Unsteady free flow to an observation well from a semi-confined leaky aquifer

This paper presents an analytical solution to the problem of unsteady free flow of water from a leaky confined aquifer, fed by an external supply source and draining into a ditch. Both the non-homogeneous governing equation and the boundary conditions are converted to Sturm-Liouville problems. The closed form solution so obtained is significant because it not only illustrates the process of groundwater recharge and depletion, but can constitute a bench-test for numerical models.     

Numerical solutions of the one-phase classical Stefan problem using an enthalpy green element formulation

The enthalpy method is exploited in tackling a heat transfer problem involving a change of state. The resulting governing equation is then solved with a hybrid finite element - boundary element technique known as the Green element method (GEM). Two methods of approximation are employed to handle the time derivative contained in the discrete element equation. The first involves a finite difference method, while the second utilizes a Galerkin finite element approach. The performance of both methods are assessed with a known closed form solution. The finite element based time discretization, despite its greater challenge, yields less reliable numerical results. In addition a numerical stability test of both methods based on a Fourier series analysis explain the dispersive characters of both techniques, and confirms that replication of correct results is largely attributed to their ability to handle the harmonics of small wavelengths which are usually dominant in the vicinity of a front.     

Evaluation of Air Oven Moisture Content Determination Procedures for Pearl Millet (Pennisetum glaucum L.)

This study evaluated moisture content determination procedures for pearl millet using seven different air oven methods. The moisture content of the pearl millet samples varied from 11–41% (wet basis). The procedures included 130°C for 1 h; 130°C for 2 h; 105°C for 5 h; 105°C for 48 h; 105°C for 72 h; 130°C for 16 h; and 130°C for 20 h. Analysis of variance revealed that at high moisture content levels above 27% (wet basis), and the mean values of the moisture content determined were not significantly different (p > 0.05). Error analysis carried out showed that the moisture content determination methods were adequate to completely remove the moisture in pearl millet with moisture less than 35% (wet basis). Regression models were developed to predict the base moisture determination method (105°C for 72 h) as a function of other procedures.     

Experimental testing of thick-walled graphite fiber composite rings

Test results are presented from pressurizing thick-walled, hoop-wound graphite fiber composite rings to very high internal radial pressures. Hydraulic pressures exceeding 275 MPa (40 000 psi) were obtained. The testing was performed on rings wound with two different resins: a cyanate ester and a bismaleimide (BMI) resin. To prevent axial delaminations at these high pressures, a thin bi-directional G11 cloth lining was used inside the rings. The rings were monitored with strain gages and acoustic probes as the pressure was applied. Flaw-free cyanate ester rings survived the testing, indicating that the nominal transverse (radial) compressive strength of hoop-wound rings is higher than 275 MPa (40 000 psi).     

Green element computation of the Sturm-Liouville equations

A mathematical derivation of a new numerical procedure called the Green element method (GEM) is presented and applied to the solution of Sturm-Liouville problems. The GEM is a numerical technique which expands the scope of application of the boundary element method (BEM) by implementing the singular boundary integral theory in an element-by-element fashion; and like the finite element method (FEM) gives rise to a banded coefficient matrix which is easy to handle numerically. For this application, the location of both the field and the source nodes within the same element makes it possible for integrations to be carried out accurately, thereby enhancing the accuracy of discrete equations. The method is therefore easy to apply and, because of its domain based implementation, it maintains the flexibility of the FEM. We apply the GEM to the solution of boundary value differential equations which represent the form of Sturm-Liouville problems, and its capability is demonstrated by comparing the results with those of the finite element methods available in the literature. Satisfactory results and a second-order accuracy were found to be exhibited.     

Hand anthropometry survey of rural farm workers in south-eastern Nigeria

The importance of hand anthropometry as it relates to design of hand tools particularly for farm workers have been established; however, anthropometric data for this group of agricultural workers have continued to remain scarce. A survey of hand anthropometry relevant in design of agricultural hand tools was carried out on 200 male and 100 female adult farm workers in south-eastern Nigeria. Comparison of the male and female data obtained showed that male dimensions were higher than that recorded for the females. The hand anthropometric data of the male and female farm workers were compared with that of other populations but no clear distinction was observed. It was however clear that the following hand dimensions, 2nd Joint to root digit 3 and width at tip digit 3 recorded for Nigerian farm workers were highest and lowest, respectively, compared to other populations.

Practitioner Summary:

Hand anthropometric data relevant in design of hand tools have continued to remain scarce particularly for farm workers. Hand anthropometry survey of farm workers carried out in south-eastern Nigeria revealed higher dimensions for males than females; however, no clear distinction was observed in comparison with other populations.     

An efficient green element formulation for the Graetz problem

We propose an efficient Green element method (GEM) technique for the solution of the generalized Graetz problem. The main point is to illustrate how GEM concepts can be adapted to handle heat or mass transport in tube flow; with axial conduction first ignored but later included. Several numerical examples are tested to demonstrate this numerical approach; for all cases, it is seen that GEM offers an elegant and in comparison with the problem difficulty, a reliable and straightforward approach.