• Journal of Construction Engineering and Project Management
• /
• 제7권4호
• /
• pp.1-12
• /
• 2017

India has accorded a high priority to road infrastructure development through Public-Private Partnership (PPP) and it has set a high target for investment inflows. Yet, it is widely held that road/highway infrastructure has not been developing at required pace and that the road infrastructure projects under PPP have been suffering from several hurdles and delays, thereby affecting project success/failure. This paper is an attempt to analyze the critical success/failure factors of road infrastructure projects under PPP in India. A questionnaire survey was conducted among a sample of the stakeholders of road infrastructure projects to identify the critical success/failure factors during all four major project stages using different approaches. Initially, the critical factors were identified through ranking based on the average/mean score. Later, the conventional RII score was used to identify the critical success/failure factors. Finally, the critical success/failure factors were also identified based on the stakeholder-wise ranking of the factors and their convergence. The assessment revealed that there was a greater convergence across the different methods and also that there was greater consensus among project stakeholder on the critical success/failure factors of road PPP projects.

• International Journal of Reliability and Applications
• /
• 제11권2호
• /
• pp.123-138
• /
• 2010

This paper investigates a mathematical model of a system composed of two non-identical unit parallel system with common-cause failure, critical human error, non-critical human error, preventive maintenance and two type of repair, i.e. cheaper and costlier. This system goes for preventive maintenance at random epochs. We assume that the failure, repair and maintenance times are independent random variables. The failure rates, repair rates and preventive maintenance rate are constant for each unit. The system is analyzed by using the graphical evaluation and review technique (GERT) to obtain various related measures and we study the effect of the preventive maintenance preventive maintenance on the system performance. Certain important results have been derived as special cases. The plots for the mean time to system failure and the steady-state availability A(${\infty}$) of the system are drawn for different parametric values.

• Structural Engineering and Mechanics
• /
• 제10권1호
• /
• pp.67-79
• /
• 2000

Critical loads and load-carrying capacities for steel scaffolds used as shoring systems were compared using computational and experimental methods in Part I of this paper. In that paper, a simple 2-D model was established for use in evaluating the structural behavior of scaffold-shoring systems. This 2-D model was derived using an incremental finite element analysis (FEA) of a typical complete scaffold-shoring system. Although the simplified model is only two-dimensional, it predicts the critical loads and failure modes of the complete system. The objective of this paper is to present a closed-form solution to the 2-D model. To simplify the analysis, a simpler model was first established to replace the 2-D model. Then, a closed-form solution for the critical loads and failure modes based on this simplified model were derived using a bifurcation (eigenvalue) approach to the elastic-buckling problem. In this closed-form equation, the critical loads are shown to be function of the number of stories, material properties, and section properties of the scaffolds. The critical loads and failure modes obtained from the analytical (closed-form) solution were compared with the results from the 2-D model. The comparisons show that the critical loads from the analytical solution (simplified model) closely match the results from the more complex model, and that the predicted failure modes are nearly identical.

• 한국IT서비스학회지
• /
• 제4권1호
• /
• pp.1-13
• /
• 2005

Many buying and selling companies have participated in B2B electronic commerce in order to boost sales and cut down purchase prices respectively. There are some studies on buying and selling companies performances of using B2B e-marketplaces which provide electronic B2B transaction services such as finding transaction partners, providing on-line transaction process like auctioneering, etc. This study investigates the critical failure factors against B2B e-marketplace in other words B2B market-maker or B2B intermediary. We proposed 4 hypotheses asserting that 4 critical failure factors make reverse effects on B2B intermediary performances. We adopt the Balanced Score Card (BSC) framework to evaluate B2B intermediary performance. Data were collected from 46 respondents of B2B intermediaries in Korea. Analyses showed that traditional off-line B2B practices like refunding to buyer or transactions without legal documents and low quality of product information and catalog are critical failure factors against B2B intermediary performance.

• 한국산학기술학회논문지
• /
• 제10권10호
• /
• pp.2810-2818
• /
• 2009

본 연구는 화강풍화토로 구성된 절토사면에서 얕은파괴의 특성을 규명하고자 우리나라의 강우특성에 따른 한계투수계수를 산정하고, 국내에 분포하는 화강풍화토의 대표적 물성을 기준으로 절토사면의 파괴면까지의 수평거리, 사면의 경사각, 사면높이 그리고 강우로 인한 포화깊이 등에 따른 안정해석을 수행하여 그 결과를 분석하였다. 한계투수계수를 분석한 결과 국내의 지역별 강우특성을 고려한 최대 한계투수계수가 $7.16{\times}10^{-4}cm/sec$의 값으로 나타났다. 최대 한계투수계수 이하의 값을 갖는 국내의 화강풍화토로 구성된 절토사면에서 한계강우강도 이하의 강우가 최소 강우지속시간보다 오랫동안 지속될 때에는 포화깊이에 따른 얕은파괴의 검토가 고려되어져야 할 것으로 판단되었다. 또한, 가상파괴면이 발생하는 수평거리, 포화깊이, 강도정수 변화에 따른 사면안전율의 변화관계를 통해 절토사면의 얕은파괴 특성을 파악 할 수 있었다.

• Nuclear Engineering and Technology
• /
• 제39권2호
• /
• pp.129-132
• /
• 2007

It is generally known that software reliability growth models such as the Jelinski-Moranda model and the Goel-Okumoto's non-homogeneous Poisson process (NHPP) model cannot be applied to safety-critical software due to a lack of software failure data. In this paper, by applying two of the most widely known software reliability growth models to sample software failure data, we demonstrate the possibility of using the software reliability growth models to prove the high reliability of safety-critical software. The high sensitivity of a piece of software's reliability to software failure data, as well as a lack of sufficient software failure data, is also identified as a possible limitation when applying the software reliability growth models to safety-critical software.

• Structural Monitoring and Maintenance
• /
• 제8권4호
• /
• pp.345-360
• /
• 2021

This paper presents an analytical approach to calculate the buckling load of the cylindrical ring structures subjected to both hydrostatic and hydrodynamic pressures. Based on the conservative law of energy and Timoshenko beam theory, a theoretical formula, which can be used to evaluate the critical pressure of buckling, is first derived for the simplified cylindrical ring structures. It is assumed that the hydrodynamic pressure can be treated as an equivalent hydrostatic pressure as a cosine function along the perimeter while the thickness ratio is limited to 0.2. Note that this paper limits the deformed shape of the cylindrical ring structures to an elliptical shape. The proposed analytical solutions are then compared with the numerical simulations. The critical pressure is evaluated in this study considering two possible failure modes: ultimate failure and buckling failure. The results show that the proposed analytical solutions can correctly predict the critical pressure for both failure modes. However, it is not recommended to be used when the hydrostatic pressure is low or medium (less than 80% of the critical pressure) as the analytical solutions underestimate the critical pressure especially when the ultimate failure mode occurs. This implies that the proposed solutions can still be used properly when the subsea vehicles are located in the deep parts of the ocean where the hydrostatic pressure is high. The finding will further help improve the geometric design of subsea vehicles against both hydrostatic and hydrodynamic pressures to enhance its strength and stability when it moves underwater. It will also help to control the speed of the subsea vehicles especially they move close to the sea bottom to prevent a catastrophic failure.

• Tuberculosis and Respiratory Diseases
• /
• 제82권3호
• /
• pp.242-250
• /
• 2019

Background: Data on noninvasive ventilation (NIV) use in intensive care units (ICUs) are very limited in South Korea. Methods: A prospective observational study was performed in 20 ICUs of university-affiliated hospitals from June 2017 to February 2018. Adult patients (age>18 years) who were admitted to the ICU and received NIV treatment for acute respiratory failure were included. Results: A total of 156 patients treated with NIV were enrolled (mean age, $71.9{\pm}11.6years$). The most common indications for NIV were acute hypercapnic respiratory failure (AHRF, n=89) and post-extubation respiratory failure (n=44). The main device for NIV was an invasive mechanical ventilator with an NIV module (61.5%), and the majority of patients (87.2%) used an oronasal mask. After the exclusion of 32 do-not-resuscitate patients, NIV success rate was 68.5% (85/124); ICU and hospital mortality rates were 8.9% and 15.3%, respectively. However, the success rate was lower in patients with de novo respiratory failure (27.3%) compared to that of patients with AHRF (72.8%) or post-extubation respiratory failure (75.0%). In multivariate analysis, immunocompromised state, de novo respiratory failure, post-NIV (2 hours) respiratory rate, NIV mode (i.e., non-pressure support ventilation mode), and the change of NIV device were significantly associated with a lower success rate of NIV. Conclusion: AHRF and post-extubation respiratory failure were the most common indications for NIV in Korean ICUs. Overall NIV success was achieved in 68.5% of patients, with the lowest rate in patients with de novo respiratory failure.

• 한국건설관리학회논문집
• /
• 제13권3호
• /
• pp.78-88
• /
• 2012

국내의 건설실패 관련 연구는 체계화된 실패정보 분류체계 및 실패정보의 활용을 위한 방안을 제시하는 것에 초점을 맞추고 있다. 그러나, 건설현장의 한정된 관리자가 건설실패를 유발하는 다양한 원인에 대한 예방대책을 수립하는 것은 한계가 있다. 따라서, 효율적인 건설실패 예방활동이 이루지기 위해서는 많은 실패원인에 대한 정량적 평가를 통해 우선순위를 정하여 효율적인 예방대책이 수립되어야 한다. 이에 본 연구는 정량적인 평가를 통해 실패를 유발하는 핵심관리요인을 도출 할 수 있도록 FMEA(Failure Mode and Effect Analysis) 기법을 활용한 건설실패 핵심관리요인 선정방법을 제시하고, 공동주택 골조공사를 대상으로 핵심관리요인을 분석하는 것을 목적으로 하였다. 이를 위해 FMEA 기법의 위험도를 실패 위험성과 예방성으로 구분하여 평가할 수 있도록 하였다. 본 연구에서 제시한 핵심관리요인 평가방법은 건설실패의 사전예방대책을 효율적으로 수립하는데 활용될 수 있으며, 향후 유사한 연구를 통해 프로젝트 수행 단계별 혹은 다양한 시설 및 공종에 대한 핵심관리요인을 도출하는데 활용될 수 있을 것으로 기대된다.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2003년도 학술대회지
• /
• pp.395-401
• /
• 2003

In this paper, the dent printing phenomena and critical dent size which lead to premature failure of deep grooved ball bearing for automobiles are presented. The results of newly assembled test bearings showed that the ball dent size strongly affect the bearing life and inner ring raceways were the major failed parts in spite of using the dented balls. The dent printing phenomena are a root cause of premature failure, which was not reported until now. And there exist the critical ball dent size for given rolling bearings and operating conditions. So, the initial condition of tribologically mating parts should be treated as important as the failed body itself.