Measurement of the torque-speed characteristics of induction motorsusing an improved new digital approach

A measurement technique for determining the torque-speed characteristics of induction motors is presented. This technique is in compliance with the IEEE standard test procedure for polyphase induction motors and generators. It is based on the acceleration method which is performed under no-load conditions. A fast data-acquisition system is used to record the speed and other signals of interest. The data is processed digitally with the objective of removing undesired extraneous signals while preserving the accuracy of the machine characteristics over the complete range of speed. To achieve this objective, algorithms for performing adaptive window-size average filtering and numerical differentiation are developed. Experimental tests performed on 1 HP and 600 HP induction motors confirm that this approach has several advantages over other methods. It produces very accurate results over the full dynamic speed range of the machine and permits precise correlation between the switching transients on the line with the variation of the speed signal     

Site‐specific and Spatially Controlled Addressability of a New Viral Nanobuilding Block: Sulfolobus islandicus Rod‐shaped Virus 2

Nanotechnology seeks to mimic what nature has achieved: self‐assembly at the nanometer scale. Viral nanoparticles (VNPs) provide natural examples of self‐assembled architectures with unique structural and chemical properties. Here, the utilization of an archaeal virus, Sulfolobus islandicus rod‐shaped virus 2 (SIRV2), as a template for site‐selective and spatially controlled bioconjugation is described. SIRV2 is a virus of a hyperthermophilic and acidophilic host, the archaeon S. islandicus growing optimally at 80 °C and pH 3, and is thus, by its nature, an extremely stable VNP. The stability of SIRV2 in different solvent/water mixtures is monitored, and it is found that in other, non‐natural harsh conditions the VNPs also remained intact. Further, the question of whether the particles offer attachment sites allowing for selective chemical modification and decoration with functional ligands using biotin as a probe is addressed. It is found that carboxylate‐, carbohydrate‐ and amine‐selective chemistries are applicable and various biotinylated SIRV2 formulations can be fabricated. Depending on the chemistry and hence attachment site used, the display of the biotin labels can be spatially controlled at the virus body and at the ends. Labeling studies also provide novel insights into the structural properties of SIRV2, indicating that the major coat protein (CP) forms the virus body while the minor CP is located in the tail fibers at the end of the particles. Overall, SIRV2 represents an extremely stable and structurally interesting VNP with the potential for novel nanobiotechnological applications.     

The plutonium/hydrogen reaction: The pressure dependence of reaction initiation time

The hydrogen pressure dependence of the initiation time (I_t) of the plutonium hydriding reaction has been determined over a hydrogen pressure range of 10-1000 mbar for plutonium covered in a dioxide over-layer. The data show that hydriding initiation time is inversely proportional to hydrogen pressure. This observation is consistent with a model of hydriding attack in which the dioxide over-layer acts as a diffusion barrier, controlling the flow of hydrogen to the oxide/metal interface. The low scatter and reproducibility of the experimental data set illustrate the importance of synthesising a reproducible oxide layer prior to determining this experimental parameter.     

Models for Balanced Voltage Operation of Linear Induction Motors

The mathematical analysis for many studies on linear induction motors is based upon an extension of the iron in the direction of motion. The models from two such analyses are compared. For a single layer induction motor fed by a three phase balanced voltage, one of the models is shown to yield better results than the other.     

Oropharyngeal morbidity following transoral approaches to the upper cervical spine

OBJECTIVE: A clinical definition of a hypertensive emergency is excessively high blood pressure in the presence of symptoms indicating end organ damage. Equally high blood pressure without symptoms is called a hypertensive crisis. Patients with hypertensive crisis or emergency need prompt, effective, and specific therapy and a controlled reduction of blood pressure. METHODS: We performed a randomized, double-blind multi-centre study, to compare the safety, efficacy and tolerability of an intravenous (i.v.) infusion of two dihydropyridine calcium channel blockers (either nifedipine or felodipine) in 122 patients, of whom 63 were diagnosed as hypertensive emergencies and 59 as hypertensive crisis, who had not reacted adequately (diastolic blood pressure <115 mmHg) to 5 mg of nifedipine PO. RESULTS: Both drugs lowered blood pressure adequately in more than 90% of the patients and were well tolerated. Only one patient had to be withdrawn, because of an excessive decrease in blood pressure. CONCLUSION: Patients with excessively high blood pressure who do not react to oral nifedipine can be treated equally effectively with felodipine and nifedipine IV. Felodipine is easier to handle because of its lack of light sensitivity.     

双向IGBT开关在矩阵变换器中的应用

双向IGBT模块是实现高频矩阵变换器极为有效的方法。略不同于硬开关PWM变换器，矩阵变换器中的开关和传导损耗取决于所选的调制策略。本文介绍了一种由诺丁汉大学推导的平均损耗的计算公式。测试一个使用1200V，200A的双向模块实现的三相到单相的构造，得到的波形说明了矩阵变换器的实际操作以及可能会出现的输出电流纹波。     

Conformation and ion-channeling activity of a 27-residue peptide modeled on the single-transmembrane segment of the IsK (minK) protein

IsK (minK) protein, in concert with another channel protein KVLQT1, mediates a distinct, slowly activating, voltage-gated potassium current across certain mammalian cell membranes. Site-directed mutational studies have led to the proposal that the single transmembrane segment of IsK participates in the pore of the potassium channel [Takumi, T. (1993) News Physiol. Sci. 8, 175-178]. We present functional and structural studies of a short peptide (K27) with primary structure NH2-1KLEALYILMVLGFFGFFTLGIMLSYI27R-COOH, corresponding to the transmembrane segment of IsK (residues 42-68). When K27 was incorporated, at low concentrations, into phosphatidylethanolamine, black-lipid membranes, single-channel activity was observed, with no strong ion selectivity. IR measurements reveal the peptide has a predominantly helical conformation in the membrane. The atomic resolution structure of the helix has been established by high-resolution 1H NMR spectroscopy studies. These studies were carried out in a solvent comprising 86% v/v 1,1,1,3,3,3-hexafluoro-isopropanol-14% v/v water, in which the IR spectrum of the peptide was found to be very similar to that observed in the bilayer. The NMR studies have established that residues 1-3 are disordered, while residues 4-27 have an alpha-helical conformation, the helix being looser near the termini and more stable in the central region of the molecule. The length (2. 6 nm) of the hydrophobic segment of the helix, residues 7-23, matches the span of the hydrocarbon chains (2.3 +/- 0.25 nm) of fully hydrated bilayers of phosphatidylcholine lipid mixture from egg yolk. The side chains on the helix surface are predominantly hydrophobic, consistent with a transmembrane location of the helix. The ion-channeling activity is believed to stem from long-lived aggregates of these helices. The aggregation is mediated by the pi-pi stacking of phenylalanine aromatic rings of adjacent helices and favorable interactions of the opposing aliphatic-like side chains, such as leucine and methionine, with the lipid chains of the bilayer. This mechanism is in keeping with site-directed mutational studies which suggest that the transmembrane segment of IsK is an integral part of the pore of the potassium channel and has a similar disposition to that in the peptide model system.     

Modification of a chemiluminescent ozone monitor for the measurement of gaseous unsaturated hydrocarbons

A chemiluminescent ozone monitor using the ozone-ethylene reaction has been adapted for measuring unsaturated hydrocarbons. The only change in the monitor was a replacement of the ethylene supply system with an electric discharge ozone source. Chemiluminescence was detected for all olefin-ozone reactions studied, including ethylene, substituted ethylenes (vinyl fluoride, chloride and cyanide), propylene, the butenes, 1,3-butadiene and several higher olefins. The intensity of chemiluminescence differed for the different olefins and appeared related to the ozone-olefin reaction rate. Saturated hydrocarbons and aromatics did not give a response. The minimum detectability for ethylene was 0.003 ppm and this value was somewhat lower for the higher olefins.Several important implications of the findings are discussed. These include the development of a more sensitive ozone monitor and the application of a total olefin monitor for the measurement of reactive hydrocarbons.     

Monitoring calibration of descriptive sensory panels using distance from target measurements

Training targets can be established from product profiles that provide an objective representation of the underlying sensory characteristics of a group of products. If available to a panel leader, these training targets can be used to calibrate a panel and measure the accuracy of their responses. Response accuracy can be determined either by frequency counts—how often the target was hit versus how many opportunities there were to hit it—or by distance from target measurements—which attempt to further quantify the degree to which the target was hit or missed. In addition to the frequency counts, four distance-from-target methods are presented and discussed—Distance from Target, Distance from Range, Adjusted Distance from Target, and Adjusted Distance from Range—each of which provides insights into the degree to which the panel is calibrated.