Overland Water Flow and Solute Transport: Model Development and Field-Data Analysis

The application of plant nutrients with irrigation water is an efficient and cost-effective method for fertilizer application to enhance crop production and reduce or eliminate potential environmental problems related to conventional application methods. In this study, a combined overland water flow and solute transport model for analysis and management of surface fertigation/chemigation is presented. Water flow is predicted with the well-known Saint-Venant’s equations using a control volume of moving cells, while solute transport is modeled with the advection-dispersion equation. The 1D transport equation was solved using a Crank-Nicholson finite-difference scheme. Four, large-scale, field experiments were conducted on blocked-end and free draining furrows to calibrate and verify the proposed model. The results showed that application of solute during the entire irrigation event, or during the second half of the irrigation for blocked end conditions with appropriate inflow rates, produced higher solute uniformity than application of solute during the first half of the irrigation event. Measured fertilizer distribution uniformity of the low quarter ranged from 21 to 76% while fertilizer distribution uniformity of the low half values varied between 62 to 87%. The model was subsequently applied to the experimental data; results showed good agreement with all field data. Water balance errors for the different experiments varied from 0.004 to 1.8%, whereas fertilizer mass balance errors ranged from 1.2 to 3.6%. A sensitivity analysis was also performed to assess the effects of longitudinal dispersivity parameter on overland solute concentrations. A value of 10 cm for dispersivity provided a reasonable fit to the experimental data.     

Evaluation of Various Surface Irrigation Numerical Simulation Models

In this study, a zero-inertia model (ZIMOD) is presented to simulate all phases of border and furrow irrigation systems. The governing equations were discretized using a control volume of moving cells, by procedures reported in the literature for borders and for furrows. Later, the discretized equations were linearized by applying a Taylor series expansion according to the Newton-Raphson procedure, and then the algebraic linearized equations were iteratively solved using the Gaussian elimination technique. The ZIMOD was verified against several field experimental data and output of various numerical models in the SIRMOD package. Computational times, errors in predicting advance and recession trajectories, and estimated runoff and infiltrated volumes were compared. All models used in the comparative analysis predicted the advance and recession times and the infiltrated and runoff volumes satisfactory. However, models in the SIRMOD package were computationally faster than ZIMOD.     

Water—ethanol—gasoline blends as spark ignition engine fuels

The miscibility characteristics of hydrated ethanol with gasoline is investigated as a means of reducing the cost of ethanol/gasoline blends for use as a spark ignition engine fuel. For a given percentage of water in the ethanol, the experimental data shows that a limited volume of gasoline can be added to form a stable mixture. Engine experiments indicate that, at normal ambient temperatures, a water/ethanol/gasoline mixture containing up to 6 vol% of water in the ethanol constitutes a desirable motor fuel with power characteristics similar to those of the base gasoline. As a means of reducing the smog causing components of the exhaust gases, such as the oxides of nitrogen and the unburnt hydrocarbons, the water/ethanol/gasoline mixture is superior to the base gasoline.     

Use of the dendograph for data processing in fuel science

In fuel science there is a need to present the relationships between the elements of a group of variables or a group of samples as tables of data. The dendrograph, a derivative of the dendogram, is a method used for general cluster analysis. It offers an improvement by providing an irregular spacing of the objects classified on the x axis. The mathematical basis of this method is described as unweighted pair group method of clustering.     

Application of the extended Kantorovich method to the bending of variable thickness plates

The governing equations of the classical plate theory for a uniform or a unidirectional variable thickness rectangular plate under transverse applied loading are solved by means of the extended Kantorovich method. The plate may be either simply supported or clamped along the edges. The solution procedure is iterative and must be carried out numerically. This necessitates the calculation of the two missing pieces of boundary data along the edges of the plate. The missing boundary data are determined utilizing the method of adjoints of the shooting method. The numerical values of the deflection and bending moments for uniform and variable thickness plates are compared with those from the exact solutions and finite element analysis, respectively.     

A CFD Analysis of Ventilation Effectiveness in a Partitioned Room

A numerical model has been developed to investigate the contaminant removal and air freshness in a ventilated two-zone enclosure. The average contaminants and the distributions of air age in each zone under variable positions of door, supply and exhaust are compared. The correlation between the average contaminants and each of the main parameters, such as door location, supply and exhaust positions etc., are presented, and the average air ages in both zones are illustrated against door position. It is found that the average air age in the upstream zone is less affected by the door position than that in the downstream zone, and that the door position near the side-walls seems to give better air circulation. It is also concluded that the supply and door positions affect the concentration in the upstream zone significantly, while the exhaust location does not seem to influence the average concentration in either the upstream or the downstream zone.     

Modelling of volatile organic compounds emission from dry building materials

A numerical and an analytical model were developed to predict the volatile organic compound (VOC) emission rate from dry building materials. Both models consider the mass diffusion process within the material and the mass convection and diffusion processes in the boundary layer. All the parameters, the mass diffusion coefficient of the material, the material/air partition coefficient, and the mass transfer coefficient of the air can be either found in the literature or calculated using known principles.

The predictions of the models were validated at two levels: with experimental results from the specially designed test and with predictions made by a CFD model. The results indicated that there was generally good agreement between the model predictions, the experimental results, and the CFD results. The analytical and numerical models then were used to investigate the impact of air velocity on emission rates from dry building materials. Results showed that the impact of air velocity on the VOC emission rate increased as the VOC diffusion coefficient of the material increased. For the material with a diffusion coefficient >10⁻¹⁰ m²/s, the VOC emission rate increased as the velocity increased; air velocity had significant effect on the VOC emission. For the material with a VOC diffusion coefficient <10⁻¹⁰ m²/s, the VOC emission rate increased as the velocity increased only in the short-term; <24 h. In the medium to long-term time range, the VOC emission rate decreased slightly as the air velocity increased; velocity did not have much impact on these materials. Furthermore, the study also found that the VOC concentration distribution within the material; the VOC emission rate and the VOC concentration in the air were linearly proportional to the initial concentration. However, the normalized emitted mass was not a function of the initial concentration: it was a function of the properties of the VOC and the material.     

The Influence of Office Furniture,Workstation Layouts,Diffuser Types and Location on Indoor Air Quality and Thermal Comfort Conditions at Workstations

Abstract Many factors affect the airflow patterns, contaminant removal efficiency and the indoor air quality at individual workstations in office buildings. The effects of office furniture design and workstation layouts on ventilation performance, contaminant removal efficiency and thermal comfort conditions at workstations were studied. The range of furniture configurations and environmental parameters investigated included: 1) partition heights, 2) partition gap size, 3) diffuser types, 4) supply air diffuser location relative to the workstation, 5) return air grill location relative to the workstation, 6) heat source locations, 7) presence of furniture, 8) supply air temperatures, 9) adjacent workstations, 10) contaminant source locations, 11) supply air flow rates, and 12) outdoor air flow rates. The tracer gas technique was used to study experimentally the relative impact of these parameters on the air distribution and ventilation performance, as well as contaminant removal efficiency. Thermal environmental parameters such as air velocity and temperature were monitored at several locations to characterize the impact of these parameters on the thermal comfort conditions. The results showed that the outdoor air flow rate had a significant influence on the mean age of air. The air distributions at all the workstations were good even when the supply air flow rate was relatively low (i.e 5 L/s). At the same time, most of the parameters tested had a significant influence on contaminant removal efficiency when there was a contaminant source present somewhere in the office.     

Three-Dimensional Effects in Microcrack Nucleation in Brittle Polycrystals

Stress concentration at vertices where grains of a polycrystal meet at a point is contrasted with stress concentration at two-dimensional junctions where grains join along a line. Effects of thermal anisotropy and elastic anisotropy orientation mismatches from grain to grain are considered. Special geometries with moduli mismatches are also analyzed to shed light on three-dimensional vs two-dimensional behavior. Although there are exceptions, it is generally found that the stress concentration at vertices is more singular than that at junctions. Singularities which are stronger than cracklike singularities (i.e., stress α r ^{− s} where s > 1/2) are found, and the implication of such "super singularities" for microcrack nucleation is discussed. Conditions for propagation of microcrack flaws at vertices are analyzed and contrasted with those at junctions.     

A Simulated Annealing algorithm for a mixed model assembly U-line balancing type-I problem considering human efficiency and Just-In-Time approach

This research deals with balancing a mixed-model U-line in a Just-In-Time (JIT) production system. The research intends to reduce the number of stations via balancing the workload and maximizing the weighted efficiency, which both are considered as the objectives of this research paper.After balancing the line and determining the number of stations, the labor assignment policy should be set. In this study, it was assumed that there are two types of operators: permanent and temporary. Both types can work in regular and overtime periods. Based on their skill levels, workers are classified into four types. The sign at each work station indicates types of workers allowed to work at that station. An alert system using the hybrid kanban systems was also considered. To solve this problem, a Simulated Annealing algorithm was applied in the following three stages. First, the balancing problem was solved and the number of stations was determined. Second, workers were assigned to the workstations in which they are qualified to work. Following that, an alert system based on the kanban system was designed to balance the work in the process inventory. This was achieved by defining control points based on the processing time and making control decisions to minimize the number of kanban cards. In the proposed SA algorithm, two methods for the temperature cooling schedule were considered and two methods were defined for determining the number of neighborhood search. The initial temperature was considered equal to the cost of the initial solution to reach the convergence situation as soon as possible. Five problems were solved in small size using the GAMS software. The results obtained from the GAMS software were compared with those obtained from the SA algorithm to determine the performance difference. The computational results demonstrated that the SA algorithm is more consistent with the answers obtained. Also seven large scale problems were solved. The results showed that the SA algorithm still have better reliability. To show the efficiency of the proposed SA algorithm, an axel assembly company was studied. To satisfy demands and reduce backlogging, a mixed model assembly line was designed for this case study. The results showed that the mixed model assembly line designed using the SA algorithm had good efficiency.