• 산업경영시스템학회지
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• 제1권1호
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• pp.37-44
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• 1978

The purpose of this study is to search for an efficient application method in solving delay-phenomenon problems which influence upon total production cost through case study. The method of this study is an experimental study based on cutting time data in lead cutting operations from "Lead Cutting Machine (Stripper)" and its service rate data from a large electronic products company which utilizes conveyor line system for the products "Car Stereo" The procedure of this experimental study is as follows; 1) Using loading(Man-Hour) analysis technique j,1 order to analyse and evaluate Production capacity, efficiency, operation and idle rate assembly charge, waiting and service cost -when its are controlled by stripper operator(server) 2) Establishing adequate waiting time model of finite population caused by the interference of 4 stripper machine which is drawn from mathematical statistics testing, that is, goodness of fit test in the waiting and service rate and to search for optimal solution by utilizing the above mentioned model The experimental result was that amount to 8,546,618won Per year was brought down, that is, by optimum point, it shows a decrease as compared with Present point. The major limitation of this experimental study is that the Queue in the Finite Population, so to speak. it comes from the interference of 4 stripper machine dealt with this case were limited only on the Car Stereo conveyor line. Further study of application of this application method to the areas such as material handling, personnel management marketing and transportation management is strong1y recommended.trong1y recommended.

• 한국통신학회논문지
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• 제28권6A호
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• pp.371-378
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• 2003

CDMA 시스템에서 셀의 용량은 그 셀에서 사용 가능한 채널의 수로 정의되고, 이는 셀이 받는 간섭의 양에 의해 제한된다. 새로운 이동국이 홈 셀 에서 호가 수락되었을 경우, 이는 홈 또는 인접 셀 에 간섭을 준다 따라서, 본 논문에서는 홈 셀은 새로운 호를 수락할 만큼 용량이 충분하고, 새로운 이동국이 홈 셀에 수락되었을 때 이동국의 송신 전력을 예측 계산한 후, 이를 이용하여 인접 셀들이 받을 간섭의 양을 예측하여 인접 셀 들에서 QoS(Quality of Service)가 보장될 경우 호를 수락하는 이동국의 송신 전력 예측에 기반을 둔 호 수락 방식을 제안한다. 모의 실험 결과 제안한 방식은 인접 셀 에서 기존 호의 회손 확률(outage probability)이 현저히 감소함을 보여 준다.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.177-184
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• 2023

In order to reserve frequency bands for stable operation of the Korean Positioning System (KPS), it must be demonstrated that the impact of interference caused by KPS on other services operating in the same bands is tolerable. The International Telecommunication Union (ITU) provides the radio regulations and a compatibility assessment methodology for the coexistence of different services in limited frequency resources. The purpose of this paper is to investigate the radio regulations regarding the compatibility issues between the KPS and other services sharing the same frequency bands. The results of the investigation show that the RNSS system can be operated in the L5-band under the condition that the Power Flux Density (PFD) and Aggregated Equivalent PFD (AEPFD) thresholds specified in the radio regulations are met. In addition, the ITU recommends that the interference-to-noise ratio (INR) protection criteria be met to prevent degradation of the performance of radar systems operating in the L2/L6-band. In the case of the S-band, coordination of allocations for RDSS space stations with respect to terrestrial services is not required if the PFD does not exceed regulated thresholds regulated by ITU.

• Journal of Communications and Networks
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• 제11권2호
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• pp.187-195
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• 2009

The application of mathematical analysis to the study of wireless ad hoc networks has met with limited success due to the complexity of mobility, traffic models and the dynamic topology. A scenario based universal mobile telecommunications system (UMTS) time division duplex (TDD) opportunistic cellular system with an ad hoc behaviour that operates over UMTS frequency division duplex (FDD) licensed cellular network is considered. In this paper, we present a new routing metric which overall improves system performance in terms of interference and routing which operate in an ad hoc network in an opportunistic manner. Therefore we develop a simulation tool that addresses the goal of analysis and assessment of UMTS TDD opportunistic radio system with ad hoc behavior in coexistence with a UMTS FDD primary cellular networks.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1996년도 추계학술대회 학술발표 논문집
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• pp.323-326
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• 1996

In this paper, we propose a new method of the communication system for cooperative behavior and control in a collective autonomous mobile robots. A communication function among the collective robots is essential to intelligent cooperation. In general, global communication is effective for small number of robots. However when the number of robot goes on increasing, this becomes difficult to be realized because of limited communication capacity and increasing amount of information to handle. And also the problems such as communication interference and improper message transmission occur. So we propose local communication system based on infrared sensor to realize the cooperative behavior and control as the solution of above problem. It is possible to prevent overflow of information and exchange of complex information by combining communicate a specific robot. At last we verify the effectiveness of the proposed communication system from example of cooperative behavior.

• 농업과학연구
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• 제22권1호
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• pp.11-23
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• 1995

The CAD/CAM system for the manufacturing automation is the newest technology in mechanical engineering area and becomes the important research subject nowadays. Most of all hardwares and softwares for the CAD/CAM system used in the our manufacturing companies such as automobile company are developed by the foreign country and the purchasing price of them is very expensive but their applicability to a certain area is very limited. This study was conducted to develope a CAD/CAM system for the design and the automatic manufacturing of the iron pattern shaped with 3 - dimensional free curved surface, and to test its applicability to the design and the manufacturing of the rotary blade. The results obtained from the study are as follow; 1. The CAD system which can process graphic procedures from the free curved surface shaped data was developed with personal computer. 2. The CAM main program was developed. This main program could produce CL data from CAD data file by checking the tool interference according to the cutting mode. 3. The sub. program which can simulate the tool trace from the CL data was developed. 4. The post processor for the Deckel FP2NC NC milling machine from CL data file was developed and the sub program could transmit NC program through modem to NC milling machine was developed. 5. The developed CAM system seemed to be applicable to any other system. Because the measuring results of the cross sectional thickness of the plastic model from the manufacturing iron pattern by the system showed that this system could properly check the tool interference. 6. In took 75~90 hours to manufacture two iron patterns of rotary blade. For the sake of convenience in applying to the other systems, this system was developed in BASIC and FORTRAN computer language and minimum portion of machine language as possible.

• Corrosion Science and Technology
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• 제11권3호
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• pp.77-81
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• 2012

Cathodic protection(CP) is widely used as a means of protecting corrosion for not only marine structures like ship hulls and offshore drilling facilities, but also underground structures like buried pipelines and oil storage tanks. The principle of CP is that the anodic dissolution of metal can be protected by supplying electrons to the cathode metal. When unprotected structures are nearby to CP systems, interference problems between unprotected and protected structures may be happened. The stray current interference can accelerate the corrosion of nearby structures. So far many efforts have been made to reduce the interference in the electric railway systems adjacent to the underground metal structures like buried pipelines and gas/oil tanks. During recent few decades the protection technologies against stray current induced corrosion have been significantly improved and a number of techniques have been developed. However, there is very limited information an marine environments. Some complex harbor structures are protected by two cathodic protection systems, i.e. sacrificial anode cathodic protection(SACP) and impressed current cathodic protection(ICCP). In this case, when the protection current from sacrificial anodes returns to the cathode through electrolyte, it passes through nearby other low resistance metal structures. In many cases the stray current of ICCP systems influences the function of SACP. In this study, the risk of stray current from the SACP system to adjacent reinforced concrete structures has been verified through laboratory experiments. Concrete and steel pile structures modeled a part of bridge have been investigated in terms of CP potential and current between the two. The variation of stray current according to the magnitude of ICCP/SACP has been studied to mitigate it and to suggest the proper protection criteria.

• Journal of Communications and Networks
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• 제15권3호
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• pp.312-320
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• 2013

Home evolved Node-B (HeNB), also called a femtocell or a femto base station, is introduced to provide high data rate to indoor users. However, two main problems arise in femtocell networks: (1) Small coverage area of HeNB, which results in limited cell-splitting gain and ping-pong handover (HO) problems and (2) high inter-femtocell interference because HeNBs may be densely deployed in a small region. In this study, an efficient cooperation mechanism called an HeNB-aided virtual-HO (HaVHO) scheme is proposed to expand the coverage area of femtocells and to reduce inter-femtocell interference. The cooperation among neighbor HeNBs is exploited in HaVHO by enabling an HeNB to relay the data of its neighbor HeNB without an HO. The HaVHO procedure is compatible with the existing long term evolution specification, and the information exchange overhead in HaVHO is relatively low. To estimate the signal to interference plus noise ratio improvement, the area average channel state metric is proposed, and the amount of user throughput enhancement by HaVHO is derived. System-level simulation shows that HaVHO has a better performance than the other four schemes, such as lesser radio link failure, lesser ping-pong handover, lesser short-stay handover, and higher user throughput.

• 한국통신학회논문지
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• 제41권2호
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• pp.254-262
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• 2016

차량용 레이더 시스템에 대한 수요가 증가함에 따라서, 상호 간섭 문제는 차량 안전을 보장하기 위해 해결해야 할 결정적인 이슈가 되었다. Frequency modulated continuous wave(FMCW) 레이더의 상호 간섭은 잡음 전력 증가의 형태로 나타나며, 이는 간섭체로 인한 타겟 검출의 실패로 이어진다. 기존의 FMCW 레이더의 주파수 추정을 위하여 사용되는 fast Fourier transform (FFT) 기법은 차량용 레이더 간섭 환경에서는 취약하다. 이러한 단점을 극복하기 위하여, 본 연구에서는 간섭환경에서 사용하기 위한 고해상도 주파수 추정 기법을 제안한다. 제안된 알고리즘의 성능을 입증하기 위하여, 77GHz 전방 감시용FMCW 레이더 시스템을 도입하였다. 제안된 기법은 간섭환경에서도 정확하게 주파수를 추정할 수 있는 multiple signal classification, estimation of signal parameters via rotational invariance techniques과 같은 고해상도 알고리즘을 이용한다. 실험결과로부터 제안된 알고리즘이 기존의 FFT 알고리즘에 비해 신호 대 간섭비 측면에서 14 dB 이상의 마진을 가짐을 확인하였다.

• 한국인터넷방송통신학회논문지
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• 제11권3호
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• pp.107-113
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• 2011

본 논문은 기존 CMA (Constant Modulus Algorithm) 적응 등화기의 성능인 수렴 특성과 잔류 부호간 간섭을 개선하기위하여 Coordinate Reduction을 적용한 CR(Coordinate Reduction)-CMA에대한 관한 것이다. 송신 시스템과 수신 시스템을 연결하는 무선과 유선의 대역 제한 채널에서 발생되는 부호간 간섭에의한 찌그러짐을 줄이기 위하여 등화기가 사용되며, 이의 대표적인 알고리즘으로는 CMA가 널리 알려져 있다. 이와같은 채널을 통하여 대량의 정보를 고속으로 전송하기 위해서는 등화에 필요한 오버헤드를 최소화할 수 있는 빠른 수렴 속도가 요구된다. 논문에서는 등화기 입력단에서 정상 등화 상태에서 오차를 주이는 수신 신호의 Coordinate를 reduce하는 새로운 비용 함수를 도입하였다. 컴퓨터 시뮬레이션을 통하여 제안한 알고리즘이 기존 CMA 보다 빠른 수렴 속도와 적은 잔류 부호간 간섭양을 가짐을 확인할 수 있었다.