Journal of Research of the National Institute of Standards and Technology最新文献

{"title":"The New Kilogram Definition and its Implications for High-Precision Mass Tolerance Classes.","authors":"Patrick J Abbott,&nbsp;Zeina J Kubarych","doi":"10.6028/jres.118.016","DOIUrl":"https://doi.org/10.6028/jres.118.016","url":null,"abstract":"<p><p>The SI unit of mass, the kilogram, is the only remaining artifact definition in the seven fundamental units of the SI system. It will be redefined in terms of the Planck constant as soon as certain experimental conditions, based on recommendations of the Consultative Committee for Mass and Related Quantities (CCM) are met. To better reflect reality, the redefinition will likely be accompanied by an increase in the uncertainties that National Metrology Institutes (NMIs) pass on to customers via artifact dissemination, which could have an impact on the reference standards that are used by secondary calibration laboratories if certain weight tolerances are adopted for use. This paper will compare the legal metrology requirements for precision mass calibration laboratories after the kilogram is redefined with the current capabilities based on the international prototype kilogram (IPK) realization of the kilogram. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"353-8"},"PeriodicalIF":1.5,"publicationDate":"2013-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.6028/jres.118.016","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34200334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kiloampere, Variable-Temperature, Critical-Current Measurements of High-Field Superconductors.","authors":"L F Goodrich, N Cheggour, T C Stauffer, B J Filla, X F Lu","doi":"10.6028/jres.118.015","DOIUrl":"10.6028/jres.118.015","url":null,"abstract":"<p><p>We review variable-temperature, transport critical-current (I c) measurements made on commercial superconductors over a range of critical currents from less than 0.1 A to about 1 kA. We have developed and used a number of systems to make these measurements over the last 15 years. Two exemplary variable-temperature systems with coil sample geometries will be described: a probe that is only variable-temperature and a probe that is variable-temperature and variable-strain. The most significant challenge for these measurements is temperature stability, since large amounts of heat can be generated by the flow of high current through the resistive sample fixture. Therefore, a significant portion of this review is focused on the reduction of temperature errors to less than ±0.05 K in such measurements. A key feature of our system is a pre-regulator that converts a flow of liquid helium to gas and heats the gas to a temperature close to the target sample temperature. The pre-regulator is not in close proximity to the sample and it is controlled independently of the sample temperature. This allows us to independently control the total cooling power, and thereby fine tune the sample cooling power at any sample temperature. The same general temperature-control philosophy is used in all of our variable-temperature systems, but the addition of another variable, such as strain, forces compromises in design and results in some differences in operation and protocol. These aspects are analyzed to assess the extent to which the protocols for our systems might be generalized to other systems at other laboratories. Our approach to variable-temperature measurements is also placed in the general context of measurement-system design, and the perceived advantages and disadvantages of design choices are presented. To verify the accuracy of the variable-temperature measurements, we compared critical-current values obtained on a specimen immersed in liquid helium (\"liquid\" or I c liq) at 5 K to those measured on the same specimen in flowing helium gas (\"gas\" or I c gas) at the same temperature. These comparisons indicate the temperature control is effective over the superconducting wire length between the voltage taps, and this condition is valid for all types of sample investigated, including Nb-Ti, Nb3Sn, and MgB2 wires. The liquid/gas comparisons are used to study the variable-temperature measurement protocol that was necessary to obtain the \"correct\" critical current, which was assumed to be the I c liq. We also calibrated the magnetoresistance effect of resistive thermometers for temperatures from 4 K to 35 K and magnetic fields from 0 T to 16 T. This calibration reduces systematic errors in the variable-temperature data, but it does not affect the liquid/gas comparison since the same thermometers are used in both cases. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"301-52"},"PeriodicalIF":1.5,"publicationDate":"2013-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4487313/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34200333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Registration of Six Degrees of Freedom Data with Proper Handling of Positional and Rotational Noise.","authors":"Marek Franaszek","doi":"10.6028/jres.118.013","DOIUrl":"https://doi.org/10.6028/jres.118.013","url":null,"abstract":"<p><p>When two six degrees of freedom (6DOF) datasets are registered, a transformation is sought that minimizes the misalignment between the two datasets. Commonly, the measure of misalignment is the sum of the positional and rotational components. This measure has a dimensional mismatch between the positional component (unbounded and having length units) and the rotational component (bounded and dimensionless). The mismatch can be formally corrected by dividing the positional component by some scale factor with units of length. However, the scale factor is set arbitrarily and, depending on its value, more or less importance is associated with the positional component relative to the rotational component. This may result in a poorer registration. In this paper, a new method is introduced that uses the same form of bounded, dimensionless measure of misalignment for both components. Numerical simulations with a wide range of variances of positional and rotational noise show that the transformation obtained by this method is very close to ground truth. Additionally, knowledge of the contribution of noise to the misalignment from individual components enables the formulation of a rational method to handle noise in 6DOF data. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"280-91"},"PeriodicalIF":1.5,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.6028/jres.118.013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34200331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recommendations for Improving Consistency in the Radiation Fields Used During Testing of Radiation Detection Instruments for Homeland Security Applications.","authors":"L Pibida,&nbsp;M Mille,&nbsp;B Norman","doi":"10.6028/jres.118.014","DOIUrl":"https://doi.org/10.6028/jres.118.014","url":null,"abstract":"<p><p>Several measurements and calculations were performed to illustrate the differences that can be observed in the determination of exposure rate or ambient dose equivalent rate used for testing radiation detection systems against consensus standards. The large variations observed support our recommendation that better consistency in the test radiation fields can be achieved by specifying the source activity and testing distance instead of the field strength. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"292-300"},"PeriodicalIF":1.5,"publicationDate":"2013-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.6028/jres.118.014","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34200332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Case Study of Performance Degradation Attributable to Run-Time Bounds Checks on C++ Vector Access.","authors":"David Flater, William F Guthrie","doi":"10.6028/jres.118.012","DOIUrl":"10.6028/jres.118.012","url":null,"abstract":"<p><p>Programmers routinely omit run-time safety checks from applications because they assume that these safety checks would degrade performance. The simplest example is the use of arrays or array-like data structures that do not enforce the constraint that indices must be within bounds. This report documents an attempt to measure the performance penalty incurred by two different implementations of bounds-checking in C and C++ using a simple benchmark and a desktop PC with a modern superscalar CPU. The benchmark consisted of a loop that wrote to array elements in sequential order. With this configuration, relative to the best performance observed for any access method in C or C++, mean degradation of only (0.881 ± 0.009) % was measured for a standard bounds-checking access method in C++. This case study showed the need for further work to develop and refine measurement methods and to perform more comparisons of this type. Comparisons across different use cases, configurations, programming languages, and environments are needed to determine under what circumstances (if any) the performance advantage of unchecked access is actually sufficient to outweigh the negative consequences for security and software quality. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"260-79"},"PeriodicalIF":1.5,"publicationDate":"2013-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4487316/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34200330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hazardous Continuation Backward in Time in Nonlinear Parabolic Equations, and an Experiment in Deblurring Nonlinearly Blurred Imagery.","authors":"Alfred S Carasso","doi":"10.6028/jres.118.010","DOIUrl":"https://doi.org/10.6028/jres.118.010","url":null,"abstract":"<p><p>Identifying sources of ground water pollution, and deblurring nanoscale imagery as well as astronomical galaxy images, are two important applications involving numerical computation of parabolic equations backward in time. Surprisingly, very little is known about backward continuation in nonlinear parabolic equations. In this paper, an iterative procedure originating in spectroscopy in the 1930's, is adapted into a useful tool for solving a wide class of 2D nonlinear backward parabolic equations. In addition, previously unsuspected difficulties are uncovered that may preclude useful backward continuation in parabolic equations deviating too strongly from the linear, autonomous, self adjoint, canonical model. This paper explores backward continuation in selected 2D nonlinear equations, by creating fictitious blurred images obtained by using several sharp images as initial data in these equations, and capturing the corresponding solutions at some positive time T. Successful backward continuation from t=T to t = 0, would recover the original sharp image. Visual recognition provides meaningful evaluation of the degree of success or failure in the reconstructed solutions. Instructive examples are developed, illustrating the unexpected influence of certain types of nonlinearities. Visually and statistically indistinguishable blurred images are presented, with vastly different deblurring results. These examples indicate that how an image is nonlinearly blurred is critical, in addition to the amount of blur. The equations studied represent nonlinear generalizations of Brownian motion, and the blurred images may be interpreted as visually expressing the results of novel stochastic processes. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"199-217"},"PeriodicalIF":1.5,"publicationDate":"2013-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.6028/jres.118.010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34031221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Critical Compilation of Energy Levels, Spectral Lines, and Transition Probabilities of Singly Ionized Silver, Ag II.","authors":"Alexander Kramida","doi":"10.6028/jres.118.009","DOIUrl":"https://doi.org/10.6028/jres.118.009","url":null,"abstract":"<p><p>All available experimental measurements of the spectrum of the Ag(+) ion are critically reviewed. Systematic shifts are removed from the measured wavelengths. The compiled list of critically evaluated wavelengths is used to derive a comprehensive list of energy levels with well-defined uncertainties. Eigenvector compositions and level designations are found in two alternate coupling schemes. Some of the older work is found to be incorrect. A revised value of the ionization energy, 173283(7) cm(-1), equivalent to 21.4844(8) eV, is derived from the new energy levels. A set of critically evaluated transition probabilities is given. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"168-98"},"PeriodicalIF":1.5,"publicationDate":"2013-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.6028/jres.118.009","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34031220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long-Wavelength Beam Steerer Based on a Micro-Electromechanical Mirror.","authors":"Anthony B Kos,&nbsp;Eyal Gerecht","doi":"10.6028/jres.118.006","DOIUrl":"https://doi.org/10.6028/jres.118.006","url":null,"abstract":"<p><p>Commercially available mirrors for scanning long-wavelength beams are too large for high-speed imaging. There is a need for a smaller, more agile pointing apparatus to provide images in seconds, not minutes or hours. A fast long-wavelength beam steerer uses a commercial micro-electro-mechanical system (MEMS) mirror controlled by a high-performance digital signal processor (DSP). The DSP allows high-speed raster scanning of the incident radiation, which is focused to a small waist onto the 9mm(2), gold-coated, MEMS mirror surface, while simultaneously acquiring an undistorted, high spatial-resolution image of an object. The beam steerer hardware, software and performance are described. The system can also serve as a miniaturized, high-performance long-wavelength beam chopper for lock-in detection. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"125-39"},"PeriodicalIF":1.5,"publicationDate":"2013-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.6028/jres.118.006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34031217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Eddy Current Rail Inspection Using AC Bridge Techniques.","authors":"Ze Liu,&nbsp;Andrew D Koffman,&nbsp;Bryan C Waltrip,&nbsp;Yicheng Wang","doi":"10.6028/jres.118.007","DOIUrl":"https://doi.org/10.6028/jres.118.007","url":null,"abstract":"<p><p>AC bridge techniques commonly used for precision impedance measurements have been adapted to develop an eddy current sensor for rail defect detection. By using two detection coils instead of just one as in a conventional sensor, we can balance out the large baseline signals corresponding to a normal rail. We have significantly enhanced the detection sensitivity of the eddy current method by detecting and demodulating the differential signal of the two coils induced by rail defects, using a digital lock-in amplifier algorithm. We have also explored compensating for the lift-off effect of the eddy current sensor due to vibrations by using the summing signal of the detection coils to measure the lift-off distance. The dominant component of the summing signal is a constant resulting from direct coupling from the excitation coil, which can be experimentally determined. The remainder of the summing signal, which decreases as the lift-off distance increases, is induced by the secondary eddy current. This dependence on the lift-off distance is used to calibrate the differential signal, allowing for a more accurate characterization of the defects. Simulated experiments on a sample rail have been performed using a computer controlled X-Y moving table with the X-axis mimicking the train's motion and the Y-axis mimicking the train's vibrational bumping. Experimental results demonstrate the effectiveness of the new detection method. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"140-9"},"PeriodicalIF":1.5,"publicationDate":"2013-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.6028/jres.118.007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34031218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Weathering Patterns of Ignitable Liquids with the Advanced Distillation Curve Method.","authors":"Thomas J Bruno, Samuel Allen","doi":"10.6028/jres.118.003","DOIUrl":"10.6028/jres.118.003","url":null,"abstract":"<p><p>One can take advantage of the striking similarity of ignitable liquid vaporization (or weathering) patterns and the separation observed during distillation to predict the composition of residual compounds in fire debris. This is done with the advanced distillation curve (ADC) metrology, which separates a complex fluid by distillation into fractions that are sampled, and for which thermodynamically consistent temperatures are measured at atmospheric pressure. The collected sample fractions can be analyzed by any method that is appropriate. Analytical methods we have applied include gas chromatography (with flame ionization, mass spectrometric and sulfur chemiluminescence detection), thin layer chromatography, FTIR, Karl Fischer coulombic titrimetry, refractometry, corrosivity analysis, neutron activation analysis and cold neutron prompt gamma activation analysis. We have applied this method on product streams such as finished fuels (gasoline, diesel fuels, aviation fuels, rocket propellants), crude oils (including a crude oil made from swine manure) and waste oils streams (used automotive and transformer oils). In this paper, we present results on a variety of ignitable liquids that are not commodity fuels, chosen from the Ignitable Liquids Reference Collection (ILRC). These measurements are assembled into a preliminary database. From this selection, we discuss the significance and forensic application of the temperature data grid and the composition explicit data channel of the ADC. </p>","PeriodicalId":17039,"journal":{"name":"Journal of Research of the National Institute of Standards and Technology","volume":"118 ","pages":"29-51"},"PeriodicalIF":1.5,"publicationDate":"2013-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4487305/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34029180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}