• Proceedings of the KSPS conference
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• 2003.05a
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• pp.211-214
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• 2003

일반적으로 음성 인식에서의 성능은 잡음의 영향으로 인하여 저하된다. 전화망을 통한 한국어 연속 숫자음 인식은 음성인식 분야에 있어서 어려운 영역에 속하는데, 이는 조음 현상으로 인한 인식률 저하되는 점과 전화망 채널의 영향으로 인하여 스펙트럼 포락이 왜곡되며 음성신호의 대역폭이 제한되기 때문이다. 본 논문에서는 잡음의 영향을 줄이기 위하여, 2WF(2-stage Wiener Filter) 와 SWP (SNR-dependent Waveform Processing) 그리고 CMN(Cepstrum Mean Normalization)을 사용하였다. 2WF는 음성 신호의 포만트 구조를 적게 왜곡시키면서 전체적인 가산잡음 뿐만 아니라 동적 가산잡음도 줄여준다. SWP는 음성파형에서 SNR값이 상대적으로 큰 부분을 강조하여 전체적인 SNR을 향상시킬 수 있다. 또한, CMN은 특징벡터로부터 채널잡음의 영향을 정규화하여 음성 인식 성능을 향상시킨다. 이러한 방법들을 전화망 한국어 연속 숫자음 DB를 이용하여 실험한 결과, 음성신호의 왜곡을 최소화하면서 잡음의 영향을 줄여 전화망에서의 숫자음 인식 성능을 향상시킬 수 있었다.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.135-144
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• 1998

High speed machining is a key issue in die and mold manufacturing recently. Even though this technology has great potential of high productivity. tool wear accelerated by high cutting speed to the hardened materials is other barrier. In this research, we attempted to reduce tool wear by considering tool inclination angle between tool and workpiece. The boundary lines describing machined sculptured surfaces were represented by both of cutting envelop condition and the geometric relationship of successive tool paths. Chip cross section, and cutting length could be obtained from the calculated cutting edge and the rotational engagement angle. From the simulation results, machining inclination angle of tool of $15^\circ$ was good enough from the point of tool wear and cutting force, and this value was verified through the cutting experiment of high speed ball end milling.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.12
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• pp.1243-1249
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• 2008

Gear system has been widely used in industrial applications and unexpected failures of gears are not only extremely damaging but also leading to economic losses. So, early detection of fault is important for diagnosis machine condition. And acoustic emission is an efficient non-destructive testing technique fur the diagnosis of machine health and is useful technique far early detection of fault because it can find low-amplitude and high-frequency signal on account of high sensibility. Therefore, in this paper, the AE signal was measured and preprocessed using envelope analysis for gearbox with misalignment between pinion and gear. And then the gear misalignment's vibration characteristic were analyzed.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.697-704
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• 2019

The public has grown more anxious towards domestic earthquakes that have been taking place since 2000, and regulations on seismic design has been strengthened. Out of 4,605 Air Force installations that require the application of seismic design, 2,982 remain unapplied. By taking budget issues and the time spent to implement seismic retrofit into account, this paper aims to list up seismic reinforcement priorities for airmen dormitories where they can potentially be most vulnerable to earthquakes. The priorities are extracted based on Data Envelope Analysis(DEA). To apply DEA, two sets of variables are set: seismic reinforcement costs as input variable: age of building, number of residents, and seismic load as output variables. At the end, suggestions are made for developing seismic reinforcement plans that can be applied to all Air Force installations.

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.1-10
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• 1992

A simple formula of the envelope method, which uses two envelopes fitted to the transmittance at quarter- and half-wave optical thicknesses, is derived to determine the optical constants (refractive index and extinction coefficient) and the thickness of weakly absorbing thin films. We applied the envelope method to ZnS and SiOx films deposited in a vacuum chamber and determined the optical constants at different deposition conditions. For SiOx films, the decrease in refractive index is consistent with the increase in stoichiometry as the backfilled oxygen pressure increases.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.340-342
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• 2020

본 논문에서는 CNN을 이용한 TCX 모드 기반의 주파수 정보 복원 기술을 제안한다. TCX 모드는 USAC에서 지원하는 음성을 위한 양자화 기술로 부호화 과정에서 포락선을 평탄화한 후 양자화한다. 이러한 평탄화 동작은 주파수 정보 간의 상관도를 높여 네트워크의 학습을 쉽게 만들고 예측 성능을 높인다. 제안하는 방법은 청각 심리 모델 기반으로 구현된 주파수 정보 복원 방법에 TCX 모드 기반의 양자화 방법을 적용하여 일부 주파수 정보만을 사용해 손실된 주파수 정보를 복원한다. 제안하는 방법을 사용해 기존 방법보다 낮은 학습 오차를 얻었고 최적화 되지 않은 조건에서 동등한 음질을 얻었다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.07a
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• pp.347-348
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• 2023

본 연구에서는 다년간 계속되어 온 공기업의 개혁 성과에 대해 경영효율성 관점에서 살펴보고자 한다. 공기업을 포함한 공공기관의 개혁 움직임은 부채 수준의 급증 문제에서 시작되었으며, 방만 경영으로 대표되는 비효율적인 경영방침이 지속된다면 미래 정부에 큰 부담으로 작용할 것으로 우려되었기 때문이다. 공공기관의 효율적 경영은 자료포락분석에 의한 DEA로 측정하능하며, 본 연구에서는 DEA의 시계열적 변화를 살펴봄으로써 공공기관이 개혁과정이 성공적이라 평가할 수 있는지 점검해보고자 하였다. 또한, 매년 발표되는 경영평가결과를 바탕으로 우수 공공기관과 그렇지 않은 공공기관에서 이러한 시계열적 추세에 차이가 존재하는지를 살펴보아 향후의 공공기관 개혁에 방향성을 제시할 수 있는 보다 명확한 분석결과를 제시하고자 한다. 본 연구의 결과는 공공기관의 성공적인 개선을 이루기 위한 중간점검 차원에서 이해될 수 있으며, 비효율성을 개선하기 위해 어떠한 기관이 더욱 노력해야 하는지에 대한 답을 제공할 것으로 기대된다.

• Journal for History of Mathematics
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• v.37 no.4
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• pp.93-105
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• 2024

Research on the caustic, the envelope of light rays, began with the geometric optics studies of Huygens and others in the 17th century. One of the most important problems in optics in the 17th century was focusing the sun's rays. This was a problem that had to be solved in order to manufacture various practical optical instruments at the time. Beginning with research on the caustic during this period, the concept of envelope became generalized and expanded to various fields until the 19th century. This paper examines the mathematical history involved in the study of envelope curves. We compare several methods of defining the envelope and provide an example of calculating the envelope accordingly.

• Korean Journal of Social Welfare
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• v.52
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• pp.117-141
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• 2003

This study is to identify the efficiency in Busan social welfare agencies between input factors and output factors. For this purpose, gathered are the 2001 services reports of those study agencies. This study used 4 difference model, model 1; comparing input factor(social worker number & labor cost) about output factor(the total number of program used person), model 2; comparing input factor(the total number of social welfare agencies staff & the total working expenses) about output factor(the total number of program used person), model 3; comparing input factor(the total number of volunteer, social welfare agencies staff & a period of operation) about output factor(the total number of program used person), model 4; comparing input factor(the total number of volunteer, social welfare agencies staff, a period of operation & the total working expenses) about output factor(the total number of program used person). Charnes's study(1978) provided an analytical tool for efficiency services output of non-profit organizations, and DEA(Data Envelopment Analysis) was a analytical framework for evaluating the impact of social service outcome. the finding are as follows : (1) In the results of comparing 4 models as same standard, we can find 35-55%(16-25) efficiency agencies among the 45 social welfare agencies. (2) For all DMU becoming the efficiency 1 to standard of output factor, model 1; 33 agencies are increasing the social worker number($\Delta$0.8 number), 10 agencies are raising the labor cost of social worker($\Delta$1,189,000 Won), model 2; 30 agencies are increasing the total number of social welfare agencies staff($\Delta$1.25 number), 14 agencies are raising the total working expenses($\Delta$1,447,000 Won), model 3; 8 agencies are increasing the total number of social welfare agencies staff($\Delta$2.26 number), 14 agencies are increasing the total number of volunteer($\Delta$52 number), and 10 agencies are increasing a period of operation($\Delta$13 month), model 4; 24 agencies are increasing the total number of social welfare agencies staff($\Delta$1.8 number), 12 agencies are raising the total working expenses($\Delta$5,017,000 Won), 12 agencies are increasing the total number of volunteer($\Delta$43.2 number), and 23 agencies are increasing a period of operation($\Delta$16 month).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.331-336
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• 2004

In order to strengthen the competitiveness of port against calling for the huge vessel and reducing the shipping service time, the productivity of container terminal must be improved. This productivity variously results according to the kinds of productivity evaluation model, input elements like yard, equipment, employee, facility, etc,. But, it is discussed that the productivity is measured by partial productivity evaluation model or general input elements. Therefore, we measured for the productivity of the container terminal using the Developed the data Envelopment Analysis (DEA), which is developed in order to evaluate the relative efficiency of decision making units - it's difficult to clear cause and effect between input and output. We measured the whole productivity of container terminal in Busan according to decision of the correct input elements. And we investigated the change of the productivity measurement result according to input elements, presents more accurate productivity evaluation model in container terminal.