• Title/Summary/Keyword: defect factor

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Experimental and numerical study on viscoelastic behavior of polymer during hot embossing process (핫엠보싱 공정의 폴리머 점탄성 거동에 대한 연구)

  • Song, N.H.;Son, J.W.;Rhim, S.H.;Oh, S.I.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.05a
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    • pp.191-194
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    • 2007
  • In hot embossing lithography which has shown to be a good method to fabricate polymeric patterns for IT and bio components, it is very important to determine the proper process conditions of pressure, temperature, and time. It is also a key factor for predicting the optical properties of final product to calculate residual stress distribution after the embossing process. Therefore, to design the optimum process with right conditions, the ability to predict viscoelastic behavior of polymer during and after the hot embossing process is required. The objective of the present investigation is to establish simulation technique based on constitutive modeling of polymer with experiments. To analyze deformation behavior of viscoelastic polymer, the large strain material properties were obtained from quasi-static compression tests at different strain rates and temperatures and also stress relaxation tests were executed. With this viscoelastic material model, finite element simulation of hot embossing was executed and stress distribution is obtained. Proper process pressure is very important to predict the defect and incomplete filling.

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Generalized fracture toughness for specimens with re-entrant corners: Experiments vs. theoretical predictions

  • Carpinteri, Alberto;Cornetti, Pietro;Pugno, Nicola;Sapora, Alberto;Taylor, David
    • Structural Engineering and Mechanics
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    • v.32 no.5
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    • pp.609-620
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    • 2009
  • In this paper the results of a series of experimental tests upon three-point bending specimens made of polystyrene and containing re-entrant corners are firstly described. Tests involved different notch angles, different notch depths and finally different sizes of the samples. All the specimens broke at the defect, as expected because of the material brittleness and, hence, the generalized stress intensity factor was expected to be the governing failure parameter. Recorded failure loads are then compared with the predictions provided by a fracture criterion recently introduced in the framework of Finite Fracture Mechanics: fracture is assumed to propagate by finite steps, whose length is determined by the contemporaneous fulfilment of energy balance and stress requirements. This fracture criterion allows us to achieve the expression of the generalized fracture toughness as a function of the tensile strength, the fracture toughness and the notch opening angle. Comparison between theoretical predictions and experimental data turns out to be more than satisfactory.

A Case of Azathioprine Induced Severe Myelosuppression and Alopecia Totalis in IgA Nephropathy

  • Kim, Jae Choon;Kim, Ye Kyung;Hyun, Hye Sun;Park, Eu Jin;Kang, Hee Gyung;Ha, Il Soo;Cheong, Hae Il
    • Childhood Kidney Diseases
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    • v.21 no.1
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    • pp.35-39
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    • 2017
  • Azathioprine is commonly used as immunosuppressive therapy for various inflammatory diseases including chronic glomerulonephritis. Myelosuppression is a common side effect of azathioprine, resulting in the need for dose reduction. However, severe pancytopenia or alopecia is not often encountered. Here, we report a case of severe myelosuppression, and alopecia totalis that occurred after azathioprine treatment in a patient with IgA nephropathy. A 10-year-old boy with IgA nephropathy was treated with oral deflazacort and later with azathioprine. After 4 weeks, the patient complained of hair loss, and despite a dose reduction in azathioprine, he developed bone marrow suppression and alopecia totalis in two weeks. The blood indices and alopecia of the patient had returned to normal after azathioprine withdrawal and 3 consecutive doses of granulocyte colony-stimulating factor. We suggest that physicians remain vigilant to the side effects of azathioprine. Unusual hair loss after azathioprine treatment might suggest a defect in the metabolism of the drug, warranting the discontinuation of azathioprine to prevent more severe side effects.

Analyzing the Effect of Si Surface Morphology on Front Electrode Formation (전면 전극 형성 시 표면 형상이 미치는 영향 분석)

  • Han, Hyebin;Choi, Dongjin;Kang, Dongkyun;Park, HyunJung;Bae, Suhyun;Kang, Yoonmook;Lee, Hae-Seok
    • Current Photovoltaic Research
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    • v.7 no.4
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    • pp.130-133
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    • 2019
  • The Ag crystallite formed during the formation of the front electrode forms a contact between the metal of the electrode and the emitter of the cell. Contact between the electrode and emitter plays an important role in collecting electrons generated by the solar cell. Therefore, Ag crystallite formation is an important factor. In order for solar cells to have good characteristics, it is important to understand the factors influencing the Ag crystallite formation. Factors affecting the formation of Ag crystallites include Si emitter, morphology, Si defect and firing temperature. The influence of surface morphology on Ag crystallite formation was confirmed throughout this study. In the case of fine texturing, the Ag crystallites were formed at the pointed parts. The finer the texturing, the sharper areas and more Ag crystallites were formed. This was confirmed by SEM image and FF calculation.

Effect of Printing Conditions on Fluting in Heatset Web Offset Printing (Heatset 윤전 오프셋 인쇄에서 인쇄주름에 대한 인쇄조건의 영향)

  • Jeon, Sung-Jai;Youn, Jong-Tae
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.41 no.1
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    • pp.52-60
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    • 2009
  • A printing defect known as fluting (or waviness) of the web printed by heatset web offset printing process is one of the chronically serious problems deteriorating print quality. In this paper, fluting occurrence on uncoated papers was explored in terms of many printing conditions including drying temperature, fountain solution amount, ink supply, and press configurations. For this purpose, fluting on prints from real press runs was appraised in a quantitative manner. As results, ink supply was a distinctive factor for fluting such that the lower ink amount, the milder fluting. However increase in fountain solution seemed to make fluting severer while the effect of drying temperature was inconsistent for each paper. This result might indicate variable drying requirements for each paper. Thereby it was suggested that the optimum drying conditions related to the printabilities of each paper need to be established to minimize fluting potential. A press with short dryer and drastic cooling unit produced higher fluting. Suggestions for future work were given along with interpretation for the results.

Evaluation on Architectural Acoustic Performance of Small-scaled Multipurpose Hall for Improvement of Acoustic Performance (음향성능 개선을 위한 소규모 다목적홀의 건축음향성능 평가)

  • Yun, Jae-Hyun;Ju, Duck-Hoon;Kim, Jae-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.226-230
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    • 2007
  • In case of domestic performance hall, it is real situation that the demand of multipurpose hall that accommodative a lecture, gathering activity, drama and concert than a professional performance hall such as opera house, is on increasing. Accordingly, since such multipurpose hall, in view of its characteristics, is emphasizing the clearness of sound, also it requiring the repletion or abundance of sound simultaneously, it could be said that the sufficient examination and plan with regard to the architectural acoustics design is indispensable. However, since most of multipurpose hall has ever been designed and constructed without any consideration on an acoustic factor, many problem points are generating. Standing on such viewpoint, this Research has measured the physical acoustic characteristics about the small-scaled multipurpose hall recently built without any acoustic consideration, and through the above, tried to grasp the acoustic defect and controversial point thereof. It is deemed that such study result could be utilized as an important material for improvement the acoustic performance of the multipurpose hall.

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TREATMENT FOR EPILEPSY PATIENT WITH BITING INJURY ON MENTOLABIAL SULCUS USING SOFT MOUTH GUARD : A CASE REPORT (Epilepsy 환아에서 야기된 이순구 교상을 soft mouth guard로 치료한 증례)

  • Kim, Tae-Wan;Kim, Young-Jin
    • The Journal of Korea Assosiation for Disability and Oral Health
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    • v.4 no.1
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    • pp.17-20
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    • 2008
  • In the brain of epilepsy patients, sudden and unusually intense bursts of electrical charges are occurred repeatedly. So, epilepsy patient experiences seizure. Seizure shows various frequency and precipitating factor and has a prodrome. Also, epilepsy patient present various behavior pattern during seizure. If the biting injury occurred during seizure, there would be pain, infection, defect of soft tissue and esthetic problem. The dental management of self-mutilation includes preserve methods of using appliances such as lip bumper or soft mouth guard and radical methods such as extraction of all teeth or orthognathic surgery. A case of epilepsy patient with self-mutilation of mento-labial sulcus is presented. She was treated successfully with soft mouth guard.

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An Analysis of Turbine Disk Forging of Ti-Alloy by the Rigid-Plastic Finite Element Method (강소성 유한요소법을 이용한 Ti 합금 터빈디스크의 단조공정 해석)

  • 조현중;박종진;김낙수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.11
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    • pp.2954-2966
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    • 1994
  • The characteristics and good corrosion resistance at room and elevated temperatures led to increasing application of Ti-alloys such as aircraft, jet engine, turbine wheels. In forging of Ti-alloy at high temperature, die chilling and die speed should be carefully controlled because the flow stress of Ti-alloy is sensitive to temperature, strain and strain-rate. In this study, the forging of turbine disk was numerically simulated by the finite element method for hot-die forging process and isothermal forging process, respectively. The effects of the temperature changes, the die speed and the friction factor were examined. Also, local variation of process parameters, such as temperature, strain and strain-rate were traced during the simulation. It was shown that the isothermal forging with low friction condition produced defect-free disk under low forging load. Consequently, the simulational information will help industrial workers develope the forging of Ti-alloys including 'preform design' and 'processing condition design'. It is also expected that the simulation method can be used in CAE of near net-shape forging.

A Study on Valuation about Acoustic Performance utilizing Auditory-Evocation for Grand Performance Hall of G Art Hall (가청화를 이용한 G예술회관의 대공연장 음향 성능평가에 관한 연구)

  • Kim, Nam-Don;Yun, Jae-Hyun;Kim, Jae-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.623-627
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    • 2007
  • In case of the Grand Performance Hall, in view of its distinctiveness, since various Assembly Activity as well as Lecture together with the use for Music are important besides the purpose of Performance itself, the consideration with regard to the sound environment which enables to minimize the acoustic defect has appeared on the stage as an essential factor. On this viewpoint, this Study has attempted to examine the acoustic satisfaction degree and its response regarding to the grand performance hall by means of the measurement and valuation about the psychological volume of human-being using the auditory-evoked technology that possible to experience the Virtual Sound Field at the designing stage, after practice of the optimized acoustic design for the object of the grand performance hall on the step of construction. As the result of auditory-evocation, it was known that the valuation about the acoustic performance after reformation has been improved affirmatively than before reformation. It is considered that such outcome of the study could be utilized as the useful material that enables to improve the curtailment effect of construction cost and the acoustic performance, by means of the presupposition control about the acoustic problem from the stage of design, for the occasion when the similar Performance Hall is planning to build, hereafter.

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Wear Analysis of Journal Bearings Operating in a Shaft During Motoring Start-up and Coast-down Cycles - Part II: Wear Analysis of two Journal Bearings Supporting a Misaligned Shaft (모터링 시동 및 시동정지 사이클에서 경사진 축을 갖는 저어널베어링의 마모 해석 - Part II: 경사진 축을 지지하는 두 저어널베어링의 마모해석)

  • Chun, Sang Myung
    • Tribology and Lubricants
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    • v.33 no.4
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    • pp.168-186
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    • 2017
  • This paper presents a wear analysis procedure for calculating the wear of journal bearings during the start-up and coast-down cycles of a motoring stripped-down single cylinder engine operating with a tilted shaft. In order to decide whether the lubrication state of a journal bearing is in the mixed-elasto-hydrodynamic lubrication regime, we utilize lift-off speed and MOFT (most oil film thickness) under mixed-elasto-hydrodynamic lubrication regime at the corresponding aligned shaft. We formulate an equation for the modified film thickness in a misaligned journal bearing considering the additional wear volume described in Part I of this study. For this, we use the calculation results of the degree of misalignment and tilting angle obtained after finding the eccentricities of the two bearings supporting the crankshaft of a single cylinder engine. In this Part II, we calculate the wear of journal bearings using the fractional film defect coefficient, the asperity load sharing factor, and the modified specific wear rate for the application of mixed-elasto-hydrodynamic lubrication regime. We show that the accumulated wear volume after turning the ignition switch on and off once, increases to ${\sigma}=39{\mu}m$ and then decreases from ${\sigma}=39{\mu}m$ with increasing in surface roughness.