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This paper investigates the influence of some critical parameters in lumped parameter thermal network (LPTN) models for electrical machines. Even though the conduction thermal resistances in LPTN models are well defined by analogy to electric circuit, some critical convection thermal resistances are still difficult to compute and usually determined by empirical rules based on the previous publications. Thus, these parameters, including the equivalent thermal resistance between the frame and the ambient, and the convection coefficients within the machine, e.g. between the frame and the inner air, the end-winding and the inner air, the rotor and the inner air, as well as the equivalent airgap thermal resistance, etc., are discussed and evaluated. Moreover, the winding models and the estimation of the equivalent thermal conductivity are also discussed. Based on a totally enclosed natural cooled interior permanent magnet synchronous machine, a thermal analysis software package Motor-CAD is employed in this paper to provide a reference for comparison.

In this paper, a combined lumped-parameter (LP) thermal model and 2-D simplified analytical winding models is developed to predict the critical temperatures in an electrical machine, especially the average and maximum temperatures of active-winding and end-winding. The 2-D analytical active-winding and end-winding models are obtained by solving the Poisson’s equation in polar coordinates and cylindrical coordinates with the Dirichlet boundary conditions, which are extracted from the LP thermal model. The analytical models are then simplified based on series expansions to reduce the computation time. Furthermore, the analytical models are used to calibrate the average active-winding and end-winding temperatures calculated by the LP thermal model and to estimate the maximum temperatures, which is suitable for real-time winding temperature estimation. The combined thermal model is applied to a medium size totally enclosed water cooled permanent magnet synchronous machine for electric vehicles, and validated by thermal analysis software Motor-CAD, 2-D and 3-D thermal finite-element analyses.

The effects of vacuum pressure and gas adsorption on field emission current of α-Fe2O3 nanoflakes were studied. It was found that field emission current of α-Fe2O3 nanoflakes decreased with increasing pressure. The field emission current decreased when N2 or O2 was introduced into chamber, while no obvious change was observed for H2 gas. An in-situ thermal treatment was carried out to eradicate the effect of absorbed gas. After the in-situ thermal treatment, the field emission current density was largely enhanced from 60 to 500 μA/cm2 under applied electrical field of 10 MV/m and the turn on field (Eturn-on) decreased from 7.6 to 5.2 MV/m. The lowered turn-on field was attributed to the decrease of surface work function induced by surface gas desorption and reduction of α-Fe2O3 nanoflakes. Moreover, the improvement of field emission performance can be retained in high vacuum condition, which indicates the in-situ thermal treatment is an efficient method to improve field emission properties of α-Fe2O3 nanoflakes.

The Ion Source Group at IMP has been undertaking a series of high intensity ion beam R&D projects. The first project is the development of the intense proton source and its low energy beam transport system (LEBT) for China Initiative Accelerator Driven Sub-Critical reactor (CiADS). The specific characteristics of the proton source are long-term reliability and flexible beam manipulation for the commissioning need of the Superconducting radio-frequency (SRF) accelerators. The LEBT is used to deliver 35 keV H+ beam to the entrance of a 2.1 MeV RFQ . And then the 2.1 MeV proton beam is further accelerated by the superconducting cavities to 25 MeV and eventually goes into a high power beam dumper. Another project is the development of the intense ion source for Jinping Underground Nuclear Astrophysics experiments (JUNA). The ion source was expected to provide 10 emA H+, 10 emA He+ or 2.5 emA He2+ beams for the study of (p, γ), (p, α), (α, p) and (α, γ) reactions in the first phase of the JUNA project. The main challenges of the ion source for JUNA project are production of intense He2+ beam, control of the beam contaminations and beam commissioning a wide beam energy range (70~800 keV) . In this paper, the studies of these intense beam injector systems, for instance, beam intensities, species and ratio, beam transmission efficiency in the LEBT and also the beam optics matching to the downstream accelerator systems will be presented.

Vertically aligned few-layer graphene is prepared using microwave plasma enhanced chemical vapor deposition. The vertically aligned few-layer graphene is irradiated by X-ray of different doses from synchrotron radiation. The main structure of vertically aligned few-layer graphene is found to remain unchanged after X-ray irradiation both in high and low vacuum. X-ray photoelectron spectroscopy results reveal that the oxygen content in pristine and irradiated few-layer graphene remain unchanged after X-ray irradiation in high vacuum. When irradiated in low vacuum, the oxygen content in few-layer graphene increases with X-ray dose. For the vertically aligned few-layer graphene irradiated in low vacuum, the work function first increases and then slightly decreases with further increase irradiation dose from 9.0 x 10(14) to 3.6 x 10(15) phs/cm(2). The field electron emission turn-on field is observed to increase from 4.0 to 9.1 MV/m after X-ray irradiation with the dose of 3.6 x 10(15) phs/cm(2). The mechanism of the changes in work function and field emission performance of vertically aligned few-layer graphene after X-ray irradiation in low vacuum are discussed. (C) 2013 Elsevier B.V. All rights reserved.

Soil surfactants are wetting agents designed to improve infiltration, water distribution, and water retention. This industry-independent study evaluates the effects on soil-water properties of four surfactants commonly used in the Pacific Northwest: Wet-Sol #233 (Schaeffer), WaterMaxx II (Aquatrols/Western Farm Services), Ad-Sort RST (Simplot), and ADVANTAGE Formula One (Wilbur-Ellis). These surfactants were tested at labeled rates on two sifted soils with no known water repellency issues: a Warden silt loam and a Quincy sand. No significant differences were found among the means of treatment variables of any of the surfactants or the control (irrigation water only) in the tests of infiltration rate and water holding capacity, at a significance level of α = 0.05. Significant differences were found for the tests of unsaturated hydraulic conductivity (p = 0.009) and capillary rise (p = 0.048) in the sand samples only. Lower unsaturated hydraulic conductivity was inferred from the results for Wet-Sol samples compared to the control and all other samples. Additionally, Formula One performed significantly better than Wet-Sol and Water Maxx in unsaturated hydraulic conductivity, but differences compared to the control were insignificant. In capillary rise tests, the rise height of samples treated with WaterMaxx, Ad-Sorb, and Formula One were significantly lower than that of the control samples. Hence, the use of surfactants did not benefit water penetration or soil-water distribution (up to 24 hours) according to the statistical tests on the four soil physical properties. Furthermore, the surfactants did not perform consistently across the different experiments. These findings indicate that a single application of these four anionic, nonionic, and block polymer surfactants does not improve the movement and conservation of soil-water in these hydrophilic soils.

Nisin is an antimicrobial polypeptide produced by Lactococcus lactis and is believed nontoxic to humans. The objective of this study was to evaluate a nisin-based formulation for the treatment of bovine clinical mastitis in lactating dairy cattle. A total of 92 cows with 107 clinically mastitic quarters were randomly assigned to nisin- (48 cows with 51 quarters) and gentamicin (GM)-treated (44 cows with 56 quarters) groups. In the nisin-treated group, cows received an intramammary infusion of nisin at a dose of 2,500,000 IU; in the GM-treated group, intramammary infusion of GM was administered at a dose of 0.8 g. Results indicated that nisin offered a clinical cure rate similar to GM (90.2 vs. 91.1%) and no difference in bacteriological cure rate than GM-treated group (60.8 vs. 44.6%, respectively). Proportion of the quarters with milk somatic cell counts500,000 cells/mL was not different in the nisin-treated group (50.0 and 47.8%) compared with the GM-treated group (33.3 and 37.3%) 1 and 2 wk after treatment. Of 17 Staphylococcus aureus isolates, 82.5% were resistant to penicillin, and 35.3% to GM, but none of them to nisin. Nisin therapy eliminated 54.5% (6 of 11) of S. aureus IMI, whereas GM eliminated 33.3% (2 of 6). Nisin in milk (4.5 +/- 0.8 IU/mL) was detected only at 12 h following intramammary infusion, which was much lower than the upper limit (500 mg/mL) allowed as preservative in milk by the China authority. Because of its efficacy in the treatment of bovine clinical mastitis, especially resistant Staph. aureus-caused IMI, as well as its safety in humans, nisin deserves further study to clarify its effects on mastitis caused by different mastitis pathogens on a larger scale.

Population-based study of semen quality is rare in literature. Healthy men aged 20-60 years from six Chinese provinces were invited to participate in the study between December 2000 and November 2002. Posters were distributed in the participating counties to enroll 200 subjects from each province. Medians percentiles and proportions below lower threshold of the WHO criteria for semen parameters were calculated. Generalized linear models were used to examine the determinants of semen quality. Semen samples from 1191 healthy Chinese men were collected and analysed. The medians (5th and 95th percentiles) were 2.3 ml (1.0-4.5) for semen volume 65 x 10/6/ml (20-150) for semen concentration 154 x 10/6/ejection (29-421) for sperm count 19% (5-32) for rapid progressive motility 46% (29-66) for progressive motility 67% (47-81) for total motile spermatozoa 70% (48-88) for sperm viability and 39% (23-76) for normal morphology. Many healthy Chinese men had semen parameter values below the lower threshold of the WHO criteria. Region age abstinence duration and season were important determinants of semen quality. Chinese men have lower values of semen parameters according to WHO standard and a lower threshold for normal semen parameters for Chinese men should be considered. (authors)

Dry-sliding and lubricated friction and wear behaviours of polyamide (PA) and ultra-high molecular weight polyethylene (UHMWPE) blend were studied using a pin-on-disc method (polymer pin sliding against a stainless steel disc) at room environment. The tribological performance of PA and UHMWPE were also investigated for the purpose of comparison. The worn surfaces were examined using a scanning electron microscope (SEM) and optical microscope. It was observed that PA specimen demonstrated highest friction coefficient, UHMWPE the lowest in both dry-sliding and lubricated sliding test. The friction of PA could be sufficiently decreased by blending with UHMWPE. Statistical analysis suggested the relationship between the wear volume loss and the sliding distance could be expressed by a linear model for dry-sliding, while a logarithmic model was determined for lubricated sliding. The difference in wear modes between both sliding series suggested that there was change in the mode of material removal process. The lower wear rate in lubricated sliding was attributed to the elastohydrodynamic or partial elastohydrodynamic lubrication through the development of a continuous lubricant film between the polymer and the counterface, while the high wear rate of the specimens, in dry-sliding test, was mainly caused by fatigue process due to the repeated action of tearing and crack-propagation.

High-performance MOCVD-grown N-p-N InP/GaAsSb/InP DHBTs based on epitaxial layers deposited on 100 mm InP substrates are reported. The transistors feature the first nearly ideal emitter/base junction characteristics reported for material grown using AsH 3 and PH 3 hydride precursors, a DC current gain β =30–40, and a peak cutoff frequency f T =245 GHz for a 0.5×12 μm 2 emitter fabricated on a 250 A lattice-matched carbon-doped base. We discuss layer composition and thickness uniformity, C-doping efficiency as determined by the comparison of SIMS and Hall effect data on bulk GaAs 0.5 Sb 0.5 layers, as well as provide SIMS and TEM data for the transistor layers (including a lattice image of the interface between GaAsSb and InP). To our knowledge, the present article provides the first detailed characterization of high-speed InP/GaAsSb/InP DHBTs fabricated on industrially grown epitaxial layers.

This paper reports, in a comparative method, the effect of dielectric barrier discharge (DBD) plasma and radio frequency (RF) plasma on the surface wettability, chemistry and microstructure changes of the surface of polytetrafluroethylene (PTFE). Both types of plasma could improve the PTFE surface wettability significantly owing to the changes in surface chemistry and surface microstructure. The high-energy species in high-vacuum (HV) plasma cause the PTFE surface severely etched and causing decomposition of outmost layer of PTFE, results in the evolution of tetrafluoroethylene via scission of the (CF2)n chain to yield oligomeric segments. In comparison, few heavy species in DBD plasma have high enough energy to cause the scission of the (CF2)n chain to yield oligomeric segments, thus less etching effect. The contact angle variation with energy dose on RF plasma-treated surface demonstrated a two-stage decrease behaviour: an initial fast decrease stage followed by a levelled-off stage. In comparison, three stages of behaviour are evident for DBD plasma-treated surface. A drastic decrease of the contact angle was recorded during early DBD plasma treatment (at low energy dose), followed by a steady stage and then a slow recovery stage.

Cured, uncured and stored (1 and 3 months) sweet potato roots were baked, frozen and stored at −23°C. Sensory scores, color (CIE L,a,b values), instrumental texture profile (Instron), sugars, beta-carotene, vitamin C, alcohol insoluble solids (AIS) and moisture contents were determined after 0,1, 3, 6 and 9 months frozen storage. Baked frozen sweet potatoes from all treatments were stable during 6 months frozen storage, with exception of vitamin C, which decreased by about 50% during the first month. Surface response analysis showed sensory scores for the prebaked sweet potatoes were very acceptable, particularly in the region with 1–2 months fresh storage of roots prior to freezing and followed by 1–6 months frozen storage.

Mg alloys have various advantages. However, the low formability due to the poor ductility of Mg alloys limits their engineering applications. In this study, an Mg-3% Gd alloys was chosen to explore processing approaches for improving its strength and ductility combination. The alloy was processed by accumulative roll-bonding (ARB) at 400 °C to 4 cycles followed by annealing at various temperatures. The microstructures after annealing were characterized by the electron backscatter diffraction technique and the mechanical properties were measured by a tensile test. It was found that the alloy has a good combination of strength and ductility after 2 cycle ARB processing followed by annealing at 290°C for 1h. The strength is 2.3 times higher than that of the fully annealed coarse grained alloy, and the elongation is comparable with that of fully annealed coarse grained counterpart. The good mechanical properties were related to the fine-sized heterogeneous microstructures and weakened texture.

A new slim hole LWD propagation resistivity tool has been developed that exceeds current commercial specifications for pressure, measurement accuracy, and depth of investigation. The MFR* (Multi-Frequency Resistivity Tool) is designed to operate in borehole pressures of up to 30,000 psi and flow rates of 400 gpm without sustaining damage to the tool or electronics. The MFR operates at both 2 MHz and 400 kHz at antenna-receiver spacings of 20, 30, and 46 inches. All antenna arrays are fully compensated and integrated into the drill collar1 to increase reliability and simplify maintenance. Digital Signal Processors (DSP's) are used to measure phase and attenuation at each transmitter-receiver pair, resulting in 48 absolute measurements. These 48 measurements are combined to produce 12 fully compensated resistivity measurements at unique radial distances from the borehole. The fully compensated antenna design and DSP electronics result in both phase and attenuation accuracy specifications of +/−.25 mmhos and +/−.5 mmhos respectively. The 400 kHz attenuation measurement made at the 46 inch antenna-receiver spacing has a diameter of investigation (DOI) of 197 inches at 20 ohm-m, which is deeper than what is currently available in the industry today. Making resistivity measurements accurately, deeper, and at varying radial distances from the borehole enhance existing applications such as geosteering and inversion modeling. Field test results acquired while drilling show the response characteristics of the tool in a horizontal well drilled with salt mud and a vertical well drilled with oil based mud (OBM).

Parallel processing has been applied for time domain simulations of power system transient behavior in order to implement real-time dynamic security assessment. In this paper, two different algorithms have been implemented and compared: the Shifted-Picard (SP) and the Very DisHonest Newton (VDHN). The former has been proved to be effective when parallelism-in-time is adopted whereas the latter is an effective solver when parallelism-in-space is exploited. Furthermore, two different parallel computing architectures have been considered: namely, the Sequent Symmetry computer with 26 processors which is a data shared memory machine and the nCUBE characterized by 128 CPUs which is a typical message passing parallel machine. A realistic network with 662 buses has been used to assess the performance of the different implementations. The comparison of the results allows the reader to understand both the limitations of the algorithmic approaches and the constraints imposed by the two parallel architectures. An optimal grain of the parallelism associated to the problem can be identified through the reported experience.

A technique has been developed to detect bed boundaries using a combination of computer modelling and real-time data from a 2 MHz dual resistivity MWD tool. This technique has proven effective in horizontal drilling projects in North America and Europe. Models of the response of a 2 MHz dual resistivity tool in high angle penetrations of various Australian reservoirs show the potential for application of this technique in Australian horizontal drilling projects.

An excellent description of the fusion excitation function in the system Ti + Zr is obtained in a model coupling collective surface excitations to the relative motion. For heavier systems that require an “extra push” for fusion, the coupled channel model reproduces the relative enhancements associated with different isotopes, but does not describe the absolute cross section well. In solving the coupled channel problem, we found that the adiabatic representation is very useful when many channels are allowed.

Isotopic differences in the fusion cross sections for 0+0, observed by Thomas, et al., are interpreted with a coupled-channel model. We find that most of the subbarrier enhancement of /sup 18/O+ /sup 16/O over /sup 16/O+ /sup 16/O is attributable to the excitation of the low 2/sup +/ state in /sup 18/O. However, the model predicts the enhancement to persist above the barrier, contrary to experimental findings.