• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 International Symposium
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• pp.79-94
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• 2002

Root cause -Thermal expansion coefficient mismatch -Tape warpage -Initial die crack (die roughness) Guideline for failure prevention -Optimized tape/Substrate design for minimizing the warpage -Fine surface of die backside Root cause -Thermal expansion coefficient mismatch - Repetitive bending of a signal trace during TC cycle - Solder mask damage Guideline for failure prevention - Increase of trace width - Don't make signal trace passing the die edge - Proper material selection with thick substrate core Root cause -Thermal expansion coefficient mismatch -Creep deformation of solder joint(shear/normal) -Material degradation Guideline for failure Prevention -Increase of solder ball size -Proper selection of the PCB/Substrate thickness -Optimal design of the ball array -Solder mask opening type : NSMD -In some case, LGA type is better

• 한국정밀공학회지
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• 제6권3호
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• pp.90-99
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• 1989

In this study, J-integral values obtained by various methods, i.e, R-Curve, Unloading Compliance, Strectched Zone Width [SZW], and Acoustic Emission [AE] methods are investigated. Elasto-plastic fracture toughness [$J_IC$] estimations by R-curve method are overestimated than those by SZW method, and those by unloading compliance method is around middle value of them. And the difference between them is little. The $J_IC$ value by AE method was almost agreed with that by SZW, and then proved to be useful. Crack propagation mechanism on fractography is a stable ductile fracture. For the identification of ductile fracture, both fractography analysis and AE method were applied to estimate the characteristics more precisely.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.43-50
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• 2017

A type of one-way concrete composite slabs made by strain hardening cementitious composites (SHCC) deck combined with high tensile reinforcements was developed and evaluated by four-point slab bending test. The SHCC material was considered to have an high-ductile and strain hardening behavior in tension after cracking. From experimental comparisons with conventional reinforced concrete slab, the proposed SHCC and high tensile reinforced concrete composite slab showed more improved responses both in service and ultimate load capacities as well as in control of crack width and deflection.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.348-353
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• 1996

This study addresses the evaluation of the durability of reinforced concrete marine structures subjected to fatigue loading. The laboratory investigation was carried out on full and half size reinforced concrete specimens with three different water cement ratios (0.3, 0.4, and 0.56), static and fatigue loading conditions, and epoxy-coated and regular black steel reinforcements. The marine tidal zone was simulated by alternate filling and draining of the tank (wet and dry cycled), and a galvanostatic corrosion technique to accelerate corrosion of reinforcement was used. Half-cell potentials and changes of crack width were measured periodically during the exposure and followed by ultimate strength testing. The significant findings include adverse effect of fatigue loading, existence of an explicit size effect, poor performance of epoxy coated steel, and negative effect of increasing water/cement ratio.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.657-662
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• 2000

This paper presents the results from experimental study that investigated to explore the load transfer characteristics of post-tensioning anchorage zones. The experimental program investigated the primary variables which affect the ultimate load, lateral strains and crack width: concrete compressive strength, details of reinforcement and shape of anchorage. Through this research, it was found that the governing factor of the ultimate load was not compressive cylinder strength but tensile splitting strength. Ultimate load was increased and lateral strain was decreased as the ratio of spiral increased because the lateral expansion of th concrete inside the spiral was restrained by the spiral. Furthermore, the shape of anchorage which can diminish the wedge effect of anchorage and disperse the anchorage force in various depths was more effective.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.156-160
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• 1994

Use of engineering ceramics has been increasing due to the outstanding physical and chemical properties. Conventional machining processes, however, are not applicable due to their hardness and brittleness. Laser cutting is a promising alternative for these ceramics. In this study, experimental data of CO $_{2}$ laser cutting of $Al_{2}$ $O_{3}$ and Si $_{3}$ N $_{4}$ are obtained to give a guide in the industry. Results of $Al_{2}$ $O_{3}$ cutting showed extreme weakness to thermal crack and it was found that pulsed beam has to be used for thick $Al_{2}$ $O_{3}$ specimen. Si $_{3}$ N $_{4}$ showed good results for both CW and pulsed beams. Using pulsed beam resulted narrower kerf width with increased surface roughness a nd reduced cutting speed. It was also found that a parameter call path energy is useful for representing minimum threshold value for possible cutting range with pulsed beam.

• 대한기계학회논문집
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• 제10권5호
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• pp.680-688
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• 1986

본 연구에서는 마르텐사이트-페라이트 복합조직강의 파괴인성평가법을 확립하 기 위하여 불균질의 대표적 인자인 페라이트 결정입경 및 마르텐사이트의 강도를 변화 시켜 R곡선법과 SZ법에 의해 파괴인성을 평가하고, SZ법에 의한 $J_{IC}$ 의 과대평가 정 도와 이에 대한 원인을 규명하기 위하여 균열선단의 미시파괴거동을 검토하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.269-272
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• 2005

Epoxy resins are gradually becoming some of the most important and versatile polymers in modem civil engineering. Because epoxy resins have some unigue properties, such as toughness, versatility of viscosity and curing conditions, good handling characteristics, high adhesive strength, inertness, low shrinkage compared to most other thermo-setting resins and concrete, and resistance to chemicals, they have found many applications in construction castings, repair materials, road or bridge deck pavements, coatings, and as structural or non structural adhesives. In this applications, epoxy resins are widely used for polymer concretes, grouting materials, injection glues, and sealants. In this paper, characteristics of deformation of repair material after repaired have been investigated by viscosity of repair material and the width of crack. It is believed that flexural strength of epoxy resin with low viscosity is high because tensile strength is high and elongation at break is low, fracture energy is low.

• Structural Monitoring and Maintenance
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• 제6권4호
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• pp.269-289
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• 2019

This study investigated experimentally the response of thick reinforced concrete specimens having hollow cores with critical parameters. The investigation includes testing of twelve specimens that are solid and hollow-core slab models. Each specimen consists of two pieces, the piece dimensions are (1.2 m) length, (0.3 m) width and (20 cm) thickness tested under both monotonic and repeated loading. The test program is carried out to study the effects of load type, core diameters, core shape, number of cores, and steel fiber existence. Load versus deflection at mid span, failure modes, and crack patterns were obtained during the test. The test results showed that core shape and core number has remarkable influenced on cracking pattern, ultimate load, and failure mode. Also, when considering repeated loading protocol, the ultimate load capacity, load at yielding, and ductility is reduced.

• Computers and Concrete
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• 제11권3호
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• pp.253-270
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• 2013

The aim of the present paper is to show the application of optimization strategies for the cost of beams in reinforced concrete buildings and to propose pre-sizing parameters. In order for these goals to be met, an optimization software program was developed. The program combines the analysis of structures by the grid model, reinforced concrete sizing, and the simulated annealing optimization heuristic. Sizing is compliant with the NBR 6118 (2007) Brazilian standard, according to which flexural, shearing, torsion, and web reinforcements and serviceability limit states (deflection and crack width limitation) are checked. Besides the dimensions of the situations mentioned above, the influence the cost of each material (steel, concrete and formwork) has on the overall cost of structures was also determined.