Simulation-based Modelling Approach Research Articles

A simulation-based modelling approach for a production line with nested-loop work sequences

ABSTRACT Critical for current situation analysis in lean initiatives, establishing standardised work can be challenging due to the intricacies involved in documenting complex routine work, mainly characterised by nested-loop work sequences. This study aims to extend the existing methods of establishing standardised work and analysing a production line for complex routine work. Novel concepts and terminologies are introduced, combining the existing methods into a modelling approach capable of addressing all complex features simultaneously. A standardised work sequence diagram is defined as a fundamental representation, forming the basis for a new simulation-based modelling approach. Described, validated, and applied through an industrial case study, the proposed approach is confirmed effective, achieving an average relative combined cycle time of 0.99, compared to the expected value of 1. The resulting redesign of standardised work significantly improves line efficiency from 53% to 79%, with a manpower reduction from 8 to 4 workers.

Mathematical modelling of gene delivery in patients with haemophilia B

Haemophilia B is a bleeding disorder resulting from a deficiency of coagulation factor IX (FIX). Although gene therapy is a potentially curative treatment option, optimising the dosing of therapeutic genes for patients remains a challenge. Detailed simulation of gene delivery systems is required for an improved understanding of the system. Hence, the purpose of this paper is to develop a modelling framework to predict the physiological response of a subject affected by type B haemophilia to a dose of the vector. To address this, an integrated pharmacokinetic/pharmacodynamic (PK/PD) modelling platform was developed based on in vivo clinical data for three patients with severe haemophilia B, whose functional plasma levels of FIX are less than 1% of the normal value. The plasma FIX activity was considered as the pharmacological effect, while the level of serum alanine aminotransferase (ALT) demonstrated the hepatocellular toxicity. Both an individual-based modelling approach and a population modelling approach were used to estimate the physiological parameters of the developed PK/PD models. The models were then validated using data from the clinical study before being used in a simulation-based modelling approach to provide dosing recommendations. The results obtained from the study demonstrate a good prediction of the pharmacokinetics and pharmacodynamics of the vector. Model-based simulations were subsequently performed to guide initial dose selection to provide clinicians with better tools to simplify the decision-making process for designing more effective treatment plans.

Analyzing the Impact of Strategies for Separating Trucks and Cars: IH 20 Truck-Only Lane Case Study

This research examined the use of truck-only lanes to separate truck freight traffic from general passenger traffic along the 32-mi interstate highway (IH) 20 corridor between Dallas and Fort Worth, TX, United States. The corridor was selected because of its high truck percentage, locations of complex weaving and interactions between trucks and automobiles, and grade change issues that affect truck performance and raise safety concerns. The simulation-based modeling approach leveraged both mesoscopic and microscopic modeling methods. Dynamic traffic assignment (DTA)-based multiresolution modeling examined the regional impact of adding truck-only lanes along the entire IH 20 study corridor, whereas microsimulation focused on a specific segment with distinct operational challenges to model the interaction between truck traffic and general passenger traffic. The DTA mesoscopic model for the region predicted that around 3,000 trucks daily might shift to the dedicated truck-only lanes in both directions giving a travel time saving of 12% in each direction compared with the base case (no build). Focusing on the microsimulation case study to add an inside truck-only climbing lane on a 5-mi segment on IH 20, the model predicted an average increase in speed of 11 mph for eastbound traffic during the morning peak-hour but limited travel time benefits during the morning and afternoon peak hours in either direction. Reasonable safety and operational benefits were observed based on the analysis.

Evaluating the long-term operational performance of a large-scale inland terminal: A discrete event simulation-based modeling approach.

Inland terminals, or dry ports, have played an important role in multimodal transportation networks as transportation hubs that provide connections between seaports and hinterland economies. While important, evaluating the operational performance of a dry port is especially challenging since it depends not only on internal factors, such as the variety and number of container handling equipment (CHE) deployed, but also on other external factors, including changes in transportation policies and container demands experienced by a dry port. To properly evaluate the holistic performance of a dry port while considering all the aforementioned factors, a discrete event simulation (DES) framework is herein developed and applied to the Ladkrabang Inland Container Depot (LICD)-one of the largest dry ports in Southeast Asia-under various operational settings. Despite complicated internal operations, the devised DES framework has shown itself useful in the analyses of LICD, due largely to its flexibility that allows users to include sophisticated operational rules into models. According to our computational results, the current LICD operation is markedly ineffective as the usage rates of all CHE types are relatively low and varied across gate operators-especially the yard truck whose values range between 2.46% and 11.15% on yearly average. We also find that, by redesigning the LICD and its internal operations, the LICD's performance could be substantially enhanced-even with fewer numbers of CHE. Regarding the four CHE types, the reach stacker seems to limit LICD's capability, as its utilization tends to first reach the maximum allowable rate of 75%, while the rubber tyred gantry crane could help boost the usage rate of yard trucks, which, in turn, results in reduced container dwelling times. Nonetheless, the modified LICD could accommodate up to 140% of the current container demand before it experiences operational difficulties induced by the saturation of container flow from rail transportation.

Wealth inequality and social mobility: A simulation-based modelling approach

We design a series of simulation-based thought experiments to deductively evaluate the causal effects of various factors on wealth inequality (the distribution) and social mobility (dynamics of the distribution). We find that uncertainty per se can lead to a “natural” degree of inequality and returns-related factors contribute more than earnings-related factors. Based on these identified factors, we construct an empirical, hybrid agent-based model to match the observed wealth inequality measures of the G7 countries and China. The estimated model can generate a power-law wealth distribution for the rich and a positively sloped intra-generational Great Gatsby curve. We also demonstrate how this hybrid model can be extended to a wide range of questions such as redistributive effects of tax and finance.

Five per cent measurements of the growth rate from simulation-based modelling of redshift-space clustering in BOSS LOWZ

ABSTRACT We use a simulation-based modelling approach to analyse the anisotropic clustering of the BOSS LOWZ sample over the radial range $0.4 \, h^{-1} \, \mathrm{Mpc}$ to $63 \, h^{-1} \, \mathrm{Mpc}$, significantly extending what is possible with a purely analytic modelling framework. Our full-scale analysis yields constraints on the growth of structure that are a factor of two more stringent than any other study on large scales at similar redshifts. We infer fσ8 = 0.471 ± 0.024 at $z$ ≈ 0.25, and fσ8 = 0.430 ± 0.025 at $z$ ≈ 0.40; the corresponding ΛCDM predictions of the Planck cosmic microwave background (CMB) analysis are 0.470 ± 0.006 and 0.476 ± 0.005, respectively. Our results are thus consistent with Planck, but also follow the trend seen in previous low-redshift measurements of fσ8 falling slightly below the ΛCDM + CMB prediction. We find that small- and large-radial scales yield mutually consistent values of fσ8, but there are 1−2.5σ hints of small scales ($\lt 10 \, h^{-1} \, \mathrm{Mpc}$) preferring lower values for fσ8 relative to larger scales. We analyse the constraining power of the full range of radial scales, finding that most of the multipole information about fσ8 is contained in the scales $2 \, h^{-1} \, \mathrm{Mpc}\lesssim s \lesssim 20 \, h^{-1} \, \mathrm{Mpc}$. Evidently, once the cosmological information of the quasi-to-nonlinear regime has been harvested, large-scale modes contain only modest additional information about structure growth. Finally, we compare predictions for the galaxy–galaxy lensing amplitude of the two samples against measurements from SDSS and assess the lensing-is-low effect in light of our findings.

A Dynamic Risk Appraisal Model and Its Application in VTS Based on a Cellular Automata Simulation Prediction.

The successful implementation of Vessel Traffic Services (VTS) relies heavily on human decisions. With the increasing development of maritime traffic, there is an urgent need to provide a sound support for dynamic risk appraisals and decision support. This research introduces a cellular automata (CA) simulation-based modelling approach the objective of which is to analyze and evaluate real-time maritime traffic risks in port environments. The first component is the design of a CA model to monitor ships’ behavior and maritime fairway traffic. The second component is the refinement of the modelling approach by combining a cloud model with expert knowledge. The third component establishes a risk assessment model based on a fuzzy comprehensive evaluation. A typical scenario was experimentally implemented to validate the model’s efficiency and operationality.

A simultaneous optimization model for a heat-integrated syngas-to-methanol process with Kalina Cycle for waste heat recovery

The syngas to methanol (STM) process is an energy-intensive chemical production process, and effective utilization of waste heat can improve energy and economy efficiency. To address current challenges that complex interactions between process synthesis and waste heat recovery are not considered, a novel simultaneous optimization model is proposed for a heat-integrated syngas-to-methanol process with Kalina Cycle (KC) for waste heat recovery, where the identified key parameters of KC and STM are optimized simultaneously without reducing the overall conversion of hydrogen to produce methanol. In developing the model, an enhanced Heat Integration model that considers variable temperatures and flowrates is established to perform thermal cycle optimization with process synthesis by combination of simulation-based modelling approach and equation-based mathematical programming approach. The STM process is synthesized based on a rigorous kinetic modelling approach and the effect of process parameters on waste heat recovery is further analyzed by control variable method. The results show that the net power output of the whole system increases with the decrease of reaction pressure. The optimal medium temperature and inlet temperature of reactor are 180 °C and 160 °C, respectively. Moreover, the presented model can achieve the optimal coupling structure of KC and STM process with the maximized net power output of 15,206.3 kW, which increases by 81.6% compared with that of 8371.4 kW derived by the traditional sequential optimization method in previous study.

Proactive Evaluation of an Operating Room Prototype: A Simulation-Based Modeling Approach.

There is a pressing need to improve safety and efficiency in the operating room (OR). Postsurgical adverse events, such as surgical site infections and surgical flow disruption, occur at a significant rate in industrial countries where a considerable portion of such complications result in death. The aim of the study was to identify an ideal room design that improves the flow of staff members using risk and safety performance measures. Operating room designs were compared by using computer simulation modeling to analyze traffic flow inside an OR. The study was conducted in two phases. A historical data set was first created based on surgical flow data obtained from 23 video observations of actual surgical procedures. A detailed simulation-based model was then developed. As room size increases, staff members have more available space to maneuver in the room, resulting in more distance walked but far fewer undesirable contacts. An angled table orientation is preferred with the circulating nurse workstation at the foot of the OR table, as it provides more space for staff to move across the room without increasing the number of contacts. Furthermore, when the nurse workstation is near the wall, staff members experience fewer undesirable contacts. Simulation modeling was used to assess the impact of OR layout alternatives on three performance metrics, and the medium-sized OR prototype performs well across the metrics. Future research will consider the relative influence of several factors on traffic-based safety and efficiency performance metrics, resulting in a more predictive simulation design model.

Economic decline, incarceration, and mortality from drug use disorders in the USA between 1983 and 2014: an observational analysis

Drug use disorders are an increasing cause of disability and early death in the USA, with substantial geographical variation. We aimed to investigate the associations between economic decline, incarceration rates, and age-standardised mortality from drug use disorders at the county level in the USA. In this observational analysis, we examined age-standardised mortality data from the US National Vital Statistics System and the Institute for Health Metrics and Evaluation, household income data from the US Census Bureau, and county-level jail and prison incarceration data from the Vera Institute of Justice for 2640 US counties between 1983 and 2014. We also extracted data on county-level control variables from the US Census Bureau, the National Center for Health Statistics, and the US Centers for Disease Control and Prevention. We used a two-way fixed-effects panel regression to examine the association between reduced household income, incarceration, and mortality from drug use disorders within counties over time. To assess between-county variation, we used coarsened exact matching and a simulation-based modelling approach. After adjusting for key confounders, each 1 SD decrease in median household income was associated with an increase of 12·8% (95% CI 11·0-14·6; p<0·0001) in drug-related deaths within counties. Each 1 SD increase in jail and prison incarceration rates was associated with an increase of 1·5% (95% CI 1·0-2·0; p<0·0001) and 2·6% (2·1-3·1; p<0·0001) in drug-related mortality, respectively. The association between drug-related mortality and income and incarceration persisted after controlling for local opioid prescription rates. Our model accounts for a large proportion of within-county variation in mortality from drug use disorders (R2=0·975). Between counties, high rates of incarceration were associated with a more than 50% increase in drug-related deaths. Reduced household income and high incarceration rates are associated with poor health. The rapid expansion of the prison and jail population in the USA over the past four decades might have contributed to the increasing number of deaths from drug use disorders. None.

Determining Optimal Tolling Rates for Border Regions Using Dynamic Modeling Methods

Many toll facilities have been faced with traffic shortfalls due to inaccurate and over-forecasted toll revenue projections. Therefore calculating optimal toll rates can be a difficult process. Toll rates are often set to reflect the revenue needed to pay back bonds issued to finance the roadway. This research provides an alternative approach to calculating toll rates where revenue can be maximized while still considering the socio-demographics of the region. Several different approaches used in the border region were explored and compared to field data on an existing toll facility in El Paso, Texas. An innovative simulation-based modeling approach was used to test both static and dynamic pricing algorithms. Static tolling results showed optimal toll rates of $0.14/mile and $0.08/mile for Border Highway West in the westbound and eastbound directions respectively. The Cesar Chavez Highway has optimal toll rates of $0.12 and $0.10/mile in the west and eastbound directions. The dynamic tolling approach showed a max toll rate of $1.56/mile for Cesar Chavez Highway (westbound) during the morning peak period and then incrementally decreased to the minimum toll rate. However, the eastbound direction never increased above the minimum toll rate of $0.08 mile. Border Highway West never increased above the minimum toll rate in either direction. The dynamic tolling algorithm prediction is more representative of the optimal tolling rates for the border region-with the exception of Cesar Chavez Highway westbound.

A Simulation Based Modelling Approach to Jointly Support and Evaluate Spare Parts Supply Chain Network and Maintenance System

This research aims at proposing a simulation-based modelling methodology to support the decision-making process related to the Spare Parts Supply Chain, which is a significant supporting system for maintenance operations in manufacturing systems. The proposed simulation-based modelling approach suits as a useful quantitative methodology to evaluate the performance of the Spare Parts Supply Chain along with its impact on the underlying Maintenance System. The joint modelling and performance evaluation of both the Spare Parts Supply Chain and the Maintenance System allows to support the assessment and selection of policies and strategies related to Spare Parts inventories (e.g. supplying processes, transport decisions and maintenance operations). This methodology may yield a better system costs balance between Spare Parts Supply Chain and Maintenance System, while ensuring desired system service levels. Finally, it worth to be mentioned that this proposed simulation-based approach is suitable to be embedded into a more general decision-making framework to support Spare Parts Supply Chain planning and control.

Smart sealing for magnetorheological fluid actuators

In automotive and industrial environments, magnetorheological fluid–based applications such as clutches and brakes are gaining continuously more attention. However, one of the serious challenges for their application are drag losses at high shear rates. While viscous losses of the magnetorheological fluid can be eliminated by a magnetorheological fluid movement control based on partially filled shear gaps, commonly utilized sealings also cause drag losses based on dry friction. To overcome these challenges, in this contribution, a novel design of sealings for magnetorheological fluid–based actuators is introduced eliminating the adverse drag losses. The intended sealing is based on the magnetorheological fluid itself, positioned in a sealing gap and exposed to a well-defined magnetic stray field of a permanent magnet to prevent any leakage. To eliminate drag torques, a superimposed functional principle with the magnetorheological fluid movement control is utilized. An analytical and a simulation-based modeling approach is proposed describing the torque behavior of the magnetorheological fluid sealing. In experimental investigations, the drag torque-free operation is proven by showing a lossless operation above a defined rotational speed.

Spreading of alien species and diversity of communities

A new species invading a new area may cause a decrease in diversity of the community already present there. Comparison of temporal changes in species diversity of the “new” community (including alien species) with those of the “original” community (including only native species) may clarify our understanding of the effect of alien species. Using a simulation-based modelling approach we considered several scenarios describing the invasion of native communities by alien species and calculated the trends in Shannon-Wiener indices and in the numbers of species of the “original” and “new” communities during the course of the invasion. We found that despite a large increase in the population size of the invasive alien species the diversity of the original community may be little affected. Native species numbers may stay relatively constant for a long time and then suddenly collapse. The results indicate some possibly still concealed consequences of the spread of the invasive ladybird Harmonia axyridis (Pallas).

Genetic confounding of the relationship between father absence and age at menarche

Abstract Research in evolutionary psychology, and life history theory in particular, has yielded important insights into the developmental processes that underpin variation in growth, psychological functioning, and behavioral outcomes across individuals. Yet, there are methodological concerns that limit the ability to draw causal inferences about human development and psychological functioning within a life history framework. The current study used a simulation-based modeling approach to estimate the degree of genetic confounding in tests of a well-researched life history hypothesis: that father absence ( X ) is associated with earlier age at menarche ( Y ). The results demonstrate that the genetic correlation between X and Y can confound the phenotypic association between the two variables, even if the genetic correlation is small—suggesting that failure to control for the genetic correlation between X and Y could produce a spurious phenotypic correlation. We discuss the implications of these results for research on human life history, and highlight the utility of incorporating genetically sensitive tests into future life history research.

SIMULATION OF BRIDGE CONSTRUCTION WORKS: AN EXPLORATORY STUDY

Bridge construction projects are associated with uncertainties partly due to sequencing issues, logistics, interactions, and resource constraints. Their construction is mostly cyclic and repetitive, yet complex, requiring innovative approaches to cope with its management. Construction projects planners seek methods to enable them to schedule bridge construction projects in consideration of these constraining factors. The main objective of this research is to develop a concept of a simulation-based modeling approach. It aimed to decide which data in real systems are important for the modeling of an operation, and in which way they must be gathered to help planners approach a proper simulation-based schedule. A case study project based in New Zealand was selected for this paper. It focuses on developing a resource-based model of bridge construction using a launching-girder construction method, taking into account the complex interactions among the project’s components. The discrete elements within the project and steps taken to develop a model are described in this paper. The study enhances knowledge on the applicability of simulation in repetitive construction operation, which in turn can provide more realistic models for scheduling progress.

A Spatial Microsimulation Approach to Estimating the Total Number and Economic Value of Site Visits in Travel Cost Modelling

This paper presents a simulation-based modelling approach for simultaneously estimating the total number and aggregate value of recreation-related visits to a small-scale community forest in the West of Ireland. Spatially-referenced simulated individuals from a spatial microsimulation model for Ireland (SMILE) who reside within the geographic extent of the market for recreation at the forest are identified using GIS techniques. A travel cost model, adjusted for truncation and endogenous stratification, is estimated for a sample of visitors to the site and transferred across each individual in the simulated population. The SMILE model and GIS-based network analysis are used to derive the appropriate values for the explanatory variables in the transfer. Each simulated individual’s latent demand for visits to the site is predicted and summed, in order to derive aggregate visits and amenity value estimates. The paper makes two principal contributions. First, it sets out a new approach for modelling the geographic extent of the market for recreation using survey data on reported travel distances and GIS techniques. Second, it develops a new simulation-based modelling approach for predicting total site visits at non-priced open-access recreation sites.

Using spatial microsimulation to account for demographic and spatial factors in environmental benefit transfer

This paper presents a simulation-based modelling approach for estimating total visitor numbers and amenity values for prospective non-priced open-access outdoor recreation sites. To begin, the geographic extent of the market for recreation at a policy site is estimated using data from a similar study site. The population residing within this geographic area is simulated using a spatial microsimulation model and GIS techniques and an individual-level ‘visitor arrival function’ is then transferred across this simulated population. This allows the latent demand for visits to the policy site by each simulated individual to be predicted and summed, providing an estimate of the total potential demand for recreation at the site. Combining this with an economic value measure of a visit provides an estimate of the potential amenity value of the policy site. The approach is applied to Moyode Wood, a small-scale forest in the West of Ireland, and estimates the potential total economic value of recreation at €0.4 million for the site. The research represents the first time that spatial microsimulation has been used in environmental benefit transfer and shows how it can be used to control for differences in demographic and spatial factors between study and policy sites. It also demonstrates how individual-level single-site travel cost models estimated using on-site survey data can be used to predict demand at alternative policy sites.

An investigation into effects of long-distance seed dispersal on organelle population genetic structure and colonization rate: a model analysis.

A simulation-based modelling approach is used to examine the effects of stratified seed dispersal (representing the distribution of the majority of dispersal around the maternal parent and also rare long-distance dispersal) on the genetic structure of maternally inherited genomes and the colonization rate of expanding plant populations. The model is parameterized to approximate postglacial oak colonization in the UK, but is relevant to plant populations that exhibit stratified seed dispersal. The modelling approach considers the colonization of individual plants over a large area (three 500 km x 10 km rolled transects are used to approximate a 500 km x 300 km area). Our approach shows how the interaction of plant population dynamics with stratified dispersal can result in a spatially patchy haplotype structure. We show that while both colonization speeds and the resulting genetic structure are influenced by the characteristics of the dispersal kernel, they are robust to changes in the periodicity of long-distance events, provided the average number of long-distance dispersal events remains constant. We also consider the effects of additional physical and environmental mechanisms on plant colonization. Results show significant changes in genetic structure when the initial colonization of different haplotypes is staggered over time and when a barrier to colonization is introduced. Environmental influences on survivorship and fecundity affect both the genetic structure and the speed of colonization. The importance of these mechanisms in relation to the postglacial spread and genetic structure of oak in the UK is discussed.