• 한국운동역학회지
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• 제28권3호
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• pp.151-158
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• 2018

Objective: In this study, we analyzed kinematic changes in the start phase of speed skating before and after physical training. Method: We introduced a new strength training program (2017) that was improved in terms of exercise type and intensity [%, one repetition maximum (1RM)] compared with the previous strength training program (2016). The new program was applied to elite speed skating athletes (four males and four females). To determine the improvement in starting technique, we recorded race images during the start phase of the 500-m race held in 2016 and 2017. The race images were collected using five high-speed cameras and kinematic characteristics of the start phase were analyzed by three-dimensional image analysis. Results: The 1RMs were improved by 11% on an average after the strength training. In 2017, records of four out of the eight athletes were shortened in terms of the initial lap time (100 m), and 500-m records were shortened in six athletes. The time to nine strokes was shortened in five athletes, and the ratio of correct kinetic chain was increased or maintained at a high level in six athletes. Conclusion: In this study, the new strength training program (2017), applied to elite speed skating athletes, showed a positive effect on starting technique and reduced the record times.

• 한국레이저가공학회지
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• 제14권2호
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• pp.1-7
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• 2011

The latest trends of vehicle technology development are fuel efficiency improvement, body designs declining air resistance and lightweight of materials. Especially, as lightened weight of materials makes engine efficient so that vehicles keep the best performance, it is the best way to protect the environment and reduce fuel consumption. In this study, we conducted laser welding by using 3-dimension remote scanner that is 5J32 aluminium alloy. Furthermore, conduction experiment that was 3 times repeated for changing factors such as observing angle, laser power and welding speed. we observed exterior and cross section of weled part and tensile strength. When increasing laser power and decreasing laser speed, tensile strength increased. In order to evaluate factors that affect tensile strength qualitatively we conducted ANOVA. We assumed that the factors are observing angle, laser power and welding speed. Then we found that laser power and laser speed affect tensile strength. We conducted evaluation of weldability of aluminium alloy by above ways.

• 인터넷정보학회논문지
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• 제3권1호
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• pp.91-99
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• 2002

많은 기업 및 기관들이 그들의 업무정보를 인터넷을 통해 공유함에 있어서 얼마나 원하는 정보를 정확하게 그리고 신속하게 검색할 수 있는가에 대한 관심이 높아지고 있다. 따라서 업무정보의 신속한 저장, 검색 및 관리를 지원하기 위한 디렉토리 서버의 표준으로 LDAP 프로토콜이 제안되었고 이미 세계적 표준으로 자리 잡아 가고 있는 실정이다. 하지만 기존의 LDAP 프로토콜만으로는 서버의 과부화 및 데이터 동기화 등의 문제에 효과적으로 대처하기 어렵다. 본 연구에서는 LDAP의 등장 배경 및 특징에 대해 살펴보고 LAP 운용환경에서 발생할 수 있는 서버의 과부하와 데이터 동기화 문제를 해결하기 위하여 서버 독려형 방식의 아키텍쳐를 제안하고 그 특징을 기술한다. 특히 서버 독립형 방식은 기존의 LDAP 아키텍쳐 위에 설계되었기 때문에 확장성과 이식성도 함께 보장할 수 있다는 장점이 있다.

• 동력기계공학회지
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• 제3권1호
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• pp.16-22
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• 1999

The purpose of this study is to prevent the stick, scuffing, scratch between piston and cylinder, is to contribute the piston design such as piston profile, clearance by calculating reaction force by over-lap of piston skirt, as measuring the temperature distributions of cylinder wall. The experiment has been peformed to obtain data during actual engine operation. Temperature gradient in peripheral and axial distributions of cylinder wall according to torque and speed of engine were measured by use of an 800cc class gasoline engine. The results obtained are summarized as follows ; 1) The temperature of cylinder wall at TDC was about $50{\sim}75^{\circ}C$ higher than temperature of cooling water. 2) The rear side temperature of top dead center was $141^{\circ}C$(1/4 load) in axial distribution, whereas the rear side of midway position temperature was $98^{\circ}C$. 3) The temperature of cylinder wall increased in according to rising temperature of cooling water. 4) The thrust side temperature of cylinder wall was about $15^{\circ}C$ in all load test. 5) The rear side temperature of top dead center was $159^{\circ}C$ (1/2 load) in peripheral distribution, it was about $39^{\circ}C$ higher than thrust side temperature.

• Journal of Welding and Joining
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• 제31권4호
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• pp.7-12
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• 2013

The dissimilar welding between magnesium alloy and steel sheet was required in automobile industry to increase the strength of the dissimilar joints. Laser brazing is one of the good joining processes for Mgsteel dissimilar joint. In this study, the effect of coating materials was evaluated on the laser brazing for the dissimilar joint between AZ31 and coated steels such as Zn, Sn and Ni. Diode direct laser was used to braze the lap-edge joint with Mg600 filler wire and Superior #21 flux. The wettability was best on Zn coated steel. The interlayer was formed at the interface between brazement and steel for all coating materials. The strengths of brazed specimen were 146.5N/mm, 204.6N/mm and 101.6N/mm for Zn, Sn and Ni coated steel respectively.

• 소성∙가공
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• 제32권6호
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• pp.360-366
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• 2023

This study is concerned with the surface quality of products according to the material and coating condition of the forming tool in incremental sheet forming. Three forming tools, SKD11 with and without diamond-like-coating (DLC) and polymer tool tip, were used to form conical and pyramidal geometries to take into account the influence of friction between the forming tool and the sheet on the surface quality including geometric accuracy of deformed samples. Each test was performed using SUS304 with a thickness of 0.4 mm according to different incremental depths per lap of 0.5 mm, 1.0 mm, and 1.5 mm for the contour tool path, considering the increase in normal force which is associated with the frictional behavior during local deformation. The surface quality was then investigated through surface roughness measured with KEYENCE VR-6000 and relative strain distribution including deformed shape analyzed with ARGUS which is a non-contact optical strain measurement system. Differences between 3D CAD surfaces and captured geometry from experiments were evaluated to compare the effect of friction on geometric accuracy. From comparisons of experimental results, it was revealed that the polymer-based tool tip can improve surface quality and geometric accuracy by reducing the undesired material flow due to local friction in the increment sheet forming process.

• Computers and Concrete
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• 제33권5호
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• pp.519-533
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• 2024

Many materials including cementitious concrete-type materials undergo material property changes during high-rate loading. There is a wealth of research regarding this phenomenon for concrete in compression and tension. However, there is minimal knowledge about how mortar material used in concrete masonry unit (CMU) construction behaves in high-rate shear loading. A series of experiments was conducted to examine the bond strength of mortar bonded to CMU units under high-rate shear loading. A novel experimental setup using a shock tube and dynamic ram were used to load specially constructed shear triplets in a double lap shear configuration with no pre-compression. The Finite Element Method was leveraged in conjunction with data from the experimental investigation to establish if the shear bond between concrete masonry units and mortar exhibits any rate dependency. An increase in shear bond strength was observed when loaded at a high strain rate. This data indicates that the CMU-mortar bond exhibits a rate dependent strength change and illustrates the need for further study of the CMU-mortar interface characteristics at high strain rates.

• 한국정밀공학회지
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• 제30권2호
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• pp.154-163
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• 2013

Adhesive bonding and plastic welding have been widely used to join two plastic materials together. The goal of this paper is to determine a proper joining technology of a pair of flat panel (FP) photobioreactor (PBR) case. The material of the FP PBR case is polycarbonate (PC) plate. Two types of adhesion, including acryl adhesive and two-part epoxy adhesive, as well as two types of plastic welding technology, including ultrasonic welding and thermal welding, are employed for joining of PC plates. In order to influence of the adhesion and welding conditions on the joining characteristics of the PC plates in operational conditions of the FP PBR case, the morphology in the vicinity of the joined region as well as the water and pressure resistance characteristic are investigated. In addition, the variation of the bonding strength of the joined region and deformation behaviors in the vicinity of the joined region according to the adhesion and welding conditions is examined via the lap-shear test. From the results of basic experiments, proper joining technologies are chosen. Using the chosen joining technologies, the FP PBR case are fabricated to perform full-scale durability experiment. The results of the full-scale durability experiment have been shown that the chosen joining technologies can be applicable to fabricate the FP PBR case.

• 재활간호학회지
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• 제9권1호
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• pp.5-14
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• 2006

Purpose: This research was conducted to explore the relationship between spiritual well being and life attitude among breast cancer patients who were operated, and to increase understanding for wholistic nursing care. Method: With spiritual well being from quality of life questionnaire in breast cancer survivors (QOL-BR 23) of Ferrell et al (1998) and Life attitude profile (LAP) of Recker & Peacock (1981), the data were collected by research assistant in a sample of 56 women with stage 1-stage 3 breast cancer at surgery OPD after follow-up care. Result: Mean spiritual wellbeing score of subject was 5.83 (0-10) and life attitude was 4.96 (1-7). There were significant differences in life attitude according to monthly income (F=3.22, p=.03), and in spiritual wellbeing according to monthly income (F=4.16, p=.01) and religion (t=-3.67, p=.001) among demographic characteristics. There was significant difference in spiritual wellbeing according to the period passed after operation (F=2.89, p=.04) among disease characteristics. From life attitude domain, the mean score of "will to meaning" was the highest (5.30) and "existential vacuum" was the lowest (4.58). There was a significant relationship between spiritual wellbeing and "will to meaning" subscale of life attitude (r=.521, p=.000). The correlation coefficient showed r= .513 between spiritual well being and life attitude. Conclusion: Nurses could promote positive life attitude for breast cancer patients by improving spiritual well being with the encouragement of having religion expecially for long term breast cancer survivors in the process of their rehabilitation.

• Journal of Gastric Cancer
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• 제19권2호
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• pp.193-201
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• 2019

Purpose: There is no consensus on the optimal method for intracorporeal esophagojejunostomy (EJ) in laparoscopic total gastrectomy (LTG). This study aims to compare 2 established methods of EJ anastomosis in LTG. Materials and Methods: A total of 314 patients diagnosed with gastric cancer that underwent LTG in the period from January 2013 to October 2016 were enrolled in the study. In 254 patients, the circular stapler with purse-string "Lap-Jack" method was used, and in the other 60 patients the linear stapling method was used for EJ anastomosis. After propensity score matching, 58 were matched 1:1, and retrospective data for patient characteristics, surgical outcome, and post-operative complications was reviewed. Results: The 2 groups showed no significant difference in age, body mass index, or other clinicopathological characteristics. After propensity score matching analysis, the linear group had shorter operating time than the circular group ($200.3{\pm}62.0$ vs. $244.0{\pm}65.5$, $P{\leq}0.001$). Early postoperative complications in the circular and linear groups occurred in 12 (20.7%) and 15 (25.9%, P=0.660) patients, respectively. EJ leakage occurred in 3 (5.2%) patients from each group, with 1 patient from each group needing intervention of Clavien-Dindo grade III or more. Late complications were observed in 3 (5.1%) patients from the linear group only, including 1 EJ anastomosis stricture, but there was no statistical significance. Conclusions: Both circular and linear stapling techniques are feasible and safe in performing intracorporeal EJ anastomosis during LTG. The linear group had shorter operative time, but there was no difference in anastomosis complications.