• Journal of Internet Computing and Services
• /
• v.16 no.3
• /
• pp.1-11
• /
• 2015

WBAN(Wireless Body Area Network) operating around the human body aims at medical and non-medical service at the same time. and it is the short-range communication technology requiring low-power, various data rate and high reliability. Various studies is performing for IEEE 802.15.4, because IEEE 802.15.4 can provide high compatibility for operate WBAN among communication standard satisfiable these requirements. Meanwhile, in the case of coexisting many IEEE 802.15.4-based WBAN, signal interference and collision are the main cause that is decreasing data reliability. but IEEE 802.15.4 Standard does not consider about coexistence of many networks. so it needs improvement. In this paper, To solve about this problem, identify coexistence problem of IEEE 802.15.4-based WBAN by preliminary experiments. and propose a scheme to mitigate the reliability decrease at multiple coexistence WBAN. The proposed scheme can be classified in two steps. The first step is avoidance to collision on the CFP through improving data transmission. The second step is mitigation collision through converting channel access method. Proposed scheme is verified the performance by performing comparison experiment with Standard-based WBAN.

• Journal of Society of Preventive Korean Medicine
• /
• v.9 no.1
• /
• pp.17-36
• /
• 2005

The objective of this study is to present basic data for producing tools to measure Yangseng of the elderly aged older than 65 by reassessing the validity and reliability of such tools already developed. In the present study, total 855 subjects were divided into 4 groups and given 31 question for the ultimate factor analysis of each item. The results cloud be summarized as follows: 1. In case of 'don't have sex in drunken state or right after dinner'(the 31st item of sex live yangseng). factor loading came out proportionally in 3 factors such as factor 4=0.358, factor 5=0.389 and factor 6=0.386. As they all failed to reach the general standard of 0.5 or more and even the minimum standard of 0.4 or more, the 31st item was deleted from the questionnaires. 2. From the factor analysis after exclusion of the 31st item, factor loading of the 25th item of sleep yangseng 'go to bed and get up regularly' appeared to be proportional in 2 factor(factor 4=0.393 and factor 7=0.373). Since it was shown that the 25th item could not be classified into a category but interacted with others in common and didn't satisfy the minimum standard of 0.4, it was deleted form the questionnaires, too. 3. From the factor analysis conducted after excluding the item numbers 31 and 25, factor loading of the 12th item of diet yangseng 'do not eat much' turned out to be relatively high with such values as factor 5=0.518 and factor 3=0.453. As it was, however, tied up with the factor of exercise yangseng, it was also deleted. In conclusion, 28 items after excluding the item numbers 12, 25 and 31 form 4 group showed the same results as divided into 8 factor with high grade of reliability and validity, evidencing the assumption that they can be employed practically to measure yangseng of the elderly aged 65 and oder.

• Proceedings of the Korean Reliability Society Conference
• /
• 2001.06a
• /
• pp.269-269
• /
• 2001

Maintainability refers to the ease with which maintenance work can be done. It involves the process of ensuring that products can be easily and safely maintained and that the maintenance support requirement is minimized. When a product has a reasonably long life, the cost of operation and support during that life can greatly exceed the initial capital cost. The value to the customer of optimizing maintainability should be evident. Some effort and expense applied to achieving a product which can be easily and cheaply maintained will make very significant savings in the life cycle costs. In this paper, the International Standard IEC 60300-3-10, which is the application guide for maintainability, is considered. This standard can be used to implement a maintainability program covering the initiation, development and in-service phases of a product. It provides guidance on how the maintenance aspects of the tasks should be considered in order to achieve optimum maintainability. The elements of a maintainability program, which are maintenance policy and concept, maintainability studies, project management, design for maintainability, analysis and prediction methods, maintenance verification and validation, analysis of life cycle cost, maintenance support planning, and collection and analysis of maintenance data, are fully discussed in this paper.

• Journal of Sensor Science and Technology
• /
• v.25 no.4
• /
• pp.291-296
• /
• 2016

The ideal chemical sensor must show the similar result under the same condition for accurate measurement of gases regardless of time. However, the actual responses of chemical sensors have been shown the lacks of repeatability and reproducibility because of the drift which has been caused by aging and pollution of the sensor and the environment change such as temperature and humidity. If the problems are not properly taken into considerations, the stability and reliability of the system using chemical sensors would be decreased. In this paper, we analyzed the sensor's drift and applied the three different compensation methods(DWT( Discrete Wavelets Transform), Baseline Manipulation, Internal Normalization) for reducing the effects of the drift in order to improve the stability and the reliability of short term of the chemical sensors. And in order to compare the results of the methods, the standard deviation was used as a criterion. The sensor drift was analyzed by a trend line graph. We applied the three methods to the successive data measured for three days and compared the results. As a result of comparison, the standard deviation of DWT showed lowest value. (Before compensation: 7.1219, DWT: 1.3644, Baseline Manipulation: 2.5209, Internal Normalization: 3.1425).

• Computers and Concrete
• /
• v.26 no.5
• /
• pp.385-395
• /
• 2020

The influence of combination of nano silica and silica fume, as partial cement replacement materials, on the properties of concrete has been studied through the measurement of compressive strength. The compressive strength of concrete in terms of mean, standard deviation and with-in-test coefficient of variation related to the variation in the nominated parameters have also been developed. The compressive strength data developed experimentally has been analyzed using normal-probability distribution and partial safety factors of composite concretes have been evaluated by using first order second moment approach with Hasofer Lind's method. The use of Nano silica and silica fume in concrete decreases the partial safety factor of concrete i.e., increase the reliability of concrete. The experimental results show that the properties of concrete having nano silica and silica fume in combination were better than that of a plain concrete. The SEM test results showing the level of Ca(OH)₂ in plain concrete and consumption level Ca(OH)₂ of concrete containing nano silica & silica fume have also been presented.

• Proceedings of the Korea Contents Association Conference
• /
• 2005.11a
• /
• pp.53-59
• /
• 2005

Reference Standard Data(RSD), which is a very high data of reliability, an authentic data of quality, can be used repetitively in industry, science and technology field. The more RSD is produced and used in various field, the more the level of detail of industry goods and reliability of material rise. It is also the nationally important information resource that improve the technology level of nation and international competitiveness. Before constructing RSD, this paper is used of the source data that recommend RSD's development direction and higher required RSD after we investigate what kind of RSD domestic users require in some field.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.54 no.10
• /
• pp.480-486
• /
• 2005

This paper proposes a method to consider an aging failure probability and survival probability of power system components, though only aging failure probability has been considered in existing mean life calculation. The estimates of the mean and its standard deviation is calculated by using Weibull distribution, and each estimated parameters is obtained from Data Analytic Method (Type H Censoring). The parameter estimation using Data Analytic Method is simpler and faster than the traditional calculation method using gradient descent algorithm. This paper shows calculation procedure of the mean life and its standard deviation by the proposed method and illustrates that the estimated results are close enough to real historical data of combustion turbine generating units in Korean systems. Also, this paper shows the calculation procedures of a probabilistic failure prediction through a stochastic data analysis. Consequently, the proposed methods would be likely to permit that the new deregulated environment forces utilities to reduce overall costs while maintaining an are-related reliability index.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.24 no.1
• /
• pp.90-98
• /
• 2016

Currently government certified test method for an automobile remanufactured products is insufficient. Thus many automotive parts in the remanufacturing market are lacking proper evaluation criteria and production of defective products are causing customer dissatisfaction. In this paper a power steering oil pump, which requires stringent manufacturing standards, is studied by the failure mode and effect analysis approach. The research suggested that the test criteria such as discharge flow characteristic test, tightness test, pulley run-out test, pressure switch operation test, low temperature test and rotation pressure durability test should be performed to evaluate the reliability of remanufactured power steering oil pumps. As a result of tests, the performance of remanufactured power steering oil pump satisfied the evaluation criteria of pressure switch operation test and low temperature test. However, the remanufactured power steering oil pump failed to satisfy the evaluation criteria on discharge performance test, tightness test and pulley run-out test. These performance evaluation tests proved the necessity of standard process for the remanufactured power steering oil pump.

• Journal of Korean Society for Quality Management
• /
• v.49 no.3
• /
• pp.255-268
• /
• 2021

Purpose: We sought to understand why a high-speed rotating projectile featuring a fuze-and-body assembly sometimes exhibited airburst, and we intended to improve the flight stability by eliminating airburst. Methods: We performed characteristic factor analysis, structural mechanics modeling, and dynamic modeling and simulation; and we scheduled firing tests to discover the cause of airburst. We used a step-by-step procedure to analyze the reliability function for selecting the bonding force standard that prevents airburst. Results: The 00MM high-speed rotating projectile features a fuze bonded to a body assembly; the bonding sometimes can break on firing. The resulting contact force, vibration and roll damping during flight generated yaw. Flight became unstable; fuze operation triggered an airburst. Our reliability test improved the bonding force standard (the force was increased). When the bonding force was at least the minimum required, a firing test revealed that airburst/flight instability disappeared. Conclusion: Analysis and identification of the causes of flight instability and airburst render military training safer and enhance combat power. Ammunition must perform as designed. Our method can be used to set standards that improve the performances of similar types of ammunition.

• Land and Housing Review
• /
• v.12 no.3
• /
• pp.87-96
• /
• 2021

Korea has begun to use the Helical pile prevalent in Europe. Korea hasn't still set up the standard design criteria on Helical pile due to the lack of relevant researches. In this regard, this study carried out static and dynamic load tests on Helical pile and then performed reliability analysis including the previous research data. The results present that Road bridge design standard design criteia for pre-boring pile with regard to Modified Davisson method showed good reliability and consistency because Resistance bias factor of this design criteria approached '1.0' and Design C.O.V. showed 'low' level.