• Title/Summary/Keyword: component state test

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Uniaxial and Biaxial Flexural Strength of Plain Concrete using Optimum Specimen Configuration (최적실험체 제원에 의한 콘크리트의 일축 및 이축 휨인장강도)

  • Oh, Hongseob;Zi, Goangseup
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2A
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    • pp.185-191
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    • 2010
  • Because the concrete crack that is the reason of the serviceability and durability degradation of concrete structure can be arisen from either the stress magnitude and gradient or other structural and material defects, the crack strength of concrete is hard to accurately evaluate. Especially, stress-state in concrete plate components such as rigid pavement and long span slab is biaxial flexure stress, and the flexural strength of those component may be different than the traditional rupture modulus of concrete subjected to uniaxial stress. In this study, an experimental investigation to assess of mechanical behavior under uniaxial and biaxial flexure stress is conducted and the proposed optimum specimen configuration is adopted. From the test, the modulus of rupture under uniaxial and biaxial stress are decreased as the size of aggregate or specimen is larger. And biaxial flexure strength of concrete specimens is varied from 39.5 to 99.2% as compared with that of uniaxial strength, and the biaxial strength of specimen with 20mm aggregate size is only 76% of uniaxial strength.

Temperature Prediction of Cylinder Components in Medium-Speed Diesel Engine Using Conjugate Heat Transfer Analysis (복합 열전달 해석을 이용한 중속 디젤엔진 실린더 부품 온도 분포 예측)

  • Choi, Seong Wook;Yoon, Wook Hyoen;Park, Jong Il;Kang, Jeong Min;Park, Hyun Joong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.8
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    • pp.781-788
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    • 2013
  • Predicting the engine component temperature is a basic step to conduct structural safety evaluation in medium-speed diesel engine design. Recent trends such as increasing power density and performance necessitate more effective thermal management of the engine for achieving the desired durability and reliability. In addition, the local temperatures of several engine components must be maintained in the proper range to avoid problems such as low- or high-temperature corrosion. Therefore, it is very important to predict the temperature distribution of each engine part accurately in the design stage. In this study, the temperature of an engine component is calculated by using steady-state conjugate heat transfer analysis. A proper approach to determine the thermal load distribution on the thermal boundary area is suggested by using 1D engine system analysis, 3D transient CFD results, and previous experimental data from another developed engine model. A Hyundai HiMSEN engine having 250-mm bore size was chosen to validate the analysis procedure. The predicted results showed a reasonable agreement with experimental results.

Structure and Growth of Tin Whisker on Leadframe with Lead-free Solder Finish (무연솔더 도금된 리드프레임에서 Sn 위스커의 성장과 구조)

  • Kim Kyung-Seob;Leem Young-Min;Yu Chong-Hee
    • Journal of the Microelectronics and Packaging Society
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    • v.11 no.3 s.32
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    • pp.1-7
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    • 2004
  • Tin plating on component finishes may grow whiskers under certain conditions, which may cause failures in electronics equipment. To protect the environment, 'lead-free' among component finishes is being promoted worldwide. This paper presents the evaluation results of whiskers on two kinds of lead-free plating materials at the plating temperature and under the reliability test. The rising plating temperature caused increasing the size of plating grain and shorting the growth of whisker. The whisker was grown under the temperature cycling the bent type in matt Sn plating and striated type in malt Sn-Bi. The whisker growth in Sn-Bi plating was shorter than that in Sn plating. In FeNi42 leadframe, the $7.0{\~}10.0{\mu}m$ diameter and the $25.0{\~}45.0{\mu}m$ long whisker was grown under 300 cycles. In the 300 cycles of Cu leadframe, only the nodule(nuclear state) grew on the surface, and in the 600 cycles, a $3.0{\~}4.0{\mu}m$ short whisker grew. After 600 cycles, the ${\~}0.34{\mu}m$ thin $Ni_3Sn_4$ formed on the Sn-plated FeNi42. However, we observed the amount of $0.76{\~}1.14{\mu}m$ thick $Cu_6Sn_5$ and ${\~}0.27{\mu}m$ thin $Cu_3Sn$ intermetallics were observed between the Sn and Cu interfaces. Therefore, the main growth factor of a whisker is the intermetallic compound in the Cu leadframe, and the coefficient of thermal expansion mismatch in FeNi42.

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BEEF MEAT TRACEABILITY. CAN NIRS COULD HELP\ulcorner

  • Cozzolino, D.
    • Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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    • 2001.06a
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    • pp.1246-1246
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    • 2001
  • The quality of meat is highly variable in many properties. This variability originates from both animal production and meat processing. At the pre-slaughter stage, animal factors such as breed, sex, age contribute to this variability. Environmental factors include feeding, rearing, transport and conditions just before slaughter (Hildrum et al., 1995). Meat can be presented in a variety of forms, each offering different opportunities for adulteration and contamination. This has imposed great pressure on the food manufacturing industry to guarantee the safety of meat. Tissue and muscle speciation of flesh foods, as well as speciation of animal derived by-products fed to all classes of domestic animals, are now perhaps the most important uncertainty which the food industry must resolve to allay consumer concern. Recently, there is a demand for rapid and low cost methods of direct quality measurements in both food and food ingredients (including high performance liquid chromatography (HPLC), thin layer chromatography (TLC), enzymatic and inmunological tests (e.g. ELISA test) and physical tests) to establish their authenticity and hence guarantee the quality of products manufactured for consumers (Holland et al., 1998). The use of Near Infrared Reflectance Spectroscopy (NIRS) for the rapid, precise and non-destructive analysis of a wide range of organic materials has been comprehensively documented (Osborne et at., 1993). Most of the established methods have involved the development of NIRS calibrations for the quantitative prediction of composition in meat (Ben-Gera and Norris, 1968; Lanza, 1983; Clark and Short, 1994). This was a rational strategy to pursue during the initial stages of its application, given the type of equipment available, the state of development of the emerging discipline of chemometrics and the overwhelming commercial interest in solving such problems (Downey, 1994). One of the advantages of NIRS technology is not only to assess chemical structures through the analysis of the molecular bonds in the near infrared spectrum, but also to build an optical model characteristic of the sample which behaves like the “finger print” of the sample. This opens the possibility of using spectra to determine complex attributes of organic structures, which are related to molecular chromophores, organoleptic scores and sensory characteristics (Hildrum et al., 1994, 1995; Park et al., 1998). In addition, the application of statistical packages like principal component or discriminant analysis provides the possibility to understand the optical properties of the sample and make a classification without the chemical information. The objectives of this present work were: (1) to examine two methods of sample presentation to the instrument (intact and minced) and (2) to explore the use of principal component analysis (PCA) and Soft Independent Modelling of class Analogy (SIMCA) to classify muscles by quality attributes. Seventy-eight (n: 78) beef muscles (m. longissimus dorsi) from Hereford breed of cattle were used. The samples were scanned in a NIRS monochromator instrument (NIR Systems 6500, Silver Spring, MD, USA) in reflectance mode (log 1/R). Both intact and minced presentation to the instrument were explored. Qualitative analysis of optical information through PCA and SIMCA analysis showed differences in muscles resulting from two different feeding systems.

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Effects of Eisenia Bicyclis Extracts and Pill on Blood Glucose and Lipid Profile in Streptozotocin-Induced Diabetic Mice (당뇨 생쥐에서 대황 추출물 및 정제환의 혈당과 지질 상태 개선 효과)

  • Cho, Sung-Hee;Park, So-Young;Choi, Sang-Won
    • Journal of Nutrition and Health
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    • v.41 no.6
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    • pp.493-501
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    • 2008
  • The objectives of this study were to investigate the antihyperglycemic and hypolipidmic effects of sea oak(Eisenia bicyclis, EB) in the diabetic state and to examine the appropriateness of formulated EB pill for the effects. The various test materials obtained from EB were included in the experimental diets with 15% fat/0.5% cholesterol and fed to streptozotocin-induced diabetic mice weighing $35.0{\pm}0.7$ g for three weeks but not in the control diet having the same composition. The test materials were EB dry powder, water and ethanol extracts, viscozyme-treated EB water extract(EB enzyme-TR) and formulated pill containing dry powders of the EB, two kinds of seaweed, black soybean, sesame, onion and garlic. BG was measured during feeding period and serum insulin, lipids and thiobarbituric acid reactive substances(TBARS) and intestinal disaccharidase activities were measured at the end of the three weeks of the feeding. BG increase was lower in the EB enzyme-TR group after 10 days of the experimental diet but lower in EB pill group after 15 days compared with the control group. Serum insulin levels were higher in the EB enzyme-TR and EB pill groups. Intestinal maltase but not sucrase activity was higher in EB enzyme-TR fed group than the control group. Serum levels of total cholesterol and triglyceride were reduced by the EB enzyme-TR and EB pill compared with the control diet. HDL-/total cholesterol was increased by all EB test materials. Serum TBARS levels were lower in the EB ethanol extract and EB pill groups than in the control group and tended to be lower in the other EB groups. It is concluded that the EB enzyme-TR is the best among the EB preparations to be utilized as a functional component for improving blood glucose and lipid profile in diabetic subjects in the future. However, the pill containing low level of the EB powder is also regarded as effective and readily usable when formulated with the several other ingredients of the proper composition.(Supported by the RIC Program of MOCIE, Korea).

Experimental Study on Engineering Properties of Concrete Using Fluosilicates Based Composite (규불화염계 복합 조성물을 혼입한 콘크리트의 공학적 특성에 관한 실험적 연구)

  • Yang Il-Seung;Yun Hyun-Do;Kim Do-Su;Khil Bae-Su;Han Seung-Gu
    • Journal of the Korea Concrete Institute
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    • v.17 no.5 s.89
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    • pp.769-774
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    • 2005
  • Fluosilicic acid(H2SiF6) is recovered as an aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded H3PO4 or HF. Generally, fluosilicates are the salts produced by the reaction of H2SiF6 and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. This study was performed to know mechanical properties and watertightness using fluosilicates based composite made from fluosilicates and other compounds. Mix proportions for experiments were modulated at 0.45 of water to cement ratio and $0.0-2.0\%$ of adding ratio of fluosilicates based composite. Evaluation for mechanical properties of concrete was conducted to know fresh state of concrete, hardening state of concrete, and watertightness. Evaluation for watertightness of concrete was carried out permeability, absorption test and porosity analysis. In addition. Scanning Electron Microscopy(SEM) and Energy Dispersive X-Ray(EDX) used for investigating micro-structure and atomic component distributed in hardened concrete. It is ascertained that characteristics of mechanical properties and watertightness was more improved than non-added because of packing role of fluosilicates based composite and pozzolanic reaction of soluble $SiO_2$. Also, concrete added fluosilicates based composite had a tendency to delay setting time and only $0.5\%$ addition of fluosilicates based composite delayed 150 minutes compared with non-added.

Development of 2-kW Class C Amplifier Using GaN High Electron Mobility Transistors for S-band Military Radars (S대역 군사 레이더용 2kW급 GaN HEMT 증폭기 개발)

  • Kim, Si-Ok;Choi, Gil-Wong;Yoo, Young-Geun;Lim, Byeong-Ok;Kim, Dong-Gil;Kim, Heung-Geun
    • The Journal of the Korea institute of electronic communication sciences
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    • v.15 no.3
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    • pp.421-432
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    • 2020
  • This paper proposes a 2-kW solid-state power amplifier (SSPA) developed by employing power amplifier pallets designed using gallium-nitride high electron mobility transistors, which is used in S-band military radars and to replace existing traveling-wave tube amplifier (TWTA). The SSPA consists of a high-power amplifier module, which combines eight power amplifier pallets, a drive amplifier module, a digital control module, and a power supply unit. First, the amplifier module and component were integrated into a small package to account for space limitations; next, an on-board harmonic filter was fabricated to reject spurious components; and finally, an auto gain control system was designed for various duty ratios because recent military radar systems are all active phase radars using the pulse operation mode. The developed SSPA exhibited a max gain of 48 dB and an output power ranging between 63-63.6 dBm at a frequency band of 3.1 to 3.5 GHz. The auto gain control function showed that the output power is regulated around 63 dBm despite the fluctuation of the input power from 15-20 dBm. Finally, reliability of the developed system was verified through a temperature environment test for nine hours at high (55 ℃) / low (-40℃) temperature profile in accordance with military standard 810. The developed SSPA show better performance such as light weight, high output, high gain, various safety function, low repair cost and short repair time than existing TWTA.

Limit State Evaluation of Elbow Components Connected with Flexible Groove Joints (유동식 그루브 조인트로 연결된 엘보 요소의 한계상태 평가)

  • Sung-Wan Kim;Da-Woon Yun;Bub-Gyu Jeon;Dong-Uk Park;Sung-Jin Chang
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.28 no.3
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    • pp.91-99
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    • 2024
  • Piping systems are crucial facilities used in various industries, particularly in areas related to daily life and safety. Piping systems are fixed to the main structures of buildings and facilities but do not support external loads and serve as non-structural elements performing specific functions. Piping systems are affected by relative displacements owing to phase differences arising from different behaviors between two support points under seismic loads; this can cause damage owing to the displacement-dominant cyclic behavior. Fittings and joints in piping systems are representative elements that are vulnerable to seismic loads. To evaluate the seismic performance and limit states of fittings and joints in piping systems, a high-stroke actuator is required to simulate relative displacements. However, this is challenging because only few facilities can conduct these experiments. Therefore, element-level experiments are required to evaluate the seismic performance and limit states of piping systems connected by fittings and joints. This study proposed a method to evaluate the seismic performance of an elbow specimen that includes fittings and joints that are vulnerable to seismic loads in vertical piping systems. The elbow specimen was created by connecting straight pipes to both ends of a 90° pipe elbow using flexible groove joints. The seismic performance of the elbow specimen was evaluated using a cyclic loading protocol based on deformation angles. To determine the margin of the evaluated seismic performance, the limit states were assessed by applying cyclic loading with a constant amplitude.

The Effects of Argumentation-based General Chemistry Laboratory on Preservice Science Teachers' Understanding of Chemistry Concepts and Writing (논의가 강조된 일반화학실험이 예비교사의 글쓰기 능력 및 화학개념 이해에 미치는 효과)

  • Nam, Jeong-Hee;Koh, Mi-Rye;Bak, Deok-Chan;Lim, Jai-Hang;Lee, Dong-Won;Choi, Ae-Ran
    • Journal of The Korean Association For Science Education
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    • v.31 no.8
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    • pp.1077-1091
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    • 2011
  • The purpose of this study was to examine the effects of argumentation-based general chemistry laboratory on preservice science teachers' chemistry concepts understanding and writing. Five topics about argumentation-based general chemistry laboratory activities were developed using Science Writing Heuristic (SWH) approach. Summary Writing Test, and Chemistry Concepts Test were developed as tools to examine the effects of this approach. Both Argumentation-based general chemistry laboratory activities and traditional general chemistry laboratory activities were implemented for the experimental group (23 students), and traditional general chemistry laboratory activities were implemented for the comparative group (16 students). Results of this study indicated that there were significant differences in both groups' chemistry concepts understanding and summary writing. The experimental group showed significantly higher mean score than comparative group in chemistry concepts understanding and summary writing. In the analysis of the sub-component of Summary Writing, there were no significant difference between both groups in 'Big Idea.' However, the experimental group gained significantly higher mean score in 'argumentation,' 'understanding of science concepts,' and 'rhetoric structure.' The results showed that argumentation-based general chemistry laboratory programs were effective in achieving chemistry concepts understanding and writing in general chemistry laboratory.

Sustainable Water Resources Planning to Prevent Streamflow Depletion in an Urban Watershed: 1. Methodology (도시유역의 건천화 방지를 위한 지속가능한 수자원 계획: 1. 방법론)

  • Lee, Kil-Seong;Cung, Eun-Sung;Kim, Young-Oh;Cho, Tak-Gun
    • Journal of Korea Water Resources Association
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    • v.39 no.11 s.172
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    • pp.935-946
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    • 2006
  • This study proposed a new procedure of sustainable water resources planning to prevent the urban streamflow depletion, based on the Heathcote's study in 1998: (1) to understand the watershed component and processes, (2) to identify and quantify problems within the watershed, (3) to set clear and specific goals, (4) to develop a list of management options, (5) to eliminate infeasible options, (6) to test the effectiveness of remaining feasible options, and (7) to develop the final options. PSR(Presure-State-Response) concept was used for the determination of indicators of PSD(Potential Streamflow Depletion; step 2) and effect equation (step 7) and composite programming for the calculation of PSD. The instreamflow requirement was proposed as clear and specific goal (step 3) and was determined by the larger of the PHABSIM's environmental flow and the drought flow. A continuous rainfall-runoff model is necessary to test the effectiveness of alternatives. It should estimate not only the exact runoff but also the effect of landuse change, reservoir, infiltration facility and so on like SWAT(Soil and Water Assessment Tool). The proposed procedure will be applied on the corresponding paper.