• Journal of KIISE:Computer Systems and Theory
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• v.33 no.9
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• pp.626-633
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• 2006

The wireless sensor networks are sensing, computing and communication infrastructures that allow us to monitor, instrument, observe, and respond to phenomena in the harsh environment. Sensor operating systems that run on tiny sensor nodes are the key to the performance of the distributed computing environment for the wireless sensor networks. Therefore, sensor operating systems should be able to operate efficiently in terms of energy consumption and resource management. In this paper, we present an efficient memory allocation scheme to improve the time and space efficiency of memory management for the sensor operating systems. Our experimental results show that the proposed scheme performs efficiently in both time and space compared with existing memory allocation mechanisms.

• Journal of the Korea Society of Computer and Information
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• v.18 no.10
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• pp.121-128
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• 2013

Existing sensor network studies have only emphasized energy aspects that sensors themselves had. But when an actual sensor network is established, biased use of a specific sensor may cause a partial disconnection of the sensor network. It becomes an disadvantage to fail efficient operation of the sensor network for a long time and energy efficiency of specific sensor energy causes to drop the efficiency of the sensor network. When a sensor network is composed of many clusters or made up of a large network, sensor network's disconnection cannot be avoided because they emphasize sensor's energy efficiency. Therefore, it was tried to lengthen the lifespan of the sensor network by making sensors in the sensor network avoid disconnection through even use of all the sensors composing of the sensor network. This article proposes a protocol to maintain a sensor network for a long time by preventing a sensor networks' disconnection through efficient management of sensor network energy composed of the protocols composing of the sensor network in ubiquitous environments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1559-1569
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• 2014

The purpose of this study is to estimate the degree of cost inefficiency for the urban railway lines of a metropolitan city operated by public institutions in Korea and identify the causes of this inefficiency. To this end, we assume that the urban railway lines produce the output of train-km by putting three production factors of labor, electric power and maintenance and set the variable cost function model with the translog function to make a stochastic cost frontier analysis. Based on estimated result, we conclude that the cost savings for 6 years of all lines are about 6,672 hundred million won and top five lines with high inefficiency are Busan Line1, Daegu Line1, Daejeon Line1, Gwangju Line1, and Daegu Line2. The causes of inefficiency are attributable to labor and maintenance factors. The results of this study can be useful in case of finding the priorities of measures and specific plans for reducing labor and maintenance costs in the urban railway operation.

• Journal of the Korea Institute of Construction Safety
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• v.2 no.2
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• pp.63-69
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• 2019

Building Construction projects are getting higher and larger. Therefore, the use of Tower Crane, which is more productive than any other lifting plan shows a trend of continuous increases. However as equipment for transporting heavy goods, are is too expensive for the monthly rent and used inefficiently for construction. site so it is analyzed that it has problems of reducing productivity and efficiency of lifting work. Inefficient situations are arising like poor communications between operator and worker, occurrence of blind spots, securing the shortest distance of fire during movement after lifting plan, influences of weather, location of materials, movement radius of tower crane by each locations and ever-changing working environments. Therefore, in this study, we first made a list of tower cranes that are inefficiently used at the site, and then we made a checklist. After that, through field visits, we derived checklist for Tower Crane to comprehensive data value.

• Journal of Korean Society of Transportation
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• v.20 no.2
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• pp.59-68
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• 2002

Using 1996 annual observations for 69 bus firms in Seoul, this paper measures firm-level efficiency with data envelopment analysis(DEA) and identifies firm characteristics indicative of differential efficiency in these firms with Tobit regression analysis. The paper then conceptualizes that these firms produce two kinds of output(city/seat bus kilometers or city/seat bus Passengers) using four inputs (labor vehicle, fuel and maintenance). The findings show that, on an average, these firms have only a little input saving potential of 0.9 percent, while not a little output increasing potential of 12.9 percent. On the other hand, it is discovered that these firms operate more efficiently with a lower ratio of maintenance employees to total employees. Furthermore, it appears that both the ratio of seat buses to total buses and average speeds positively affect efficiency in this industry.

• The KIPS Transactions:PartC
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• v.16C no.4
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• pp.495-504
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• 2009

Wireless sensor networks (WSN) consisting of a largenumber of sensors aims to gather data in a variety of environments and is beingused and applied in many different fields. The sensor nodes composing a sensornetwork operate on battery of limited power and as a result, high energyefficiency and long network lifetime are major goals of research in the WSN. Inthis paper we propose a novel cluster-based local multi-hop routing protocolthat enhances the overall energy efficiency and guarantees reliability in thesystem. The proposed protocol minimizes energy consumption for datatransmission among sensor nodes by forming a multi-hop in the cluster.Moreover, through local cluster head rotation scheme, it efficiently manageswaste of energy caused by frequent formation of clusters which was an issue inthe existing methods. Simulation results show that our scheme enhances energyefficiency and ensure longer network time in the sensor network as comparedwith existing schemes such as LEACH, LEACH-C and PEACH.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.255-265
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• 2015

The globalization of the banking industry has highlighted the importance of the internal stability of the banks. For internal stability, the efficiency and productivity of the bank becomes more important, and the bank must be improved. To improve the efficiency and productivity, a methodology for analyzing the current state of the bank's needs was made based on the BCC of DEA and the Malmquist productivity index. This model was developed as a diagnostic method that can analyze the efficiency and productivity of the bank. As a result of the analysis, the position of the bank and the position of the model studied were similar. The BCC-Malmquist model can be applied to the other areas and provide a management strategy.

• The Journal of Society for e-Business Studies
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• v.17 no.4
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• pp.117-140
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• 2012

This study focuses on the use of competitive analysis to identify the effective benchmarking target through consulting techniques to derive improvements. After developed using DEA(Date Envelopment Analysis) the relative efficiency analysis tool for competitor analysis to apply in consulting on-site or within the organization, this study compared the new techniques and the existing techniques. This study was carried out as follows. First, through a review of the literature, consulting competitive analysis techniques and methodologies relative efficiency analysis technique DEA for research scholars examined. Second, DEA-based competitive analysis, multidimensional efficiency analysis is presented. Third, The case study was conducted to determine the suitability and practicality of this analysis method for public company "A".

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.141-148
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• 2015

This paper presents a sun-synchronous orbit design which effectuvely includes the requirements derived from spacecraft to ground station contact and spacecraft to target image accessibility. For this purpose, operation parameters of multiple spacecraft are defined as Contact Overlap, Contact Overlap Gap, Access Overlap, Access Overlap Gap. These parameters are used to form a Figure of Merit that reflects the operational requirements. The Figure of Merit is optimized to increase the efficiency of operating multiple spacecraft in constellation and is used to determine the operational orbit of each spacecraft that constitutes the constellation.

• Journal of Digital Convergence
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• v.14 no.8
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• pp.47-56
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• 2016

This study is on the actual analysis of R&D investment effect through DEA in terms of efficiency resulted from forestry sector climate change response R&D project. Namely, it is clarifying the mechanism of the scientific, technological, social performance result and output, depending on research development cost, employment size as same input. Also, it is in-depth analysis on which performance operates more efficiently in any detailed business. With the study result, we seek political implications to enhance investment effect and core element to consider R&D business project in the future.