Effect of drilling speed on the required torque and thrust force for non-ferrous materials

Constant-feed-rate drilling tests under conditions of dry cutting were performed on three non-ferrous materials, namely free machining brass, aluminium and lead. The tests covered a wide range of cutting speeds. Both thrust forces and torques were affected by the drill diameter and by speed variations. Empirical relationships between the thrust force, the torque and the cutting parameters were derived for the materials used.     

The fatty acid composition of Hibiscus sabdariffa seed oil

Analysis of Hibiscus sabdariffa seed oil from different seed collections (or cultivars), representing different growing areas, showed differences in the fatty acid pattern, especially with respect to linoleic (30.1-37.45%) and epoxyoleic (trace to 5.3%). The results showed different values from those previously reported for the cyclopropenoid fatty acid, found to be malvalic acid (0.4-2.0%), responsible for the positive Halphen response of the oil. It is now also established that the oil contains dihydrosterculic acid (1.0-1.6%) which has been reported previously in other species of the genus Hibiscus. The results of the rest of fatty acids showed ranges for myristic 0.2-0.5%, palmitic 17.4-22.6%, stearic 3.9-5.2% and oleic acid 34.6-39.8%.     

Utilization of oil-contaminated sands in asphalt concrete for secondary roads

The oil well sabotage during the Iraqi occupation and following the Iraqi withdrawal contaminated the Kuwaiti desert with crude oil covering millions of square meters. Thus, the desert has a huge amount of oil-contamined sand that must be cleaned up or treated in order to restore it to its natural beauty. The oil-contaminated sand was utilized to mix asphalt concrete in the laboratory to determine the feasibility of using sand contaminated with oil as feed stock in theproduction of asphalt construction materials. The products developed in experimental testing did meet international standards. The mixes were asphalt concrete of a quality that can be used for secondary roads, road beds, road subbases, impermeable layers for landfill and containment facilities, or as stabilizers for steep embankments. Gases emitted during the production of asphalt concrete utilizing oil-polluted sands are considered environmentally acceptable. Further studies are required to determine the feasibility of producing asphalt concrete from oil-contaminated sand on a pilot-plant scale as a means of utilizing the millions of square meters of oil-polluted sand.     

Effect of electron irradiation on alternating current electrical properties of gelatin – cadmium sulfide nano-composite films

Gelatin was doped with 1 %, 3 %, 5 % and 10 % cadmium sulfide nanoparticles in weight concentrations forming the gelatin-cadmium sulfide nanocomposites and irradiated by various electron beam doses equals 50 kGy, 75 kGy, 100 kGy, and 150 kGy using 3 MeV – 3 mA electron accelerator. The applied alternating current electrical field frequency ranging from 70 Hz to 5 MHz is what caused the fluctuation in dielectric properties and alternating current electrical conductivity of these nanocomposites. The results showed that the films of 1 %, 3 %, 5 %, and 10 % for blank (nanocomposite film without electron beam irradiation) nanocomposites had the highest dielectric parameters (έ, ϵ′′, tan δ) at 0.5 kHz with values of (0.696, 0.0233, 0.034), (0.533, 0.0114, 0.0215), (0.402, 0.001196, 0.003), and (0.459, 0.00418, 0.0091), respectively. However, the lowest dielectric parameters were (0.645, 0.00618, 0.0066), (0.523, 0.00165, 0.0215), (0.417, 0.00035, 0.0008), and (0.455, 0.00066, 0.0015) at 5 MHz, respectively. The highest conductivity values for blank nanocomposites of 1 %, 3 %, 5 %, and 10 % were 1.79×10⁻⁴ S/m, 1.45×10⁻⁴ S/m, 1.16×10⁻⁴ S/m, 1.27×10⁻⁴ S/m at 5 MHz, and the lowest values were 1.92×10⁻⁸ S/m, 1.49×10⁻⁸ S/m, 1.13×10⁻⁸ S/m, 1.26×10⁻⁸ S/m at 0.5 kHz, respectively. For irradiated nanocomposites at 5 MHz, the dielectric constant order for 1 % was 100 kGy, 150 kGy, 50 kGy, and 75 kGy with values 0.63, 0.537, 0.532, and 0.523, respectively. For 10 % weight concentration, the order was 50 kGy, 100 kGy, 150 kGy, and 75 kGy with values 0.515, 0.477, 0.47, and 0.437, respectively. Otherwise the dielectric constant order for 3 % and 5 % was 100 kGy, 75 kGy, 150 kGy, and 50 kGy. The highest dielectric properties and conductivity values for blank and irradiated nanocomposites were observed at 100 kGy for 1 %, 3 %, and 5 %.     

Annealing Dependence of Exchange Bias in MnO/Ga<Subscript>1−</Subscript><Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>As Heterostructures

We discuss the annealing-dependence of exchange bias in Ga_{1− x} Mn _x As epilayers that are overgrown with Mn. Although pure Mn is a known antiferromagnet, we find that the as-grown Mn overlayer does not produce any exchange coupling with Ga_{1− x} Mn _x As. Rather, our studies indicate that annealing in air is essential for creating the standard signatures of exchange bias (a clear shift in the magnetization hysteresis loop and an increased coercive field). We use X-ray photoelectron spectroscopy to characterize the compositional depth profile of both as-grown and rapid thermal annealed samples. These studies demonstrate that the cleanest exchange bias arises when the Mn overlayer is completely converted into MnO.     

Studies on (Hg0.7Mo0.3)Sr2(Sr1?xLax)Cu2Oz with a Wide Range of Doping State

The single-phased series of Sr-bearing Hg-1212 superconducting cuprate,(Hg_0.7Mo_0.3)Sr₂(Sr_1–x La _x )Cu₂O _z has been prepared. X-ray diffraction showed that, the obtained samples belong to the 1212-structure with tetragonal space group P4/mmm, similar to that of (Hg, Mo)Sr₂(Ca, Y)Cu₂O_z, and stabilized in a wide compositional range of 0.25x0.75. Refinements of the structure are carried out in which the oxygen atoms at the (Hg, Mo) layer is shifted from high-symmetry position (0.5, 0.5, 0) to (x, x, 0). Magnetization and electrical resistivity measurements show that the as-prepared samples exhibit evidence for superconductivity and their superconducting properties were improved after O₂ annealing with T ^onset _c as high as 92 K.     

The Valve Metal Character of Zirconium as inferred from anode potential measurements in mineral acid solutions

A study on the value metal character of Zr in 0.1 M solutions of H₂SO₄, HNO₃, and H₃PO₄ has been performed using the anode potential as the primary variable in galvanostatic, potentiostatic, and capacity measurements. A method of surface pre-treatment, which suppresses both O₂ evolution and metal dissolution, has been described. Kinetic parameters of oxide growth have been calculated. The results indicate that:

• (i) the high field approximation is applicable following an exponential law, and
• (ii) the height and activation distance of the energy barrier for ion transport through the oxide phase (Verwey model) are the same three acids.

Measurements have been also made on the dielectric breakdown of oxide, and this occurs at potentials above 200 V. Direct capacity measurements give similar results as those based on reciprocal capacity calculated from galvanostatic experiments. It is concluded that the dominant anodic oxide species is ZrO₂ having a dielectric constant of 25. Open circuit potential measurements show that Zr is spontaneously oxidized in the three acids.     

X-ray and electron microscopical studies of thin films of (Cd1−xZnx)S solid solution

A series of (Cd_1–x Zn _x )S powders phosphors and thin layers prepared by thermal evaporation of solid solution were studied. The phosphors used were 41% ZnS: 59% CdS with a cobalt concentration from 0 to 0.325%. The analysis of the structure of films of different thicknesses using X-ray diffraction technique confirms that the calculated relative intensities of the planes show considerable differences from the experimental results. For film thicknesses 70 nm thea axis is normal to the substrate, while at greater thicknesses (273 nm) thec axis is practically normal to the substrate. The effect of the electron beam on the solid solution indicates that layers decomposed leaving the grain boundaries decorated by metallic cadmium and zinc particles.     

Performance analysis of air cycle refrigerator integrated desiccant system for cooling and dehumidifying warehouse

In this paper, the performance of air cycle refrigerator integrated desiccant system used to cool and dehumidify warehouse is analyzed theoretically. Simulation analysis is carried out to calculate the system coefficient of performance, cooling effects and the humidity change under different values of pressure ratio, storage zone temperature inside dock and outdoor air conditions. Also, the effect of the air cycle and the rotor parameters on the system performance is evaluated. From the simulation result it is found that, the desiccant system has the ability to supply air to the dock area at very low humidity. The system coefficient of performance increases due to the exhaust heat recovery on the desiccant system, and this enhancement can be more than 100%. The coefficient of performance of the proposed system is greater than that of a conventional system under the same operating conditions.