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31.
Sol–gel precursors to HfB2 and ZrB2 are processed by high‐energy ultrasonication of Hf,Zr oxychloride hydrates, triethyl borate, and phenolic resin to form precipitate‐free sols that turn into stable gels with no catalyst addition. Both precursor concentration and structure (a sol or a gel) are found to influence the synthesis of the diboride phase at high temperature. Decreasing sol concentration increases powder surface area from 3.6 to 6.8 m2/g, whereas heat‐treating a gel leads to residual oxides and carbides. Particles are either fine spherical particles, unique elongated rods, and/or platelets, indicating particle growth with directional coarsening. Investigation of the conversion process to ZrB2 indicates that a multistep reaction is likely taking place with: (1) ZrC formation, (2) ZrC reacts with B2O3 or ZrC reacts with B2O3 and C to form ZrB2. At low temperatures, ZrC formation is limiting, while at higher temperatures the reaction of ZrC to ZrB2 becomes rate limiting. ZrC is found to be a direct reducing agent for B2O3 at low temperature (~1200°C) to form ZrB2 and ZrO2, whereas at high temperatures (~1500°C) it reacts with B2O3 and C to form pure ZrB2. 相似文献
32.
Marcel Kornelis Erica van Herpen Ivo van der Lans Lusiné Aramyan 《Food quality and preference》2010,21(5):512-520
Food companies, governments, and societal organizations use an increasing number of food-choice motives to persuade consumers to buy food products, and the question which combinations of motives matter for which type of consumer has become of central relevance. In this study, we use a concomitant mixture-modeling approach to uncover consumer segments in terms of food-choice motives, using a nationwide sample in the Netherlands. The results reveal seven segments with distinct profiles and demonstrate that age and membership of environmental organizations play an essential role in segment membership probabilities. Our findings support the idea that information about non-food-related consumer behavior improves the identification of segments. In an additional analysis, we demonstrate how organizational membership also provides an effective way to access consumer segments as compared to diverse media outlets. We discuss the implications of our findings for segmentation practice. 相似文献
33.
Extracting local mechanical properties of steel bars by means of instrumented flat indentation 总被引:1,自引:0,他引:1
The evaluation of local mechanical properties of metal parts can be used for the prediction of forming and cutting forces during the following working stages. In order to show the feasibility of using indentation tests for work-piece characterization, C40 steel disks were cut from an extruded bar and machined by facing operation under different conditions. Indentation tests were carried out with 1 mm and 2 mm diameter indenters made of tungsten carbide; yield strength and indentation pressure values were extracted along the diameter of each disk. For the first time, indentation results were used to extract local mechanical properties of steel bars as a function of their process conditions: it was observed that small pins gave information on the effect of the machining process whereas large pins were more suitable to evaluate work-piece bulk properties. 相似文献
34.
The experiences of the largest corporation in the world and those of a start-up company show how companies can profitably reduce greenhouse gas emissions in their supply chains. The operations management literature suggests additional opportunities to profitably reduce emissions in existing supply chains, and provides guidance for expanding the capacity of new “zero emission” supply chains. The potential for companies to profitably reduce emissions is substantial but (without effective climate policy) likely insufficient to avert dangerous climate change. 相似文献
35.
36.
F. Delfino R. Procopio A. Andreotti L. Verolino 《Electrical Engineering (Archiv fur Elektrotechnik)》2002,84(1):41-50
An inverse procedure is presented for identifying and reconstructing the waveform of the lightning return stroke current.
It is based only on the acquisition of the electromagnetic field radiated by the discharge channel in various locations on
the ground and at various frequencies, and requires no information about the channel base current. The fundamental idea is
shown to come from an electrostatic problem in which the linear charge density of a vertical thin wire is determined starting
from the measured field. Three versions of this procedure have been developed: in the first, the identification is carried
out by means of the measurement of the electric field at various distances from the lightning channel at a given frequency;
in the second, only two sensors for the electric field are necessary, but various sampling frequencies; in the third, only
one observation point is needed, for the measurement of both the electric and the magnetic field. A simulated validation of
all the approaches is provided as well as a detailed analysis of their numerical accuracy.
Received: 4 April 2001/Accepted: 30 April 2001 相似文献
37.
Rosen Alexander J.; Lockhart Joseph J.; Gants Erica S.; Westergaard Cindy K. 《Canadian Metallurgical Quarterly》1991,100(4):583
A grip-induced muscle tension maintenance task distinguished between schizophrenic patients, regardless of medication or hospitalization status, and both normals and controls with affective (unipolar and bipolar) disorders. Unaffected 1st-degree relatives of schizophrenic patients also showed a grip deficit. Coupling the grip task with a visual discrimination task that divided attention through instruction or reinforcement contingency increased grip error times for all groups. No group differences appeared on the discrimination task, regardless of difficulty level, and the tone used to provide corrective feedback was not implicated in the grip deficit. The results suggest that the grip task is tapping, in a systematic and reliable manner, a motor-control abnormality that may be useful as a behavioral marker of schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
Problems with contracting out government services: lessons from orderly services at SCGH 总被引:1,自引:0,他引:1
This paper identifies and discusses the problems associatedwith contracting out labor-intensive government services. Itexamines in detail the contracting out of the orderly serviceat Sir Charles Gairdner Hospital (SCGH) in Western Australiaand its subsequent return to in-house delivery. When the orderlyservice was contracted out, the result was poor in terms ofcost, quality and externalities. Subsequent return of the serviceto in-house provision reduced costs and improved quality. Theproblems that led to failure of contracting out and subsequentsuccess of in-house provision can be explained in terms of transactioncost economics. 相似文献
39.
Rapallino MV Cupello A Luccardini C Nieddu E Seitun A Robello M 《Receptors & channels》2003,9(2):77-81
Vestibular Deiters' neurons have been isolated from bovine brain by the Hydén's freehand dissection technique and challenged with monoclonal antibodies directed toward the alpha 1 and beta 2/3 subunits of the GABAA receptors. Subsequent challenge with fluorescent secondary antibodies and confocal microscopy allowed the study of the cellular distribution of such subunits. In Deiters' neurons the beta 2/3 subunit displayed a clear presence all along the cell body profile and the initial parts of the dendrites. The alpha 1 subunit was found highly present all over the cell interior except the nuclear profiles. The strong presence inside the cells possibly masked its presence on the plasma membrane. However, in part of the cells studied a distinct presence on the plasma membrane was evident. This subunit was visualized also all along the long dendrites of these neurons. The approach we describe here, involving freehand isolated mature neurons from adult animals, may allow a better characterization of the tridimensional distribution of different types of neuronal GABAA receptors in the respect of the approach with brain slices. 相似文献
40.
Brodbeck WG Colton E Anderson JM 《Journal of materials science. Materials in medicine》2003,14(8):671-675
A previously established human monocyte culture protocol was used to determine the effects of varying adsorbed proteins on monocyte/macrophage adhesion and survival on dimethyl-silane (DM) or RGD modified glass coverslips. Cells were allowed to adhere for 2 h in the absence of protein or in the presence of serum, fibrinogen (Fg), heat inactivated serum (HIS), serum supplemented with Fg or HIS with Fg. Cell adhesion and apoptosis rates were determined on days 0 (2 h), 3, 7 and 10 of culture. The presence of serum alone in the initial culture was sufficient to optimize monocyte/macrophage adhesion and survival rates. Adding Fg to serum did not increase adhesion nor decrease apoptotic rates. No protein or the addition of HIS during the initial incubation period significantly decreased monocyte/macrophage adhesion and survival on both surfaces, however, the addition of Fg to HIS restored adhesion and survival rates to those seen with in the presence of serum alone on RGD surfaces. These studies demonstrate that monocyte/macrophage adhesion and survival on biomaterial surfaces are optimized by adsorbed heat labile serum proteins while adsorbed Fg plays a surface property-dependent role. 相似文献