• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제25권4호
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• pp.162-172
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• 2021

This paper proposes stochastic methods to find an approximate solution for the L²-Wasserstein least squares problem of Gaussian measures. The variable for the problem is in a set of positive definite matrices. The first proposed stochastic method is a type of classical stochastic gradient methods combined with projection and the second one is a type of variance reduced methods with projection. Their global convergence are analyzed by using the framework of proximal stochastic gradient methods. The convergence of the classical stochastic gradient method combined with projection is established by using diminishing learning rate rule in which the learning rate decreases as the epoch increases but that of the variance reduced method with projection can be established by using constant learning rate. The numerical results show that the present algorithms with a proper learning rate outperforms a gradient projection method.

• 한국산업융합학회 논문집
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• 제11권2호
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• pp.83-91
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• 2008

GMAW(Gas Metal Arc Welding) processes are usually used in industrial side in order to get its high productivity. But those are only adopted in the semi-automated welding equipment because of a lot of welding spatters. Many industrial robot actually percents from being engaged in the welding processes. The welding spatter problem of causes blocking them being a fully automated welding process.This study was carried out to investigate the optimal conditions for minimizing welding spatter generation at GMAW robot. The spatter can be significantly reduced below 2% of welding spatter generation at the following conditions ; First, below 18V at the wire-feed rate 2.0mm/min Second, below 23V at the wire-feed rate 3.6mm/min Third, below 24V at the wire-feed rate 5.5mm/min.

• 제어로봇시스템학회논문지
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• 제20권8호
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• pp.849-853
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• 2014

In micro-scale electromechanical systems, the power to perform accurate position sensing often greatly exceeds the power needed to generate motion. This paper explores the implications of sampling rate and amplifier noise density selection on the performance of a system identification algorithm using a capacitive sensing circuit. Specific performance objectives are to minimize or limit convergence rate and power consumption to identify the dynamics of a rotary micro-stage. A rearrangement of the conventional recursive least-squares identification algorithm is performed to make operating cost an explicit function of sensor design parameters. It is observed that there is a strong dependence of convergence rate and error on the sampling rate, while energy dependence is driven by error that may be tolerated in the final identified parameters.

• ETRI Journal
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• 제37권6호
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• pp.1242-1250
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• 2015

It is very important to provide a parameterized quality of service (QoS) using traffic specification (TSPEC), such as mean data rate, maximum burst size, and peak data rate, when packets from the application layer need to be transmitted with guaranteed services in a high-rate wireless personal area network (HR-WPAN). As medium resources are limited, the optimal medium time required for each device needs to be estimated to share the resources efficiently among devices. This paper proposes a variable-service interval-based resource allocation algorithm to efficiently make a reservation of medium resources based on a parameterized QoS. In other words, the proposed algorithm calculates the number of medium access slots (MASs) based on TSPEC, local resources, and local conditions and determines suitable locations for the MASs within a superframe to accommodate more devices. The simulation results show that the proposed algorithm can accommodate more devices and has greater than 10% resource allocation efficiency in an HR-WPAN compared to existing schemes.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 Ⅲ
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• pp.1239-1242
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• 2003

The neural networks are a famous model to learn the nonlinear function or nonlinear system. The main point of neural network is that the difference actual output from desired output is used to update weights. Usually, the gradient descent method is used for the learning process. On training process, if learning rate is too large, neural networks hardly guarantee convergence of neural networks. On the other hand, if learning rate is too small, the training spends much time. Therefore, one major problem in use of neural networks are to decrease the teaming time while neural networks are guaranteed convergence. In this paper, we suggest the model of fuzzy logic to neural networks to calibrate learning rate. This method is to tune learning rate dynamically according to error and demonstrates the optimization of training.

• 한국언론정보학보
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• 제34권
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• pp.7-33
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• 2006

본 논문은 근래 사회적 쟁점이 되고 있는 방송통신융합 현상을 '이윤율의 경향적 하락의 법칙'에 따라 설명하려고 했다. 새로운 단말기 시장을 조성하고 사용료 수입을 획기적으로 늘리기 위해서는 새로운 서비스를 개발해야 하는 바, 그것이 방송 서비스의 결합으로 나타난 것이다. 그 과정에서 자본의 유기적 구성의 변화, 그로 인한 이윤율의 경향적 하락, 그것을 극복하기 위한 다양한 모색 등을 살펴보았다. 통신자본과 전자산업은 생산성 향상을 위해 불변자본 부분에 대한 끊임없는 투자를 진행하는 가운데 자본의 유기적 구성이 높아지고, 따라서 이윤율이 경향적으로 하락하는 현상으로 나타났다. 이윤량은 증가하면서도 이윤율이 하락하는 현상에 대해 사업자들이 대처하는 모습들도 확인하였다. 굳이 이 법칙을 적용해본 것은, 수면 위에 나타나는 모습만 보고 쉽게 비판하는 경향을 탈피하여 현상의 본질을 규명해보고자 하는 것이었다. 진단이 정확해야 처방도 정확할 수 있기 때문이다.

• 대한의용생체공학회:의공학회지
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• 제43권4호
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• pp.271-279
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• 2022

Functional cosmetics containing various ingredients that improve skin health are currently being developed. In addition, technologies that help increase the absorption rate of such cosmetics have recently gained significant attention. Sonophoresis is a method to increase the transdermal absorption of cosmetics using ultrasound. A skin-mimicking phantom was fabricated using polydimethylsiloxane, Strat-M^TM membrane, and thermochromic pigments. Gel-type cosmetics used in skin mask packs and epidermal-growth-factor-based nano-cosmetics were tested for their absorption rates at ultrasound frequencies of 1, 3, and 10 MHz in the single frequency mode, and 1/3 and 3/10 MHz in the dual frequency mode. The gel-type cosmetics and epidermal-grow-factor-based nano-cosmetics showed the highest absorption rate at 3/10MHz dual frequency. The size of the cosmetic particles decreased by 5-9 %. Furthermore, the temperature rise caused by ultrasound could be visually recognized by the thermochromic pigment in the phantom turning white. We presented a skin-mimicking phantom. The device can be customized according to the size of the ultrasound probe and has the advantage of quantitatively evaluating the transdermal permeability of cosmetics at a low cost. The development of the skin-mimicking phantom will be useful for determining the suitable conditions required to increase the absorption rate of cosmetics using ultrasound.

• 한국정보통신학회논문지
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• 제18권8호
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• pp.1987-1994
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• 2014

본 논문에서는 외국어 계열과 IT 계열의 창의적 인력 양성을 위한 융합적 교육 방안에 관한 제언을 목적으로 한다. 학계와 기업, 그리고 정부는 지금까지 대학졸업자의 취업을 위해서 수많은 변화와 노력을 시도하였고, 더 나은 방향을 제시하고자 여러 사업과 계획들을 추진하였다. 그러나 이러한 노력에도 불구하고 여전히 대학졸업생의 취업률이 심각한 사회문제로 남아 있는 게 현실이다. 이러한 문제점을 해결하기 위하여 본 논문에서는 국내 대학 및 전문대학의 취업률을 고찰하고, 상대적으로 취업률이 저조한 외국어 계열 대학의 취업률을 높이기 위해서 IT 계열과의 융합교육 방안을 제안한다. 세부적으로 창의성, 차별성, 현지성, 그리고 융합성이라는 새로운 패러다임을 만들고, 이를 바탕으로 노동시장의 한계점을 극복할 수 있을 것으로 기대한다.

• 정보통신설비학회논문지
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• 제4권2호
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• pp.9-17
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• 2005

Coexistence of different wireless systems that share the 2.4 GHz ISM frequency band is becoming one of the most important issue. This paper presents a model of the interference that IEEE 802.11b affected by IEEE 802.15.4. The packet error rate (PER) of IEEE 802.11b under the interference of IEEE 802.15.4 is analyzed. The PER is obtained by using the bit error rate (BER) and the collision time. Further, this paper suggests a packet length to reduce the effect of the IEEE 802.15.4 interference and obtain a maximum throughput of the IEEE 802.11b. The analytical results are validated using simulation.

• 방송공학회논문지
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• 제14권3호
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• pp.332-341
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• 2009

지상파 DMB는 이동 환경에서 QVGA 급의 영상과 스테레오 오디오를 제공하는 방송 서비스로서 국내에서는 2005년 12월부터 본격적으로 서비스되고 있다. 최근에는 DMB 환경에서 고품질의 영상과 오디오를 제공하려는 기술에 대한 연구가 이루어지고 있는데, 지상파 DMB 환경에서 고품질의 영상 또는 오디오를 제공하기 위해서는 기존의 DMB 서비스에 추가적인 데이터들을 전송하는 것이 필요하다. 하나의 지상파 DMB 방송 채널에 할당되는 전송 비트율이 높지 않다는 점을 감안하면, 이러한 추가적인 데이터들을 효율적으로 전송하는 것이 서비스의 상용화 입장에서는 중요한 요소가 될 수 있다. 본 논문에서는 지상파 DMB 환경에서 멀티채널 오디오 서비스를 제공하고자 할 때, 추가적으로 전송되어야 하는 부가정보 스트림의 효율적인 전송을 위한 패킷화 방법을 제안한다.