• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.51-53
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• 2012

This paper is to report the results of mock-up test for concrete during severe cold weather. The temperature is fixed at -20℃. The mock-up specimens were fabricated simulating slab, wall and column. Heating coil with different heat capacity with 5 W and 15 W were embedded at slab specimen. Test results revealed that at -20℃, temperature dropped below 0℃ since around 70 hours. It takes 7 days to gain 45°D·D of maturity for avoiding frost damage at early age.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.113-123
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• 2003

Both numerical analysis and experiment of cold and hot tests were performed to obtain basic design data for the swirl coaxial type Injector and to predict the combustion performance. Mass distribution, mixing distribution, mixing efficiency, characteristic velocity efficiency were measured by the cold tests and numerical analysis using the commercial thermo-hydraulic program. Test and analysis variables were recess, pressure drop, velocity ratio, mixing spray, mixture ratio. Hot tests were performed for the Uni-element injector to compare the performance with the cold test results, and, hot tests for Multi-element injector were performed to compare the performance with Uni-element injector. Designed thrust of the Uni-element injector liquid rocket was 35kgf at sea level and combustion chamber pressure, 20bar. Kerosene and Lox were used as a propellant.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.36-39
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• 2003

Due to the strength and biocompatibility requirement, the stainless steel SUS 316L is widely used for trauma internal fixation device. SUS 316L can be hardened and strengthened only by cold work. In this work, the material compression test is performed both in laboratory and computer simulation by a FEM analysis software DEFORM to correlate the hardness to strain. This data is then used for preform design and predict the hardness of the finish bone plate forging. Finally, we compared the hardness between the actual forging and computer analysis results. Although the predicted hardness from computer simulation. is 55HV higher than the final forging sample, we can get good compatibility on the hardening tendency of cold forging.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.141-144
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• 2002

This study presents the enhancement of forgeability of SNCM522H materials. Target parts are output shaft(OP shaft) used as components of power train for automobiles. To carry out cold forging process of OP shaft by 1 pass instead of existing 2 pass process, studies in terms of process design and heat treatment were performed. To introduce the new process, Finite element Method are accomplished, and to verify the validity of proposed heat treatment cycle, several experiments(Hardness test, Observation of optical microstructures, tensile test) are carried out.

• Transactions of Materials Processing
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• v.12 no.5
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• pp.473-478
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• 2003

This study presents the enhancement of forgeability of SNCM522H materials. Target parts are output shaft(OP shaft) used as components of power train for automobiles. To carry out cold forging process of OP shaft by 1 pass instead of existing 2 pass process, studies in terms of process design and heat treatment were performed. To introduce the new process, the finite element method was accomplished, and to assess the validity of proposed heat treatment cycle, several experiments(hardness test, observation of optical microstructures, tensile test) were carried out. The 2Pass forging process could be reduced as lPass process through improvement of process and heat treatment technology and that would give cost reduction.

• Transactions of Materials Processing
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• v.10 no.1
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• pp.67-74
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• 2001

The cold forging process to produce a long-neck flange is investigated by using model material test. The two stage process with optimum design condition is examined using plasticine, which is suitable to model steel at room temperature. The similarity theory is employed to estimate the forging load of each sequence by strict application of similarity condition between steel(AISI 1015) and plasticine material The model test results are compared with the simulation results and shows good agreement. The proper forging process with least forming energy can be resulted in $25^{\circ}$ of extrusion semi-die angle.

• Steel and Composite Structures
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• v.47 no.1
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• pp.135-145
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• 2023

This study presents a numerical investigation into the hysteretic behavior of cold-formed austenitic stainless steel square hollow section (SHS) brace members using a commercial finite element (FE) analysis software ABAQUS/Standard. The initial/post buckling and fracture life of SHS brace members are comprehensively investigated through parametric studies with FE models incorporating ductile fracture model, which is validated against the existing laboratory test results collected from the literature. It is found that the current predictive models are applicable for the initial buckling strengths of SHS brace members under cyclic loading, while result in significant inaccuracy in predictions for the post-buckling strength and fracture life. The modified predictive model is therefore proposed and the applicability was then confirmed through excellent comparisons with test results for cold-formed austenitic stainless SHS brace members.

• The Journal of Internal Korean Medicine
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• v.25 no.3
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• pp.559-568
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• 2004

Diagnosis of Raynaud's phenomenon is primarily based on clinical symptoms. Cold stress test(CST) done by DITI(Digital Infrared Thermographic Image) can be helpful for objective diagnosis. The cold stress test was performed three times by DITI; the first after 15 minutes of rest, the second right after one minute of soaking in $20^{\circ}C$ water, the third ten minutes after immersion. For a clear diagnosis, the temperature of the finger tips must be low, or the thermal difference between the metacarpophalangeal joints and the fingertips must be large. Also the evaluation of treatment depends on decrease of thermal gradient between the metacarpophalangeal joints and the finger tips after CST. In oriental medicine Raynaud's phenomenon can be categorized by coldness of the limbs or numbness. Numbness was diagnosed as depression of Ki and Chiljehyangbuhwan(Qizhixiangfuwan) was prescribed. Positive results were observed, not only in follow up CST, but also Visual Analogue Scale after treatment.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.1
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• pp.36-44
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• 2012

Multi-injector rocket engine using high-concentrated hydrogen peroxide and kerosene was designed and manufactured. Design requirements of a rocket engine were determined and main geometrical parameters of rocket engine were determined on the basis of fundament. Six coaxial swirl injectors were mounted on the multi-injector engine. Flow analysis in the hydrogen peroxide manifold was performed to minimize stagnation and recirculation zones. Finally, the optimized hydrogen peroxide manifold was manufactured and cold flow test was carried out to confirm mass flow rate per uni-element, spray pattern and atomization characteristics. The results of cold flow test showed that the mixing head design process was successful and enough to use as a essential database for the development of a full-scale engine.

• The Korean Journal of Pain
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• v.19 no.2
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• pp.159-163
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• 2006

Background: Despite the enormous amount of basic research on neuropathic pain, there is the lack of an objective diagnostic test for complex regional pain syndrome (CRPS). The aim of this study was to evaluate the usefulness of cold stress thermography in the diagnosis of CRPS. Methods: The study involved 12 patients with CRPS type 1, according to the IASP criteria, who were compared with 15 normal healthy volunteers. All subjects underwent thermographic examination under baseline conditions at $21^{\circ}C$. A cold stress test (CST; $10^{\circ}C$ water for 1 minute) was then applied to both hands below the wrists, immediate, and after 10 and 20 minutes. Results: The temperature asymmetry between the patients with CRPS and the volunteers showed significant discrimination at the baseline and after a 20 minute recovery period from the CST. Among the study subjects having temperature asymmetry of both hands of less than $1^{\circ}C$ (8 out of 12 CRPS patients and 14 out of 15 volunteer), 7 (87.5%) of the 8 CRPS patients and 3 (21%) of the 14 volunteers showed a temperature difference of more than $1^{\circ}C$ after the 20 minute recovery period. The actual temperature values during the four periods did not discriminate between the patients with CRPS and the volunteers. Conclusions: Thermography, under the CST, could be a more objective test for the diagnosis of CRPS. A temperature asymmetry greater than $1^{\circ}C$ during the 20 minute recovery period following CST provides strong diagnostic information about CRPS, with both high sensitivity and specificity.