摘要:

A practical method is described to find automatically the calibration coefficients and residual nonorthogonality of a tunneling microscope scanner. As initial data, the coordinates of three atoms were used forming a triangle in a highly oriented pyrolytic graphite surface appearing in the form of a spatially geometrical measure. A recognition procedure is described which can be applied to determine the lateral coordinates of the atoms. Length and orientation distortions were calculated, estimates of calibration errors were given and the requirement on the nonorthogonality limit was formulated for manipulator a given that ensures measurements of the predetermined accuracy. The sensitivity of the method to a noise in atom coordinates was determined. Experimental data showing the practical suitability of the method developed are presented. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149091

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An optical scanning mechanism capable of dual-dimension scanning is presented. The mechanism uses a piezoelectric element to drive a V-shaped reflecting mirror surface through two pairs of elastic beams. The design entails the use of various vibration modes to reflect the incident light in orthogonal directions. The design, fabrication, and mechanical, electrical, and optical performance of this scanning mechanism are presented. The scanning sensitivities of 88.8 and 19.3 &mgr;rad/V in each scanning direction are measured when operated at frequencies of 23.8 and 48.8 kHz, respectively. The capability of fine scanning sensitivity, high operating frequency, and wide scanning range is applicable for fine adjustment of the laser beam. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149092

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have addressed essential problems for the determination of the size distribution and volume density of crystal defects by bright field infrared laser interferometer [optical precipitate profiler (OPP)]. By taking into consideration the influences of the intensity profile and phase shift of the incident laser beam along the optical axis, we developed a new statistical data processing method to determine the true size distribution and volume density of the crystal defects from the raw OPP data. Using this method we evaluated the size distribution and volume density of oxygen precipitates introduced in a CZ–Si wafer and the validity of the new method was confirmed by comparing the obtained results with those obtained by the etching method and transmission electron microscopy. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149093

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This article describes an experimental technique to measure simultaneously the thermal diffusivity and thermal conductivity of nonmetallic materials. The method is applied to a large thickness sample and uses a single temperature sensor located at the heating surface of a perspex sample. In addition the golden section optimization technique is used with parameter estimation for minimizing two different objective functions. Each of the thermal properties is estimated in a different way. The diffusivity estimation uses a correlation function estimator between heat flux and temperature while a square function error of experimental and estimated temperatures is the objective function used for determining the conductivity. A comparison with the guarded hot plate method indicates a deviation of 2.1&percent; of the thermal conductivity. An error analysis for both properties is also presented. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149094

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Based on our technique of fine temperature control, we developed a new “millikelvin (mK)-stabilized cell” having a function of sensing thermal anomalies for the detailed x-ray diffraction study of solid phase transitions. It is easily mounted on a commercially available goniometer head. The performance was tested usingCsPbCl3single crystal, in which a phase transition is known to take place at 320 K (47°C) from tetragonal to cubic. An abrupt variation in the distance between some two reciprocal points in the precession pattern was clearly detected in a 0.1 K temperature range centered at 47°C along with two thermal anomalies observed. The “mK-stabilized cell” will be very useful to investigate a mechanism of phase transitions occurring in a narrow temperature range. ©1998 American Institute of Physics

ISSN:0034-6748    

DOI:10.1063/1.1149114

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Multi-dimensional tomographic-based data sets are now being used to calculate physical properties and transport coefficients. This article presents a method, based upon the propagation of uncertainties, for determining the valid range of values for the property calculated. The example used to demonstrate the method is the application of nuclear magnetic resonance imaging (NMRI) to measure fluid velocity profiles for the calculation of fluid viscosities. The resolution of the velocity data is shown to be the most important factor for implementation of the NMRI-based viscometry technique. Uncertainties in the velocity measurement are propagated through the shear viscosity calculation to estimate the standard deviation of the shear viscosities. Two data sets, experimental velocity resolutions of 0.6 and 1.5 mm/s, demonstrate that when the shear viscosity standard deviation exceeds 30&percent; of the predicted shear viscosity value we observe a discrepancy between the data and viscosities obtained using conventional rheometrical instruments. Removal of those data points with a standard deviation exceeding 30&percent; of the shear viscosity value provided data that agreed to within 6&percent; of conventional rheometry data. The estimation methodology for property uncertainty can be applied prior to experimental measurements to design for accuracy over a specific range of the property to be determined. These findings are not restricted to NMRI and should hold for other tomography-based viscometers ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149113

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A high-accuracy, calibration-free technique to measure the electrical conductivity of liquids has been developed — the coaxial cylinders technique. Because the liquid under investigation comes in contact only with metal and not with anything dielectric, this technique enables the measurement of the electrical properties of liquids inaccessible by classical high-accuracy techniques. Two coaxial cylindrical electrodes are immersed in the liquid to an arbitrary initial depth, and ac impedance is measured over a wide range of frequency. This process is repeated at many immersions. The electrical conductivity is calculated from the change in measured conductance with immersion. This technique was validated in 1.0, 0.1, and 0.01 D KCl(aq) solutions at room temperature. Measured electrical conductivities were within±0.5&percent;of the standard reference values. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149095

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This work describes the construction of an experimental setup — a mass spectrometer coupled microreactor — which makes possible the simultaneous monitoring of the electric resistance of a solid sensor sample and the composition of the near surface gas atmosphere. The information obtained from the constant voltage resistance measurement is complemented by the information about of the near-sensor gas composition. The evaluation of both sets of results offers insight into the mechanism of the sensing process. As an example, the results obtained on an undoped, oven-heatedCeO2sensor sample is presented, in a CO and oxygen containing atmosphere between 25 and 900 °C. It was found that between 200 and 300 °C the decrease in the sensor resistance is mainly due to the CO chemisorption. In this temperature range the oxidation of CO is negligible. The CO sensitivity decreases with the temperature in the whole interval examined. However, its value is the highest in this temperature range due to the relatively high surface coverage. In the 300–400 °C range the most important process is the gas phase oxidation of the CO; about 85&percent; of it is transformed. The transformation of CO leads to a smaller surface coverage, and so to a decreasing — but still high enough — sensitivity. A further temperature rise hinders the CO chemisorption and the lack of chemisorption results in no CO sensitivity. It is noted that even the catalytic effect of theCeO2sample is important in the studied system; its effect on the near-sensor gas composition is easily detectable. The maximum catalytic activity ofCeO2in the CO oxidation was found to be around 400 °C. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149115

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The use of high-temperature superconductors in electric power components requires the knowledge of their alternating current (ac) losses. Methods are therefore needed to characterize the conductors with respect to their ac losses under applicationlike conditions. In this article we describe a calorimetric setup for ac loss measurements on long length high-temperature superconductors carrying ac transport currents in ac external magnetic fields at variable temperatures. The variable temperature is achieved by a thermal connection between the sample and a cooling machine. Current in copper coils generates the magnetic field parallel to the plane of the tape and perpendicular to the transport current. This current can be induced in the coil-formed sample. Two slightly different methods are used to determine the ac losses, one in which the temperature rise of the sample, caused by the ac losses, is compared to the temperature rise caused by a reference heater and another in which the increase in power dissipation of the sample is compensated for by a reduction of the power dissipation in the heater. Typical results of the ac loss measurements are presented. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149096

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The design of a new radiative heater for the growth of oxide thin films is presented. A blackbody cavity approach has been used to eliminate the large temperature variations usually observed during the growth of highTc(HTC) superconducting thin films. Results show that this simple and inexpensive design enables one to work without the need forin situmonitoring and constant adjustment of the substrate temperature. The performance of the new heater is demonstrated by the growth of excellent quality HTC thin films. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149097

出版商:AIP    

年代:1998

数据来源: AIP