• Journal of Electrical Engineering and Technology
• /
• 제12권6호
• /
• pp.2118-2126
• /
• 2017

The large-scale power system blackouts have indicated that conventional protection relays that based on local signals cannot fit for modern power grids with complicated setting or heavily loaded-flow transfer. In order to accurately detect various faulted lines and improve the fault-tolerance of wide-area protection, a novel multi-section weighed fault matching and detecting algorithm is proposed. The real protection vector (RPV) and expected section protection vectors (ESPVs) for five fault sections are constructed respectively. The function of multi-section weighed fault matching is established to calculate the section fault matching degrees between RPV and five ESPVs. Then the fault degree of protected line based on five section fault degrees can be obtained. Two fault detecting criterions are given to support the higher accuracy rate of detecting fault. With the enumerating method, the simulation tests illustrate the correctness and fault-tolerance of proposed algorithm. It can reach the target of 100% accuracy rate under 5 bits error of wide-area protections. The influence factors of fault-tolerance are analyzed, which include the choosing of wide-area protections, as well as the topological structures of power grid and fault threshold.

• Current Optics and Photonics
• /
• 제1권5호
• /
• pp.538-543
• /
• 2017

Progressive addition lenses (PAL) have very wide application in the modern glasses market. The unique progressive surface can make a lens have progressive refractive power, which can meet the human eye's different needs for distance-vision and near-vision. According to the national glasses fabrication standard, the difference between actual optical power after fabrication and nominal design value should be less than 0.1D over the lens effective area. The optical power distribution of PAL is determined directly by the surface. Consequently, the surface processing accuracy requirement is proposed. Beginning from the surface expressions of progressive addition lenses, the relationship equations between the surface sag and optical power distribution are derived. They are demonstrated through tolerance analysis and test of an example progressive addition lens with addition of 2.09D (5.46D-7.55D). The example addition surface is fabricated under given accuracy by a single-point diamond ultra-precision machine. The optical power of the PAL example is tested with a focal-meter after fabrication. The optical power addition difference between test result and design nominal value is 0.09D, which is less than 0.1D. The derived relationship between the surface error and optical power is verified from the PAL example simulation and test result. It can provide theoretical tolerance analysis proof for the PAL surface fabricating process.

• 한국CDE학회논문집
• /
• 제14권1호
• /
• pp.18-24
• /
• 2009

This paper proposes an analytical method of evaluating the maximum error by modeling the exact tool path for the tool traverse singular region in five-axis machining. It is known that the NC data from the inverse kinematics transformation of 5-axis machining can generate singular positions where incoherent movements of the rotary axes can appear. These lead to unexpected errors and abrupt operations, resulting in scoring on the machined surface. To resolve this problem, previous methods have calculated several tool positions during a singular operation, using inverse kinematics equations to predict tool trajectory and approximate the maximum error. This type of numerical approach, configuring the tool trajectory, requires much computation time to obtain a sufficient number of tool positions in a region. We have derived an analytical equation for the tool trajectory in a singular area by modeling the tool operation into a linear and a nonlinear part that is a general form of the tool trajectory in the singular area and that is suitable for all types of five-axis machine tools. In addition, we have evaluated the maximum tool-path error exactly, using our analytical model. Our algorithm can be used to modify NC data, making the operation smoother and bringing any errors to within tolerance.

• Journal of the Optical Society of Korea
• /
• 제18권6호
• /
• pp.720-731
• /
• 2014

There are many kinds of optical systems to widen a field of view. Fisheye lenses with view angles of 180 degrees and omni-directional systems with the view angles of 360 degrees are recognized as proper systems to widen a field of view. In this study, we proposed a new optical system to overcome drawbacks of conventional omni-directional systems such as a limited field of view in the central area and difficulties in manufacturing. Thus we can eliminate the undesirable reflection components of the omni-directional system and solve the primary drawback of the conventional system. Finally, tolerance analysis using Zernike polynomial coefficients was performed to confirm the productivity of the new optical system. Furthermore, we established a method of optical axis alignment and compensation schemes for the proposed optical system as a result of tolerance analysis. In a sensitivity calculation, we investigated performance degradation due to manufacturing error using Code V(R) macro function. Consequently, we suggested compensation schemes using a lens group decentering. This paper gives a good guidance for the optical design and tolerance analysis including the compensation method in the extremely wide angle system.

• 지적과 국토정보
• /
• 제52권1호
• /
• pp.5-16
• /
• 2022

다각형 필지의 면적오차계산에 대한 일반식으로부터 직사각형 필지의 면적오차계산식을 도출하고 관련 법률 시행령에서 정하고 있는 면적오차계산의 상수항 0.026² × M(축척분모)이 갖는 의미를 분석하였다. 그 결과, 현행의 면적오차 공식은 직사각형 필지모형으로서 도해측량의 특성을 적절히 반영하고 있으나, 정량적으로는 면적오차를 비교적 크게 허용한다는 것을 알 수 있었다. 또, 면적이 같더라도 필지의 형상에 따라 정사각형 필지보다 50% 더 많은 면적오차가 산출될 수 있다는 문제, 필지 분할시 허용면적오차가 달라져야 하는 문제 등을 파악하였다. 이와 더불어, 본 연구에서 도출한 면적오차계산식으로써 지적측량의 관점에서 문제를 한꺼번에 해결할 수 있는 방안을 제시하였다. 즉, 필지의 크기와 형상을 반영하는 문제, 측량의 정확도를 반영하는 문제, 도해측량과 수치측량을 구분할 필요 없이 단일의 면적오차계산식을 채택하는 문제에 대한 해결책이다. 이들 문제를 해소하는 새로운 면적오차계산식의 채용은 많은 관련 요소들의 개선을 촉진하여 선진적 지적제도로의 발전을 강화할 것이다.

• 대한공간정보학회지
• /
• 제14권3호
• /
• pp.23-30
• /
• 2006

임야지역은 지역적 특성상 토탈스테이션, RTK-GPS 측량 등의 지상측량 방법으로는 지적재조사 측량에 한계성이 있다. 그렇기 때문에 기존 지적재조사 측량 방법들로 제안되고 있는 방식과는 다른 새로운 방법들이 모색되어야 할 필요성이 있다. 본 연구에서는 임야지역을 효율적으로 재조사할 수 있는 방법으로서 현재 KLIS에서 이용되고 있는 임야도 전산파일의 이용가능성을 제시하고자 하였다. 연구결과 가장 중요한 면적오차는 대체적으로 오차범위 이내의 성과를 보였다. 따라서 위치경계선 조정을 위한 현황 참조 데이터와 KLIS 데이터를 연계하여 이용한다면 향후 지적재조사시에 충분한 활용가능성이 있는 것으로 나타났다.

• Nuclear Engineering and Technology
• /
• 제56권8호
• /
• pp.2916-2922
• /
• 2024

\\In memory semiconductors such as a static random access memory (SRAM), a common problem is soft errors under radiation environment. These soft errors cause bit flips, which are referred to as single event upsets (SEUs). Some radiation-hardened SRAM cells such as a Quatro SRAM, we-Quatro SRAM, and DICE SRAM cells have been reported for years. However, these designs have the disadvantage of taking up more area than a conventional 6T SRAM cell. Thus, we propose a radiation-hardened SRAM cell design that we named capacitor-static random access memory (C-SRAM) without area overhead. The C-SRAM is formed by simply adding a capacitor to the conventional 6T SRAM. It was designed to mitigate the radiation effect using the conservation law of electrical charge. Moreover, it has the same cell size as the conventional 6T SRAM cell. Its static noise margins (SNMs), which are indicators of operational stability, are equal to the conventional 6T SRAM values of 530 mV, 220 mV, and 860 mV in hold, read, and write modes, respectively. The results of the SEU simulation test showed that it had 4.761 times better flipping tolerance than the conventional 6T SRAM with a charge value of 247.494 fC. In addition, irradiation experiments also confirmed that the C-SRAM cell was more tolerant than the 6T SRAM cell. The conventional 6T SRAM and C-SRAM were fabricated using a standard 0.18 ㎛ CMOS process.

• 디지털산업정보학회논문지
• /
• 제5권4호
• /
• pp.39-49
• /
• 2009

Nowadays, according to rapid development of computing environments, information processing and analysis system are very interesting research area. As a viewpoint of data preparation-processing-analysis in knowledge technology, the goal of automated information system is to satisfy high reliability and confidence and to minimize of human-administrator intervention. In addition, we expect the system which can deal with problem and abnormal error effectively as a fault detection and fault tolerance. In this paper, we design a monitoring system as follows. A productive monitoring information from various systems has unstructured forms and characteristics and crawls informative data by conditions and gathering rules. For representing of monitering information which requested by administrator, running-status can be able to check dynamically and systematic like connection/closed status in real-time. Our proposed system can easily correct and processing for monitoring information from various type of server and support to make objective judgement and analysis of administrator under operative target of information system. We implement semi-realtime monitering system using AJAX technology for dynamic browsing of web information and information processing using XML and XPATH. We apply our system to SMS server for checking running status and the system shows that has high utility and reliability.

• 한국컴퓨터정보학회논문지
• /
• 제10권2호
• /
• pp.199-204
• /
• 2005

인터넷 사용이 급속히 확산되면서 많은 기업들이 전자상거래를 적극적으로 도입하고 있으며 시장규모도 급속도로 증가하고 있다. 그러나 전자상거래에 대한 연구성과는 그 중요성과 사회적 관심에 비해 매우 미약한 실정이다. 특히 고객 요구사항은 온라인 구매의향에 많은 영향을 미칠 수 있으므로 이에 대한 정확한 이해가 선행되어야만 할 것이다. 본 연구는 전자상거래에서 중요시되는 구매의향에 대한 성공요인을 분석함으로써 인터넷 쇼핑몰의 설계 운영, 전략수립 등에 시사점을 제공하기 위함이다. 연구결과 가격 및 사용자편리, 쇼핑몰 배송 등에 대한 신뢰, 속도 및 오류방지가 쇼핑물 구매의향에 유의한 영향을 미치는 것으로 판명되었다.

• Journal of Mechanical Science and Technology
• /
• 제19권spc1호
• /
• pp.265-271
• /
• 2005

Randomness exists in engineering. Tolerance, assemble-error, environment temperature and wear make the parameters of a mechanical system uncertain. So the behavior or response of the mechanical system is uncertain. In this paper, the uncertain parameters are treated as random variables. So if the probability distribution of a random parameter is known, the simulation of mechanical multibody dynamics can be made by Monte-Carlo method. Thus multibody dynamics simulation results can be obtained in statistics. A new concept called functional reliability is put forward in this paper, which can be defined as the probability of the dynamic parameters(such as position, orientation, velocity, acceleration etc.) of the key parts of a mechanical multibody system belong to their tolerance values. A flexible mechanical arm with random parameters is studied in this paper. The length, width, thickness and density of the flexible arm are treated as random variables and Gaussian distribution is used with given mean and variance. Computer code is developed based on the dynamic model and Monte-Carlo method to simulate the dynamic behavior of the flexible arm. At the same time the end effector's locating reliability is calculated with circular tolerance area. The theory and method presented in this paper are applicable on the dynamics modeling of general multibody systems.