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Surface soil contamination due to oil spill is one of the major environmental concerns. The extent of the contaminated depth governs the design and installation of remediation method and monitoring system. Physical modeling of oil contaminant in unsaturated soils was conducted using a centrifuge. Preliminary results on effects of clay content and temperature on the contaminant profile near the surface are presented. The experimental results indicate that centrifuge modeling may be a viable method to study the problem of immiscible oil movement in partially water-saturated soils. DOI: 10.1061/(ASCE)0733-9372(2005)131:10(1473) CE Database subject headings: Centrifuge model Oil spills; Unsaturated flow; Cold regions; Contaminants; Temperature.

Recent physical model studies have refined designs for high-flow air diffusers for managing accumulations of broken ice at navigation projects. Although these solutions are successful in the model, implementing them in the field can be difficult because of uncertainties in airflow scaling. This study uses field and laboratory data to test theoretical relationships between airflow from the diffuser and the resulting near-surface water velocity. In the experiments, water velocities were measured adjacent to bubbler plumes for depths ranging from 0.52 to 6.5 m and airflow rates ranging from 0.015 to 0.68 standard cubic meters per minute/meter. The observed vertical and horizontal water velocity data compared moderately well to theoretical curves based on the equations of Kobus and Ashton. In addition, a reasonably linear relationship was found between the average velocity of the horizontal, near-surface flow field V and unit airflow from the diffuser [Q.sub.a] CE Database subject headings: Validation; Bubbles; Diffusion; Velocity; Air flow.

This paper describes a study undertaken at Umiujaq, in northern Quebec, on laterally loaded piles in permafrost subject to a constant displacement rate. Test results of bending moments, shear load, soil reaction, and pile displacements demonstrate the complex nature of creep of frozen soils. FEM simulations show a good concurrence with field test results and confirm a clear distinction between stationary and nonstationary creep. CE Database subject headings: Lateral loads; Piles; Permafrost; Canada; Creep; Displacement.

The detection of random defects in the fabrication process is important as they contribute to the majority of the defects occurring while processing the chips. Test structures are developed to detect random defects, test chips are then realized in the process, and measurements carried out and the results are presented.

This paper presents guidelines for the deep reactive ion etching (DRIE) of silicon MEMS structures, employing S[F.sub.6]/[O.sub.2]-based high-density plasmas at cryogenic temperatures. Procedures of how to tune the equipment for optimal results with respect to etch rate and profile control are described. Profile control is a delicate balance between the respective etching and deposition rates of a Si[O.sub.x][F.sub.y] passivation layer on the sidewalls and bottom of an etched structure in relation to the silicon removal rate from unpassivated areas. Any parameter that affects the relative rates of these processes has an effect on profile control. The deposition of the Si[O.sub.x][F.sub.y] layer is mainly determined by the oxygen content in the S[F.sub.6] gas flow and the electrode temperature. Removal of the Si[O.sub.x][F.sub.y] layer is mainly determined by the kinetic energy (self-bias) of ions in the S[F.sub.6]/[O.sub.2] plasma. Diagrams for profile control are given as a function of parameter settings, employing the previously published 'black silicon method'. Parameter settings for high rate silicon bulk etching, and the etching of micro needles and micro moulds are discussed, which demonstrate the usefulness of the diagrams for optimal design of etched features. Furthermore it is demonstrated that in order to use the oxygen flow as a control parameter for cryogenic DRIE, it is necessary to avoid or at least restrict the presence of fused silica as a dome material, because this material may release oxygen due to corrosion during operation of the plasma source. When inert dome materials like alumina are used, etching recipes can be defined for a broad variety of microstructures in the cryogenic temperature regime. Recipes with relatively low oxygen content (1-10% of the total gas volume) and ions with low kinetic energy can now be applied to observe a low lateral etch rate beneath the mask, and a high selectivity (more than 500) of silicon etching with respect to polymers and oxide mask materials is obtained. Crystallographic preference etching of silicon is observed at low wafer temperature (-120[degrees]C). This effect is enhanced by increasing the process pressure above 10 mtorr or for low ion energies (below 20 eV). [720] Index Terms--Cryogenic etching, profile control, reactive ion etching (RIE).

The coherence length of reactively sputtered Nb[subscript 0.62]Ti[subscript 0.38]N thin films is reported to be 2.4 plus or minus 0.3 mm.

Microwave propagation characteristics of a high-temperature superconducting (HTS) microstrip transmission line is examined by means of numerical analysis.

The performance of broad-band low-noise low-dc-power-consumption cryogenic amplifiers have been studied in detail with emphasis on minimizing the power consumption and optimizing the amplifier performance at cryogenic temperature. A general approach is presented for the modeling and amplifier design, which helps in minimizing the power consumption and optimizing the performance of the amplifier. A noise temperature below 9 K and 22-dB gain was experimentally obtained in the frequency range of 4-8 GHz with a total power consumption of 4 mW with commercial GaAs transistors. Index Terms--Empirical large-signal models, FET, FET noise models, modeling, noise model extraction, noise parameter.

Vickers hardness characteristics of bulk superconductors are examined at cryogenic temperatures.

Surface spark-over voltages for various solid insulators are examined in liquid N[subscript 2] and liquid helium under ac, dc, and impulse voltages. Results are summarized and discussed.

Cryogenic refrigerators and associated refrigerant-distribution systems are described and discussed.

Ansaldo-CRIS, Napoli, Italy, is developing a cryocooler-assisted cryostat for a 4 T split-coil NbTi magnet, operated in a helium bath.

A superfluid cryostat for a 1GHz nuclear magnetic resonance (NMR) magnet has been developed. Test results are presented and discussed.

Cooling of superconducting power cables with counter-flow cooling by means of liquid nitrogen is investigated.

Cryogenic liquids are claimed to have a noteworthy impact on the concept of improved future power equipment. The low boiling temperature of liquid helium or liquid nitrogen offers the use of superconducting materials which eliminate ohmic losses in the conductors on the one hand. This yields a high overall current density in the equipment. On the other hand, the liquids seem to be interesting basic insulators with reasonable dielectric performance in the medium high voltage domain. The liquids are chemically inert, and no irreversible compound within the insulation system must be anticipated. Hazards such as fire risk in case of faults can be ruled out. Thermal aging of the insulation system can also be disregarded because no excess temperature must be taken into account during service, even in case of temporary overload operation. Dielectric aging due to partial discharges may be of little concern because the liquids can be easily fully reprocessed by vaporizing and recondensing in a closed cooling circuit; no memory effects then can degrade the liquid. Finally, the liquids are produced from gases which are found in open atmosphere. Thus, the disposal of insulation systems at the end of operational life is straightforward.

Application of conventional cutting fluids do not serve the purposes effectively particularly under high cutting velocity and feed. Besides, such cutting fluids pollute the environment in high production machining and grinding. Cryogenic cooling seemed to be quite effective in reducing the high cutting temperature which impairs product quality and reduces tool life. The present work deals with investigating the role of cryogenic cooling by liquid nitrogen jet on cutting temperature in turning plain carbon steel (C-40) under varying cutting velocity and feed. The experimental and computational results indicate that such cryogenic cooling enables substantial reduction in the cutting temperature depending upon the levels of the cutting velocity and feed and the cutting tool geometry. It was also noted that the chip formation and chip-tool interaction become more favorable and the cutting forces decreased to some extent when liquid nitrogen jet was employed. Therefore, it appears that cryogenic cooling, if properly employed, not only provides environment friendliness but can also improve the machinability characteristics. [DOI: 10.1115/1.1413774]

Two types of tunable filters have been developed at 400- and 800-MHz frequency bands, respectively. These filters have been fabricated with low-temperature co-fired-ceramics multilayer technologies assisted by varactor diodes. The filter size is 5.6 x 5.6 x 3.0 mm. Each filter has approximately 11% and 13% tuning range of frequency with a controlling voltage of 1-4 V, IL < 2.0 dB, and has an attenuation over 40 dB at fo [+ or -] 30%, respectively. Temperature stability data is also discussed. Index Terms--Ceramics, multilayers, tunable filters, varactors.

Helical coils for the Large Helical Device were studied to determine excitation properties and cryogenic stability.

The development of an optimized resistance bridge based on the Cryogenic Current Comparator with SQUID readout is discussed.

Research is presented describing measurement studies of a high-gradient quadrupole magnet that has been cooled with stagnant, pressurized, superfluid. The studies were conducted on a 2-m long superconducting model of the Large Hadron Collider interaction region quadrupole magnet at the European Organization for Nuclear Research (CERN).

Research is presented concerning the investigation of the processes involved in decreasing the gate sizes in the niobium Josephson IC fabrication process in order to increase packing density and speed.

The growth of low-temperature fully dense polycrystalline TiN layers having complete 111 texture characteristics has been accomplished. The technique, which used reactive magnetron sputter deposition, produces TiN films that were sightly overstoichiometric with a N/Ti ratio of 1.02 + or - 0.03. The increase of the onset temperature fr interfacial reaction to 610 degrees Celsius in bilayers with fully dense TiN led to the demonstration of complete 111 preferred orientation.

For a system of spheres multiply contacting in 180-degree orientation, transient temperature computation is discussed. The meaning of the driving potential for transient formulations is considered to develop a transient formulation that can compute temperature development of a packed-sphere system, but keep the spatial resolution to that for a sphere. A correction factor was shown to be necessary and is called constriction capacitance.

Theoretical and experimental characterizations were used to study the cryogenic interlaminar shear behavior of G-10CR glass-cloth/epoxy laminates. Measurements of the interlaminar shear strength of glass-cloth/epoxy laminates at low temperatures were done through the use of the double-notch shear test. The effect of specimen thickness and notch separation on the shear stress distribution in the expected fracture plane was investigated by means of a three-dimensional finite element analysis.

This paper is a reasoned conjecture of the future up to 2050 AD including estimates of energy supply and consumption, transport system developments and corresponding pollution effects. Results of the logistic substitution methods (Volterra-Lotka) are used in forecasting trends in innovation, transport and energy. Later work on normative forecasts is also included. The future of aeronautics cannot be isolated from events in other transport modes which together create the major problem of crude oil replacement during the next century. Natural gas will be the dominant energy source for the next 80 years and a major question is how best to use it for aviation. The work on which this paper is based was started in 1992 to answer the following questions: * Is the future oil shortfall sufficient to restrict aviation traffic and growth in the next 50 years? * If so, what is its substitute? * Can a substitute be obtained cheaply enough to free aviation from future kerosine shortages? * Is it paramount to change to liquid hydrogen fuel to avoid future fuel shortage in aeronautics, incidentally conferring possible environmental advantages? There was no adequate evidence available to answer these questions, hence a method was devised to bring together several sets of partial data that contributed to the solution. The essence is to use the mean annual growth rate of traffic or energy over a future period as a pseudo-independent variable. This allows the inclusion of alternative high and low estimates of all the important quantities involved.

Cryogenic fluid damper seals operating close to the liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two-phase flow region which affects the seal performance and reliability. An all-liquid, liquid-vapor, and all-vapor, i.e., a 'continuous vaporization' bulk flow model for prediction of the seal dynamic forced response is given in Part I. The numerical method of solution of the flow equations is detailed here. Computed predictions for static seal characteristics, leakage and axial pressure drop, correlate well with existing measurements for a gaseous nitrogen seal and a liquid nitrogen seal with two-phase at the seal exit plane. The effects of two-phase flow regimes on the dynamic force coefficients and stability of an oxygen damper seal are discussed. Fluid compressibility effects, particularly for mixtures with low mass content of vapor, are of utmost importance. Under these conditions, an increase on seal direct stiffness and reduction of whirl frequency ratio are shown to occur.

Cryogenic fluid damper seals operating close to the liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two-phase flow region which affects the seal performance and reliability. An all-liquid, liquid-vapor, and all-vapor, i.e., a 'continuous vaporization' bulk flow model is presented for prediction of the seal dynamic forced response. Continuity, momentum, and energy (enthalpy) transport equations govern the two-phase flow of a homogeneous saturated mixture in thermodynamic equilibrium. Static and dynamic force performance characteristics for the seal are obtained from a perturbation analysis of the governing equations. Theoretical predictions and comparisons to experimental measurements in a liquid and gaseous nitrogen seal are presented in Part II. The effects of two-phase flow regimes on the dynamic force coefficients and stability of an oxygen damper seal are also discussed.

Lower-limit concentration of active N atoms stored in a cryomatrix has been found using Fourier transform infrared (FTIR) spectroscopic measurements. Bombardment of the matrix by N and N(sub.2) neutrals with energies estimated to be 20 - 120 eV gives a concentration of N(sub.3) radicals proportional to the beam flux in a linear fashion.

The accuracy of detector calibration in the UV, vacuum-ultraviolet, and soft-x-ray spectral ranges could be significantly improved by the use of the synchrotron radiation electrical substitution radiometer (SYRES) as the primary detector standard. The SYRES radiometer is optimized for use with spectrally dispersed synchrotron radiation as supplied by two monochromator beam lines in the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at the Berlin electron-storage ring (BESSY). Wavelength ranges from 0.8 to 25 nm and from 35 to 400 nm are covered. The typically available radiant power of [approximately]1-10 [micro]W can be measured with the SYRES radiometer with a standard relative uncertainty of less than 0.2%. The spectral responsivity of qualified photodiodes for use as secondary detector standards is determined by direct comparison with the primary detector standard at an arbitrary wavelength. At present, the scale of spectral responsivity is realized with a standard relative uncertainty of well below 1% in the spectral ranges 0.8-3.5 nm, 5-25 nm, and 120-400 nm. We provide a comprehensive description of the SYRES radiometer and of the two facilities for detector calibration in the UV and vacuum-ultraviolet spectral ranges and in the soft-x-ray spectral range, respectively, and we discuss the achievable uncertainties in the calibration of detectors. Key words: Radiometry, cryogenics, electrical substitution, detector standards, PTB, synchrotron radiation.

Application of soft x-ray photoemission spectroscopy to the initial interface formation of In-In53Ga47As(100) for room and cryogenic temperatures indicated a predominantly three-dimensional mode of growth for room-temperature metallization, with accompanying As diffusion. Clustering and As outdiffusion is restricted for low temperature metallization. Interface geometry and bonding at low temperature variations conditioned surface state distribution and fermi level pinning position.

The simplicial approximation and centers-of-gravity design centering methods were compared. They were applied to several rapid single flux quantum circuits and analytical test functions to test their effectiveness. Circuit simulation was conducted using a SPICE-type program with analog behavior modeling and transient noise simulation capabilities. An interactive yield optimization framework for cryoelectronic circuits was developed using the yield optimization strategies.

A 61-channel superconducting quantum interference device-based MEG measurement system cooled by a hybrid Gifford-McMahon/Joule-Thomson cryocooler has been fabricated. The system is capable of conforming to a human head due to the 61-channels of axial gradiometers arranged on a spherical surface. The system was demonstrated by applying it for faint biomagnetic field measurements of the human brain.

A high-power flip-chip metal-oxide-semiconductor microprocessor module operates efficiently in liquid nitrogen. The thermal resistance is 0.15 K/W in the nucleate boiling regime under pool boiling conditions without a lid. The thermal resistance is maintained up to a total power of 50 W. The use of a lid increases the resistance to about 4 K/W. The module consists of 12 thermal test chips of area 0.40 cm squared.

There have been few experimental reports on cryogenic two-phase fluids and cavitation phenomena using the irradiation of pulsed high-power laser. This paper describes an investigation of the behavior of laser induced cavitation bubble in cryogenic liquid nitrogen. The bubble is produced by a pulsed ruby laser focused in the special cryostat. The production, growth, and rebound phenomena of the bubbles are visualized by diffusive shadowgraph technique with an image-converter camera. To compare with the experimental results, a numerical study has also been performed on the dynamics of a single spherical bubble in liquid nitrogen under the conditions of nonequilibrium phase change.

The AlGaAs-GaAs vertical cavity surface-emitting lasers (VCSEL) exhibit thermally stable operations over a wide range of cryogenic temperatures to give a high degree of efficiency that includes high slope, power efficiency, and lower power dissipation and threshold characteristics. VCSEL is also used for high speed optical link for cryogenic applications. The applications of this laser include the designing of a free space optical interconnect configuration and high speed frequency modulation at a rate of 2 gigabits per second.

Seizure phenomena in pin-on-disk tests have been studied for 'soft' and 'hard' steel specimens. Differences in competing and dominant wear mechanisms under steady state friction have been preserved for 'soft' and 'hard' specimens in the region of transition to seizure or galling. Severe wear was observed for 'soft' specimens under all loads tested, while adhesion and splitting off of wear particle conglomerates (microseizure) were identified for 'hard' specimens. The contact temperature, calculated in accordance with the temperature model of plastically deformed contact spots (Kuhlmann-Wilsdorf), has appeared to be low for 'soft' specimens and not sufficient for adhesion interaction. The effect of oxide films on the friction of 'hard' specimens has been estimated in accordance with the temperature model for a coated semi-infinite body (Tian and Kennedy). The insulated oxide films on the surface of 'hard' specimens create the 'skin effect' and lead, therefore, to raising the temperature up to the temperature of adhesion interaction. Temperature instability of hard surfaces has been demonstrated to result from the 'skin effect' and from a disturbance in equilibrium of formation and failure of oxide films. It has been shown that for 'soft' specimens the prime cause of transition to seizure was the mechanical interlocking between the wear particles and the soft disk surface combined with mechanical instability, while for 'hard' specimens the cause was temperature instability. A more realistic temperature model of the contact has been considered, which takes into account some competing wear mechanisms (oxidational wear, ploughing, delamination) and the effect of wear particles.

A theory for analyzing the effects of elastic deformations of the seal wall on the dynamic characteristics of high pressure cryogenic annular seals under concentric operation is presented. The bulk flow continuity, axial and circumferential momentum, and the energy transport equations are utilized to determine the pressure distribution in the seal. Thermophysical properties of the cryogenic fluid are assumed to be functions of the local pressure and temperature. The wall deformations are obtained using an iso-parametric, axi-symmetric Finite Element formulation of the seal wall. A perturbation analysis is employed to arrive at the first order solution which yields the rotordynamic coefficients. Results obtained for the case of Space Shuttle Main Engine Oxygen Turbopump (SSME-HPOTP) Preburner Seal show a significant impact of seal flexibility on the dynamic coefficients.

Significant advances in the development of high electron mobility field-effect transistors (HEMT's) have resulted in cryogenic, low-noise amplifiers (LNA's) whose noise temperatures are within an order of magnitude of the quantum noise limit (hv/k). Further advances in HEMT technology at cryogenic temperatures may eventually lead to the replacement of maser and superconducting-insulator-superconducting (SIS) front-ends in the 1-100 GHz frequency band. Key to identification of the best HEMT's and optimization of cryogenic LNA's is accurate and repeatable device measurements at cryogenic temperatures. A cryogenic on-wafer noise and scattering parameter measurement system has been developed to provide a systematic investigation of HEMT noise characteristics. In addition, an improved parameter extraction technique has been developed to help understand the relationship between device structure and LNA performance.

The design of a cooling structure for an NbTi superconducting magnet that is directly cooled by a 4-K Gifford-McMahon refrigerator is considered. Specifically, two types of experiments were conducted to find a cooling structure that will allow ramping up of the NbTi coil to six tesla within a five-minute period. The first concerned finding an appropriate structure based on measured thermal resistances of different structures. The second involved measuring the temperature difference between the coil and the cooling structure during operation.

Eddy current losses in conducting plates placed in a non-uniform alternating magnetic field at cryogenic temperatures have been calculated taking into account temperature dependencies of resistivity, heat capacity and heat-transfer coefficient. The calculation method is based on a coupled solution of a quasi-stationary electromagnetic problem and a non-stationary heat-conduction equation. A simplification of the task is achieved by neglecting eddy current reaction and free space charge. In this case the problem is solved in two stages: 1) the calculation of electromagnetic field; 2) the determination of a temperature distribution in the plate. As the first boundary condition for heat-conduction equation it is assumed that the heat transfer from edges of the plate equals zero. The second boundary condition is determined as a solution of the integral equation describing the law of conservation of energy relevant to the plate. The nonlinear two-dimensional heat conduction equation has been solved using partition of coordinates, implicit difference approximation and modified Thomas algorithm for obtained finite-difference equations. The numerical results remain in a good agreement with data obtained by means of an experimental model of the cryogenic device, while neglecting of thermal processes results in substantial errors amounting up to several hundreds percent.

The analysis and design of buried chilled pipelines in frost heaving soils warrants a study of the complex pipe-soil interaction. Stress gradients are generated at the interface between frozen and unfrozen ground because of differential heave, produced as the chilled pipe crosses from the unfrozen, heave-susceptible terrain to the frozen, nonheaving one, resulting in the generation of uplift forces acting on the pipe portion buried in the frozen ground. The present paper characterizes the load-resistance response of the uplift-resistant side of the pipe section as it is pulled upward at a constant displacement rate through the frozen ground. Crack patterns in the frozen soil around the pipe section were observed in uplift tests. In view of this, a theoretical assessment of tension-fractured and compression-crushed zones, developed in the vicinity of the pipe, producing a reduced peak uplift resistance is discussed.

The construction and maintenance of structures subject to subzero (

This article presents the principle of using sequential freezing for the purpose of freeze protection in a solar water heater. Sequential freezing is accomplished by maintaining a temperature gradient across the collector so that water is squeezed out of the collector rather than being trapped by ice at the ends of the tubes. The authors give the mathematical models of tubular sequential freezing, compare the predicted results of models with the measured data, and investigate the influences of various factors on the tubular sequential freezing state with the model. A series of experiments show that a solar water heater designed according to the principle of sequential freezing can operate effectively in winter without drain-down, electricity, and heat exchanger systems.

The construction and experimental results of a novel compact anti-Compton spectrometer system are reported. The device consists of a large BGO scintillation crystal with a cylindrical well. Inside the well, a 56 mm diameter, 57 mm high (n-type) germanium crystal is mounted. The entire assembly is cooled down to 104 K. Scintillation light from the BGO crystal is detected by a 127 mm diameter PM tube. The assembly has the advantage of a compact design and the absence of any material between the Ge and the BGO crystal. A Peak-to-Total ratio of 0.60 is obtained with a 60Co source and 0.74 with a 137Cs source.