Facility Location Problems: Models, Techniques, and Applications in Waste Management

This paper presents a brief description of some existing models of facility location problems (FLPs) in solid waste management. The study provides salient information on commonly used distance functions in location models along with their corresponding mathematical formulation. Some of the optimization techniques that have been applied to location problems are also presented along with an appropriate pseudocode algorithm for their implementation. Concerning the models and solution techniques, the survey concludes by summarizing some recent studies on the applications of FLPs to waste collection and disposal. It is expected that this paper will contribute in no small measure to an integrated solid waste management system with specific emphasis on issues associated with waste collection, thereby boosting the drive for e�ective and e�cient waste collection systems. The content will also provide early career researchers with some necessary starting information required to formulate and solve problems relating to FLP

Determinants of Wheat Production in Nigeria (1981 – 2019): A Bounds Testing Approach

The study examined the analysis of trends and determinants of wheat production in Nigeria between 1981 and 2019. The data for this study are time series data at macro level spanning from 1981 to 2019. All the data were largely sourced from Food and Agriculture Organization (FAO) statistical data base, Penn world data of the university of Pennsylvania and Central Bank of Nigeria (CBN) statistical bulletin. The data include output of wheat in Nigeria, local and international price of wheat, real exchange rate, and external reserve. The data were analyzed using autoregressive distributed lags to access the relationship between wheat output and factors affecting wheat production in Nigeria. Results showed that external reserve, per capita income, market reforms and technological advancement significantly increased wheat production in Nigeria. Consistency of government policies and policy actions geared towards reducing wheat imports should especially pursued by the government

An Improved Location Model for the Collection of Sorted Solid Waste in Densely Populated Urban Centres

This paper presents a facility location model for improving the collection of solid waste materials. The model is especially suitable for densely populated regions with several housing units as well as encourages initial sorting of wastes. Each individual house in the collection area is designated a customer, with randomly selected customers comprising the set of candidate hubs. The fundamental feature of the model is to group the customers into clusters by assigning each customer (house) to the nearest hub. Each cluster is then assigned to exactly one waste collection site drawn from the set of potential collection locations. The objective is to minimize the total number of activated waste collection sites such that all the customers’ requests are satisfied without violating the capacity limit of each site. A simple Lagrangian relaxation heuristic is developed for the problem and solved with the CPLEX solver on the AMPL platform to find a feasible solution. Results from the numerical implementation of model show the model is efficient and competitive with existing solid waste collection facility location model

A Test of Non-linear Conjugate Gradient Methods Via Exact Line Search

The conjugate gradient method provides a very powerful tool for solving unconstrained optimization problems. In this paper the non-linear conjugate gradient methods are tested using some benchmark non-polynomial unconstrained optimization functions. The task was accomplished by finding the exact values of the descent also known as the minimizing argument or rather the minimizer in each method. Findings also show that the basic requirement for exact convergence was satisfied by all the methods

A Review of Local Factors Affecting Solid Waste Collection in Nigeria

The knowledge of local and regional factors that affect effective solid waste collection plays an important role in choosing appropriate technology. Waste collection has grown to become a major challenge demanding daily response from waste managers and it becomes inevitable to provide stakeholders with necessary information to aid key decision-making. This paper provides a comprehensive and detailed review of local-based factors that affect waste collection in Nigeria. Literature study and on-site observation were used for getting theoretical and useful information on the collection of waste in the study area. The study considered various standard collection technologies and their supporting factors in order to assess the effectiveness of existing methods. The current collection techniques existing in different parts of the country together with unique local factors for these various areas are reported. The findings in many cases reveal that the method of waste collection adopted and equipment used are faced with many challenges. This paper revealed that there is no investment presently made on the existing development plan to initiate a modern waste collection system. The study recommends a new approach that could be used by institutions and government agencies for efficient municipal solid waste collection to achieve sustainable and effective sanitation which will consequently facilitate the development of an aesthetically balanced and friendly environmen

An Empirical Analysis of Climate Change Effects on Selected Cereals Acreage in Nigeria: A Ricardian Approach

This study examined the relationship between the acreage of selected cereal crops and climate variables for the period 1995 – 2021 in Nigeria. The study was based on maize, rice, millet and guinea corn for all the states in Nigeria for the period of study. Data for acreage of selected cereal crops for all the time period were collected from the Nigeria Bureau of Statistics (N.B.S) while data on the two important climate variables required for crop growth – temperature and precipitation – used for the analysis were obtained from the Nigerian Metrological Agency. The results indicated positive response of the acreage of the cereal crops to increase in temperature which is possibly due to other factors that serve in cushioning the effect of the temperature such as irrigation; rainfall has mixed relationship with the acreage of the cereal crops except; the negative coefficient of trend variable shows a negative relationship with the acreage of selected cereal crops. The results of the elasticity of cereals acreage to climate variables show that the acreage of rice is inelastic to rainfall but elastic to temperature. However, maize, millet and guinea corn acreage are all appreciably elastic to precipitation and temperature changes. These results also reveal that with the passage of years and climate factors running contrary to agricultural productivities, cereal crops farmers in Nigeria were adopting new measures to cope with the negative effect of climate change. Climate adaptation measures which include the use of drought or heat resistant varieties, early sowing, mixed cropping, tillage system alteration and the utilization of land that has been considered too marginal for agricultural cultivation reduces the negative effects of climate change on cereal crops acreage and enhances the positive factors

APPLICATION OF LINEAR PROGRAMMING MODEL TO UNSECURED LOANS AND BAD DEBT RISK CONTROL IN BANKS

Most banks fail as a result of mismanagement of credit risk. In this paper, the management of credit risk as it affects loan portfolio management and proactive strategy to seek out relative value opportunities are considered. An operational research technique, linear programming, is applied to the management of loan portfolio of banks. With the results obtained, using Simplex method, an answer is provided to the question of how to avoid possible occurrence of non-performing loans, bad and doubtful debts in banks when some percentage of the loans they give out are not secured

A Stable and Consistent Finite Difference Scheme for a Time-Dependent Schrodinger Wave Equation in a Finitely Low Potential Well

In this paper, we present a stable and consistent criterion to an explicit finite difference scheme for a time-dependent Schrodinger wave equation. This paper is a departure from the well-established time independent Schrodinger Wave Equation (SWE). We do this for a particular case of a finitely low potential wel

LOCATION-ALLOCATION-ROUTING APPROACH TO SOLID WASTE COLLECTION AND DISPOSAL

Various studies have indicated that the collection phase of solid wastes, which comprises of the initial col- lection at the source of generation and the transportation to the disposal sites, is by far the most expensive. Two fundamental issues of concern in solid waste collection are the locations of initial collection and the period of collection by the dedicated vehicles. However, considering the prevailing conditions of adhoc lo- cation of waste containers and the faulty roads in many developing countries, this research was conducted to develop two e�ective models for solid waste collection and disposal such that new parameters measuring the capacity of waste ow from each source unit and road accessibility were introduced and incorporated in the mathematical formulations of the models. To formulate the problems, two classes of integer pro- gramming problems namely, Facility Location Problem (FLP) and the Vehicle Routing Problem (VRP), were used for the collection and disposal respectively. The clustering process involved in the model for the collection phase was based on the Euclidean distance relationship among the various entities within the study area. In this model, the study area was considered as a universal set and simply partitioned with each element representing a cluster. At this stage, a threshold distance was de�ned as the maximum allowable distance between a cluster and the potential collection sites. In the VRP formulation of the disposal model, two new parameters, called the accessibility ratio and road attribute, were introduced and included in the formulation. The inclusion of these parameters ensure that a waste collection vehicle uses only roads with high attributes. The solution to the model on the collection phase was based on the Lagrangian re- laxation of the set of constraints where decision variables are linked, while in the model on waste vehicle routing, the assignment constraints were relaxed. Both resulting Lagrangian dual problems were solved using sub-gradient optimization algorithm. It was shown that the resulting Lagrangian dual functions were non-di�erentiable concave functions and thus the application of the sub-gradient optimization method was justi�ed. By applying these techniques, strong lower bounds on the optimal values of the decision variables were obtained. All model implementations were based on randomly generated data that mimic real-life experience of the study area (Eti-Osa Local Government Area of Lagos State, Nigeria), as well as large-scale standard benchmark data instances in literature. These computational experiments were carried out using the CPLEX and MINOS optimization solvers on AIMMS and AMPL modeling environments. Results from the computational experiments revealed that the models are capable of addressing the challenge of solid waste collection and disposal. For instance, more than 60% reductions were obtained for the number of collection points to be activated and the container allocations for the different wastes considered. Numerical results from the disposal model showed that there is a general reduction in the total distance covered by a vehicle and a slight improvement in the number of customers visited. Result comparison with those found in literature suggested that our models are very efficient