• ETRI Journal
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• 제38권5호
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• pp.911-921
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• 2016

This paper presents the description, practical implementation, and stability analysis of a recently proposed, energy-efficient, medium access control protocol for wireless sensor networks, ALOHA-Q, which employs a reinforcement-learning framework as an intelligent transmission strategy. The channel performance is evaluated through a simulation and experiments conducted using a real-world test-bed. The stability of the system against possible changes in the environment and changing channel conditions is studied with a discussion on the resilience level of the system. A Markov model is derived to represent the system behavior and estimate the time in which the system loses its operation. A novel scheme is also proposed to protect the lifetime of the system when the environment and channel conditions do not sufficiently maintain the system operation.

• 한국컴퓨터정보학회논문지
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• 제23권4호
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• pp.1-8
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• 2018

In this paper, we propose an adaptive partition cache replacement policy and evaluate the performance of our scheme using various monitoring ratios to help lifetime extension of non-volatile main memory systems without performance degradation. The proposal combines conventional LRU (Least Recently Used) replacement policy and Early Eviction Zone (E2Z), which considers a dirty bit as well as LRU bits to select a candidate block. In particular, this paper shows the performance of non-volatile memory using various monitoring ratios and determines optimized monitoring ratio and partition size of E2Z for reducing the number of writebacks using cache hit counter logic and hit predictor. In the experiment evaluation, we showed that 1:128 combination provided the best results of writebacks and runtime, in terms of performance and complexity trade-off relation, and our proposal yielded up to 42% reduction of writebacks, compared with others.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권1호
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• pp.25-33
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• 2012

As to display products are made slim, the diameter of aluminum electrolytic capacitor is smaller and the length is longer to be fitted in. These small diameter and long length are pointed as the disadvantageous design factors of the capacitor's life cycle. So, the most electronic makers want to use proven capacitors (or well-known) to secure reliability of the electric products. In this study, we carried out the comparison analysis with two domestic capacitors and one foreign made capacitor. We designated separators, rubber breather and debris as the main factors that effect on the lifetime of capacitors. From the comparison results, we suggested the improvement points of the aluminum electrolytic capacitor.

• 설비공학논문집
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• 제27권10호
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• pp.515-519
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• 2015

Conjugate heat transfer analysis for an ethylene furnace was carried out based on numerical simulation. Detailed distributions of velocity vectors, chemical species, and temperature inside the furnace are presented and discussed. Von Mises stress and heat flux at the tube surface were also evaluated to elucidate mechanisms regarding failure of the tube. Maximum stress was found at the upstream elbow of the tube, which did not coincide with the location of maximum heat flux. This implies that thermal stress at a steady state would not be a dominant component of the stress. Degradation of the material, as well as the system arrangement, should be considered in order to accurately predict the lifetime of the tube material in the furnace.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2079-2081
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• 2005

Electrical treeing occurrence is caused by some defect in solid insulator. Those are accompany the PD(partial discharge) occurrence. And lifetime of the insulator is affected by PD. So, detection of electrical treeing is important thing as this view. Especially, detection of the end treeing is more important and have meaning for industrial engineering because concerned with maintenance and replacement of equipment. In this paper, evaluation of treeing process were studied and PCA(principle component analysis)-LDA(linear discriminant analysis) as classification method were used. The result is present the good recognition.

• Nuclear Engineering and Technology
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• 제34권2호
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• pp.176-185
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• 2002

A 4-bundle shift refuelling method of CANDU6 F/H (Fuel Handling) System is analyzed to assess the operational flexibility and capacity of F/H system. The current 8-bundle shift refuelling scheme requires to refuel eight fuel bundles from a single fuel channel, and to refuel 14 fuel channels in a week on average assuming that the reactor is in a steady state. The analysis showed that the 4-bundle shift refuelling method increases F/M (Fuelling Machine) duty cycle and operator load. However, the fuellin’g method change from the 8- to 4-bundle shift refuelling ill not require additional team of operators. A marginal increase in the maintenance cost may be resulted in by the change of fuelling method and the increase of fatigue usage factors requires some components to be replaced during the FM lifetime.

• Childhood Kidney Diseases
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• 제27권2호
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• pp.127-132
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• 2023

Cystinuria, a genetically inherited disorder, is a rare cause of kidney stones. It is characterized by impaired transport of cystine and amino acids in the proximal renal tubule and the small intestine. Most patients develop cystine stones throughout their lifetime. Recurrent renal stones need to be extracted by repeated urologic interventions. Treatment options of cystinuria for preventing stone recurrence are limited and poorly tolerated. In this study, we report a pediatric case of cystinuria with a heterozygous SLC3A1 mutation diagnosed by stone analysis, measurement of urine cystine excretion, and genetic analysis. There were recurrent renal stones despite repetitive shock wave lithotripsy and retrograde intrarenal surgery. However, the rate of stone formation seemed to be slower after D-penicillamine was added into adequate hydration and urinary alkalinization.

• 한국기계가공학회지
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• 제13권5호
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• pp.107-115
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• 2014

Highly functional mill turrets have been developed and continuously improved to shorten the manufacturing time and enable multiple uses. Among these, a mill turret with B-axis rotary table was developed. The B-axis rotary table should be evaluated for structural integrity. Moreover, its worm and worm gear for transmitting power should be able to endure fatigue damage. Therefore, this article presents a structural analysis of this type of B-axis rotary table and confirms its static stability by comparing the stress results to the allowable stress levels. Next, the dynamic stability of the rotary table was investigated via a mode analysis and a harmonic analysis in a range determined by the results of a modal analysis. Finally, a worm gear set, the main part that drives the rotary table, is analyzed for fatigue and to estimate its lifetime. The results of the fatigue analysis allowed a prediction of the life of the worm gear set. The analytical results show that the B-axis rotary table has good structural integrity.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권3호
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• pp.260-270
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• 2018

Purpose: The purpose of this study is to evaluate the life of the capsule, which is a core part of the heat storage cooling system. This paper will develop a life test mode that can reproduce environment conditions through the analysis of capsule shrinkage and expansion characteristics. Methods: In order to determine the life test mode of the capsule, this paper analyzed the case of field failures and analyzed the deformation characteristics according to the pressure fluctuation of the capsule. The method to find out whether the field failure and deformation analysis results are consistent is the testing with the construction of the repetition pressure test equipment and the thermal cycle test to reproduce the freezing and thawing characteristics. Results: In this study, failure mode analysis and analysis of freezing and thawing characteristics regarding to the capsule positions were completed. Based on this test & analysis results, this paper have been able to determine the main parameters for determining the life test mode, the freezing and thawing time. Conclusion: Determining the lifetime mode of the capsule can be used to improve the life and performance of the thermal storage system.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.581-588
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• 2013

This paper deals with the Safety Analysis for $CANDU^{(R)}$ 6 nuclear reactors as affected by main Heat Transport System (HTS) aging. Operational and aging related changes of the HTS throughout its lifetime may lead to restrictions in certain safety system settings and hence some restriction in performance under certain conditions. A step in confirming safe reactor operation is the tracking of relevant data and their corresponding interpretation by the use of appropriate thermal-hydraulic analytic models. Safety analyses ranging from the assessment of safety limits associated with the prevention of intermittent fuel sheath dryout for a slow Loss of Regulation (LOR) analysis and fission gas release after a fuel failure are summarized. Specifically for fission gas release, the thermal-hydraulic analysis for a fresh core and an 11 Effective Full Power Years (EFPY) aged core was summarized, leading to the most severe stagnation break sizes for the inlet feeder break and the channel failure time. Associated coolant conditions provide the input data for fuel analyses. Based on the thermal-hydraulic data, the fission product inventory under normal operating conditions may be calculated for both fresh and aged cores, and the fission gas release may be evaluated during the transient. This analysis plays a major role in determining possible radiation doses to the public after postulated accidents have occurred.