Effective concentration of electrons in metals upon measurements via positron annihilation spectroscopy

Calculations are performed together with the summarization of published data on the measurement of positron annihilation rates in a number of simple substances. The information potential of different methods underlying positron annihilation spectroscopy is analyzed as applied to the study of condensed matter. The features of the mechanism of positron annihilation in metals are discussed. The possibility of investigating the electronic and defect structures of metals and alloys using the method of the time distribution of annihilation photons is considered.     

Estimation of inaccuracies of thermocouple measurements of the temperature profile in pyrolyzed solid substances

Thermal interaction of a thermocouple embedded into a solid substance pyrolyzed by an external heat source with the thermal wave propagating inward the substance from the pyrolysis surface is considered. Numerical simulations show that a heat sink through thermocouple wires inward the substance occurs because of a significant difference in thermal conductivities of the solid substance and thermocouple material, which leads to substantial changes in thermojunction, thus, distorting thermocouple data.     

Surface free energies of solid metals: Estimation from liquid surface tension measurements

An equation is derived on semi-theoretical grounds which expresses the solid-vapour surface free energy as a function of the liquid surface tension and the solid-liquid interfacial free energy. A means of calculating reliable values for the solid-liquid energy is presented, which then allows an accurate estimate of solid surface energy at the melting temperature, T_m, to be made for the large number of elements for which dependable liquid surface tension data exist. A method of estimating surface entropy is presented, and has been used to calculate the energies typical of “average”, high-index surfaces at temperatures ranging from 0 K to T_m. It is felt that this paper describes the most accurate method presently available for the calculation of the surface energy of solids in the absence of direct experimental measurement.     

Scheme for realizing entanglement concentration via generalized measurements

How to concentrate non-maximally entangled states for quantum communication is a fundamental problem in quantum information. In this paper, we will apply generalized measurements to entanglement concentration of known non-maximally entangled pure states in arbitrary dimensional system. How to design the generalized measurements for the unambiguous discrimination of linearly independent non-orthogonal states is crucial for the concentration of the known non-maximally entangled states. The result shows that, any known non-maximally entangled pure state (for arbitrary dimensional system) can be transformed to the maximally entangled state only by introducing a qubit as ancilla and a joint unitary transformation operation on one of the entangled particles and the ancilla. In addition, because the less entangled state of each fail round will be re-concentrated too, the entanglement waste during the concentration process will be greatly reduced.     

Neutron Method for Measuring the Volume Distribution of Hydrogen in Various Objects

Physics of Atomic Nuclei - A method for measuring the volume distribution of hydrogen in various objects by means of tagged neutron probing is proposed. The existing probing methods, which permit...     

Estimation of binding energy between a dislocation and vacancy and concentration of vacancies from ultrasonic attenuation measurements

Cottrell’s binding energy between a dislocation and vacancy and concentration of vacancies has been calculated using ultrasonic attenuation measurements in single crystals of pure tin at 300K for frequencies varying from 3 to 50 MHz and at different dislocation densities.     

Pressure measurements of the solid hydrogen quadrupolar glass

We report measurements of the pressure and (?P/?T)_V in samples of solid hydrogen of orthohydrogen concentrations of 40–55% and 150 mK ? T ? 1 K. No evidence of a first or second order phase transition is seen at temperatures associated with the formation of a quadrupolar glass.     

Reflection 4f coherent imaging technique for measurements of optical nonlinearity

A one-laser-shot measurement technique, which can characterize the nonlinear optical properties of the film prepared on the opaque substrates conveniently and exactly, is presented. This method is based on the reflection 4f coherent imaging system with phase objects. The proposed technique is examined in the case of a novel ultrathin film [CuPc(COONa)₄]/PDDA coated on an opaque silicon substrate with 532 nm picosecond laser pulses. By measuring the reflected intensity, but not the transmitted one, we verify both nonlinear absorption and refraction of the coated thin film. This progress obviously ensures that nonlinearities caused by reflection of opaque surfaces are measurable.     

Effective Mode Volume of Nanoscale Plasmon Cavities

The controlled squeezing of electromagnetic energy into nanometric volumes via surface plasmon-polariton excitations in plasmonic nanoresonators is analyzed using the concept of an effective electromagnetic mode volume V _eff, while taking careful account of the plasmon-polariton dispersion and the electromagnetic energy stored in the metal. Together with the quality factor Q of the cavity resonance, this enables a comparison with dielectric optical cavities, where V _eff is limited by diffraction. For a Fabry–Perot type planar metallic cavity, a one-dimensional analytic model as well as a three-dimensional finite-difference time-domain simulation reveal that V _eff is not bounded by diffraction, and that Q/V _eff increases for decreasing cavity size. In this picture, matter–plasmon interactions can be quantified in terms of Q and V _eff, and a resonant cavity model for the enhancement of spontaneous Raman scattering is presented.     

The Effective Dynamics of the Volume Preserving Mean Curvature Flow

We consider the dynamics of small closed submanifolds (‘bubbles’) under the volume preserving mean curvature flow. We construct a map from (\(\text {n}+1\))-dimensional Euclidean space into a given (\(\text {n}+1\))-dimensional Riemannian manifold which characterizes the existence, stability and dynamics of constant mean curvature submanifolds. This is done in terms of a reduced area function on the Euclidean space, which is given constructively and can be computed perturbatively. This allows us to derive adiabatic and effective dynamics of the bubbles. The results can be mapped by rescaling to the dynamics of fixed size bubbles in almost Euclidean Riemannian manifolds.     

Comparison of different CARS variants for concentration measurements in combustion research

Summary Different strategies are discussed to use CARS spectroscopy for measuring mole fractions of combustion species. The influence of various physical parameters on both shape and total intensity of spectral bands is studied. Two variants for concentration measurements are compared based either on spectralshape analysis or frequency-integrated intensity ratios. The analysis leads to the conclusion that concentrations from a spectral-shape fit are more sensitive to inaccuracies of input parameters than band intensities. Paper presented at the ?XI European CARS Workshop?, Florence, Italy, 23–25 March, 1992.     

用激光测量蔗糖溶液的旋光率及其浓度

采用激光测量了蔗糖溶液的旋光率及其浓度,利用计算机实时采集数据并输出图形,使实验具有直观、准确度高、操作简便等特点.     

Elastic-constant measurements in solid argon at the melting point

The velocities of ultrasonic waves have been measured in solidified argon in the pressure range up to 6 kb (600 MPa). Shear wave velocities could be measured to temperatures very close to the melting point, such that both liquid and solid phases coexisted, $\text{(T?T}{}_{\mathrm{<mtext>m</mtext>}}\text{)}\text{T}{}_{\mathrm{<mtext>m</mtext>}}\text{<10}{}^{-5}$. The measurements show that neither the shear velocity tends to zero nor its derivative with temperature tends to -8 as T→T_m.     

Frequency-stabilized cavity ring-down spectrometer for high-sensitivity measurements of water vapor concentration

We present a portable spectrometer that uses the frequency-stabilized cavity ring-down spectroscopy technique capable of high-precision measurements of trace water vapor concentration. Measuring one of the strongest rovibrational transitions in the ν₁+ν₃ water vapor combination band near ˜ν=7181.156 cm^-1, we compare spectroscopic and thermodynamic determinations of trace water vapor in N₂, and find systematic differences attributable to water vapor background effects and/or uncertainties in line intensities. We also compare the frequency-stabilized ring-down method with other cavity ring-down approaches that are based on unstabilized probe lasers and unstabilized ring-down cavities. We show that for the determination of water vapor concentration, the frequency-stabilized cavity ring-down method has the minimum measurement uncertainty of these techniques. The minimum noise-equivalent absorption coefficient of the spectrometer was 1.2×10^-10 cm^-1 Hz^-1/2, which further corresponds to a minimum detectable water vapor mole fraction equal to 0.7×10^-9 for an absorption spectrum of 10 minutes duration. PACS 33.20.-t; 33.70.Jg; 33.70.Fd; 42.62.Fi     

The calibration of the solid state nuclear track detector LR 115 for radon measurements

An experimental calibration of indoor room and outdoor soil detector devices which are based on LR 115 as sensitive element has taken place at the Swedish Radiation Protection Institute in Stockholm (Sweden) in 1994 and 1996, at the Physikalisch-Technischen Bundesanstalt in Braunschweig (Germany) in 1997 and at the Umweltforschungszentrum Leipzig-Halle (Germany) in 1997. Special properties of the used solid state nuclear track detector (SSNTD) material LR 115^* have been measured to define the application of the experimental calibration.     

A KLM-circuit model of a multi-layer transducer for acoustic bladder volume measurements

In a preceding study a new technique to non-invasively measure the bladder volume on the basis of non-linear wave propagation was validated. It was shown that the harmonic level generated at the posterior bladder wall increases for larger bladder volumes. A dedicated transducer is needed to further verify and implement this approach. This transducer must be capable of both transmission of high-pressure waves at fundamental frequency and reception of up to the third harmonic. For this purpose, a multi-layer transducer was constructed using a single element PZT transducer for transmission and a PVDF top-layer for reception. To determine feasibility of the multi-layer concept for bladder volume measurements, and to ensure optimal performance, an equivalent mathematical model on the basis of KLM-circuit modeling was generated. This model was obtained in two subsequent steps. Firstly, the PZT transducer was modeled without PVDF-layer attached by means of matching the model with the measured electrical input impedance. It was validated using pulse-echo measurements. Secondly, the model was extended with the PVDF-layer. The total model was validated by considering the PVDF-layer as a hydrophone on the PZT transducer surface and comparing the measured and simulated PVDF responses on a wave transmitted by the PZT transducer. The obtained results indicated that a valid model for the multi-layer transducer was constructed. The model showed feasibility of the multi-layer concept for bladder volume measurements. It also allowed for further optimization with respect to electrical matching and transmit waveform. Additionally, the model demonstrated the effect of mechanical loading of the PVDF-layer on the PZT transducer.