• 한국정밀공학회지
• /
• 제17권10호
• /
• pp.56-62
• /
• 2000

A fast and precise technique to make 3-dimensional object which is called direct metal shaping process is processed. It is very useful technique in design and inspection. Using this developed system, a solid object is made. In experiment, test parts are built by varying three factors, laser power, scan path, scan speed. This process used device, which is different from the widely used in rapid prototyping in that powder feeding device is used. Spraying powder directly at the focused laser beam and then three dimensional object is made by the deposit of melted metal powder. The optimum scanning path is found to be zigzag path, which had little thermal affection on base metal. As a result of these experiments, it was found that optimum scanning speed is 15mm/sec laser power is 50W. This constructed 3-dimensional object could be used in mold manufacturing directly.

• PNF and Movement
• /
• 제15권3호
• /
• pp.281-290
• /
• 2017

Purpose: The purpose of this study was to examine the effect of an 8-week competitive exercise program on physical fitness, psychological variables, and video-game playtime in game-addicted adolescents. Methods: All subjects were screened by a game behavior diagnosis scale questionnaire, and a total of 7 game-addicted, male adolescents ($16{\pm}2$ yrs of age) participated in the study. All subjects were informed of the study's purpose, procedures, and risks, and a consent form was obtained from each subject. The 8-week soccer and basketball exercise program included twice-weekly sessions of 120 minutes per session. All data were presented as $mean{\pm}SE$, and the variables were analyzed with a paired t-test. Results: Following the 8-week intervention, cardiovascular endurance and grip strength were significantly increased (approximately 17 and 7%, respectively [p<0.05]). Although there was no statistical significance on flexibility, vertical jump, and zigzag-run, all variables showed an increasing tendency. Anxiety levels changed from a mild anxiety state to a normal state, and depression levels also altered from moderate to a normal state. The video-game playtime was reduced about 20% during weekends and vacation periods. Conclusion: Given these combined results, 8 weeks of regular participation in competitive exercise (soccer/basketball) may contribute to positive effects on physical fitness, psychological variables, and video-game playtime in computer-game addicted adolescents.

• 대한조선학회논문집
• /
• 제42권6호
• /
• pp.551-558
• /
• 2005

In this paper, horizontal manoeuvrability of an underwater vehicle near free surface was investigated. Planar Motion Mechanism(PMM) tests were performed at the shallow depth within 4.5 times of vehicle's diameter. Hydrodynamic coefficients related to the horizontal movement were estimated from the measured data using Least SQuare(LS) method and analyzed at each submerged depth. Furthermore, horizontal dynamic stability, trajectory of turning and zigzag test were investigated for the various depths. As underwater vehicle is positioned nearer to the free surface, forces increase and moment decreases. Tested model was found to be stable only at the depth 0.5 times of vehicle's diameter.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
• /
• pp.2140-2142
• /
• 2005

This paper presents the experimental results on the preliminary breakdown characteristics under a highly non-uniform electric field in $SF_6/CO_2$ gas mixtures. The impulse preliminary breakdown developments are investigated by the measurements of corona current and light emission images. As a result, the preliminary breakdown development mechanisms for both positive and negative polarities are same. The first streamer corona is initiated at the tip of needle electrode, and the leaders develop with a stepwise propagation and bridge the test gap. The pause time of leader pulses in the positive polarity is significantly shorter than that in the negative polarity. Also, the time interval between the first streamer corona onset and breakdown in the negative polarity was much longer than that in the positive polarity The discharge channel paths in the positive polarity were zigzag. On the other hands, the leader channel in the negative polarity was thicker than that in the positive polarity.

• 한국의류학회지
• /
• 제42권3호
• /
• pp.474-485
• /
• 2018

Smart sensors and connected devices have changed the concept of garments along with IT technology convergent garments that transform the performance of basic functions. Various types of products have been researched and developed due to the increased interest in smart clothing; in addition, studies based on physical and mechanical properties have also been actively studied to improve accuracy and reliability. This study represents a basic study for the development of smart textiles based on motion recognition for the surfing practice of beginners interested in IT convergence type. A physical durability evaluation of conductive yarn according to sewing method was later carried out. This study is a conditional specimen sewn with cotton lower thread and 100mm pattern length based on the results of previous studies. The durability of the conductive yarn according to the sewing method was evaluated according to the sewing method. Durability was evaluated by two kinds of repeated strain and abrasion tests. The specimen with applied cotton in a lower thread zigzag pattern 2mm stitch size 100mm stitch length was shown to have the most suitable durability for smart textile.

• 소성∙가공
• /
• 제30권6호
• /
• pp.284-290
• /
• 2021

Manufacturing using a 3D printer has recently increased in many fields and the material extrusion method, which is a lamination method, is commonly used. Since it uses a plastic material, the strength of the output of 3D printing is lower than that of steel material. For this reason, research on improving the mechanical properties of the output of 3D printing is continuously being conducted. In this study, tensile strength was compared with changes in the material type (PLA+, ABS) and density (60, 80, and 100%), layer height (0.1, 0.2, and 0.3 mm), layer direction (transverse and lengthwise), and fill pattern (zigzag, honeycomb, and concentric) among 3D printing output conditions. Tensile tests according to 3D printing output conditions were performed using a Universal Testing Machine. The results showed that tensile strength ranged from 21.10 MPa to 43.65 MPa according to the 3D printing output conditions.

• 한국균학회지
• /
• 제29권1호
• /
• pp.34-40
• /
• 2001

Entomogenous fungi의 수집된 14균주를 대상으로 종내 그룹의 상호 유연관계를 분석하고자 자실체 및 불완전세대의 형태적, 배양적 특징 관찰과 RAPD 검정을 실시하였다. Paecilomyces tenuipes는 수 없이 많은 흰색 분생포자가 자실체에 불어 눈꽃모양을 나타냈으며, 곤봉형 phialides위에 구형 또는 타원형의 분생포자가 연쇄상을 이루었다. Cordyceps militaris는 담황색 자실체가 방망이 모양으로 번데기에서 형성되었으며, 불완전세대는 Verticillium으로 단생의 phialides에 구형의 분생포자가 Acremonium-type으로 부착되어 있었다. Beauveria bassiana는 자루에서 여러마디가 이어지며, 각 마디에서 1개씩 분생포자가 붙어있는 zigzag type이었다. 또한 이들의 배양에 적합한 배지는 PDA, SDAY이며, 평면과 단면구조로 Paecilomyces는 벨벳과 평탄, Cordyceps는 양모상과 중앙융기로 생육하였고, Beauveria는 벨벳에 밀가루를 뿌린 모양이었다. URP primer를 이용한 rDNA의 RAPD분석 결과 증폭된 산물의 크기는 100bp에서 2.0kb사이로 genomic DNA fragment는 $10{\sim}14$개이었다. UPGMA 분석에 의한 dendrogram 작성 결과 다양한 유전적 분화를 나타내었으며, 2개의 군으로 그룹화 하였다. P. tenuipes 그룹의 $94.8{\sim}100%$, C. militaris와 C. scarabaeicola, B. bassiana 그룹은 $54.3{\sim}$100%의 상동성을 보였다. 또한 완전세대의 자실체를 형성하는 C. militaris 그룹은 불완전세대인 P. tenuipes와 B. bassiana보다 종내의 변화의 폭이 컸으며, 종내의 세분화가 이루어졌다.

• 해양환경안전학회지
• /
• 제17권4호
• /
• pp.383-389
• /
• 2011

선박 성능과 항해 안전의 관점에서 선박조종 특성을 아는 것은 선박 설계에서 중요한 일이다. IMO 규정에 의하면 만재 적하된 even 조건(트림=0)에서 몇가지 선박 조종 기준이 제시되어 있다. 그러나 선박은 일반적으로 항상 만재 적재 조건으로 운항되지 않는다. 따라서 선박이 IMO 규정을 만족시키고, 모든 적재 조건에서 안전하게 항행하도록 하기 위해 다양한 적재 조건에서 선박 조종 특성을 추정해야 한다. 본 논문에서 우리는 실선 실험과 시뮬레이션을 수행하여 조종특성을 조사하였다. 시뮬레이션 결과와 비교하였을 때 실선실험은 시뮬레이션 값 및 이전 연구와 그 경향이 일치한다. 실 해역에서 얻은 조종실험 데이터가 선박 조종성능 추정에 활용 될 수 있음을 확인하였고, 실시한 실해역 실험을 통하여, 선박 운항 상태에 따른 조종성의 변화를 추정할 수 있었다.

• 수산해양기술연구
• /
• 제47권4호
• /
• pp.435-442
• /
• 2011

In an attempt to respond to the increase in international oil prices and reduce operating expenses, ship remodeling was carried out on a 740ton class tuna purse seiner. To strengthen the competitiveness of the fisheries industry by improving vessel performance, a bulbous bow was newly equipped. The slipway and rudder area were also lengthened and enlarged with the propeller and main engine remained unchanged. To reduce the hull resistance, a circle type bulbous bow was attached on the hull behind bow thruster and thus the cost for exchanging electrical equipment for bow thruster was reduced. The new rudder area was expanded 15% more than the old one within the extent that the existing mechanical control part and rudder stock were not changed. To prevent fishing net damage and stabilize wake field, slipway was lengthened to the optimal position. All of the new design of remodeling parts went through the model tests in towing tank and CWC. Besides resistance test, all of necessary model test results were delivered for hydrodynamic character for the modified ship. The maneuvering simulation to verify that the remodeled ship satisfies the IMO rules was performed in both zigzag and turning tests. The estimated resistance with new bulbous bow and lengthened stern was reduced by 4.8% in the 2-dimensional analysis and 17.4% in the 3-dimensional analysis in comparison of conventional ship. The average reduction of resistance was estimated about 10%. Maneuvering character of modified hull form was found to satisfy all regulations under IMO. The remodeling of tuna purse seiner can not only improve fishing performance but also contribute to reduction of operating cost by saving energy for the fisheries industry.

• 대한공간정보학회지
• /
• 제14권4호통권38호
• /
• pp.11-18
• /
• 2006

본 논문은 항공 LiDAR 데이터의 정확도를 수평과 수직으로 구분하여 현지의 측량기준점을 이용하여 평가하였다. 항공 LiDAR 측량은 좌우 스캔방식에 의한 레이저 포인트를 취득하므로, 미리 측량된 점과 정확히 일치하는 포인트를 획득하기가 어렵다. 따라서 본 연구에서는 현지 측량점 주변에 위치한 점들을 종합적으로 이용하여 비교, 평가를 실시하였다. 수평위치의 정확도는 LiDAR 포인트로부터 각 건물면에 대한 평면방정식을 구성하여 모서리 점에 대한 좌표를 산출하여 현지 측량점과 비교한 결과, 평균오차 19cm, RMSE 21cm로 나타났으며, 16점 중에서 15점이 20cm 이내의 오차를 보였다. 수직위치의 정확도는 총41점에 대해 현지에서 측량한 검사점의 높이값을 이용하여 수직위치를 평가한 결과, 평균오차 10cm, RMSE 14cm로 나타났으며, 총 검사점의 75%가 15cm 이내로 오차를 보였다. 따라서 본 연구 결과를 바탕으로 향후 수치지형도 수정 갱신, 기본지리정보 및 삼차원공간정보 구축 등 LiDAR 데이터의 정확도에 따른 활용범위를 산정할 수 있을 것으로 판단된다.