재(再) 제조란 폐기된 제품을 회수하여 신제품과 같은 품질상태로 회복시키는 과정으로, 제품의 폐기로 인하여 발생하는 경제적 손실뿐만 아니라 폐기물의 증가로 인한 환경오염의 예방에도 도움을 준다. 이러한 재 제조의 목표는 보다 많은 부품들을 재사용하는 것으로 기존의 수리와 제조 개념이 결합된 형태로서 제품의 완전 해체, 세척, 검사, 부품수리 및 조정과 교체, 제품의 재조립 등의 일련의 단계를 거치게 되며 이 과정에서 부품의 신뢰도는 매우 중요한 요소로 작용하게 된다. 따라서 이 논문에서는 크게 다음의 두 가지 내용에 대해서 다루게 된다. 첫째, 시스템의 가용도를 모델링하는 방법으로 잘 알려진 마코프 모델을 이용하여 재 제조 시스템의 가용도 분석을 위한 모델을 제시한다. 둘째, 가용도 분석을 통한 부품의 재사용 빈도와 이용시간 평가 등을 통하여 재 제조 시스템의 성능을 평가하기 위한 척도를 제시한다.

Dual frequency acoustic pinger(AP) was manufactured to reduce study effect by long-term use of developed single frequency AP to prevent cetacean bycatch. Directivity characteristic of transducer was the omnidirectional pattern which showed less than ±3dB the change range of sensitivity on the beam pattern of right and left. Source power level(SPL) was 1384311pa with epoxy window before casing however after casing 1170B11Pa at sea. Dual frequency Af was tested to identify the avoidance behavior of bottlenose dolphin by its working. However the efficiency of dual frequency AP about the study effect was verified experiment repeatedly using single and dual frequency AP.

본 실험은 고랭지 산지초지에서 예취횟수와 시비수준이 목초의 식생변화와 건물수량 및 사료성분에 미치는 영향을 검토하기 위하여 3년간 실시하였다. 실험은 표고 600m에서 예취횟수를 2회와 3회, 시비수준을 ha당 질소-인산-칼리 200-200-200kg의 소비구 및 280-200-240kg/ha의 표준시비구로 나누어 실시하였다. 화본과목초의 비율은 2회 예취가 3회 예취보다 높았으며, 클로버 비율은 3회 예취한 소비구에서 로 가장 높았다. 잡초는 모든 처

비선형 함수로 모델링되는 동적 시스템의 비선형 파라미터를 결정하기 위하여 주파수 영역 볼테라 모델을 적용하는 연구를 수행하였다. 시간영역의 1차, 2차, 3차 전달함수에 해당하는 주파수 영역의 볼테라 핵함수를 비선형 파라미터 산정 과정에 3차 비선형 항까지 포함시켰다. Schetzen의 방법으로 시스템의 비선형 미분방정식에 적합한 볼테라 급수 표현식을 정하고, 이로부터 유도되는 비선형 전달함수를 입력 출력 관계식에 사용하였다. 관찰된 입력을 비선형 주파수 영역 모델에 대입하여 계산한 출력과 관찰된 출력의 차이로 오차를 정의한 후 오차를 최소화 시키는 시스템 파라미터의 값을 구하였다. 예제를 통하여 선형 주파수 구간 뿐만 아니라 2차 혹은 3차 비선형이 지배적인 주파수 범위 대에서 볼테라 모델이 충분한 정확성과 수렴성을 가지며 인식된 파라미터는 실제 값과 잘 일치함을 확인할 수 있었다.

The present study investigated the hypothesis that a extremely low frequency magnetic field (ELF-MF) partially suppresses the synthesis of human growth hormone (HGH) in a group of 28 primary schoolchildren living nearby and 60 primary schoolchildren aged 12 years living far away from overhead transmission power lines from December 2003 to April 2004 in Seoul, Korea. The mean personal exposure levels of the primary schoolchildren living nearby overhead transmission power line were 0.37 μT, whereas the levels for the primary schoolchildren living away from overhead transmission power line was 0.05 μT. From simple analyses, the mean growth hormone levels in the primary schoolchildren living nearby were lower than away from overhead transmission power line, and statistically significant differences in the levels of the growth hormone (p = 0.0316), whereas not statistically significant differences in the levels of the growth hormone related to the distance from residence to power line less and more than 100 m by cut-off point (p = 0.4017). In conclusion, these results may indicate that urinary levels of nocturnal growth hormone are altered in primary schoolchildren exposed to extremely low frequency magnetic field at overhead transmission power line.

Electromagnetic fields of all frequencies represent one of the most common and fastest growing environmental influences, about which anxiety and speculation are spreading. All populations are now exposed to varying degrees of electromagnetic field, and the levels will continue to increase as technology advances. The objectives of this study were to measure and analyze emitting characteristics of extremely low frequency electromagnetic field at micro-environments. We measured magnetic field at microenvironments such as home, school, educational institute, internet pc game room for children attending the primary school. The range of time weighted average (TWA) of 60 Hz EMF in micro-environment were 0.26∼ 7.62 mG and the highest TWA 7.62 mG was measured in PC room possessed more than 50 computers. We will measure personal exposure levels of primary students and analyze correlation between major micro-environments and personal exposure level.

The frequency distribution of HII regions radii in our galaxy has been investigated. The correlation between the number of these regions and their radii has been re-determined, and could be represented by an exponential function. The size distribution of the HII regions in 10 spiral galaxies has been derived and combined with that of our galaxy to derive the distances of these galaxies. It has been found that the distances derived are in a good agreement with the published ones. The interstellar extinction in the galaxies has no influence on the distance estimate when using this geometrical method.

Fuzzy information representation of multi-source spatial data is applied to landslide hazard mapping. Information representation based on frequency ratio and non-parametric density estimation is used to construct fuzzy membership functions. Of particular interest is the representation of continuous data for preventing loss of information. The non-parametric density estimation method applied here is a Parzen window estimation that can directly use continuous data without any categorization procedure. The effect of the new continuous data representation method on the final integrated result is evaluated by a validation procedure. To illustrate the proposed scheme, a case study from Jangheung, Korea for landslide hazard mapping is presented. Analysis of the results indicates that the proposed methodology considerably improves prediction capabilities, as compared with the case in traditional continuous data representation.

Dense -20vol.%SiC composite was synthesized by high-frequency induction-heated combustion synthesis(HFIHCS) method within 2 minutes in one step from elemental powder mixture of W, Si and C. Simultaneous combustion synthesis and densification were accomplished under the combined effects of an induced current and mechanical pressure. Highly dense -20vol.%SiC with relative density of up to 97% was produced under simultaneous application of 60MPa pressure and the induced current. The average grain size of was about 5.2. The hardness and fracture toughness values obtained were 1700kg/ and , respectively.

In this paper, we describe a principle of the atomic frequency standard and clock system in VLBI(Very Long Baseline Interferometry). The hydrogen maser is a usual VLBI standard. During VLBI observations, signals emitted by distant sources of radio frequency energy(quasars) are received and recorded at several antennas. At each antenna(VLBI station), a very stable frequency standard(hydrogen maser) provides a reference signal which enables time-tagging to the quasar signals as they are being recorded on magnetic tapes or hard-disk modules. For each VLBl experiment, correlation of the time-tagged recorded information between the participating antennas is used to yield the arrival time differences of any specific quasar radio wave between the antennas. These time differences are used to calculate the relative antennas to each other. In this paper, we also introduce the KVN(Korean VLBI Network) atomic frequency standard and clock system.

This study was conducted to identify the factors that correlated with food consumption frequency and perceptions of attributes for food selection. The purpose of this study was to improve menu's quality which is related to the food consumption frequency. Taste health and cost perceptions were chosen as the main factors of foods selection from the former related researches. There were differences in foods perception and consumption patterns according to gender. For both of female and male consumers, taste perceptions were highly correlated with consumption of most of foods. Finally, some recommendations which should be considered to correct or improve the quality of menu.

본 연구에서는 기 개발된 유한요소-경계요소 조합을 통한 지반구조물 상호작용해석기법을 이용하여 주파수 특성이 다른 여러 가지 지진파를 이용한 수치해석을 통하여 지진파에 따른 거동특성을 분석하였다. 사용한 기본해의 검증을 위하여 적용된 다층 반무한 해를 Estorff 등의 연구결과와 비교하였으며, 기본해를 이용하여 개발된 지반-구조물 상호작용해석기법의 검증을 위하여 자유장해석을 수행하였다. 자유장 해석결과는 1차원 파전달 이론에 의하여 개발된 자유장응답해석 프로그램인 SHAKE의 결과와 비교하여 그 타당성을 검증하였다. 검증된 해석기법을 이용하여 특성이 다른 3종류의 지진파가 적용된 2차원 평면상의 지반-구조물 상호작용해석을 수행함으로써 지진파와 말뚝유무에 따른 지반-구조물 상호작용거동특성을 분석하였다. 해석결과 지진이 작용할 때는 말뚝기초를 사용하는 것이 반드시 유리한 결과를 주지는 않는다는 것을 알았으며, 지반의 비선형성을 고려 할때는 말뚝의 유무가 지진응답결과에 큰 영향을 미치지 않는다는 것을 알 수 있었다.