• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.551-554
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• 2005

The method of the reduction of the automotive induction noise can be classified by the method of passive control and the method of active control. However, the passive control method has a demerit to reduce the effect of noise reduction at low frequency (below 500Hz) range and to be limited by a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used the LMS (Least-Mean-Square) algorithm because the LMS algorithm can easily obtain the complex transfer function in real-time. Especially, When the Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm goes bad when the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. Thus Normalized FXLMS algorithm was developed to improve the control performance under the rapid acceleration. The advantage of Normalized FXLMS algorithm is that the step size is no longer constant. Instead, it varies with time. But there is one additional practical difficulty that can arise when a nonstationary input is used. If the input is zero for consecutive samples, then the step size becomes unbounded. So, in order to solve this problem. the Correlation FXLMS algorithm was developed. The Correlation FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Correlation FXLMS Is presented in comparison with that of the other FXLMS algorithms based on computer simulations.

• Asia-Pacific Journal of Business
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• v.12 no.1
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• pp.209-223
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• 2021

Purpose - The purpose of this study was to investigate the relationship between Korea agricultural productions and Greenhouse Gas (GHG) emissions based on Environmental Kuznets Curve (EKC) hypothesis. Design/methodology/approach - This study utilized time series data of economic growth, greenhouse gas, agricultural productions, trade dependency, and energy usages. In order to econometric procedure of EKC hypothesis, this study utilized unit root test and cointegration test to check staionarity of each variable and also adopted Vector Error Correction Model (VECM) and Ordinary Least Square (OLS) to analyze the short and long run relationships. Findings - In the short run, greenhouse gas emissions resulting from economic growth show an inverse U-shape relationship, and an increase in agricultural production and energy consumption led to increase in greenhouse gas emission. In the long run, total GHG emissions and CO2 emissions show an N-shaped relationship with economic growth, and an increase in agricultural production has resulted in a decrease in total GHG and CO2 emissions. However, methane (CH4) and nitrous oxide (N2O) emissions showed an inverse U-shape relationship with economic growth, which indicated the environment and production process of agricultural production. Research implications or Originality - Korea agricultural production has different effects on the GHG emission sources, and in particular, methane (CH4) and nitrous oxide (N2O) emissions show to increase as the agricultural production expansions, so policy or technological development in related sector is required. Especially, in the context of the 2030 GHG reduction road-map, if GHG-related reduction technologies or policies are spread, national GHG emission reduction targets can be achieved and this is possible to predict the decline in production in the sector and damage to the related industries.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.4
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• pp.323-327
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• 2021

This paper produced SUS MASK, which is used for OLEDs, using an automatic liquid management system. The SUS MASK was tested by setting the hole diameter to 0.4 mm. The additive F300 was found to be excellent as the hole diameter was close to 0.4 mm and the error range was measured to be 0.08 on average. And as a result of measuring the weight reduction amount of CuCl2 and FeCl3 according to the change in oxidation-reduction potential (ORP), FeCl3 is relatively sensitive to ORP changes. Experiments were conducted on whether ORP (610 mV) and specific gravity (1.463) were automatically controlled while continuously etching the SUS Mask. Experimental results show that the automatic liquid management system is well controlled because the setting value is not significantly changed. After setting the hole diameter to 0.4 mm as the target, the experiment results were measured from 0.36 to 0.44. Therefore, it is expected that etching processing in the manufacturing process of SUS MASK can be improved with higher precision by applying the manufactured automatic liquid management system.

• Journal of the Korean Society of Radiology
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• v.18 no.2
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• pp.93-99
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• 2024

The digital medical imaging, especially, computed tomography (CT), should necessarily be considered in terms of noise distribution caused by converting to X-ray photon to digital imaging signal. Recently, the denoising technique based on deep learning architecture is increasingly used in the medical imaging field. Here, we evaluated noise reduction effect according to various noise types based on the U-net deep learning model in the lung CT images. The input data for deep learning was generated by applying Gaussian noise, Poisson noise, salt and pepper noise and speckle noise from the ground truth (GT) image. In particular, two types of Gaussian noise input data were applied with standard deviation values of 30 and 50. There are applied hyper-parameters, which were Adam as optimizer function, 100 as epochs, and 0.0001 as learning rate, respectively. To analyze the quantitative values, the mean square error (MSE), the peak signal to noise ratio (PSNR) and coefficient of variation (COV) were calculated. According to the results, it was confirmed that the U-net model was effective for noise reduction all of the set conditions in this study. Especially, it showed the best performance in Gaussian noise.

• Progress in Medical Physics
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• v.25 no.2
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• pp.72-78
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• 2014

The aim of the study is to test a hypothesis that quasi-breath-hold (QBH) biofeedback improves the residual respiratory motion management in gated 3D thoracic MR imaging, reducing respiratory motion artifacts with insignificant acquisition time alteration. To test the hypothesis five healthy human subjects underwent two gated MR imaging studies based on a T2 weighted SPACE MR pulse sequence using a respiratory navigator of a 3T Siemens MRI: one under free breathing and the other under QBH biofeedback breathing. The QBH biofeedback system utilized the external marker position on the abdomen obtained with an RPM system (Real-time Position Management, Varian) to audio-visually guide a human subject for 2s breath-hold at 90% exhalation position in each respiratory cycle. The improvement in the upper liver breath-hold motion reproducibility within the gating window using the QBH biofeedback system has been assessed for a group of volunteers. We assessed the residual respiratory motion management within the gating window and respiratory motion artifacts in 3D thoracic MRI both with/without QBH biofeedback. In addition, the RMSE (root mean square error) of abdominal displacement has been investigated. The QBH biofeedback reduced the residual upper liver motion within the gating window during MR acquisitions (~6 minutes) compared to that for free breathing, resulting in the reduction of respiratory motion artifacts in lung and liver of gated 3D thoracic MR images. The abdominal motion reduction in the gated window was consistent with the residual motion reduction of the diaphragm with QBH biofeedback. Consequently, average RMSE (root mean square error) of abdominal displacement obtained from the RPM has been also reduced from 2.0 mm of free breathing to 0.7 mm of QBH biofeedback breathing over the entire cycle (67% reduction, p-value=0.02) and from 1.7 mm of free breathing to 0.7 mm of QBH biofeedback breathing in the gated window (58% reduction, p-value=0.14). The average baseline drift obtained using a linear fit was reduced from 5.5 mm/min with free breathing to 0.6 mm/min (89% reduction, p-value=0.017) with QBH biofeedback. The study demonstrated that the QBH biofeedback improved the upper liver breath-hold motion reproducibility during the gated 3D thoracic MR imaging. This system can provide clinically applicable motion management of the internal anatomy for gated medical imaging as well as gated radiotherapy.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.661-668
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• 2009

Effective beam width model(EBWM) has been used for analysis of post-tensioned(PT) flat plate slab frames under lateral loads. The accuracy of this model in predicting lateral drifts and unbalanced moments strongly depends on the estimated effective stiffness of PT flat plate slabs. As moments on the slab due to lateral loads increases, cracks occur which leads to stiffness reduction in slabs. For analyzing PT flat plate slab structure under lateral loads with good precision, reduction in slab stiffness has to be accurately estimated for EBWM. For this purpose, this study collected test results of PT flat plate system conducted by former researches. And this study reduced the width of slab so that the stiffness of the EBWM converged into the lateral stiffness of each test specimens by trial and error. By conducting nonlinear regression analysis using the stiffness ratio of the reduced width of slab to the effective width of EBWM with respect to the level of slab moments, an equation for calculating stiffness reduction factor for slab is proposed. For verifying the accuracy of the proposed equation, this study compared with the test result of the PT flat plate frame. It is shown that the EBWM with the proposed equation predicts the actual stiffness of the PT specimen which varied according to the level of applied moment.

• Radiation Oncology Journal
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• v.29 no.2
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• pp.107-114
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• 2011

Purpose: To assess the degree and clinical impact of location error of the dens on the X-axis during radiotherapy to brain and head and neck tumors. Materials and Methods: Twenty-one patients with brain tumors or head and neck tumors who received three-dimensional conformal radiation therapy or intensity-modulated radiation therapy from January 2009 to June 2010 were included in this study. In comparison two-dimensional verification portal images with initial simulation images, location error of the nasal septum and the dens on the X-axis was measured. The effect of set-up errors of the dens was simulated in the planning system and analyzed with physical dose parameters. Results: A total of 402 portal images were reviewed. The mean location error at the nasal septum was 0.16 mm and at the dens was 0.33 mm (absolute value). Location errors of more than 3 mm were recorded in 43 cases (10.7%) at the nasal septum, compared to 133 cases (33.1%) at the dens. There was no case with a location error more than 5 mm at the nasal septum, compared to 11 cases (2.7%) at the dens. In a dosimetric simulation, a location error more than 5 mm at the dens could induce a reduction in the clinical target volume 1 coverage (V95: 100%${\rightarrow}$87.2%) and overdosing to a critical normal organ (Spinal cord V45: <0.1%${\rightarrow}$12.6%). Conclusion: In both brain and head and neck radiotherapy, a relatively larger set-up error was detected at the dens than the nasal septum when using an electronic portal imaging device. Consideration of the location error of the dens is necessary at the time of the precise radiation beam delivery in two-dimensional verification systems.

• International Journal of Automotive Technology
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• v.7 no.4
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• pp.477-483
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• 2006

A vibration model of a helical gear pair for vehicle transmission is developed by considering the elastic deformation of the active teeth and the body to be a rigid. The main source of vibration in a helical gear system which caused by the mass unbalances of rotors and the transmission errors of gearings in mathematically formulated and applied to the analysis of vibration characteristics of geared systems. As an example, a simple geared system containing a helical gearing is considered. The critical speeds are found by the Campbell diagram and compared with the experimental results We expect this developed program to contribute to the reduction of the vibration and noise on vehicle a transmission in the field of both design and manufacturing. In addition, this program can be used as a basic program for CAD/CAM of low-noised gear teeth.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.784-788
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• 2008

In this research, we propose a remote speech input unit, a new method of user-friendly speech input in speech recognition system. We focused the user friendliness on hands-free and microphone independence in speech recognition applications. Our module adopts two algorithms, the automatic speech detection and speech enhancement based on the microphone array-based beamforming method. In the performance evaluation of speech detection, within-200msec accuracy with respect to the manually detected positions is about 97percent under the noise environments of 25dB of the SNR. The microphone array-based speech enhancement using the delay-and-sum beamforming algorithm shows about 6dB of maximum SNR gain over a single microphone and more than 12% of error reduction rate in speech recognition.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 1999.10a
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• pp.131-137
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• 1999

전문가시스템 개발에 있어서 지식획득 병목현상(knowledge acquisition bottleneck)은 해결해야 할 큰 걸림돌중 하나이다. 지식획득을 위한 여러 과정을 단순화하고 자동화함으로 지식공학자의 작업을 최소화하면서 전문지식을 쉽고 빠르게 획득할 수 있도록 지식획득시스템을 설계·구현한다면 전문가시스템의 대중화는 지금보다 쉽게 이루어질 것이다. 본 연구는 지식 획득시스템 설계와 구현을 위한 연구의 일환으로 기계학습의 한 방법인 PIPPER(Repeated Incremental Pruning to Produce Error Reduction)를 이용하여 규칙을 생성하고 생성된 규칙을 JESS(Justification based Expert System Shell)에서 처리하도록 하였다. 규칙을 생성하기 위한 데이터는 Bohanec이 1997년도에 만든 자동차 평가 데이터베이스(Car Evaluation Database)를 사용하여 실험하였으며, 1700여 개의 레코드에서 약 40개의 규칙이 생성되었고, 생성된 규칙은 지식베이스의 정당성을 위반하지 않으면서 실행되었다.