• International Journal of Highway Engineering
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• v.10 no.2
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• pp.115-124
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• 2008

This Study was investigated in main breakage types of 50 interlocking block pavements in apartment houses and evaluated on their performance. According to performance evaluation, maintenance control index of 9 aged interlocking block pavements ranged 7.9 to 8.9. These values meant that the condition of interlocking block pavements were still good. Therefore, it was concluded that the 10-year cycle of the block replacement recommended by Ministry of Construction & Transportation is necessary to reappraise. To objectively evaluate the performance of interlocking block pavements, this study presented the criteria of maintenance control by combining two maintenance control standards suggested by Ministry of Construction & Transportation and the Japan Interlocking Block Pavement Engineering Association. Also, this study suggested that the domestic standard is necessary to include durability standards and quality standards of joint filling materials and bedding sand layer for increasing expectation life and reducing maintenance costs of interlocking block pavements.

• The Journal of the Korea Contents Association
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• v.17 no.1
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• pp.50-57
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• 2017

This study investigated the causes and problems of train operation impediments through the statistics analysis of 8 years'internal data of Daejeon Metropolitan Express Transit. By evaluating the risks regarding the system, equipment, and parts of high risk group, this study measured the Risk Index Severity, and applied the $5{\times}5$ Risk Assessment Matrix which is a method of risk management to calculate the scale of risk to analyze the safety level and allowance range. As a result, the car sector, the most serious risk, followed by machinery and equipment sector showed that the inherent risk. In particular, the door broken and the door rail signaling and control devices due to defects of the vehicle is high, but also the severity, and frequency are showing very frequent additional potential accidents. PSD also had defects in the machinery sector appeared to be the most dangerous of the PSD poor safety gates, it was found that the glass also involve the risk of mishandling and breakage of the PSD. This study intended to contribute to the transportation benefits through the safety and stable operation of Metropolitan Express Transit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.740-753
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• 2008

The conventional Split Hopkinson Pressure Bar (C-SHPB) technique with aluminum pressure bars to achieve a closer impedance match between the pressure bars and the specimen materials such as hot temperature degraded POM (Poly Oxy Methylene) and PP (Poly Propylene) to obtain more distinguishable experimental signals is used to obtain a dynamic behavior of material deformation under a high strain rate loading condition. An experimental modification with Pulse shaper is introduced to reduce the nonequilibrium on the dynamic material response during a short test period to increase the rise time of the incident pulse for two polymeric materials. For the dynamic stress strain curve obtained from SHPB experiment under high strain rate, the Johnson-Cook model is applied as a constitutive equation, and we verify the applicability of this constitutive equation to the probabilistic reliability estimation method. The methodology to estimate the reliability using the probabilistic method such as the FORM and the SORM has been proposed, after compose the limit state function using Johnson-Cook model. It is found that the failure probability estimated by using the SORM is more reliable than those of the FORM, and the failure probability increases with the increase of applied stress. Moreover, it is noted that the parameters of Johnson-Cook model such as A and n, and applied stress affect the failure probability more than the other random variables according to the sensitivity analysis.

• International Journal of Highway Engineering
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• v.5 no.3 s.17
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• pp.21-29
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• 2003

The management of existing airfield pavement information has currently become difficult and the maintenance cost has increased over time due to the long-term performance. It is needed to develop the method for effective budget allocation and systematic airfield pavement management services. The objectives of this paper are to introduce Micro PAVER, one of the popular pavement management systems, into our management system and customize Micro PAVER based on our environment and pavement management level. This study focused on the analysis on logics and structures of Micro PAVER and customization of important parts in the program using the existing pavement evaluation data and survey method. Customized items selected in this study included the pavement deterioration prediction models, critical PCI, maintenance cost by PCI, maintenance or rehabilitation method and unit cost, and PCI rank.

• Explosives and Blasting
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• v.37 no.4
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• pp.10-16
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• 2019

Information on overpressure, positive phase duration, and impulse are required to assess the effects of shock waves or pressure waves on the structure. In this study, the overpressure and positive phase duration were determined by applying the Multi-Energy Method, which is found to be effective in analyzing the explosion of vapor clouds. Based on the total heat of combustion estimated in the cyclohexane vapor cloud explosion in the Nypro Ltd(UK), overpressure and positive phase duration at the distance of 40, 80, 120, 160, 200, 240, 280, 320, 360(m) from the source of explosion were evaluated. Overpressure was shown to decrease exponentially and positive phase duration increased almost linearly with distance. A probit function was used to assess the probability of damages for the structures at each distance using the overpressure and impact obtained at the above mentioned distances. The Analyses of probability of damages have shown that there is a high probability of collapse at distances within 120m, major damage to structures within 240m, and minor damage and breakage of window panes of structures occur over the entire distances.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.21-27
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• 2019

Composite motor cases fabricated by the filament winding method are structurally weak in the dome when they are required to withstand the internal pressure of the combustion gas. In this study, a finite element analysis is conducted to compare the burst pressure of a composite dome according to the variation of the pressure distribution ratio(PDR). The performance of the composite motor case was compared quantitatively by calculating the stress on the inner and outer dome surfaces and metal boss volume. As a result, the critical point of the failure mode was observed at a PDR between 2.5 and 3.0. A design at a PDR of 2.5­-3.5 can reduce the weight of metal boss without fluctuation in the burst pressure of the combustion motor case. Moreover as the design reference value changes according to the dome shape and opening size, further analysis and testing are necessary.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6A
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• pp.1023-1032
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• 2006

In this paper, a new method for the bridge maintenance is proposed to overcome the limit of the existing methods and to implement the preventive bridge maintenance system. The proposed method can establish the lifetime optimum maintenance strategy of the deteriorating bridges considering the life-cycle performance as well as the life-cycle cost. The lifetime performance of the deteriorating bridges is evaluated by the safety index based on the structural reliability and the condition index detailing the condition state. The life-cycle cost is estimated by considering not only the direct maintenance cost but also the user and failure cost. The genetic algorithm is applied to generate a set of maintenance scenarios which is the multi-objective combinatorial optimization problem related to the life-cycle cost and performance. The study examined the proposed method by establishing a maintenance strategy for the existing bridge and its advantages. The result shows that the proposed method can be effectively applied to deciding the bridge maintenance strategy.

• International Journal of Highway Engineering
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• v.5 no.1 s.15
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• pp.11-18
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• 2003

Road roughness, as the key factor influencing not only drivers' ride quality and safety but also pavement deterioration, is one of the most important pavement performance indicator to be evaluated by users' subjective assessment. For this reason, a specific number of the pavement roughness has been adopted to monitor the condition of a road for pavement management systems and to evaluate the quality of newly constructed sections, however, none of the unified methodology was internationally accepted. In Korea highway network, road roughness has been used mainly to evaluate newly placed pavement by using 7.6m CP (California Profile meter) to calculate PrI (Profile Index). But this instrument is manually operated to measure road profiles by traffic closure and their interpretation depends on personal bias. Therefore, problems arisen from the manually operated instrument will be overcome by using the APL (Longitudinal Profile Analyzer) which can be operated in the speed of 80km per hour. A study was conducted to correlate the relation from both concrete and asphalt pavement between IRI (measured by APL) and PrI (measured by 7.6m CP). Test results showed that there was a good correlation between IRI and PrI.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.401-404
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• 2008

Bridges are exposed to very severe environment and experience, as service life increased, elevated traffic load and traffic flow, in addition to natural disasters. In comparing to other road structures, bridges may cause more significant damage, such as human-involved accidents, to the society in the event of collapse. A certain level of service shall be necessarily secured to assure the minimum safety of users. The cost for manage and preserve bridges will increase gradually and more restrictions will be loaded to efficiently distribute the limited resources, such as monetary budget and human resource etc. In order to enhance performance and serviceability of bridges with the limited resource, asset management technique has been applied into the bridge management system, which capitalizes the road infrastructures including bridges and assess them in accordance with the government finance report. In the application of asset management, there must be a tool for assess the performance of bridges and this study introduces the basic information on the definition and role of performance measures for asset management for bridges.

• Journal of Oral Medicine and Pain
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• v.33 no.4
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• pp.305-316
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• 2008

The mandibular advancement device(MAD) has been used to help manage snoring and obstructive sleep apnea. The aims of this study were to specify the demographic and clinical characteristics of the patients receiving long-term treatment with MAD and to quantify the compliance with and side effects of the use of the device. Of 103 patients who were treated with MAD for at least one full year after delivery date, 49 were able to be contacted with telephone and complete follow-up questionnaires were obtainable. They were telephoned to determine whether they were still using the device. If not, they were asked when and why they stopped using it. Patients were also asked how much effectiveness of the MAD in decreasing snoring and how much they and their bed-partners were satisfied with the MAD therapy. The initial respiratory disturbance indices and pre-treatment snoring frequency and intensity were obtained from the medical records of initial visit. All the data were compared between users and nonusers. The results were as follows: 1. Of 49 patients 25 are still using the device, but 24 stopped using it. Among nonusers nobody stopped wearing the device within first 1 month, but 37.5% of nonusers stopped wearing it in the following 6 months, and another 4.2% before the end of the first year. 2. The one-year compliance of the MAD therapy was 79.59%. 3. There were no significant differences in mean age, mean body mass index, and gender distribution between users group and nonusers group. 4. There was no significant difference in mean respiratory disturbance index at initial visit between users group and nonusers group. 5. There was no significant difference in pre-treatment snoring frequency and intensity between users group and nonusers group. 6. The degree of decrease in snoring with use of MAD was significantly higher in the users when compared to nonusers. 7. Patient's overall satisfaction with treatment outcome was significantly higher in the users when compared to nonusers. 8. Bed partner's satisfaction with treatment outcome tended to be higher in the users when compared to nonusers. 9. The most frequent reasons why patients discontinued wearing the MAD were: jaw pain(25%), dental pain(20.83%), broken appliance(20.83%), hassle using(16.67%), lost weight(8.3%), dental work(8.3%), no or little effect(4.17%), sleep disturbance(4.27).