• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.182-187
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• 2006

This research presented the heat resistance characteristics of heat sink which is newly designed through the experiment. For the same volume and base plate of heat sinks, the experiment of heat transfer characteristics was conducted for forced convection of layered type heat sink. The heat transfer and pressure drop characteristics of the layered type heat sink were compared for the various kinds of fin pitches, fin heights and heights of heat sink. The results show that thermal resistance is decreased as the height of heat sink increases and the fin height and fin pitch decrease, From the experimental data of layered type heat sink, the correlation equation of Nusselt number was obtained as follows ; $$Nu=0.845{\cdot}Re^{0.393}{\cdot}(\frac{f_h}{D_h})^{0.160}{\cdot}(\frac{f_p}{D_h})^{0.372}{\cdot}(\frac{H_{hs}}{D_h})^{-0.942}$$

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3112-3121
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• 2021

One of the major factors affecting the life span of a Reactor Pressure Vessel (RPV) is the Pressurised Thermal Shock (PTS). PTS is a thermo-mechanical load on the RPV wall due to steep temperature gradients and structural load created by internal pressure of the fluid within the RPV. Safe operating life of a nuclear power plant is ensured by carrying out fracture analysis of the RPV against thermal shock. Carrying out fracture tests on RPV/large scale components is not always feasible. Hence, studies on laboratory level specimens are necessary to validate and supplement the prototype results. This paper aims to study the fracture behaviour of standard Compact Tension [C(T)] specimens, made of RPV steel 20MnMoNi55, subjected to thermal shock through experimental and numerical investigations. Fracture tests have been carried out on the C(T) specimens subjected to thermal transient load and tensile load to quantify the effect of thermal shock. Crack resistance curves are obtained from the fracture tests as per ASTM E1820 and compared with those obtained numerically using XFEM and a good agreement was found. A quantitative study on the crack tip plastic zone, computed using cohesive segment approach, from the numerical analyses justified the experimental crack initiation toughness.

• 운동영양학회지
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• 제16권1호
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• pp.11-17
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• 2012

The purposes of this study were to investigate the effects of acute exercise on blood vaspin, glucose level, and inflammatory cytokines in middle-aged women with pre-diabetes. Nineteen middle-aged women (normal women, n = 11) and women with pre-diabetes(n = 8), who were apparently healthy and not taking any medications affecting their blood pressure or blood glucose, participated. Body fatness parameters including body mass index, body fat percentage, and waist circumference were measured using a bio-impedance analyzer. Resting blood pressure was measured in duplicate, and mean values were used for the data analysis. Regardless of group assignments, all subjects participated in a 3-day consecutive walking exercise at an intensity of 65% VO_2max targeting an energy expenditure of 1200 kcal (400 kcal per day). The major outcome variables included total cholesterol, triglycerides, high-density lipoprotein cholesterol, glucose, vaspin, interleukin-6, and adiponectin levels. Unlike normal women, women with pre-diabetes had a significant improvement in the homeostatic model assessment of insulin resistance (p < 0.025) with no significant group difference in response to acute exercise. The findings suggest that acute exercise results in a significant improvement in insulin sensitivity without any change in serum vaspin levels in women with pre-diabetes.

• 산업기술연구
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• 제25권B호
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• pp.63-71
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• 2005

This paper is an experimental result of investigating lateral soil movements at piled bridge abutments by using the centrifuge model facility. Three different centrifuge model experiments, changing the methods of ground improvement at bridge abutment on the soft clayey soil (no improvement, preconsolidation and plastic board drains (PBD), sand compaction pile (SCP) + PBD), were carried out to figure out which method is the most appropriate for resisting against the lateral soil movements. In the centrifuge modelling, construction process in field was reconstructed as close as possible. Displacements of abutment model, ground movement, vertical earth pressure, cone resistance after soil improvement and distribution of water content were monitored during and after centrifuge model tests. As results of centrifuge model experiments, preconsolidation method with PBD was found to be the most effective against the lateral soil movement by analyzing results about displacements of abutment model, ground movement and cone resistance. Increase of shear strength by preconsolidation method resulted in increasing the resistance against lateral soil movement effectively although SCP could mobilize the resistance against lateral soil movement. It was also found that installment with PBD beneath the backfill of bridge abutment induced effective drainage of excess pore water pressure during the consolidation by embanking at the back of the abutment and resulted in increasing the shear strength of clay soil foundation and eventually increasing the resistance of lateral soil movement against piles of bridge abutment.

• 대한조선학회논문집
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• 제47권5호
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• pp.689-696
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• 2010

Bulbous bow is one of the important design factors on the design of fore-body hull form. Using the interference technique of ship waves, the bulbous bow can decrease the wave resistance of ship. Recently, the goose neck bulb is applied mainly for high speed vessels like passenger ships and ferries etc.. Also, the goose neck bulb is applied for relatively high speed merchant vessels like container ships and LNG carriers. However, existing research papers about the goose neck bulb are not enough as reference data for the design of bow hull form. In this study, numerical calculations are carried out to investigate the bow wave characteristics of a high speed ferry with a normal high nose bulb or a goose neck bulb. By comparing the pressure distributions on the hull surface and the wave systems near the bow, the features of wave resistance reduction are discussed. Also, Numerical calculations were carried out for a series of goose neck bulbs to figure out the optimum bulb size. The maximum reduction rate of pressure resistance for the fore-body is achievable up to 8% by adopting the goose neck bulb in the present calculation.

• 대한물리의학회지
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• 제13권4호
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• pp.113-121
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• 2018

PURPOSE: This study was conducted to identify a more effective intervention in sling and resistance exercise for chronic low back pain patients. METHODS: Seventy (70) subjects were randomly divided into the sling group (SG) and resistance exercise group (REG). Muscular activity of the internal oblique (IO), external oblique (EO), rectus abdominis (RA), and pelvic rotation angle during active straight leg raise (ASLR), a pressure pain threshold (PPT) and a visual analog scale (VAS) were measured. Sling and resistance exercises were conducted for 12 weeks. Intermediate measurements were taken after 8 weeks and final measurements were taken after 12 weeks. RESULTS: Both groups showed significantly decreased RA muscle activity and significantly increased IO muscle activity (p<.05). Additionally, EO muscle activity was significantly decreased in the REG, but significantly increased in the SG (p<.05), while the pelvic rotation angle and VAS were significantly decreased in the SG (p<.05). The pressure pain threshold was significantly increased in both groups (p<.05). CONCLUSION: Based on the results of this study, a 12-week intervention seems to be effective at improving back pain in both groups. However, a lower VAS was seen in the sling group after 8 weeks of intervention. Therefore, it is recommended that the sling be applied first when establishing a chronic back pain treatment program to shorten the treatment period and reduce the pain period.

• 한국융합학회논문지
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• 제10권9호
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• pp.161-166
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• 2019

본 연구에서는 A, B, C 3가지 자동차 사이드미러 모델들에 있어서의 공기 저항으로 인한 유동을 분석을 함으로서 다양한 사이드미러들 주위에서의 흐름을 연구한다. 모델 A는 사각형 모양의 사이드미러이고, 모델 B는 삼각형 모양의 사이드미러, 모델 C은 타원형 모양의 사이드미러이다. 자동차의 사이드미러의 설계를 변경함으로서 운전 시 좀 더 사이드미러의 공기저항을 줄여서 약간의 자동차의 동력을 감소시킬 수 있다. 해석 결과로서, 사이드미러에 대한 공기저항의 압력이 클수록 공기 유동속도가 큰 것을 볼 수 있었다. 그러므로 공기저항의 압력이 작을수록 유동속도가 작고 공기가 더 잘 유통된다고 판단된다. 그러므로 Model B가 가장 좋은 Model이라는 것을 확인할 수 있다. 본 연구결과를 토대로 얻은 자동차 사이드 미러의 설계데이터를 활용함으로서 실생활에서의 자동차 운전시에 그 미적 감각을 나타낼 수 있다.

• 대한물리치료과학회지
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• 제25권3호
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• pp.17-24
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• 2018

Purpose: The purpose of this study was to investigate the effect of whole body vibration combined breathing resistance on lung capacity and respiratory muscle and to suggest a mediation method for improvement of respiratory function and lung function in the future. Methods: This study was a preliminary study design of two groups of 54 healthy young adults who were randomly assigned to an experimental group (n=27) with core exercise combined with respiratory resistance and whole body vibration and a control group with respiratory resistance and core exercise (n=27). All interventions consisted of 6 core exercises every 40 seconds and rest for 20 seconds. To compare the effects of intervention, we measured spirometry and respiratory muscle strength. Results: Both the experimental group and the control group showed a significant increase in Forced vital capacity (FVC) and Maximum voluntary ventilation (MVV) (p<.05). However, FEV1 and FEV1% were significantly increase only in the experimental group (p<.05). FVC, FEV1%, Maximum Inspiratory Pressure (MIP), Maximum Expiratory Pressure (MEP) showed more significant increase in the experimental group than the control group. Conclusion: These findings indicate that whole-body vibration combined breathing resistance is an effective intervention for people, with FVC, FEV1%, MIP, MEP increase.

• 대한물리치료과학회지
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• 제27권3호
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• pp.1-11
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• 2020

Background: The purpose of this study was to investigated the effects of threshold resistance inspiratory muscle training on respiratory function in chronic stroke patients. Design: Randomized Controlled Trial Methods: Eighteen patient with stroke were randomly assigned to the experimental group (n=9) and control group (n=9) all testing and training. The experimental group underwent threshold resistance inspiratory muscle training with resistance adjusted of maximal inspiratory pressure, 60 breathing a day and general physical therapy 30 minutes a day, 5 times a week for 4 weeks. The control group was taken general respiratory muscle training and general physical therapy for 4 weeks in the same way. Respiratory function, walking ability were evaluated before and after the intervention. Statistical significance of the results were evaluated by ANCOVA between control group and experimental group after intervention. Results: There was a significant increase in FVC and FEV1 in the experimental group in pulmonary function tests (p<0.05). There was a significant difference with the maximum inspiratory pressure and the maximum inspiratory flow rate between experimental and control group (p<0.05). There was no significant difference with the maximum inspiratory capacity between experimental and control group (p>0.05) but the maximum inspiratory capacity of experimental group some increased than that of control group. Conclusion: These finding gave some indications that the threshold resistance inspiratory training may benefit on pulmonary function in people with stroke, and it is feasible to be included in rehabilitation interventions with this population.

• Advances in concrete construction
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• 제14권3호
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• pp.205-214
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• 2022

Due to seawater's physical and chemical deterioration effects on concrete structures, it is crucial to investigate the durability of these structures in marine environments. In some conditions, concrete structures are exposed to seawater from the first days of construction or because of the lack of potable water, part of the concrete curing stage is done with seawater. In this research, the effects of exposure to seawater after 7 days of curing in standard conditions were evaluated. To improve the durability of concrete, fly ash has been used as a substitute for a part of the cement in the mixing design. For this purpose, 5, 15, and 30% of the mixing design cement were replaced with type F fly ash, and the samples were examined after curing in seawater. The resistance of concrete against chloride ion penetration based on the rapid chloride penetration test (RCPT), water permeability based on the depth of water penetration under pressure, and water absorption test was done. The changes in the compressive strength of concrete in different curing conditions were also investigated. The results show that the curing in seawater has slightly reduced concrete resistance to chloride ion permeation. In the long-term, samples containing FA cured in seawater had up to 10% less resistance to chloride ion penetration. The amount of reduction in chloride ion penetration resistance was more for samples without FA. Whiles, for both curing conditions in the long-term up to 15%, FA improved the chloride ion penetration resistance up to 40%. Curing in seawater slightly increased the penetration depth of water under pressure in samples containing FA, while this increase was up to 12% for samples without FA. In the long-term the compressive strength of samples cured in seawater is not much different from the compressive strength of samples cured in plain water, while at the age of 28 days, due to seawater salts' accelerating effects the difference is more noticeable.