Search for: time-lags
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    An experimental study of time lag for pressure measurement in different tubes

    , Article Amirkabir (Journal of Science and Technology) ; Volume 16, Issue 61 B , 2005 , Pages 127-137 ; 10150951 (ISSN) Mani, M ; Soltani, M. R ; Tolouei, E ; Sharif University of Technology
    Determination of the time lag caused by utilization of different tubes to measure pressure on the surface of a wind tunnel model is an important problem in the field of aerodynamic especially for unsteady measurements where the pressure signature changes continuously with time. In this investigation the time required for the applied pressure at one end of different tubes to reach its original value (applied pressure) at the other end has been measured. Three plastic tubes and two polyethylene tubes with different lengths and different inner diameters; L=2, 5 and 10 m, d=1, 2 and 4 mm, were used to study the time lag. Experimental data show that the response time in a pressure measuring... 

    Impact of reduced frequency on the time lag in pressure distribution over a supercritical airfoil in a pitch-pause-return motion

    , Article Chinese Journal of Aeronautics ; Volume 32, Issue 2 , 2019 , Pages 243-252 ; 10009361 (ISSN) Eslami, H. Z ; Davari, A. R ; Soltani, M. R ; Sharif University of Technology
    Chinese Journal of Aeronautics  2019
    Effects of reduced frequency, stop angle, and pause duration have been studied on a thin supercritical airfoil undergoing a pitch-pause-return motion, which is one of the classic maneuvers introduced by the AIAA Fluid Dynamics Technical Committee. Experiments were conducted in a low-speed wind tunnel at both a constant mean angle of attack and an oscillation amplitude with a reduced frequency ranging from 0.01 to 0.12. The desired stop angles of the airfoil were set to occur during the upstroke motion. The unsteady pressure distribution on the airfoil was measured for below, near, and beyond static stall conditions. Results showed that the reduced frequency and stop angle were the dominant... 

    Cost derivation of a dyadic supply chain with time lag information sharing

    , Article 37th International Conference on Computers and Industrial Engineering 2007, Alexandria, 20 October 2007 through 23 October 2007 ; Volume 3 , 2007 , Pages 1709-1714 ; 9781627486811 (ISBN) Sajadifar, S. M ; Haji, R ; Shenas, N. Y ; Sharif University of Technology
    In this paper we consider a dyadic supply chain consisting of one warehouse and one retailer with information exchange. We assume that the demand process to the retailer is a Poisson process and transportation times are constant. The retailer applies continuous review (R,Q)-policy. When the retailer's inventory position reaches R+s she sends information about her customer demand and inventory activities to the supplier. The supplier receives this information after a constant time lag. The supplier starts with m initial batches (of size Q), and places an order in a batch of size Q to an outside source immediately after receiving the information from the retailer. In this paper using the idea... 

    Resource-constrained project scheduling problem with flexible work profiles: A genetic algorithm approach

    , Article Scientia Iranica ; Volume 17, Issue 1 E , JANUARY-JUNE , 2010 , Pages 25-35 ; 10263098 (ISSN) Ranjbar, M ; Kianfar, F ; Sharif University of Technology
    This paper deals with the resource-constrained project scheduling problem with flexible work profiles. In this problem, a project contains activities interrelated by finish-start-type precedence constraints with a time lag of zero. In many real-life projects, however, it often occurs that only one renewable bottleneck resource is available and that activities do not have, a fixed prespecified duration and associated resource requirement, but a total work content, which essentially indicates how much work has to be performed on them. Based on this work content, all feasible work profiles have to be specified for the activities, each characterized by a, fixed duration and a resource... 

    A hybrid scatter search for the discrete time/resource trade-off problem in project scheduling

    , Article European Journal of Operational Research ; Volume 193, Issue 1 , 2009 , Pages 35-48 ; 03772217 (ISSN) Ranjbar, M ; De Reyck, B ; Kianfar, F ; Sharif University of Technology
    We develop a heuristic procedure for solving the discrete time/resource trade-off problem in the field of project scheduling. In this problem, a project contains activities interrelated by finish-start-type precedence constraints with a time lag of zero, which require one or more constrained renewable resources. Each activity has a specified work content and can be performed in different modes, i.e. with different durations and resource requirements, as long as the required work content is met. The objective is to schedule each activity in one of its modes in order to minimize the project makespan. We use a scatter search algorithm to tackle this problem, using path relinking methodology as... 

    A branch and bound algorithm for the weighted earliness-tardiness project scheduling problem with generalized precedence relations

    , Article Scientia Iranica ; Volume 16, Issue 1 E , 2009 , Pages 55-64 ; 10263098 (ISSN) Afshar Nadjafi, B ; Shadrokh, S ; Sharif University of Technology
    In this paper, an exact solution procedure is presented for the Weighted Earliness-Tardiness Project Scheduling Problem (WETPSP) with Generalized Precedence Relations (WETPSP-GPR), taking into account the time value of money (WETPSPDC-GPR) and a fixed deadline for the project. The WETPSP-GPR extends the WETPSP to arbitrary minimal and maximal time-lags between the starting and completion times of activities. We present a new depth-first Branch and Bound (B&B) algorithm for an extended form of the problem, in which the time value of money is taken into account by discounting cash flows, and minimum, as well as maximum, time-lags between different activities may be given. The algorithm is...