Design and Simulation of a Digital Twin Mobility Concept: An Electric Aviation System Dynamics Case Study with Capacity Constraints

Vertical mobility, as a commercial service, has been strongly focused on the scheduled volume and long-distance mobility services. Thus, limiting its potential coverage, flexibility, and adaptability with high investments and centralized mobility hubs, called airports. In this context, a customized and on-demand air mobility concept providing high flexibility in location combinations and time schedules appears as an unexplored challenge for regional mobility needs. As a result, the aim of this research is to provide a generic framework for various mobility means as well as to design a holistic air mobility management concept for electric vertical mobility for profitable and sustainable operations by providing a service to society. A system dynamics simulation case study applies the conceptual model for an on-demand air mobility network of electric aircrafts in a regional area considering capacity constraints in vertiports, aircrafts, charging, and parking stations. Thus, bottlenecks and delays can be quantified by using a digital twin tool for customized scenarios. Simulation results show how an optimal maintenance management and redistribution of aircraft units improve service indicators in passenger quantity and customer order lead time as well as reduce aircraft on ground time. As a result, a digital twin air mobility network model with simulation capabilities is a key factor for successful operations.

Shared Manufacturing in A Differentiated Duopoly with Capacity Constraints

This study sets up a differentiated duopoly model considering capacity constraints and shared manufacturing, investigates the equilibrium results, examines the effects of product differentiation and capacity constraints in three scenarios, and compares the equilibrium outcomes in three cases under Cournot and Stackelberg competition. We find that capacity constraints affect the relationships among product differentiation, equilibrium results, and the market share of enterprises. Shared manufacturing impacts the degree of excess capacity, profits, consumer surplus, and social welfare; however, it may sometimes play a negative role in alleviating excess capacity. Moreover, Cournot competition is a better choice for enterprises with capacity constraints compared to Stackelberg competition.

Impact of Price-Sensitive Demand and Premium Payment Scheme on Bullwhip Effect

Bullwhip effect reduces the efficiency, responsiveness, and value of the supply chain. There are some indirect causes like lead time, the number of echelons, and some direct causes of bullwhip effect such as rationing or price variation. Due to capacity constraints, retailers are forced to experience rationing of their demands. Fear of rationing usually gives rise to manipulable demand and hence increases the bullwhip effect. Moreover, if the retailer’s demand is price sensitive then it will cause price variation. The offerings of premium payment by retailers due to unfulfilled demand lure the supplier to extend his existing capacity and to allocate them more supply. In this paper, an attempt has been made to mitigate the impact of the bullwhip effect using a premium payment scheme. A technique has been coined that will help in reducing the bullwhip effect. The increased value of the supply chain on using a premium payment scheme is proof of the reduction of the bullwhip effect. Results are validated through numerical analysis.

Impact of Price Sensitive Demand and Premium Payment Scheme on Bullwhip Effect

Bullwhip effect reduces the efficiency, responsiveness, and value of the supply chain. There are some indirect causes like lead time, the number of echelons, and some direct causes of bullwhip effect such as rationing or price variation. Due to capacity constraints, retailers are forced to experience rationing of their demands. Fear of rationing usually gives rise to manipulable demand and hence increases the bullwhip effect. Moreover, if the retailer’s demand is price sensitive then it will cause price variation. The offerings of premium payment by retailers due to unfulfilled demand lure the supplier to extend his existing capacity and to allocate them more supply. In this paper, an attempt has been made to mitigate the impact of the bullwhip effect using a premium payment scheme. A technique has been coined that will help in reducing the bullwhip effect. The increased value of the supply chain on using a premium payment scheme is proof of the reduction of the bullwhip effect. Results are validated through numerical analysis.

A genetic algorithm for vehicle routing in logistic networks with practical constraints

We optimise a postal delivery problem with time and capacity constraints imposed on vehicles and nodes of the logistic network. Time constraints relate to the duration of routes, whereas capacity constraints concern technical characteristics of vehicles and postal operation outlets. We consider a method which can be applied to a brownfield scenario, in which capacities of outlets can be relaxed and prospective hubs identified. As a solution, we apply a genetic algorithm and test its properties both in small case studies and in a simulated problem instance of a larger (i.e. comparable with real-world instances) size. We show that the genetic operators we employ are capable of switching between solutions based on direct origin-to-destination routes and solutions based on transfer connections, depending on what is more beneficial in a given problem instance. Moreover, the algorithm correctly identifies cases in which volumes should be shipped directly, and those in which it is optimal to use transfer connections within a single problem instance, if an instance in question requires such a selection for optimality. The algorithm is thus suitable for determining hubs and satellite locations. All considerations presented in this paper are motivated by real-life problem instances experienced by the Polish Post, the largest postal service provider in Poland, in its daily plans of delivering postal packages, letters and pallets.

CAPACITY SHARING STRATEGY WITH SUSTAINABLE REVENUE-SHARING CONTRACTS

This paper develops a duopoly model to analyse capacity sharing strategy and the optimal revenue-sharing contract under a two-part tariff and examines the effects of capacity sharing, cost, and sharing charges in three scenarios. The paper uses the two-part tariff method and adds a more realistic assumption of incremental marginal costs to improve the research on capacity sharing strategies. The results show that capacity constraints affect the sustainable development of firms. A sustainable revenue-sharing contract can create a win-win situation for both firms and promote capacity sharing. Capacity sharing, cost, and the revenue-sharing rate have different impacts in different scenarios; the optimal revenue-sharing rate and fixed fee can be determined to maximise the profits of firms that share capacity. However, capacity sharing may not improve social welfare.

Forced Labor Exploitation: Illegal Trading in Protected Goods in the Southern African Countries

Human exploitation refers to the curtailment of fundamental human rights. The crime plays out notwithstanding the laws that criminalizes human abuses. This study explored the policing of human trafficking and forced labor in the Southern African countries of the Southern African Development Community (SADC) and assesses the capabilities and abilities of law enforcement agencies in the region to curb the scourge. In this study a qualitative perspective was adopted with use of literature study and interviews. The prevalence of organized criminal groupings exacerbates the problem of human trafficking and forced labor in the region. Law enforcement corruption is rife as the police are often accused of acts of receiving bribes. There are capacity constraints in the policing agencies across the region which impacts negatively on proactive enforcement of protected goods. The study reveals that respective law enforcement agencies work in seclusion and do not systematize their databases to share information with other agencies owing to a prevailing cynicism amongst countries. It is proposed that there should be harmonization of law enforcement agencies’ databases to share information for intelligence purposes and to develop defensive and responsive response mechanisms to thwart the crime.

Kuwait faces imminent oil capacity constraints

Significance Capacity has fallen by around 15% over the past four years and is below the country’s official OPEC baseline. COVID-19 and difficult executive-legislative relations in 2020-21 have interfered with oil sector project delivery. Impacts As projects flounder, Kuwait will lose market share to regional rivals. Restructuring the Kuwait Petroleum Corporation from eight operating companies to three may boost administrative efficiency. Upstream operations are unlikely to be much affected by restructuring, given the dominance of Kuwait Oil Company.