| Efficient Algorithms for Structured Self-Calibration Problems |
JUL 2001 |
8 pages |
| Authors:
Alistair B. Forbes; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
 | Self-calibration techniques have been used extensively in co-ordinate metrology. At their most developed, they are able to extract all systematic error behaviour associated with the measuring instrument as well as determining the geometry of the artefact being measured. However, this is generally at the expense of introducing extra parameters leading to moderately large observation matrices. Fortunately, these matrices tend to have sparse, block structure in which the nonzero elements are ... |
|
| Generalised Gauss-Markov Regression |
JUL 2001 |
8 pages |
| Authors:
Alistair B. Forbes; Peter M. Harris; Ian M. Smith; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Experimental data analysis is an key activity in metrology, the science of measurement. It involves developing a mathematical model of the physical system in terms of mathematical equations involving parameters that describe all the relevant aspects of the system. The model specifies how the system is expected to respond to input data and the nature of the uncertainties in the inputs. Given measurement data, estimates of the model parameters are ... |
|
| Fixed- and Free-Knot Univariate Least-Squares Data Approximation by Polynomial Splines |
JUL 2001 |
16 pages |
| Authors:
Maurice Cox; Peter Harris; Paul Kenward; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Fixed- and free-knot least-squares data approximation by polynomial splines is considered. Classes of knot-placement algorithms are discussed. A practical example of knot placement is presented, and future possibilities in free-knot spline approximation are addressed. |
|
| Complex Media in Complex Fields: A Statistical Approach |
29 SEP 2000 |
4 pages |
| Authors:
L. R. Arnaut; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The use of statistical techniques to characterize composite materials systems and their use in complex electromagnetic environments is discussed. Examples of the calculation of uncertainties and distribution functions of wave statistics are given. |
|
| Time and Frequency Activities at the National Physical Laboratory |
Dec-1999 |
10 pages |
| Authors:
John A Davis; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The Time and Frequency Section of the National Physical Laboratory (NPL) has an active program of work in time and frequency metrology. This paper provides an overview of this section's principal activities. These include: maintenance and development of the national time scale UTC (NPL), development of a new cesium fountain clock, time-transfer activities, development of clock algorithms, technology-transfer activities, and time and frequency dissemination in the UK. |
|
| A Very-Short-Baseline Time Transfer Experiment Using Two Geodetic-Quality GPS Receivers and Carrier Phase Techniques |
Dec-1998 |
14 pages |
| Authors:
Jon D Clarke; John A Davis; Andrew Lowe; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| For over 10 years primary timing laboratories have used signals from the Global Positioning System (GPS) to compare atomic timescales. The method used, the common-view of GPS satellites, does not use the GPS system for its full potential. Recently, there has been much interest in using geodetic-quality GPS receivers for time transfer. The result has been a substantial improvement in the precision of the resulting time and frequency transfers. In ... |
|
| Preliminary Comparison of Two-Way Satellite Time and Frequency Transfer and GPS Common-View Time Transfer During the Intelsat Field Trial |
Dec 1995 |
13 pages |
| Authors:
J A Davis; W Lewandowski; J A DeYoung; D Kirchner; P Hetzel; G de Jong; A Soering; F Baumont; W Klepczynski; A McKinley; T Parker; K A Bartle; H Ressler; R Robnik; L Veenstra; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| For a decade and a half GPS Common-View time transfer has greatly served the needs of primary timing laboratories for regular intercomparisons of remote atomic clocks. However, GPS as a one-way technique has natural limits and may not meet all challenges of the comparison of the coming new generations of atomic clocks. Two-Way Satellite Time and Frequency Transfer (TWSTFT) is a promising technique which may successfully complement GPS. For two ... |
|
| Measurements of Thermophysical Properties in High Temperature Melts |
1994 |
|
| Authors:
K. C. Mills; R. F. Brooks; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
 | The levitated drop method has been used to measure the surface tensions, densities and enthalpies of liquid metals and alloys. undercoolings of 300 degrees c were recorded for pure metals but only 50 degrees c could be obtained for austenitic stainless steels. surface tensions for the under cooled state of pure fe, ni and au were found to be linear extrapolations of the data obtained for the liquid phase. densities ... |
|
| Modelling and Testing Fibre Reinforced Titanium for Design Purposes. |
1994 |
|
| Authors:
L. N. McCartney; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, cr mmc, designs, mmc, theoretical materials and material types:, fibers, ti matrix material characteristics and data fields:, failures testing and test conditions:, finite element methods, testing methods, miscellaneous and special technical terms:, micromechanical models, models. |
|
| Analysis of Hydrogen Atom Transport in a Two-Phase Alloy. |
1994 |
|
| Authors:
A. Turnbull; R. B. Hutchings; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The theoretical basis for analyzing hydrogen atom transport in a two-phase alloy is evaluated. experimental measurements of hydrogen atom transport in a duplex stainless steel, thermally treated to give a varying volume fraction of austenite, are described and analyzed to ascertain the relative effect on the effective diffusivity of interfacial trapping and of the reduced diffusivity but enhanced solubility of the austenite phase. the effective diffusivity of the as-received duplex ... |
|
| Uniaxial Testing of Particulate MMC. |
1994 |
|
| Authors:
B. Roebuck; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, data, experimental, mmc, mmc data materials and material types:, (sic)p/2014, (sic)p/2124, (sic)p/al, 2014 matrix, 2124 matrix, al alloys, particulates, sic particulates, sic/2014, sic/2124, sic/al material characteristics and data fields:, compression data, compressive strength, electrical resistivity, elongation data, failure data, fracture behaviors, modulus data, stress-strain behaviors, stress-strain curves, tensile behavior, tensile strength ... |
|
| Measurements of Thermophysical Properties in High Temperature Melts. |
1994 |
|
| Authors:
K. C. Mills; R. F. Brooks; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The levitated drop method has been used to measure the surface tensions, densities and enthalpies of liquid metals and alloys. Undercoolings of 300 C were recorded for pure metals but only 50 C could be obtained for austenitic stainless steels. Surface tensions for the undercooled state of pure Fe, Ni, and Au were found to be linear extrapolations of the data obtained for the liquid phase. Densities for the liquid ... |
|
| A Prediction Model for Noise from Low-Altitude Military Aircraft |
13 MAR 1993 |
7 pages |
| Authors:
B. F. Berry; J. D. Speakman; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| For a number of years, the National Physical Laboratory, supported by the Ministry of Defense, has been developing AIRNOISE, a mathematical model for computing aircraft noise contours. As part of the continuous programme of development of the model we were asked to extend it to include low-altitude military operations. The objective is to predict the complete time-history of the noise of these vary rapid events, thus providing information on onset ... |
|
| The Prediction of Cracking in Biaxially Loaded Cross-Ply Laminates Having Brittle Matrices |
93 |
|
| Authors:
L. N. McCartney; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| For a cross-ply laminate, it is shown how the dependence of the relevant thermoelastic constants on transverse crack density may be determined. the effect of biaxial loading on transverse cracking may be determined using energy balance concepts. the multiple transverse crack formation is considered which are formed simultaneously or progressively. non-linear stress/strain curves for axial and transverse loading assuming that the 0 degree plies remain undamaged. the effect of axial ... |
|
| Measurement of Properties of Brittle Matrix Composites |
93 |
|
| Authors:
R. Morrell; L. N. McCartney; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Based upon NPL experience of testing carbon fiber-reinforced glass matrix composites in unidirectional and cross-ply laminated forms, a review is presented covering those aspects of mechanical properties of brittle matrix composites. Specimen geometry, gripping techniques and alignment for tension testing are discussed. The limitations of flexure testing in possibly overestimating tensile properties are demonstrated for a material having a low interlaminar shear strength. Interpretation of strain gauge output is discussed ... |
|
| Terminology Requirements for Classification of Advanced Ceramics |
93 |
|
| Authors:
R. Morrell; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| This paper highlights some of the terminology problems that will arise in the English language during the development of a classification scheme for advanced ceramics. The uncontrolled development of terms in the technical and scientific literature over the last decade is reviewed, and some specific examples of the needs to define preferred terms are given. |
|
| The Prediction of Cracking in Biaxially Loaded Cross-Ply Laminates Having Brittle Matrices |
93 |
|
| Authors:
L. N. McCartney; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Assuming biaxial loading and perfect bonding conditions, it is shown how the dependence of the relevant thermoelastic constants on transverse crack density may be determined for a cross-ply laminate. It is shown using energy balance concepts how the effect of biaxial loading on transverse cracking may be determined, and how to account for thermal residual stresses. The formation of multiple transverse cracks is considered, either formed simultaneously or progressively, either ... |
|
| Standardisation Requirements for Ultrasonic C-Scanning of Polymer Matrix Composites - An Initial Assessment |
93 |
|
| Authors:
J. L. Lesmiarek-Hamid; G. D. Sims; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| As part of a wider programme aimed at new or improved test methods for quality control, qualification and design data purposes, an assessment has been undertaken on the 'standardization' requirements for the use of the ultrasonic C-scan technique for evaluating polymer matrix composites. This report is a compilation of that assessment, which covered current practices used by industry and requirements in terms of defect detection and measurement. The report contains ... |
|
| Ultrasonic Measurement Technique to Determine the State of Cure in Thermosetting Materials |
93 |
|
| Authors:
P. A. Gibbs; M. Rides; P. Williamson; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The report investigates the possibility of using ultrasonics as a nondestructive test method for determining the state of cure in thermosetting materials. Four variations of an unsaturated polyester moulding material were used to evaluate ultrasonics for cure monitoring. The test materials were each cured at a series of test temperatures up to 100 C. During cure the changes in velocity and attenuation of a transmitted ultrasonic pulse were measured at ... |
|
| Round Robin on Grain Size Measurement for Advanced Technical Ceramics. |
1993 |
|
| Authors:
L. J. M. G. Dortmans; R. Morrell; G. de With; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The results of a joint CEN/VAMAS round robin on grain size measurement for advanced technical ceramics have been analyzed. Twenty-five participants from Europe, USA and Japan employed a line and circle method for determination of the mean linear intercept length, and grid methods for determination of a grain size distribution. The results show that the scatter obtained for measurement of the mean linear intercept length and the grain size distribution ... |
|
| Validation of the Role of Bulk Charging of Hydrogen in the Corrosion Fatigue Cracking of a Low Alloy Steel. |
1993 |
|
| Authors:
A. J. Griffiths; R. B. Hutchings; A. Turnbull; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A high strength steel was fatigue tested to investigate the effect of bulk charging of hydrogen in corrosion cracking. AISI 4340 steel was tested in a corrosive environment of 3.5 wt. pct NaCl at-1100mv (SCE). It was found that bulk charging had a significant effect on the corrosion fatigue crack growth rate. |
|
| Development of a Cryogenic Hydrogen Maser at the NPL |
Dec-1992 |
10 pages |
| Authors:
R Mossavati; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| We have been developing a prototype Cold Hydrogen Maser (CHM) for the past year. The novel features of this CHM, which is designed to operate initially at 4.2 K, are the use of low loss alumina, and later sapphire, in the fabrication of the microwave cavity; possible use of superconductors for shielding; use of a cryogenic amplifier; possible novel coating material; and a reliable rf discharge circuit for the dissociation ... |
|
| Electro-Optic Sampling for the Measurement of the Response of Fast Oscilloscopes, |
22 MAY 1992 |
|
| Authors:
D. Henderson; A. G. Roddle; A. J. A. Smith; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A technique for measuring the impulse response and risetime of fast sampling oscilloscopes using picosecond electro-optic sampling is described. The results are compared with those obtained using a kick-out method and with measuring the spectral response in the frequency domain. |
|
| Measurement and Prediction of Noise from Low-Altitude Military Aircraft Operations, |
APR 1992 |
|
| Authors:
Bernard F. Berry; Richard C. Payne; Anthony L. Harris; Ralph J. Weston; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| In response to the rapid growth in demand for information on noise levels around military airfields in the UK, NPL developed AIRNOISE, a mathematical model for computing aircraft noise contours. since its first applications in 1981, the model has been used to determine zones of eligibility within the MoD compensation scheme. The model has been subject to continuous development, e.g. the incorporation of Harrier V/STOL operations. We have now extended ... |
|
| Advanced Materials for Critical Components in Industrial Gas Turbines |
92 |
|
| Authors:
Thomas B. Gibbons; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Combined-cycle plants for power production have big advantages over conventional power plants. To achieve acceptable efficiencies from combined- cycle plants turbine inlet temperature of > 1200 c are needed. This paper reviews recent advances in Ni-Cr base alloys and the potential for advanced materials for this use are discussed. Developments in coatings for resisting thermal effects and resisting aggressive environments is also covered. |
|
| Hydrogen Transport in Nickel-Base Alloys |
92 |
|
| Authors:
A. Turnbull; R. G. Ballinger; I. S. Hwang; M. M. Morra; M. Psaila-Dombrowski; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The electrochemical permeation technique has been used to characterize hydrogen transport and trapping in pure Ni and in alloys 600, X- 750, and 718 at 80 C; the "effective diffusivity" of hydrogen atoms in alloy 600 is reduced by a factor of about 5 compared to pure Ni; the "effective diffusivity" of hydrogen atoms in solution-annealed alloy X-750 is reduced by a factor of about 9 compared to that of ... |
|
| Test Methods for Environment Assisted Cracking |
92 |
|
| Authors:
A. Turnbull; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A review on various test methods to determine environment assisted cracking in metals is presented. Test methods, specimen geometry, environment, and advantages and disadvantages of the methods are discussed. |
|
| Mechanics for the Growth of Bridged Cracks in Composite Materials: Part I. Basic Principles |
92 |
|
| Authors:
L. Neil McCartney; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The fracture mechanics are established for a large plate containing an embedded crack of finite length taking account of: (1) the anisotropy of the material, (2) the effect of residual stresses arising from isothermal temperature changes, and (3) the effect of tractions applied to the crack- bridging ligaments. an expression for the crack-opening displacement distribution in terms of the crack-bridging traction distribution is derived together with the corresponding fracture criterion ... |
|
| Mechanics for the Growth of Bridged Cracks in Composite Materials: Part II. Applications |
92 |
|
| Authors:
L. Neil McCartney; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A fracture mechanics analysis valid for long cracks is applied to three crack-bridging problems that arise in the composites area, namely, (1) matrix cracking in perfectly bonded unidirectional composites, (2) transverse cracking in perfectly bonded cross-ply laminates, and (3) matrix cracking in unidirectional composites in which frictional slip occurs at fiber matrix interfaces governed by the constant shear-lag model of stress transfer. the fracture mechanics analysis is also applied to ... |
|
| The Formation of Aluminium Hydroxide in the Sliding Wear of Alumina |
92 |
|
| Authors:
M. G. Gee; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The wear of ceramics is often affected by tribochemical reactions with the surrounding environment. This paper examines the development of aluminum hydroxide interfacial layers in the wear of alumina at intermediate wear rates and the effect of these layers on wear and friction. Since the humidity of the surrounding atmosphere promotes the formation of these layers, a dramatic effect of humidity on the wear rate is brought about by the ... |
|
| Review of Corrosion Studies on Aluminium Metal Matrix Composites. |
1992 |
|
| Authors:
A. Turnbull; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, data, dr mmc, experimental, mmc, mmc data, review materials and material types:, (sic)w/2024, (sic)w/5456, (sic)w/6061, (sic)w/7075, (sic)w/al, 2024 matrix, 5456 matrix, 6061 matrix, 7075 matrix, al matrix, coatings, sic whiskers, sic/2024, sic/5456, sic/6061, sic/7075, sic/al, whiskers material characteristics and data fields:, corrosion, electrochemical data, potentiostatic polarization data parameter values relevant to ... |
|
| Parabolic Curved Crack Fronts in Fracture Toughness Specimens of Particulate Reinforced Aluminium Alloy Metal Matrix Composites. |
1992 |
|
| Authors:
B. Roebuck; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, calculations, data, mmc, mmc data materials and material types:, (sic)p/al, al alloys, al matrix, sic/al, material characteristics and data fields:, crack geometry, crack length data, fracture toughness, mechanical properties, modulus data, power law coefficient data, uts data miscellaneous and special technical terms:, crack lengths, particulate reinforcements, similar 010733. |
|
| Extending the Application Areas for Titanium Carbonitride Cermets. |
1992 |
|
| Authors:
E. B. Clark; B. Roebuck; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Titanium carbonitride cermets have been largely developed as cutting tool materials. however, their properties indicate that there is potential for extending the application areas to other tools. this report examines the industrial possibilities and indicates a number of alternative products which might benefit from the use of cermets., mmc, review, cermets, wc/co, zro2 reinforcements, mechanical properties, physical properties, wear resistances, machinings, near net shapes, p/m, agricultural applications, aircraft applications, aircraft ... |
|
| Theory of Stress Transfer in a 0 Degrees -90 Degrees -0 Degrees Cross-Ply Laminate Containing a Parallel Array of Transverse Cracks. |
1992 |
|
| Authors:
L. N. McCartney; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| STRESS TRANSFER, PLY LAMINATE, TRANSVERSE CRACKS, THERMAL RESIDUAL STRESS, THEORETICAL APPROACH, DISPLACEMENT COMPONENTS, INTERFACE CONDITIONS, STRESS-STRAIN-TEMPERATURE RELATIONS, Young's modulus, Poisson's ratio, thermal expansion coefficient, density of transverse cracks, 2- and 3-D models, glass fibre/epoxy, carbon fibre/epoxy, |
|
| An Intercomparison Involving PTB and NPL of Thermal Conductivity Measurements on Stainless Steel, Inconel and Nimonic Alloy Reference Materials, and an Iron Alloy |
91 |
|
| Authors:
John M. Corsan; Nigel J. Rudd; Wolfgang F. Hemminger; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The results of a thermal conductivity intercomparison involving NPL and PTB, carried out under a European Collaboration on Measurement Standards agreement (EUROMET), are given. The measurements were undertaken in apparatuses operating on the steady-state linear-heat-flow principle but differing markedly in their configurations and specimen requirements. Four materials, namely 310 stainless steel, Nimonic 755, Inconel 600, and a special cast iron, have been investigated over the temperature range from near 50 ... |
|
| An Intercomparison Involving PTB and NPL of Thermal Conductivity Measurements on Stainless Steel, Inconel and Nimonic Alloy Reference Materials, and an Iron Alloy. |
1991 |
|
| Authors:
John M. Corsan; Nigel J. Budd; Wolfgang F. Hemminger; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The results of a thermal conductivity intercomparison involving NPL and PTB, carried out under a European Collaboration on Measurement Standards agreement (EUROMET), are given. The measurements were undertaken in apparatuses operating on the steady-state linear-heat- flow principle but differing markedly in their configurations and specimen requirements. Four materials, namely 310 stainless steel, Nimonic 75, Inconel 600, and a special cast iron, have been investigated over the temperature range from near ... |
|
| Creep Deformation of Single Crystal Superalloys-Modelling the Crystallographic Anisotropy |
90 |
|
| Authors:
R. N. Ghosh; R. V. Curtis; M. McLean; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A generalized model of creep deformation in cubic single crystals is developed that considers the combined effects of viscous glide on two (or more) slip systems and accounts for tertiary creep by the accumulation of mobile dislocations with plastic strain; database of creep curves for the nickel-base single crystal superalloy SRR99 with the assumption that creep deformation occurs by glide on both the ?111! and ?001! systems is analyzed; a ... |
|
| The Measurement of Sliding Friction and Wear of Ceramics at High Temperature |
90 |
|
| Authors:
M. G. Gee; C. S. Matharu; E. A. Almond; T. S. Eyre; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A wear testing system is described which can be used to carry out sliding wear tests at temperatures up to 1500 C. The tests can be performed in air, vacuum or controlled atmospheres under applied loads in the range of 5 - 100 N and at speeds up to 1.5 m/s. The relative displacement of the two specimens and the frictional load generated between the two surfaces are monitored throughout ... |
|
| Determination of Strain in Textile Materials Using Moire Photography |
90 |
|
| Authors:
A. Kearney; c. forno; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Moire photography is appropriate for the measurement of deformation in textiles and is able to display graphically local strain disturbance around defects, such as holes or slits. The technique is non-invasive and because no prior preparation of the material is required, the deformations are accurately represented in the resulting fringe patterns. Automatic analysis of the patterns has revealed unusual strain distributions. (Author). |
|
| Plane Strain Fracture Toughness Test Procedures for Particulate Metal Matrix Composites. |
1990 |
|
| Authors:
B. Roebuck; J. D. Lord; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, data, dr mmc, mmc, mmc data materials and material types:, (sic)p/2014, (sic)p/2024, (sic)p/2124, (sic)p/2618, (sic)p/6061, (sic)p/7000, (sic)p/7075, (sic)p/7091, (sic)p/7475, (sic)p/a356, (sic)p/al, (sic)p/mb78, (sic)p/mb85, 2014 matrix, 2024 matrix, 2124 matrix, 2618 matrix, 6061 matrix, 7000 matrix, 7075 matrix, 7091 matrix, 7475 matrix, a356 matrix, a357 matrix, al matrix, in 9052 matrix, mb78 ... |
|
| Interference Films for Microstructural Characterization of Metal Matrix Composites |
89 |
|
| Authors:
E. G. Bennett; J. D. Lord; B. Roebuck; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A challenge which is difficult to meet by conventional techniques is presented when doing metallographic preparation and phase identification of metal matrix composites, especially when features other than the reinforcement and matrix, such as inclusions, must be identified and interfacial reaction zones characterized. a significant contribution to solving these problems is the use of thin oxide films to produce interference film colour contrast between different phases. the technique should be ... |
|
| Fractography of a SiC Particulate Reinforced Aluminium Metal Matrix Composite |
87 |
|
| Authors:
B. Roebuck; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The engineering potential of metal matrix composites (mmc) based on a combination of sic and an aluminium alloy is now widely recognized. to support this recognition an extensive literature has built up which is largely comprised of the results of mechanical property measurements and supporting microstructural studies. most of the published work has been on whisker or particulate reinforced alloys possibly because mmc of these kinds are more easily available ... |
|
| Mechanical Properties and Design of Sandwich Materials |
86 |
|
| Authors:
A. F. Johnson; G. D. Sims; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Where the main loads are flexural, sandwich materials consisting of a low density core with stiff skins offer considerable potential for weight saving in panel applications. steel/plastic laminates, integral skinned plastic foams and glass fiber-reinforced polyester skins with foamed plastic cores are sandwich materials which are of interest for car and van body panels, seat shells etc. in this paper, basic design formulae for the flexural stiffness and strength of ... |
|
| Influence of Monitoring Conditions on the Stress Wave Emission Data Recorded During Tensile Testing of a GRP |
JUN 79 |
35 pages |
| Authors:
G. D. Sims; D. G. Gladman; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| The stress wave or acoustic emission monitoring technique is a potentially valuable tool for the detection of failures in reinforced plastics. The monitoring conditions used may vary under different test circumstances and influence the actual data recorded. It is not yet possible to predict these effects from a basic understanding of the stress wave source event, its propagation and interaction with the detection system. In this report the results of ... |
|
| Debugging Computer Programs: A Survey With Special Emphasis on ALGOL |
JUN 1972 |
41 pages |
| Authors:
R. S. Scowen; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| This report considers the problems of debugging computer programs and some of the tools which can simplify the task. The main sections describe: (1) ways in which compilers can aid the debugging of programs, (2) ALGOL programs which can be used to determine the kinds of errors detected by an ALGOL compiler, (3) results of running the test programs on sixteen different compilers, (4) results obtained from a survey of ... |
|
| THE DESIGN AND PERFORMANCE OF PRESSURE-SCANNING SWITCHES EMPLOYING O-RING SEALING, |
14 FEB 1966 |
|
| Authors:
G. S. Smith; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| A description is given of a series of pressure-scanning switches designed to meet the problem of switching a multiplicity of pressures to the transducer used for measurement. Although designed for use on wind-tunnels such pressure switches would have applications in other directions in which accuracy and freedom from leakage are important over a range of pressures from several atmospheres down to a few micrometres of mercury. The performance of the ... |
|
| THE TURBULENCE STRUCTURE OF EQUILIBRIUM BOUNDARY LAYERS, |
21 JAN 1966 |
|
| Authors:
P. Bradshaw; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Measurements in boundary layers are discussed together with existing data and some new measurements in boundary layers in zero pressure gradient. It is shown that the small-scale turbulence is nearly universal, and that the large-eddy motion is nearly the same. Comparisons with the free mixing layer suggest that the large eddies consist of mixing jets. |
|
| Combining Time Transfer Measurements Using a Kalman Filter |
|
17 pages |
| Authors:
J A Davis; P W Stacey; P M Harris; M G Cox; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| Time transfer measurements made between UTC (k) timing laboratories are routinely performed using a variety of satellite-based methods. The National Physical Laboratory has undertaken a study of combining time transfer measurements from separate links between two laboratories, where each link measures the same clock difference. The aim is to produce a time series of (composite) time-transfer measurements that has appreciably less measurement noise than any of the component measurements. A ... |
|
| Results from the National Physical Laboratory GPS Common-View Time and Frequency Transfer Service |
|
13 pages |
| Authors:
J A Davis; S L Shemar; J D Clarke; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
|
| An overview is given of precise frequency and time transfer methods available to UK users. The use of the GPS common-view method to provide time and frequency links, traceable to national standards, is examined. The development of a new GPS common-view receiver is described along with NPL's new GPS common-view service. Methods used to characterize and validate these GPS common-view links are discussed. |
|
| Least-Squares Analysis of Two-Way Satellite Time and Frequency Transfer Measurements |
|
13 pages |
| Authors:
J A Davis; P M Harris; S L Shemar; M G Cox; NATIONAL PHYSICAL LAB TEDDINGTON (UNITED KINGDOM)
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| The least-squares analysts of Two-Way Satellite Time and Frequency (TWSTFT) data, with the aim of determining optimal estimates of phase and frequency offsets, is considered. An overview of the application of Gauss-Markov estimation to the analysts of a uniformly spaced time series is presented. Two aspects of TWSTFT data analysis are examined in depth. Firstly, measures based on second difference statistics for characterizing the consistently but unevenly spaced TWSTFT measurements ... |
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