A systematic study of the etch characteristics of GaN, AlN and InN has been performed with boron halides- (BI{sub 3} and BBr{sub 3}) and interhalogen- (ICl and IBr) based Inductively Coupled Plasmas. Maximum etch selectivities of -100:1 were achieved for InN over both GaN and AlN in the BI{sub 3} mixtures due to the relatively high volatility of the InN etch products and the lower bond strength of InN. Maximum selectivies of- 14 for InN over GaN and >25 for InN over AlN were obtained with ICl and IBr chemistries. The etched surface morphologies of GaN in these four mixtures are similar or better than those of the control sample.

A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of {Tc}, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc.

In this paper, a time-dependent engine model is used for predicting hydrogen engine efficiency and emissions. The model uses basic thermodynamic equations for the compression and expansion processes, along with an empirical correlation for heat transfer, to predict engine indicated efficiency. A friction correlation and a supercharger/turbocharger model are then used to calculate brake thermal efficiency. The model is validated with many experimental points obtained in a recent evaluation of a hydrogen research engine. A The validated engine model is then used to calculate fuel economy and emissions for three hydrogen-fueled vehicles: a conventional, a parallel hybrid, and a series hybrid. All vehicles use liquid hydrogen as a fuel. The hybrid vehicles use a flywheel for energy storage. Comparable ultra capacitor or battery energy storage performance would give similar results. This paper analyzes the engine and flywheel sizing requirements for obtaining a desired level of performance. The results indicate that hydrogen lean-burn spark-ignited engines can provide a high fuel economy and Equivalent Zero Emission Vehicle (EZEV) levels in the three vehicle configurations being analyzed.

MS0 is a promising alternative to incineration for the treatment of a variety of organic wastes. Lawrence Livermore National Laboratory (LLNL) has prepared a facility (please see the photo attached) in which an integrated pilot-scale MS0 treatment system is being tested and demonstrated. The system consists of a MS0 vessel with a dedicated off-gas treatment system, a salt recycle system, feed preparation equipment, and a ceramic final waste forms immobilization system. The MSO/off-gas system has been operational since December 1997. The salt recycle system and the ceramic final forms immobilization became operational in May and August 1998, respectively. We have tested the MS0 facility with various organic feeds, including chlorinated solvents; tributyl phosphate/kerosene, PCB-contaminated waste oils & solvents, booties, plastic pellets, ion exchange resins, activated carbon, radioactive-spiked organics, and well-characterized low- level liquid mixed wastes. MS0 is a versatile technology for hazardous waste treatment and may be a solution to many waste disposal problems. In this paper we will present our operational experience with MS0 and also discuss its process capabilities as well as performance data with different feeds.

We present a brief summary of the current status of the Advanced Photon Source (APS) at Argonne National Laboratory and of the facilities at two of the APS sectors operated by the Basic Energy Sciences Synchrotrons Radiation Center (BESSRC). This is followed by a report on recent measurements at BESSRC on the phenomenon of Nuclear Excitation by Electronic Transition (NEET).

Epitaxial growth of AlAs-InAs short-period superlattices on (001) InP can lead to heterostructures exhibiting strong, quasi-periodic, lateral modulation of the alloy composition; transverse satellites arise in reciprocal space as a signature of the compositional modulation. Using an x-ray diffractometer equipped with a position-sensitive x-ray detector, we demonstrate reciprocal-space mapping of these satellites as an efficient, nondestructive means for detecting and characterizing the occurrence of compositional modulation. Systematic variations in the compositional modulation due to the structural design and the growth conditions of the short-period superlattice are characterized by routine mapping of the lateral satellites. Spontaneous compositional modulation occurs along the growth front during molecular-beam epitaxy of (AlAs) (InAs)n short-period superlattices. The modulation is quasi-periodic and forms a lateral superlattice superimposed on the intended SPS structure. Corresponding transverse satellites arise about each reciprocal lattice point, and x-ray diffraction can be routinely used to map their local reciprocal-space structure. The integrated intensity, spacing, orientation, and shape of these satellites provide a reliable means for nondestructively detecting and characterizing the compositional modulation in short-period superlattices. The analytical efficiency afforded by the use of a PSD has enabled detailed study of systematic vacations in compositional modulation as a function of the average composition, the …

Sediments from relic Lake Golbasi were analyzed by X-ray fluorescence with synchrotrons radiation to determine changes in element concentrations over time with selected elements serving as proxies for environmental change. Increases in Ca and Sr suggest soil formation during a dry period, from ca. 4500 BC to ca. 200 AD at which point K, Rb, Zr, Ti, and Y increase, indicating the return of a wet environment. Soil erosion, represented by Cr and Ni, increases ca. 7000 BC, probably as a consequence of environmental change, prior to suggested exploitation of natural resources by the newly urbanized society of the third millennium BC.

No endeavor is risk-fire and as we realize the inherent risks in society, our only viable solution is to manage the risk. Application of an integrated risk management program of a large technological system like the DOE complex is a difficult, task; but it is the only rational means to optimize the risk-benefit equation. An effective risk management culture-within the DOE complex will in the long run, ensure a consistent response to mitigate identified risks. An effective risk management program provides responsible administrative planning and logical application of the best technical analyses. It requires the involvement of all personnel. Our objective in this paper is to point out broad perspectives that raise concerns about future DOE ask management issues and to suggest some possible remedies.

Crystalline nanoprecipitates of Xe have been produced by ion implantation into high purity Al at 300 K. With an off-zone axis TEM imaging technique, the nanocrystals may be clearly structure imaged against a nearly featureless background. Under the 1 MeV electron irradiation employed for the HREM observation, Xe nanocrystals exhibit a number of readily observed physical phenomena including migration within the matrix, changes in shape, faulting, melting, crystallization and coalescence. The various phenomena observed as changes in the Xe nanocrystals reflect changes of matrix cavity-surface structure. The Xe nanocrystal thus allows investigation indirectly into changes in interface morphology at the atomic level, resulting in this instance from electron irradiation damage. Such changes have heretofore been inaccessible to observation.

When a noble gas element such as Xe is implanted in an fcc metal matrix such as Al at room temperature, a fine dispersion of precipitates forms. The precipitates are elementary fcc crystals up to diameters of several nanometers (for Xe in Al, 8-10 rim), above which they are non-crystalline. The precipitates exhibit a cube-on-cube orientation relation with the matrices and have lattice parameters which are much larger than those of the matrices (a{sub Xe} = 1.5a{sub Al}). Thus the interphase interfaces are incommensurate though the lattices are isotactic. The precipitates assume the shape of matrix cavities; for an Al matrix, at equilibrium this is a cuboctahedron, a {r_brace}111{l_brace} octahedron truncated at the corners on {l_brace}100{r_brace}. Fig. 1 is a sketch of a dispersion of such cuboctahedra, viewed approximately along a {l_angle}110{r_angle}. For this study specimens were prepared in the HVEM-Tandem Facility at Argonne National Laboratory by implanting 35 keV Xe to a dose of 4x10{sup 19} m{sup {minus}2} into well-annealed 5N Al discs which had been thinned by jet electropolishing. The range of the implant is approximately 25 nm. Specimens were examined at high resolution in the JEOL ARM-1000 high voltage electron microscope (HVEM) at the High Resolution Beam …

This paper describes the development and evaluation of neural network-based systems for industrial resistance spot welding process control and weld quality assessment. The developed systems utilize recurrent neural networks for process control and both recurrent networks and static networks for quality prediction. The first section describes a system capable of both welding process control and real-time weld quality assessment, The second describes the development and evaluation of a static neural network-based weld quality assessment system that relied on experimental design to limit the influence of environmental variability. Relevant data analysis methods are also discussed. The weld classifier resulting from the analysis successfldly balances predictive power and simplicity of interpretation. The results presented for both systems demonstrate clearly that neural networks can be employed to address two significant problems common to the resistance spot welding industry, control of the process itself, and non-destructive determination of resulting weld quality.

A method is described for inverse modeling of material deformation in applications of importance to the sheet metal forming industry. The method was developed in order to assess the feasibility of utilizing empirical data in the early stages of the design process as an alternative to conventional prototyping methods. Because properly prepared and employed artificial neural networks (ANN) were known to be capable of codifying and generalizing large bodies of empirical data, they were the natural choice for the application. The product of the work described here is a desktop ANN system that can produce in one pass an accurate die design for a user-specified part shape.

Nanometer-scale compositional structure in InAsxP1.InNYAsxPl.x-Y/InP, grown by gas-source molecular-beam epitaxy and in InAsl-xPJkAsl$b#InAs heterostructures heterostructures grown by metal-organic chemical vapor deposition has been characterized using cross-sectional scanning tunneling microscopy. InAsxP1-x alloy layers are found to contain As-rich and P-rich clusters with boundaries formed preferentially within (T 11) and (111) crystal planes. Similar compositional structure is observed within InNYAsxP1-x-Y alloy layers. Imaging of InAsl-xp@Asl#bY superlattices reveals nanometer-scale clustering within both the hAsI-.p and InAsl$bY alloy layers, with preferential alignment of compositional features in the direction. Instances are observed of compositional structure correlated across a heterojunction interface, with regions whose composition corresponds to a smaller unstrained lattice, constant relative to the surrounding alloy material appearing to propagate across the interface.

Cross-sectional scanning tunneling microscopy has been used to characterize compositional structure in InAs{sub 0.87}Sb{sub 0.13}/InAs{sub 0.73}P{sub 0.27} and InAs{sub 0.83}Sb{sub 0.17}/InAs{sub 0.60}P{sub 0.40} strained-layer superlattice structures grown by metal-organic chemical vapor deposition. High-resolution STM images of the (110) cross section reveal compositional features within both the InAs{sub x}Sb{sub 1{minus}x} and InAs{sub y}P{sub 1{minus}y} alloy layers oriented along the [{bar 1}12] and [1{bar 1}2] directions--the same as those in which features would be observed for CuPt-B type ordered alloys. Typically one variant dominates in a given area, although occasionally the coexistence of both variants is observed. Furthermore, such features in the alloy layers appear to be correlated across heterojunction interfaces in a manner that provides support for III-V alloy ordering models which suggest that compositional order can arise from strain-induced order near the surface of an epitaxially growing crystal. Finally, atomically resolved (1{bar 1}0) images obtained from the InAs{sub 0.87}Sb{sub 0.13}/InAs{sub 0.73}P{sub 0.27} sample reveal compositional features in the [112] and [{bar 1}{bar 1}2] directions, i.e., those in which features would be observed for CuPt-A type ordering.

A major problem with cavitation in pumps and other hydraulic devices is that there is no effective method for detecting or predicting its inception. The traditional approach is to declare the pump in cavitation when the total head pressure drops by some arbitrary value (typically 3o/0) in response to a reduction in pump inlet pressure. However, the pump is already cavitating at this point. A method is needed in which cavitation events are captured as they occur and characterized by their process dynamics. The object of this research was to identify specific features of cavitation that could be used as a model-based descriptor in a context-dependent condition-based maintenance (CD-CBM) anticipatory prognostic and health assessment model. This descriptor was based on the physics of the phenomena, capturing the salient features of the process dynamics. An important element of this concept is the development and formulation of the extended process feature vector @) or model vector. Thk model-based descriptor encodes the specific information that describes the phenomena and its dynamics and is formulated as a data structure consisting of several elements. The first is a descriptive model abstracting the phenomena. The second is the parameter list associated with the functional model. The …

The technical challenge for making two-beam accelerators into realizable power sources for high-energy colliders lie in the creation of the drive beam and in its propagation over long distances through multiple extraction sections. This year we have constructed a 1.2-kA, 1-MeV, electron induction injector for the RTA accelerator. The electron source will be a 8.9 cm diameter, thermionic, flat-surface cathode with a maximum shroud field stress of approximately 165 kV/cm. The injector� s pulse length should be over 120-ns flat top (1% energy variation) with a normalized edge emittance of less than 200 (small pi)-mm-mr. Details of the design and performance of the injector, beam line, and diagnostics will be presented.

Paper presented at the International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (1999) reporting on the progress of the STAR experiment, a complex system of many detector sub-systems which have been installed in a large solenoidal magnet at the Relativistic Heavy Ion Collider (RHIC).

Development of isentropic loading techniques is a long standing goal of the shock physics community. The authors have used the Sandia Z Accelerator to produce smoothly increasing pressure loading on planar iron specimens over time durations of 100 ns and for pressures to 300 Mbar. Free surface velocity measurements on the rear surface of the continuously loaded specimens were made on specimens 0.5-mm and 0.8-mm thick and clearly show the effects of wave evolution into the well known two-wave structure resulting from the {alpha}-{var_epsilon} phase transition beginning at 125 kbar. The resulting wave profiles are analyzed with a rate-dependent, phase transition model to extract information on phase transformation kinetics for isentropic compression of iron. Comparison of the experiments and calculations demonstrate the value of isentropic loading for studying phase transition kinetics.

Significant effort is presently focused on reducing the size and weight of power electronic modules. To achieve these goals in high-power capacitors, alternative materials and fabrication processes are needed. Thin film (<0.5 {micro}m) and bulk capacitors that use perovskite-based ferroelectric dielectrics are promising alternative technologies. Ferroelectrics possess high dielectric constants, thus offering substantial increases in volumetric capacitance. In thin film form, these materials display low loss and high breakdown strength. The unique properties of some of these materials, such as a nonlinear dielectric response or a high energy-storage capacity accompanying a phase change, can be exploited for power electronic capacitors. Prototype capacitors of two such materials, (Ba,Sr)TiO{sub 3} and PbZrO{sub 3}, have been fabricated in both thin film and bulk ceramic form. The influence of fabrication conditions on dielectric properties has been studied. Initial studies have demonstrated the viability of perovskite ferroelectrics for next-generation capacitor components.

It is known that the forming gas (N{sub 2}-H{sub 2} mixture) annealing process required for microcircuit fabrication results in an unacceptable electrical degradation of SrBi{sub 2}Ta{sub 2}O{sub 9} (SBT) ferroelectric capacitors due mainly to the interaction of H{sub 2} with the ferroelectronic layer of the capacitor. We have found a strong relationship between changes in the surface composition of the ferroelectric layer and the electrical properties of SBT capacitors as a result of hydrogen annealing. Mass spectroscopy of recoiled ions (MSRI) analysis revealed a strong reduction in the Bi signal as a function of exposure to hydrogen at high temperatures ({approximately}500 C). The Bi signal reduction correlates with Bi depletion in the SBT surface region. Subsequent annealing in oxygen at temperatures in the range of 700-800 C resulted in the recovery of the MSRI Bi signal, corresponding to the replenishment of Bi in the previously Bi-depleted surface region. XRD analysis (probing the whole SBT film thickness) showed little difference in the XRD spectra of the SBT fti before and after hydrogen and oxygen-recovery annealing. The combined results of the MSRI and XRD analyses can be interpreted as an indication that the degradation of the electrical properties of the SBT capacitors, …

The first measurements of {phi} meson production in Au-Au collisions at AGS energies are presented via the decay to K{sup +} K{sup {minus}}. A measurement of the centrality dependence of the yield shows an increase similar to that seen for the K{sup {minus}} with a spectral shape consistent with a relativistic Breit-Wigner distribution within the statistical errors of the present data set. Future analysis using the full data set with 4 times the statistics will allow a more accurate determination of the yields, slopes and spectral shapes.

During the 1988/1989 run at the Fermilab Tevatron, the CDF detector collected {approx equal}4.1 pb{sup {minus}1} of p{bar p} data at {radical}s = 1.8 TeV. The main goals of this run being physics at high p{sub t}, the CDF trigger was tuned'' for maximizing signals from Z{sup 0}s, Ws, t-quarks, etc. As such, compared to the high p{sub t} physics, the b-physics program was of secondary importance other than that which would be used for background calculations. Also, CDF had no vertex chamber capability for seeing displaced vertices. However, significant b-quark, physics results are evident in two data samples; inclusive electrons and inclusive J/{psi} where J/{psi} {yields} {mu}{sup +}{mu}{sup {minus}}. We can then ask ourselves, given all this, why is it that CDF is able to do b-quark physics The answer is that nature has been kind enough to provide b-quarks at an extremely high rate at the Tevatron. The production cross-section for b{bar b} production is quite large. In the rest of this paper, I will try to specify the goals for b-physics using the inclusive electrons and J/{psi} signals for the 1988/1989 data set. I will then provide a brief look at the data, and will finish with …

HIPROTECT (pronounced High-protect) is a system designed to protect national archaeological and natural treasures from destruction by vandals or looters. The system is being developed jointly by the Lawrence Livermore National Laboratory and the University of California at Riverside under the DOD Legacy Resource Management Program. Thousands of archaeological sites are located on military bases and national park lands. Treasure hunters or vandals are pillaging and destroying these sites at will, since the sites are generally located in remote areas, unattended and unprotected. The HIPROTECT system is designed to detect trespassers at the protected sites and to alert park officials or military officials of intrusions. An array of sensors is used to detect trespassers. The sensors are triggered when a person or vehicle approaches the site. Alarm messages are transmitted to alert park officials or law enforcement officials by way of a cellular telephone link. A video and audio system is included to assist the officials in verifying that an intrusion has occurred and to allow two-way communication with the intruders.

The increasing emphasis on envirorunental issues, waste reduction, and improved efficiency for industrial processes has mandated the development of new chemical and physical sensors for field or in-plant use. The Lawrence Livermore National Laboratory (LLNL) has developed a number of technologies for sensing physical and chemical properties. Table 1 gives some examples of several sensors. that have been developed recently for environmental, industrial, commercial or government applications. Physical sensors of pressure, temperature, acceleration, acoustic vibration spectra, and ionizing radiation have been developed. Sensors developed at LLNL for chemical species include inorganic solvents, heavy metal ions`, and gaseous atoms and compounds. Primary sensing technologies we have employed have been based on optical fibers, semiconductor optical or radiation detectors, electrochemical activity, micromachined electromechanical (MEMs) structures, or chemical separation technologies. The complexities of these sensor systems range from single detectors to more advanced micro-instruments on-a-chip. For many of the sensors we have developed the necessary intelligent electronic support systems for both local and remote sensing applications. Each of these sensor technologies are briefly described in the remaining sections of this paper.