Faculty of Science

Transportation of a product from multi-source to multi-destination with minimal total transportation cost plays an important role in logistics and supply chain management. Researchers have given considerable attention in minimizing this cost with fixed supply and demand quantities. However, these quantities may vary within a certain range in a period due to the variation of the global economy. So, the concerned parties might be more interested in finding the lower and the upper bounds of the minimal total costs with varying supplies and demands within their respective ranges for proper decision making. This type of transportation problem has received attention of only one researcher, who formulated the problem and solved it by LINGO. We demonstrate that this method fails to obtain the correct upper bound solution always. Then we extend this model to include the inventory costs during transportation and at destinations, as they are interrelated factors. The number of choices of supplies and demands within their respective ranges increases enormously as the number of suppliers and buyers increases. In such a situation, although the lower bound solution can be obtained methodologically, determination of the upper bound solution becomes an NP hard problem. Here we carry out theoretical analyses on developing the lower and the upper bound heuristic solution techniques to the extended model. A comparative study on solutions of small size numerical problems shows promising performance of the current upper bound technique. Another comparative study on results of numerical problems demonstrates the effect of inclusion of the inventory costs.

Transportation of a product from multi-source to multi-destination with minimal total transportation cost
plays an important role in logistics and supply chain management. Researchers have given considerable
attention in minimizing this cost with fixed supply and demand quantities. However, these quantities
may vary within a certain range in a period due to the variation of the global economy. So, the concerned
parties might be more interested in finding the lower and the upper bounds of the minimal total costs with
varying supplies and demands within their respective ranges for proper decision making. This type of transportation
problem has received attention of only one researcher, who formulated the problem and solved it
by LINGO. We demonstrate that this method fails to obtain the correct upper bound solution always. Then
we extend this model to include the inventory costs during transportation and at destinations, as they are
interrelated factors. The number of choices of supplies and demands within their respective ranges
increases enormously as the number of suppliers and buyers increases. In such a situation, although the
lower bound solution can be obtained methodologically, determination of the upper bound solution
becomes anNP hard problem. Herewecarry out theoretical analyses on developing the lower and the upper
bound heuristic solution techniques to the extended model. A comparative study on solutions of small size
numerical problems shows promising performance of the current upper bound technique. Another comparative
study on results of numerical problems demonstrates the effect of inclusion of the inventory costs.

Transportation of products from sources to destinations with minimal total cost plays an important role in logistics and supply chain management. All algorithms start with an initial feasible solution in obtaining the minimal total cost solution to this problem. Generally, better is the initial feasible solution lesser is the number of iterations of obtaining the minimal total cost solution. Here, first we demonstrate a deficiency of a recently developed method in obtaining the minimal total cost solution to this problem. Then we develop a better polynomial time (O(N 3) (N, higher of the numbers of source and destination nodes)) heuristic solution technique to obtain a better initial feasible solution to the transportation problem. Because of the intractability of carrying out enormous calculations in this heuristic technique without a soft computing program, this technique is coded using C++ programming language. Comparative studies of this heuristic with the best available ones in the literature on results of some numerical problems are carried out to show better performance of the current one. Our heuristic is found to lead to the minimal total cost solution in most cases (88.89%) of the studied numerical problems.

Determination of an Initial Feasible Solution (IFS) to a transportation problem plays an important role in obtaining a minimal total transportation cost solution. Better initial feasible solution can result less number of iterations in attaining the minimal total cost solution. Recently, an efficient method denoted by JHM (Juman and Hoque's Method) was proposed to obtain a better initial feasible solution to a transportation problem. In JHM only column penalties are considered. In this paper, a new approach is proposed with row penalties to find an IFS to a transportation problem. The new method is illustrated with a numerical example. A comparative study on a set of benchmark instances shows that the new method provides the same or better initial feasible solution to all the problems except one. Thus, our new method can be considered as an alternative technique of attaining an initial feasible solution to a transportation problem.

Linear Programming Problem is about minimizing the production cost of t-shirts of the production plant while satisfying its limitations. This paper presents a large scale Linear Programming Model to provide a fully functional Cost Effective System finding optimum number of machine operators and workers in each of its departments as well as finding optimum raw material for the entire t-shirts production. The model is tested by applying to an apparel production plant (Silk Line (pvt) Ltd). The solution of the model is found using the commercial software package called “ LINGO SOLVER ”. Moreover, a sensitivity analysis is performed to complete the target (entire t-shirts production) within a given specific period of time.

Seaweed is well known about for potential in chelating heavy metals. In this study, carbon paste electrodes were fabricated with siphonous seaweed Acetabularia acetabulum as the modifiers to sense lead (II) and copper (II) by square-wave anodic stripping voltammetry. Various scan rates and deposition potentials were measured to obtain the optimal peak current for Pb(II) and Cu(II). Optimum conditions of Acetabularia-CPE for sensing Pb(II) were at the scan rate of 75 mV/s and deposition potential of −800 mV, while for Cu(II) sensing were at 100 mV/s and −300 mV, respectively. The electrodes were characterized by the duration of accumulation time, preconcentration over a range of standards, supporting electrolyte, and standard solutions of various pH values. Interference studies were carried out. Both Zn(II) and Cu(II) were found to interfere with Pb(II) sensing, whereas only Zn(II) causes interference with Cu(II) sensing. The electrode was found to have good regeneration ability via electrochemical cleaning. Preliminary testing of complex samples such as NPK fertilisers, black soil, and sea salt samples was included.

We report results of combined experimental and theoretical studies of black tea waste extract (BTE) as a potential sensitizer for TiO 2 -dye-sensitized solar cells (DSSCs). UV-vis absorption data revealed that BTE contains theaflavin. DSSC sensitized with pigment complexes of BTE showed a photon-energy conversion efficiency of = 0.20%, while a significant increase ( = 0.46%) is observed when pH of the pigment solution was lowered. The HOMO and LUMO energy levels were calculated using experimental data of UV-vis absorption and cyclic voltammetry. These calculations revealed a reduction of the band gap by 0.17 eV and more negativity of HOMO level of acidified pigment, compared to that of original pigment. Combined effect of these developments caused the enhanced efficiency of DSSC. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) computational calculations were carried out to study the four theaflavin analogues which are responsible for the dark colour of BTE. According to the calculations, two theaflavin analogues, theaflavin and theaflavin digallate, are the most probable sensitizers in this dye-sensitized solar cell system.

Low-cost ion-selective electrodes for chloride analysis were fabricated using carbon rods extracted from spent AA batteries. The rods were cleaned and subsequently coated with polyaniline via multiple cyclic voltammetry of aniline monomer in hydrochloric acid solution. This method allows the multilayer formation of chloride-doped polyaniline film on the carbon surface that provides the physicochemical transduction for potentiometric sensing of chloride ions. Voltammetric parameters such as scan rate and number of scans as well as concentrations of monomer and dopant HCl were optimized based on the electrode response with laboratory prepared chloride solutions. Figures of merit were measured in terms of linear slope, linear concentration range and detection limit of the fabricated electrodes. One possible application of the electrodes being developed in this project is in the analysis of chloride in seawater. High levels of chloride ions can induce corrosion of steel bars and cause the deterioration of concrete structures in marine environment, hence the need for fast and accurate method of determining the concentration of chloride ions.

This study investigated the potential of Casuarina equisetifolia needle (CEN) on the removal of two important dyes, methylene blue (MB) and malachite green (MG), by batch adsorp-tion experiments. Characterisation of CEN's functional groups was done using Fourier Transform infrared spectroscopy while elemental analysis was carried out using CHNS analysis and X-ray flu-orescence. The experiments were carried out by varying the adsorbent dosage, pH, ionic strength, contact time and initial dye concentration. The pseudo-second-order kinetics model best represented the experimental data for both CEN-MB and CEN-MG systems. The Weber–Morris intra-particle diffusion model showed that intraparticle diffusion is not the rate-limited step for both adsorbates, while the Boyd model suggested both systems could be controlled by film diffusion. The Langmuir, Freundlich and Dubinin–Radushkevich isotherm models were used for describing the adsorption process. Of these, the Langmuir model best represented both adsorbents systems (CEN-MB and CEN-MG) giving maximum adsorption capacity (q m) of 110.8 and 77.6 mg g À1 , respectively, at 25 °C. Thermodynamics studies showed that both adsorption systems are spontaneous and endothermic.

Casuarina equisetifolia needle (CEN), a lignocellulosic-rich and sustainable material, was used in order to investigate its ability as an adsorbent to remove rho-damine B (RB) dye from aqueous solution. Fourier Transform Infrared spectrometer was used to characterise CEN functional groups and scanning electron microscope was used to study its surface morphology. Batch experiments were done in order to determine the effect of some parameters such as adsorbent dosage, initial pH, contact time, ionic strength, temperature and initial dye concentration. Kinetics, isotherm modelling and thermodynamics studies were also performed in order to explore an insight into the mechanism of the adsorption process. The study showed that the adsorption of RB by CEN is endothermic in nature and follows the pseudo-second-order kinetics model. The Langmuir isotherm model fitted the experimental data best with a maximum adsorption capacity of 82.34 mg g −1 .

Jackfruit seed (JS) was used in this study to investigate its potential as an adsorbent to remove rhodamine B (RB) dye from aqueous solution. Surface morphology and functional group analyses were carried out to characterise the adsorbent. Experimental parameters such as contact time, temperature, adsorbent dosage, dye concentration, medium pH and ionic strength were studied to explore their effects on the adsorption of RB dye onto the adsorbent. Thermodynamics, kinetics and isotherm models were applied on the experimental data in order to further understand the adsorption process and mechanism. The Langmuir and Sips models best described the adsorption process with predicted maximum adsorption capacity of 26.4 and 37.9 mg/g, respectively. The pseudo-second-order model best fitted the kinetics model and thermodynamics studies revealed adsorption process is endothermic.

The potential of Artocarpus heterophyllus (jackfruit) seed (JS) as an adsorbent to remove methyl violet 2B (MV) dye was investigated using batch experiment method. Surface morphology and functional groups of JS were analyzed in order to characterize the adsorbent. The adsorption experiments were carried out by varying the pH, dye concentration, contact time, ionic strength and temperature. Adsorption isotherm, kinetics and thermodynamics were also studied to further understand the adsorption process. Isotherm data was described using three isotherm models of which the Langmuir model best represent the experimental data with maximum adsorption capacity of 126.7 mg g-1. Pseudo 2 nd order described the adsorption mechanism and intraparticle diffusion was not the rate limiting step. Regeneration studies showed that JS was able to maintain good adsorption of MV dye even after a few cycles.

The removal of toxic dye rhodamine B (RB) from aqueous solution was achieved by using Casuarina equisetifolia cone (CEC) as an adsorbent. Batch experiment method was used in order to investigate the effects of contact time, pH, temperature, ionic strength, and dye concentration on the adsorption process. Kinetics and isotherm theoretical models were applied on the experimental data and it was found that the pseudo-2nd-order kinetics and the Langmuir isotherm model best fitted into the data. The Langmuir maximum adsorption capacity for CEC was determined as 49.5 mg g −1. The adsorption of RB onto CEC is thermodynamically favourable, feasible, and endothermic in nature.

Phytoremediation potential of Azolla pinnata (AP) was investigated for the remediation of malachite green (MG) dye from aqueous solution. This study involved the use of artificial neural network (ANN) as one of the mathematical tools for modelling the experimental data which showed good accuracy (R=0.867). The parameters of this study included the pH, initial dye concentration and plant weight. The optimum pH for phytoremediation of MG was in the range of 4-5, with reasonably high removal efficiencies of 81-84%. Reusability studies of spent AP showed good removal efficiency of 75% in the second cycle indicating its usefulness in repeated batch treatment. The growth estimation as indicated by relative frond number (RFN) showed that AP can tolerate a concentration of up to 15 mg/L MG.

This study investigates the potential of the stem axis of Artocarpus odoratissimus fruit (TSA) as an adsor-bent for the removal of methyl violet 2B (MV). The functional group analysis was carried out using Fourier-transform infrared spectroscopy. Investigation of the effects of pH and ionic strength provide insights on the involvement of electrostatic attraction and hydrophobic– hydrophobic attraction between the adsorbent and adsor-bates. Kinetics models (pseudo-first-order, pseudo-second-order, Weber–Morris and Boyd) and isotherm models (Langmuir, Freundlich and Dubinin–Raduskevich) were used for characterising the adsorption process. The Lang-muir model predicted a high qm of 263.7 mg g-1. Thermodynamics studies indicate the adsorption system is spontaneous, endothermic and physical sorption dominant. The spent adsorbent was successfully regenerated using water and obtained adsorption capacity close to the unused adsorbent even after fifth cycle of washing.

Casuarina equisetifolia cone exhibited potential to remove methyl violet 2B dye from the aqueous solution. The experiments were performed using batch method whereby parameters such as contact time, dosage, temperature, pH, ionic strength and dye concentration were investigated. The kinetics of the adsorption process was described using the pseudo-first-order, pseudo-second-order and Weber-Morris intraparticle diffusion models with pseudo-second-order better described the adsorption kinetics and more than one diffusion mechanism may be involved. The maximum adsorption capacity was determined as 63 mg/g, according to the Langmuir model.