Layouts of Unit-Load Warehouses with Multiple Slot Heights

2020 ◽  
Vol 54 (5) ◽  
pp. 1332-1350
Author(s):  
Luis F. Cardona ◽  
Kevin R. Gue
Keyword(s):  
Simulation Model ◽  
Travel Time ◽  
Operating Costs ◽  
Unit Load ◽  
Space Utilization ◽  
Duration Of Stay

We describe a method to generate layouts for unit-load warehouses that use multiple slot heights as a way to maximize warehouse space utilization. The problem has two parts: slots must be arranged into rack-bays, and rack-bays must be arranged into a layout. We describe two methods for the first subproblem, depending on whether the warehouse has directed picking and put-away. For the second, we describe a simulation model and a greedy procedure based on the duration-of-stay storage policy. We observe significant benefits of using multiple slot heights in unit-load warehouses with respect to footprint, expected travel time, and cost of racking. For a typical warehouse, we expect space savings between 25% and 35%, depending on the number of slot types, and savings of between 15% and 25% in annual operating costs.

scholarly journals A Simulation Approach for Optimising Energy-Efficient Driving Speed Profiles in Metro Lines

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6038
Author(s):  
Mariano Gallo ◽  
Marilisa Botte ◽  
Antonio Ruggiero ◽  
Luca D’Acierno
Keyword(s):  
Energy Consumption ◽  
Simulation Model ◽  
Travel Time ◽  
Energy Efficient ◽  
Energy Savings ◽  
Simulation Software ◽  
Gradient Algorithm ◽  
Simulation Approach ◽  
Driving Speed ◽  
Optimisation Model

We propose a model for optimising driving speed profiles on metro lines to reduce traction energy consumption. The model optimises the cruising speed to be maintained on each section between two stations; the functions that link the cruising speed to the travel time on the section and the corresponding energy consumption are built using microscopic railway simulation software. In addition to formulating an optimisation model and its resolution through a gradient algorithm, the problem is also solved by using a simulation model and the corresponding optimisation module, with which stochastic factors may be included in the problem. The results are promising and show that traction energy savings of over 25% compared to non-optimised operations may be achieved.

Travel time estimation in urban networks using limited probes data

2011 ◽  
Vol 38 (3) ◽  
pp. 305-318 ◽  
Author(s):  
Mohamed El Esawey ◽  
Tarek Sayed
Keyword(s):  
Simulation Model ◽  
Travel Time ◽  
Network Performance ◽  
Time Estimation ◽  
Performance Measure ◽  
Estimation Accuracy ◽  
Travel Time Estimation ◽  
Travel Times ◽  
Time Data ◽  
Travel Time Data

Travel time is a simple and robust network performance measure that is well understood by the public. However, travel time data collection can be costly especially if the analysis area is large. This research proposes a solution to the problem of limited network sensor coverage caused by insufficient sample size of probe vehicles or inadequate numbers of fixed sensors. Within a homogeneous road network, nearby links of similar character are exposed to comparable traffic conditions, and therefore, their travel times are likely to be positively correlated. This correlation can be useful in developing travel time relationships between nearby links so that if data becomes available on a subset of these links, travel times of their neighbours can be estimated. A methodology is proposed to estimate link travel times using available data from neighbouring links. To test the proposed methodology, a case study was undertaken using a VISSIM micro-simulation model of downtown Vancouver. The simulation model was calibrated and validated using field traffic volumes and travel time data. Neighbour links travel time estimation accuracy was assessed using different error measurements and the results were satisfactory. Overall, the results of this research demonstrate the feasibility of using neighbour links data as an additional source of information to estimate travel time, especially in case of limited coverage.

scholarly journals A simulation approach for aircraft cargo loading considering weight and balance constraints

2021 ◽  
Vol 3 (1) ◽  
pp. 21-31
Author(s):  
Erdem Agbas ◽  
Ali Osman Kusakci
Keyword(s):  
Simulation Model ◽  
Real World ◽  
Performance Indicators ◽  
Center Of Gravity ◽  
Air Cargo ◽  
Unit Load ◽  
Loading Process ◽  
Cargo Transport ◽  
Manual Methods ◽  
The Given

Air cargo transport is a growing industry in parallel with the growth in world trade and e-commerce. The global air cargo transport traffic getting busier, the importance of timely loading with minimum error is increasing. Therefore, digitalization of the air cargo loading process is needed. Assignment of Unit Load Devices (ULDs) to the specific positions on the freighter is performed by loadmasters by manual or semi-manual methods. This study aims to design a simulation model, which performs the ULD assignment automatically by simulating the loading process performed by the experienced loadmasters under the weight and balance constraints. The SEMMA (sample, explore, modify, model, assess) model is used while generating the simulation model. Fifty real-world loading orders were used to assess the performance of the model. The ULD assignment process by the simulation model and the loadmasters using semi-manual loading were compared with regard to time and center of gravity performance indicators. The results demonstrated that the simulation model can load all the given sets of ULDs, as efficiently as a loadmaster with a similar center of gravity in a shorter period of time. In conclusion, the proposed simulation model provides an efficient solution to the ULD assignment problem. However, the base model generated may be improved to address various real-world scenarios

scholarly journals Simulation model for the coordination of environmental and economic interests

2022 ◽  
Vol 962 (1) ◽  
pp. 012011
Author(s):  
I P Glazyrina ◽  
S M Lavlinskii
Keyword(s):  
Mineral Resource ◽  
Simulation Model ◽  
Mining Industry ◽  
Target Function ◽  
The State ◽  
Operating Costs ◽  
Financial Resources ◽  
Economic Interests ◽  
Stackelberg Model ◽  
Resource Sector

Abstract The purpose of the work is to develop a simulation model that could be used as the basis for a practical methodology for forming a ‘green’ program for the development of mining industry. For this purpose, the Stackelberg model and the apparatus of two-level mathematical programming are used and thus take into account the peculiarities of the hierarchy of interaction between the state and the private investor in the mineral resource sector. The obtained data make it possible to determine the quantitative parameters of expenditures of public financial resources, at which the target function of the state reaches its maximum. It is concluded that the strategy of choosing higher operating costs and, as a result, lower postproject environmental losses is preferable for both the state and the investor.

Innovative Estimating Travel Time Model for Dual-Command Cycle Time of Stewart-Gough Platform in Automated Storage/Retrieval Systems

2012 ◽  
Author(s):  
Muawia Ramadan ◽  
Bashir Salah ◽  
Bernd Noche
Keyword(s):  
Travel Time ◽  
Unit Load ◽  
Time Model ◽  
Parallel Wire ◽  
Storage And Retrieval ◽  
Retrieval Systems ◽  
Automated Storage ◽  
Stewart Gough Platform ◽  
Numerical Case Study

The travel time models of automated storage and retrieval systems (AS/RS’s) have been widely used in distribution and production environments. This paper extends previous work presented on impact design aspects of automated storage/retrieval systems by determining the expected cycle travel time for single command. Our new study improves the throughput performance rate of new AS/RS’s design on cycle travel time that will be specified by estimating travel time for dual command to serve as storage and retrieval (S/R) machine using a parallel wire-based Stewart-Gough platform (parallel wire robot). This improved efficiency in new design is called Stewart-Gough Platform based Automated Storage and Retrieval Systems (SGP-AS/RS’s). A numerical case study has been presented to clarify the travel time analysis based on mini unit-load storage and retrieval system. The improved throughput has been demonstrated by making a comparison between the conventional AS/RS results and the (SGP-AS/RS’s) results in the numerical case study. The effectiveness and ability of (SGP-AS/RS’s) has been proofed by determining the expected travel time for single command and dual command for random and classed-based analysis of storage assignment.

scholarly journals On the Effects of Various Measures of Performance Selections on Simulation Model Calibration Performance

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Chen Wang ◽  
Chengcheng Xu
Keyword(s):  
Simulation Model ◽  
Travel Time ◽  
Model Calibration ◽  
Lane Change ◽  
Traffic Conditions ◽  
Average Travel Time ◽  
Traffic Conflicts ◽  
Headway Distribution ◽  
Multicriteria Calibration ◽  
Measures Of Performance

Objective. This paper examines the effects of various measures of performance (MOP) selections on simulation model calibration performance, in terms of reflecting actual traffic conditions and vehicle interactions. Method. Two intersections in Shanghai were selected for simulation model calibration, one for testing and another for validation. Three effective MOPs were utilized, including average travel time (i.e., time passing the intersection), average queue length, and vehicle headway distribution. The counts of three types of traffic conflicts (i.e., crossing, rear-end, and lane change) were used as safety MOPs. Those MOPs, as calibration objectives, were examined and compared. Results. The results of the testing site showed that different effective MOPs had their own advantages: average travel time appeared to be the best in reflecting lane change and rear-end conflicts while headway distribution performed the best consistency between simulated and actual crossing conflicts. Compared to the safety MOPs, average travel time and headway distribution still performed better, in terms of resulting in more similar simulated conflict metrics (e.g., TTC, PET) to actual ones. A multicriteria calibration strategy based on average travel time and headway distribution generally had better performances in reflecting actual traffic conditions and vehicle interactions than using any single effective or safety MOP. Similar results were found for the validation site. Conclusion. To simulate actual traffic conditions and vehicle interactions, multiple effective MOPs could be simultaneously considered for model calibration, instead of using safety MOPs.

Sign in / Sign up

Export Citation Format

Share Document