C. L. Carroll, 36 pages (Aug. 1975). Order from NTIS as PB247943.

Key words: density standard; phase shift; silicon.

There were a few features of our recently completed density standard experiment which were based upon ideas which, we believe, should be changed. This report lists these changes and their justification. The result is to increase the assumed values of the densities of the crystals by about 1.7 ppm. The new assumed values are: X2= 2.329 1289 g/cm3; X3 = 2.329 1253 g/cm3; X4 = 2.329 1228 g/cm3; X5 = 2.329 1226 g/cm3.

=

Additionally, we now believe that the densities of the crystals are stable, and not appreciably changing due to oxidation-a point left unresolved in our published report.

NBSIR 75-769. Report on an NBS/AID/OAS Workshop on standardization and measurement services in industrializing economies, H. S. Peiser, R. S. Marvin, M. McNeil, and J. Mejeur, Eds., 227 pages (Sept. 1975). Order from NTIS as PB247978. Key words: AID; assistance; economics; foreign relations; industrializing nations; LDC's; measurement services; OAS; standardization.

On November 3-16, 1974, a Workshop was held at the National Bureau of Standards, Gaithersburg, under the sponsorship of AID and the Organization of American States, the object of which was to give standards officials of industrializing nations insight into the standards and measurement systems in the United States and the role of the National Bureau of Standards, so that these officials might consider what parts of the U.S. system might usefully be adapted to conditions in their home countries. The report contains copies of speeches and presentations by the U.S. hosts and the participants from the other nations. In addition, information is given on the general agenda of discussions, presentations, and tours of laboratories at NBS and other U.S. organizations.

NBSIR 75-770. The equation of state for ammonia, L. Haar and J. Gallagher, 27 pages (Sept. 1975). Order from NTIS as COM 75-11370.

Key words: ammonia; correlation; gas; liquid; thermodynamic properties; thermodynamic surface.

An outline is presented of the basic results of the extensive correlation for the thermodynamic properties of ammonia recently completed at this laboratory. Computer programs are presented for the calculation of thermodynamic properties in the range including the triple point temperature to 5/3 the critical temperature and pressures from the dilute gas to 8000 bar.

NBSIR 75-772. The dynamic response of helicoid anemometers, J. M. McMichael and P. S. Klebanoff, 54 pages (Nov. 1975). Order from NTIS as PB246861.

Key words: air; analytical; anemometer; dynamic response; experimental; lag; unsteady flow.

The results of an analytical and experimental investigation of the dynamic response of a helicoid anemometer are presented. The experimental investigation was conducted using the NBS Unsteady Flow Facility and data are presented which illustrate the dynamic behavior in a spatially uniform, fluctuating flow with varying amplitudes, frequencies, and mean velocities. An analytical model governing the dynamic response is also presented and compared with the experimental results.

NBSIR 75-774. Calibration of Kerr systems used to measure high voltage pulses, R. E. Hebner, Jr., 51 pages (Aug. 7, 1975). Order from NTIS as COM 75-11364.

Key words: automated measurements; dielectrics; dividers; electrical measurement; electric fields; electro-optics; high voltage measurements; insulating fluids; Kerr effect; nitrobenzene; pulse measurements; space charge.

The purpose of this work is to define, develop and refine techniques for calibrating pulse voltage measurement systems, particularly those based on the electro-optic Kerr effect. The approach used exploits the assumed frequency independence of the Kerr coefficient of nitrobenzene. Theoretically, the Kerr coefficient should exhibit the same frequency dependence as the relative permittivity. Measurements have shown the relative permittivity to be approximately frequency independent over the frequency range from direct voltage to 109 Hz. The realization of this calibration approach has been hampered by the fact that the electric field distribution, in the liquid exhibiting the electro-optic Kerr effect, is itself frequency dependent.

This report describes the present best comparison of cell calibration under direct voltage with calibration under low frequency alternating voltage and calibration under pulsed high voltage. The results under all three types of waveforms agree to within ±0.5 percent. From these results it can be inferred that it is feasible to use an electro-optic Kerr system as an independent, and possibly more accurate, device against which to calibrate other pulse voltage measurement systems.

In addition to this discussion of Kerr system calibration, the report contains two appendices. One presents an improved technique for analysis of data obtained from a Kerr system and the other discusses space charge in a nitrobenzene-filled Kerr cell.

NBSIR 75-775. Electrical measurement of high voltage pulses in diagnostic x-ray units, R. E. Hebner, Jr., 62 pages (Nov. 1, 1975). Order from NTIS as PB248684.

Key words: calibration; electrical measurements; electrooptics; frequency response; high voltage; Kerr effect; operational amplifier; pulses; radiation; safety; x-ray generators;

x rays.

The report describes a method of calibrating dividers used to measure high voltage pulses in diagnostic x-ray units. The experimental development emphasized four areas. These were the divider ratio under direct voltage, the frequency dependence of the ratio, the voltage dependence of the ratio and the effect of self-heating on the device. The results of measurements on approximately fifteen different dividers are summarized.

In addition, this report contains two appendices. The first discusses conventional and electro-optical methods of measuring the high voltage pulses, while the second presents a more detailed analysis of the feasibility of electro-optical measurement of these pulses.

NBSIR 75-778. ETIP: THE FIRST 18 MONTHS. A progress report of the experimental technology incentives program, National Bureau of Standards, J. D. Lewis, 74 pages (Aug. 1975). Order from NTIS as PB246435.

Key words: civilian R&D policy; ETIP; incentives; innovation; procurement policy; regulatory policy; small business policy; technology.

This internally prepared report describes the overall accomplishments of the experimental Technology Incentives Program in carrying out its mission. Progress is compared with the plans that were established in a program plan approved by the Secretary of Commerce in February of 1974. An appendix to the report describes the purpose and shows progress of each of the individual projects that ETIP has launched.

NBSIR 75-779. The development of an improved compression

test method for wall panels, C. W. C. Yancey and L. E. Cattaneo, 107 pages (Dec. 1975). Order from NTIS as PB249935.

Key words: compression; eccentric loading; flat-end; kern; loading rate; pin-end; test method; wall panels; walls.

An experimental and analytical investigation of the primary factors involved in the testing of prototype wall panels under axial compression loading is reported. The objective of the investigation was to develop a method of testing wall specimens that incorporates the best features of ASTM Standard Method E72 while at the same time incorporating improvements in the areas of deficiency in the Standard. Twenty-five laboratory tests were conducted on samples composed of five types of wall panel construction. The panels were tested to failure under either of two different eccentricities of load, while being supported with one of two types of idealized end conditions. Selected test results and detailed descriptions of the laboratory procedures used are presented. A computer-aided analytical study of the variables affecting the degree of uniformity of loading was conducted. Equations based on the analogy of beams supported on elastic foundations were used in the analysis. A study of the statistical parameters commonly used to interpret test results was conducted to establish useful guidelines for predicting structural performance on the basis of small sample test results. A compression test method applicable to traditional and innovative wall constructions is presented. The principal additions in the revised test method are as follows: (a) a provision for variable eccentricity, (b) a procedure for selecting a load distribution assembly which will be compatible with the test panel.

NBSIR 75-781. Optical materials characterization, A. Feldman, D. Horowitz, R. M. Waxler, I. H. Malitson, and M. J. Dodge, 24 pages (Aug. 1975). Order from NTIS as COM 75-11375.

Key words: birefringence; elastic constants; infrared-laser window materials; interferometry; KCl; photoelasticity; polycrystalline ZnSe; refractive index; stress-optical constants; thermal coefficient of refractive index; ZnSe.

The refractive index of each of two prismatic samples of chemical vapor deposited (CVD) ZnSe was measured from 0.5086 μm to 18.2 μm by means of the minimum-deviation method on a precision spectrometer. Data were obtained at temperatures near 20 and 34 °C and each set of data was fitted to a three-term Sellmeier-type dispersion equation, which permits refractive index interpolation within several parts in 10-5. From the data obtained at the two temperatures, dn/dT was calculated for both samples. A comparison of refractive index and dn/dT is made with other types of ZnSe. Preliminary photoelastic data are presented for single crystal specimens of Ge, reactive atmosphere processed (RAP) KCl, and KCl doped with KI. The Ge data, which were obtained at 10.6 μm differ from previously reported data. Data on the two types of KCl were obtained at 10.6 μm, 0.633 μm and 0.644 μm. These data are compared with values from the literature. Also presented are revised photoelasticity data for CVD ZnSe. The design of an improved stressing apparatus that was developed for the measurement of photoelastic constants is discussed.

NBSIR 75-782. Full-scale corridor fire experiment using a glass fiber carpet, L. H. Breden, 33 pages (Dec. 1975). Order from NTIS as PB248643.

Key words: carpet; corridor test; fire testing; flammability; glass fiber.

A corridor fire experiment was carried out using a glass fiber carpet. It was observed that with a fuel loading of 2.7 pounds per square foot of wood in an adjacent fire room, no propagation of

the fire occurred down the corridor. The glass fiber carpet in the burn-room became discolored and there was a significant weight loss of the carpet directly in contact with the fire. The carpet did not produce significant levels of smoke and did not spread the fire into the corridor.

NBSIR 75-783. Validation of the DELCAP airport simulation model, J. F. Gilsinn, 167 pages (July 1975). Available from the author at the National Bureau of Standards, Washington, D.C. 20234.

Key words: airport; airport capacity; airport simulation; models; model validation; runway capacity; simulation; validation.

This report documents exercises of the DELCAP airport simulation model performed to validate the outputs of that model. Airport throughput levels were calculated by DELCAP for five runway configurations, with three or four appropriate operating policies chosen for each, and for three different mixes of aircraft types. These estimates from DELCAP agreed well, generally within 6 to 8 percent, with current values provided by the FAA. An attempt at validating DELCAP's delay-figure output, using existing data on scheduled and actual times of aircraft departures and arrivals, is also reported. It proved unsuccessful, because available data are not sufficient to isolate that portion of total delay which DELCAP is designed to measure, i.e., terminal area ATC delay. A collection effort to accumulate the necessary data is formulated. Appendices to the report contain program listing, flowcharts, descriptions of program changes from earlier versions, and user instructions for the model's operation.

NBSIR 75-784. Fire incidents involving flammable liquids, gas, and dry explosives, E. A. Tyrrell, 58 pages (Oct. 1975). Order from NTIS as PB246862.

Key words: accidents; burn injuries; burn severity; explosives; fabric fires; FFACTS; flammable liquids; gas; gasoline; ignition-causing activities; ignition sources; injury disposition.

From the NBS Flammable Fabrics Accident Case and Testing System as of December 1973, flammable liquids, gas, and dry explosives were found to be involved in 832 incidents, injuring 863 victims. Volatile flammable liquids represented 77 percent of the incidents; 72 percent of these liquids were gasoline. Male victims outnumbered females more than 3 to 1. Young adults, ages 21-45, and youth, ages 13-20, were injured most frequently. Children and youth were injured primarily through what was considered as play activities. Adults generally were injured while engaged in activities traditionally considered as being oriented to the particular sex involved. Streetwear, particularly shirts/blouses, was reported most frequently as igniting first. Thirty-six percent of the fabrics represented in these incidents were contaminated with a flammable liquid. Most of the victims sustained burn injuries covering 1-10 percent of their bodies; only 6 percent sustained burn injuries covering 61 percent or more of their bodies. Most of the victims were hospitalized for treatment of their injuries. Although the very young and the elderly were involved in these incidents less frequently than other age groups, they generally were burned more severely and represented 46 percent of the victims who died in the hospital or were dead on arrival.

NBSIR 75-785. The review of standardization and measurement services at the Ecuadorian Institute for Standardization, R. Estrada and H. S. Peiser, 17 pages (June 27-29, 1974). Order from NTIS as PB246345.

Key words: AID; development assistance; economics; Ecuador; less developed countries; measurement services; review; standardization; survey.

An international team of standards and measurement specialists visited the Ecuadorian Institute for Standardization on June 27-29, 1974, to review the operations of that organization in light of the recommendations made two years earlier by a Survey of Standardization and Measurement Services in Ecuador conducted by a team which was organized and sponsored by the U.S. National Bureau of Standards and the U.S. Agency for International Development. The review consists of the historical background of the Institute, results of the 1972 Survey, and recommendations for future planning.

NBSIR 75-786. The CPSC road test of bicycle braking performance-Kinetic and error analyses, L. Mordfin, 75 pages (Oct. 1975). Order from NTIS as PB251411.

Key words: bicycle brakes; brakes, bicycle; dynamics, bicycle; error analysis; friction, tire/pavement; kinetics, bicycle; measurements, bicycle braking; pitchover; standards, bicycle safety; test method, bicycle.

The Consumer Product Safety Commission has promulgated a safety standard for bicycle braking systems based on the stopping distances achieved in road tests under specified conditions. This report presents an error analysis of the test method, for the Commission's use in justifying or modifying the test criteria. The error analysis is based on experimental data, for the most part, and on theoretical principles where sufficient data are lacking. The theory, a kinetic analysis of the bicycle braking process, is included in the report together with proposed definitions of terms intended to quantify important aspects of bicycle braking performance.

The error analysis produced estimates of rather large lab-tolab and test-to-test variabilities to be expected from the test method. These, in turn, were found to be principally dominated by errors resulting from an incorrect overweight-rider allowance specified by the Commission, and by variations in rider reaction times, respectively. Suggestions are made for more accurate methods of accommodating variations in rider mass, for reducing the effects of the test-to-test variability, and for reducing the danger of pitchover in the performance of the road test.

NBSIR 75-787. Piezo- and pyroelectric properties of electrets, M. G. Broadhurst and G. T. Davis, 55 pages (Oct. 1975). Order from NTIS as COM 75-11471.

Key words: electrets; piezoelectricity; polarization; polymers; polyvinylchloride; polyvinylfluoride;

polyvinylidenefluoride.

A model for piezo- and pyroelectricity in polymers is presented. These effects are true piezo- and pyroelectricity rather than electrostriction, conduction, electromechanical effects or the motion of conductors in the field of space charges. Two distinct types of polymers can be piezoelectric. Amorphous polymers are piezo- and pyroelectric by virtue of a nonequilibrium but kinetically stable net dipole orientation. The semicrystalline polymers are piezoelectric due to alignment of polar, ferroelectric crystals dispersed in the amorphous phase. In both types the magnitudes of the piezo- and pyroelectric effects are in accord with the expected temperature and pressure dependence of the dipolar polarization. Space charges embedded in the polymer normally will not produce a piezo- or pyroelectric current. Those embedded near the crystal-liquid interfaces tend to reduce the piezo- and pyroelectricity. Improved orientation of dipoles and reduction of ionic impurities should increase p and d for PVF2 by a factor of three above typical values presently reported. The sensitivity of amorphous polymers is limited mainly by dipole moment per unit volume and breakdown strength.

NBSIR 75-788. Evaluation of the fire hazard in a mobile home resulting from an ignition on the kitchen range, E. K. Budnick and D. P. Klein, 28 pages (Feb. 1976). Order from NTIS as DB250843.

Key words: fire test; flame spread; kitchen cabinets; kitchen range; kitchen range hood; limited combustibility; mobile home.

A series of fire tests was conducted in a typical mobile home to evaluate the potential fire hazard resulting from an accidental ignition from cooking on the kitchen range. Specific attention was directed to (a) ease of ignition of the kitchen cabinets as a function of the clearance between the range and the underside of the cabinets with and without the presence of a metal hood and (b) flame spread following the ignition.

The tests, which used a preheated pan of cooking oil as an ignition source, were conducted in a mobile home kitchen area. The materials tested were printed lauan plywood, printed particle board, and molded polystyrene, representative of materials used in kitchen cabinet construction in mobile homes.

Under the test conditions employed, it was found that ignition of the kitchen cabinets occurred in all cases in which a metal hood was not used. The time to ignition of the materials was only slightly affected by the clearance between the specimen (cabinet bottom) and the range. A significant time delay or no ignition resulted from the installation of a metal range hood.

An additional problem area revealed by the tests was the ignition and burn-through of the partition directly behind the range. Specific design recommendations based on test results are presented along with suggestions for further investigation.

NBSIR 75-790. FY75 progress report on design criteria and methodology for construction of low-rise buildings to better resist typhoons and hurricanes, R. D. Marshall and N. J. Raufaste, Jr., 362 pages (Nov. 1975). Order from NTIS as PB250848.

Key words: buildings; codes and standards; housing; hurricanes; low-rise buildings; natural disaster; structural connections; typhoons; wind loads.

This report represents the major accomplishments conducted during the third phase (FY75) of a three year project to develop improved design criteria for low-rise buildings in developing countries to better resist extreme winds. The research study sponsored by the Agency for International Development commenced in March 1973. Two other reports were prepared: NBSIR 74-582 FY73 Progress Report (first phase of the research-4 months) and NBSIR 74-567 FY74 Progress Report (second phase of the research-12 months). During FY75, 6 major tasks were completed (instrumentation of fifth and sixth of six test houses to collect full scale field wind data, continuation of technician training at the field sites and at the wind tunnel facility, analyzed of extreme wind data, development of draft improved design criteria reports, participation in regional conferences in Manila and scheduling of regional dissemination of project results conference in Jamaica for November 1975). Research activities will be completed in December 1975. A final report will be published by the end of FY76.

NBSIR 75-791. Procedural options for modification of architectural glass in residences to improve occupant safety, S. W. Stiefel, 57 pages (Dec. 1975). Order from NTIS as PB253229.

Key words: architectural glass products; Consumer Product Safety Act; residence-related products; residential safety modification; safety implementation approaches.

The U.S. Consumer Product Safety Commission has the responsibility for developing and promulgating mandatory safety standards for products which pose unreasonable risks of injury for consumers. One of the first products selected for development of a safety standard under the Consumer Product Safety Act of 1972 was architectural glass. The prospects for regulation of many other residential unit component parts are wide open. Nevertheless, the initial impact of the adoption of a mandatory standard for architectural glass would be rather limited. The limited impact is largely due to the fact that people will continue to occupy existing housing that will not be immediately subject to the new rule.

This report documents the second and final phase of a project which considered the possible modifications for architectural glass products and the means for encouraging their implementation. The report evaluates available injury data, defines the population of hazardous architectural glass products and compares the relative level of hazard among the products. A set of possible retrofit options is presented, suggested by accident pattern review, and criteria are developed, which are useful in assessing their effectiveness. A model has been developed and exercised to calculate benefit-cost ratios for retrofit modification based upon averted injury medical costs attributable to injuries prevented by product modification. A set of implementation approaches has been postulated for consideration by the CPSC, for encouraging safety modification of component parts of residential units.

NBSIR 75-793. Microsecond-resolution pulse calorimetry for semiconducting materials at high temperatures (a feasibility study), A. Cezairliyan and C. W. Beckett, 51 pages (Oct. 1975). Order from NTIS as PB247538.

Key words: capacitor discharges; heat capacity; high-speed measurements; high temperature; thermodynamics; uranium dioxide.

A feasibility study is conducted for the applicability of microsecond-resolution pulse heating techniques to the measurement of selected thermodynamic properties of semiconducting substances at high temperatures. The method of pulse heating of the specimen using capacitor discharges is described and general design considerations, including electrical circuitry and various physical, electrical and chemical phenomena, are presented. Measurements of experimental quantities, such as current, voltage, temperature, and pressure are described. The special problems in relation to measurements of heat capacity and vapor pressure of uranium dioxide in the temperature range 2000 to 6000 K are discussed. It is concluded that the capacitor discharge circuitry and the measurement of the experimental quantities, although difficult, are not likely to present major problems. However, problems are likely to stem from the experiment chamber and the specimen. The nature of these problems is discussed, and the performance of some preliminary experiments is suggested.

NBSIR 75-794. Heat transfer in furnaces for CIB cooperative program and heat balance analysis of wall furnace, J. B. Fang and J. T. Scott, 48 pages (Nov. 1975). Order from NTIS as PB247203.

Key words: fire resistance ratings; fire test furnace; heat balance; heat transfer; temperature-time curve.

Tests were conducted in the NBS wall panel furnace as part of a CIB international cooperative program to measure and compare heat transfer in fire endurance furnaces. Additionally, a heat

balance analysis showed that a cellular concrete block wall specimen absorbed more heat by convection than by radiation. The rate of radiant heat transfer was found to decrease slowly, while the furnace exhaust heat loss increased during the test from 42 to 58 percent of the heat output. The calculated radiant heat fluxes incident at furnace walls was found to be somewhat lower than the experimental values measured at the test wall. NBSIR 75-795. Recommended criteria for retrofit materials and products eligible for tax credit, W. J. Rossiter, Jr. and R. G. Mathey, Eds., 44 pages (Nov. 1975). Order from NTIS as PB246866.

Key words: caulks and sealants; clock thermostats; energy conservation; insulation; retrofitting; storm doors; storm windows; tax credit; vapor barriers; weatherstripping.

The Federal Energy Administration requested the National Bureau of Standards to develop criteria for retrofitting for possible use by the Internal Revenue Service in implementing the Presidential initiative authorizing tax credit to homeowners. Criteria are recommended for materials and products considered eligible for proposed tax credit for retrofitting one and two family residences to conserve energy. The materials considered include insulation and vapor barriers, storm windows and doors, caulking and weatherstripping, and clock thermostats. A list of these retrofit materials was compiled by generic type and recommendations made on their installation.

In addition to recommended criteria for materials and products eligible for tax credit, desired levels of performance for the retrofit materials are presented as a guide to homeowners to achieve maximum benefits in energy conservation through retrofitting.

NBSIR 75-796. An analysis of the Salmon Statistical Information System, F. C. Johnson, 20 pages (Sept. 29, 1975). Order from NTIS as PB247656.

Key words: Anadromous Fish Catch Record System; catch record system; fisheries statistics; fish record system; fishery management model; fishery modeling; modeling; salmon; salmon fishery; salmon information system; Washington State Fisheries.

This report contains an analysis of the official salmon statistical information system of the Washington State Department of Fisheries relative to the changing data requirements of the Department. Recommendations are given for revising the current system in order to assure the availability of complete, accurate statistics on a timely basis. In addition, the principal requirements are identified for the development of improved procedures for generating input to the hatchery and fishery management models in use by the Department. This project was sponsored by the Washington State Department of Fisheries under Service Contract No. 626.

NBSIR 75-797. An evaluation of a range-top warning light system, M. E. Stefl and J. J. Persensky, 22 pages (July 1975). Order from NTIS as COM 75-11465.

Key words: consumer products; human factors; kitchen; ranges; reaction time; safety; warning lights.

A descriptive analysis of In-Depth Injury Investigations of range-related accidents revealed a series of incidents where range-users were unaware that surface elements were energized. One proposed solution to this problem involved a system of four warning lights to indicate individual surface unit activation. A laboratory study using human subjects evaluated the effectiveness of such a system. The backgrounds against which the warning lights were fitted and the intensity of the lights were not shown to influence subjects' responses in a reaction time task; however, the position of the lights and the type of ancilliary task

being performed by the subject did. These results are discussed in terms of product design and safety, and implications of the study for methodological development are considered.

NBSIR 75-801. A bibliography on automated measurements (July 1, 1969, to July 1, 1974), G. A. Teamer and A. Y. Rumfelt, 158 pages (Apr. 1976). Order from NTIS as PB252044. Key words: automated measurements; computer-aided measurements; computer-controlled instruments.

This bibliography lists approximately 1000 citations pertinent to the field of automated measurement of electrical/electronic quantities and characteristics. In addition, approximately 400 citations are included that should be helpful in applying computers to the automation of measurements. Only references appearing in the open literature between July 1, 1969, and July 1, 1974, are listed.

NBSIR 75-804. Generation of standard EM fields for calibration of power density meters 20 kHz to 1000 MHz, M. L. Crawford, 44 pages (Jan. 1975). Order from NTIS as COM 75-10395.

Key words: hazard level fields; power density meter calibration; TEM transmission cells.

This report describes techniques for calibrating power density meters used by the Department of Defense in measuring high intensity (hazard level) RF fields in the frequency range 20 kHz to 1000 MHz. It reports on part of the work sponsored by the Calibration Coordination Group (CCG), of the Department of Defense covering the frequency range 20 kHz to 20 GHz.

Several techniques were considered for producing a standard field including parallel plate and parallel wire transmission lines, transverse electromagnetic mode (TEM) transmission cells, various directive antennas and open ended waveguide (OEG). The major emphasis in this report is on the TEM cells, which are recommended for the frequency range 20 kHz to 500 MHz. Design and evaluation details and an error analysis associated with the TEM cell measurement system are given. Power density levels can be established in the cells from a few μW/cm2 to 100 mW/cm2 with uncertainties less than ± dB.

Limited information is also given describing the use of OEG, the recommended technique for the frequency range 500 MHz to 2.6 GHz, and giving the results of intercomparisons among parallel plate lines, TEM cells, OEG, and standard gain horns.

NBSIR 75-805. Calibration techniques for electromagnetic hazard meters: 500 MHz to 20 GHz, R. R. Bowman, 38 pages (Apr. 1976). Order from NTIS as PB252971.

Key words: calibrations; electromagnetic hazards; field meters; gain; microwave; near-field.

The calibration techniques discussed are suitable for producing fields for calibrating most electromagnetic (EM) hazard meters to within ±1.0 dB using a minimum of laboratory space and oscillator power. Above about 2.6 GHz, adequate equipment and standards have been available for these calibrations. Below this frequency the large apertures of the usual horn radiators require more power than is available from medium power oscillators. Further, calibrations in closed systems are difficult except at frequencies well below 1 GHz. Thus there is a need for smallaperture gain standards from about 500 MHz to 2.6 GHz. The main portion of the work reported here consists of accurate gain measurements for open-ended hollow waveguide radiators (OEG) for use from 500 MHz to 2.6 GHz. Other characteristics of this type of radiator important for EM hazard meter calibrations were also determined: near-field corrections, reflection coefficients, and aperture scattering. The suitability of the calibration scheme was tested by performing calibrations at 2

GHz on an EM hazard meter with both a horn radiator and an OEG radiator.

NBSIR 75-806. Phase equilibrium and flow-induced desorption data for He-CO, He-N2O, and He-N2 systems, W. G. Steward, R. O. Voth, J. Hord, W. R. Parrish, C. F. Sindt, and J. M. Arvidson, 62 pages (Mar. 1975). Order from NTIS as COM 7510368.

Key words: binary mixture; cavitating venturi; enhancement factors; experimental vapor-liquid equilibria; flow induced desorption; helium-carbon monoxide system; heliumnitrous oxide system; Henry's law constants; two phase choking; two phase flow.

Liquid-vapor equilibrium data were obtained for the heliumcarbon monoxide and helium-nitrous oxide systems at pressures to 138 bars. Liquid and vapor phase compositions were measured at nominal temperatures of 80, 85, 90, 100, and 120 K (144, 153, 162, 180, and 216 °R) for the helium-carbon monoxide system, and at 235, 245, 265, and 285 K (423, 441, 477, and 513 °R) for the helium-nitrous oxide system. Internal consistency of the data was checked by using pseudo-Henry's law constants and enhancement factors.

The effects on flow of helium absorption and subsequent flowinduced desorption were investigated by means of reduced scale model experiments. Friction losses attributable to helium desorption in the long channels proved to be negligible both in experimental measurements and in calculations based on assumed equilibrium of liquid and gas. Contrarily, the assumption of phase equilibrium leads to gross miscalculations of flow rates in cavitating or near cavitating nozzles or venturis. Actual venturi mass flow rates reached in the experiments were fifty times the theoretical choking flow rates; however, definite mass flow rate reductions due to helium desorption were measured, ranging from four percent for nitrogen to twelve percent for nitrous oxide. Pertinent experiences in handling these fluids and operating the test equipment are also discussed.

NBSIR 75-807. Turbulent natural convection of liquid deuterium, hydrogen, and nitrogen within enclosed vessels, D. E. Daney, 82 pages (Feb. 1975). Order from NTIS as COM 7510396.

Key words: cryogenic; heat transfer; hemisphere; horizontal cylinder; liquid deuterium, liquid hydrogen, liquid nitrogen; natural convection; sphere; vertical cylinder. Quasi-steady natural convection of liquid deuterium, hydrogen, and nitrogen within a sphere, hemisphere, horizontal cylinder, and vertical cylinder has been studied experimentally for the case of a nearly isothermal wall. A single expression relating the Nusselt and Rayleigh numbers,

Nu 0.104 Ra0.352,

fits the deuterium and nitrogen data over the range 7 × 108 < Ra <6 × 10", while the hydrogen Nusselt numbers are 8 percent lower. The temperature field within the vessels is virtually free of horizontal temperature gradients. A single dimensionless temperature profile characterizes the vertical temperature distribution for each vessel shape, with the profiles for the sphere, hemisphere, and horizontal cylinder being nearly identical.

NBSIR 75-809. Non-planar near-field measurements: Spherical scanning, P. F. Wacker, 67 pages (June 1975). Order from NTIS as COM 75-10989.

Key words: antennas; arrays; coordinate transformations; data processing; group representations; measurements; near field; non-planar; patterns; scanning; spherical; symmetry.