• Communications of the Korean Mathematical Society
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• v.13 no.2
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• pp.393-403
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• 1998

We consider $M_1,M_2/M/1$ retrial queues with two classes of customers in which the service rates depend on the total number or the customers served since the beginning of the current busy period. In the case that arriving customers are bloced due to the channel being busy, the class 1 customers are queued in the priority group and are served as soon as the channel is free, whereas the class 2 customers enter the retrical group in order to try service again after a random amount of time. For the first $N(N \geq 1)$ exceptional services model which is a special case of our model, we derive the joint generating function of the numbers of customers in the two groups. When N = 1 i.e., the first exceptional service model, we obtain the joint generating function explicitly and if the arrival rate of class 2 customers is 0, we show that the results for our model coincide with known results for the M/M/1 queues with smart machine.

• Journal of Biosystems Engineering
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• v.43 no.3
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• pp.161-172
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• 2018

Purpose: During tillage operations, the selection of a working machine (tool) depends on the soil conditions as well as the type of tillage operation to be performed. The goal of this research was to ascertain the effects of varying working machine parameters of a compact disc harrow on tillage operations under various soil moisture content (SMC) conditions. Methods: The working machine parameters were the disc spacing and machine speed. The tillage parameters under investigation were the soil inversion ratio (SIR), tillage cutting depth (TCD), and soil clod breakage ratio (SCB). To determine the SIR, the areas of the white regions before and after tillage were obtained. The ratio of the difference of the areas of the white regions before and after tillage to the area of the white regions before tillage was considered as the SIR. The SCB was obtained as the ratio of the weight of soil clods after sieving with a mesh size of <0.02 m to the total weight of the soil clods before sieving. The soil TCD was measured using a tape measure at random points after the tillage operation. The resulting data were statistically analyzed in a one-way analysis of variance. Results: The highest soil inversion was achieved when the machine speed was 0.2 m/s with the disc spaced at 0.2 m in the 16.5% SMC. At a 0.4-m/s machine speed and 0.3-m disc spacing the highest soil breakage was achieved in the 26.5% SMC. The highest TCD was achieved at a 0.2-m/s machine speed and 0.2-m disc spacing in the 16.5% SMC. Conclusions: It was concluded that varying the working machine parameters, such as the disc spacing and machine speed, could significantly affect the soil inversion and soil clod breakage; however, it had no significant impact on the TCD.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1152-1153
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• 2011

본 시스템은 개방형 M2M(Machine to Machine Communication: 사물 지능 통신) 기반의 개방형 API 중에서 컴퓨터 지원 협력 작업 환경 API 에서의 웹 동기화 시스템에 대한 설계를 제안한다. M2M 기반의 웹 동기화 시스템이 잘 지원되면 웹 기반 원격 제어, 결함 진단 등 개발 시 비 효율성을 제거할 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1154-1155
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• 2011

본 연구에서는 M2M(Machine to machine: 사물 지능 통신) 기반의 URL 동기화 기능을 갖는 멀티미디어 공동작업 환경에서 웹 관련 응용 소프트웨어와 미디어 등의 프로세스(process) 요소들에 대한 오류를 미리 감지하고 오류를 공유하여 웹 멀티미디어 세션에 참여한 참여자 간의 효율적인 의사소통과 상호 협력 환경의 향상을 제공한다. M2M 기반의 오류 동기화 시스템을 이용하여 신속하고 정확하게 오류를 전달하여서 복구하는데 빠르게 대처할 수 있는 시스템을 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.687-708
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• 2017

The machine-to-machine (M2M) communication is featured by tremendous number of devices, small data transmission, and large uplink to downlink traffic ratio. The massive access requests generated by M2M devices would result in the current medium access control (MAC) protocol in LTE/LTE-A networks suffering from physical random access channel (PRACH) overload, high signaling overhead, and resource underutilization. As such, fairness should be carefully considered when M2M traffic coexists with human-to-human (H2H) traffic. To tackle these problems, we propose an adaptive Slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) hybrid protocol. In particular, the proposed hybrid protocol divides the reserved uplink resource blocks (RBs) in a transmission cycle into the S-ALOHA part for M2M traffic with small-size packets and the TDMA part for H2H traffic with large-size packets. Adaptive resource allocation and access class barring (ACB) are exploited and optimized to maximize the channel utility with fairness constraint. Moreover, an upper performance bound for the proposed hybrid protocol is provided by performing the system equilibrium analysis. Simulation results demonstrate that, compared with pure S-ALOHA and pure TDMA protocol under a target fairness constraint of 0.9, our proposed hybrid protocol can improve the capacity by at least 9.44% when ${\lambda}_1:{\lambda}_2=1:1$and by at least 20.53% when ${\lambda}_1:{\lambda}_2=10:1$, where ${\lambda}_1,{\lambda}_2$ are traffic arrival rates of M2M and H2H traffic, respectively.

• Journal of applied mathematics & informatics
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• v.18 no.1_2
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• pp.431-439
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• 2005

The aim of this paper is to derive the analytical solution of the queue: $M/E_{r}/1/k/N$ for machine interference system with balking and reneging considering the discipline FIFO. Some measures of effectiveness and some special cases are obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.86-89
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• 2005

Design and estimation of a spindle system which was composed of grinding spindle and regulating spindle for the centerless grinding of ferrule was performed and prototypes of each spindle were manufactured. Loop stiffness of the spindle system was 130 N/${\mu}m$. Although the value was lower than the target value of 150 N/${\mu}m$, as there included 20% of the safety factor, it was enough to machine the ferrule. Rotational accuracies of each spindle were about 0.2${\mu}m$ at the primary speed of 2,300 rpm(grinding spindle) and 300 rpm(regulating spindle). Temperature rises at the same speed were about $4.4\;\~\;4.7^{\circ}C$ in the case of grinding spindle and $1.8^{\circ}C$in the case of regulating spindle, which were well agreed with the designed value. From these results, it was estimated that the prototype of spindle system had a enough performances for the centerless grinding machine to machine the ferrule.

• Journal of Digital Convergence
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• v.13 no.4
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• pp.205-210
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• 2015

The auto industry has significantly evolved to the extent that much attention is paid to M2M (Machine-to-Machine) communication. In M2M communication which was first used in meteorology, environment, logistics, national defense, agriculture and stockbreeding, devices automatically communicate and operate in accordance with varying situations. M2M system is applied to vehicles, specifically to device-to-device communication inside cars, vehicle-to-vehicle communication, communication between vehicles and traffic facilities and that between vehicles and surroundings. However, communication systems are characterized by potential intruders' attacks in transmission sections, which may cause serious safety problems if vehicles' operating system, control system and engine control parts are attacked. Thus, device-to-device secure communication has been actively researched. With a view to secure communication between vehicular devices, the present study drew on hash functions and complex mathematical formulae to design a protocol, which was then tested with Casper/FDR, a tool for formal verification of protocols. In brief, the proposed protocol proved to operate safely against a range of attacks and be effective in practical application.

• Journal of Advanced Navigation Technology
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• v.18 no.1
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• pp.74-77
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• 2014

This paper suggested an error control for multi-channel running on machine to machine environment. This system is suitable for recovering software fault for multimedia CSCW(Computer Supported Cooperative Works) based on machine to machine environment. It is necessary for the system to be protected by reactivity of media service instance instead of breaking process of session. This paper explains a performance analysis of an error recovery system of M2M based computing collaboration environment using rule-based DEVS modeling and simulation techniques.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.585-590
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• 2011

In the past few years, M2M (Machine-to-Machine) applications have become a hot topic in the wireless industry. While M2M applications can be used for many purposes (smart homes, smart metering/electricity meter reading, fleet management, mobile workforce, automobile insurance, vending machines, etc), and in many sectors (healthcare, agriculture, commercial, industrial, retail, utility, etc.), smart metering applications or smart grids present the biggest growth potential in the M2M market today. M2M platform is the future ubiquitous network technologies which provide the integrated service with the networks and devices. The promising technologies to tackle these problems are the Semantic technologies, for interoperability, and the Agent technologies for management of complex systems. In this paper the information communication technique based on the disaster prevention system's for the M2M, concepts and its requirement technology and application are studied.