Search results for: failure rate

Authors: Omer Yeni

Abstract:

Ground strata failure or fall-of-ground is one of the underground mines' most prominent catastrophic risks. Mining companies use various methods/technics to prevent and critically control the associated risks. Some of those are safety by design, excavation methods, ground support, training, and competency, which all require quality control and assurance activities to confirm their efficiencies and performances and identify improvement opportunities through monitoring. However, many mining companies use quality control (QC) methods without quality assurance (QA), and they call it QA/QC together as a habit. From a simple definition, QC is a method of detecting defects, and QA is a method of preventing defects. Testing the final products at the end of the production line is not the way of proper QA/QC application but testing every component before assembly and the final product once completed. The installed ground support elements are some final products mining companies use to prevent ground strata failure. Testing the final product (i.e., rock bolt pull testing, shotcrete strength test, etc.) with QC methods only while those areas are already accessible; is not like testing an airplane full of passengers right after the production line or testing a car after the sale. Can only QC methods be called QA/QC? Can QA/QC activities be numerically scored for each critical control implemented to assess ground strata failure potential? Can numerical scores be used to identify Geotechnical Risk Rating (GRR) to determine the ground strata failure risk and its probability? This paper sets out to provide a specific QA/QC methodology to manage and confirm efficiencies and performances of the implemented critical controls and a numerical approach through the Geotechnical Risk Rating (GRR) process to assess ground strata failure risk to determine the gaps where proactive action is required to evaluate the probability of ground strata failures in underground mines.

Keywords: fall of ground, ground strata failure, QA/QC, underground

Procedia PDF Downloads 39

Authors: Tetyana Kendzerska, David T. Zhu, Michael Pugliese, Douglas Manuel, Mohsen Sadatsafavi, Marcus Povitz, Therese A. Stukel, Teresa To, Shawn D. Aaron, Sunita Mulpuru, Melanie Chin, Claire E. Kendall, Kednapa Thavorn, Rebecca Robillard, Andrea S. Gershon

Abstract:

The impact of the COVID-19 pandemic on the management of ambulatory care sensitive conditions (ACSCs) remains unknown. To compare observed and expected (projected based on previous years) trends in all-cause mortality and healthcare use for ACSCs in the first year of the pandemic (March 2020 - March 2021). A population-based study using provincial health administrative data.General adult population (Ontario, Canada). Monthly all-cause mortality, and hospitalizations, emergency department (ED) and outpatient visit rates (per 100,000 people at-risk) for seven combined ACSCs (asthma, COPD, angina, congestive heart failure, hypertension, diabetes, and epilepsy) during the first year were compared with similar periods in previous years (2016-2019) by fitting monthly time series auto-regressive integrated moving-average models. Compared to previous years, all-cause mortality rates increased at the beginning of the pandemic (observed rate in March-May 2020 of 79.98 vs. projected of 71.24 [66.35-76.50]) and then returned to expected in June 2020—except among immigrants and people with mental health conditions where they remained elevated. Hospitalization and ED visit rates for ACSCs remained lower than projected throughout the first year: observed hospitalization rate of 37.29 vs. projected of 52.07 (47.84-56.68); observed ED visit rate of 92.55 vs. projected of 134.72 (124.89-145.33). ACSC outpatient visit rates decreased initially (observed rate of 4,299.57 vs. projected of 5,060.23 [4,712.64-5,433.46]) and then returned to expected in June 2020. Reductions in outpatient visits for ACSCs at the beginning of the pandemic combined with reduced hospital admissions may have been associated with temporally increased mortality—disproportionately experienced by immigrants and those with mental health conditions. The Ottawa Hospital Academic Medical Organization

Keywords: COVID-19, chronic disease, all-cause mortality, hospitalizations, emergency department visits, outpatient visits, modelling, population-based study, asthma, COPD, angina, heart failure, hypertension, diabetes, epilepsy

Procedia PDF Downloads 62

Authors: Fu-Pei Hsiao, Fung-Chung Tu, Chien-Kuo Chiu

Abstract:

In this work, to develop a method for detailed assesses of post-earthquake seismic performance for RC buildings in Taiwan, experimental data for several column specimens with various failure modes (flexural failure, flexural-shear failure, and shear failure) are used to derive reduction factors of seismic capacity for specified damage states. According to the damage states of RC columns and their corresponding seismic reduction factors suggested by experimental data, this work applies the detailed seismic performance assessment method to identify the seismic capacity of earthquake-damaged RC buildings. Additionally, a post-earthquake emergent assessment procedure is proposed that can provide the data needed for decision about earthquake-damaged buildings in a region with high seismic hazard. Finally, three actual earthquake-damaged school buildings in Taiwan are used as a case study to demonstrate application of the proposed assessment method.

Keywords: seismic assessment, seismic reduction factor, residual seismic ratio, post-earthquake, reinforced concrete, building

Procedia PDF Downloads 374

Authors: Stefano Andrea Denes

Abstract:

The use of dental implants to rehabilitate edentulous patients has become a well-established and effective treatment option; however, despite its high success rate, this treatment is not free of complications. The fracture of implant body is a rare cause of failure but when it does occur it can present technical challenges. In this article, we report the complete removal of a fractured osseointegrated implant using electrosurgery and ultrasonic instrumentation. The postoperative course was uneventful, no bleeding, infection, or hematoma formation was observed.

Keywords: dental implant, oral surgery, electrosurgery, piezosurgery

Procedia PDF Downloads 239

Authors: B. Paygozar, S.A. Dizaji, A.C. Kandemir

Abstract:

In this study, the effects of the modified adhesive including different concentrations of Nano-silica are surveyed on the bonding strength of the adhesive scarf joints. The nanoparticles are added in two different concentrations, to an epoxy-based two-component structural adhesive, Araldite 2011, to survey the influences of the nanoparticle weight percentage on the failure load of the joints compared to that of the joints manufactured by the neat adhesive. The effects of being exposure to a moist ambience on the joint strength are also investigated for the joints produced of both neat and modified adhesives. For this purpose, an ageing process was carried out on the joints of both neat and improved kinds with variable immersion periods (20, 40 and 60 days). All the specimens were tested under a quasi-static tensile loading of 2 mm/min speed so as to find the quantities of the failure loads. Outcomes indicate that the failure loads of the joints with modified adhesives are measurably higher than that of the joint with neat adhesive, even while being put for a while under a moist condition. Another result points out that humidity lessens the bonding strength of all the joints of both types as the exposure time increases, which can be attributed to the change in the failure mode.

Keywords: bonding strength, humidity, nano-silica, scarf joint

Procedia PDF Downloads 144

Authors: Chaoyi Sun, Congxin Chen, Yun Zheng, Kaizong Xia, Wei Zhang

Abstract:

Crest loads are often encountered in hydropower, highway, open-pit and other engineering rock slopes. Toppling failure is one of the most common deformation failure types of anti-dip bedding rock slopes. Analysis on such failure of anti-dip bedding rock slopes subjected to crest loads has an important influence on engineering practice. Based on the step-by-step analysis approach proposed by Goodman and Bray, a geo-mechanical model was developed, and the related analysis approach was proposed for the toppling failure of anti-dip bedding rock slopes subjected to crest loads. Using the transfer coefficient method, a formulation was derived for calculating the residual thrust of slope toe and the support force required to meet the requirements of the slope stability under crest loads, which provided a scientific reference to design and support for such slopes. Through slope examples, the influence of crest loads on the residual thrust and sliding ratio coefficient was investigated for cases of different block widths and slope cut angles. The results show that there exists a critical block width for such slope. The influence of crest loads on the residual thrust is non-negligible when the block thickness is smaller than the critical value. Moreover, the influence of crest loads on the slope stability increases with the slope cut angle and the sliding ratio coefficient of anti-dip bedding rock slopes increases with the crest loads. Finally, the theoretical solutions and numerical simulations using Universal Distinct Element Code (UDEC) were compared, in which the consistent results show the applicability of both approaches.

Keywords: anti-dip bedding rock slope, crest loads, stability analysis, toppling failure

Procedia PDF Downloads 156

Authors: Abdelmounaim Zanaz, Sylvie Yotte, Fazia Fouchal, Alaa Chateauneuf

Abstract:

This paper presents a methodology for probabilistic assessment of bearing capacity and prediction of failure mechanism of masonry vaults at the ultimate state with consideration of the natural variability of Young’s modulus of stones. First, the computation model is explained. The failure mode is the most reported mode, i.e. the four-hinge mechanism. Based on this assumption, the study of a vault composed of 16 segments is presented. The Young’s modulus of the segments is considered as random variable defined by a mean value and a coefficient of variation CV. A relationship linking the vault bearing capacity to the modulus variation of voussoirs is proposed. The failure mechanisms, in addition to that observed in the deterministic case, are identified for each CV value as well as their probability of occurrence. The results show that the mechanism observed in the deterministic case has decreasing probability of occurrence in terms of CV, while the number of other mechanisms and their probability of occurrence increase with the coefficient of variation of Young’s modulus. This means that if a significant change in the Young modulus of the segments is proven, taken it into account in computations becomes mandatory, both for determining the vault bearing capacity and for predicting its failure mechanism.

Keywords: masonry, mechanism, probability, variability, vault

Procedia PDF Downloads 416

Authors: Jared R. Chapman

Abstract:

This study introduces a type of motivational information system called an educational engagement information system (EEIS). An EEIS draws on principles of behavioral economics, motivation theory, and learning cognition theory to design information systems that help students want to improve their performance. This study compares academic outcomes for course sections taught by part- and full-time instructors both with and without an EEIS. Without an EEIS, students in the part-time instructor's course sections demonstrated significantly higher failure rates (a 143.8% increase) and dropout rates (a 110.4% increase) with significantly fewer students scoring a B- or higher (39.8% decrease) when compared to students in the course sections taught by a full-time instructor. It is concerning that students in the part-time instructor’s course without an EEIS had significantly lower academic outcomes, suggesting less understanding of the course content. This could impact retention and continuation in a major. With an EEIS, when comparing part- and full-time instructors, there was no significant difference in failure and dropout rates or in the number of students scoring a B- or higher in the course. In fact, with an EEIS, the failure and dropout rates were statistically identical for part- and full-time instructor courses. When using an EEIS (compared with not using an EEIS), the part-time instructor showed a 62.1% decrease in failures, a 61.4% decrease in dropouts, and a 41.7% increase in the number of students scoring a B- or higher in the course. We are unaware of other interventions that yield such large improvements in academic performance. This suggests that using an EEIS such as Delphinium may compensate for part-time instructors’ limitations of expertise, time, or rewards that can have a negative impact on students’ academic outcomes. The EEIS had only a minimal impact on failure rates (7.7% decrease) and dropout rates (18.8% decrease) for the full-time instructor. This suggests there is a ceiling effect for the improvements that an EEIS can make in student performance. This may be because experienced instructors are already doing the kinds of things that an EEIS does, such as motivating students, tracking grades, and providing feedback about progress. Additionally, full-time instructors have more time to dedicate to students outside of class than part-time instructors and more rewards for doing so. Using adjunct and other types of part-time instructors will likely remain a prevalent practice in higher education management courses. Given that using part-time instructors can have a negative impact on student graduation and persistence in a field of study, it is important to identify ways we can augment part-time instructors’ performance. We demonstrated that when part-time instructors use an EEIS, it can result in significantly lower students’ failure and dropout rates and an increase in the rate of students earning a B- or above; and bring their students’ performance to parity with the performance of students taught by a full-time instructor.

Keywords: gamification, engagement, motivation, academic outcomes

Procedia PDF Downloads 40

Authors: Haider Al-Zubaidy, Xiao-Ling Zhao, Riadh Al-Mahaidi

Abstract:

In recent years, the technique adhesively-bonded fibre reinforced polymer (FRP) composites has found its way into civil engineering applications and it has attracted a widespread attention as a viable alternative strategy for the retrofitting of civil infrastructure such as bridges and buildings. When adopting this method, adhesive has a significant role and controls the general performance and degree of enhancement of the strengthened and/or upgraded structures. This is because the ultimate member strength is highly affected by the failure mode which is considerably dependent on the utilised adhesive. This paper concerns with experimental investigations on the effect of the adhesive used on the bond between CFRP patch and steel plate under medium impact tensile loading. Experiment were conducted using double strap joints and these samples were prepared using two different types of adhesives, Araldite 420 and MBrace saturant. Drop mass rig was used to carry out dynamic tests at impact speeds of 3.35, 4.43 and m/s while quasi-static tests were implemented at 2mm/min using Instrone machine. In this test program, ultimate load-carrying capacity and failure modes were examined for all loading speeds. For both static and dynamic tests, the adhesive type has a significant effect on ultimate joint strength. It was found that the double strap joints prepared using Araldite 420 showed higher strength than those prepared utilising MBrace saturant adhesive. Failure mechanism for joints prepared using Araldite 420 is completely different from those samples prepared utilising MBrace saturant. CFRP failure is the most common failure pattern for joints with Araldite 420, whereas the dominant failure for joints with MBrace saturant adhesive is adhesive failure.

Keywords: CFRP/steel double strap joints, adhesives of different ductility, dynamic tensile loading, bond between CFRP and steel

Procedia PDF Downloads 211

Authors: Richard Colwell, Thomas Englert

Abstract:

In cryogenic liquefaction processes, brazed aluminum core heat exchangers are used to minimize surface area/volume of the exchanger. Aluminum alloy (5083-H321; UNS A95083) piping must transition to higher melting point 304L stainless steel piping outside of the heat exchanger kettle or cold box for safety reasons. Since aluminum alloys and austenitic stainless steel cannot be directly welded to together, a transition joint consisting of 5 layers of different metals explosively bonded are used. Failures of two of these joints resulted in process shut-down and loss of revenue. Failure analyses, FEA analysis, and mock-up testing were performed by multiple teams to gain a further understanding into the failure mechanisms involved.

Keywords: explosion bonding, intermetallic compound, thermal strain, titanium-nickel Interface

Procedia PDF Downloads 177

Authors: A. S. Grewal, R. S. Sangwan, Dharambir, Vikas Dhanda

Abstract:

The purpose of this paper is to develop and analyze two reliability models for a system of non-identical firearms – one is standard firearm (called as original unit) and the other is a country-made firearm (called as duplicate /substandard unit). There is a single server who comes immediately to do inspection and repair whenever needed. On the failure of standard firearm, the server inspects the operative country-made firearm to see whether the unit is capable of performing the desired function well or not. If country-made firearm is not capable to do so, the operation of the system is stopped and server starts repair of the standard firearms immediately. However, no inspection is done at the failure of the country-made firearm as the country-made firearm alone is capable of performing the given task well. In model I, priority to repair the standard firearm is given in case system fails completely and country-made firearm is already under repair, whereas in model II there is no such priority. The failure and repair times of each unit are assumed to be independent and uncorrelated random variables. The distributions of failure time of the units are taken as negative exponential while that of repair and inspection times are general. By using semi-Markov process and regenerative point technique some econo-reliability measures are obtained. Graphs are plotted to compare the MTSF (mean time to system failure), availability and profit of the models for a particular case.

Keywords: non-identical firearms, inspection, priority to repair, semi-Markov process, regenerative point

Procedia PDF Downloads 403

Authors: Weigao. Wu, Stefano. Utili

Abstract:

Based on the kinematic approach of limit analysis, a full set of upper bound solutions for the stability of homogeneous rock slopes subjected to tension cracks are obtained. The generalized Hoek-Brown failure criterion is employed to describe the non-linear strength envelope of rocks. In this paper, critical failure mechanisms are determined for cracks of known depth but unspecified location, cracks of known location but unknown depth, and cracks of unspecified location and depth. It is shown that there is a nearly up to 50% drop in terms of the stability factors for the rock slopes intersected by a tension crack compared with intact ones. Tables and charts of solutions in dimensionless forms are presented for ease of use by practitioners.

Keywords: Hoek-Brown failure criterion, limit analysis, rock slope, tension cracks

Procedia PDF Downloads 315

Authors: M. Ezzat, Y. Zaghloul, T. Sorour, A. Hefny, M. Eid

Abstract:

Ultimate capacity of large diameter bored piles is usually determined from pile loading tests as recommended by several international codes and foundation design standards. However, loading of this type of piles till achieving apparent failure is practically seldom. In this paper, numerical analyses are carried out to simulate load test of a large diameter bored pile performed at the location of Alzey highway bridge project (Germany). Test results of pile load settlement relationship till failure as well as results of the base and shaft resistances are available. Apparent failure was indicated in this test by the significant increase of the induced settlement during the last load increment applied on the pile head. Measurements of this pile load test are used to assess the quality of the numerical models investigated. Three different material soil models are implemented in the analyses: Mohr coulomb (MC), Soft soil (SS), and Modified Mohr coulomb (MMC). Very good agreement is obtained between the field measured settlement and the calculated settlement using the MMC model. Results of analysis showed also that the MMC constitutive model is superior to MC, and SS models in predicting the ultimate base and shaft resistances of the large diameter bored pile. After calibrating the numerical model, behavior of large diameter bored piles under axial loads is discussed and the formation of the plastic zone around the pile is explored. Results obtained showed that the plastic zone below the base of the pile at failure extended laterally to about four times the pile diameter and vertically to about three times the pile diameter.

Keywords: ultimate capacity, large diameter bored piles, plastic zone, failure, pile load test

Procedia PDF Downloads 119

Authors: Vahdettin Sariyel, Birol Dag

Abstract:

In this research, it is aimed to determine the effects of several environmental factors on adaptation and some yield parameters of Saanen goats reared under intensive conditions at a private farm in Konya province. Gestation rate, twins rate and litter size were evaluated as reproductive traits. Gestation rate was determined as 93.8% and 90.5% for 2011 and 2012 years respectively. Twins rate was determined as 59.35 % and 70.00 % for 2011 and 2012 years respectively. Litter size was 1.49 and 1.46 for 2011 and 2012 years respectively. Survival rates of kids from birth to weaning at three months of age were found as 87.74 % and 98.54 % for 2011 and 2012 years respectively.

Keywords: gestation rate, reproduction, saanen, twins rate, vitality

Procedia PDF Downloads 566

Authors: Mikhail O. Eremin

Abstract:

Present work is devoted to experimental study and numerical modelling of failure of rocks typical for Kuzbass coal basin (Russia). The main goal was to define strength and deformation characteristics of rocks on the base of uniaxial compression and three-point bending loadings and then to build a mathematical model of failure process for both types of loading. Depending on particular physical-mechanical characteristics typical rocks of Kuzbass coal basin (sandstones, siltstones, mudstones, etc. of different series – Kolchuginsk, Tarbagansk, Balohonsk) manifest brittle and quasi-brittle character of failure. The strength characteristics for both tension and compression are found. Other characteristics are also found from the experiment or taken from literature reviews. On the base of obtained characteristics and structure (obtained from microscopy) the mathematical and structural models are built and numerical modelling of failure under different types of loading is carried out. Effective characteristics obtained from modelling and character of failure correspond to experiment and thus, the mathematical model was verified. An Instron 1185 machine was used to carry out the experiments. Mathematical model includes fundamental conservation laws of solid mechanics – mass, impulse, energy. Each rock has a sufficiently anisotropic structure, however, each crystallite might be considered as isotropic and then a whole rock model has a quasi-isotropic structure. This idea gives an opportunity to use the Hooke’s law inside of each crystallite and thus explicitly accounting for the anisotropy of rocks and the stress-strain state at loading. Inelastic behavior is described in frameworks of two different models: von Mises yield criterion and modified Drucker-Prager yield criterion. The damage accumulation theory is also implemented in order to describe a failure process. Obtained effective characteristics of rocks are used then for modelling of rock mass evolution when mining is carried out both by an open-pit or underground opening.

Keywords: damage accumulation, Drucker-Prager yield criterion, failure, mathematical modelling, three-point bending, uniaxial compression

Procedia PDF Downloads 143

Authors: Riccardo Patriarca, Giulio Di Gravio, Francesco Costantino, Massimo Tronci

Abstract:

An accurate inventory management policy acquires a crucial role in the several high-availability sectors. In these sectors, due to the high-cost of spares and backorders, an (S-1, S) replenishment policy is necessary for high-availability items. The policy enables the shipment of a substitute efficient item anytime the inventory size decreases by one. This policy can be modelled following the Multi-Echelon Technique for Recoverable Item Control (METRIC). The METRIC is a system-based technique that allows defining the optimum stock level in a multi-echelon network, adopting measures in line with the decision-maker’s perspective. The METRIC defines an availability-cost function with inventory costs and required service levels, using as inputs data about the demand trend, the supplying and maintenance characteristics of the network and the budget/availability constraints. The traditional METRIC relies on the hypothesis that a Poisson distribution well represents the demand distribution in case of items with a low failure rate. However, in this research, we will explore the effects of using a Poisson distribution to model the demand of low failure rate items characterized by an irregular demand trend. This characteristic of a demand is not included in the traditional METRIC formulation leading to the need of revising its traditional formulation. Using the CV (Coefficient of Variation) and ADI (Average inter-Demand Interval) classification, we will define the inherent flaws of Poisson-based METRIC for irregular demand items, defining an innovative ad hoc distribution which can better fit the irregular demands. This distribution will allow defining proper stock levels to reduce stocking and backorder costs due to the high irregularities in the demand trend. A case study in the aviation domain will clarify the benefits of this innovative METRIC approach.

Keywords: METRIC, inventory management, irregular demand, spare parts

Procedia PDF Downloads 318

Authors: Aboozar Aghaei

Abstract:

In the present work, the dissimilar Monel400 and SS316 were joined by friction stir welding (FSW). The applied rotating speed was 400 rpm, whereas the traverse speed varied between 50 and 150 mm/min. At a constant rotating speed, the sound welds were obtained at the welding speeds of 50 and 100 mm/min. However, a groove-like defect was formed when the welding speed exceeded 100 mm/min. The mechanical properties of the joints were evaluated using tensile and fatigue tests. The fatigue strength of dissimilar FSWed specimens was higher than that of both Monel400 and SS316. To study the failure behavior of FSWed specimens, the fracture surfaces were analyzed using a scanning electron microscope (SEM). The failure analysis indicates that different mechanisms may contribute to the fracture of welds. This was attributed to the dissimilar characteristics of dissimilar materials exhibiting different failure behaviors.

Keywords: frictions stir welding (FSW), stainless steel, mechanical properties, Monel400

Procedia PDF Downloads 54

Authors: Wei-Neng Wang, Jhy-Yuan Shieh, Jhy-Hwa Chen, Juin-Jen Chang

Abstract:

This paper incorporate tax evasion into a one-sector real business cycle (RBC) model to explores the quantitative interrelations between income tax rate and equilibrium (in)determinacy, and income tax rate is endogenously determined in order to balance the government budget. We find that the level of the effective income tax rate is key factor for equilibrium (in)determinacy, instead of the level of income tax rate in a tax evasion economy. Under an economy with tax evasion, the higher income tax rate is not sufficiently to lead to equilibrium indeterminate, it must combine with a necessary condition which is the lower fraction of tax evasion and that can result in agents' optimistic expectations to become self-fulfilling and sunspot fluctuation more likely to occur. On the other hand, an economy with tax evasion can see its macroeconomy become more stabilize, and a higher fraction of income tax evasion may has a stronger stabilizing effect.

Keywords: tax evasion, balanced-budget rule, equlibirium (in)determinacy, effective income tax rate

Procedia PDF Downloads 26

Authors: Alamgir Naushad, Ghulam Abbas, Shehzad Ali Shah, Ziaul Haq Abbas

Abstract:

Unlike conventional networks, it is particularly challenging to manage resources efficiently in Wireless Sensor Networks (WSNs) due to their inherent characteristics, such as dynamic network topology and limited bandwidth and battery power. To ensure energy efficiency, this paper presents a routing protocol for WSNs, namely, Enhanced Hybrid Multipath Routing (EHMR), which employs hierarchical clustering and proposes a next hop selection mechanism between nodes according to a maximum residual energy metric together with a minimum hop count. Load-balancing of data traffic over multiple paths is achieved for a better packet delivery ratio and low latency rate. Reliability is ensured in terms of higher data rate and lower end-to-end delay. EHMR also enhances the fast-failure recovery mechanism to recover a failed path. Simulation results demonstrate that EHMR achieves a higher packet delivery ratio, reduced energy consumption per-packet delivery, lower end-to-end latency, and reduced effect of data rate on packet delivery ratio when compared with eminent WSN routing protocols.

Keywords: energy efficiency, load-balancing, hierarchical clustering, multipath routing, wireless sensor networks

Procedia PDF Downloads 48

Authors: N. Abbas, S. Lagomarsino, S. Cattari

Abstract:

Examining existing experimental results for shallow rigid foundations subjected to vertical centric load (N), accompanied or not with a bending moment (M), two main non-linear mechanisms governing the cyclic ‎response of the soil-foundation system can be distinguished: foundation uplift and soil yielding. A soil-foundation failure limit, is defined as a domain of resistance in the two dimensional (2D) load space (N, M) inside of which lie all the admissible combinations of loads; these latter correspond to a pure elastic, non-linear elastic or plastic behavior of the soil-foundation system, while the points lying on the failure limit correspond to a combination of loads leading to a failure of the soil-foundation system. In this study, the proposed resistance domain is constructed analytically based on mechanics. Original elastic limit, uplift initiation ‎limit and iso-uplift limits are constructed inside this domain. These limits give a prediction ‎of the mechanisms activated for each combination of loads applied to the ‎foundation. A comparison of the proposed failure limit with experimental tests existing in the literature shows interesting results. Also, the developed uplift initiation limit and iso-uplift curves are confronted with others already proposed in the literature and widely used due to the absence of other alternatives, and remarkable differences are noted, showing evident errors in the past proposals and relevant accuracy for those given in the present work.

Keywords: foundation uplift, iso-uplift curves, resistance domain, soil yield

Procedia PDF Downloads 356

Authors: Stephen V. Crowder, Jonathan W. Lane

Abstract:

With short production development times, there is an increased need to demonstrate product reliability relatively quickly with minimal testing. In such cases there may be few if any observed failures. Thus it may be difficult to assess reliability using the traditional reliability test plans that measure only time (or cycles) to failure. For many components, degradation measures will contain important information about performance and reliability. These measures can be used to design a minimal test plan, in terms of number of units placed on test and duration of the test, necessary to demonstrate a reliability goal. In this work we present a case study involving an electronic component subject to degradation. The data, consisting of 42 degradation paths of cycles to failure, are first used to estimate a reliability function. Bootstrapping techniques are then used to perform power studies and develop a minimal reliability test plan for future production of this component.

Keywords: degradation measure, time to failure distribution, bootstrap, computational science

Procedia PDF Downloads 490

Authors: Yu-Jen Chang, Yun Chen, Hei-Lam Wong

Abstract:

The Economic Lot Scheduling Problem (ELSP) is a valuable mathematical model that can support decision-makers to make scheduling decisions. The basic period approach is effective for solving the ELSP. The assumption for applying the basic period approach is that a product must use its maximum production rate to be produced. However, a product can lower its production rate to reduce the average total cost when a facility has extra idle time. The past researches discussed how a product adjusts its production rate under the common cycle approach. To the best of our knowledge, no studies have addressed how a product lowers its production rate under the basic period approach. This research is the first paper to discuss this topic. The research develops a simple fixed rate approach that adjusts the production rate of a product under the basic period approach to solve the ELSP. Our numerical example shows our approach can find a better solution than the traditional basic period approach. Our mathematical model that applies the fixed rate approach under the basic period approach can serve as a reference for other related researches.

Keywords: economic lot, basic period, genetic algorithm, fixed rate

Procedia PDF Downloads 538

Authors: Cecília M. Antão, Paulo Jorge Nogueira

Abstract:

Breast cancer (BC) is the first cause of cancer mortality among Portuguese women. This retrospective observational study aimed at identifying comorbidities associated with BC female patients admitted to Portuguese public hospitals (2010-2018), investigating the effect of comorbidities on BC mortality rate, and building a predictive model using logistic regression. Results showed that the BC mortality in Portugal decreased in this period and reached 4.37% in 2018. Adjusted odds ratio indicated that secondary malignant neoplasms of liver, of bone and bone marrow, congestive heart failure, and diabetes were associated with an increased chance of dying from breast cancer. Although the Lisbon district (the most populated area) accounted for the largest percentage of BC patients, the logistic regression model showed that, besides patient’s age, being resident in Bragança, Castelo Branco, or Porto districts was directly associated with an increase of the mortality rate.

Keywords: breast cancer, comorbidities, logistic regression, adjusted odds ratio

Procedia PDF Downloads 57

Authors: Aboozar Aghaei, Kamran Dehghani

Abstract:

In the present work, the dissimilar Monel400 and SS316 were joined by friction stir welding (FSW). The applied rotating speed was 400 rpm, whereas the traverse speed varied between 50 and 150 mm/min. At a constant rotating speed, the sound welds were obtained at the welding speeds of 50 and 100 mm/min. However, a groove-like defect was formed when the welding speed exceeded 100 mm/min. The mechanical properties of the joints were evaluated using tensile and fatigue tests. The fatigue strength of dissimilar FSWed specimens was higher than that of both Monel400 and SS316. To study the failure behavior of FSWed specimens, the fracture surfaces were analyzed using a scanning electron microscope (SEM). The failure analysis indicates that different mechanisms may contribute to the fracture of welds. This was attributed to the dissimilar characteristics of dissimilar materials exhibiting different failure behaviors.

Keywords: frictions stir welding, stainless steel, Monel400, mechanical properties

Procedia PDF Downloads 56

Authors: Belén Vinaixa Kinnear, Arturo Hidalgo López, Bernardo Elembo Wilasi, Pablo Fernández Pérez, Cecilia Hernández Fuentealba

Abstract:

The expanded use of risk assessment in legislative and corporate decision-making has increased the role of expert judgement in giving data for security-related decision-making. Expert judgements are required in most steps of risk assessment: danger recognizable proof, hazard estimation, risk evaluation, and examination of choices. This paper presents a fault tree analysis (FTA), which implies a probabilistic failure analysis applied to leakage of oil in a subsea production system. In standard FTA, the failure probabilities of items of a framework are treated as exact values while evaluating the failure probability of the top event. There is continuously insufficiency of data for calculating the failure estimation of components within the drilling industry. Therefore, fuzzy hypothesis can be used as a solution to solve the issue. The aim of this paper is to examine the leaks from the Zafiro West subsea oil facility by using fuzzy fault tree analysis (FFTA). As a result, the research has given theoretical and practical contributions to maritime safety and environmental protection. It has been also an effective strategy used traditionally in identifying hazards in nuclear installations and power industries.

Keywords: expert judgment, probability assessment, fault tree analysis, risk analysis, oil pipelines, subsea production system, drilling, quantitative risk analysis, leakage failure, top event, off-shore industry

Procedia PDF Downloads 159

Authors: Trisiladi Supriyanto

Abstract:

Although much research has been done on the pricing benchmark both in terms of fiqh or Islamic economic perspective, but no substitution for the concept of interest (rate of interest) up to now in the application of Islamic Banking because some of the jurists from the middle east even allow the use of a benchmark rate such as LIBOR (London Interbank Offered Rate) as a measure of Islamic financial asset prices, so in other words, they equate the concept of rate of interest with the concept of rate of profit, which is the core reason (raison detre) for the replacement of usury as instructed in the Quran. This study aims to find the concept of rate of profit on Islamic banking that can create economic justice and stability in Islamic Banking and Capital market. Rate of profit that creates economic justice and stability can be achieved through its role in maintaining the stability of the financial system in which there is an equitable distribution of income and wealth. To determine the role of the rate of profit as the basis of the sharing system implemented in the Islamic financial system, we can see the connection of rate of profit in creating financial stability, especially in the asset-liability management of financial institutions that generate a stable net margin or the rate of profit that is not affected by the ups and downs of the market risk factors including indirect effect on interest rates. Furthermore, Islamic financial stability can be seen from the role of the rate of profit on the stability of the Islamic financial assets that are measured from the Islamic financial asset price volatility in Islamic Bond Market in Capital Market.

Keywords: Rate of profit, economic justice, stability, equitable distribution of income, equitable distribution of wealth

Procedia PDF Downloads 378

Authors: Matthew Scott Lau

Abstract:

This study addresses the research question: How effective has the Community Health Assist Scheme (CHAS) been in reducing market failure in Singapore’s healthcare sector? The CHAS policy, introduced in 2012 in Singapore, aims to improve accessibility and affordability of healthcare by offering subsidies to low and middle-income groups and elderly individuals for general practice consultations and healthcare. The investigation was undertaken by acquiring and analysing primary and secondary research data from 3 main sources, including handwritten survey responses of 334 individuals who were valid CHAS subsidy recipients (CHAS cardholders) from 5 different locations in Singapore, interview responses from two established general practitioner doctors with working knowledge of the scheme, and information from literature available online. Survey responses were analysed to determine how CHAS has affected the affordability and consumption of healthcare, and other benefits or drawbacks for CHAS users. The interview responses were used to explain the benefits of healthcare consumption and provide different perspectives on the impacts of CHAS on the various parties involved. Online sources provided useful information on changes in healthcare consumerism and Singapore’s government policies. The study revealed that CHAS has been largely effective in reducing market failure as the subsidies granted to consumers have improved the consumption of healthcare. This has allowed for the external benefits of healthcare consumption to be realized, thus reducing market failure. However, the study also revealed that CHAS cannot be fully effective in reducing market failure as the scope of CHAS prevents healthcare consumption from fully reaching the socially optimal level. Hence, the study concluded that CHAS has been effective to a large extent in reducing market failure in Singapore’s healthcare sector, albeit with some benefits to third parties yet to be realised. There are certain elements of the investigation, which may limit the validity of the conclusion, such as the means used to determine the socially optimal level of healthcare consumption, and the survey sample size.

Keywords: healthcare consumption, health economics, market failure, subsidies

Procedia PDF Downloads 136

Authors: Niloufar Khoshbakht, Peggi L. Clouston, Sanjay R. Arwade, Alexander C. Schreyer

Abstract:

Laminated veneer bamboo (LVB) is a structural engineered composite made from glued layers of bamboo. A relatively new building product, LVB is currently employed in similar sizes and applications as dimensional lumber. This study describes the results of a 3D elastic Finite Element model for halfhole specimens when loaded in compression parallel-to-grain per ASTM 5764. The model simulates LVB fracture initiation due to shear stresses in the dowel joint and predicts displacement at failure validated through comparison with experimental results. The material fails at 1mm displacement due to in-plane shear stresses. The paper clarifies the complex interactive state of in-plane shear, tension perpendicular-to-grain, and compression parallel-to-grain stresses that form different distributions in the critical zone beneath the bolt hole for half-hole specimens. These findings are instrumental in understanding key factors and fundamental failure mechanisms that occur in LVB dowel connections to help devise safe standards and further LVB product adoption and design.

Keywords: composite, dowel connection, embedment strength, failure behavior, finite element analysis, Moso bamboo

Procedia PDF Downloads 243

Authors: Mustapha Kamel Mihoubi, Mohamed Essadik Kerkar

Abstract:

Probabilistic risk analysis models are used to provide a better understanding of the reliability and structural failure of works, including when calculating the stability of large structures to a major risk in the event of an accident or breakdown. This work is interested in the study of the probability of failure of concrete dams through the application of reliability analysis methods including the methods used in engineering. It is in our case, the use of level 2 methods via the study limit state. Hence, the probability of product failures is estimated by analytical methods of the type first order risk method (FORM) and the second order risk method (SORM). By way of comparison, a level three method was used which generates a full analysis of the problem and involves an integration of the probability density function of random variables extended to the field of security using the Monte Carlo simulation method. Taking into account the change in stress following load combinations: normal, exceptional and extreme acting on the dam, calculation of the results obtained have provided acceptable failure probability values which largely corroborate the theory, in fact, the probability of failure tends to increase with increasing load intensities, thus causing a significant decrease in strength, shear forces then induce a shift that threatens the reliability of the structure by intolerable values of the probability of product failures. Especially, in case the increase of uplift in a hypothetical default of the drainage system.

Keywords: dam, failure, limit-state, monte-carlo, reliability, probability, simulation, sliding, taylor

Procedia PDF Downloads 298

Authors: Siphat Lim

Abstract:

The result of the study revealed that the interaction between money, exchange rate, and price level was mainly derived from the policy-induced by the central bank. Furthermore, the variation of inflation was explained weakly by exchange rate and money supply. In the period of twelfth-month, the variation of inflation which caused by exchange rate and money supply were not more than 1.78 percent and 9.77 percent, respectively.

Keywords: money supply, exchange rate, price level, VAR model

Procedia PDF Downloads 251