Page images
PDF
EPUB

electronic coordinates derived from fundamental microscopic theory for a structural map of these alloy systems.

18358. Berger, M. J., Planned compilation of stopping power and range data, Proc. Sixth Symp. on Microdosimetry, Brussels, Belgium, May 22-26, 1978, J. Booz and H. G. Ebert, Eds., I, 639-649 (Harwood Academic Publishers, Ltd., London, England, 1978).

Key words: a-particles; electrons; heavy ions; international commission on radiation units and measurements; protons; stopping power.

In recent years there has been a steady accumulation of new information about the penetration of charged particles through matter. The ICRU has appointed a committee that is charged with the task of digesting this new information and of preparing an up-to-date compilation of stopping-power and range data for electrons, protons and heavy ions, with emphasis on the needs of medical physics and radiobiology. The purpose of this talk is to indicate the plans, priorities and initial activities of the committee, and to discuss some recent development in stopping-power research which will facilitate the committee's

task.

18359. Callcott, T. A., Arakawa, E. T., Ederer, D. L., Emission and absorption x-ray edges of Li, Phys. Rev. B 16, No. 12, 5185-5192 (Dec. 15, 1977).

Key words: core hole lifetime; core hole relaxation; K xray absorption spectrum; K x-ray emission spectrum; many body effects; rhonon interactions.

The K x-ray emission edge of Li is measured between 85 and 490 K and analyzed to obtain the temperature dependences of the edge position and of a Gaussian edge-broadening function. Full width at half-maximum edge widths range from 0.22 ± 0.05 eV at 85 K to 0.38 ± 0.05 eV at 440 K. Edge positions shift from 54.81 ± 0.02 eV at 85 K to 54.86 ± 0.02 eV at 440 K and to 54.91 ± 0.02 eV after melting. Emission and absorption spectra measured with the same spectrometer establish a 0.10 ± 0.02 eV separation between the emission and absorption edges. These results are compared with recent theories describing incomplete lattice relaxation about the core hole. We conclude that for a core-hole lifetime of 0.016 to 0.030 eV the theories give a satisfactory explanation of the premature peak in the emission spectra. We suggest also that phonon-core-hole interactions provide the dominant edge-broadening mechanism, and that many-body effects are small.

18360. Caswell, R. S., Coyne, J. J., Influence of nuclear data on calculations of neutron energy deposition, Proc. Third Symp. on Neutron Dosimetry in Biology and Medicine, Neuherberg/München, Federal Republic of Germany, May 23-27, 1977, G. Burger and H. G. Ebert, Eds., pp. 29-43 (Commission of the European Communities, DirectorateGeneral, Scientific and Technical Information Management, Bâtiment Jean Monnet, Luxembourg, 1978).

Key words: kerma factors; neutron cross section; neutron energy deposition; nuclear data; nuclear reactions; secondary particle spectra.

It is often assumed that if one has a set of evaluated neutron cross sections such as ENDF/B-IV, that it is then possible to determine physical properties of the neutron energy deposition process, such as kerma factors and secondary particle spectra, unambiguously. While this is true for some elements, it is not true for others. In the case of kerma factor calculations, nart of the calculational problem caused by lack of data can be side-stepped by use of the relation: (kerma) = (energy available)-(energy carried off by secondary neutrons)-(energy carried off by gamma rays). In all cases the energy available is known.

In elastic scattering the scattered neutron energy is known (if the angular distribution is known) and there are no gamma rays. For (n, charged particle) reactions with cross sections given to known final states the second term is zero and the third term is determined by the cross section. In other reactions, such as (n,n' α) (n,n' p), and (n,n' 3a), the kerma factor is very sensitive to information about the outgoing neutron energy (direct reaction versus boil-off reaction), and to the final states assumed (i.e. energy carried off by gamma rays). We will discuss some "global" assumptions made in kerma factor calculations-uniform assumptions based on reasonable nuclear physics used when specific data is not available. In the case of secondary particle spectra, the above simplifying relation usually does not work since energy distributions of all secondary charged particles are needed. Here the choice of nuclear reaction mechanisms is crucial. Examples will be given of alternatives and choices made for specific nuclides.

In the higher energy regions where evaluated cross sections are not available, there are several ways to go. One is essentially an extrapolation of data at lower energies using what guides (total cross sections, optical model calculations) are available. A second method is the use of optical model and nuclear statistical model cross sections to produce the complete set of data needed. A third model is the use of the Intranuclear Cascade Model (INC). Results of some of these methods will be compared.

18361. Cavallo, L., Ehrlich, M., Hutchinson, J. M. R., Traceability in ionizing radiation measurements systems, Proć. Int. Symp. on National and International Standardization of Radiation Dosimetry, Atlanta, GA, Dec. 5-9, 1977, IAEA-SM222/18, 1, 65-87 (International Atomic Energy Agency, Vienna, Austria, 1978).

Key words: dose; ionizing; radioactivity; standards; testing; traceability.

There are many demands for traceability to the national radiation measurements systems (NRMS) stemming from groups such as the regulatory agencies, state health laboratories, commercial suppliers of radioactive materials and their customers, hospitals and their patients. The United States National Bureau of Standards supervises and administers measurements assurance programmes for radiation therapy departments, the radiopharmaceutical industry, federal agencies charged with radiation and radioactivity monitoring and surveillance, and for manufacturers and users of radioactivity standards, and administers to the radioactivity measurements assurance programme of the College of American Pathologists. These efforts are described and the results are tabulated. 18362. Durst, R. A., Potential pitfalls in the use of ion-selective electrode-reference electrode pairs, Paper in Theory, Design, and Biomedical Applications of Solid State Chemical Sensors, pp. 155-163 (CRC Press, Inc., West Palm Beach, FL, 1978). Key words: electrodes, errors; electrodes, ion-selective; electrodes, reference; ion-selective electrodes; reference electrodes; sensors, chemical.

Ion-selective electrodes have demonstrated unique features for the measurement of a variety of ionic and gaseous species. While the advantages of these electrodes are widely known and appreciated, it is usually not until one is actually using these sensors that the problems and pitfalls become apparent and may result in serious errors and considerable aggravation. The causes of these problems are almost as varied as the sensors and the samples, but several common sources can be identified: interferences and/or fouling of the electrode, sample matrix effects, reference electrode instability, and improper calibration of the measurement system. These pitfalls are discussed in

some detail with suggestions for overcoming or minimizing the problems and their associated errors.

These sensors can be a useful and convenient means for the determination and monitoring of selected species, but only if the potential pitfalls are recognized and eliminated. More than any other modern analytical technique, ion-selective electrodes require a sound knowledge of solution chemistry in order to achieve the maximum effectiveness of these sensors.

18363. Holton, J. K., Interfacing building design and solar energy research and standards, Proc. Joint Conf. 1976 of the American Section of the Int. Solar Energy Society and the Solar Energy Society of Canada, Winnipeg, Canada, Aug. 1520, 1978, pp. 74-82 (American Section of the Int. Solar Energy Society, Cape Canaveral, FL, 1978).

Key words: building research; NBS solar standards projects; solar energy.

An extensive program of solar energy research and standards development has been undertaken by the National Bureau of Standards in support of the national effort to expedite the introduction of solar usage. The communication between researchers and the building community, who will utilize the products of this research, is of critical importance for effective conduct of this program. This paper examines a number of the programs being conducted at NBS, identifies the intended user groups, and describes some of the paths of communication that are being used. It is hoped that a clearer understanding of the research/user linkage will lead to more effective communication between those working in the field.

18364. Keller, R. A., Travis, J. C., Recent advances in analytical laser spectroscopy, Paper in Analytical Laser Spectroscopy, N. Omenetto, Ed., Chapter 8, 493-538 (John Wiley & Sons, Inc., New York, NY, 1979).

Key words: atomic flame fluorescence; intracavity absorption; isotope analysis; laser analysis; laser fluorescence; laser spectroscopy; microfluorescence; saturation spectroscopy; tunable laser.

A review of new, potentially analytical applications of lasers is presented. Topics include: description of laser properties, direct absorption measurement, frequency modulation, intracavity absorption, fluorescence measurements, saturation spectroscopy, isotope analysis, CARS, flame fluorescence, condensed phase fluorimetry, energy state population distribution, and microfluorescence.

18365. Tewksbury, S. K., Meyer, F. C., Rollenhagen, D. C., Schoenwetter, H. K., Souders, T. M., Terminology related to the performance of S/H, A/D, and D/A circuits, IEEE Trans. Circuits Syst. CAS-25, No. 7, 419-426 (July 1978).

Key words: analog-to-digital converter; digital-to-analog converter; IEEE subcommittee; performance specifications; sample/hold circuit; standards; terminology.

A review of terminology, often misunderstood or misused, concerning the performance of sample-and-hold (S/H) circuits, analog-to-digital (A/D) converters, and digital-to-analog (D/A) converters is presented. Although a set of general definitions is presented, definitions consistent with the needs of users and with the measurement capabilities of manufacturers are not easily obtained. The definitions presented have been selected by the authors from among definitions suggested by members of the Subcommittee on A/D and D/A Converters of the IEEE Network Applications and Standards Committee. It is hoped that others interested in the problem of terminology will submit their opinions to one of the authors before any final recommendations are made by the Subcommittee.

18366. Younger, S. M., Wiese, W. L., Systematic trends for the oscillator strengths of resonance transitions in the Cu and Zn isoelectronic sequences, Phys. Rev. A 18, No. 5, 2366-2368 (Nov. 1978).

Key words: Cu sequence; oscillator stength; Zn sequence.

New systematic trend curves for the oscillator stengths of the 4s-4p resonance transitions of Cu- and Zn-like ions have been derived from a critical analysis. This analysis takes into account recent theoretical results as well as a simulation study of cascade effects in beam-foil experiments which showed that the currently available experimental data for high ions may be too low by as much as 40-70%. The new analysis yields reliable interpolated data for many ions within the Cu and Zn isoelectronic sequences.

18367. Chang, S. J., Zapas, L. J., Several relations for comparison of a general rate fluid and the BKZ fluid, Proc. VIIth Int. Congress of Rheology, Gothenburg, Sweden, Aug. 23-27, 1976, C. Klason and J. Kubát, Eds., pp. 566-567 (Tages-Anzeiger/Regina-Druck, Zurich, Switzerland, 1976).

Key words: BKZ fluid; constitutive equation; non-linear flow histories; rate fluid; simple shear.

In the framework of a general rate fluid and a BKZ fluid the stress components for a shearing flow history can be obtained from a knowledge of the behavior in other flow histories. In some cases the two fluids are indistinguishable. To avoid specialized forms of either fluid we obtained a set of rheological relations (relations which are independent of the material properties) for two flow histories, stress relaxation after shear and suddenly applied steady shear. It is found that the relations are identical for the two fluids only in shear rates in the range of a second order fluid.

18368. Christ, B. W., Smith, J. H., Brady, C. H., Analyzing fire extinguisher failures, Met. Prog. 114, No. 8, 28-32 (Dec. 1978).

Key words: circumferential tearing; fire extinguisher; hydrostatic pressure testing; intergranular cracking stainless steel; sensitized metal.

Hydrostatic pressure testing and metallographic examination was carried out on stainless steel inverting type fire extinguishers to determine the cause of failures by circumferential tearing at the dome end of the extinguishers. Intergranular cracking of sensitized metal, perhaps over a period of 15-20 years, seemed to be the cause of these failures.

18369. Kaufman, V., Sugar, J., Analysis of the spectrum of four-times-ionized lutetium (Lu v), J. Opt. Soc. Am., 68, No. 11, 1529-1541 (Nov. 1978).

Key words: energy levels; lutetium; spectrum; wavelengths. Spectra of Lu obtained with a sliding spark discharge at peak currents of 50-500 A were recorded with a 10.7 m normal incidence spectrograph in the range of 500-2100 Å. Intercomparison of spectra revealed a distinct separation of Lu II, IV, and v, the first two of which have already been analyzed. The present work contains an interpretation of Lu v in which 419 lines are classified as transitions among 136 energy levels of the 4ƒ13, 4ƒ125d, 4ƒ126s, and 4ƒ126p configurations. Calculated energy levels and eigenvectors, obtained with fitted values for the radial integrals, are given.

18370. Olsen, H. A., Maximon, L. C., High-frequency limit of bremsstrahlung, Phys. Rev. A 18, No. 6, 2517-2522 (Dec.

1978).

Key words: atomic screening effects; bremsstrahlung high frequency limit; bremsstrahlung spectrum tip; continuum x rays; Coulomb field; non-relativistic bremsstrahlung.

It is shown that, contrary to common belief, the. bremsstrahlung cross section vanishes at the high-frequency limit for a neutral atom. The Sommerfeld finite value at the upper limit is valid only for atomic fields falling off as for large distances, i.e., for ionized atoms. The behavior of the cross section at the high-frequency limit is closely connected to the position of bound states close to the continuum limit for the atom. An explicit calculation is performed for a particular screened atomic field. It is shown that the resonances in the bremsstrahlung cross section close to the high-frequency limit found experimentally by Liefield et al., can be explained as final-state resonance scattering.

18371. Seltzer, S. M., Hubbell, J. H., Berger, M. J., Some theoretical aspects of electron and photon dosimetry, Proc. National and International Standardization of Radiation Dosimetry, Atlanta, GA, Dec. 5-9, 1977, IAEA-SM-222/05, II, 3-43 (International Atomic Energy Agency, Vienna, Austria, 1978).

Key words: absorbed dose; attenuation coefficient; detector response functions; dosimetry; electrons; foil transmission; photons; stopping power; transport theory.

The dosimetry standardization programme at the National Bureau of Standards (NBS) has a number of theoretical components. These include the compilation of standard cross-section data sets, the theoretical analysis of detector response to various radiations, the spectral and directional characterization of radiation sources, and the determination of absorbed-dose distributions in irradiated media. This paper describes recent results, with emphasis on photon and electron dosimetry. A discussion is given of some recent developments pertaining to photon attenuation coefficients and electron stopping powers. Response functions are presented for intrinsic germanium detectors (used to measure the output of diagnostic X-ray machines) and for sodium iodide detectors (used to measure the spectral characteristics of one of the NBS "Co irradiation facilities). As examples of source characterization, calculations are described pertaining to the passage of high-energy electron beams through foils. Consideration is given to thin foils used to spread the electron beam, and to thick foils used as bremsstrahlung converters. The results include the energy spectra and angular distributions of the transmitted electrons and emergent bremsstrahlung photons. An example of the calculation of absorbed-dose distributions is given for irradiation of a carbon phantom by a Co gamma-ray beam.

18372. Alperin, H. A., Pickart, S. J., Rhyne, J. J., Small-angle neutron scattering from rare-earth iron alloys (Extended Abstract), J. Appl. Cryst. 11, 648-649 (1978).

Key words: amorphous alloys; magnetic partides; magnetism; neutron scattering; rare earths; small angle scattering.

Small angle neutron scattering (SANS) has been used to investigate the onset of magnetic order and some aspects of the magnetic microstructure in a series of bulk amorphous rareearth iron alloys prepared by dc rapid sputtering.

18373. Cahn, J. W., Allen, S. M., A microscopic theory for domain wall motion and its experimental verification in Fe-Al alloy domain growth kinetics, J. Phys. (Paris), Colloq. C7, 38, No. 12, C7-51-C7-54 (Dec. 1977).

Key words: alloys; antiphase domains; critical behavior; domain growth; domain walls; ordering; surface mobility.

A microscopic theory for curved antiphase domain wall motion in ordered structures leads to a prediction that velocity is proportional to mean curvature. Unlike previous models, the velocity is not proportional to domain wall free energy. Experimental results on domain growth in ordered FeAl alloys over a range of temperatures, times and compositions, are consistent with the theory. In the vicinity of the critical temperature where domain wall free energy tends to zero, domain growth is not slowed.

18374. Steenbergen, C., Rush, J. J., Neutron scattering study of the methyl-group reorientations and the low temperature phase transition in (CH3)2SnF2, J. Chem. Phys. 70, No. 1, 5056 (Jan. 1, 1979).

Key words: activation energy; methyl group; neutron scattering; potential barrier; quasielastic scattering; reorientation; residence time; tunneling.

The reorientation of the methyl groups in solid (CH,),SnF, has been investigated by neutron quasielastic scattering. It is found that a phase transition occurs in the solid at about 70 K, which might be of second order. The shape of the measured quasielastic lines can be described by instantaneous threefold jumps of the methyl groups. From the derived residence times as a function of temperature below the phase transition, an activation energy Ea/ks 250 K and a residence time at infinite temperatures T, = 0.10 ps have been determined. Above the phase transition the activation energy is at least a factor 2 smaller.

=

18375. Breiter, D. N., Roush, M. L., Trace element characterization of thin polymer films by proton-induced x-ray emission spectrometry, Macromolecules 10, No. 4, 868-870 (Aug. 1977).

Key words: copper; iron; plastic; polymer; proton-induced x-ray fluorescence; thin films; trace element analysis; trace element concentrations; zinc.

Proton-induced x-ray fluorescence is a particularly wellsuited technique for the simultaneous quantitative analysis of trace elements in thin polymer films. Since the sample is thin and of low atomic number, matrix effects due to proton energy loss and x-ray self absorption are small. Sensitivities are sufficient to allow for the 5-10 minute analysis of films of 1 mg/cm2 areal density for iron, copper and zinc at concentration of several ng/cm2.

18376. Chang, S. S., Automated adiabatic calorimetric system for heat capacity measurement, Proc. 7th Symp. on Thermophysical Properties, Gaithersburg, MD, May 10-12, 1977, pp. 75-82 (The American Society of Mechanical Engineers, New York, NY, 1977).

Key words: adiabatic calorimetry; automated calorimetry; calorimetry; heat canacity; measurement automation; pTerphenyl; thermodynamic properties; A-type transition.

A fully automated adiabatic calorimetric system for heat capacity measurements from 2 to 380 K is described. The system includes both automatic analog adiabatic shield control and automatic digital data acquisition and experimental control. The system incorporates a self-balancing, high resolution potentiometric system as the main instrument. The automated system is capable of making continuous, unattended calorimetric measurements over long periods of time. The precision of the heat capacity measurements is about 0.02% when the temperature increment of each measurement is greater than 1 K. For higher temperature resolutions the precision of the present system is apparently limited by an uncertainty of 0.2 mK in the estimation of the temperature increment.

18377. Chang, S. S., Heat capacity and thermodynamic properties of solid synthetic sapphire, a-A↳O,, Proc. 7th Symp. on Thermophysical Properties, Gaithersburg, MD, May 10-12, 1977, pp. 83-90 (The American Society of Mechanical Engineers, New York, NY, 1977).

Key words: alumina; aluminum oxide; calorimetry; corundum; enthalpy; heat capacity; sapphire; specific heat; standard reference materials; thermodynamic properties. Heat capacity of the National Bureau of Standards calorimetric Standard Reference Material 720, synthetic Sapphire (aAl2O), for heat capacity and enthalpy, has been measured from 8 to 375 K with a fully-automated adiabatic calorimeter. By combining the results from this work and those from NBS high-temperature drop calorimetry on the same sample, thermodynamic functions of a-Al2O,, from 0 to 2250 K, based entirely on NBS experimental measurements on SRM 720, are derived.

18378. Cohen, J., Methodology of product life testing, Proc. 27th Meeting of the Mechanical Failures Prevention Group, Gaithersburg, MD, Nov. 1-3, 1977, T. R. Shives and W. A. Willard, Eds., pp. 31-41 (National Bureau of Standards, Gaithersburg, MD, May 1978).

Key words: consumer products; reliability engineering; testing methodology; useful life.

A methodology was formulated for estimating, through laboratory testing, useful life and associated performance of consumer products. Excerpts from two key parts-concepts of reliability engineering and procedure to guide the formulation of tests-are given here. Criteria for assessing tests are presented.

18379. Durst, R. A., Cali, J. P., Recommended reference materials for realization of physicochemical properties, Pure Appl. Chem. 50, E. F. G. Herington, Ed., 1485-1517 (1978).

Key words: activity coefficient; hydrogen ion activity; ionic activity; ionic activity scales; pD; pD scale; pH; pH scales; potentiometric ion activity.

This report is a survey and compilation of pH and ionic activity reference materials in use throughout the world. An introductory section discusses the differences in the national pH scales and provides a brief review of the equations which define these operational scales. The major part of this report tabulates the reference materials (composition and values as a function of temperature) used to realize the pH scales presently being employed in Germany, Hungary, Japan, Poland, Rumania, USSR, UK, and the USA. Datą sheets are also included for the PD and ionic activity reference materials used in the United States. This report was prepared under the auspices of the IUPAC Commission 1.4 Subcommittee on Calibration and Test Materials.

18380. Joseph, J. T., Hybl, A., Flynn, J. H., Differential scanning calorimetry studies of some analogs for the lipid component of biological membranes, Chem. Phys. Lipids 22, 239-243 (1978).

Key words: benzyl substituted diglycerides; differential scanning calorimetry; heat of fusion; lecithins; lipids; melting temperature; metastable states; phenyl substituted diglycerides; phospholipids; polymorphism; recrystallization temperature.

The melting behavior of members of newly synthesized series of rac-1,2-diglycerides with substituted phenyl groups or a benzyl group on the 3-position was investigated with differential scanning calorimetry (DSC). Solution crystallized samples had

single melting temperatures, higher than those of the quenched or annealed specimens. Quenched samples exhibited polymorphic behavior; some melted and recrystallized during slow heating. This behavior is similar to that of lecithins and suggests that X-ray diffraction studies of the substituted diglycerides may be useful for understanding membrane structure and functions.

18381. Treado, M. J., Diamond, J. J., Taggart, H. E., Jones, R. N., Saulsbury, L. F., Workman, J. L., NILECJ standard for body-worn FM transmitters, NILECJ-STD-0214.00, 20 pages (U.S. Department of Justice, Law Enforcement Assistance Administration, National Institute of Law Enforcement and Criminal Justice, Washington, DC, Dec. 1978).

Key words: body-worn transmitters; communications equipment; FM transmitters; law enforcement equipment; standards; surveillance; undercover equipment.

This is a voluntary national standard that establishes minimum performance requirements and methods of test for body-worn FM transmitters used by law enforcement personnel in undercover operations. The standard specifies the test equipment needed, the test methods, and the minimum performance requirements necessary for satisfactory performance.

18382. Wang, F. E., Mitchell, M. A., Sutula, R. A., Holden, J. R., Bennett, L. H., Crystal structure study of a new compound Li,B, J. Less-Common Met. 61, 237-251 (1978).

Key words: crystal; diffraction; Li,B, neutron powder; structure; x ray.

A study has been made of the crystal structure of Li̟B by x-ray, neutron powder diffraction techniques and NMR (nuclear magnetic resonance) measurements. The crystal structure thus determined is rhombohedral (R3) in its short-range ordered state and bcc (123) in its statistically disordered (longrange) state.

The boron atomic arrangement consists of a coplanar triangular cluster of four boron atoms which are situated at the vertices and the center of the triangle. This boron atomic arrangement has no precedent either in metal-borides or boronhydrides. There is a strong indication that: 1) electrons on the boron atoms at the vertices partially transferred (approx. 1.3 electrons) to the boron atom at the center of the triangle in Li,B1, 2) the amount of electron transfer increases with temperature rise.

Lithium atoms on the other hand, cluster in a bitetrahedral form (two tetrahedrons sharing a common face) with five lithium atoms occupying the vertices. This lithium atomic arrangement is in part similar to the hexagonal structure of lithium at low temperature.

18383. Watson, R. E., Bennett, L. H., A Mulliken electronegativity scale and the structural stability of simple compounds, J. Phys. Chem. Solids 39, 1235-1242 (1978).

Key words: alloys; electronegativity; electronic configuration; s-p binding; structural stability.

A new electronegativity scale is derived, in the spirit of Mulliken's original scheme, in terms of neutral atom spectroscopic data. The effect of changing the atomic configuration for C from covalent (sp3) to metallic (sp2) is considered. Structural stability maps are presented for non-octet non-transition metal compounds, and for two classes of transition metal-non-transition-metal compounds.

18384. Anderson, W. E., Davis, R. S., Dissipation factor measurements on dielectric materials at liquid helium temperatures, Proc. Conf. on Electrical Insulation and Dielectric Phenomena, Gaithersburg, MD, Nov. 3-6, 1975, pp. 151-156 (National Academy of Sciences, Washington, DC, 1978).

Key words: cryogenic; dielectric loss; dissipation factor; high voltage; low temperature polymer.

The designers of high voltage superconducting a.c. cables need accurate dissipation factor measurements of proposed insulating materials. A technique for making these measurements at high voltage using a current comparator bridge is described. Dissipation factor data at 60 Hz and 4.2 K is presented for several polymers. The estimated uncertainty in the dissipation factor is 5 × 10.

18385. Chi, J., Kelly, G. E., A method for estimating the seasonal performance of residential gas and oil-fired heating systems, ASHRAE Trans. 84, Part 1, 405-420 (1978).

Key words: boiler; combustion; energy; furnace; gas-fired; heating; oil-fired; rating; space-heating; testing.

An evaluation procedure is described for estimating the seasonal efficiency of a gas or oil-fired furnace which is located in an indoor heated space and uses conditioned air for combustion and draft control. It involves carrying out the following four tasks: 1) measuring the flue gas temperature and CO2 concentration during steady-state operation; 2) obtaining information on the shape of the flue gas temperature-vs-time curves as a unit cools-down and warms-up from steady-state conditions; 3) assigning appropriate values to various factors which describe the off-period air flow rate through the flue and stack, the degree of furnace oversizing, and the effect of furnace operation on infiltration, and 4) carrying out the calculation procedure described herein to determine the various on-period and off-period losses and the seasonal efficiency of a furnace or boiler operating in any given climatic region. Several examples are worked out to illustrate the nature of this simplified procedure.

18386. Unassigned.

18387. Goldman, D. T., Managing research, Phys. Today, Letter to the Editor 32, No. 1, 94-95 (Jan. 1979).

Key words: management; research.

18388. Horwitz, A. B., Leone, S. R., Laser-excited resonant isotopic V→ V energy transfer: HCl-H37Cl, H”Br-H31Br, DCI-D3Cl, and D"Br-Da1Br, J. Chem. Phys. 69, No. 12, 5319-5328 (Dec. 15, 1978).

Key words: hydrogen halides; isotopes; laser; vibrational energy transfer.

=

=

An isotopically selective transverse discharge chemical laser coupled with infrared fluorescence techniques is used to measure vibration-to-vibration energy transfer rates between v = 1 levels of the isotopic species HCl H3⁄4Cl, H"Br← Ha1Br, DCI ↔ D3Cl, and D"Br← D'Br. The measured rate constants are kncı = (1.91 ± 0.04) × 10−", kнBr (1.50 ± 0.06) × 10-", kpct = (1.18 ± 0.08) × 10-", and kDBY (8.34 ± 0.17) X 10-12 cm3 molecule-1 sec-1. All of the processes are nearly resonant and the rates for the hydrogenated species are on the order of one-tenth gas-kinetic. The rates for DCI and DBr are found to be 1.6 and 1.8 times slower than the corresponding hydrogen halides. Direct comparison of the results with theoretical predictions for such resonant energy transfer processes shows disagreement, indicating that further development of theoretical methods for these systems is desirable.

18389. McCann, K. J., Flannery, M. R., Elastic scattering and rotational excitation in ion-molecule collisions. II. Li*-H, and H⭑-H2 collisions, J. Chem. Phys. 69, No. 12, 5275-5287 (Dec. 15, 1978).

Key words: ion-molecule collisions; rotational excitation; semiclassical treatment.

A general semiclassical treatment of elastic scattering and of rotational excitation in ion-molecule collisions is presented. When the orbits associated with the different channels corresponding to the internal modes do not differ significantly, simplification occurs and the internal degrees of freedom can then be coupled to the relative motion via the introduction of an optical potential (which in turn depends on the transition amplitudes). Total energy is consequently conserved. An expression is derived for the inelastic scattering amplitude which acknowledges various interference effects and possible rainbow scattering. With all phase-information supressed, the procedure, when compared with the full quantum-mechanical results, reproduces the background elastic and inelastic scattering in Li*-H, and in H+-H, collisions. Restoration of the phases, particularly of the eikonal or action phases associated with the different classical paths that contribute to a specified scattering angle, produces the interference oscillations present in the differential cross section for scattering angles less than the rainbow angle. The method, when compared with the full quantal procedure, is remarkably efficient and accurate.

18390. Unassigned.

18391. Sachse, W., Golan, S., The scattering of elastic pulses and the non-destructive evaluation of materials, Proc. American Society of Mechanical Engineers Winter Annual Meeting, San Francisco, CA, Dec. 10-15, 1978, pp. 11-31 (American Society of Mechanical Engineers, New York, NY, 1979).

Key words: acoustic; crack; defects; elastic solid; pulses; scattering; ultrasonic.

This paper is a review of the results of experiments and their interpretation of the scattering of bulk ultrasonic pulses from various smooth and crack-like obstacles imbedded in an elastic solid. The scattering by circular and elliptical cylinders and multiple inclusions possessing a wide range of acoustic properties and crack-like defects of various sizes and orientations is described. For the smooth obstacles, it is shown that both arrival-time and spectral analysis of the scattered signals contain information regarding the characteristics of the scatterer and either can be used to characterize such obstacles. For the crack-like scatterers, the time-delays of various signals scattered by the crack are measured relative to reference signals from the specimen surfaces from which the crack size can be ascertained.

18392. Celotta, R. J., Swanson, N., Kurepa, M., Electron scattering from ozone, Proc. Int. Conf. on the Physics of Electronic and Atomic Collisions, Paris, France, July 21-27, 1977, pp. 656-657 (Commissariat a L'Energie Atomique, Paris, France, 1978).

Key words: electron scattering; energy loss; excited states; negative ions; ozone; resonances.

We present recent electron scattering measurements in ozone which (1) resolve vibrational structure in the energy loss range of 1.3-2.4 eV and (2) exhibit resonances in the incident energy range of 0.9-1.9 eV.

18393. Hanson, D. W., Davis, D. D., Cateora, J. V., Microprocessor-based satellite-controlled clock, Proc. of the NBS-IEEE Microcomputer-Based Instrumentation Conf., Gaithersburg, MD, June 12-13, 1978, pp. 83-86 (Institute of Electrical and Electronics Engineers, Silver Spring, MD, 1978).

Key words: clock; GOES; microprocessors; satellite; synchronization; time.

As a demonstration of the usefulness of the NBS-sponsored time signals from two U.S. weather satellites, NBS designed and

« PreviousContinue »