the flow field in regenerator, in which heat absorption of regenerative particle is concurrent with the same magnitude of heat desorption. The regenerative particle experiences small temperature fluctuation below 10 K during the reversing process. The performance of thermal flow in heat regenerator varies with inlet velocity of exhaust gas and air, configuration of regenerator (cross-sectional area and length) and diameter of regenerative particle. As the gas velocity increases, the heat transfer between gas and particle enhances and with the increase the pressure losses. As particle diameter decreases, the air is preheated higher and the exhaust gases are cooled more with the increase of pressure losses.

Study of Fuel Consumption Characteristics and Regenerative Braking Recovery Rate in a TMED Type Parallel Hybrid Electric Vehicle (TMED방식 병렬형 하이브리드 차량의 회생제동 회수율 및 연비 특성 연구)

  • Chung, Jin Ho;Kim, Jin Su;Kim, Ju Whan;Lee, Jin Wook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.8
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    • pp.485-494
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    • 2016
  • In this work, we conducted a study of fuel consumption characteristics and regenerative braking recovery rate by conducting an experiment using a TMED type parallel hybrid electric vehicle. As regenerative braking technology is considered essential to improve the energy efficiency of the hybrid vehicle, it is necessary to conduct research on the regenerative braking system. Therefore, the electrical characteristics, current balance, and fuel consumption were investigated using an EC type chassis dynamometer with experimental conditions as per IM240 mode. From the results, it was observed that when the initial SOC condition was lower, the engine operating time of the hybrid vehicle increased, and the energy efficiency decreased. While operating in the driving mode characteristics condition and the driving characteristics condition, the difference in the average fuel consumption was not significant. However, after completion of the experiment, there was a difference in the engine operation.

Effects of gamma-aminobutyric acid and piperine on gene regulation in pig kidney epithelial cell lines

  • Shin, Juhyun;Lee, Yoon-Mi;Oh, Jeongheon;Jung, Seunghwa;Oh, Jae-Wook
    • Asian-Australasian Journal of Animal Sciences
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    • v.33 no.9
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    • pp.1497-1506
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    • 2020
  • Objective: Gamma-aminobutyric acid (GABA) and piperine (PIP) are both nutritional supplements with potential use in animal diets. The purpose of this study is to investigate the effect of GABA and/or PIP treatment on the gene expression pattern of a pig kidney epithelial cell line. Methods: LLCPK1 cells were treated with GABA, PIP, or both, and then the gene expression pattern was analyzed using microarray. Gene ontology analysis was done using GeneOntology (Geneontology.org), and validation was performed using quantitative real-time polymerase chain reaction. Results: Gene ontology enrichment analysis was used to identify key pathway(s) of genes whose expression levels were regulated by these treatments. Microarray results showed that GABA had a positive effect on the transcription of genes related to regulation of erythrocyte differentiation and that GABA and PIP in combination had a synergistic effect on genes related to immune systems and processes. Furthermore, we found that effects of GABA and/or PIP on these selected genes were controlled by JNK/p38 MAPK pathway. Conclusion: These results can improve our understanding of mechanisms involved in the effect of GABA and/or PIP treatment on pig kidney epithelial cells. They can also help us evaluate their potential as a clinical diagnosis and treatment.

Novel Discovery of LINE-1 in a Korean Individual by a Target Enrichment Method

  • Shin, Wonseok;Mun, Seyoung;Kim, Junse;Lee, Wooseok;Park, Dong-Guk;Choi, Seungkyu;Lee, Tae Yoon;Cha, Seunghee;Han, Kyudong
    • Molecules and Cells
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    • v.42 no.1
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    • pp.87-95
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    • 2019
  • Long interspersed element-1 (LINE-1 or L1) is an autonomous retrotransposon, which is capable of inserting into a new region of genome. Previous studies have reported that these elements lead to genomic variations and altered functions by affecting gene expression and genetic networks. Mounting evidence strongly indicates that genetic diseases or various cancers can occur as a result of retrotransposition events that involve L1s. Therefore, the development of methodologies to study the structural variations and interpersonal insertion polymorphisms by L1 element-associated changes in an individual genome is invaluable. In this study, we applied a systematic approach to identify human-specific L1s (i.e., L1Hs) through the bioinformatics analysis of high-throughput next-generation sequencing data. We identified 525 candidates that could be inferred to carry non-reference L1Hs in a Korean individual genome (KPGP9). Among them, we randomly selected 40 candidates and validated that approximately 92.5% of non-reference L1Hs were inserted into a KPGP9 genome. In addition, unlike conventional methods, our relatively simple and expedited approach was highly reproducible in confirming the L1 insertions. Taken together, our findings strongly support that the identification of non-reference L1Hs by our novel target enrichment method demonstrates its future application to genomic variation studies on the risk of cancer and genetic disorders.

Effect of severe acute respiratory syndrome coronavirus 2 infection during pregnancy in K18-hACE2 transgenic mice

  • Byeongseok, Kim;Ki Hoon, Park;Ok-Hee, Lee;Giwan, Lee;Hyukjung, Kim;Siyoung, Lee;Semi, Hwang;Young Bong, Kim;Youngsok, Choi
    • Animal Bioscience
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    • v.36 no.1
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    • pp.43-52
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    • 2023
  • Objective: This study aimed to examine the influence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on pregnancy in cytokeratin-18 (K18)-hACE2 transgenic mice. Methods: To determine the expression of hACE2 mRNA in the female reproductive tract of K18-hACE2 mice, real-time polymerase chain reaction (RT-PCR) was performed using the ovary, oviduct, uterus, umbilical cord, and placenta. SARS-CoV-2 was inoculated intranasally (30 μL/mouse, 1×104 TCID50/mL) to plug-checked K18-hACE2 homozygous female mice at the pre-and post-implantation stages at 2.5 days post-coitum (dpc) and 15.5 dpc, respectively. The number of implantation sites was checked at 7.5 dpc, and the number of normally born pups was investigated at 20.5 dpc. Pregnancy outcomes, including implantation and childbirth, were confirmed by comparison with the non-infected group. Tissues of infected mice were collected at 7.5 dpc and 19.5 dpc to confirm the SARS-CoV-2 infection. The infection was identified by performing RT-PCR on the infected tissues and comparing them to the non-infected tissues. Results: hACE2 mRNA expression was confirmed in the female reproductive tract of the K18-hACE2 mice. Compared to the non-infected group, no significant difference in the number of implantation sites or normally born pups was found in the infected group. SARS-CoV-2 infection was detected in the lungs but not in the female reproductive system of infected K18-hACE2 mice. Conclusion: In K18-hACE2 mice, intranasal infection with SARS-CoV-2 did not induce implantation failure, preterm labor, or miscarriage. Although the viral infection was not detected in the uterus, placenta, or fetus, the infection of the lungs could induce problems in the reproductive system. However, lung infections were not related to pregnancy outcomes.