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Integrating Machine Reliability and Preventive Maintenance Planning in Manufacturing Cell Design
Das, Kanchan,Lashkari, R.S.,Sengupta, S. Korean Institute of Industrial Engineers 2008 Industrial Engineeering & Management Systems Vol.7 No.2
This paper presents a model for designing cellular manufacturing systems (CMS) by integrating system cost, machine reliability, and preventive maintenance (PM) planning. In a CMS, a part is processed using alternative process routes, each consisting of a sequence of visits to machines. Thus, a level of 'system reliability' is associated with the machines along the process route assigned to a part type. Assuming machine reliabilities to follow the Weibull distribution, the model assigns the machines to cells, and selects, for each part type, a process route which maximizes the overall system reliability and minimizes the total costs of manufacturing operations, machine underutilization, and inter-cell material handling. The model also incorporates a reliability based PM plan and an algorithm to implement the plan. The algorithm determines effective PM intervals for the CMS machines based on a group maintenance policy and thus minimizes the maintenance costs subject to acceptable machine reliability thresholds. The model is a large mixed integer linear program, and is solved using LINGO. The results point out that integrating PM in the CMS design improves the overall system reliability markedly, and reduces the total costs significantly.
Photoacoustic resonance by spatial filtering of focused ultrasound transducers
Kang, Dongyel,Lashkari, Bahman,Mandelis, Andreas OPTICAL SOCIETY OF AMERICA 2017 Optics letters Vol.42 No.4
<P>The effect of a spherically focused ultrasound (US) transducer (TD) on photoacoustic (PA) measurements is analytically investigated using the concept of a virtual point detector. The derived analytical results indicate that the limited numerical aperture (NA) of the PA detector takes on the role of spatial filtering of the induced PA waves, which leads to the occurrence of a peak frequency in the PA spectrum. The mathematical description of this phenomenon is similar to the result of resonance peaks of light propagation in dielectrics. This PA resonance peak depends on the NA of the US TD and the absorption coefficient of the PA source. Experimentally measured PA spectra from an ink solution using a frequency-domain PA system verify the PA resonance effect. Finally, we discuss the possibility that previously reported PA resonances interpreted as PA source viscosity might be actually caused by the US TD's spatial filtering. (C) 2017 Optical Society of America</P>
DABCO-Catalyzed the Synthesis of Densely Functionalized Cyclohexanones in a Benign Manner
Nourallah Hazeri,Mojtaba Lashkari,Maryam Fatahpour,Mahla Sheikhveisi 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.8
In this study, a robust DABCO-catalyzed method has been reported for the reaction of readily available material, including various aromatic/aliphatic aldehydes and acetoacetanilide affording N,N?-diaryl-2-aryl-6-hydroxy-6-methyl-4-oxocyclohexane-1,3-dicarboxamides. The reaction proceeds at 50 °C under solvent-free conditions via a one-pot pseudo-three-component reaction to yield functionalized cyclohexanones containing four quaternary stereogenic centers. Simple reaction conditions, moderate-to-high yields of product, no need of column chromatographic purification, eco-friendliness, shorter reaction time, and simple work-up has transformed this method an interesting route to the available procedures. The stereoselectivity of compounds was envisaged with crystallography and NMR spectroscopy.
Three dimensional analysis of temperature effect on control rod worth in TRR
Maedeh Yari,Ahmad Lashkari,S. Farhad Masoudi,Mirshahram Hosseinipanah 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.8
In this paper, three-dimensional neutronic calculations were performed in order to calculate the dependencyof CRW on the temperature of fuel and moderator and the moderator void. Calculations wereperformed using the known MTR_PC computer codes in the core configuration 61 of TRR. The dependencyof CRW on the fuel temperature in the range of 20e340 C and the moderator temperature ofeach control rods were studied. Based on the positions of the control rods, the calculations were performedin three different cases, named case A, B and C. By the results, the worth of each control rodsincreases by increasing of the coolant temperature in all methods, however, the total CRW is somewhatindependent of the fuel temperature. In addition, the results showed that the variation of CRW versusdensity depends on the positions of the control rods and the most change in CRW in the coolant temperature,20e100 C (279 pcm), belongs to SR4. Finally the effect of void on CRW was studied fordifferent void fraction in coolant. The most worth change is about $2 for 40% void fraction related to SR1and SR3 in case B. For 40% void fraction, the total CRW increases about $7.5, $6 and $7 in cases, A, B and C,respectively
Disaster Assessment and Mitigation Planning
Kanchan Das,R. S. Lashkari,N. Biswas 대한산업공학회 2013 Industrial Engineeering & Management Systems Vol.12 No.4
This paper proposes a mathematical modeling-based approach for assessing disaster effects and selecting suitable mitigation alternatives to provide humanitarian relief (HR) supplies, shelter, rescue services, and long-term services after a disaster event. Mitigation steps, such as arrangement of shelter and providing HR items (food, water, medicine, etc.) are the immediate requirements after a disaster. Since governments and non-governmental organizations (NGOs) providing humanitarian aid need to know the requirements of relief supplies and resources for collecting relief supplies, organizing and initiating mitigation steps, a quick assessment of the requirements is the precondition for effective disaster management. Based on satellite images from weather forecasting channels, an area/dimension of the disaster-affected zones and the extent of the overall damage may often be obtained. The proposed approach then estimates the requirements for HR supplies, supporting resources, and rescue services using the census and other government data. It then determines reliable transportation routes, optimum collection and distribution centers, alternatives for resource support, rescue services, and long-term help needed for the disaster-affected zones. A numerical example illustrates the applicability of the model in disaster mitigation planning.
Neutronic analysis of control rod effect on safety parameters in Tehran Research Reactor
Mina Torabi,A. Lashkari,Seyed Farhad Masoudi,Somayeh Bagheri 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.7
The measurement and calculation of neutronic parameters in nuclear research reactors has an importantinfluence on control and safety of the nuclear reactor. The power peaking factors, reactivity coefficientsand kinetic parameters are the most important neutronic parameter for determining the state of thereactor. The position of the control shim safety rods in the core configuration affects these parameters. The main purpose of this work is to use the MTR_PC package to evaluate the effect of the partiallyinsertion of the control rod on the neutronic parameters at the operating core of the Tehran ResearchReactor. The simulation results show that by increasing the insertion of control rods (bank) in the core,the absolute values of power peaking factor, reactivity coefficients and effective delayed neutron fractionincreased and only prompt neutron life time decreased. . In addition, the results show that the changes ofmoderator temperature coefficients value versus the control rods positions are very significant. Theaverage value of moderator temperature coefficients increase about 98% in the range of 0e70% insertionof control rod
Integrating Machine Reliability and Preventive Maintenance Planning in Manufacturing Cell Design
Kanchan Das,R.S. Lashkari,S. Sengupta 대한산업공학회 2008 Industrial Engineeering & Management Systems Vol.7 No.2
This paper presents a model for designing cellular manufacturing systems (CMS) by integrating system cost, machine reliability, and preventive maintenance (PM) planning. In a CMS, a part is processed using alternative process routes, each consisting of a sequence of visits to machines. Thus, a level of ‘system reliability’ is associated with the machines along the process route assigned to a part type. Assuming machine reliabilities to follow the Weibull distribution, the model assigns the machines to cells, and selects, for each part type, a process route which maximizes the overall system reliability and minimizes the total costs of manufacturing operations, machine underutilization, and inter-cell material handling. The model also incorporates a reliability based PM plan and an algorithm to implement the plan. The algorithm determines effective PM intervals for the CMS machines based on a group maintenance policy and thus minimizes the maintenance costs subject to acceptable machine reliability thresholds. The model is a large mixed integer linear program, and is solved using LINGO. The results point out that integrating PM in the CMS design improves the overall system reliability markedly, and reduces the total costs significantly.