• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.323-331
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• 2010

In this study, we propose a 3D finite element (FE) model for the residual stress under oblique shot peening. Using the FE model for an oblique impact, we examine the effects of factors on the residual stress such as the Rayleigh damping in the material, dynamic friction, and the rate dependency of the material and systematically integrate the effects. The plastic deformation of the shot is also emphasized. Then, the FE model is used to study oblique multi-impacts. The results obtained using the FE model are compared with experimental x-ray diffraction (XRD) results; in contrast to the rigid and elastic shots, plastic shots are found to produce residual stresses similar to that shown in the XRD results. Thus, the 3D FE models with integrated factors and plastically deformable shots are validated. The proposed model will serve as a basis for the 3D FE model for multi-impacts with different impact angles to simulate the actual phenomenon of shot peening.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.549-564
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• 2008

In this paper, the plastic settlement of mortar is analyzed on the basis of the small strain consolidation theory, and the validity of the approach is verified through the comparison with experimental data. First, the amount of settlement caused by self-weight of bulk mortar is measured using a non-contact laser measurement device and the estimation of material parameters related to the settlement of mortar is followed. In advance, another experiment is also performed on mortar with embedded reinforcement to measure the settlement distribution, and the influence of mixture proportions and cover depth on unequal settlement is analyzed. Finally, correlation studies between experimental data and settlement distribution obtained by consolidation analysis represents that the application of consolidation theory to the analysis of plastic settlement of mortar is reasonable.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.107-114
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• 2009

In present study, an alternative process for manufacturing ultra marine blue by using kaolin, sulfur, sodium carbonate, silica, and rosin was investigated. From the experiments, it was found in the reductive calcination process that the temperature variation with the bed height of input materials is relatively high due to the inadequate thermal conductivity of them. It was also found that the color of the ultramarine blue manufactured is sensitive for the shape of the input materials and the calcinations conditions, and specially the heating rate is very important to form ultramarine. For manufacturing green ultramarine by using sulfur, sodium carbonate, silicon, and pine resin, an optimum condition was investigated to be the heating rate region below $0.6^{\circ}C/min$, the reaction temperature of $850^{\circ}C$ and the reaction time of 4 hr. At the oxidative calcination process to manufacture ultra marine blue from green ultramarine, the optimum flow rate of air is $500{\sim}550\;{\ell}/kg$ (green ultramarine) and the reaction temperature is $500{\sim}550^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.396-399
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• 2004

저온 동시소성용 glass-ceramics의 소결 경향성 연구를 위해 lead-borosilicate계 glass를 frit화하여 알루미나분말과 $TiO_2$분말을 $10{\sim}50\;vol%$로 각각 혼합한 후 여러 온도에서 소결하여 소결과 유전 특성을 조사하였다. 그 결과 glass의 연화온도(Ts)가 낮을수록 최대 치밀화 온도가 낮았으며, 반면에 소결밀도는 Ts가 높을수록 높았는데, 이는 glass-ceramicss에서의 결정화도와 관계하였다. 본 연구를 통해 glass-ceramic에서의 소결특성은 glass와 ceramic의 반응성에 의한 2상 석출 정도에 큰 영향을 받음을 알 수 있었으며, ceramic filler로서 알루미나와 $TiO_2$를 이용하여 $900^{\circ}C$에서 소성이 가능하였다. 알루미나의 경우 유전특성$({\epsilon}r=8.5,\;Q{\times}fo=6000)$이 기판용 저유전율 재료로 사용이 가능하였고, $TiO_2$의 경우도 유전특성($({\epsilon}r=17,\;Q{\times}fo=4000)$)이 필터용 고유전율 재료로 사용 가능하도록 높게 나타났다.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.17-23
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• 1990

When a thin walled member is subjected to compression in a condition such as collision, the energy is mainly absorbed by axial crumpling. In this case, dynamic crushing strength of the member is increased due to the effects of strain-rate compared with the static strength, even though the inertia effect is neglected. In this paper, the method of predicting the static crushing for tubular members is presented using the kinematic method of plasticity. Since, a predicted crushing load, taking account of the dynamic yield stress, usually overestimates the effects of strain-rate, the average plastic flow stress for the effects of strain-rate is used to obtain the dynamic crushing load for tubular members. The analytical results are compared with the experiments published in references, and a good correlation is observed.

• Korean Journal of Head & Neck Oncology
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• v.10 no.2
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• pp.206-211
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• 1994

Congenital thyroid dysgenesis including agenesis, hypoplasia and ectopia is the predominant cause of permanent hypothyroidism. Of these, two thirds are due to an ectopic thyroid and about one third to complete thyroid agensis. From Jan. 1981 to Dec. 1992, authors experienced the 9 cases of congenital thyroid dysgenesis. Aberrent thyroid was 4 cases (44.4%), thyroid hemiagenesis with aberrent thyroid was 3 cases(33.3%) and thyroid hemiagenesis was 2 cases(22.2%). The most predominant site of aberrent thyroid is the base of tongue(85.7%). 7 patients(77.8%) revealed euthyroidism and among them, 4 patients showed elevated TSH level. Hypothyroidism was 2 patients (22.2%). 7 cases responded to thyroid suppressive therapy. 2 cases of lingual thyroid which did not responed to thyroid suppressive therapy underwent surgery and they have placed on thyroid suppressive therapy postoperatively.

• Advances in pediatric surgery
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• v.15 no.1
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• pp.58-63
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• 2009

환아는 4개월부터 직장 탈출증과 심한 변비를 보였으며, 9개월에 질로부터 대변이 배출되는 증상을 나타냈으나 검사상 우측 이상 형성 콩팥 및 이소성 요관 이외 특이 소견이 없어 경과 관찰을 시행하였다. 16개월에 전신 마취하에 이학적 검사를 시행하여 누공을 확인하였고 이를 통한 대장 조영술에서 직장 중복증을 진단하여 수술을 시행하였다. 수술 시야에서 직장부터 횡행 결장에 이르는 관형의 뒤창자 중복을 확인하고, 직장-질 누공을 분리하고 결장 및 직장에는 중격절개술을 시행하였으며, 동반된 기형인 이소성 요관과 무기능 우측 신장은 절제하였다. 환아는 수술 후 3년간 잘 지내고 있다. 직장-질 누공을 동반한 관형의 뒤창자 중복은 매우 드문 선천성 기형으로 저자들의 경험을 문헌 고찰과 함께 보고하는 바이다.

• Transactions of Materials Processing
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• v.1 no.2
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• pp.52-62
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• 1992

본 연구에서는 모델재료를 이용한 모사실험을 통하여 고온의 강을 단조하였을 때의 유동과 변형 그리고 하중을 검토하고, 이어 성형에 관한 연구를 하였다. 모델재료인 플라스티신은 고용의 강을 모사하는데 많이 쓰이는데, 실험을 통하여 플라스티신과 강과의 변형저항식을 비교 검토하였다. 이 실험결과 상사성이 어느정도 일치함을 알았고, 이 상사성 결과를 이용하여 실제와 모델사이의 하중과 응력비를 검출하였다. 이로써 플라스티신을 이용한 단조 압축 실험을 통하여 실제의 하중을 예측하였다. 또한 예비 성형체를 설계하기 위하여 앞서 실험한 결과들을 이용하여 초기의 실린더의 체적과 치수를 결정하고 이에 단계에 따른 성형과정을 통하여 예비 성형체를 만들었는데, 이는 제한된 용량으로 성형하여야 하는 문제를 해결하기 위함이었다. 실험 결과 8단계에 따른 성형과정에 의해 우리가 원하는 대형 단조품을 성형할 수 있음을 알았다.

• Journal of Chest Surgery
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• v.42 no.6
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• pp.789-791
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• 2009

Tuberculoma of the lungs is not an uncommon finding, but an ectopic liver in the lung is extremely rare. Pulmonary tuberculosis presenting as tuberculoma can be diagnosed radiologically, but its definite diagnosis is established by confirmation of the acid-fast bacillus or the unique histology. We report here on a case of tuberculoma of the left lower lobe that was erroneously diagnosed as ectopic liver by ultrasono-guided fine needle aspiration biopsy. An understanding of the normal variants of the liver can prevent a patient from undergoing an unnecessary invasive procedure.

• Computational Structural Engineering
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• v.7 no.3
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• pp.133-141
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• 1994

When a bolt is tightened up to the range of plastic deformation, yielding may be governed by the combined stresses due to the axial force developed in the bolt and the frictional torque induced on the thread by the contact with the nut. Consideration is taken account of the fact that the unengaged portion of the thread has least sectional area, being subject to initial yielding. Once yielding has taken place some strain hardening effect may result. Incremental stress-strain relations are used to treat the continued yielding, which is equivalent to treat continued yielding as if summing up the effects of thin walled cylinders subject to plastic deformation. M10 bolts of fine threads are used for both computational and experimental purposes. Variation of axial forces and frictional torques vs. the frictional coefficients are presented together with other plots showing some characterist of bolt under plastic deformation. Finally, a design and control aid for the tightening(i.e., kind of nomograph) is presented, showing the relationships among the torque factor and frictional coefficients for that particular bolt used in the experiment.