• Carbon letters
• /
• 제7권2호
• /
• pp.114-118
• /
• 2006

Isotropic pitch-based carbon fiber has been activated by steam diluted in nitrogen in order to characterize the microporosity. Especially, 40 wt% burn-off ACFs were prepared from different conditions to compare the pore structure and size. The ACFs were thinly sliced to investigate the inside pores by TEM and image analyzer. As expected, the adsorption characteristics of these ACFs were quite different from one another because of different pore structure and size. Most pores are not slit-shaped but rather round. Small round micropores become broad and irregular as increasing the activation time and temperature.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
• /
• pp.554-554
• /
• 2000

To improve mechanical properties of Cu-Al-Ni alloy by the grain refinement, Cu-Al-Ni SMA ribbons were fabricated by melt spinning apparatus. The variations of microstructure, mechanical properties and transformation characteristics with the condition of rapid solidification and annealing time-temperature were investigated in Cu-Al-Ni SMA ribbons. The ribbons fabricated by melt spinning obtained around 1.5nm in width and 50-60${\mu}{\textrm}{m}$ in thickness. With increasing wheel speed in order of 10m/s, 15m/s, 20m/s, 30m/s and 3m/s, the grain size was decreased in order of 10${\mu}{\textrm}{m}$, 6.25${\mu}{\textrm}{m}$, 5.5${\mu}{\textrm}{m}$, 3${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$. $M_{s}$ and $A_{s}$ temperature were decreased with decreasing grain size. By X-ray diffraction test, ordered $\beta$$_1$ phase was observed in all the SMA ribbons and the volume friction of it was increased with increasing wheel speed. With increasing wheel speed, strain was increased from 4.2% to 5.8% and fracture mode has changed from mixture of intergranular and dimple fracture to mixture of fiber structure and dimple fracture. The grain size of ribbon heat-treated at $600^{\circ}C$ was increased with increasing time. In the heat-treated ribbons at 55$0^{\circ}C$, ${\gamma}$$_2$ phases were observed.d.d.

• Journal of Advanced Marine Engineering and Technology
• /
• 제26권1호
• /
• pp.76-82
• /
• 2002

In this study, the rotary bending fatigue test was carried out with low carbon steel(SM25C). The specimens were heat-treated in order to change the grain size, and investigated items are fatigue limit, small crack initiation, fatigue crack propagation behavior and possibility of fatigue life prediction according to the different grain size. The summarized result are as follows ; Fatigue limit of the smooth specimen was dependent upon the grain size. The fatigue crack initiation of the small grain size specimen was delayed more than that of the large grain size specimen. And the small cracks of small grain size specimen were distributed in the narrow region of the main crack circumference contrary to the large grain size specimen. The main crack was grown along the grain boundary having co-alliance with small cracks. The experiment material has quantitatively disclosed the possibility of fatigue life prediction because the fatigue crack propagation behavior is dependent upon the grain size.

• Journal of electromagnetic engineering and science
• /
• 제13권4호
• /
• pp.263-266
• /
• 2013

A novel compact and low-loss VHF bandpass filter is presented with enhanced stopband performance using metamaterial zeroth order resonator (ZOR) characteristics. An in-line ZOR filter is initially suggested and changed to have transmission zeros (TZs) due to source-load coupling for effective improvement of the isolation from UHF wireless channels. The proposed filter is smaller than 1/10 of the conventional filters in terms of size and has relatively very low insertion loss (< 1 dB for the electromagnetic (EM) simulation and < 3 dB for the measurement) and return loss (<-20 dB) in the passband due to the approximately 80% size reduction and the higher isolation in the stopband due to the TZs. The circuit and EM simulation are in good agreement with the measurements.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.1115-1122
• /
• 2011

Reinforced-Roadbed materials are usually composed of crushed stones. Repeated load application can induce deformation in the reinforced-roadbed layer so that it causes irregularity of track. Thus it is important to develop a prediction model of elastic modulus based on stress-strain relation under repeatitive load in order to investigate behavior of reinforced roadbed. The prediction model of elastic modulus of the material can be obtained from repeated triaxial test. However, a proper size of the sample for the test must be used. In this study, a large repeatitive triaxial test apparatus with the sample size of diameter of 30 cm and height of 60cm was adapted for performing test of the crushed stone reinforced-roadbed considering large particle size to get resilient modulus Mr. The obtained resilient modulus was compared to shear modulus obtained from mid size resonant column test. The sample size effect is somewhat large enough so that it is required to design a scale factor based on similarity law in order to use smaller samples for getting elastic modulus of the crushed stone reinforced-roadbed material. A scale factor could be obtained from this study.

• 한국의상디자인학회지
• /
• 제5권1호
• /
• pp.85-88
• /
• 2003

In order to design a good ready-made cloth, it is important to consider not only body size but also morphological factor. However, most dissatisfaction of customer is focusing on the size of ready-made cloth which is graded with elements of body size. Various researches on body type have been doing but the study on part of body type is insufficient compared to the study on whole body type. The objective of this paper is to provide relationship of shoulder angle between value in pattern and real measured value after analysis and comparison with these two values.

• 한국세라믹학회지
• /
• 제21권3호
• /
• pp.209-216
• /
• 1984

The influence of the particle size of quartz and the change of cooling rate to the strength of conventional triaxial porcelain was studied, . The results indicate that 1. The residual quartz content was increased by particle size increasing. And the strength was increased by increas-ing residual quartz content which increased the total stress in the specimen. But the influence of residual quartz was lessened by the extent of crack between quartz particle and glass matrix 2. In order to increase the strength of the body fast cooling is suitable to small quartz particle and slow cooling is suitable to large quartz particle.

• 한국통신학회논문지
• /
• 제25권10B호
• /
• pp.1648-1664
• /
• 2000

This paper proposes a real-time dynamic storage allocation algorithm QSHF(quick-segregated-half-fit) that provides various memory allocation policies. that manages a free block list per each word size for memory requests of small size good(segregated)-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per each power of 2 size for large size requests. The proposed algorithm has the time complexit O(1) and makes us able to easily estimate the worst case execution time(WCET). This paper also suggests two algorithm that finds the proper free list for the requested memory size in predictable time and if the found list is empty then finds next available non-empty free list in fixed time. In order to confirm efficiency of the proposed algorithm we simulated the memory utilization of each memory allocation policy. The simulation result showed that each policy guarantees the constant WCET regardless of memory size but they have trade-off between memory utilization and list management overhead.

• 한국콘텐츠학회논문지
• /
• 제21권4호
• /
• pp.331-346
• /
• 2021

본 연구는 국내 캡스톤 디자인 교육이 학업성과에 미치는 효과를 종합적으로 분석·평가하여 캡스톤 디자인 수업이 효과적으로 이루어지기 위한 설계 및 실행방향을 제안하는 데 목적이 있다. 이를 위해 2020년 9월까지 국내에서 발표된 캡스톤 디자인 수업 효과 관련 학술지 및 학위논문 중 기준에 부합하는 총 21편의 연구를 선정하고 83건의 효과크기를 토대로 메타분석을 진행한 연구 결과는 다음과 같다. 첫째, 캡스톤 디자인 교육의 학업성과에 대한 전체 효과크기는 0.96으로 큰 효과크기로 나타났다. 둘째, 학업성과 영역별 효과크기 분석 결과 인지적, 정의적, 사회적 영역 모두에서 효과가 유의하게 나타났으며, 효과크기는 정의적·인지적·사회적 영역 순으로 나타났다. 셋째, 학업성과 변인별 효과크기에서 직업기초능력은 큰 효과크기, 창의성은 중간 효과 크기로 나타났다. 넷째, 캡스톤 디자인의 학습효과는 교과목, 학년, 산업체 협력유무, 수업유형, 팀원 수에 영향을 받는 것으로 나타났다. 본 연구는 이러한 연구 결과를 바탕으로 향후 국내 캡스톤 디자인 교육의 효과를 높이기 위한 교수설계적 시사점을 제안하였다.

• 교육시설
• /
• 제6권2호
• /
• pp.5-12
• /
• 1999

This study aims to propose some alternatives in architectural planning for reducing the class size of elementary, middle and high schools. In order to achieve above purpose, I discuss the current status of class size, the relationship between class size and educational outputs and the obstacles in realizing the optimum class size of elementary, middle and high schools during the past 40 years. Finally, the paper proposes 8 alternatives in reducing the class size, which can be considered during the early stage of school planning.