• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.103-111
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• 2002

Steady-state creep analysis of power generation turbine blade is carried out considering thermal loads and centrifugal forces. Creep strains and stresses of the turbine blade are calculated for 3-D finite clement model of the turbine blade. From the numerical results, creep life of the turbine blade is predicted. The results of creep analysis during about 200 hours indicate that creep strains of the turbine blade do not reach the rupture strain of GTD111. Creep stresses of the turbine blade are relaxed as time increases. Maximum creep strain occurs at the tip section of the airfoil pressure surface. The maximum creep strain of the turbine blade is expected close to the rupture strain after 50,000 hours approximately. The turbine blade may not have creep damage for the starting procedure of the turbine.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.194-199
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• 2000

The creep rate is affected by the temperature and in fact. if the temperature above $T_M/2(T_M:melting\;point)$. The aim of the present investigation is to study the relationship of static creep and cyclic creep behavior of pure copper and the formulation of these phenomena with the special attention to the instantaneous strain. strain rate from time and number of cycles have the same inclination Steady state creep rate depend upon maximum stress and can be expressed as linear function according to Power law creep equations Creep rupture time has relation with creep rate. and it make a group represented as the same direct line regardless of max stress, stress ratio and the temperature. Initial strain effect on continuous creep deformation. and have guantitative relationship between elastic and Plastic strain. LMP have similar tendency than OSDP and MHP according to temperature

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.371-378
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• 2018

Internal detonation of a warhead inside a compartment of naval vessel can result in serious blast damages including plastic deformation and rupture of the structural members especially bulkhead due to the huge explosive impact pressure, fragments and high temperature flame. To secure watertight integrity and to prevent the domino-type flooding of neighbouring compartments caused by the rupture of bulkheads, it is necessary to develop the structural design technology of Blast Hardened Bulkheads(BHB) which can resist the blast impact pressure of threatening weapons to increase the survivability of naval vessels. This study dealt with the simplified structural response analysis of BHB under impact pressure of confined explosion and aimed to develop the efficient and rational design method of BHB and joint structures which can be applied at initial design stage. The present 1st report dealt with the phenomena of explosive detonation surveying the preceding experimental/theoretical research and the characteristics of time history of blast pressure including the peak value and duration time were examined. And to predict the large plastic deformation behaviors of BHB by the huge blast pressure reasonably, the plastic hinge method including the membrane effects was formulated. It was applied to the simplified structural design equations. The following report will deal with the application and adjustment process of the structural scantling equations to the actual BHB design and verification of validity of them.

• Journal of Korean Foot and Ankle Society
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• v.23 no.3
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• pp.100-104
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• 2019

Purpose: This study examined the clinical outcomes and assessed the average time to return to play following a peroneal tendon repair in Korean athletes. Materials and Methods: Between March 2004 and February 2017, a total of 30 athletes underwent peroneal tendon repair for a peroneal tendon tear. The indications of surgical treatment were chronic pain or intractable symptoms after a previous ankle sprain affecting sports activity refractory to conservative treatment for at least six months. The patient underwent tubulization for a longitudinal tendon rupture. Peroneus longus to peroneus brevis tenodesis was performed when tendon repair was impossible due to total rupture or multiple longitudinal rupture. Results: Twenty patients not included in this study were as follows: insufficient follow-up, previous surgery, and additional bone surgery. All 10 patients had a previous ankle sprain history, tenderness and swelling on the retromalleolar area. In the 10 patient population, there were five peroneus brevis tendon tears, three peroneus longus tendon tears, one peroneus longus and brevis tendon tear, and one peroneus brevis and superior peroneal retinaculum tear. In the 10 patients, six cases of peroneal brevis tendon repair and four cases of peroneal longus to brevis tenodesis were performed. The preoperative American Orthopaedic Foot and Ankle Society score was improved from a mean of 60.6 (standard deviation [SD], 8.64) to a mean of 90.2, postoperatively (SD, 4.4; p<0.012). The preoperative visual analogue scale was improved from a mean of 5.43 (SD, 1.2) to 0.5 (SD, 0.16), postoperatively (p<0.023). The mean length of time to return to play was 12.2 weeks (range, 8~16 weeks). Conclusion: Peroneal tendon tear can occur due to sports injuries. If there is tenderness at the retromalleolar area, the surgeon should consider a peroneal tendon lesion. Surgical repair of the peroneal tendon can be an effective treatment to help athletes to return to play.

• Advances in pediatric surgery
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• v.19 no.2
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• pp.98-107
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• 2013

Debates exist about the appropriate treatment for pancreatic trauma in children. We intended to examine the safety of the operation of pancreatic trauma in children. This is a retrospective study of 13 patients, younger than 15, who underwent surgery for pancreatic trauma, between 1993 and 2011 in Seoul National University Children's Hospital. Medical records were reviewed for mechanism of trauma, clinical characteristics, radiological findings, operation and outcomes. Organ injury scaling from the AAST (American Association for Surgery of Trauma) was used. All injuries were caused by blunt trauma. Patients with grade III, IV, and those who were difficult to distinguish grade II from IV, underwent surgery due to severe peritonitis. Three patients with grade II were operated for reasons of mesenteric bleeding, tumor rupture of the pancreas, and progression of peritonitis. Distal pancreatectomy was performed in 10 patients and subtotal pancreatectomy and pylorus preserving pancreaticoduodenectomy in 1 patient each. The remaining one underwent surgical debridement because of severe adhesions. The location of injury, before and after operation, coincided in 83.3%. The degree of injury, before and after the operation, was identical in all the patients except for those who were difficult to tell apart grade II from grade IV, and those cannot be graded due to severe adhesion. Postoperative complications occurred in 23.1%, which improved with conservative treatment. Patients were discharged at mean postoperative 12(range 8~42) days. Even though patients with complications took longer in time from diagnosis to operation, time of trauma to operation and hospital stay, this difference was not significant. In conclusion, When pancreatic duct injury is present, or patient shows deterioration of clinical manifestation without evidence of definite duct injury, or trauma is accompanied by other organ injury or tumor rupture, operative management is advisable, and we believe it is a safe and feasible method of treatment.

• Journal of the Korean Institute of Gas
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• v.24 no.2
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• pp.36-43
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• 2020

Gas system fire extinguishing equipment is a very economically useful facility, but if it is not used for a long period of time after installing the equipment, there is possibility of rupture due to corrosion of containers and operation errors of equipment systems, and this is very dangerous. However, it is impossible to experiment to check whether the equipment is operating normally. If gas is temporarily released into the enclosed space due to rupture and malfunction, it can cause serious human damage due to gas suffocation. In this study, based on the suffocation death accident of gas system fire extinguishing facility, the inflow path of released gas and the possibility of death and time to death were estimated using a 3D scan and FLACS.

• Journal of Chest Surgery
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• v.23 no.4
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• pp.782-784
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• 1990

We present a case of ruptured abdominal aortic aneurysm caused by blunt injury. The patient was 23-year-old soldier injured by a motor vehicle accident. Injuries sustained a contused abdominal aorta. At the time of aortic repair, the involved segment formed huge pseudoaneurysm, and which had intimal tear. Aorto-iliac graft replacement was carried out with a woven-dacron Y-graft prosthesis, which restored satisfactory circulation to both lower limbs. The postoperative course was uneventful.

• Journal of the Korean Society of Safety
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• v.3 no.2
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• pp.35-48
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• 1988

Modern technological progress demands the use of materials at high temperature and high pressure. One of the most critical factors in considering such applications - perhaps the most critical one - is creep behavior. In this study the stress exponents n were determined during creep over the temperature range of $90^{\circ}C\;to\;500^{\circ}C$ (0.4 - 0.85 Tm) and stress range of 0.64 kgt/$mm^2$ in order to investigate the creep hehavior. The stress dependence of rapture time (n') were determined over the temperature range of $200^{\circ}C\;to\;240^{\circ}C$ and stress range of 8.13 kgt/$mm^2$ to 9.55 kgt/$mm^2$ in order to investigate to creep rupture property. And the stress transient dip tests were also carried out for the internal stress ${\sigma}i$ over the temperature range of $90^{\circ}C\;to\;500^{\circ}C$ and stress range of 0.64kgt/$mm^2$ to 17.2 kgt/$mm^2$. The creep tests for constant temperature and stress transient dip tests were conducted in air with Al 7075 alloy under constant tensile load. At around the temperature range $200^[\circ}C\;-\;230^{\circ}C$ and the stress level 8.13 - 9.55 (kgt/$mm^2$), the temperature range $280^{\circ}C\;-\;310^{\circ}C$ and the stress level 1.85 - 2.55 (kgt/$mm^2$), the temperature range $380^{\circ}C\;-\;410^{\circ}C$ and the stress 1.53 - 0.91 (kgt/$mm^2$), the stress exponent in had the value of 6.2 - 6.65 but at around the temperature range $90^{\circ}C\;-\;120^{\circ}C$ and the stress level 10 - 17.2(kgt/$mm^2$), the value of 1.3, and at around the temperature range $470^{\circ}C\;-\;500^{\circ}C$, the stress level 0.62 - 1.02 (kgt/$mm^2$) the value of 1-1. Besides these results, at around the temperature $200^{\circ}C\;-\;240^{\circ}C$ the stress dependence of rupture time (n') had the value of 6.3. Finally, it was found that the value n calculated by considering the applied stress dependence of the internal stress were in good agreement with those obtained for the creep test. Then, it was concluded that the change in n was mainly attributed to the difference of the applied stress dependence of the internal stress and the ratio of the internal stress to the applied stress, and the creep rupture life may be represented as.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.27-36
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• 2005

Some studies have shown that unstable factors are inherent in WEDM process, causing the instability of the discharging pulse to reach about 40∼60％ in normal machining. Transient stability is an important subject in WEDM process since there is a close relationship between stability and machining performance, such as the characteristics of a machined surface, machining speed and problem of instability like wire rupture phenomenon. Among the many machining parameters affecting WEDM machining state, three specific parameters (Vr, Ip, off time ) are major controllable variables that can be applied in transient stability control. And, this research investigates the implementation and analysis of real-time micro control of the discharging stability of WEDM (Wire Electric Discharge Machining) process.

• Advances in materials Research
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• v.7 no.1
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• pp.45-72
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• 2018

In the present study, a special attention has been paid to the effects regarding the use of different superplasticizers in different dosages. To do so, 36 mixes of normal and self-compacting concrete with two water/binder ratios of 0.35 and 0.45, four different types of superplasticizer including melamine-formaldehyde, naphthalene-formaldehyde, carboxylic-ether and poly-carboxylate, four different superplasticizer/cement ratios of 0.4%, 0.8%, 1.2% and 1.6% and two silica fume/cement ratios of 0% and 10% have been cast. Moreover, the initial and final setting time of the pastes have been tested. For self-compacting mixes, flow time, slump flow, V-funnel, J-ring and L-box tests have been carried out as well as testing the compressive strength and rupture modulus. For normal concrete mixes,slump test has been conducted to assess the workability of the mix and then for each mix, the compressive strength and rupture modulus have been determined. The results indicate that in addition to the important role of superplasticizer type and dosage on fresh state properties of concrete, these parameters as well as the use of silica fume could affect the hardened state properties of the mixes. For instance, the mixes whose superplasticizer were poly-carboxylic-ether based showed better compressive and tensile strength than other mixes. Besides, the air contents showed robust dependency to the type of the superplasticizer. However, the use of silica fume decreased the air contents of the mixes.