• 대한전자공학회논문지TC
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• 제44권1호
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• pp.146-154
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• 2007

본 논문에서는 무선 센서 네트워크에서 지연시간에 민감한 데이터를 실시간으로 전달하는 기법을 제안하였다. 실시간 전송을 위한 기존의 방식들은 단순히 전달 지연이 짧은 경로 혹은 홉 수가 작은 경로를 선택한다. 하지만, 이러한 방식들은 링크 에러율을 고려하지 않았으므로, 전송 오류가 발생하는 경우에는 재전송으로 인하여 실시간 전송을 보장하기 어렵다. 따라서, 본 논문에서는 링크 에러율을 고려하여 실시간 전송 경로를 선정하는 알고리즘을 제안하였다. 제안하는 기법은 이웃 노드들 간의 링크 에러율에 기반하여 홉 간의 전송 지연시간을 추정함으로써 종단 간 기대되는 지연시간을 계산한다. 소스 노드는 가장 짧은 전달 지연시간을 가진 경로를 실시간 경로로 선택하고 데이터를 전송한다. 링크의 에러율에 따른 다양한 실험을 통하여 제안 방식이 데이터 전달 속도를 향상시키고 지연 지터를 감소시킨다는 사실을 확인하였다. 또한, 전송 오류와 재전송의 상대적 인 감소로 인하여 에너지 소비가 줄어들고 네트워크 수명이 연장된다는 사실을 알 수 있었다.

• 대한전자공학회논문지SD
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• 제48권2호
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• pp.7-13
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• 2011

본 논문에서는 디지털 위상고정루프(All-digital PLL)를 구성하는 핵심 블록인 시간-디지털 변환기(Time-to-Digital Converter)를 제안하고 구현하였다. 본 연구에서는 게이티드 링 오실레이터 시간-디지털 변환기(GRO-TDC)의 기본 구조에 버니어 지연단(VDL)을 이용하여 다중 위상을 얻음으로써 보다 높은 해상도를 얻을 수 있는 구조를 제안하였다. 게이티드 링 오실레이터(GRO)는 총 7개의 지연셀을 사용하였고, 버니어 지연단(VDL) 3단을 이용하여 총 21개의 다중 위상을 사용하여 시간-디지털 변환기(TDC)를 설계하였다. 제안한 회로는 $0.13{\mu}m$ 1P-6M CMOS 공정을 사용하여 설계 및 구현하였다. 측정결과, 제안한 시간-디지털 변환기(TDC)의 최대 입력 주파수는 100MHz이고, 해상도는 26ps로 측정되었으며, 출력은 8-비트이며, 검출이 가능한 최대 위상 차이는 5ns의 위상 차이까지 검출이 가능하였다. 전력 소비는 측정된 Enable 신호의 크기에 따라 최소 8.4mW에서 최대 12.7mW로 측정되었다.

• 한국건설관리학회논문집
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• 제5권1호
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• pp.133-139
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• 2004

최근 도심지 고층건축공사가 증가하면서 건설자원의 효율적인 관리가 중요시되고 있으나 현재 국내 건설현장에서 건설자재의 공급에 대한 많은 문제점을 가지고 있다. 공정과 연계되지 못한 자재의 조달 및 양중은 현장 내 재고 증가 및 작업지연을 유발하며, 복잡한 정보전달 체계는 관련 작업의 의사결정의 지연의 원인으로 작용하여 결과적으로 공사기간에 절대적인 영향을 미치고 있다. 따라서 공정진행을 고려한 조달 및 양중작업에서 각 공사담당자간의 효율적인 정보전달 체계의 구축은 효과적인 공사수행을 위해 필수적이다. 본 연구에서는 사례조사를 통해 건설자재의 조달 및 양중작업의 문제점을 분석하여 가치흐름분석을 통해 구체적인 낭비요소를 추출한 뒤, 공사참여자간의 의사소통 체계를 구축 및 양중계획 업무흐름 개선방안을 제시하였다. 개선방안은 web을 기반으로 한 조달 및 양중시스템의 전반적인 체계로서 활용될 것이다.

• 한국자동차공학회논문집
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• 제21권4호
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• pp.89-95
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• 2013

In this work, the evaluation of swirl nozzle injector performance was conducted by investigating effective area ($A_{eff}$), injection mass ($m_{inj}$), injection rate ($Q_{inj}$), and injection delay ($t_{delay}$) under various test conditions. To achieve these, fuel injection analysis system which was composed of fuel supply system, injection system, and control system was installed. At the same time, the swirl nozzle that had 12 orifice hole with $120^{\circ}$ injection angle was used in this work. It was revealed that the difference of injection mass ($m_{inj}$) between base and swirl nozzle injector increased as the injection pressure ($P_{inj}$) and energizing duration ($t_{eng}$) decreased under the same test conditions. The maximum injection rate ($Q_{inj}$) of swirl nozzle injector was higher than base nozzle injector about 2~5%. The injection performance of swirl nozzle was better than base nozzle at low injection pressure ($P_{inj}$) and short energizing duration ($t_{eng}$) conditions.

• Journal of Communications and Networks
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• 제6권3호
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• pp.216-225
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• 2004

In a cellular network, if there are too many data users in a cell, data may suffer long delay, and system's quality-of-service (QoS) will degrade. Some traditional schemes such as dynamic channel-allocation scheme (DCA) will assign more channels to hot (or overloaded) cells through a central control system (CC) and the throughput increase will be upper bounded by the number of new channels assigned to the cell. In mobile-assisted data forwarding (MADF), we add an ad-hoc overlay to the fixed cellular infrastructure and special channels-called forwarding channels- are used to connect mobile units in a hot cell and its surrounding cold cells without going through the hot cell's base station. Thus, mobile units in a hot cell can forward data to other cold cells to achieve load balancing. Most of the forwarding-channel management work in MADF is done by mobile units themselves in order to relieve the load from the CC. The traffic increase in a certain cell will not be upper bounded by the number of forwarding channels. It can be more if the users in hot cell are significantly far away from one another and these users can use the same forwarding channels to forward data to different cold neighboring cells without interference. We find that, in a system using MADF, under a certain delay requirement, the throughput in a certain cell or for the whole net-work can be greatly improved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4883-4901
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• 2016

Energy efficiency in Wireless Sensor Networks (WSNs) is very appealing research area due to serious constrains on resources like storage, processing, and communication power of the sensor nodes. Due to limited capabilities of sensing nodes, such networks are composed of a large number of nodes. The higher number of nodes increases the overall performance in data collection from environment and transmission of packets among nodes. In such networks the nodes sense data and ultimately forward the information to a Base Station (BS). The main issues in WSNs revolve around energy consumption and delay in relaying of data. A lot of research work has been published in this area of achieving energy efficiency in the network. Various techniques have been proposed to divide such networks; like grid division of network, group based division, clustering, making logical layers of network, variable size clusters or groups and so on. In this paper a new technique of group based WSNs is proposed by using some features from recent published protocols i.e. "Energy-Efficient Multi-level and Distance Aware Clustering (EEMDC)" and "Energy-Efficient Multi-level and Distance Aware Clustering (EEUC)". The proposed work is not only energy-efficient but also minimizes the delay in relaying of data from the sensor nodes to BS. Simulation results show, that it outperforms LEACH protocol by 38%, EEMDC by 10% and EEUC by 13%.

• 품질경영학회지
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• 제49권3호
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• pp.245-254
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• 2021

Purpose: In order to accurately reach an underwater projectile to a target point, reliable INS and accurate arrangement of INS between master and slave INS is paramount. Unlike terrestrial and aerial environments, underwater projectile will operates in a restricted environment where location information cannot be received or sent through satellites. In this report, we review the factors affecting the transfer alignment of master and slave INS, as well as how to improve the positional error between INS through improved transfer alignment algorithms. Methods: In this work, we propose an improvement algorithm and verify it through simulation and driving test. The simulation confirmed the difference in the transfer alignment azimuth by fitting the MINS and SINS indoors, displacement in posture, and the process of transfer alignment between MINS and SINS through a driving test to confirm algorithm can improve the arrangement. Results: According to this study, reason for the error in the transfer alignment between MINS/SINS is the factors of the system where movements such as roll, pitch, yaw are not inter locked in real time due to the delay in transmit/receive system. And confirm that the improved algorithm has a desirable effect on accuracy. Conclusion: Through this work, it is possible to identify ways to improve the accuracy of underwater projectiles to reach their target points under various underwater environments and launch condition.

• 산업경영시스템학회지
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• 제3권3호
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• pp.35-39
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• 1980

Although the product line produces a large volume of goods in a relatively short time, once the product line is established there are numerous problems that arise in connection with this product line. One of these problems is the problem of balancing operations or stations in terms of equal times and in terms of the times required to meet the desered rate of production. The objective of line balancing is minimizing the idle time on the line for all combinations of work stations subject to certain restrictions. In general, there are two types of line-balancing situations : (1) assembly line balancing and (2) fabrication line balancing. Two approaches to the assembly line balancing problem have been used. The first assumes a filed cycle time and find the optimum number of work stations. The second approach to the assembly line balancing problem assumes the number of work stations to be fixed and systematically coverages on a solution which minimizes the total delay time by minimizing the cycle time. Here the cycle time is determined by the longest station time. In this paper, by using the second approach method, a general mathematical model, problem solutions, and computer program for the assembly line balancing problem is presented. Data used is obtained from the company which has been confronted with many problems arising in connection with their assembly line.

• 한국BIM학회 논문집
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• 제11권3호
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• pp.34-44
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• 2021

This study quantitatively analyzes the work performance of the structural safety diagnosis team that diagnoses pipe racks. To this end, a method for evaluating the performance of the structural safety diagnosis team using the queuing model was proposed. For verification, the case of applying the existing method and the method of introducing a 3D laser scanner for one site was used. The period, number of people, and initial investment cost of each project were collected through interviews with case project experts. As a result of analyzing the performance of the structural safety diagnosis team using the queuing model, it was possible to confirm the probability of delay in the work of each project and the amount of delayed work. Through this, the cost (standby cost) when the project was delayed was analyzed. Finally, economic analysis was conducted in consideration of the waiting cost, labor cost, and initial investment cost. The results of this study can be used to decide whether to introduce 3D laser scanners.

• Journal of applied mathematics & informatics
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• 제41권1호
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• pp.95-105
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• 2023

To make the network energy efficient and to protect the network from malignant user's energy efficient grid based secret key sharing scheme is proposed. The cost function is evaluated to select the optimal nodes for carrying out the data transaction process. The network is split into equal number of grids and each grid is placed with certain number of nodes. The node cost function is estimated for all the nodes present in the network. Once the optimal energy proficient nodes are selected then the data transaction process is carried out in a secured way using malicious nodes filtration process. Therefore, the message is transmitted in a secret sharing method to the end user and this process makes the network more efficient. The proposed work is evaluated in network simulated and the performance of the work are analysed in terms of energy, delay, packet delivery ratio, and false detection ratio. From the result, we observed that the work outperforms the other works and achieves better energy and reduced packet rate.