有机-羟基磷灰石复合骨替代材料

本文对有机－羟基磷灰石复合生物材料的发展、研究近况作综述,对今后的发展方向也作描述。     

Discounted Least-Squares Gearshift Detection Using Accelerometer Data

A gearshift detector based on accelerometer readings is derived, and its performance is investigated with the aid of experimental data. The employed methodology contains a low-order parametric model of the acceleration performed by the vehicle in combination with the minimization of a fading-memory least-squares criterion for parameter estimation and tracking. It is shown that the resulting filtering equations converge so that filtered accelerometer outputs (i.e., instantaneous acceleration and its rate of change) are obtained by linear time-invariant filtering of the raw accelerometer data, where the tradeoff between noise suppression and tracking ability is entirely determined by a single user-chosen variable. Two detection variables are formed, and they are combined to produce the detector output. Evaluation on experimental data illustrates the potential of the proposed method.      

Hysteresis in quartz resonators-a review

The literature on the frequency versus temperature characteristics of quartz crystal resonators is reviewed. Three papers that deal with frequency versus pressure hysteresis are included, as these may possibly have relevance to frequency versus temperature hysteresis. It is seen that the causes of hysteresis are not well understood. The evidence to date is inconclusive. The mechanisms that can cause hysteresis include: strain changes changes in the quartz, contamination redistribution, oscillator circuitry hysteresis, and apparent hysteresis due to thermal gradients. The results to date seem to indicate that lattice defects are somehow related to thermal hysteresis. Stress relief in the mounting structure can also produce significant hysteresis. As crystal processing techniques have improved. contamination has become less of a problem.     

Hysteresis losses in a superconducting plate

On the basis of theoretical analysis expressions have been derived suitable for calculating the hysteresis losses in the presence of variable and constant components of both external magnetic field and transport current in a superconducting layer. The calculation scheme can be applied to any arbitrary shape of the field variation cycle, provided the variable components of the field and current are proportional. It has been assumed that the critical current density is dependent only on the external field. For the more common forms of this relationship the results have been expressed in an analytical form. Application of the results is illustrated by calculating the losses in a superconducting solenoid under variable current in the winding and the external field.     

Hysteresis studies in Clarke solder-blob junctions

A study of hysteresis in Clarke solder-blob junctions has been carried out in the temperature range 4.2–1.2 K. The temperature dependence of the critical current, the variation of the constant-temperature critical current with sequential sweep cycles, and the effects of an external field are studied. All the experimental results are explained as due to a net trapping of magnetic flux in the junction loop whenever a hysteretic curve is traced. The origin of the flux can be traced to the inductance of the superconducting loop and the electrical or geometrical asymmetry.     

Pressure Transducer Hysteresis Modeling

The paper describes the results of attempts to model hysteresis effects of strain gauge pressure transducers. Experimental data are presented with an analysis of the observed behavior and a model suitable for the transducer tested.     

Thermal Hysteresis in Thin-Film Platinum Resistance Thermometers

Thin-film platinum resistance thermometers (PRTs) are generally manufactured using the deposition of a thin platinum film on an alumina substrate and a laser-trimming method. Because of the strong adhesion between the platinum thin film and the alumina substrate, the PRTs inevitably have strain over the operating temperature range. This causes anomalies and instabilities in the resistance versus temperature characteristics (R?CT). The most prominent and observable effect of thermally induced strain is the thermal hysteresis in the R?CT characteristics. Thermal hysteresis is one of the main uncertainty factors in the calibration of industrial platinum resistance thermometers in laboratories. The thermal hysteresis for 30 thin-film PRTs was measured in the range of 0 °C to 500 °C in 100 °C steps. The thermal hysteresis was measured repeatedly using the same process, and the hysteresis decreased drastically with the repeated measurements. The thermal hysteresis was distributed from 16 mK to 156 mK for all sensors, and the lowest hysteresis was 1 mK to 11 mK in the test temperature range.     

汽车三包责任争议技术专家咨询标准化思考

本文通过分析汽车三包的现状和三包责任争议问题,给出了家用汽车三包责任争议技术专家咨询标准的思路和主要内容,旨在规范相关工作的流程,保障咨询工作公正有序进行,促使"三包"政策发挥更大的作用.     

Hysteresis losses in fine filament internal-tin superconductors

Hysteresis losses were measured on a series of fine filament Nb₃Sn superconductors made by the internal-tin process. Hysteresis was measured as a function of filament diameter and interfilament separation using a vibrating sample magnetometer in transverse magnetic field. Losses were greater than expected from the critical state model that expresses loss as a function of filament diameter. Micrographs of the reacted wire cross-sections showed some interfilament bridging for all wires. This gave rise to effective filament diameters that were greater than actual diameters. The critical interfilament separation, above which the losses would be expected to follow the critical state model, was determined.     

Hysteresis modeling based on similarity

A principle of constructing hysteresis models with stable minor loops is proposed. It has been found that a modeled reversal curve of any order can be obtained by copying (transplanting) the segment of the first-order curve that has the same overall dimensions and is the nearest to the modeled curve in the M- (or B-) direction. It is discussed how models with different grades of accuracy can be implemented within the framework of the approach. For the case when experimental first-order curves are absent, a procedure for their generation is suggested. The modeling is in remarkably good agreement with experimental data     

Generalized Constructive Model of Hysteresis

We describe a generalized constructive model of rate independent scalar hysteresis. It consists of an algorithm that uses a set of experimental hysteresis minor loop vertical chords. The introduced model requires new, less constraining properties than the congruency and equal vertical chords properties required by the classical and the generalized Preisach models. Our model allows for fitting transition curves of order greater than two, despite its simple mathematical notation. Further, we describe interesting performance of the model in numerical evaluation and inversion     

汽车三包标准作用及主要技术内容浅析

本文基于《家用汽车产品修理、更换、退货责任规定》,对相应的配套标准《家用汽车质量担保中主要零部件目录及有效期》国家标准的作用、主要框架和核心技术指标进行分析,为该国家标准的制定提供借鉴。     

偏转磁芯中磁滞损耗的估测

通过空间磁场和感应电压的测量,对偏转磁芯中的磁通密度分布进行了计算,并根据磁滞损耗的经验公式对Philips17英寸CMT的磁滞损耗进行了估测。该方法适用于降低能量损耗的偏转系统磁芯结构的优化和磁性材料的选择等。     

Hysteresis in the phase-slip state of superconducting filaments

Recently some papers on measurements of the I-V characteristics (where V is the time-averaged voltage) of superconducting indium microbridges ¹ as well as tin and zinc whiskers ^2,3 driven by a dc current into the phase-slip state have appeared. Special emphasis was placed on a discussion of the hysteresis, which is well-known in such experiments (see, e.g., Refs.1–18 in Kramer and Rangel ⁴ ). The hysteresis was compared with the predictions of the generalized time-dependent Ginzburg-Landau (GTDGL) equations for dirty superconductors in local equilibrium. ^4,5 Unfortunately these predictions represent the only results in this context derived ultimately in a rigorous fashion from the standard microscopic theory of superconductivity. Comparison was also made with a model by Kadin, Smith, and Skocpol (KSS), ^6,7 which gives a much smaller hysteresis. The authors of Ref. 1 found good agreement with the KSS model. The authors of Refs. 2 and 3 found a hysteresis which is larger than that of the KSS model, but still considerably smaller than predicted by GTDGL theory. They proposed a generalization of KSS which can be fitted to the data.