• Radiation Oncology Journal
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• v.38 no.2
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• pp.138-147
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• 2020

Purpose: To evaluate the dosimetric variations in patients of head and neck cancer treated with definitive or adjuvant radiotherapy using optimized non-coplanar (ncVMAT) beams with coplanar (cVMAT) beams using volumetric arc therapy. Materials and Methods: Twenty-two patients of head and neck cancer that had received radiotherapy using VMAT in our department were retrospectively analyzed. Each of the patients was planned using coplanar and non-coplanar orientations using an optimized couch angle and fluences. We analyzed the Conformity Index (C_IRTOG), Dose Homogeneity Index (DHI), Heterogeneity Index (HI_RTOG), low dose volume, target and organs-at-risk coverage in both the plans without changing planning optimization parameters. Results: The prescription dose ranged from 60 Gy to 70 Gy. Using ncVMAT, C_IRTOG, DHI and HI_RTOG, and tumor coverage (ID_95%) had improved, low dose spillage volume in the body V_5Gy was increased and V_10Gy was reduced. Integral dose and intensity-modulated radiation therapy factor had increased in ncVMAT. In the case of non-coplanar beam arrangements, maximum dose (D_max) of right and left humeral head were reduced significantly whereas apex of the right and left lung mean dose were increased. Conclusion: The use of ncVMAT produced better target coverage and sparing of the shoulder and soft tissue of the neck as well as the critical organ compared with the cVMAT in patients of head and neck malignancy.

• Tunnel and Underground Space
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• v.22 no.4
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• pp.257-265
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• 2012

In this study, a series of CFD (Computational Fluid Dynamics) simulations carried out to evaluate the optimum design model of the internal flow path of drill bit. The Star-CCM+ code was adopted to simulate the multi-phase discharge flow of rock particles and flushing air during a drilling process. The input parameters for the flow simulation of rock particles and air were obtained from the in-situ drilling test results. After the three design factors were determined, the experimental design method (Taguchi method) was utilized to evaluate the optimum value of each factor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.6
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• pp.509-523
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• 2012

The sound quality based on design optimization, throughout the development process of various electronic office equipments, needs to be considered in order to respond the increased needs for the emotional satisfaction of customers in terms of psycho-acoustics. This paper focuses on how to describe the characteristics of operating sound radiated from laser printers by using various sound attributes, and to model the sound quality index that can properly evaluate the subjective preference on modification conditions in the improvement study quantitatively. Especially, the proposed verification process, in the form of combining the correlation based method and the decision error based method, was applied to improve the generality and reliability of a group of participants in the jury evaluation. The modified Aures tonality model was also proposed to improve the correlation coefficient with the mean response of participants by optimizing some parameters. As a result, the loudness, articulation index, roughness, tonality, fluctuation strength were used to model the sound quality index for laser printers by using the multiple-linear regression method. Through the improvement study, it was confirmed that replacing the absorbing materials is effective to reduce the tonalness radiated from the side of a reference printer model. Based on above results, it can be concluded that the proposed model has enough usefulness as quantitative evaluation index to evaluate the difference between modification conditions in the improvement study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4121-4128
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• 2010

A probe card is used in testing semiconductor wafers. It must maintain a precise location tolerance for a fine pitch due to highly densified chips. However, high heat transferred from its lower chuck causes thermal deformations of the probe card. Vertical deformation due to the heat will bring contact problems to the pins in the probe card, while horizontal deformation will cause positional inaccuracies. Therefore, probe cards must be designed with proper materials and structures so that the thermal deformations are within allowable tolerances. In this paper, heat transfer analyses under realistic loading conditions are simulated using ANSYS$^{TM}$ finite element analysis program. Thermal deformations are calculated based on steady-state temperature gradients, and an optimal structure of the probe card is proposed by adjusting a set of relevant design parameters so that the deformations are minimized.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2369-2378
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• 2009

In this paper, we implement measurement functionality for performance measurement of the GSM (Global System for Mobile Communication) terminal by using software. Generally speaking, the receiving algorithms in normal modems cannot be used directly to the measurement system due to the lack of the algorithm accuracy. In this paper, we propose the new receiver algorithm for precise GSM signal measurements. In the receiving algorithm, 2-stage (coarse stage, fine stage) parameters estimation (symbol-timing, frequency offset, carrier phase) scheme is used. To improve the estimation accuracy, we increase the number of the received signal samples by interpolation. The proposed GSM signal measurement algorithm can be used for verifying the hardware measurement system. In addition, the proposed algorithm can be used for the commercial system through code execution speed optimization.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.1
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• pp.22-28
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• 2017

The Convolutional Neural Network(CNN) can be divided into two stages: feature extraction and classification. The hyperparameters such as kernel size, number of channels, and stride in the feature extraction step affect the overall performance of CNN as well as determining the structure of CNN. In this paper, we propose a method to optimize the hyperparameter in CNN feature extraction stage using Parameter-Setting-Free Harmony Search (PSF-HS) algorithm. After setting the overall structure of CNN, hyperparameter was set as a variable and the hyperparameter was optimized by applying PSF-HS algorithm. The simulation was conducted using MATLAB, and CNN learned and tested using mnist data. We update the parameters for a total of 500 times, and it is confirmed that the structure with the highest accuracy among the CNN structures obtained by the proposed method classifies the mnist data with an accuracy of 99.28%.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2336-2347
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• 2018

The azeotrope of methyl acetate methanol and water was isolated using extractive distillation with water as entrainer. The pressure-swing extractive distillation (PSED) process and vapor side-stream distillation column (VSDC) with the rectifier process were designed to separate the methyl acetate, methanol and water mixture. It was revealed that the VSDC with the rectifier process had a reduction in energy consumption than the PSED process. Four control schemes of the two process were investigated: Double temperature control scheme (CS1), $Q_R/F$ feedforward control of reboiler duty scheme for PESD (CS2), $Q_R/F$ feedback control scheme for VSDC (CS3), the feedback control scheme of sensitive plate temperature of side-drawing distillation column to dominate the compressor shaft speed (CS4). Feed flow and composition disturbance were used to evaluate the dynamic performance. As a result, CS4 is a preferable choice for separation of methyl acetate-methanol-water mixture. A control scheme combining the operating parameters of dynamic equipment with the control indicators of static equipment was proposed in this paper. It means using the sensitive plate temperature of side-drawing column to control the compressor shaft speed. This is a new control scheme for extractive distillation.

• Korean Journal of Remote Sensing
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• v.15 no.3
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• pp.195-208
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• 1999

In the classification of satellite images, the representative of training of classes is very important factor that affects the classification accuracy. Hence, in order to improve the classification accuracy, it is required to optimize pre-classification stage which determines classification parameters rather than to develop classifiers alone. In this study, the normality of training are calculated at the preclassification stage using SPOT XS and LANDSAT TM. A correlation coefficient of multivariate Q-Q plot with 5% significance level and a variance of initial training are considered as an object function of genetic algorithm in the training normalization process. As a result of normalization of training using the genetic algorithm, it was proved that, for the study area, the mean and variance of each class shifted to the population, and the result showed the possibility of prediction of the distribution of each class.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.208-208
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• 2018

본 연구에서는 비슬산 강우레이더 관측반경 내 표준유역별 정규화오차 정확도를 이용하여 강우량, 유역특성 등 강우레이더 관측의 수문학적 평가요소와의 상관 특성을 분석하였다. 이를 분석하면 강우레이더 관측 오차 또는 정확도가 수문학적 특성에 따라 얼마나, 어떻게 발생하는지를 추정할 수 있고, 이를 이용하여 홍수예보에 활용되는 입력 자료의 오차를 유역단위로 명확히 정량화 할 수 있어 보다 정확하고 신뢰도 높은 홍수예보에 도움이 될 것으로 기대된다. 강수량 크기와 강수추정 정확도 간의 상관 특성을 분석하기 위해 표준유역 평균 최대 강수량과 강수추정 정확도 간의 분포특성을 분석하였다. 단기간의 자료를 분석하여 오차특성을 정규화 하기는 매우 어렵기 때문에 본 연구에서는 비슬산 강우레이더로 관측된 2012년에서 2016년(5년)사이의 236개 강우사상에 대하여, 동기간의 기상청 AWS 지점 강우량을 기준으로 비슬산 강우레이더의 정규화오차 정확도(1-NE)를 산정한 후 이를 이용하여 850개 표준유역 별 유역평균 정규화오차 정확도를 재산정 하였다. 분석결과 표준유역 평균 최대강수량과 정규화오차 정확도 간에는 유의한 상관성이 있는 것으로 나타났다. 표준유역 평균 최대강수량의 크기에 따라 정규화오차 정확도가 상대적으로 일정한 경향이 나타났고 후처리 단계에서의 편파변수 최적화 이후에는 레이더 강수추정의 정규화오차 정확도가 표준유역 평균 최대강수량 크기에 상관없이 일정해 지는 것으로 나타났다. 따라서 이러한 일정한 레이더 강수추정의 정규화오차 정확도는, 편파변수 최적화에 의해 관측 가능한 최대 기대 정확도 수준 도달에 도달했다고 볼 수 있으며, 표준유역에서 강우레이더의 강수추정 기대 정확도 수준은 84%(정규화오차 16%에 해당) 정도로 추정되었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.191-191
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• 2017

Floods have become more widespread and frequent among natural disasters and consisted significant losses of lives and properties worldwide. Flood's impacts are threatening socio-economic and people's lives in the Mekong River Basin every year. The objective of this study is to identify the flood hazard areas and inundation depth in the Mekong River Basin. A rainfall-runoff and flood inundation model is necessary to enhance understanding of characteristic of flooding. Rainfall-Runoff-Inundation (RRI) model, a two-dimensional model capable of simulating rainfall-runoff and flood inundation simultaneously, was applied in this study. HydoSHEDS Topographical data, APPRODITE precipitation, MODIS land use, and river cross section were used as input data for the simulation. The Shuffled Complex Evolution (SCE-UA) global optimization method was integrated with RRI model to calibrate the sensitive parameters. In the present study, we selected flood event in 2000 which was considered as 50-year return period flood in term of discharge volume of 500 km3. The simulated results were compared with observed discharge at the stations along the mainstream and inundation map produced by Dartmouth Flood Observatory and Landsat 7. The results indicated good agreement between observed and simulated discharge with NSE = 0.86 at Stung Treng Station. The model predicted inundation extent with success rate SR = 67.50% and modified success rate MSR = 74.53%. In conclusion, the RRI model was successfully used to simulate rainfall runoff and inundation processes in the large scale Mekong River Basin with a good performance. It is recommended to improve the quality of the input data in order to increase the accuracy of the simulation result.