• Journal of the Korean Institute of Navigation
• /
• v.25 no.2
• /
• pp.131-136
• /
• 2001

A new analysis method of lumped-element directional coupler for CATV was proposed, where the even-and odd-mode theory for a symmetrical coupled-line directional coupler was applied to a transformer-type directional coupler. In addition, the tap-offs were analyzed by the proposed theory, which are widely used in CATV (Cable Television) systems. By comparing the calculated results for S-parameters results to the measured ones using only the even-and odd-mode reflection coefficients, the validity of the proposed analysis method was confirmed. Then, it was clearly shown that the tap-off has very wide bandwidth from 5 MHz to 4,000 MHz by adopting the proposed theory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2007.06a
• /
• pp.95-98
• /
• 2007

In this paper, we make an analysis of electromagnetic wave absorption properties of $TiO_2$ in W-band. Therefore, we fabricated some samples in different composition ratio of $TiO_2$ and CPE. And the material properties of samples are calculated from S-parameter of samples using $\ell-2\ell$ method. We analyze absorption properties and complex relative permittivitis of samples. As a result, it has verified that absorption properties of sample containing $TiO_2:CPE=70:30wt.%$ have been excelled in W-band.

• Geotechnical Engineering
• /
• v.1 no.1
• /
• pp.47-58
• /
• 1985

A new approach is develped to analyze the reliability of the shallow foundation. The measure of the safety of the structhure is expressed In terms of the probability of failure, instead of the conventional factor of safety. Many uncertainties involved in the deterministic stability anaitsis can be reasouably treated by using the probabilistic approach. Both the soil properties and loads are assumed to be random variables. Accordingly, the capacity and demand are considered to be normal, log-normal, and beta variated. Use is made of Error Propagation Method to investigate the probability of failure. And the relationship is investigated between the probability of failure and the central factor of safety. The results are computer programed and several case studies are performed using developed program.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.6 no.1
• /
• pp.90-96
• /
• 2011

In this paper, we propose a new discrete logarithm problem(DLP) based on the class semigroups of imaginary quadratic non-maximal orders using the special character of non-invertible ideal and analysis its security. To do this, we first explain the mathematical background explicitly and prove some properties of Cls (O) which relate to constructing the DLP and guaranteeing the security. To test the security of the proposed DLP, we compare the class number of the maximal order with that of the non-maximal order and investigate the unique factorization problems of ideals between class groups of the maximal orders and class semigroups of non-maximal orders to ensure the security of the cryptosystem.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.11 s.176
• /
• pp.99-103
• /
• 2005

It is generally accepted that fracture toughness of fiber-reinforced polymer composites is affected by strain rate in an atmospheric pressure condition. For a present study, the strain rate effect on the fracture toughness of fiber-reinforced laminated composites in the hydrostatic pressure condition was investigated. For this purpose, fracture tests have been conducted using graphite/epoxy laminated composites applying three steps of the strain rate at 270 MPa hydrostatic pressure condition. The strain rates applied were $0.05\%/sec,\;0.25\%/sec$, and $0.55\%/sec$. Fracture toughness was determined from the work factor approach as a function of applied strain rate. The result showed that fracture toughness decreased as the strain rate increased. Specifically, the fracture toughness decreased $12\%$ as the strain rate increased from $0.05\%/sec$ to $0.55\%/sec$.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.4 no.1
• /
• pp.10-19
• /
• 1993

As a method to measure the absorbing characteristics of microwave absorber, the various microwave measuring method can be used fundamentally. There is, however, a big problem in measuring errors, since the wavelength of microwave such as used for radar is very short. Therefore, this research aimed to design and fabricate a converting adaptor of 20mm .PHI. coaxial tube from a Type - N connector to $20mm\phi$ coaxial tube and to use it for evaluating absorption characteristics of microwave absorber. Furthermore, the measurements of absorbing characteristics and material constants have been performed and reviewed, which were carried out by using the coaxial tube and by using rectangular waveguide, res- pectively. As a result, the validity of the proposed measuring method has been confirmed.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1580-1581
• /
• 2008

We investigated the effects of intermittent hydrostatic pressure with various duration of resting period on changes in calcium ($Ca^{2+}$) concentration and adhesive forces of cells on substrates. The quantitive adhesive forces of cells were measured under various resting periods. When the pressure applied to the cells, the concentration of $Ca^{2+}$ increased. Under intermittent hydrostatic pressure, the concentration of $Ca^{2+}$ was maintained under a resting period of 15 min, while it was not decreased with other resting periods of less than 15 min. With a resting period of 15 min, the magnitudes of adhesive forces were significantly increase. In addition, the adhesive forces were measured with and without $Ca^{2+}$ chelating agents to evaluate the effect of $Ca^{2+}$ on cell adhesiveness. When $Ca^{2+}$ ions were chelated, the adhesive forces dramatically decreased, even under intermittent hydrostatic pressure. We conclude that $Ca^{2+}$ plays an crucial role in modulating the adhesive forces of cells, and that the concentration of $Ca^{2+}$ can be increased by intermittent hydrostatic stimuli.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.04a
• /
• pp.279-282
• /
• 2003

충적층 지하수 개발이 활발히 이루어짐에 따라 철, 망간이 충적층 지하수를 이용한 취수원 확보 시에 정수처리의 주요관심대상이 되고 있다. 이에 본 연구에서는 기존 충적층 지하수의 개발이 이루어졌거나 검토되었던 지역을 중심으로 철, 망간의 분포특성을 고찰하여 보았다. 연구지역은 크게 금강권역, 낙동강권역, 영산-섬진강권역, 한강권역으로 나누었고, 조사 관정이 밀집된 권역들은 더 세분된 지구로 나누어 연구를 수행하였다. 철의 경우, 563개의 시료가 망간의 경우, 483개 시료가 수집 분석되었다. 수집된 충적층 지하수 시료들의 철, 망간 농도를 살펴보면, 철의 경우는 전체 조사 관정의 약 27%, 망간의 경우는 약 39%가 음용수 수질기준(WHO)을 상회하였다. 본 연구에서는 철, 망간의 분포특성을 고찰하기 위하여 철, 망간 농도에 대한 다양한 통계 분석을 수행하였다 수집 분석된 철의 산술평균 농도는 2.7ppm이며, 망간의 산술평균 농도는 0.4ppm로 이들 산술평균 역시, 모두 음용수 수질 기준을 상회하는 것으로 나타났다 그러나 철 및 만간 농도의 중간 값은 각 각 50 및 20 ppb이며, 실제 이들 농도가 기하학적 분포를 한다고 가정할 경우, 이들의 대표 값인 기하평균은 모두 먹는 물 수질기준을 만족하는 것으로 나타났다.

• School Mathematics
• /
• v.10 no.3
• /
• pp.339-355
• /
• 2008

This article tried to review the meaning and implication of six stages theory of learning mathematics suggested by Zoltan Dienes in "Building up Mathematics" in 1971. It was not much concretely known to Korean mathematics education society. In particular, there is no mathematical example which could cover all the stages to know what the theory tells. So this article focused on the example which Dienes developed for learning integers in 2000 to dig the theory. As a result, some critical aspects and problems of six stages theory were found. And finally educational implication was described.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.46 no.2
• /
• pp.1-9
• /
• 2009

This paper develops a fast method performing intra prediction which only restores block boundary pixels without decoding all blocks in an I slice of H.264/AVC. To accomplish this, we develop a fast integer inverse DCT scheme that quickly decodes residual block boundary which can be consisted of references pixels. we add the restored block boundary pixels and appropriate calculated prediction pixels for each intra prediction mode and consist of needed reference pixels. The experiments showed that the proposed method produces the reliable performance with reducing the computational complexity, compared to conventional method when applied to H.264/AVC integer DCT.