PURPOSES: The objective of this paper is to select the confidential intervals by utilizing the second moment reliability index(Hasofer and Lind; 1974) related to the number of load applications to failure which explains the fatigue failure and rut depth that it indicates the permanent deformation. By using Finite Element Method (FEM) Program, we can easily confirm the rut depth and number of load repetitions without Pavement Design Procedures for generally designing pavement depths. METHODS : In this study, the predictive models for the rut depth and the number of load repetitions to fatigue failure were used for determining the second moment reliability index ( ). From the case study results using KICTPAVE, the results of the rut depth and the number of load repetitions to fatigue failure were deducted by calculating the empirical predictive equations. Also, the confidential intervals for rut depth and number of load repetitions were selected from the results of the predictive models. To determine the second moment reliability index, the spreadsheet method using Excel’s Solver was used. RESULTS : From the case studies about pavement conditions, the results of stress, displacement and strain were different with depth conditions of layers and layer properties. In the clay soil conditions, the values of strain and stresses in the directly loaded sections are relatively greater than other conditions. It indicates that the second moment reliability index is small and confidential intervals for rut depth and the number of load applications are narrow when we apply the clay soil conditions comparing to the applications of other soil conditions. CONCLUSIONS : According to the results of the second moment reliability index and the confidential intervals, the minimum and maximum values of reliability index indicate approximately 1.79 at Case 9 and 2.19 at Case 22. The broadest widths of confidential intervals for rut depth and the number of load repetitions are respectively occurred in Case 9 and Case 7.

PURPOSES: The purpose of this study is to verify the causes of surface scaling at L-shoulder concrete structure. METHODS : From the literature reviews, mechanisms of frost damage were studied and material properties including strength, air void, spacing factor and scaling resistance of L-shoulder concrete structure were analyzed using core specimens taken by real fields. RESULTS : The spacing factor of air void has relatively high correlation of surface conditions : lower spacing factor at good surfacing condition and vice versa. If the compressive strength is high, even thought spacing factor does not reach the threshold value of reasonable durability, the surface scaling resistance shows higher value. Based on these test results, the compressive strength also provide positive effect on the surface scaling resistance. CONCLUSIONS: The main causes of surface scaling of L-shoulder could be summarized as unsuitable aid void amount and poor quality of air void structure. Secondly, although the compressive strength is not the governing factor of durability, but it shows the positive effect on the surface scaling resistance.

An accident related with elevators can cause death or serious injury of operators or passengers. This kind of a fatal accident is due to a failure of elevator. The reduction of failures of elevators is important to reduce the occurrence of elevator accident. Thus, this paper presents the results of analysis for the failure of elevators using the failure data of elevator. The results of analysis can be used to make a maintenance process of elevators.

This paper presents a method for the assesment of thermal and vibration fatigues in integral exhaust manifold/turbine housing system. Most of failures on turbine housing are observed by thermal cyclic loads. In order to predict thermal failures by finite element analysis, we considered the temperature-dependent inelastic materials and transient temperature histories based on the thermal shock test. The results showed that the plastic strains of localized critical regions such as valve seat coincided well with crack locations from an endurance test. But, some failures around neck areas of turbine housing could not predict from thermal stress analysis. These cracks were originated due to the vibration excitations near resonance frequencies within engine operating ranges. The stress results of neck areas, which divided by temperature dependent yield stresses, from harmonic analysis showd a good agreement with experimental results.

This article investigates how failure severity and attribution influence the level of satisfaction in men and women. In an experimental study, we find women’s satisfaction declines more than men’s satisfaction as failure severity increases, but only for consumer-caused failure not for company-caused failure. We also suggest the process underlying these differences by testing the mediation effect. The mediation analysis suggests that women have lower satisfaction than men when the service failure is caused by consumers because as outcome severity increases women have a higher tendency than men to avoid self-blame out of a defensive motivation.

Due to the recent advances in technology, the systems are becoming more demanding in terms of functionality and implementation complexity. Therefore, when system failures are involved in such complex systems, the effects of the related safety issues can also be more serious, thereby causing in the worst case irrecoverable hazards on both human being and properties. This fact can be witnessed in the recent rail systems accidents. In general, the accidents can be attributed to the systematic failure or the random failure. The latter is due to the aging or unsatisfied quality of the parts used in implementation or some unexpected external cause that would otherwise result in accidents whereas the former is usually related to incomplete systems design. As the systems are becoming more complex, so are the systematic failures. The objective of the paper is to study an approach to solving the systematic failure. To do so, at first the system design process is augmented by the functional safety activities that are suggested in the standard IEC 61508. Analyzing the artifacts of the integrated process yields the traceability, which satisfies the requirements for reduction of systematic failure as provided in ISO 26262. In order to reduce systematic failure, the results are utilized in the conceptual design stage of systems development in which systems requirements are generated and functional architecture is developed.

In aerospace industry, MTBF (Mean Time Between Failure) and MFTBF (Mean Flight Time Between Failure) are generally used for reliability analysis. So far, especially to Korean military aircraft, MFTBF of avionic equipments is predicted by MIL-HDBK-217 and MIL-HDBK-338, however, the predicted MFTBF by military standard has a wide discrepancy to that of real-world operation, which leads to overstock and increase operation cost. This study analyzes operational data of avionic equipments. Operational MFTBF, which is calculated from operational data, is compared with predicted MFTBF calculated conventionally by military standard. In addition, failure rate trend is investigated to verify reliability growth in operational data, the investigation shows that failure rate curve from operational data has somewhat pattern with decreased failure rate and constant failure rate.

Many automotive components for power generation such as motors and alternators have been widely using ferrite magnets. To ensure a high level of efficiency could be achieved in an alternator, the assembled magnets must be in good enough durability. Recently, some hairline cracks have been found on the magnet produced by manufacturers in Korea. Thus, there is an increasing concern that some of the magnets produced could cause further problems after being assembled in the alternator. Based on the standard alternator test (RS0008 : 2006), this paper has developed an accelerated failure-free test for magnets in alternator to demonstrate that assembled magnets will meet durability objective specified by the manufacturer. This guarantees the target life of the magnet with 90 percent reliability and 90 percent confidence level (R90C90). Temperature and rotation speed were selected as accelerated stress factors.

Abstract In Korean society, the theme of human errors in railway has been emerging as a critical issue. As far as human error studies are concerned, main trend has been inclined to be led by industrial engineering and systems science. Apart from those trends, this study empirically highlighted the relationship between depression, which has been a frequent research subject in the medical science and psychology, and accidents, with setting depression as an exogenous variable and cognitive failure and mistake as endogenous variables, respectively. Results of hypotheses test for the 204 respondents showed that driver's depression has a significant effect on accidents mediated by cognitive failure and mistake. This findings suggest the need for exploring the diverse latent factors causing human errors and for understanding the complex cognitive process as well as for establishing integrative countermeasures to mitigate human errors.

Thermo-mechanical fatigue cracks on the turbine housing of turbochargers are often observed in currently developed gasoline engines for them to adopt lightness and higher performance levels. Maximum gas temperatures of gasoline engines usually exceed 950℃ under engine test conditions. In order to predict thermo-mechanical failures by simulation method, it is essential to consider temperature-dependent inelastic materials and inhomogeneous temperature distributions undergoing thermal cyclic loads. This paper presented the analytical methods to calculate thermal stresses and plastic strain ranges for the prediction of fatigue failures on the basis of motoring test mode, which is commonly used for accelerated engine endurance test. The analysis results showed that the localized critical regions with large plastic strains coincided well with crack locations from a thermal shock test.

In aerospace industry, MTBF(Mean Time Between Failure) and MFTBF((Mean Flight Time Between Failure) are generally used for reliability analysis. So far, especially to Korean military aircraft, MFTBF of avionic equipments is predicted by MIL-HDBK-217 and MIL-HDBK-338, however, the predicted MFTBF by military standard has a wide discrepancy to that of real-world operation, which leads to overstock and increase operation cost. This study analyzes operational data of avionic equipments. Operational MFTBF, which is calculated from operational data, is compared with predicted MFTBF calculated conventionally by military standard. In addition, failure rate trend is investigated to verify reliability growth in operational data, the investigation shows that failure rate curve from operational data has somewhat pattern with decreased failure rate and constant failure rate.

The purpose of this study is evaluating about the survival rate and causes of failed implants. In this study, the 371 implants was evaluated for the survival rate and failing factors of implant. The survival rate was 96.5%. The failure rate was 3.5%. The average life time of implants was 50 months. The average age of patients treated was 49 years old. In total 371 cases, 13 cases failed implants were removed. The causes of failing implants were poor oral hygiene, excessive occlusal loading, smoking, and etc. The leading causes of failed implants were improper oral hygiene and excessive occlusal loading. In conclusion, I suggest that the periodic plaque control and occlusal force management can improve the survival rate of implants.

This study was carried out to investigate the influence of artificial insemination (AI) failure in 1,619 Korean native cows at Gangwon East area, Korea. The average AI failure rate was 37.02% in the cows and the highest rate was 40.85% in Yangyang-city. Based on the parity in the cows, the AI failure rate was 49.14% and 29.91% in the first and fifth parity cows, respectively. Whereas cows until fifth parity were decreased in AI failure, cows with sixth or more parity showed an upturning AI failure trends with the increasing of parity number. AI failure rate incidence according to the rump fat thickness measured by ultrasound was 28.9% and 33.4% at 5 mm to 10 mm and over than 15 mm, respectively. There was a positive correlation (0.2186) between AI failure rate of mother and that of their offspring cows. That is, offspring of dams with high AI failure rate showed also higher AI failure than those of dams having lower AI failure rate. In conclusion, these results indicate that the AI failure rate was closely related to the rump fat thickness, parity number, and conception rate of mother cows. In addition, these results might strengthen the basis to improve the reproductive performance in Korean native cows.

This study proposes flexural failure design criteria of continuous slabs enhanced by a hybrid system of fiber reinforced polymer (FRP) and ultra high performance concrete (UHPC). The proposed hybrid retrofit system is designed to be placed at the top surface of the slabs for flexural strengthening of the sections in both positive and negative moment zones. The enhancing mechanisms of the proposed system for both positive and negative moment regions are presented. The neutral axis of the enhanced sections in positive moment zone at flexural failure is enforced to be in UHPC overlay for preventing the compression in FRP. From this condition, a relationship between design parameters of FRP and UHPC is established. Although the capacity of the proposed retrofit system to enhance flexural strength and ductility is confirmed through experiments of one-way RC slabs having two continuous spans, the retrofitted slabs failed in shear. To prevent this shear failure, a design criteria of flexural failure is proposed.

이 연구는 1990년부터 2010년까지 20여 년 동안 공시된 34개 광고대행사 들의 감사보고서의 매출액 자료를 Altman의 Z-Score의 수식을 통해 구 해진 Z값을 기준으로 Z값이 1.81보다 작으면 부실기업으로 판정, 2.99보다 크면 건전한 기업으로 판정, 1.81과 2.99사이에 있으면 판정을 유보(회색지대 : Grey Zone)했다. 분석결과, 광고시장 개방초기인 1991년에는 Z값이 0.88이었지만 국내 금융위기 (IMF)의 시작년도인 1997년 Z값 0.72, 1998년 Z값 0.84이었다. 이 시기에는 많 은 광고주들의 부도로 인하여 계열회사 형태였던 인하우스 광고대행사들도 함께 부도가 나거나 다국적 광고대행사들에게 지분양도 등을 통해 기업회생을 모색하던 시기였다. 그 후 1999년 Z값은 1.32, 2000년 1.39로 증가했다. 하지만, 2008년에 는 미국발 서브프라임 모기지 사태로 인해 다국적 광고주들이 경영상의 어려움을 겪게 되면서 그의 광고를 대행해주던 다국적 광고대행사들도 어려움을 겪게 되었 다. 이 시기 국내 광고대행사들은 2008년 Z값은 1.55, 2010년에는 광고시장 개방 이후 가장 높은 Z값 1.62를 기록했다. 한편, Z값이 계산된 34개 기업 중 부실광고대행사로 판정된 비율은 2010년에 62.5%였다. 광고시장 개방초기에 광고대행사들 모두 재무 건정성이 부실했지만 다 국적 광고대행사들이 국내진출을 시작하면서 비율이 1992년에 92.9%로 감소했다. 국내의 금융위기인 IMF가 발생이 되면서 다국적 광고대행사가 국내 광고대행사들 을 인수합병하거나 단독설립 등으로 국내 광고시장에 본격적으로 진출하면서 광고 대행사들의 부실 비중은 1998년에 91.3%로 낮아지기 시작했고 2000년에는 일시 적으로 69.2%로 감소했다가 2002년에 82.8%로 다시 증가세로 돌아 섰다가 2006 년에 57.6%로 떨어졌다. 그 후 리만브라더스 사태로 인한 세계경제의 침체로 다시 2009년에 76.5%를 기록했고 2010년에는 62.5%로 감소했다. 부실 광고대행사의 안정성은 상당히 취약했다. 2010년까지 부실 광고대행사의 평 균 부채비율은 75.65%로 유보기업의 56.07%보다 19.58% 높았다. 부실 광고대행 사의 매출액영업이익률은 3.17%였고 유보 광고대행사는 4.59%였다. 부실 광고대행사의 성장성은 12.04%였고 유보 광고대행사의 성장성은 17.13%로 둘 다 성장성이 높다. 이는 부실 광고대행사나 유보 광고대행사에게 광고물량이 꾸준히 집중화 된다고 할 수 있다. 부실 광고대행사의 자산회전율은 0.71배였고 건전 광고대행사의 자산회전율은 0.78배였다. 자산회전율이 낮다는 것은 부실 광고대행사의 투자를 효율적으로 하 지 못한 부분이 많다는 것을 의미한다.

This study was carried out to investigate artificial insemination (AI) failure status and frozen semen characteristics in Korean proven bulls‘ number (KPN) semen used for AI of Hanwoo cows in Gangwon East region (Gangneung, Donghae, Taebaek, Samcheok, Sokcho, Yangyang, Goseong). Among semen used for AI, AI failure rate showed lowest at KPN506 (27.6%), whereas highest at KPN593 (77.2%). Correlations of AI failure in between Korean proven bulls semen and cows was 0.2941, which means that AI failure rate of Korean proven bulls semen may have respectable effect on reproduction of Hanwoo cow. In addition, present study was conducted to investigate spermatozoal viability rate, ruptured acrosome rate and active mitochondria in frozen Korean proven bulls semen with flow cytometry. The semen of KPN593 showed significantly (p<0.05) higher viability rate in KPN593 (30.49%) than that in KPN637 (37.34%). Furthermore, percentage of ruptured acrosome was lower in KPN637 as 21.37% than in KPN637 (21.37%), but it was not statistically significant. In conclusion, these results indicate that choice of Korean proven bulls semen may correlate positively with conception rate in Hanwoo cow. Therefore, KPN with high AI failure rate might be avoid to increase conception rate and characteristics of frozen semen might be evaluated before its use for AI.