• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.9-24
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• 1995

In this paper, we proposed and analysed two kinds of priority control mechanism to archive the cell loss rate requirement and the delay requirement of each class. The service classes of our concern are the high time priority class(class 1) and the high loss priority class(class 2). Two kinds of priority control mechanism is divided by the method of storing the arriving class 2 cell in buffer on case of buffer full. The first one is the method which discarding the arriving class 2 cell, the second one is the mothod which storing the arriving class 2 cell on behalf of pushing out the class 1 cell in buffer. In the proposed priority schemes, one cell of the class 1 is transmitted whenever the maximum K cells of the class 2 is transmitted on case of transmitting the class 1 cell and the class 2 cell sequentially. In this paper, we analysed the cell loss rate and the mean cell delay for each class of the proposed priority scheme by using the Markov chain. The analytical results show that the characteristic of the mean cell delay becomes better for the class 1 cell and that of the cell loss rate becomes better for the class 2 cell by selecting properly the cell transfer ratio according to the condition of input traffic.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.6
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• pp.72-84
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• 1988

Engine performance is one of the main objectives specified at the beginning of a new engine design project. The cycle simulation for SI engine is based on the zero-dimensional gas exchange model and a heat release expression by Viebe. This program also requires minimum input data and takes only a short time to run. Heat transfer from cylinder transfer formula. The flow coefficient (effective area) is calculated from valve lift using the standard flow coefficient curve and engine friction is calculated from the Millington and Hartles' engine friction formula. The chemical species considered in burned gas are 6 species CO, CO, H$_{2}$, H$_{2}$O, $O_{2}$, N$_{2}$ and the cylinder pressure, homogeneous cylinder temperature, gas composition and burned fraction are calculated at each crank angle through the cycle. To check the validity and accuracy, experimental study was done with 3 engines for measuring cylinder pressure, indicated mean effective pressure, brake mean effective pressure and air flow rate, etc. Despite its simple assumptions, cycle simulation showes excellent breathing and performance correlation when compared with data of tested engines, and have been proved useful in engine design.

• 대한공업교육학회지
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• v.33 no.1
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• pp.265-281
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• 2008

The objective of this study is to show practice example let student experience about concurrent servers based multi-processes and multi-thread among the principles of data communication in ICT(information and communications technology). For this, we first implement multi-process server(fork server) and multi-thread server(thread server), and multi-thread client(thread client), Secondly, for experimental environment, we developed small ethernet networks and measure data transfer time with relation to the number of users. Experimental results show that mean transfer time of thread server is less than that of fork server by 20~61 % on average. Furthermore, it is found that the difference of data transfer time between fork server and thread server is proportional to that of the number of users. Main reason of performance difference dues to the difference between process forking time and thread creation time. We can also find that context switching for process and thread affects the load of web server. Our presentation and experimental results can be applied to used as the educational practice materials with which student can experience data communication principles.

• Journal of Embryo Transfer
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• v.14 no.2
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• pp.83-88
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• 1999

This study was undertaken with three objectives : to determine the optimal time of blood collection for plasma urea nitrogen(PUN) analysis, to examine the frequency distribution of PUN levels in recipient herd and to relate concentration of PUN to conception rate in Hanwoo recipients. The relationship between PUN level and time postfeeding was examined for 5 individual cows. Mean concentration of PUN rose for 4hrs postfeeding and decreased to PUN level before feeding at 10hrs postfeeding. And then, the blood for PUN analysis was collected at the time before feeding in next experiments. The ratio of cows with PUN concentration of < 12, 12∼18 and 18mg/dl were 50.6, 39.9 and 9.5% in 163 recipients, individually. The pregnancy rate of cows with PUN concentration 12∼16 mg/dl (63.3%) was higher than that of cows with PUN concnetration < 12 mg/dl (46.7%) or > 16mg/dl (42.9%). There results suggest that the PUN test may be beneficial for management of recipient herd in effects to maintain or improve reproductive efficiency.

• Archives of Reconstructive Microsurgery
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• v.14 no.1
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• pp.37-41
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• 2005

Purpose: The purpose of this study was to evaluate the effectiveness of internal transport using Ilizarov apparatus with free flap surgery for infected tibial nonunion. Materials and Methods: We reviewed 8 patients of infected tibial nonunion treated with internal transport using Ilizarov apparatus and free flap surgery. Seven of eight patients were available for at least 1 year follow-up. All patients were male. The mean age at the time of the surgery was All fractures were Gustilo's type III B open fracture. The mean length of the bone defect was 8.5 cm. All used flaps for covering the soft tissue defect were free rectus abdominis muscle flap. We evaluated bone and functional results with use of the Paley and Catagni's classification. And we classified the complication with use of the Paley's classification. Results: Acceptable length and solid union of bone was achieved in all cases. The mean size of the bone length was 7.2 cm. The mean healing index was 69.5 days/cm. All but one case needed bone graft at docking site. All flaps were survived. There was no recurrence of infection. According to Paley and Catagni's classification, all cases showed excellent or good results. Complications were pin tract infection in 3 cases, persistent pain in 2 cases and limitation of joint motion in 2 cases. Conclusion: Simultaneous free-tissue transfer and Ilizarov distraction osteogenesis was thought to be an attractive treatment modality for infected nonunion of the tibia.

• Structural Engineering and Mechanics
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• v.26 no.6
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• pp.635-650
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• 2007

In this paper, the equivalent exciting force caused by electric excitation is derived. By dividing load and displacement vectors into mean values and time-varying ones, the dynamic equations of the system are transformed into linear ones for time-varying portion of the displacements. The analytical equations of the forced time responses of the drive system to electric excitations are obtained. Using the Laplace transformation, the transfer function of the drive system is obtained. These equations are used to analyze the time and frequency responses of the drive system to the electric excitation. It is known that electric excitation can cause forced responses of the drive system, the total dynamic responses are decided by three phase exciting voltages, exciting frequency and natural frequencies of the drive system, and the drive parameters have obvious influence on the time and frequency responses.

• Journal of Mechanical Science and Technology
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• v.15 no.3
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• pp.357-365
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• 2001

The aim of this paper is to perform the experiment and the numerical simulation for investigating the heat transfer in a regenerator system with ceramic honeycomb and to suggest a useful correlation for optimization of the regenerator system. For achieving this, the effects of some parameters were investigated, e. g., switching time, cell size and length of honeycomb on the mean temperature efficiency. The measured temperatures by R-type thermocouples were compared with the predictions by means of the commercial package, STAR-CD. A useful correlation for thermal efficiency was newly proposed as a function of the normalized switching time, defined in terms of switching time, cell size and length of honeycomb. The results showed that the thermal efficiency is above 90% and the normalized heat exchange rate is higher than 80% when the normalized switching time is less than 1000.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1984.10a
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• pp.43-47
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• 1984

This paper describes the mean time delay and its variance before transition from search to lock mode by means of signal flow graph and its transfer function. A relation between hit probability and search stage number is presented with the comparison of the open loop and closed loop. From these results optimum transition probability which we must hold can be obtained.

• Asian-Australasian Journal of Animal Sciences
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• v.8 no.1
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• pp.51-58
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• 1995

To examine whether colostral growth factors are transferred to the general circulation, concentrations of plasma cortisol, insulin, prolactin, growth hormone, insulin-like growth factors(IGFs) -I and -II, IGF-binding proteins(IGFBPs) and total protein were measured in newborn calves fed colostrums, milk of milk replacer before and after feeding at 12 h intervals during the first two days after birth. Plasma protein concentrations increased with time after than in milk- or milk replacer-fed calves. The mean protein concentration was greater in colostrum-fed than in milk- or milk replacer-fed calves. Plasma cortisol levels transiently declined after each feeding regardless of the type of diet, while insulin levels tended to increase. Mean concentrations of these hormones did not differ between dietary groups, nor did they change with time after birth. Plasma concentrations of prolactin and growth hormone did not differ between dietary groups and also did not change with time after birth or after feeding. Concentrations of IGF-I and IGF-II transiently increased at the second feeding period, but these, as well as plasma IGFBP profiles, were not different between groups or before and after feeding. Results did not indicate significant transfer of colostral growth factors across the newborn ruminant small intestine.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.4
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• pp.63-68
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• 2006

This research presents the reliability analysis of the pneumatic actuator within the tape feeder that is used to transfer the correct force to linked parts during l.0E+7 cycles. First, the degradation analysis for thrust and air leakage is executed to obtain the failure data of a product based on its performance over time. Second, once the parameters has been calculated using the weibull 2-parameter distribution and MLE(Maximum Likelihood Estimation), information related to life such as reliability, failure rate, probability density function is estimated. Finally, MTTF(Mean Time To Failure) and $B_{10}$ life of actuators are calculated. MTTF means the mean life at the confidence level and $B_{10}$ life refers to the time by which 10% of the product would fail. In this study, failure causes and solutions are examined using the reliability analysis.