Sharif Digital Repository

As aircraft fleets get older, the challenge of Flight Safety gets greater. This Thesis focus on management strategies and principles to keep long-life fleet safe and effective into old age. But the safety and efficacy are not the only ones who are considered at long-life fleet. Here the question arises why the aircraft prior to exposure to the effects of rising life expectancy, are not replaced by other aircraft.The reason is the high cost of the replacement. Aircraft are expensive to design and manufacture. In commercial aviation, extreme competition and miniscule profit force pressures to delay replacement of older aircraft with expensive new types. But in Military aircraft reason for... 

In this thesis we study non-parametric estimation of constrained bivariate probability density functions and discuss its applications in model construction of dynamical systems and their safety verification. In many industrial applications, it is essential to obtain an estimator for density functions that satisfy particular constraints. If additional information about distribution of a random variable is known in form of moment constraints, the kernel density estimator can be obtained by replacing uniform weights with the generalized empirical likelihood estimators.Our results indicate that the constructed kernel density estimator provides an improved approximation. Moreover, due to the... 

One of the most important stages to designing a process plant is layout of equipment in unit area. There are plenty of routine procedures to find out equipment arrangement and their separation distances based on process and cost criteria. One of this Procedures is the use of codes and standards. Although some studies have been carried out to enter safety parameters to conventional procedures, the problem complexity because of the number of involved equipment is still of concern. To clear these ambiguities, the new approach presented in this thesis is aimed at quantifying the effects of adjacent equipment on each other. In this way, fire radiation and explosion have been selected as the major... 

Despite eye-catching progressive trends in highway safety, there have been a great number of unpleasant incidents in highways. A number of 8841 people died in road accidents in the first 6 month this year with 1.7% increase compared to the accidents occurred in 1396 [59]. Operation of a modeling process shall provide the engineers with more opportunities to identify the affecting factors in roads incidents. Safety infrastructure management is mainly aimed at ensuring the efficient measurement, systematic recognition and consequently deterioration of road accidents when they have been designed, constructed and used [37]. Building information modeling (BIM) tends to be a developed managerial... 

Competitive world of industrial production need more speed and faster reaction for the customer needs. This should be carried out in low cost activities while satisfying what the consumers and customers require. Business of commercial refrigerators and freezers is a big industry targeting small to big customers. In this thesis a systematic method relying on reduction of cost, reworking and unexpected expenditures in product life is utilized. Stands for Design for Manufacturing, DFM is a series of principles and guideline simply to achieve a faultless design of a product so that the non-incurred costs of the product travel through its life cycle become minimized. Freezers and refrigerators... 

As Ethylene Oxide is a highly toxic, flammable, and hazardous material, the consequences of any malfunction in an Ethylene Oxide reactor may be irreparable. The aim of this thesis is to evaluate the probable consequences of an accident in Morvarid Petrochemical Co.’s Ethylene Oxide Reactor in order to find probable hazardous scenarios. In this project, probable accidents were modelled and evaluated by Phast software in different scenarios, and the outcomes were investigated. In addition, if necessary, a set of solutions were proposed to decrease casualties in hazardous scenarios. The results may be used to change layouts according to Consequence Modelling. Results illustrated that... 

In order to respond to the concerns of safety and productivity of construction operations, in this research, the model based on discrete event simulation has been proposed. In this model, with simulation of different scenarios of construction operation in planning and designing phases, before starting construction operation, the level of safety and productivity of each scenario evaluates concurrently. The Scenario that best meets the safety and productivity concerns concurrently has been selected for operation. In order to evaluate the feasibility of the model in construction operation, the model has been implemented in a fabrical example. The operation of installing tiles on the sloping... 

In today's complex engineering systems, any increase in efficiency naturally comes with concerns about accepted level of safety. As demand for aerial transportation is increasing, more researches are conducted to increase the capacity of current controlled airspaces; as the limited capacity of the so called "en-route" corridors appears to be the main concern in the industry. Meanwhile, a solution is expected to be in more efficient exploitation of the current airspace capacities via optimizing the standards related to maintaining Separation Minima (SM) among flying aircrafts. Current standards assume an aircraft to be at the center of a circle with a radius equal to 5 nm. In this work,... 

The 1991 NIOSH Lifting Equation (NLE) is widely used to assess risk of injury to the spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses two biomechanical models of the spine to verify whether the RWL generates L5-S1 loads within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in some studies).Severallifting activities are simulated here to evaluate the RWL by the NLE and the L5-S1 loads by the models. In lifting activities involving moderate to large forward trunk flexion, the estimated RWL generates L5-S1 spine loads exceeding the recommended limits. The NIOSH vertical multiplier is the likely... 

In this study the modeling of Bushehr power plant containment is considered. In Bushehr atomic power plant, which has a unique design, the containment is similar to PWR power plants with a metal sphere, but the installed reactor is a VVER-1000. After a full study on the containment and its systems, the required date for modeling is gathered and afterwards, the engineering handbook is prepared for MELCOR input code and then the modeling and size classification of the containment is done in 4 different ways, including the control volumes of 1, 9, 23 and 30 and then the temperature, pressure and density of hydrogen is examined. The result of studying control volume sensitivity reveals that 23... 

Wildfires are complex phenomena with many indeterminate and highly unpredictable driving factors that have remained unresolved. During the last decade, machine learning methods have successfully excelled in wildfire prediction as an alternative to traditional field research methods by elucidating the relationship between historical wildfire events and various important variables. The main purpose of this research is to evaluate the random forest machine learning approach and the logistic regression statistical approach to prepare a wildfire susceptibility map using data related to historical wildfires and effective variables in the Okanogan region in Washington province of the United States... 

Identification of different hazards in a UF6 production process, and evaluation of the risk originated from these hazards is the main objective of this project. A number of hazards are present in a typical UF6 production process, such as leakage of chemical gases like HF and F2 and also radioactive UF6 gas release. In order to evaluate risk due to these hazards, probabilistic approach has been used. Due to lack of probabilistic safety criteria (PSC) for chemical releases, only for UF6 gas release risk assessment has been done. As a first step in PSA of this process eight groups of initiating events have been identified using HAZOP study, and for each initiating event, event tree analysis... 

In general, release of hazardous gas in chemical process plants could be due to two reasons. First is failures due to degradation of components that have inventory of hazardous gas in standard process conditions, and the second is deviation of system from standard process conditions because of different failure modes of related components, e.g. controller equipments. The purpose of this study is, calculating the probability of H2S releasing in GS(03) plant of Arak Heavy Water factory, using PSA methods and its risk assessment. At First, fifteen groups of initiating events were identified with Hazop study for desired system. Then, for calculating the frequency of each event, the combination... 

Inherent safety means that the process is naturally safe and the conditions of occurrence of unsafe cases and situations are eliminated from the system so that unsafe conditions can be controlled and prevented from occurrence by means of layers of protection. In general, evaluation of inherent safety may be studied in two different conditions; the first one is associated with the units that are not completely designed and built yet. In the initial steps of developing a process, there is much freedom in the determination of materials, equipment, and designing variables. As soon as the process enters its life cycle, making changes in the process will be very difficult and expensive. Therefore,... 

Transfer of Spent Nuclear Fuel from reactor building to storage facilities is one of the most important operations at Front End of Nuclear Fuel Cycle. The aim of this project is to calculate the risk of the radioactive materials release into the environment during various stages of spent fuel transfer operations. In addition, the contribution of each of the initiating events in total release probability were also determined. For this purpose, Probabilistic Risk Assessment method which is usually used in safety evaluation of the nuclear facilities, is applied. The main tools used in this method are event tree and fault tree. In this study, SAPHIRE software has been used to construct the event... 

In the absence of appropriate control, several accidents in the nuclear power, lead to serious consequences including core melted and radiation leakage outside reactor containment. In all these events, when core melted, the reactor operation is always finished and all efforts are then directed to environmental impacts of radioactive materials to the external environment. However, the occurrence of events that would bypass reactor containment, have special significance, because all possible efforts in order to limit the leakage of radioactive materials to the external environment are ineffective. In this respect the occurrence of such incidents, as most of which is considered the worst... 

Station Blackout (SBO) involves Loss of Offsite Power (LOOP) concurrent with failure of the onsiteemergency ac power system. Although SBO is a beyond designbasis accident, in recent years this accident attracts a lot of attention. Fukushima nuclear accident which was initiated by earthquake followedby tsunami led to a SBO accident. In this thesis, Probabilistic Safety Assessment (PSA) is applied to analyze SBO in IR-360 nuclear power plant and to compute its frequency. Meanwhile, weak points of the plant are identified in order to minimize the SBOprobability of occurrence. Fault tree method is used to evaluate emergency power system and offsite power system reliabilities. Common Cause... 

Fire is one of the most important events in nuclear power plants which has a large share of total core damage frequency. For example, the core damage frequency in Bushehr nuclear power plant from fire accidents is 6.1E-6/ year which is equivalent to about 63 percent of core damage frequency from all internal accidents. However, due to the unavoidable presence of flammable materials, e.g. Electrical equipment, cables, gas, flammable liquids, …), it is impossible to prevent fires in these plants . Fire at nuclear power plants may be caused directly or indirectly by one or more initiating events, which the following accidents in turn would threaten the safety of the plant. In this project,... 

Safety integrity level that is a basis for relative risk reduction, is defined by the safety function assessment. Among risk assessment methods, risk graph is known as a qualitative method, which has been used by safety experts due to its simple structure. But this feature doesn't stop them from checking out the structure in a careful way. At first by specifying the basic parameters of the risk graph method, it has been defined that safety and control systems that their functions are independent from alarms and human consciousness, are not considered in this method, so a new parameter has been introduced to show the effects of mentioned control and safety systems. On the other hand, in order... 

Sour Gas is more dangerous than sweet gas because of its hydrogen sulfide contents. So it requires more safety considerations. In this project, the effect of wall thickness and design factor of pipeline on the safe distance was examined by using risk assessment method. The safe distance tables for 4 pipelines with different wall thicknesses and design factors were prepared based on operating pressure, pipe diameter and hydrogen sulfide concentration in gas by using PHAST and PHAST RISK softwares. In this project, the depth of cover parameter was considered in safe distance determination. Also the leak of sour gas was simulated by using...