Design and storage cycle time analysis for the automated storage system with a conveyor and a rotary rack

In this paper, we analyse the performance of an automated Work-In-Process (WIP) storage system consisting of a conveyor and a rotary rack. The stability condition and the expected storage cycle time are derived to analyse the performance of the WIP storage system. As part of the storage cycle time analysis, the derived expected waiting times at the conveyor and the rotary rack are important performance measures that can be used for buffer-sizing purpose in such systems. Given the fixed storage space of the rotary rack, we also develop a heuristic approach to determine the near optimum ‘shape’ of the rotary rack so that the expected storage cycle time is minimized. Numerical results are presented to examine the storage cycle time model and the proposed shape design. The analytical model introduces a simple approach over simulation with acceptable accuracy; it is useful when designing such WIP storage systems. Moreover, it can be expanded to model more complex systems. The derived model also provides insightful information on the design parameters that a typical simulation tool can hardly provide.     

Minimizing response time in a two-stage supply chain system with variable lead time and stochastic demand

We consider customer response time minimization in a two-stage system facing stochastic demand. Traditionally, the objective of representative mathematical models is to minimize costs related to production, inventory holding, and shortage. However, the highly competitive market characterized by impatient customers warrants the inclusion of costs related to customer waiting. Therefore we investigate a supply chain system in an uncertain demand setting that encompasses customer waiting costs as well as traditional plant costs (i.e. production and inventory costs). A representative expected cost function is derived and the closed form optimal solution is determined for a general demand distribution. We also provide examples to illustrate results for some common probability distributions. Our results indicate significant cost savings under certain assumptions when comparing solutions from the proposed model to the traditional newsvendor order/production quantity.     

A matching-based approach for solving a delivery/pick-up vehicle routing problem with time constraints

Summary In this paper we deal with the following special vehicle routing problem with time window constraints: Given a non-homogeneous fleet of vehicles and a fixed set of customers, during one time period, i.e. a day or a week, these customers have to be delivered in the first half of the period with a certain amount of goods. Thereby delivery may start at timet _start say at the depot and for every customer there is a so-called cut-off-time for the latest possible delivery. In addition to travel time there is a certain delivery-time associated with every customer. In the second half of the time period the vehicles have to pick-up certain amounts of goods and to ship them to the depot. Again there is a cut-off time for the earliest possible pick-up and a certain time-span consumed for every pick-up. We show how this problem can be formulated as a (highdimensional) set partitioning problem with two additional nontrivial sets of side-constraints. Assuming that the number of customers that can be served by a single vehicle on a delivery or pick-up-pass is at most two, the problem reduces to a matching problem with side-constraints. Although the problem is still NP-complete it becomes practicable in the sense that by relaxation and applying effective optimization techniques from non-smooth optimization and efficient matching software good approximate solutions are constructed in acceptable time.This work was partially supported by a grant from the Deutsche Forschungsgemeinschaft (DFG)     

Active optical system for variable view imaging of micro objects with emphasis on kinematic analysis

Insufficient vision information, such as occlusion, low resolvability, and a small field of view, represent important issues in microassembly and micromanipulation. We propose an active optical system to solve problems related to insufficient vision information through the integration of robotics and optics technologies. The proposed system integrates a double-prism system and a scanning mirror system to supply a compact flexible view. The kinematics of the imaging system is analyzed based on a simplified model initially to investigate the workspace and identify the kinematic performance. A more rigorous analysis of kinematics of the system is then made based on the ray tracing method. The simulation results based on the preliminary design are provided for investigating the workspace and demonstrating the capability of the system in imaging with variable views.     

Common-use check-in counter reassignments with a variable number of service lines and variable length of time window

In the real world, there are a number of common factors that can cause perturbations at check-in counters, such as an airport closure, a temporary power failure, crashing of the counter computer, baggage conveyor belt malfunctions, and so on, forcing the airport authority to reassign flights to new check-in counters. In this study, we develop a model and a solution method to solve common-use check-in counter reassignment problems with a variable number of service lines and a variable length of time window. To test how well the proposed model and the solution method can be applied to the real world, we perform numerical tests based on a hypothetical incident in relation to a Taiwan airport’s operations. The test results show that the model and solution would be useful for the airport authority in actual operations.     

Forced synchronization in a system with unstable cycle

The dynamics of a system with unstable limiting cycle under the action of a periodic sequence of delta pulses is considered. It is shown that stable quasiperiodic regimes and phase lock regimes (synchronization) can be observed within a narrow range of parameters of the external signal.     

Decomposition of a layer of variable mass with progressive energy release

A self-similar solution with shock wave is found for the Lagrange equations of motion of a perfect gas in which energy is released. This solution is continued by means of a difference scheme.     

Optimisation of the multi-depots pick-up and delivery problems with time windows and multi-vehicles using PSO algorithm

Many sectors in the transport industry are concerned about the vehicle routing problem (VRP), hence the growing interest of researchers for this type of problem and its variants. This is due essentially to its many real applications in logistics for the transport of goods. The originality and contribution of our work is that we have dealt a problem that combines several variants: multiple vehicles (m), multiple depots (MD), pickup and delivery problem (PDP) with time windows (TW). Hence the notation of our problem: m-MDPDPTW. In this paper, we present the m-MDPDPTW, which is an optimisation problem belonging to the category of NP Hard problems. This problem must meet requests for transport between customers and suppliers satisfying precedence, capacity and time constraints. The goal is to find the best solution, which is the best route minimising the total travelled distance. To solve and optimise our m-MDPDPTW, we have developed a new algorithm based on the particle swarm optimisation (PSO) method. The performance of this new approach is tested on data set instances of Li and Lim's benchmark problems in which we have added multiple depot locations. Comparing with prior works, our proposed approach gave better results by decreasing the distance for several studied instances.     

The up and down time distribution in a 1 out of n system with general life time and repair time distributions

In repairable systems with redundancy, failed units can be replaced by spare units in order to reduce system down time. The failed units are sent to a repair shop or manufacturer for maintenance and are subsequently returned for re-use.In this paper we consider a 1 out of n system with cold standby and we assume that repaired machines are as ‘good-as-new’. We derive an approximation method for the distribution of the up time and the down time of the system in case of a general failure distribution and a general repair time distribution. This allows the model to be used in a wide variety of applications.     

刮板输送机用隔爆型变频调速三相异步电动机设计

基于煤矿井下变频调速装置与电动机一体式的隔爆型变频调速三相异步电动机实现高效、节能的研发项目,根据传统的感应电动机电磁计算程序增加变频调速电动机的计算方案,并结合ANSOFT 2D有限元针对三相异步电动机的数值分析方法,进行设计核算。详细论述了变频电机的变频调速原理、控制策略,并给出实际样机,介绍其设计与制造技术。     

Angular factor determination for a radiative conveyor drying system with diffuse and specular reflection

A method is given for determining the angular radiation intensity factors for thermal drying volumes with cylindrical forces.     

Transport of radiation energy in materials with variable optical properties

A solution is presented for the problem of the distribution of absorbed energy and of the fluxes of monochromatic and integrated radiation in actual absorbing and scattering materials with optical properties which vary along a coordinate.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 3, pp. 389–396, March, 1976.     

Cooling performance of a variable speed CO2 cycle with an electronic expansion valve and internal heat exchanger

The cooling performance of a CO₂ cycle must be improved to develop a competitive air-conditioning system with the conventional air-conditioners using HFCs. In this study, the cooling performance of a variable speed CO₂ cycle was measured and analyzed by varying the refrigerant charge amount, compressor frequency, EEV opening, and length of an internal heat exchanger (IHX). The basic CO₂ system without the IHX showed the maximum cooling COP of 2.1 at the compressor discharge pressure of 9.2 MPa and the optimum normalized charge of 0.282. The cooling COP decreased with the increase of compressor frequency at all normalized charges. The optimum EEV opening increased with compressor frequency. Simultaneous control of EEV opening and compressor frequency allowed optimum control of the compressor discharge pressure. The optimal compressor discharge pressure of the modified CO₂ cycle with the IHX was reduced by 0.5 MPa. The IHX increased the cooling capacity and COP of the CO₂ cycle by 6.2–11.9% and 7.1–9.1%, respectively, at the tested compressor frequencies from 40 to 60 Hz.     

Guide path design and location of load pick-up/drop-off points for an automated guided vehicle system

The guide path layout for an automated guided vehicle system (AGVS) is a critical component in the overall design of a flexible manufacturing system (FMS) that utilizes AGVs for materials handling. Not only does it affect the total distance travelled by the vehicles but it also affects vehicle requirements and space utilization. In this study, the problem of selecting the guide path as well as the location of pick-up and drop-off points for outward and inward bound parts to departments is addressed. The problem is modelled and solved as a linear integer program with the objective of minimizing the total distance travelled.     

Life cycle energy and carbon footprint analysis of photovoltaic battery microgrid system in India

Electricity supply in India is from a centralized grid. Many parts of the country experience grid interruptions. Life cycle energy and environmental analysis has been done for a 27 kWp photovoltaic system which acts as grid backup for 3 h outage in an Indian urban residential scenario. This paper discusses energy requirements and carbon emission for a PV storage system for five different battery technologies in Indian context. This can be used as a metric for comparative analysis for new batteries, with an undeveloped market. The energy requirements for the components are quantified and are compared in terms of energy payback time (EPBT) and Net Energy Ratio (NER). All the calculations are done for Indian context. EPBT is found to be in the range of 2–4.5 years for all the systems, while NER is in the range of 6.6–2.52. NaS has the highest emission factor of 0.67 kgCO₂/kWh and the least for NiCd (0.091 kgCO₂/kWh). These factors can be used to select a PV battery option and to target selection of materials and systems based on the reported values.     

Optimal cycle time and inventory decisions in coordinated and non-coordinated two-echelon inventory system under inflation and time value of money

In this paper, a mathematical model is developed for a coordinated and non-coordinated two-echelon inventory system comprising of a single manufacturer and a single retailer. The objective of the model is to demonstrate the optimality of cycle time and inventory decisions under the phenomena of different inflation rates at the manufacturer and retailer points. Also, it is aimed at determining the annual net revenue of the supply chain (SC). In the proposed model, the present value of the inflated ordering/set-up costs, purchase/unit costs, carrying costs and the gross revenue is computed for the retailer, manufacturer and the SC. A numerical example is devised to illustrate the optimality of decision variables and the objective function. Also, the sensitivity analysis is carried out. Results show that the present value of the annual net revenue of the retailer, manufacturer and SC decreases with increased inflation rate at the retailer and decreased inflation rate at the manufacturer simultaneously.     

Approximate analytical solutions for self-similar flows of a dusty gas with variable energy

Approximate analytical solutions are obtained for the unsteady one dimensional self-similar flow behind a strong shock wave propagating in a mixture of a gas and small solid particles at rest. It is assumed that variable energy is deposited at the shock and the total energy of the flow behind the shock is assumed to be varying with shock radius obeying a power law. The initial density of the medium is taken to be a constant. A simple integral method is employed to study the adiabatic and isothermal flows. The effect of the parameter characterizing the variation of total energy of the flow, on solutions of the flow field is investigated in detail. It as also shown that the similarity solutions of perfect gas with variable energy can be obtained as a particular case of this problem by taking the initial volume fraction of solid particles in the mixture as zero. Approximate solutions are compared with the numerical solutions and found a good agreement between them.