• Survey Research
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• v.6 no.2
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• pp.1-32
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• 2005

The accuracy of exit poll mainly depends on the sampling method of voting places. For exit poll, we propose a probability sampling method of selecting voting places as an alternative to the bellwether polling place sampling. Through an empirical study based on the 2004 general election data, the efficiency of the suggested systematic sampling from ordered voting places was evaluated in terms of mean prediction error and it turns out that the proposed sampling method outperformed the bellwether polling places sampling. We also calculated the variance of estimator from the proposed sampling, and considered the sample size problem to guarantee the target precision using the design effect of the proposed sample design.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.5
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• pp.579-586
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• 2005

Recently, it has demanded to the wireless monitoring system in stand-alone PV power generation system. We propose the multiplex monitoring method using RF unit of low-price. RF unit consists of RF modem and communication controller. It is also able to use by repeater to communicate long distance. In this paper. two algorithms were programmed by CCS-C and C++ for multiplex monitoring method, The algorithm of choosing unit was used 'select and poll method' and the course assignment algorithm was embodied with 'Bellman-Ford algorithm'. The good result was achieved in the actual test without communication-data lose. The proposed method will be applied such as monitoring system of PV light on the wayside, monitoring system of unmanned lighthouse, monitoring system of refrigeration container on vessel and so on. It can be applied in the field that various ocean energy system.

• Survey Research
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• v.5 no.2
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• pp.3-30
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• 2004

In Korea, bellwether voting places were selected for exit poll based on the past voting results. Sometimes, voting place stratification were used to improve the exit poll performance. The sampled voting places are intended to mirror the general voters of the entire electoral district. But few studies have been done as to which sampling method works better. This study compared the four sampling methods-bellwether voting place sampling method, random sampling method, stratified bellwether sampling method and systematic sampling from ordered voting places method. When we applied the four methods to the 2004 general election data, the systematic sampling from ordered voting places method outperformed the other three sampling method. Also, we found that the additional sampling of voting places over nine contribute little to the accuracy of the estimation.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1480-1484
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• 2003

This paper presents the design and development of network for housing estate security system. The system can cover up to 961 houses which can be up to 1,200 meters long transfer rate of 9,600 bps. This system uses checking and warning the abnormal situation. More over this system has ability to control switch on/off the electrical equipment in the house via AC line control system. The system consists of 4 parts. The first part is a security system of each house using MCS-51 microcontroller as a central processing unit scan 32 sensors and control 8 appliances and send alarm. The MCS-51 microcontroller received control signal via telephone used DTMF circuit. The second part is distributed two levels master/slave network implementing after RS-485 serial communication standard. The protocol its base on the OSI (Open Systems Interconnection) 7 layers protocol model design focus on speed, reliability and security of data that is transferred. The network security using encrypt by DES algorithm, message sequence, time stamp checking and authentication system when user to access and when connect new device to this system. Flow control in system is Poll/Select and Stop-and-Wait method. The third part is central server that using microcomputer which its main function are storing event data into database and can check history event. The final part is internet system which users can access their own homes via the Internet. This web service is based on a combination of SOAP, HTTP and TCP/IP protocols. Messages are exchanged using XML format [6]. In order to save the number of IP address, the system uses 1 IP address for the whole village in which all homes and appliance in this village are addressed using internal identification numbers. This proposed system gives the data transfer accuracy over 99.8% and maximum polling time is 1,120 ms.