Optimizing the allocation of technological resources of an air transport system in the presence of a schedule and fuzzy input data

The problem of optimal allocation of technological resources (operators) of a technical or organizational-technical system, designed to serve certain objects (operands) according to a given schedule, is considered. We take into account the necessity of incorporating, together with the main, preparatory and final operations, the possibility to select one or several operators for operand service into the service process, as well as the dependence of the operations duration on the factors characterized by uncertainty. Due to the supposed absence of statistics, expert-assigned indefinite values in the form of triangular fuzzy numbers are used. The optimization problem is formulated as a mathematical programming problem with a fuzzy criterion and clear-cut constraints, consisting in finding such a distribution of a given number of operators to serve each operand from a given set which minimizes the target function that takes into account deviations from the schedule (delay) with the service termination. Typical examples of systems for which the problem is relevant are the production complexes of air transport enterprises operating in conditions of uncertainty when it is necessary to ensure the regularity and safety of air transportation. A model example of solving the problem of allocating mobile refueling facilities at a hub airport, taking into account the peculiarities of its schedule, is presented. It is shown that the capabilities of standard personal computer software are sufficient for the solution.

Departure Time Choice Equilibrium and Tolling Strategies for a Bottleneck with Stochastic Capacity

This paper develops a bottleneck model in which the capacity of the bottleneck is assumed to be stochastic and follow a general distribution that has a positive upper bound. The user equilibrium principle in terms of mean trip cost is adopted to formulate commuters’ departure time choice in the stochastic bottleneck. We find that there exist five possible equilibrium departure patterns, which depend on both commuters’ unit costs of travel time, schedule delay early and late, and the uncertainty of the stochastic capacity of the bottleneck. All possible equilibrium departure patterns are analytically derived. Both the analytical and numerical results show that increasing the uncertainty of the capacity of the bottleneck leads to an increase of commuters’ individual mean trip cost. In addition, both a time-varying toll scheme and a single-step coarse toll scheme are designed within the proposed stochastic bottleneck model. We provide an analytical method to determine the detailed toll-charging schemes for both toll strategies. The numerical results show that the proposed toll schemes can indeed improve the efficiency of the stochastic bottleneck in terms of decreasing mean total social cost, and the time-varying toll scheme is more efficient than the single-step coarse toll scheme. However, as the uncertainty of the capacity of the bottleneck increases, the efficiency of the time-varying toll scheme decreases, whereas the efficiency of the single-step coarse toll scheme fluctuates slightly.

Analysis of Cost Overrun and Schedule Delays of Infrastructure Projects in Low Income Economies: Case Studies in Ethiopia

Today, several developing countries struggle to improve the cost and time performances of major infrastructure works due to various reasons. Cost overrun and delay are one of the major challenges being faced by the construction and infrastructure sector. Hence, the aim of this study is to explore the extent of cost overrun and schedule delays in building and road infrastructure projects across the Ethiopian construction industry. Primary data were collected through a structured questionnaire survey to evaluate the potential risks leading to those challenges. Various data analysis tools were employed, to investigate the critical causes of cost overrun and delays in infrastructure projects. The findings reveal that the minimum cost overrun for building construction projects is found to be 2%, whereas the maximum and average cost overruns are 248% and 35%, respectively. For road infrastructure projects, the minimum, maximum, and average cost overruns are found to be 1%, 61%, and 18%, respectively. Similarly, the minimum, maximum, and average delays recorded in building construction projects are 9%, 802%, and 143%, respectively, whereas, in road infrastructure projects, the minimum delay is found to be 3%, the maximum delay is 312%, and an average schedule delay of 110% is recorded. In addition, the top risk factors leading to cost overrun in infrastructure projects are inflation, inaccurate cost estimates, and variations, whereas the major risks causing schedule delays are variations, economic conditions, and escalation of material prices. Further, practical implications and key recommendations were provided to curb cost overrun and delay in infrastructure projects.

A Survey Study of Audiology Services during the Coronavirus Disease 2019 Pandemic in South Korea

Purpose: The coronavirus disease 2019 (COVID-19) pandemic has severely affected public health and people’s lifestyle. The purpose of this survey study is to investigate audiology services during COVID-19 pandemic to understand the current audiology service situations in Korea and to improve audiology services.Methods: A total of 120 participants (60 audiologists and 60 clients visiting audiologists) were surveyed in this study using online or face-to-face methods. The participants answered 24~25 questions including current status of audiology service, communication difficulties with wearing masks, and the provision of tele-audiology services during COVID-19.Results: The results showed that both audiologists and clients with hearing loss still preferred face-to-face audiology services in COVID-19 situation in spite of 56% of visiting schedule delay and cancellation. The primary audiology services they considered in COVID-19 were hearing aid fitting and maintenance & repair services. Wearing masks has led communication difficulties in both audiologists and clients with hearing loss due to speech level reduction, frequency filtering of sounds, and insufficient visual cues during the conversation. Only 30% of audiologists have provided tele-audiology services, and 4.4% of clients received tele-audiology services during COVID-19.Conclusion: The impacts of COVID-19 in audiology services in South Korea are still progressing. The technical and administrative systems and educational support to improve audiology services in South Korea are necessary.

Modeling Departure Time Choice of Car Commuters in Dhaka, Bangladesh

Dhaka, one of the fastest-growing megacities in the world, faces severe traffic congestion leading to a loss of 3.2 million business hours per day. While peak-spreading policies hold the promise to reduce the traffic congestion levels, the absence of comprehensive data sources makes it extremely challenging to develop econometric models of departure time choices for Dhaka. This motivates this paper, which develops advanced discrete choice models of departure time choice of car commuters using secondary data sources and quantifies how level-of-service attributes (e.g., travel time), socio-demographic characteristics (e.g., type of job, income, etc.), and situational constraints (e.g., schedule delay) affect their choices. The trip diary data of commuters making home-to-work and work-to-home trips by personal car/ride-hailing services (957 and 934 respectively) have been used in this regard. Given the discrepancy between the stated travel times and those extracted using the Google Directions API, a sub-model is developed first to derive more reliable estimates of travel time throughout the day. A mixed multinomial logit model and a simple multinomial logit model are developed for outbound and return trip, respectively, to capture the heterogeneity associated with different departure time choice of car commuters. Estimation results indicate that the choices are significantly affected by travel time, schedule delay, and socio-demographic factors. The influence of type of job on preferred departure time (PDT) has been estimated using two different distributions of PDT for office employees and self-employed people (Johnson’s SB distribution and truncated normal respectively). The proposed framework could be useful in other developing countries with similar data issues.

Construction Risks Management of Building Projects in Sultanate of Oman: Contractor and Owner Perspective

Managing risks is vital for any construction project to avoid cost overrun, schedule delay, and to meet the quality requirements. Over the last 10 years, the building market has evolved rapidly; businesses face greater risk and complexity than ever before. Risk assessment has been an integral aspect of the project management process. Because of the time and costs overruns involved with building projects, risk of building has become the focus of concern. This research focuses on exploring risk control techniques in construction industry. Risk reduction and management of planning is a critical approach that helps one to deal with the removal of different risks, their analyses, and the remedial steps that can be taken to remove them in a given project. Any construction company has to set up a risk management scheme to improve performance, reduce costs and increase sales. In this regard, set of principles have to be adopted for the development of ethical risk management planning decisions. In addition, hazards ought to be taken care of such that ensures a suitable norm of security for human wellbeing and the earth and at any rate offers the level of wellbeing that is sensible to people in the future today; there doesn't seem, by all accounts, to be any lawful avocation for limiting likely wellbeing and condition chances.

Risk Propagation of Concentralized Distribution Logistics Plan Change in Cruise Construction

Compared with the ordinary merchant ship building, the concentralized distribution in cruise building is more complex. Plan change is a common phenomenon in cruise building, and it is easy to lead to mismatch between production and logistics, resulting in risks such as production schedule delay and inventory backlog. In order to reduce the adverse effects of plan change on the shipyard, it is necessary to conduct an in-depth study on the risks of a centralized distribution logistics plan. Based on the analysis of the composition of the centralized distribution logistics planning system, risk factors in different plan links are identified in this paper. A system dynamic model is constructed to simulate the propagation of five basic types of planning risk, including procurement plan, warehousing plan, pallet concentralization plan, distribution plan and production plan. In the case study of HVAC (heating, ventilation and air conditioning) materials, the values of risk factors are estimated though consulting experts with questionnaire. The weight of each risk factor in each subsystem is calculated by a method combined with analytic hierarchy process and coefficient of variation method. Through the simulation experiments carried out in Vensim, it is found that both inventory backlog risk and cruise construction schedule delay risk increase with the increasement of estimated values of risk factors, which is an effective proof of the rationality of the model, and that the most sensitive risk factor for both the two kinds of risk is production planning risk.

Construction Schedule Risk Assessment and Management Strategy for Foreign General Contractors Working in the Ethiopian Construction Industry

Construction project schedule delay is a worldwide concern and especially severe in the Ethiopian construction industry. This study developed a Construction Schedule Risk Assessment Model (CSRAM) and a management strategy for foreign general contractors (FGCs). 94 construction projects with schedule delay were collected and a questionnaire survey of 75 domain experts was conducted to systematically select 22 risk factors. In CSRAM, the artificial neural network (ANN) inference model was developed to predict the project schedule delay. Integrating it with the Garson algorithm (GA), the relative weights of risk factors with rankings were calculated and identified. For comparison, the Relative Importance Index (RII) method was also applied to rank the risk factors. Management strategies were developed to improve the three highest-ranked factors identified using the GA (change order, corruption/bribery, and delay in payment), and the RII (poor resource management, corruption/bribery, and delay in material delivery). Moreover, the improvement results were used as inputs for the trained ANN to conduct a sensitivity analysis. The findings of this study indicate that improvements in the factors that considerably affect the construction schedule can significantly reduce construction schedule delays. This study acts as an important reference for FGCs who plan to enter or work in the Ethiopian construction industry.