Search

The article compares two different electrical rectifications employed by a piezoelectric harvester array. The first type consists of parallel connection of harvesters followed by an AC–DC full-bridge rectifier for overall electrical rectification. The second type allows for respective electrical rectification of each individual harvester, and then connecting them all in parallel. The former exhibits stronger electromechanical coupling effect for enhancing output power. The latter is capable of avoiding charge cancelation for improving bandwidth. The analysis of the electromechanical response of these two types is provided with full derivations for the second case. The predictions of displacement and output power are compared with the experiment and the results show good agreement. Two recommendations are offered from the present studies. First, suppose the power dissipations due to voltage gaps across the rectifiers are insignificant compared with the amount of output power realized by each individual harvester. The piezoelectric harvester array with respective electrical rectification exhibits better performance than that with the overall rectification from the broadband point of view at the cost of reducing peak power. On the contrary, if the amount of power dissipations can not be neglected or the harvester exhibits the strongly coupled electromechanical response, it is recommended to employ the harvester array allowing the mixed parallel/series connections switched by DPDT (Double-Pole Double-Throw). The array of the mixed type with overall electrical rectification exhibits performance significantly outperforming the array with respective electrical rectification from the point of view of broadband and power enhancement.

We determined temporal bone anatomy in patients with unilateral attic cholesteatoma. We compared the affected and normal ears of ten patients with unilateral attic cholesteatoma using three-dimensionally reconstructed high-resolution computed tomography images of the temporal bone. We determined the eustachian tube angle, eustachian tube length, sizes of the tympanic orifice of the eustachian tube, the pars flaccida, and the mastoid cavity, and distances of the pars flaccida and the tympanic orifice of the eustachian tube from the epitympanic roof. No significant differences were found between the normal and affected ears with regard to the size of the eustachian tube orifice, eustachian tube length or distances of the pars flaccida and the tympanic orifice of the eustachian tube from the epitympanic roof. By contrast, the mastoid cavity and the eustachian tube angle were significantly larger in the normal ears than in the affected ears [mean, 6.99 cm3(S.D., 4.9 cm3) vs. 1.28 cm3(0.81 cm3) and 16.7° (4.12°) vs. 13.89° (5.30°), respectively]. The pars flaccida was significantly smaller in the normal ears [1.07 cm (0.31 cm)] than in the affected ears [2.19 cm (0.77 cm)]. The inherent anatomy of the eustachian tube may be particularly important in the formation of attic cholesteatomas.

Estimation of water inflow during tunnel construction is traditionally regarded as a difficult task and is associated with a high level of uncertainty due to unexpected ground conditions. With new ground investigation techniques, in particular the use of horizontal directional coring (HDC), detailed ground conditions along the proposed tunnel alignment can be obtained prior to actual construction. This information can be used to identify potential problematic zones in which high water inflow is expected due to local adverse geological conditions. More importantly, the measurements of water flow rates during HDC can be used to provide a first approximation of the actual amount of water ingress during construction. This paper presents a procedure to estimate the amount of water ingress during tunnel construction using measurements made during ground investigations. Using the data obtained from the Po Shan drainage tunnels, comparisons are made for water inflow estimations using various methods that follow the same procedure but involve different sets of input parameters. The comparisons demonstrate that the initial water inflow rates observed during HDC are significantly higher than those measured during tunnel construction. The long-term water inflow measured during HDC is found to better reflect the actual seepage conditions during tunnel excavation.

The Miller-indices determination of the arising surfaces at the Si(0?0?1)convex corner due to anisotropic etching is investigated. We propose a 2D zoning model in which the undercut planes arising at a masked convex corner are presumed to be in the same zone as the sidewalls forming the convex corner, which is characterized by the parallelism of the intersection lines of each pair of new surfaces and the sidewalls. Based on this model a method combining the experimental data, analytical geometry and stereographic projection is presented to systematically determine the Miller indices of the arising planes. The quantitative prediction of undercut planes is confirmed by the angle measurement using a surface profiler.

A new Kirkpatrick-Baez-type focusing mirror system for use in synchrotron radiation IR beamlines is designed and fabricated. This mirror system, which contains two fifth-order-polynomial-corrected cylindrical mirrors, can collect and focus the long arc shape IR source from the bending magnet into a nearly perfect point image. To fabricate these two uncommon mirrors, 17-4 PH type stainless steel substrates are chosen and mechanically bent from planar to the desired fifth-order-polynomial-corrected cylindrical shapes with central radii of 3.74 and 5.43 m. The root mean square (rms) roughness and the slope error of these two mirrors are measured to be 0.3 nm and less than 6.3 rad, respectively. The method for calculating the polynomial coefficients of both mirrors as well as the mirror fabrication process, mechanical design, and the method for adjusting the mirror shape using a long trace profiler are presented. © 2004 Society of Photo-Optical Instrumentation Engineers.

Analytical electron microscopy has been used to study a new phase found in a Ti50 Pd50 alloy. The new phase was formed as ellipsoidal particles along the grain boundaries of the martensitic matrix. The crystal structure was identified as trigonal, with lattice parameters of a=0.83 nm, and c=2.62 nm, and point group ¯3m. The phase contains 68–73 at% Ti (48–54 wt% Ti).

The effect of Cu additions on the martensitic transformation sequence and temperature in Ti50-x/2Ni50-x/2Cuxalloys with x: 1–10 at% are investigated by ER, DSC, X-ray and IF measurements. Experimental results show that the transformation sequence of Ti50-x/2Ni50-x/2Cux alloys with x: 1–4 at% proceeding as two-stage B2?R?B19' transformation on cooling and Ti50-x/2Ni50-x/2Cux alloys with x=5, 10 at% have no martensitic transformation. The addition of Cu in Ti50-x/2Ni50-x/2Cux alloys assists the formation of R-phase, a behaviour which is quite different from that in Ti50Ni50-xCux alloys. Both the Ms and TR temperatures decrease rapidly with increasing Cu addition in Ti50-x/2Ni50-x/2Cux alloys with x: 1–4 at%. It is proposed that the Cu+Ni effects on the Ms temperature in Ti50-x/2Ni50-x/2Cux alloys is similar as Cu +Ni effects in Ti50Ni50-xCux alloys and as Ni effects in as-quenched Ni-rich TiNi alloys.

Refined, unhydrogenated soybean oil and edible beef tallow were interesterified with sodium methoxide. This was done as an alternative to hydrogenation for the production of plastic fats for use as margarine oils. Using 0.5% sodium methoxide at 80 C, interesterifi-cation was complete in 30 min as determined by lipase hydrolysis. A blend of 60% soybean oil and 40% edible beef tallow was found to have physical characteristics (melting point, solid fat index) similar to those of commercial tub margarine oils. The level of poly-unsaturated fatty acids was slightly lower and the level of saturated fatty acids slightly higher than the commercial margarine oils. Iodine value andtransfatty acid determinations indicated no dis-cernible effect on the degree of unsaturation or the level of isomeric fatty acids by the interesterification process. The interesterified blend did contain 3.0%transfatty acids which were originally present in the tallow. Oxidative stability of the interesterified oils was estimated by peroxide value determinations over several days on samples stored at 60 C. Experimental blends treated with 0.1% citric acid had poorer stability than the partially hydrogenated margarine oils; however, 0.01% BHA significantly delayed oxidation of the experimental samples.

Recent research has shown that population balance models hold considerable promise as a basis for accurate ball mill scale-up from laboratory batch grinding tests. Researchers at the University of Utah have developed and tested a scale-up approach based on linear population balance models which when used with an "experimental linearization" procedure (referred to as a similar fineness testing) produces accurate predictions of mill dimensions and product size distributions for commerical mills.Since wet ball mill grinding kinetics are often highly nonlinear and the similar fineness procedure required to apply the linear model can be somewhat tedious experimentally, the development of a scale-up approach based on a nonlinear model which is experimentally simpler to use is desirable. In the current paper an approach involving an empirical nonlinear kinetic model and a distributed volume model for material transport is evolved. The approach Is tested by predicting mill performance for a variety of materials (limestone, quartz, iron ore concentrate) in pilot and commercial scale mills (up to 14ft. in diameter) based on data obtained in a 10 inch diameter batch ball mill.

The use of condoms is an aid to protection against human immunodeficiency virus (HIV) infection and other sexually transmitted diseases (STDs). In a one-and-a-half month period in mid-1993, 190 commercial female sex workers and 633 male clients of 8 Social Hygiene Clinics in Hong Kong were interviewed on their practice in condom usage. For both sex workers and clients, 18.5% and 22.8% never and 55.3% and 50.3% seldom used condoms during sexual contacts with paying partners and non-paying partners respectively. The majority (86%) of male clients claimed that they would use a condom if they knew it could reduce risk of contracting HIV and other STD. Condom promotion activities are necessary, particularly for those at higher risk of infection because of their sexual behaviour.