Detection accuracy of target accelerations based on vortex electromagnetic wave in keyhole space

The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed. The spectrum spreads of different orbital angular momentum(OAM)modes in different non-line-of-sight situations are simulated. The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space. According to the research, ...     

Robust speech features representation based on computational auditory model

A speech signal processing and features extracting method based on computational auditory model is proposed. The computational model is based on psychological, physiological knowledge and digital signal processing methods. In each stage of a hearing perception system, there is a corresponding computational model to simulate its function. Based on this model, speech features are extracted. In each stage, the features in different kinds of level are extracted. A further processing for primary auditory spectrum based on lateral inhibition is proposed to extract much more robust speech features. All these features can be regarded as the internal representations of speech stimulation in hearing system. The robust speech recognition experiments are conducted to test the robustness of the features. Results show that the representations based on the proposed computational auditory model are robust representations for speech signals.     

Gas flow characteristics in straight silicon microchannels

Experiments have been conducted to investigate nitrogen gas flow characteristics through four trapezoidal silicon microchannels with different hydraulic diameters. The volume flow rate and pressure ratio are measured in the experiments. It is found that the friction coefficient is no longer a constant, which is different from the conventional theory. The characteristics are first explained by the theoretical analysis. A simplified rectangular model (rectangular straight channel model) is then proposed. The experimental results are compared with the theoretical predictions based on the simplified rectangular model and the two-dimensional flow between the parallel-plate model which was usually used. The difference between the experimental data and the theoretical predictions is found in the high-pressure ratio cases. The influence of the gas compressibility effect based on the Boltzmann gas kinetic analysis method is studied to interpret the discrepancy. We discuss two important factors affecting the application extent of different prediction models.     

Understanding the isoscaling relationship in the fissioning system with evaluated data

The isoscaling parameters α_(eval) in the fissioning systems,i.e.,those extracted from the Evaluated Nuclear Data Library(ENDFIB-VIII.0) and the Joint Evaluated Fission and Fusion File(JEFF-3.3),show an obvious difference from simple statistic model prediction where only the symmetry energy plays the dominant role.To explain the α_(eval) as a function of the charge number of the fission fragment,a statistic scission point model is adopted.Our analysis shows that the effects of the shell correction,nuclear shape deformation,and intrinsic temperature of fission fragments are indispensable as well as the symmetry energy.Furthermore,an alternative method for extracting the intrinsic temperatures of fission fragments is proposed based on the iso scaling relationship in fission fragments.The intrinsic temperatures of the light fragments are higher than those of the heavy fragments.     

Revisiting the island of hexadecapoledeformation nuclei in the A≈150 mass region: focusing on the model application to nuclear shapes and masses

Based on the potential-energy-surface calculation, the impact of different deformation degrees of freedom on a single-particle structure and binding energies in nuclei around ¹⁵²Nd, located on one of the hexadecapole-deformation islands, is analyzed in a multi-dimensional deformation space. Various energy maps, curves and tables are presented to indicate nuclear properties. The calculated equilibrium deformations and binding energies with different potential parameters are compared wi...     

RF electric field penetration and power deposition into nonequilibrium planar-type inductively coupled plasmas

The RF electric field penetration and the power deposition into planar-type inductively coupled plasmas in low-pressure discharges have been studied by means of a self-consistent model which consists of Maxwell equations combined with the kinetic equation of electrons. The Maxwell equations are solved based on the expansion of the Fourier--Bessel series for determining the RF electric field. Numerical results show the influence of a non-Maxwellian electron energy distribution on the RF electric field penetration and the power deposition for different coil currents. Moreover, the two-dimensional spatial profiles of RF electric field and power density are also shown for different numbers of RF coil turns.     

Molecular dynamic simulation of lubricant spreading： effect from the substrate and endbead

Molecular dynamic simulations based on a coarse-grained, bead-spring model are adopted to investigate the spreading of both nonfunctional and functional perfluoropolyether (PFPE) on solid substrates. For nonfunctional PFPE, the spreading generally exhibits a smooth profile with a precursor film. The spreading profiles on different substrates are compared, which indicate that the bead-substrate interaction has a significant effect on the spreading behaviour, especially on the formation of the precursor film. For functional PFPE, the spreading generally exhibits a complicated terraced profile. The spreading profiles with different endbeads are compared, which indicate that the endbead-substrate interaction and the endbead--endbead interaction, especially the latter, have a significant effect on the spreading behaviour.     

Meson Cloud Effect on △(1232) Resonance Transition Properties with a Relativistic Quark Model Approach

Based on a relativistic quark model approach, the transition properties of the first nucleon resonance △(1232), and the coupling constants gπNN, g△πN are investigated. Tvo different vays to remove the center of mass motion are considered. The results of the relativistic approaches with and without center ofmass correction are compared with those of nonrelativistic constituent quark model. Moreover, pion meson cloud effect on these calculated observables is explicitly addressed. Better results are obtained by taking the pion meson cloud into account.     

Study on the defect-related emissions in the light self-ion-implanted Si films by a silicon-on-insulator structure

This paper reports that the Si + self-ion-implantation are conducted on the silicon-on-insulator wafers with the 28 Si + doses of 7×10 12,1×10 13,4×10 13,and 3×10 14 cm 2,respectively.After the suitable annealing,these samples are characterized by using the photoluminescence technique at different recorded temperatures.Plentiful emission peaks are observed in these implanted silicon-on-insulator samples,including the unwonted intense P band which exhibits a great potential in the optoelectronic application.These results indicate that severe transformation of the interstitial clusters can be manipulated by the implanting dose at suitable annealing temperatures.The high critical temperatures for the photoluminescence intensity growth of the two signatures are well discussed based on the thermal ionization model of free exciton.     

Dosimetry Methods of Fast Neutron Using the Semiconductor Diodes

Semiconductor detectors based on a silicon pin diode are frequently used in the detection of different nuclear radiations. For the detection and dosimetry of fast neutrons, these silicon detectors are coupled with a fast neutron converter. Incident neutrons interact with the converter and produce charged particles that can deposit their energy in the detectors and produce a signal. In this study, three methods are introduced for fast neutron dosimetry by using the silicon detectors, which are： recoil proton spectroscopy, similarity of detector response function with conversion function, and a discriminator layer. Monte Carlo simulation is used to calculate the response of dosimetry systems based on these methods. In the different doses of an 241Am-Be neutron source, dosimetry responses are evaluated. The error values of measured data for dosimetry by these methods are in the range of 15-25%. We find fairly good agreement in the 241Am-Be neutron sources.     

Nuclear thermometry

Different approaches for measuring nuclear temperatures are described. The quantitative results of different thermometer approaches are often not consistent. These differences are traced back to the different basic assumptions of the applied methods. Moreover, an overview of recent theoretical investigations is given, which study the quantitative influence of dynamical aspects of the nuclear-reaction process on the extracted apparent temperatures. The status of the present experimental and theoretical knowledge is reviewed. Guidelines for future investigations, especially concerning the properties of asymmetric nuclear matter, are given.     

Peculiarities of isotopic temperatures obtained from p + A collisions at 1 GeV

Nuclear temperatures were extracted from fragment yields obtained in inclusive measurements of p+A collisions at 1 GeV. All thermometers based on double-isotopic yield-ratios provide temperatures T ≃ 4 MeV nearly independent on the target mass.     

Pt100温度计电阻和温度关系的拟合

全超导托卡马克(Tokam ak)装置EAST是国家"九五"大科学工程,温度参数是超导磁体最重要也是最基本的运行参数之一。工作在液氮温区的装置部件的温度通过铂电阻温度计Pt100进行监测。根据温度计的一组实测R-T数据进行拟合,得到与实际温度逼近度高的R-T关系函数,从而提高了EAST装置液氮温区温度测量的准确度。     

物理实验中温度测量的改进与应用

本分析了物理实验中玻璃温度计进行测温所存在的问题,根据半导体温度传感器工作原理设计并制作了一种新型的电子测温仪,该仪器具有精度高、响应快、读数方便以及便于二次开发等优点。     

Opportunities and problems in determining proton and light nuclear radii

We briefly review the so-called ‘proton puzzle’, i.e., the disagreement of the newly extracted value of the proton charge radius r _p from muonic hydrogen spectroscopy with other extractions, its possible significance and related problems. After describing the conventional theory to extract the proton radius from atomic spectroscopy we focus on a novel consistent approach based on the Breit equation. With this new tool, we confirm that the radius has indeed become smaller compared to the value extracted from scattering experiments, but the existence of different theoretical approaches casts some doubt on the accuracy of the new value. Precision measurements in atomic physics do provide the opportunity to extract light nuclear radii but the accuracy is limited by the methods of incorporating the nuclear structure effects.     

Low temperature thermometry, 1 to 30 K

The current interest and activity in thermometry between 4 and 20 K is due primarily to the development and subsequent commercial availability of 4-terminal germanium resistors as reproducible and sensitive thermometers. These have assumed the same role below 20 K as platinum resistance thermometers have above 20 K. Thermometric techniques in this low temperature region have evolved from insensitive alloy thermometers (such as constantan) to the use of high sensitivity (but sometimes irreproducible) carbon radio resistors to the introduction of the first suitably-doped germanium resistance thermometers by Kunzler and his co-workers at the Bell Telephone Laboratories.¹ Thermometers of this type now are manufactured by several different concerns and they are used routinely at temperatures from 0.1 to 40 or 50 K with mK sensitivity and reproducibility. These thermometers have brought about a considerable rethinking and simplification of cryogenic techniques; and, in many instances, they are used from 1 to 20 K (or higher) with calibrations which are certified by or traceable to Standards Laboratory scales, with little or no provision made for checks of the calibration by the user.     

Nuclear temperature measurements with the double isotope ratio technique: Influence of the experimental conditions

The dependence of the nuclear temperatures of highly excited systems, extracted by means of the double ratios of the emitted isotopes, on the experimental conditions is investigated. Experimental data obtained in the Xe+Cu 30 MeV/nucleon reaction are used to study the sensitivity of the method and the effects of the energy thresholds on the obtained temperature values. We find that the temperatures extracted using the He/Li ratios can be strongly influenced by the experimental energy thresholds which are different for different elements. These distortions depend on the velocity of the emitting system and on the detection angle and therefore particular care is needed in the choice of the detectors in those experiments in which velocities are low and angles are large. The use of four isotopes of the same element make negligible such effects. Received: 6 October 1999 / Accepted: 28 May 2000     

Thermometry by micro and nanodevices

In this paper we briefly discuss the current provisional temperature scale of 2000 (PLTS-2000) for low temperatures. Electronic thermometry is presented and discussed, focusing on its potential in verifying and realizing a future temperature scale. The discussion covers secondary thermometers such as NIS and SIS thermometers and noise, shot noise and Coulomb blockade primary thermometers. The last one is discussed in more detail.     

Verification of the inverted temperature gradient condition via molecular dynamics simulation

We perform molecular dynamics simulations to verify the critical condition for the existence of an inverted temperature profile in the vapor between two liquid slabs at slightly different temperatures. Reasonable agreement is found between the kinetic theory based condition and simulations. The deviation from theory can be explained by deviation from ideal gas behavior on which the kinetic condition is based and by deviation in the MD from diffuse boundary conditions, which are used in deriving the kinetic condition.