Direct Resistivity Measurements Research Articles

Inclusion of inter‐bar currents in multi‐slice FE modelling of induction motors – influence of inter‐bar resistance and skew discretisation

PurposeTo study the inclusion of inter‐bar (IB) currents in a multi‐slice finite element (FE) model of induction motors and in particular the effect of the associated skew discretisation. To validate the model experimentally.Design/methodology/approachBoth a classical uniform distribution and a gauss distribution of the slices and the lumped IB resistances are considered. Measurements on a 3 kW induction motor allows one to estimate its IB resistance and to validate the FE model.FindingsA gauss distribution of the slices allows one to use fewer slices and thus reduces the computational cost. The simulation results show that, at full load, skew changes the different loss components significantly, while the IB currents have a minor effect.Research limitations/implicationsThe direct measurement of the IB resistance is by no means trivial. In the frame of this paper, it was indirectly determined, namely by means of a short‐circuit test.Originality/valueThe gauss distribution of the slices and the IB resistance; the systematic study of the skew discretisation; the experimental determination of the IB resistance.

パルス電流焼結法を用いた酸化亜鉛系セラミックスの焼結に対する試料内部電流の影響

The influence of the internal current for the ZnO ceramics on the sintering behavior by pulse current sintering (PCS) method was investigated. The electric resistance of the sintering ZnO ceramics drastically decreases by the addition of the small Al2O3, and it is expected that a part of sintering current flows in the specimen and affects the sintering behavior of the ZnO ceramics on the PCS method. To clear the dependence of inner current on the sintering behavior of ZnO ceramics, direct measurement of electric resistance of ZnO specimen under sintering by SPS device was carried out. It was observed that electric resistance of specimen decreases with increase in the temperature. The electric resistance begins to decrease from the low temperature of 200°C. The internal structure of sintered ZnO ceramics changed by the control of the internal current in the specimen using Al2O3 plate.

The Apolipoprotein B/AI Ratio and the Metabolic Syndrome Independently Predict Risk for Myocardial Infarction in Middle-Aged Men

Both the metabolic syndrome and an increased apolipoprotein B/AI (apoB/AI) ratio are powerful risk factors for cardiovascular events. We hypothesized that the apoB/AI ratio well-characterizes the dyslipidemia associated with insulin resistance and the metabolic syndrome and investigated those relations and if the apoB/AI ratio and the metabolic syndrome independently predicted subsequent myocardial infarction (MI). A community-based sample of 1826 men aged 50 was investigated at baseline and again at age 70. ApoB/AI ratio and the metabolic syndrome (National Cholesterol Education Program definition) were evaluated, and the incidence of fatal and nonfatal MI was followed for a median of 26.8 years from the age 50 baseline. ApoB/AI ratio was significantly higher in men with versus without the metabolic syndrome (P<0.0001), and increased with the number of components defining the syndrome (P<0.0001). ApoB/AI ratio was inversely related to euglycemic insulin clamp glucose disposal rate at age 70 (r=-0.34, P<0.0001). During follow-up from age 50, 462 subjects developed an MI. An apoB/AI ratio > or =0.9 (hazard ratio [HR], 1.48; 95% confidence interval [CI], 1.15 to 1.91) and presence of the metabolic syndrome (HR, 1.69; 95% CI, 1.30 to 2.21) at baseline were independent predictors for MI, adjusting for low-density lipoprotein cholesterol and smoking. The apoB/AI ratio was related to the metabolic syndrome, as well as to a direct measurement of insulin resistance. Despite this, the apoB/AI ratio and the metabolic syndrome were both independent long-term predictors of MI in a community-based sample of middle-aged men.

Physiologic assessment of allergic rhinitis in mice: Role of the high-affinity IgE receptor (FcɛRI)

There have been few reports using animal models to study the development of allergic rhinitis. Characterization of such a model in mice would be advantageous given the availability of reagents and gene-manipulated strains. We sought to develop a murine model of allergic rhinitis in the absence of lower airway changes. After sensitization and challenge, both wild-type and FcepsilonRI-deficient mice were studied for their ability to develop early- and late-phase nasal responses. In the invasive approach, direct measurements of nasal airway resistance (R(NA)) were obtained; in the noninvasive approach using whole-body plethysmography, respiratory frequency and expiratory and inspiratory times were monitored. In both approaches, nasal responses were determined either acutely after challenge (early phase) or 24 hours after challenge (late phase). After challenge of sensitized mice, R(NA) significantly increased. In parallel, respiratory frequency significantly decreased and was highly correlated with the increases in R(NA). Sensitized wild-type mice had an early-phase nasal response and persistent nasal blockage (late-phase response) after allergen challenge. In contrast, sensitized and challenged FcepsilonRI alpha-chain-deficient mice did not have an early-phase nasal reaction and exhibited reduced nasal blockage and lower IL-13 levels in nasal tissue homogenates. These data indicate that FcepsilonRI is essential to development of an early-phase nasal response and contributes to the development of the late-phase nasal response. These invasive and noninvasive approaches provide new opportunities to evaluate the mechanisms underlying the development of nasal responses to allergen and to assess various therapeutic interventions.

Direct measurement of vegetation resistance in prototype scale

The hydrodynamic force exerted by water stream on series of isolated willows of several size and foliage at full scale is experimentally analysed. The plants were both fully and partially submerged by the flow. The hydrodynamic resistance was measured by means of a properly designed force transducer. The plants drag coefficient is evaluated considering the willows equivalent to a series of rigid isolated cylinders; the estimated values of the drag coefficient are close to the theoretical values expected for the isolated cylinder and, due to the willows flexibility, decreases with the plant's Reynolds number. The measurements allow to evaluate the effect of plant stiffness on drag: a linear relation between force and the square of velocity is determined for the tallest, partially submerged, rigid willows; a linear increase of drag force with flow velocity is observed for the flexible plants in completely submerged conditions, due to streamlining (bending of trunk and shrinking of branches) and consequent decrease of the drag coefficient and of the momentum absorbing area. Finally it is clearly found out the great contribution given by the foliage to the global resistance of the plant; this contribution reaches the 40% of the overall drag in present experiments.

Effects of Mandrel, Borehole, and Invasion for Tilt-Coil Antennas

Summary Several recently published studies discuss the concept of inductive resistivity-logging devices with oblique transmitting and/or receiving coils. Both wireline induction and logging-while-drilling (LWD) propagation resistivity-tool concepts have been considered. Directional resistivity measurements and improved anisotropy measurements are among the benefits promised by this type of device. Analyses based on point-magnetic dipole antennas were used to illustrate these potential benefits. The effects of a metallic mandrel, borehole, and invasion were not considered because of the absence of a suitable forward model. This paper characterizes mandrel, borehole, and invasion effects for a variety of candidate tilt-coil devices with antenna array parameters similar to those of the previous studies. The characterization is based on calculations from a new forward model that includes tilted transmitting and receiving coils of finite diameter embedded in a concentric cylindrical structure. Important details of the forward model used in the calculations are also provided.

A comparison of the homeostasis model assessment (HOMA) with direct measurements of insulin resistance in pregnancy with and without gestational diabetes (GDM)

MEASUREMENTS OF INSULIN RESISTANCE IN PREGNANCY WITH AND WITHOUT GESTATIONAL DIABETES (GDM) MARTIN MONTORO, SIRI KJOS, ANNY XIANG, THOMAS A. BUCHANAN, University of Southern California, Women’s and Children’s Hospital, Dept. of OB/GYN, Los Angeles, California, HarborUCLA Med. Ctr., Dept. of OB/GYN (LA BioMed), Torrance, California, University of Southern California, Preventive Medicine, Los Angeles, California OBJECTIVE: To correlate third trimester HOMA [fasting serum glucose (mmol/L) ! fasting serum insulin (uU/mL)]/22.5 with insulin resistance and b-cell function in control and GDM women. STUDY DESIGN: 150 GDM and 25 non-diabetic women underwent (a) oral glucose tolerance test (OGTT), (b) intravenous glucose tolerance test (IVGTT) with minimal model analysis and (c) euglycemic clamps with measures of basal and steady state glucose turnover. Exclusion criteria included history of hypertension, previous insulin use and positive anti-pancreatic islet cell antibodies. Linear regression analysis was used to evaluate relationships between HOMA (dependent variable) and four direct measures of insulin sensitivity: (a) MINIMOD SI, (b) clamps steady state (SS) glucose requirements (GINF), (c) clamp ratio of SS/GINF: SS plasma insulin (GINF: ins), and (d) clamp SS glucose clearance rate. RESULTS: During pregnancy, the HOMA calculations were significantly but weakly correlated with MINIMOD SI (R = 0.34, R 2 = 0.12); clamp GINF (R = 0.454, R =0.21), clamp SS GINF: insulin (R = 0.377, R = 0.142) and clamp SS glucose clearance (R = 0.404, R = 0.163). Raw data demonstrate non-linear relationship between HOMA and direct measures of insulin sensitivity in pregnant women. CONCLUSION: The HOMA, an empirical calculation based on fasting insulin has a non-linear relationship to insulin sensitivity. During pregnancy the range of insulin sensitivity is truncated compared to non-pregnant individuals thus limiting the applicability of HOMA as a measure of insulin sensitivity in pregnancy.

P1180 RXC GRAPH METHOD: BIA VECTOR IN THE FIRST YEAR OF LIFE

Introduction: Bioelectrical impedance analysis (BIA) is a safe, non invasive, portable and inexpensive method which allows to evaluate nutritional state. Its evaluation is possible with BIA vector (BIVA), which is the resultant of two variables: R/H and Xc/H. They are obtained from direct measurements of resistance (R) and reactance (Xc) standardized by the infant’s length (calculated in metres). R and Xc are respectively hydration and cellular mass indicator. Aim: To evaluate R/H and Xc/H’s variations in the RXc Graph in the first year of life and to map out the BIA vector for each month. Methods: A longitudinal study was performed on 41 healty infants aged 0–12 months, seen in a pediatric out-patient department from May 2002 to September 2003. They have been evaluated for growth indexes such as weight, length, cranial circumference, BMI. Bioimpedance parameters (R and Xc) were estimated by a single frequency phase sensitive impedance analyser( Quantum BIA-101Q, Rjl System Akern; Firenze Italy), standardized by the infant’s lenght (R/H; Xc/H), once a month. The bioelectrical impedance vector analysis (BIVA, or BIA vector) has been plotted by bioimpedence values, for each month. Statistical analysis was performed using t-test. Results: We observed a progressive shortening and down-sloping of the impedance vector over successive measurements; all through the growing it leans to origin of the axis.Table 1: R/H - Xc/H in the first year of life (M ± DS)Conclusion: The trend rose from the 1° to the 12° month according to the data reported in literature for the following years until the puberal age. Furthermore the RXc graph could be an efficacious and immediate method for bioimpedance values interpretation in nutritional state evaluation.

Direct measurement of grain boundary resistance in granular-type magnetoresistance thin films

The effects of grain boundary on the low-field magnetoresistance (MR) were assessed by preparing a set of polycrystalline La2/3Sr1/3MnO3 granular thin films with varying grain sizes and measuring their MR. The difference in the measured MR values was explained with interpretation of grain boundary resistance directly characterized by the complex impedance analysis. The resistance of grains was nearly independent of the grain size. On the other hand, resistance of the grain boundary increased with decreasing grain size.

Implant isolation in an indium phosphide optoelectronic device: A scanning spreading resistance microscopy study

Scanning spreading resistance microscopy has been used to delineate the implant isolated regions of an InP optoelectronic device. This scanning probe microscopy-based technique provides direct insight into the effect of helium implant isolation on the electrical conductivity of the material. The nanometer-scale resolution of the technique allows us to directly image the implanted region of the device structure. The results of the scanning probe measurements are compared with theoretical simulations of the helium implant damage. The optimal implant isolation conditions were determined by direct measurements of the series resistance across implanted and reference device material. The scanning spreading resistance microscopy results were able to provide fundamental insight explaining the implant conditions required for optimal isolation.

Bioelectric impedance vector distribution in peritoneal dialysis patients with different hydration status

In continuous ambulatory peritoneal dialysis (CAPD), total body water (TBW) is estimated by functions of body weight, and by equations of bioelectric impedance analysis (BIA). These procedures may be biased with abnormal tissue hydration. We validated vector BIA (BIVA) patterns of hydration in CAPD patients, based on direct measurements of resistance (R) and reactance (Xc) (RXc graph) without knowledge of the body weight. Cross-sectional study in 200 adult CAPD patients from two groups: 149 patients (77 males and 72 females) without edema (BMI 24.3 kg/m2), and 51 (29 males and 22 females) with pitting edema (BMI 24.6 kg/m2). Single frequency (50 kHz), whole-body impedance vector was measured with both empty and filled peritoneal cavity. Vector distribution was compared with that from 726 healthy subjects, 1116 hemodialysis patients, and 50 nephrotic patients, all with a same BMI. The performance of BIVA was compared with indications of four anthropometry and four conventional BIA equations for TBW. TBW estimates from anthropometry (Watson, Hume and Weyers, Chertow, and Johansson formulas) were misleading, indicating the same hydration in edema. TBW estimates from BIA equations indicated a 10% excess TBW in edema. BIVA were very sensitive to fluid overload, as both R (by 10%) and Xc (by 40%) were reduced in patients with edema (regardless of peritoneal filling). The vector distribution of individual CAPD patients without edema was superposable to that of the healthy, gender-specific, reference population (50%, 75%, and 95% tolerance ellipses, RXc graph) and close to the hemodialysis, presession distribution. Vectors from patients with edema were displaced downward on the RXc graph, out of the 75% ellipse (88% sensitivity and 87% specificity), and close to vectors from nephrotic patients. CAPD prescription would keep or bring vectors of patients back into the 75% reference ellipse (border for progression from latent to apparent overhydration across the lower pole) regardless of body weight. Whether CAPD patients with vector within the target ellipse have better outcome needs longitudinal evaluation.

Parameter comparison for low-noise Mo/Au TES bolometers

We describe a comparative investigation of the parameters of MoAu-bilayer TES bolometers designed for infrared detectors. A set of devices with variations in geometry were fabricated at the NASA/GSFC detector development facility. These detectors have different bilayer aspect ratios (providing differing normal state resistances and current densities), and have varieties of normal metal regions to study the effects of geometry on noise. These normal metal regions are oriented either parallel to or transverse to the direction of current flow, or both. The lowest noise detectors are found to have normal metal regions oriented transversely. For about a dozen different devices, we have measured a large set of parameters by means of a suite of tests. These include complex impedance measurements to derive time constants; IV curves to determine resistance and power; thermal conductance measurements; noise measurements as a function of device resistance; and direct resistance vs. temperature measurements.

Shaft Resistance of Single Vertical and Batter Piles Driven in Sand

An experimental investigation of the shaft resistance of single vertical and batter piles pushed into sand was conducted. A prototype laboratory setup was designed for testing relatively large model piles, inclined at an angle that varied between zero and 30° with the vertical. Two model piles having diameters of 38 and 76 mm were tested at a ratio of the pile’s length to diameter up to 40, and subjected to axial compression loading. The pile models were instrumented to allow direct measurements of the shaft resistance. A theoretical model was developed to take into account the asymmetrical earth pressure distribution around the pile shaft, the level of mobilization of the angle of friction between the pile shaft and the sand, and the pile diameter. The results predicted by the theory developed agreed well with the experimental results of the present investigation as well as other experimental and field results available in the literature. Design charts are presented for use in practice. The results of th...

A Note on Alternatively Direct Measurement of the Transfer Resistance over Vegetation

The boundary layer transfer resistance is an important parameter in micrometeorology. The most common approach to determining it uses a wind function that is extremely sensitive to the specified roughness length and can suffer large uncertainties, especially for partially vegetated surfaces. In order to avoid using some sensitive parameters not easily determined, a simple apparatus was designed for direct measurement of the resistance. This note reports the preliminary results of a test using the apparatus in a sparse wheat field.

ARPES EVIDENCE FOR A QUASIPARTICLE LIQUID IN OVERDOPED Bi2Sr2CaCu2O8+δ

High resolution angle-resolved photoemission spectroscopy of highly overdoped Bi 2 Sr 2 CaCu 2 O 8+δ with Tc = 51 K indicates that the basic transport processes in this material are fundamentally different from both the lesser-doped cuprates and model metallic compounds. The overdoped sample has sharp ARPES peaks at the Fermi energy throughout the Brillouin zone even in the normal state, unlike the lesser-doped compounds. In particular, the spectra near the (π, 0) point show the presence of a sharp peak well above Tc. The ARPES line shapes, and thus the self-energy, at a given energy are almost independent of k. Further, the quasiparticle scattering rate at the Fermi energy seems to be closely tied to direct resistivity measurements. This leads us to the conclusion that overdoped Bi 2 Sr 2 CaCu 2 O 8+δ is best described as a quasiparticle liquid. However, the energy dependence of the scattering rates is quite similar to that found in the lesser-doped compounds and quite different from that seen in a typical metal.

Phase transitions of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass at pressures up to 27 GPa

The phase transitions of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass have been investigated under high pressures and at room temperature. Direct resistance measurements in a diamond anvil cell provide evidence of a reversible transition between amorphous and crystalline phases; crystallization events occurred at 24 and 26.2 GPa on uploading, and crystalline-to-amorphous phase transitions were observed at 16 and 10.6 GPa on downloading. The phase transitions were confirmed by transmission electron microscopy observations.

In situ hard coatings strain measurement using a commercial strain-gage device

In this work we present a novel technique which can be used to measure in situ the induced substrate strain caused by the depositing film. The technique, based on the application of a commercial strain-gage, was used during the deposition of ultra-hard silicon carbide (SiC) films by RF magnetron sputtering, onto thin (95 μm) martensitic stainless steel substrates. The direct measurement of the electrical resistance of the strain-gage provides the strain values used to find the stress present in the film/substrate interface. Using a value of 480 GPa for the Young modulus of the SiC film, preliminary measurements furnish a value of the residual stress σ varying from 0.7 to 3 GPa, depending on the deposition conditions. These results are in good agreement with other ex situ measurements performed on the same material. The strain sensibility of this technique is about 10 μm/m.

Stability evolution of clayey slopes and measurement modelling of mobilizing shearing resistance

Materials in black clays weakly silty of the chaotic complex of “Argille Scagliose” and in blue clays with silt and weakly sandy of the basin of the Upper Pliocene, in the Bologna area (Italy) were examined.Samples with a different saturation degree for considering significant elastic modulus and permeability coefficients characteristic of homogeneous real unities of slope were tested. With these data it was possible to perform direct shearing resistance measurements with parameters expressed in effective and residual terms, to anlyse the stability of slopes formed with different materials and in evolutionary configuration of erosion.The permeability of these materials measured direct in the country, is about 10−4 cm.s−1 for blue clay and 10−5 cm.s−1 for black clay. In the laboratory in connection with homogeneous samples, permeability reaches values of 10−8 cm.s−1 for both materials.The subsequent tests of shear resistance carried out with the construction of a special speed reducer utilized three different speeds of preconstituted shear, i.e.: 10−3 cm.s−1, 10−5 cm. s−1, 10−7 cm.s−1. These tests have put in evidence higher values of shear resistance for blue clays with respect to black clays which reach lower values for the shear speed of 10−7 cm.s−1. This shear speed was chosen because it allows an almost complete dissipation of pore pressure. The axial compression tests with lateral deformation in free air revealed different elastic moduli for saturated and nonsaturated samples and for the two different materials tested. In particular: the elastic modulus for blue clays is smaller than that for black clays whereas saturated samples have an elastic modulus greater than that for non saturated samples. These data, introduced in a finite element model that utilises triangular mesh with at least six nodes, were analysed with the automatic system of calculation of plasticity with axis symmetric produced from “Plaxis”.With erosional data collected monthly and annually, projected to 100 and 300 years, a slope erosional model was constructed that made it possible to verify that black clays are unstable with Fs passing from 0.98 to 0.95 over 100 years. It is also possible to see that blue clays move towards stability with Fs passing from l.32 to l.34 over 100 years and to l.39 over 300 years.

The pathology of asthma.

Asthmatics respond with reversible airway narrowing when stimulated in ways that have no effect on non-asthmatic persons. Studies conducted at the turn of this century established that the pathology present in the airways of asthmatics is based on the inflammatory process. Recent work suggests that this inflammatory response may be driven by a particular group of T cells (Th2 response) that cause an overproduction of IL-4, IL-5 and other cytokines that produce an excessive infiltration of eosinophils and overproduction of IgE. The structural changes produced by the inflammatory process result in an overall thickening of the airway wall with changes in the epithelium, an increase in the interstitial matrix particularly the collagen types that contribute to the light microscopic appearance of the basement membrane, the vasculature, smooth muscle and mucous glands. Contraction of airway smooth muscle results in narrowing of the lumen particularly in the bronchioles where smooth muscle surrounds the entire lumen. An increase in wall tissue thickness as a result of asthma amplifies this normal effect producing a greater reduction in the airway lumen. Computer modelling of airway function and direct measurement of airway resistance in patients suggest that the smaller airways are the site of the greatest increase in airway resistance in asthma. These new data have shifted the emphasis away from the concept that abnormal airway smooth muscle function causes asthma toward the hypothesis that inflammatory-based changes in the airway wall act in series with normal smooth shortening to produce disease. The increased understanding of the role of the inflammatory process provides a basis for treatment of asthma with anti-inflammatory agents.

Resolving the electronic and nuclear effects of MeV ions in polymers

The electronic and nuclear stopping effects produced by MeV ion bombardment in polyvinylidene chloride (PVDC) and polyethylene (PE) were separated by stacking thin films of the polymers. The resulting layered system consisting of each polymer was bombarded with 3.5 and 5.0 MeV alpha particles. A layered system was selected such that the first layers experienced most of the effects of the electronic energy deposited and the last layers received most of the effects of the nuclear stopping. The electrical conductance and the changes in the chemical structure were measured by direct resistivity measurements, Raman microprobe analysis and FTIR. Post-irradiation analyses of the films indicated differences in these properties in the various film layers which are attributed to the individual effects of the stopping powers in the polymer films.