共查询到20条相似文献,搜索用时 15 毫秒
1.
《IEEE transactions on magnetics》2009,45(8):3085-3091
2.
Robert B. Conrad 《IIE Transactions》1971,3(2):142-149
A proposed simulation measurement model is developed which does not rely on the assumption that elements are random variables; therefore, it is based on the assumption that different times exist for the elements, depending upon their sequence of occurrence. By recognizing the sequential arrangement of elements, the interdependence among the elements is recognized. The proposed model includes a learning factor which reduces initial times in relation to the learning which occurs with each subsequent cycle. The model also provides flexibility for expressing the time values themselves. The mean value can still be used, but a randomly selected distribution of values or the operator's own times can be relied on whenever the analyst so desires. 相似文献
3.
S. A. Gudoshnikov B. Y. Liubimov Y. S. Sitnov V. S. Skomarovsky N. A. Usov 《Journal of Superconductivity and Novel Magnetism》2013,26(4):857-860
The electrodynamic method is applied to determine the specific absorption rate (SAR) of an assembly of superparamagnetic nanoparticles as a function of frequency and magnetic field amplitude. The home made frequency-adjustable electromagnet is used to create a nearly uniform magnetic field in a core gap of a volume 1×3×3 cm3 in the frequency range f=10–150 kHz and for magnetic field amplitudes up to H 0=250 Oe. Two oppositely connected pick-up coils are used to record the electromotive force signal (EMF) generated by magnetic nanoparticles. By integrating the EMF signal one can determine the low-frequency hysteresis loops of the assembly and the assembly SAR. Using this method the measurement of SAR has been carried out for magnetite nanoparticles with an average diameter D=25 nm. The electrodynamic method is shown to be capable of measuring a small amount of magnetic nanoparticles, up to 5×10?5 g, dispersed in a solid matrix. The maximal SAR ~?80 W/g has been obtained for the magnetite nanoparticle assembly investigated. 相似文献
4.
Specific heat capacity measurements of disk-shaped specimens have been performed with an apparatus based on thermal radiation calorimetry. The specimen surfaces were irradiated by two fiat heaters in a vacuum chamber so that homogeneous temperature distribution within an insulating specimen was achieved. Homogeneity was confirmed by computer simulation based on the control-volume method. The values of specific heat capacity were obtained by measurement of the specimen temperature, the time rate change of the specimen temperature, and the radiant power from the heater for heating and cooling modes. The specific heat capacities of Ni metal, A12O3 ceramic, MgO ceramic, and A1N ceramic were measured in the temperature range from 220 to 500°C to confirm the validity of this calorimeter. The relative error involved in the measured values was estimated to be ±3%. 相似文献
5.
Yoichi Okamoto Ryo Okada Takashi Nemoto Hiromichi Ohta Hiroaki Takiguchi 《International Journal of Thermophysics》2012,33(7):1219-1227
A novel method is proposed for the simultaneous calculation of thermal conductivity κ and specific heat capacity C. The new method is a combination of two established techniques. One is the photopyroelectric method for thermal diffusivity α and the other is the front-heat front-detection photothermoreflectance method for thermal effusivity b. After α, b, and density ρ measurements, C and κ are easily calculated as C?=?b α ?1/2 ρ ?1 and κ =?α 1/2 b. Test measurements on a commercial Si single-crystal wafer were performed to demonstrate that the method is sufficiently accurate. 相似文献
6.
In this paper, a way to modularize complex finite-element models is described. The modularization is done with temperature
fields that appear in high-precision measurement instruments. There, the temperature negatively impacts the achievable uncertainty
of measurement. To correct for this uncertainty, the temperature must be known at every point. This cannot be achieved just
by measuring temperatures at specific locations. Therefore, a numerical treatment is necessary. As the system of interest
is very complex, modularization is unavoidable to obtain good numerical results. 相似文献
7.
Thermal radiation calorimetry has been applied to measure the thermal conductivity and the specific heat capacity of an isolated solid specimen simultaneously. The system, in which a disk-shaped specimen and a flat heater are mounted in a vacuum chamber with the specimen heated on one face by irradiation, is presented. A theoretical formulation of the simultaneous measurement at quasi-steady state is described in detail. Noncontact temperature measurement of both specimen surfaces has been performed using pyrometers and a thermocouple set in the gap between the heater and the specimen. Pyroceram 9609 specimens, whose surfaces were blackened with colloidal graphite, were used in the measurement. The largest error involved in the noncontact temperature measurement is ±2°C in the range from 450 to 650°C. The resultant values of the specific heat capacity and the thermal conductivity deviate by about 10% from the recommended values for the Pyroceram specimen. 相似文献
8.
Thermal radiation calorimetry has been applied to measure the thermal diffusivity of a solid specimen, along with simultaneous measurements of specific heat capacity and thermal conductivity. In this calorimeter, a disk-shaped solid specimen whose surfaces are blackened is heated and cooled slowly on one face by irradiation in a vacuum chamber. A quasi-steady-state approximation in which a linear temperature gradient within the specimen was assumed is considered in the analysis. The validity of this approximation was confirmed by the results of computer simulation based on the control-volume method. Measurements of Pyroceram 9606 and Pyrex 7740 by use of thermocouples in the temperature range between 250 and 400°C gave values consistent with those obtained by previous authors, within experimental error, for all three thermophysical properties. 相似文献
9.
Fangyuan Sun Xinwei Wang Ming Yang Zhe Chen Hang Zhang Dawei Tang 《International Journal of Thermophysics》2018,39(1):5
Time-domain thermoreflectance (TDTR) technique is a powerful thermal property measurement method, especially for nano-structures and material interfaces. Thermal properties can be obtained by fitting TDTR experimental data with a proper thermal transport model. In a single TDTR experiment, thermal properties with different sensitivity trends can be extracted simultaneously. However, thermal conductivity and volumetric heat capacity usually have similar trends in sensitivity for most materials; it is difficult to measure them simultaneously. In this work, we present a two-step data fitting method to measure the thermal conductivity and volumetric heat capacity simultaneously from a set of TDTR experimental data at single modulation frequency. This method takes full advantage of the information carried by both amplitude and phase signals; it is a more convenient and effective solution compared with the frequency-domain thermoreflectance method. The relative error is lower than 5 % for most cases. A silicon wafer sample was measured by TDTR method to verify the two-step fitting method. 相似文献
10.
Jingjie Hu Izzet Altun Zefu Zhang Hassan Albadawi Marcela A. Salomao Joseph L. Mayer L. P. Madhubhani P. Hemachandra Suliman Rehman Rahmi Oklu 《Advanced materials (Deerfield Beach, Fla.)》2020,32(33):2002611
Transcatheter embolization is a minimally invasive procedure that uses embolic agents to intentionally block diseased or injured blood vessels for therapeutic purposes. Embolic agents in clinical practice are limited by recanalization, risk of non-target embolization, failure in coagulopathic patients, high cost, and toxicity. Here, a decellularized cardiac extracellular matrix (ECM)-based nanocomposite hydrogel is developed to provide superior mechanical stability, catheter injectability, retrievability, antibacterial properties, and biological activity to prevent recanalization. The embolic efficacy of the shear-thinning ECM-based hydrogel is shown in a porcine survival model of embolization in the iliac artery and the renal artery. The ECM-based hydrogel promotes arterial vessel wall remodeling and a fibroinflammatory response while undergoing significant biodegradation such that only 25% of the embolic material remains at 14 days. With its unprecedented proregenerative, antibacterial properties coupled with favorable mechanical properties, and its superior performance in anticoagulated blood, the ECM-based hydrogel has the potential to be a next-generation biofunctional embolic agent that can successfully treat a wide range of vascular diseases. 相似文献
11.
After a brief review of the hot-wire method, the design of an experiment that employs a two-wire technique is proposed. Several uncertainty sources are considered in order to define the optimal experimental conditions and evaluate the advantages of the two-wire technique. Convection and radiation effects and finite properties of the wires are discussed. The measurement uncertainties of the temperature rise, the heat flux generated by the hot wire, the time of the measurements, and the radial position of the second wire are considered. The influence of the uncertainty sources on the simultaneous estimation of thermal conductivity and specific heat capacity is analyzed for the hot-wire and two-wire techniques. 相似文献
12.
导热系数测量系统的数值模拟 总被引:1,自引:0,他引:1
对中国计量科学研究院的稳态保护热平板导热系数测量系统的温度场分布进行数值计算,并在此基础上对实验材料内测温点的选择进行了分析.结果表明,测温点复盖了实验材料内温度的最低和最高点,且呈线性分布,满足实验材料导热系数测量所需温度梯度测量的要求.此外,对热流密度测量的探讨发现,热流密度测量范围的确定是实现精密测量导热系数的关键. 相似文献
13.
Abstract It is an important task of nondestructive testing to determine the fiber orientation of reinforced polymers. One appropriate method, especially for carbon fibers, is phase-sensitive modulated thermography, where images of the phase angle and the amplitude of thermal waves at the surface of the sample are obtained. The anisotropy induced by the fibers results in elliptical contour lines whose direction and excentricity are correlated with the orientation of the fibers and the corresponding degree of thermal anisotropy, respectively. To correctly interpret the measurements one needs a theoretical model. Such a model is developed for layered media with different orientations in different depths. Using a Fourier transform one can reduce the heat conduction in three dimensions to a one-dimensional problem that can be solved analytically. Because the FFT algorithm is used for the numerical evaluation, the calculation of phase and amplitude images is very fast, with the computation time being approximately equal to the measurement time. The comparison with experiments for a test sample shows a good agreement between theory and measurement. 相似文献
14.
15.
T. Ohmura M. Tsuboi M. Onodera T. Tomimura 《International Journal of Thermophysics》2003,24(2):559-575
By applying the drop calorimeter method, a specific heat measuring apparatus that can be used in the temperature range from 100 to 1000°C has been developed. It is generally difficult to measure the specific heat of thermal insulation, because the insulation material is porous, and has low thermal conductivity and small heat capacity. In the present apparatus, the specific heat of thermal insulation is simply measured by dropping a heated specimen into water. The specific heat of the specimen obtained by the apparatus is the mean specific heat between the initial specimen temperature before dropping and the equilibrium water temperature after dropping. This apparatus was used to measure the mean specific heat of standard specimen SRM 720 Synthetic Sapphire (-Al2O3) whose reference values are certified by the National Institute of Standards and Technology (NIST). The measured values agreed well with the reference values within an error of ±10%. The specific heats of SiC refractory material, rock wool, alumina silica fiber, alumina silica board, calcium silicate, and SiO2 glass measured with this apparatus are also presented. 相似文献
16.
Measurement Techniques - The issue of the measurement of a gas-liquid medium by the mass component-by-component flow rate is examined. A thermal method is proposed for measurement of the... 相似文献
17.
为了研究和开发高产热率磁热疗用磁粉,综合分析了组分与粒径、制备方法、表面包覆对磁粉产热率的影响规律,对这些因素与产热率之间的定性关系进行了总结,并指出了其定量关系的研究方向。结果表明:不同组分的磁粉磁性能不同因而产热率不同,相同组分不同粒径和粒径分布的磁粉对产热率的影响存在一定的规律;制备方法影响粒径从而对产热率有影响;合理的包覆材料和包覆量可提高产热率。 相似文献
18.
19.
It is an important task of nondestructive testing to determine the fiber orientation of reinforced polymers. One appropriate
method, especially for carbon fibers, is phase-sensitive modulated thermography, where images of the phase angle and the amplitude
of thermal waves at the surface of the sample are obtained. The anisotropy induced by the fibers results in elliptical contour
lines whose direction and excentricity are correlated with the orientation of the fibers and the corresponding degree of thermal
anisotropy, respectively.
To correctly interpret the measurements one needs a theoretical model. Such a model is developed for layered media with different
orientations in different depths. Using a Fourier transform one can reduce the heat conduction in three dimensions to a one-dimensional
problem that can be solved analytically. Because the FFT algorithm is used for the numerical evaluation, the calculation of
phase and amplitude images is very fast, with the computation time being approximately equal to the measurement time. The
comparison with experiments for a test sample shows a good agreement between theory and measurement. 相似文献