• 천문학회보
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• 제45권1호
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• pp.67.2-67.2
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• 2020

Not only the magnitude of the mirror surface error, the pattern matters as it produces certain aberrations. In particular, the surface error of the freeform mirrors, which are optimized to eliminate specific aberrations, might show much higher sensitivity in optical performance. Therefore, we analyze the mirror surface error with Zernike polynomials with the goal of generating a realistic error surface. We investigate the surface error of the freeform mirror fabricated by diamond turning machine to analyze the realistic tendency of the error. The surface error with 0.22 ㎛ root-mean-square value is fitted to the Zernike terms using the incremental fitting method, which increases the number of the fitting coefficients through steps. Furthermore, optical performance via surface error pattern based on Zernike terms is studied to see the influences of each term. With this study, realistic error surface generation may allow higher accuracy not only for the feasibility test but also for all tests and predictions using optical simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권2호
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• pp.82-102
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• 2008

Packet losses tend to occur during short error bursts separated by long periods of relatively error-free transmission. There is also a significant spatial correlation in loss among the receiver nodes in a multicast session. To recover packet transmission errors at the transport layer, tree-based protocols construct a logical tree for error recovery before data transmission is started. The current tree construction scheme does not scale well because it overloads the sender node. We propose a scalable recovery tree construction scheme considering these properties. Unlike the existing tree construction schemes, our scheme distributes some tasks normally handled by the sender node to specific nodes acting as repair node distributors. It also allows receiver nodes to adaptively re-select their repair node when they experience unacceptable error recovery delay. Simulation results show that our scheme constructs the logical tree with reduced message and time overhead. Our analysis also indicates that it provides fast error recovery, since it can reduce the number of additional retransmissions from its upstream repair nodes or sender node.

• 대한안전경영과학회지
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• 제17권1호
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• pp.119-124
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• 2015

According as radiation therapy technique develops, standardization of radiation therapy has been complicated by the plan QA(Quality Assurance). However, plan QA tools are two type, OADT (opposite accumulation dose tool) and 3DADT (3 dimensional accumulation dose tool). OADT is not applied to evaluation of beam path. Therefore tolerance error of beam path will establish measurement value at OADT. Plan is six beam path, five irradiation field at each beam path. And beam path error is 0 degree, 0.2 degree, 0.4 degree, 0.6 degree, 0.6 degree, 0.8 degree. Plan QA accomplishes at OADT, 3DADT. The more path error increases, the more plan QA error increases. Tolerance error of OADT path is 0.357 using tolerance error of conventional plan QA. Henceforth plan QA using OADT will include beam path error. In addition, It will increase reliability through precise and various plan technique.

• International Journal of Computer Science & Network Security
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• 제23권9호
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• pp.129-133
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• 2023

Classification or prediction problem is how to solve it using a specific feature to obtain the predicted class. A wheat seeds specifications 4 3 classes of seeds will be used in a prediction process. A multi linear regression will be built, and a prediction error ratio will be calculated. To enhance the prediction ratio an ANN model will be built and trained. The obtained results will be examined to show how to make a prediction tool capable to compute a predicted class number very close to the target class number.

• 한국기계기술학회지
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• 제20권6호
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• pp.872-878
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• 2018

Steam tables including superheated, saturated and compressed region were simultaneously modeled using the neural networks. Pressure and temperature were used as two inputs for superheated and compressed region. On the other hand Pressure and dryness fraction were two inputs for saturated region. The outputs were specific volume, specific enthalpy and specific entropy. The neural network model were compared with the linear interpolation model in terms of the percentage relative errors. The criterion of judgement was selected with the percentage relative error of 1%. In conclusion the neural networks showed better results than the interpolation method for all data of superheated and compressed region and specific volume of saturated region, but similar for specific enthalpy and entropy of saturated region.

• 한국미생물·생명공학회지
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• 제21권4호
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• pp.354-365
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• 1993

A novel control method with automatic tuning of PID controller parameters has been developed for efficient regulation of dissolved oxygen concentration in fed-batch fermentations of Escherichia coli. Agitation speed and oxygen partial pressure in the inlet gas stream were chosen to be the manipulated variables. A heuristic reasoning allowed improved tuning decisions from the supervision of control performance indices and it coule obviate the needs for process assumptions or disturbance patterns. The control input consisted of feedback and feedforword parts. The feedback part was determined by PID control and the feedforward part is determined from the feed rate. The proportional gain was updated on-line by a set of heuristics rules based on the supervision of three performance indices. These indices were output error covariance, the average value of output error, and input covariance, which were calculated on-line using a moving window. The integral and derivative time constants were determined from the period of output response. The specific growth rate was maintained at a low level to avoid acetic acid accumulation and thus to achieve a high cell density. The specific growthe rate was estimated from the carbon dioxide evolution rate. In fed-batch fermentation, the simutaneous control of dissolved oxygen concentration (at 0.2; fraction of saturated value) and specific growth rate (at 0.25$hr^{-1}$) was satisfactory for the entire culture period in spite of the changes in the feed rate and the switching of control input.

• Computers and Concrete
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• 제4권6호
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• pp.425-436
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• 2007

This study is mainly focused on applying Fuller's ideal gradation curve to theoretically design blended ratio of all solid materials of a reactive powder mortar (RPM), also known as reactive powder concrete (RPC), with the aid of error function, and then to study the effect of fly ash/slag on the performance of RPM. The solid particle is assumed to be spherical particles. Then, the void volume of paste ($V_{\nu}$) and the paste content with specific quality can be obtained. As conclusion, under Fuller's ideal grading curve, the amount of fly ash/slag mixture is higher than that with silica fume along due to it better filled the void within solid particle and obtains higher packing density.

• The Journal of Asian Finance, Economics and Business
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• 제8권1호
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• pp.647-654
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• 2021

This study examines the non-performing loans of rural banks and macroeconomic factors in Indonesia, including inflation, exchange rates, and interest rates. Theoretically, the existence of erratic macroeconomic conditions can affect the level of non-performing credit risk in rural credit banks in Indonesia. The effect of macroeconomic conditions on non-performing loans has a different response for each economic sector. The main objective of this study is to determine the effect of macroeconomic factors (inflation, exchange rates, and interest rates) and bank-specific factors (credit) on the Non-Performing Loans (NPL) of Rural Banks in Indonesia for the period from January 2015 to December 2018. This study uses a Vector Error Correction Model (VECM) estimation to determine the effect of independent variables consisting of macroeconomic factors and bank-specific factors. Based on the estimation results of the Vector Error Correction Model, three variables that have a positive and significant effect on long-term non-performing loans are credit, inflation, and interest rates. Meanwhile, in the short term, there are only two variables that have a positive and significant effect on non-performing loans, namely, credit and interest rates. Inflation and exchange rate variables have a negative and insignificant effect on bad credit in the short term.

• 한국과학교육학회지
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• 제39권3호
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• pp.363-377
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• 2019

이 연구는 자기보고식 검사를 통해 과학 관련 정의적 영역을 평가하려할 때 검사 결과에서 나타나는 주관성의 양상을 과학 특이적 측면에서 밝혔다. 과학 관련 개념이나 인식을 측정하려할 때 학생이 지닌 과학 특성, 본성에 대한 인식이 원인이 되어 나타나는 반응을 과학 특이적 반응으로 정의했다. 그 중에서 과학 특이적 반응이 특별히 측정 구인을 방해하거나 정확한 자기 보고를 벗어나게 하는 경우에 대해 탐색했다. 고등학교 1, 2학년 649명의 정의적 특성 및 심리적 특성을 검사한 양적 자료와 학생 44명을 면담한 질적 자료로부터 과학 특이적 요소로 인한 오차 결과를 도출했다. 학생이 일상과 과학 학습 경험으로부터 내면화한 과학에 대한 관점과 과학 특성은 검사 도구를 이루는 문항들과 상호작용한다. 그 결과 과학의 특성, 개인의 과학 경험, 검사 도구 속 과학이라는 세 측면에서 정확한 자기 보고를 방해하는 요소가 발견되었다. 과학 본질적 측면과 관련 있는 과학의 특성은 학생들이 과학을 보는 관점과 주관적으로 인식한 과학의 특성이 측정하려는 구인에 관계없이 문항에 반응하도록 한다. 학습자 측면에서 개인의 과학 경험은 학생이 지닌 과학 동기, 과학 경험과의 상호작용, 과학과 삶에 대한 인식으로 구성된다. 마지막으로 도구적 측면에서 검사 도구 속 과학은 과학 개념의 불명확성으로 인한 용어 혼동으로 연결되며 정확한 자기보고를 방해할 수 있다. 본 연구 결과에 의한 시사점으로 검사 문항에서 과학 특이적 요소의 포함 여부 검토, 측정 개념을 명확히 하기 위한 주의점, 개발 단계에서의 과학 특이성 요소 검토, 일상 과학과 학교 과학의 괴리를 줄이려는 노력 필요 등을 제안했다.

• 한국주조공학회지
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• 제13권4호
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• pp.323-332
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• 1993

An implicit finite difference formulation with three methods of latent heat treatment, such as equivalent specific heat method, temperature recovery method and enthalpy method, was applied to solidification analysis. The Neumann problem was solved to compare the numerical results with the exact solution. The implicit solutions with the equivalent specific heat method and the temperature recovery method were comparatively consistent with the Neumann exact solution for smaller time steps, but its error increased with increasing time step, especially in predicting the solidification beginning time. Although the computing time to solve energy equation using temperature recovery method was shorter than using enthalpy method, the method of releasing latent heat is not realistic and causes error. The implicit formulation of phase change problem requires enthalpy method to treat the release of latent heat reasonably. We have modified the enthalpy formulation in such a way that the enthalpy gradient term is not needed, and as a result of this modification, the computation stability and the computing time were improved.