• 전기학회논문지P
• /
• 제57권4호
• /
• pp.377-382
• /
• 2008

For stator winding protection of AC generator, KCL(Kirchhoff's Current Law) is widely applied. Actually a CRDR(Current Ratio Differential Relay) based on DFT(Discrete Fourier Transform) has been used for protecting generator. It has been pointed out that defects can occur during the process of transforming a time domain signal into a frequency domain one which can lead to loss of time domain information. Wavelets techniques are proposed for the analysis of power system transients. This paper introduces an algorithm to choose a suitable Mother Wave1et for generator stator fault detection. For optimal selection, we analyzed db(Daubechies), sym(Symlets), and coif(Coiflects) of Mother Wavelet. And we compared with performance of the choice algorithm using detail coefficients energy and RMS(root mean square) error. It can be improved the reliability of the conventional DFT based CRDR. The feasibility and effectiveness of the proposed scheme is proved with simulation using collected data obtained from ATP (Alternative Transient Program) package.

• 응용통계연구
• /
• 제30권5호
• /
• pp.733-745
• /
• 2017

국소복합분위수 회귀모형을 활용한 비모수적 함수 추정방법이 높은 효율성과 더불어 활발히 연구되고 있다. 이러한 추정과정에 커널을 사용한 자료 평활방법이 대표적으로 사용되고 있으며, 그 성능은 커널보다는 평활계수의 선택 크게 의존한다. 한편, 회귀함수 추정방법의 성능을 평가하는 기준으로는 통상적으로 $L_2$-노름이 사용되어 평균제곱오차 또는 평균적분제곱오차를 최소화하는 평활계수의 선택에 대한 많은 연구가 진행되어 왔다. 본 논문에서는 국소선형 복합 분위수 회귀방법을 활용한 비모수 회귀모형 추정량의 성능을 결정하는 평활계수 선택의 최적성에 관해 연구하였다. 특히, 여러 장점을 가졌으나 수리적 어려움으로 연구가 미흡한 평균절대오차 및 평균적분절대오차를 최적의 기준으로 삼아 최적의 평활계수를 구하고 그 유일성에 관해 연구하였다. 나아가 기존의 평가기준인 평균제곱오차 및 평균적분제곱오차를 사용한 선택과의 관계를 파악하고 그 성능을 비교하였다. 이러한 과정에서 다양한 상황에서의 모의실험을 통해 제안한 방법의 특성을 규명하였다.

• Design & Manufacturing
• /
• 제11권2호
• /
• pp.1-8
• /
• 2017

In this study, we applied microcellular foaming injection molding process to improve the performance of system air-conditioner drain fan which had been produced by injection molding process and studied the optimization of process conditions through 6-sigma process and response surface method (RSM) to reduce weight and deformation of products. Additive type, melt temperature, mold temperature, and injection screw shape were selected as the factor affecting the weight and deformation of the products by carrying out analysis of trivial many through ANOVA and design of experiment (DOE) method. Among the effect factor, we set the addictive type to Long G/F and screw shape to foaming screw which had the highest level of weight reduction and deformation reduction. The amount of foaming agent gas was set at 60 ml, which was the limit beyond which the weight of product did not decrease any more. For melt temperature and mold temperature, we studied the conditions where both weight and deformation were minimized using the RSM. As a result, we set the melt temperature to $250^{\circ}C$, fixed mold temperature to $20^{\circ}C$, and moving mold temperature to $40^{\circ}C$. The improvement effect was analyzed by appling the selected optimal conditions to the production process using the microcellular foaming injection molding. The results showed that the mean weight of product was measured to be 1,420g which was 19% lower than that measured in the current process. The standard deviations of the weights were found to be similar to those in the current process and it showed a low dispersion. The mean deformation was measured to be 0.9237mm, which represented a 57% reduction compared to the mean deformation in the current process, and the standard deviation decreased from 0.3298mm to 0.1398mm. Moreover, we analyzed the process capability for deformation, and the results showed that the short-term process capability increased from 2.73 to 6.60 which was even higher than targeted level of 6.0.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권2호
• /
• pp.579-603
• /
• 2018

In this paper we propose a QoS-enhanced intelligent stochastic optimal fair real-time packet scheduler, QUEST, for 4G LTE traffic in routers. The objective of this research is to maximize the system QoS subject to the constraint that the processor utilization is kept nearly at 100 percent. The QUEST has following unique advantages. First, it solves the challenging problem of starvation for low priority process - buffered streaming video and TCP based; second, it solves the major bottleneck of the scheduler Earliest Deadline First's failure at heavy loads. Finally, QUEST offers the benefit of arbitrarily pre-programming the process utilization ratio.Three classes of multimedia 4G LTE QCI traffic, conversational voice, live streaming video, buffered streaming video and TCP based applications have been considered. We analyse two most important QoS metrics, packet loss rate (PLR) and mean waiting time. All claims are supported by discrete event and Monte Carlo simulations. The simulation results show that the QUEST scheduler outperforms current state-of-the-art benchmark schedulers. The proposed scheduler offers 37 percent improvement in PLR and 23 percent improvement in mean waiting time over the best competing current scheduler Accuracy-aware EDF.

• The Korean Journal of Pain
• /
• 제33권1호
• /
• pp.60-65
• /
• 2020

Background: Anatomic changes in the acromion have been considered a main cause of shoulder impingement syndrome (SIS). To evaluate the relationship between SIS and the acromion process, we devised a new morphological parameter called the acromion process cross-sectional area (APA). We hypothesized that the APA could be an important morphologic diagnostic parameter in SIS. Methods: We collected APA data from 95 patients with SIS and 126 control subjects who underwent shoulder magnetic resonance imaging (MRI). Then we measured the maximal cross-sectional area of the bone margin of the acromion process on MRI scans. Results: The mean of APAs were 136.50 ± 21.75 ㎟ in the male control group and 202.91 ± 31.78 ㎟ in the male SIS group; SIS patients had significantly greater APAs (P < 0.001). The average of APAs were 105.38 ± 19.07 ㎟ in the female control group and 147.62 ± 22.90 ㎟ in the female SIS group, and the SIS patients had significantly greater APAs (P < 0.001). The optimal APA cut-off in the male group was 165.14 ㎟ with 90.2% sensitivity, 91.4% specificity, and an area under the curve (AUC) of 0.968. In the female group, the optimal cut-off was 122.50 ㎟ with 85.2% sensitivity, 84.9% specificity, and an AUC of 0.928. Conclusions: The newly devised APA is a sensitive parameter for assessing SIS; greater APA is associated with a higher possibility of SIS. We think that this result will be helpful for the diagnosis of SIS.

• 한국식품영양학회지
• /
• 제29권6호
• /
• pp.985-997
• /
• 2016

The objectives of this study, which filled gaps in previous studies, were: (1) to find the optimal mixing condition of nanoemulsions containing oleoresin capsicum (OC), Tween 80, propylene glycol (PG), and sucrose monostearate (SES) by microfluidization; (2) to investigate their properties and stability depending on such factors as pH, temperature, and heating time; (3) to measure the effect of adding ascorbic acid. In order to test these objectives, the following three experiments were conducted: Firstly, in order to find the optimal mixing ratio, nanoemulsions containing OC - the mean diameter of which is smaller than 100 nm - were prepared through the process of microfluidization; and their mean particle size, zeta potential, and capsaicinoids were measured. The test results indicated that the mixing ratio at OC : Tween 80 : PG + water(1:2) = 1 : 0.2 : 5 was optimal. Secondly, the properties and stability of nanoemulsions were investigated with varying parameters. The test results illustrated that single-layer nanoemulsions and double-layer nanoemulsions coated with alginate were stable, irrespective of all the parameters other than/except for pH 3. Thirdly, the properties of nanoemulsions were then analyzed according to the addition of ascorbic acid. The results demonstrated that the properties of single-layer nanoemulsions were not affected by addition of ascorbic acid. In case of alginate double-layer nanoemulsions, the particle size was reduced, and zeta potential increased with the addition of ascorbic acid. In conclusion, the demonstrated stability of various nanoemulsions under the different conditions in the present study suggests that these findings may constitute a basis in manufacturing various food-grade products which use nanoemulsions-and indicate that food nanoemulsions, if adopted in the food industry, have the potential to satisfy both the functionality and acceptability requirements necessary to produce commercially marketable food-grade products.

• Journal of the Korean Data and Information Science Society
• /
• 제21권2호
• /
• pp.279-289
• /
• 2010

이 논문에서는 호흡곤란을 주호소로 내원한 668명의 환자를 대상으로 입퇴원 결정을 위한 간편한 통계모형을 제안한다. 이것을 위해 55개 변수 중 임상전문가에 의해 중요하다고 선택된 11개 변수를 설명변수로 이용하였다. 먼저 변환과정으로 11개 연속형 변수 각각에 대해 실제 입원과 퇴원 환자의 커널밀도함수에 의해 퇴원구간을 설정하였다. 다음으로 11개 설명변수 중 퇴원구간에 속한 변수의 개수를 가지고 환자의 퇴원여부를 결정하는 최적 모형을 선택하였다. 입원과 퇴원 환자수의 불균형 때문에 최적 모형의 선택기준으로는 민감도와 특이도의 산술평균과 민감도와 정확률의 조화평균을 이용하였다. 그 결과 11개의 검사결과 중 7개 이상에서 퇴원구간이 나오면 퇴원을 결정하는 것이 최적 모형이 되었다.

• 한국미생물·생명공학회지
• /
• 제2권1호
• /
• pp.29-35
• /
• 1974

We have studied the applicability of the principles and inherent advantages of the two-stage dontinuous uclture technique to an enzyme process for the purpose of improving and optimizing the productivity of 3-ketosteroid-delta-1-dehydrogenase. By using a two-stage continuous culture system, the growth st ageand enzyme produdtion stage are separated. In each stage an optimal set of toperaing conditions was determined, and this was tested for feasibility for the period of 10 days. During this period, at least 70％ of the maximum enzyme productivity could be maintained. The important design parameters studied are: (1) optimal specific growth rate in the first stage which corresponds to the maximal cell productivity, (2) the optimal dilution rate in the second stage which in turn determines the size of second stage fermentor and the mean residence time of cells in the second stage, (3) cell concentration in both stages, add (4) the specific enzyme productivity and enzyme productivity of the second stage. In addition, by using two-stage continuous culture system we have been able to reduce or eliminate the effect of catabolite repression due to high medium concentration and the adverse effect of the solvent used to dissolve the inducer. We have found the balance between the opposing effects of induction and repression in the second stage judging from the observation that the enzyme productivity goes through a maximum.

• Smart Structures and Systems
• /
• 제31권6호
• /
• pp.545-559
• /
• 2023

Nanoparticle strips (NPS) are widely used as external reinforcers for two-way reinforced concrete slabs. However, the Structural Health Monitoring (SHM) of these slabs is a very important issue and was evaluated in this study. This study has been done analytically and numerically to optimize the placement of sensors. The properties of slabs and carbon nanotubes as composite sheets were considered isotopic and orthotropic, respectively. The nonlinear Finite Element Method (FEM) approach and suitable optimal placement of sensor approach were developed as a new MATLAB toolbox called DECOMAC by the authors of this paper. The Suitable multi-objective function was considered in optimized processes based on distributed ECOMAC method. Some common concrete slabs in construction with different aspect ratios were considered as case studies. The dimension and distance of nano strips in retrofitting process were selected according to building codes. The results of Optimal Sensor Placement (OSP) by DECOMAC algorithm on un-retrofitted and retrofitted slabs were compared. The statistical analysis according to the Mann-Whitney criteria shows that there is a significant difference between them (mean P-value = 0.61).

• 한국컴퓨터산업학회논문지
• /
• 제2권6호
• /
• pp.817-826
• /
• 2001

본 논문에서는 훼손된 신호를 처리하는 방법에 대해 연구하였다. 기존의 처리방법은 특이점이나 악 조건일 경우 수렴 속도가 늦어진다는 점과 처리시간이 많이 소요되는 단점이 있다. 이러한 단점을 보완하기 위하여 Gauss-Seidel 방법으로 처리하는 방법이 있으나 이러한 경우 신호를 반복해서 처리해야 하므로 처리시간이 많이 소요된다. 이러한 단점(수렴 속도, 전체 처리시간)을 개선하기 위하여 본 논문에서는 기존의 신호처리 (Tikhnov-Miller)와 제안된 알고리즘을 적용시켜 비교하여 봄으로써 특이점 혹은 악조건일 경우에도 수렴속도를 고속화하여 기존의 Tikhnov-Miller 신호 처리 방법보다 처리 시간을 단축할 수 있는 신호 처리 방법을 제시하였다. 제안된 최적화 알고리즘을 영상신호에 적용시켜 가속 상수에 따른 처리 신호에 대한 실험과 오차(mean-square error)의 변화를 비교하여 봄으로써 처리정도를 알아보았다. 그리고, 본 알고리즘의 유효성을 입증하기 위하여 모든 가속상수의 변화에 대한 신호처리 결과와 처리시간을 측정하였다.