• Title/Summary/Keyword: Latent efficiency

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An Experimental Study on the Water Evaporation Conditions of the Enclosed Tank (밀폐용기내의 물의 저압 증발 최적조건에 관한 실험적 연구)

  • Kim, S.H.;Shin, Y.S.;Lee, Y.W.;Chung, H.S.;Jeong, H.M.
    • Journal of Power System Engineering
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    • v.8 no.1
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    • pp.41-47
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    • 2004
  • Cooling towers are widely used not only for cooling products and equipment in manufacturing process but HVAC(Heating, Ventilation and Air Conditioning) system. As a cooling tower is the terminal apparatus which discharges heat from industrial process, the efficiency of heat exchange in the cooling tower greatly affects to the overall performance of a thermal system. In this paper, we constituted a new water cooling system by using a Latent heat of evaporation in an enclosed tank, and this system is consisted of an enclosed vacuum tank and water driven ejector system. Several experimental cases were carried out for improvement methods of high vacuum pressure and water cooling characteristics. The ejector performance was tested in case of water temperature variations that flows into the ejector. Based on the vacuum pressure by water driven ejector, the water cooling characteristics were investigated for the vaporized air condensing effects.

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A Study on the Standard of ESS Requirement based on MIL-HDBK-344A (MIL-HDBK-344A 기반의 ESS 요구사항 표준안 연구)

  • Kim, Byung-Jun;Kim, Jin-Sung
    • The Journal of the Korea institute of electronic communication sciences
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    • v.15 no.2
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    • pp.335-342
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    • 2020
  • ESS(Environmental Stress Screening) is an important production process to remove 'latent defects' introduced in the production of products. Recently, ESS is included in QAR(Quality Assurance Report) as an essential quality assurance requirement for products in the defense business. However, depending on the author of the QAR or the classification of the weapon system, it is often identified that the content and form are different or important elements are omitted. Therefore, this paper proposes a MIL-HDBK-344A based quantitative ESS requirement standard to secure the consistency and completeness of QAR. and to make easier to calculate PE(Precipitation Efficiency), which is an indicator for identifying the latent defects elimination effect.

A Study on Combustion Characteristic with the Variation of Oxidizer phase in Hybrid Rocket Motor using PE/$N_2O$ (PE/$N_2O$ 하이브리드 로켓에서의 산화제 상 변화에 따른 연소특성 연구)

  • Lee, Jung-Pyo;Kim, Gi-Hun;Kim, Soo-Jong;Kim, Hak-Chul;Moon, Hee-Jang;Sung, Hong-Gye;Kim, Jin-Kon
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.2
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    • pp.46-53
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    • 2010
  • The purpose of this paper is to study combustion characteristics with the different phase of oxidizer in hybrid rocket combustion. HDPE(High Density Polyethylene) as fuel and $GN_2O$(Gas $N_2O$), $LN_2O$(Liquid $N_2O$) as oxidizer were used to perform the experiments. An investigation was performed for a change of the regression rate, pressure of combustion chamber and combustion efficiency according to the variation of oxidizer phase. In case of using $LN_2O$ as oxidizer, the regression rate is not significantly different from using $GN_2O$ as oxidizer. It is considered that combustion energy is much larger than latent heat energy which was used in the evaporation of liquid oxidizer. However propulsion performance efficiency for $LN_2O$ showed lower value than for $GN_2O$. By increasing the flow rate of liquid oxidizer, heat transfer needed for vaporization of liquid oxidizer was increased, which resulted in the growth of combustion instability.

A Study on the Cooling Characteristics Improvement of TMA-Water Clathrate Compound by Ethanol (에탄올에 의한 TMA-포접화합물의 냉각특성 개선에 대한 연구)

  • Lee, Jong-In;Kim, Chang-Oh
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.23-28
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    • 2007
  • This study aims to find out cooling characteristics of TMA(Tri-Methyl-Amine, $(CH_3)_3N$) 25wt%-water clathrate compound with ethanol($CH_3CH_2OH$) such as supercooling, phase change temperature and specific heat. For this purpose, ethanol is added as per weight concentration and cooling experiment is performed at $-6{\sim}-8^{\circ}C$, cooling heat source temperature, and it leads the following result. (1) Phase change temperature is decreased due to freezing point depression phenomenon. Especially, it is minimized as $3.8^{\circ}C$ according to cooling source temperature in case that 0.5wt% of ethanol is added. (2) If 0.5wt% of ethanol is added, average supercooling degree is $0.9^{\circ}C$ and minimum supercooling is 0.8, $0.7^{\circ}C$ according to cooling heat source temperature. The restraint effect of supercooling is shown. (3) Specific heat shows tendency to decrease if ethanol is added. It is $3.013{\sim}3.048\;kcal/kg^{\circ}C$ according to cooling heat source temperature if 0.5wt% of ethanol is added. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA 25wt%-water clathrate compound by adding additive, ethanol. This can lead to shorten refrigerator operation time of low temperature latent heat storage system and improve COP of refrigerator and efficiency of overall system. Therefore energy can be saved and efficiency can be improved much more.

Performance Improvement of Topic Modeling using BART based Document Summarization (BART 기반 문서 요약을 통한 토픽 모델링 성능 향상)

  • Eun Su Kim;Hyun Yoo;Kyungyong Chung
    • Journal of Internet Computing and Services
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    • v.25 no.3
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    • pp.27-33
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    • 2024
  • The environment of academic research is continuously changing due to the increase of information, which raises the need for an effective way to analyze and organize large amounts of documents. In this paper, we propose Performance Improvement of Topic Modeling using BART(Bidirectional and Auto-Regressive Transformers) based Document Summarization. The proposed method uses BART-based document summary model to extract the core content and improve topic modeling performance using LDA(Latent Dirichlet Allocation) algorithm. We suggest an approach to improve the performance and efficiency of LDA topic modeling through document summarization and validate it through experiments. The experimental results show that the BART-based model for summarizing article data captures the important information of the original articles with F1-Scores of 0.5819, 0.4384, and 0.5038 in Rouge-1, Rouge-2, and Rouge-L performance evaluations, respectively. In addition, topic modeling using summarized documents performs about 8.08% better than topic modeling using full text in the performance comparison using the Perplexity metric. This contributes to the reduction of data throughput and improvement of efficiency in the topic modeling process.

Optimum Conditions for Transformation of Synechocystis sp. PCC 6803

  • Zang, Xiaonan;Liu, Bin;Liu, Shunmei;Arunakumara, K.K.I.U.;Zhang, Xuecheng
    • Journal of Microbiology
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    • v.45 no.3
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    • pp.241-245
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    • 2007
  • This study was conducted to determine the optimal conditions for introduction of exogenous DNA into Synechocystis sp. PCC 6803. Of the three transformation techniques studied, electroporation, ultrasonic transformation and natural transformation, natural transformation showed the highest efficiency. Additionally, this study demonstrated that the higher plasmid concentration and longer homologous recombining fragments resulted in a greater number of transformants. For successful transformation, the lowest concentration of plasmid was $0.02\;{\mu}g/ml$, and the shortest homologous recombining fragment was 0.2 kb. Use of Synechocystis sp. PCC 6803 in the logarithmic growth phase resulted in two-fold higher transformation rate than that of the same organism when cells in the latent phase or the plateau phase were used for transformation. Pretreatment of the host strain, Synechocystis sp. PCC 6803, with EDTA (2 mM) for two days prior to transformation increased the transformation efficiency by 23%. Additionally, incubation of the cells and DNA for 5 h under light conditions increased the transformation efficiency by two orders of magnitude. Moreover, recovery treatment of the cells before they were plated onto antibiotic medium also increased the transformation efficiency.

A Human Function Deployment for Managing Human Factor in Korea railroad (국내 철도시스템에서 기능전개를 통한 인적요소 관리방안 연구)

  • Heo, Eun-Mee;Kim, Sa-Kil;Byun, Seong-Nam
    • Proceedings of the KSR Conference
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    • 2009.05a
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    • pp.1376-1382
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    • 2009
  • Railway system is a word that includes rolling stock, railway infrastructure and signalling System in passenger transfer and rail freight. This system get higher competitiveness in energy efficiency part than other transfer system. But it is comprehensive system has latent loss of lives and property by big accident. First of all, to control this comprehensive system and to confirm safety of it, we need human resource management. This research will suggest how to apply efficiency safety verification and certification system to railway system. human resource management systems is defined as three kinds that is recruitment and management, ensure personnel's competencies and fitness, activity of assigning suitable responsible person for work.

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Implementation of Improved Ice Particle Collision Efficiency in Takahashi Cloud Model (Takahashi 구름모형에서의 얼음입자 충돌효율 개선)

  • Lee, Hannah;Yum, Seong Soo
    • Atmosphere
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    • v.22 no.1
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    • pp.73-85
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    • 2012
  • The collision efficiency data for collision between graupel or hail particles and cloud drops that take into account the differences of particle density are applied to the Takahashi cloud model. The original setting assumes that graupel or hail collision efficiency is the same as that of the cloud drops of the same volume. The Takahashi cloud model is run with the new collision efficiency data and the results are compared with those with the original. As an initial condition, a thermodynamic profile that can initiate strong convection is provided. Three different CCN concentration values and therefore three initial cloud drop spectra are prescribed that represent maritime (CCN concentration = 300 $cm^{-3}$), continental (1000 $cm^{-3}$) and extreme continental (5000 $cm^{-3}$) air masses to examine the aerosol effects on cloud and precipitation development. Increase of CCN concentration causes cloud drop sizes to decrease and cloud drop concentrations to increase. However, the concentration of ice particles decreases with the increase of CCN concentration because small drops are difficult to freeze. These general trends are well captured by both model runs (one with the new collision efficiency data and the other with the original) but there are significant differences: with the new data, the development of cloud and raindrop formation are delayed by (1) decrease of ice collision efficiency, (2) decrease of latent heat from riming process and (3) decrease of ice crystals generated by ice multiplication. These results indicate that the model run with the original collision efficiency data overestimates precipitation rates.

Arc efficiency and kerf width in plasma arc cutting process (플라즈마 절단공정에서의 아아크 효율과 절단폭)

  • 노태정;나석주
    • Journal of Welding and Joining
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    • v.5 no.1
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    • pp.23-33
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    • 1987
  • Plasma arc cutting is a fusion cutting process in which a gas constricted arc is employed to produce high temperature, high velocity jet at the workpiece. Even though the plasma arc cutting has been wid¬ely used in the industry, very little work has been done on the analysis of the process. In this paper, the kerf width was numerically analyzed by soving the temperature distribution in base metal under consideration of the latent heat effect. In modelling the heat flow problem, the heat intensity of the plasma arc was assumed to have a Gaussion distribution in the transverse direction and expone¬ntially decreasing in the thickness direction. The thermal efficiency and the heat input ratio of the top surface were experimentally deterimned for various thickness and cutting conditions, and used in numerical calculation of the kerf width. The experimental results were in eonsiderabely good agreement with the theoretically predicted kerf width.

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A Study on the Way to Improve Efficiency of a Waste Heat Recovery System for an Automotive Engine (자동차 엔진용 폐열 회수 시스템의 효율 향상방안에 관한 연구)

  • Cha, Won-Sim;Choi, Kyung-Wook;Kim, Ki-Bum;Lee, Ki-Hyung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.4
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    • pp.76-81
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    • 2012
  • In recent, there are tremendous efforts to apply co-generation concept in automobile to improve its thermal efficiency. The co-generation is basically a simple Rankine Cycle that uses the waste heat from the engine exhaust and coolant for heat source. In spite of developed nano technology and advance material science, the bulky co-generation system is still a big concern in automotive application. Therefore, the system should be effectively designed not to add much weight on the vehicle, but the capacity of the waste heat recovery should be still large. With such a goal in mind, the system thermal efficiency was investigated in terms of the system operation condition and working fluid. This paper provides a direction for the optimal design of the automotive co-generation system.