• Journal of Information Processing Systems
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• v.8 no.2
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• pp.263-278
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• 2012

The data grid provides geographically distributed resources for large-scale applications. It generates a large set of data. The replication of this data in several sites of the grid is an effective solution for achieving good performance. In this paper we propose an approach of dynamic replication in a hierarchical grid that takes into account crash failures in the system. The replication decision is taken based on two parameters: the availability and popularity of the data. The administrator requires a minimum rate of availability for each piece of data according to its access history in previous periods, but this availability may increase if the demand is high on this data. We also proposed a strategy to keep the desired availability respected even in case of a failure or rarity (no-popularity) of the data. The simulation results show the effectiveness of our replication strategy in terms of response time, the unavailability of requests, and availability.

• International journal of advanced smart convergence
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• v.12 no.3
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• pp.221-232
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• 2023

Recently, due to the expansion of the logistics industry, demand for logistics automation equipment is increasing. The modern logistics industry is a high-tech industry that combines various technologies. In general, as various technologies are grafted, the complexity of the system increases, and the occurrence rate of defects and failures also increases. As such, it is time for a predictive maintenance model specialized for logistics automation equipment. In this paper, in order to secure the operational reliability of the ICT/Cold-Chain Unmanned Storage, a predictive maintenance system was implemented based on the LSTM model. In this paper, a server for data management, such as collection and monitoring, and an analysis server that notifies the monitoring server through data-based failure and defect analysis are separately distinguished. The predictive maintenance platform presented in this paper works by collecting data and receiving data based on RabbitMQ, loading data in an InMemory method using Redis, and managing snapshot data DB in real time. The predictive maintenance platform can contribute to securing reliability by identifying potential failures and defects that may occur in the operation of the ICT/Cold-Chain Unmanned Storage in the future.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.2
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• pp.154-161
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• 2010

The conning display which is located in the ship bridge shows the various important information such as ship position, ship speed, track data, rate of turn, thruster rpm so on, and is one of the IBSs(Integrated Bridge Systems). In this study, the survey was conducted for ten officers to find the importance and using frequency of the information which were displayed in the conning display. The results showed that the information of drift speed, ship speed, wind direction and wind force, rate of turn, sea water depth, ship position, heading, thrust rpm, alarm, rudder command and angle got high scores and it meant that these information were very important and high frequency of use during the navigation. The optimized contents arrangement in conning display was suggested based on importance and using frequency of information. The experiment using eye-tracking system was conducted to compare the performance time and error rate of nine different scenarios for suggested arrangement display and three other existing displays. The results showed that the suggested arrangement was the best in performance time and error rate. The scenario concerning the direction and speed of wind showed faster performance time and lower error rate than other scenarios. The movement of subject's eye tended to search from the center and to avoid the comer, called 'the comer effect.' It is expected that the results of this study could help for the bridge staff to grasp the sailing information easily and to cope with the given situations promptly.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.3
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• pp.96-102
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• 2000

High speed machining aims to raise the productivity and efficiency by making more precise and higher value-added products than any other machining method by means of the high speediness of spindle and feed drive system. The purpose of this study is to investigate the effects of the run-out of endmill on the dimension precision of workpiece and to obtain the fundamental data on high speed machining which is available by machining the side of Al-alloy with solid carbide endmills in high speed machining center and by measuring dimensions and surface roughness. From the results of experimentation following are obtained ; if spindle speed is ultra high in conditions that radial depth of cut and feed per tooth are very small highly precise and accurate products are to be made efficiently with high feed rate. and so we can raise productivity.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.5
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• pp.185-192
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• 2011

In this paper, we simulate and analyze performance of iterative coding scheme, double binary turbo code, for high speed power line communication (PLC) systems. PLC system has hostile environment for high speed data transmission, so error correction method is necessary to compensate effects of PLC channel. We employ the PLC model proposed by M. Zimmerman and Middleton Class A interference model, and system performance is evaluated in terms of bit error rate (BER). From the simulation results, we confirm double binary turbo code provides considerable coding gains to PLC system and BER performance is significantly improved as the number of iteration increase. It is also confirmed that BER performance increases as code rate is lager, while it decreases as the code rate is smaller.

• Health Policy and Management
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• v.32 no.1
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• pp.73-93
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• 2022

Background: Appropriate physician workforce projection through reasonable discussions and decisions with a broad view on supply and demand of the workforce, thus, is very important for high-quality healthcare services. The study expects to provide preliminary research data on the workforce diagnosis standard model for Korean physician workforce policy decision through more flexible and objective physician workforce projection in reflection of diverse changes in healthcare policy and sociodemographic environments. Methods: A low flow rate through the causal map was developed, and an objective workforce demand projection from 2019 to 2040 was conducted. In addition, projections by scenarios under various situations were conducted with the low flow rate developed in the study. Lastly, the demand projection of the physician workforce by region of 17 cities and provinces was conducted. Results: First, demand of physicians in 2019 was 110,665, 113,450 in 2020, 129,496 in 2025, 146,837 in 2030, 163,719 in 2035, and 179,288 in 2040. Second, the scenario for the retirement of baby boomers led to a decrease in the growth rate due to time delay. Third, Seoul and Gyeonggi-do account for a high percentage of demand, a very high upward trend was identified in Gyeonggi-do, and as a result, the projection showed that the demand of the physician workforce in Gyeonggi-do would worsen over time. Conclusion: This study is meaningful in that rational and collective physician workforce supply and demand and its imbalance in workforce distribution were verified through various projections by scenarios and regions of Korea with System Dynamics.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.185-192
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• 2022

Fisheries is known as a high-risk industry in Korea, and various efforts have been made to reduce occupational accidents. Trap fisheries represent crustacean production, accounting for 4.7% of total fisheries production and 10.7% of its production value, which is classified as a relatively high-risk industry. With the disaster insurance payment data of the National Federation of Fisheries Cooperatives (NFFC) from 2016 to 2020, the accident rate of the entire fishery, the accident rate of trap fisheries, and the type of disasters in the past five years were analyzed. As a result, the average fishery accident rate for the past five years was 5.31%, but it was high at 6.15% for coastal trap fisheries and 5.59% for offshore trap fisheries. Slips and trips, struck by objects and contact with machinery were the most common types of the accident according to the characteristics of the work, and hand injuries were analyzed the most. Additional efforts, including education for accident prevention, development of personal protective equipment and improvement of the working environment, are needed to prevent accidents caused by repeated types of disasters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6C
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• pp.561-570
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• 2009

Ultra-wideband communication systems based on impulse radio have merits that are possible for the high data rate transmission, high resolution ranging are positioning system. Conventionally, in order to accomplish these features, the high-speed ADC (Analog to Digital Convertor) is necessary to apply radio determination system operating in time domain. However, considering low rate - wireless personal area network (LR-WPAN) aims to low-cost hardware implementation, the expensive ADC converting GHz sampling per second is not appropriate. So, this paper introduces a low complex AR (Auto Regressive) model based non-coherent ranging scheme operating in frequency domain with using low-speed ADC utilizing analog Voltage Control Oscillator (VCO) mode for the frequency domain transformation. To verify the superiority of the proposed ranging and location algorithm working in frequency domain, the suggested IEEE 802.15.4a TG channel model is used to exploit affirmative features of the proposed algorithm with conducting the simulation results.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.2
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• pp.171-177
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• 2004

Many instrumentations have been used to acquire the performance data of military systems fer many years. But they could not satisfy environmental specifications(vibration, shock, temperature) and processing speed to apply for the performance test of military systems because of having developed as common vehicles/fixed installation equipments. Thus a new rugged embedded measurement system is required to process large data in high processing speed(Maximum sample rate:1.25Mhz/ch) with rugged environmental specifications. We have developed embedded measurement systems by using PXI(PCI extension for Instrumentation)bus interface composed of a stand alone controller and versatile data acquisition boards(analog, digital, vision, temperature and small signal conditioner) on PC-based environment to solve these problems. Operation programs have been developed using Lab_View and the performances have been validated experimentally.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.1
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• pp.48-55
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• 2017

This paper proposes a new link structure that transmits power, clock, and data through a single optical fiber for a future automotive network. A pulse-position modulation (PPM) technique is adopted to guarantee a DC-balanced signal for robust power transmission regardless of transmitted data pattern. Further, circuit implementations and theoretical analyses for the proposed PPM transceiver are described in this paper. A prototype transceiver fabricated in 65-nm CMOS technology, is used to verify the PPM signaling part of the proposed system. The prototype achieves a $10^{-13}$ bit-error rate and 0.188-UI high frequency jitter tolerance while consuming 14 mW at 800 Mb/s.