• 대한조선학회논문집
• /
• 제31권4호
• /
• pp.119-129
• /
• 1994

본 연구의 목적은 좌초시 선저 보강판 부재를 대상으로 강체 웨지가 종방향으로 보강된 판으로 진입할 때의 흡수에너지-찢김길이 관계를 나타내는 실험식을 도출하는 것이다. 본 연구는 제1보에서 수행한 시리즈 실험 결과 및 찢김응답에 관한 주요 인자들의 중요도 조사 결과를 바탕으로 하고 있다. 준정적 하중상태에서 수행된 실험 결과를 바탕으로 무차원 해석을 수행하여 찢김이 진행되는 동안의 판부재의 흡수에너지를 찢김길이, 항복응력, 등가판두께, 웨지각도의 함수로 정식화하였다. 또한, 이식을 충격하중 작용시에도 적용할 수 있도록 동적 효과를 고려하였다. 특히, 본 연구에서는 동적 마찰 효과를 고려하기 위하여 동적 마찰 감소 계수의 개념을 도입하였다. 본 제안식의 유용성을 확인하기 위하여 기존의 제안식 및 충격 실험에 의해 얻어진 결과와 본 제안식의 결과를 비교하였다.

• 한국재료학회지
• /
• 제17권8호
• /
• pp.447-451
• /
• 2007

We investigated the dependence of the various annealing conditions and thickness ($6\sim45nm$) of the Ti-doped $Al_2O_3$ coating on the electrochemical properties and the capacity fading of Ti-doped $Al_2O_3$ coated $LiCoO_2$ films. The Ti-doped-$Al_2O_3$-coating layer and the cathode films were deposited on $Al_2O_3$ plate substrates by RF-magnetron sputter. Microstructural and electrochemical properties of Ti-doped-$Al_2O_3$-coated $LiCoO_2$ films were investigated by transmission electron microscopy (TEM) and a dc four-point probe method, respectively. The cycling performance of Ti-doped $Al_2O_3$ coated $LiCoO_2$ film was improved at higher cut-off voltage. But it has different electrochemical properties with various annealing conditions. They were related on the microstructure, surface morphology and the interface condition. Suppression of Li-ion migration is dominant at the coating thickness >24.nm during charge/discharge processes. It is due to the electrochemically passive nature of the Ti-doped $Al_2O_3$ films. The sample be made up of Ti-doped $Al_2O_3$ coated on annealed $LiCoO_2$ film with additional annealing at $400^{\circ}C$ had good adhesion between coating layer and cathode films. This sample showed the best capacity retention of $\sim92%$ with a charge cut off of 4.5 V after 50 cycles. The Ti-doped $Al_2O_3$ film was an amorphous phase and it has a higher electrical conductivity than that of the $Al_2O_3$ film. Therefore, the Ti-doped $Al_2O_3$ coated improved the cycle performance and the capacity retention at high voltage (4.5 V) of $LiCoO_2$ films.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2002년도 ITC-CSCC -1
• /
• pp.82-85
• /
• 2002

A compact rail to rail CMOS voltage follower is presented. The circuit is based on the symmetrical class AB voltage follower and can operate under supply voltages of ${\pm}$ 1.5 V. The proposed circuit has power dissipation of 5.2㎽ under quiescent condition and can drive ${\pm}$1.25 V to 250$\Omega$ load with a total harmonic distortion of less than 0.5 percent and cut off frequency of 237 ㎒. Although simple, the proposed circuit enables the output transistors to drive load efficiently.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 추계학술대회논문집
• /
• pp.261-264
• /
• 2003

Semi-solid processing is now becoming of great interest for the production of various parts by pressure die casting. Many advantages are associated with this forming process at the condition that the forming operation is performed under appropriate conditions. The thixoforming process, which needs a suspension of a globular, non-dendritic solid phase in the liquid phase, is characterized by three major steps. The first step is casting of billets with a microstructure suited for thixoforming. The second step is reheating of slugs cut from these billets. The third step is injection of the semi-solid slugs into a die. In this paper, the horizontal reheating machine to obtain the optimal conditions suitable for semiu-solid die casting process was used and applied to extrusion material. It is estimated the possibility of application on semi-solid die casting with extrusion material through various results.

• 한국정밀공학회지
• /
• 제17권2호
• /
• pp.58-63
• /
• 2000

The dynamics of spindle-bearing-workpiece system significantly affects the cutting condition and stability in milling process. The present paper investigates the chatter stability of milling process due to the change in the dynamics of spindle-bearing-workpiece systems. In particular, the present paper focuses on chatter stability due to the presence of gyroscopic effect. An eigenvalue problem approach to the stability of milling process is extensively used in this paper. To incorporate the rotational speed dependent gyroscopic effect, an iterative algorithm is proposed. A numerical example is provided for examining the chatter stability problem in the presence of gyroscopic effects.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
• /
• pp.360-365
• /
• 1995

The purpose of this study is to identify the various characteristics of the 53-years old railway tunnel linning concrete. The nondestructive technique such as the surface hardness method and the ultrasonic method, the extent of carbonation by the phenolphthalein indicator, and the chemical analysis due to XRD/XRF are considered Also the concrete core was cut in two pieces per tunnel for the exact evaluation of strength. On the basis of the experimental result, it is concluded that the durability and the serviceability of old tunnel linning concrete are affected by the initial mixing condition and the environmental effect.

• Smart Structures and Systems
• /
• 제4권5호
• /
• pp.517-530
• /
• 2008

This paper deals with civil infrastructures in general, sensor and smart structure technology, and smart steel structures in particular. Smart structures technology, an integrated engineering field comprising sensor technology, structural control, smart materials and structural health monitoring, could dramatically transform and revolutionize the design, construction and maintenance of civil engineering structures. The central core of this technology is sensor and sensor networks that provide the essential data input in real time for condition assessment and decision making. Sensors and robust monitoring algorithms that can reliably detect the occurrence, location, and severity of damages such as crack and corrosion in steel structures will lead to increased levels of safety for civil infrastructure, and may significantly cut maintenance or repair cost through early detection. The emphasis of this paper is on sensor technology with a potential use in steel structures.

• Elastomers and Composites
• /
• 제8권2호
• /
• pp.148-152
• /
• 1973

A study of preparing rubber soles and heels was made to improve the quality in their physical properties such as resistance of cut-growth, abrasion resistance and tensile strength. Following results were obtained in the characteristics of rubber compounding: 1. In the reinforcement effect of fillers, it was found that hydrous silcate and carbon black were the best, aluminum and calcium silicate were pretty good, and basic magnesium carbonate was moderate. 2. SBR/BR blend in the ratio of from 85/25 to 100/0 and NBR/BR blend in the ratio of from 60/40 to 20/80 were the most suitable compounding condition.

• 보존과학연구
• /
• 통권29호
• /
• pp.45-64
• /
• 2008

'No-An-Dang' in 'Un-Hyeun palace' was using as a guesthouse by 'dea-won-goon' built in 1864. 'No-An-Dang tablet' exhibited in 'No-An-Dang' seems to be made by using the letters which were written by 'Choo-sa Kim Jeong-Hee'. This tablet was manufactured by special processes; wood frame which was made of a Korean white pine was drawn patterns by variety pigment and latticed inside are joined with 3 of horizontal square wooden sticks and 7 of vertical square wooden sticks, then several sheets of the paper mulberry put on this frame and sheets cut along the edge of letter attached lastly. This structure of tablet could cause more conservation problems than only made in wooden structures. Therefore, replica was made and exhibited in bad condition and original one kept in museum storage for effective conservation of artefacts.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.1085-1088
• /
• 2001

The process of styrofoam pattern that has been used for material of press die pattern depends chiefly on handwork. Laser manufacturing system developed to increase precision and efficiency of process that is also able to convert the design easily. Applying the RP(rapid prototyping) concept reversely, the unnecessary part of section is vapored away by heat source of laser beam after converting 3-D CAD model into cross-sectional shape information. Laser beam is line-scanned in plane specimens to measure the depth and width of cut, surface roughness, cross-sectional shape as converting laser power, scanning speed, cutting gas pressure. With these basic data, plane surface, inclined surface, hole, outer contour trimming process is experimented and optimum condition are obtained. In plane and inclined surface experiments, 15W laser power and 50mm/s scanning speed make superior processing property and 30W, 10mm/s make processing efficiency increase in trimming process. With these results, simple patterns were manufactured and the possibility of applying laser manufacturing system to styrofoam pattern was convinced.