• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.32-37
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• 2003

The trend of miniaturization has been applied to the research on micro rockets resulting in prototype rockets fabricated by MEMS processes. In this paper, the development of three-dimensional micro rockets using micro milling as well as the results of combustion and flight tests are discussed. The body of rocket was made of 6061 aluminum cylinder. The three-dimensional micro nozzles were fabricated on brass by micro endmill with 127${\mu}m$ diameter. Two different micro nozzles were fabricated, one with 1.0mm of throat diameter and the other with 0.5mm. The total mass of rocket was 7.32g and that of propellant was 0.65g. The thrust-to-weight ratio was between 1.58 and 1.74, and the flight test with 45 degree launch angle form the ground resulted in 46m-53m of horizontal flight distance

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.175-180
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• 2019

In order to overcome the drawbacks of low rated power of the string inverter, the necessity of micro -inverters and future development directions will be examined by comparing the power conditioner system with existing PCS using micro inverter. Currently, string inverters have been used in household solar power generation systems, and research and penetration of micro-inverters(PV-MIC) have been expanding, which can overcome the shortcomings of string inverters starting from Europe. However, in the PV inverter industry, precise technical standards, test measurement equipment and related test methods for micro-inverters(PV-MIC) are obstacles to product development. Therefore, in this paper, considering the characteristics of micro-inverter (PV-MIC), it aims to make it competitive so that it does not lag behind advanced technology change through test measurement equipment and related technical standard.

• Journal of the Korean GEO-environmental Society
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• v.22 no.4
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• pp.15-23
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• 2021

Various micropiles have been developed through research related to micropiles, which have been carried out with the increased use of micropiles. Among the micropile construction methods being developed, the triaxial micropile (tmp), which is recently developed for the purpose of increasing the horizontal bearing capacity (seismic resistance), is representative. The three-axis micropile has the advantage of a method that can resist horizontal load more effectively because three micropiles installed inclined on each axis resist horizontal load. However, there is a problem in effectively using this pile method due to insufficient research on the support characteristics of the triaxial group micropile. In order to effectively utilize the triaxial group micropile (tmp), it is required to evaluate the bearing capacity for the factors that affect the horizontal bearing capacity of the pile. Therefore, in this study, field horizontal loading Tests were performed for each load direction, field loading Tests were verified through three-dimensional finite element analysis, behavioral characteristics of triaxial micropiles were evaluated, and appropriate horizontal bearing capacity was analyzed in consideration of horizontal load directions.

• Journal of the Korean GEO-environmental Society
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• v.9 no.7
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• pp.61-71
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• 2008

This study investigates the lateral resistance of micro-pile system when surcharge load is acting on the back of retaining wall. Both laboratory experiments and numerical analysis were performed. The experimental retaining wall model was developed on the laboratory-sized foundation. While surcharge load was acting, the interval and length varied as experimental variables. From the investigation it is known that the micro-pile system can effectively control the lateral displacement which is developed on the precast retaining wall. The effectiveness became increased as the pile interval reduced and the length of pile increased. The greatest reinforcing efficiency was shown when the pile length was 0.5H and the interval was 7D.

• Journal of the Microelectronics and Packaging Society
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• v.5 no.2
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• pp.21-26
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• 1998

대용량, 고속데이터 처리가 요구되는 System 개발은 이들의 복잡하고 고기능의 회 로 구현이 가능하냐에 달려 있고 또한 이들고기능 요구를 가장 잘 만족할수 있는 패키지는 MCM 이라 할 수있다. 시스템의 고속화, 소형화는 회로의 복잡성을 요구하는 있는 이를 패 키지로 구현하는 MCM은 시험성 확보에 심각한 문제점으로 나타나고 있다. 본 논문에서는 고밀도 구조의 MCM 기판에 대한 Interconnetion Line 시험검증을 위한 Flying Prober의 적 용 및 모듈 패키징 공정에 대한 조립성 검증을 위한 BST에 대해 설명한다. 연구에 사용된 MCM 모듈은 MCM-D 공정으로 제작되었으며 31um 신호선폭, 50um Via Hole Dia. 5신호 선층 5절연층 및 455 Net의 기판으로절연층은 Dow chemical의 BCB-4024/4026을 적용하였 다. 조립은 3 ASIC, 24소자 실장 및 2000 Wire Bonding으로 이루어지며 패키지는 방열특성 을 고려한 BGA(491 I /O,50mil pitch)를 개발하여 사용하였다. MCM 기판의미세패턴으로 구성된 Interconnection Line에 대해 Fine Ptich Probing이 가능한 Flying Prober를 사용하 여 평가하였으며 BST를 이용하여 실장소자의 KGD평가 및 능동, 수동소자가 실장된 MCM Package의 조립시험성을 확보할수 있었다.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.4
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• pp.67-73
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• 2015

Recently in the evaluation of physical properties of a material, its surface friction characteristics is much required. This study treats the development of portable and affordable friction coefficient tester, which includes utensil design and application, measurement circuit design and layout, and microprocessor based firmware building. Also, real applicability of the present portable friction coefficient tester has been shown via performance comparisons with the existing standard tester.

• Journal of the Korean earth science society
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• v.38 no.2
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• pp.150-160
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• 2017

In order to determine the porosity of rock, the 'standard test method for porosity and density of rock' proposed by the Korean Society for Rock Mechanics is commonly used. However, the standard test method, which uses a drying oven, takes 8 to 24 hours to complete the test in taking samples out of the oven every four hours and measuring the weight of the specimen. To complement these disadvantages, we devised a method for measuring rock porosity by using a microwave oven. The devised method reduced the cause of errors and the inconvenience occurred in the process of weighing samples by constructing a weight monitoring system, which monitors the drying process. A suitable heating/pause time was set up to maintain the temperature of sample below $105{\pm}3^{\circ}C$ in drying process, and an alarm system was implemented in order to stop drying process when the weight change of the rock sample is within 0.1% of the initial weight. The porosity was determined from the dry weight of the sample, which was obtained by the curve fitting of weight monitoring data. Then, the porosities obtained by using the microwave oven were compared with those obtained by the standard test method. Test results using sandstone samples showed that the porosities obtained by a microwave oven was similar to those obtained by the standard method and the porosity difference between two methods was as large as 0.4%. In addition, repeated porosity measurement using the same specimen showed that the standard deviation of the porosity, which reflects the precision of the measurement was as good as 0.23%. Therefore, a microwave oven porosity measurement system can give the porosity of rock samples with high reliability.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.91-97
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• 2021

A microserver is a type of a computing server, in which two or more CPU nodes are implemented on a separate computing board, and a plurality of computing boards are integrated on a main board. In building a cluster system, the microserver has advantages in several points such as energy efficiency, area occupied, and ease of management compared to the existing method of mounting legacy servers in multiple racks. In addition, since the microserver uses a fast interconnection network between CPU nodes, performance improvement for data transfers is expected. The proposed microserver can mount a total of 16 computing boards with 4 CPU nodes on the main board, and uses Serial-RapidIO (SRIO) as an interconnection network. In order to analyze the performance of the proposed microserver in terms of the interconnection network which is a core performance issue of the microserver, we compare and quantify the performance of commercial microservers. As a result of the test, it showed up to about 7 times higher bandwidth improvement when transmitting data using the interconnection network. In addition, with CloudSuite benchmark programs used in actual cloud computing, maximum 60% reduction in execution time was obtained compared to commercial microservers with similar CPU performance specification.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.415-423
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• 2019

In this paper, a design method for a high-sensitivity microstrip patch sensor antenna (MPSA) loaded with a bent-slot was studied for the permittivity measurement. The bent-slot similar to a single-ring complementary split ring resonator was added along a radiating edge of the patch in order to enhance the sensitivity to the permittivity. The sensitivity of the proposed MPSA was compared with that of a conventional rectangular MPSA and a thin rectangular-slotted MPSA. Three MPSAs were designed and fabricated on a 0.76-mm-thick RF-35 substrate so that the input reflection coefficient would resonate at 2.5 GHz in the absence of the superstrate under test. When five different Taconic substrates with a relative permittivity ranging from 2.17 to 10.2 were used as the superstrate under test, experiment results show that the sensitivity of the proposed MPSA, which is measured by the shift in the resonant frequency of the input reflection coefficient, is 4.1 to 6.1 times higher than that of the conventional MPSA.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.67-77
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• 2017

In the present study, uplift load carrying behavior of micropiles with installation angle and pile spacing was investigated based on uplift load tests using single and group micropiles. In addition, evaluation methods of uplift load carrying capacity of group micropiles were proposed based on FHWA (2005) and Madhav (1987) and they were compared with test results to confirm the validity of proposed methods. From the test results, uplift load carrying capacities of single and group micropiles increased with the increase of the installation angle up to $30^{\circ}$, whose values also increased slightly with increasing pile spacing. For the proposed method based on FHWA (2005), the estimated values were similar to measured values up to $15^{\circ}$ of installation angle and 5D of pile spacing. For the proposed method based on Madhav (1987), on the other hand, it was observed that the estimated values were in good agreement with measured values in all installation conditions.