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We present observations of 50 deg2 of the Mopra carbon monoxide (CO) survey of the Southern Galactic Plane, covering Galactic longitudes l = 300–350° and latitudes |b| ⩽ 0.5°. These data have been taken at 0.6 arcmin spatial resolution and 0.1 km s−1spectral resolution, providing an unprecedented view of the molecular clouds and gas of the Southern Galactic Plane in the 109–115 GHz J = 1–0 transitions of 12CO, 13CO, C18O, and C17O.
We present a series of velocity-integrated maps, spectra, and position-velocity plots that illustrate Galactic arm structures and trace masses on the order of ~106 M⊙ deg−2, and include a preliminary catalogue of C18O clumps located between l = 330–340°. Together with the information about the noise statistics of the survey, these data can be retrieved from the Mopra CO website and the PASA data store.
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
Expert judgement is frequently used within general insurance. It tends to be a method of last resort and used where data is sparse, non-existent or non-applicable to the problem under consideration. Whilst such judgements can significantly influence the end results, their quality is highly variable. The use of the term “expert judgement” itself can lend a generous impression of credibility to what may be a little more than a guess. Despite the increased emphasis placed on the importance of robust expert judgements in regulation, actuarial research to date has focussed on the more technical or data-driven methods, with less emphasis on how to use and incorporate softer information or how best to elicit judgements from others in a way that reduces cognitive biases. This paper highlights the research that the Getting Better Judgement Working Party has conducted in this area. Specifically, it covers the variable quality of expert judgement, both within and outside the regulatory context, and presents methods that may be applied to improve its formation. The aim of this paper is to arm the insurance practitioner with tools to distinguish between low-quality and high-quality judgements and improve the robustness of judgements accordingly, particularly for highly material circumstances.
Ion beam synthesis of CoSi2 layers in Si by MEVVA (Metal Vapor Vacuum Arc) implantation has been performed under various conditions. The formation and characteristics of these CoSi2 layers have been studied by XTEM, RBS, AFM, X-ray diffraction, ellipsometry, electrical and Hall effect measurements. It was found that a higher substrate temperature during implantation results in an as-implanted Co distribution closer to the surface and hence the formation of a shallower CoSi2 layer after annealing. Buried CoSi2 layers of good crystal quality and low resistivity CoSi2 can be formed by MEVVA implantation and annealing under appropriate conditions. A strong temperature dependence of the Hall coefficient showing a large peak at around 100K was observed for the CoSi2 layers formed in p-type Si substrates but not in n-type substrates. The properties and their dependence on the processing conditions, in particular, the substrate temperature during implantation, are presented and discussed.
The pixel cross-talk is investigated in two-dimensional amorphous silicon (a-Si:H) imager arrays based on the new high fill factor design. In this configuration a continuous a-Si:H sensor extends over the whole surface of the imager, and a buried insulator material with low dielectric constant is used to separate the sensor from the underlying active matrix readout circuit. We find that the lateral conduction between neighboring pixels is mainly determined by the quality of the buried insulator-sensor interface, rather than the specific buried material itself. Minimum cross-talk values below 1% are obtained for different insulator materials including silicon oxynitride and thicker polymer based resins. The quality of this interface also affects trapping and recombination of the photogenerated carriers, influencing important imager properties such as sensitivity and image lag.
A new process of surface micromachining has been developed, where amorphous silicon (a-Si) and oxynitride films are used as structural and sacrificial layers on the glass substrate, respectively. Due to glass as the substrate material, the temperatures for all process steps need to be lower than 600°C. Some generic mechanical microstructures such as cantilever beams, bridges, and membranes have been fabricated. The stress changes of a-Si films with annealing temperatures are studied. It is found that the residual stress can be minimized using thermal annealing at 430°C for a few hours. In addition, some process issues such as a-Si film bubbling, the film adhesion of a-Si to the glass substrate, and stiction during structure release are discussed.
This paper describes an experimental and theoretical analysis of the near-field thermal performance of a backfilled disposal vault in which the waste containers are emplaced in boreholes and surrounded by a bentonite-sand buffer. Effects of heat and moisture diffusion on the thermal performance of clay-based buffer and backfills were studied by means of laboratory scale experiments. The bentonite-sand buffer exhibited cracking due to desiccation. The impact of such cracking on the perforamnce of buffer as an engineered barrier is being investigated.
An integrated finite difference computer code ‘TRUCHAM’ was written to analyze the transient heat and moisture flow regime in a disposal vault and was validated by a scale model heater experiment. It is hoped that with proper characterization of the material properties ‘TRUCHAM’ can be employed as a useful tool in assessing the thermal response of the prototype disposal vault. Further work is needed to integrate the effects of heat and moisture on the shrinkage and expansion of clay-based buffer and backfills.
The Al-Cu system has been used to test the application of grazing incidence EXAFS and x-ray reflectivity measurements to interface systems. Both techniques have been found to be sensitive to compound formation and interdiffusion, and with further development of analysis procedures should be very useful complements to more traditional techniques.
Si samples, with and without masking oxide films, implanted with various doses of As, P, or BF2 have been evaluated on the formation of titanium suicides from titanium films. In all cases, suicide reaction for implantation with masking oxide films is more difficult than that for implantation without masking oxide films. Suicide reaction becomes more difficult with decreasing implant energy in the range over a critical dose. In the case of implantation with masking oxide films, knocked oxygen has been found at the surface of Si substrate. Suicide formation after removing the surface layers containing considerable amount of knocked oxygen with argon back-sputtering is as easy as suicide formation for implantation without masking oxide. The difficulty of Ti silicidation for implantation with masking oxide films is believed to be due to the effects of interference from knocked oxygen.
Thin film interactions between a-(Ni-Nb) and polycrystalline Au over-layers have been studied with high depth resolution (≤1.7nm) Rutherford backscattering (RBS) and TEM to obtain information on the early stages of reaction at the interface. The RBS spectra from Au indicated that the interdiffused samples consisted of two layers: an Au-Nb binary layer on the surface and a ternary Au-Ni-Nb compound layer beneath the binary layer. The growth kinetics of the ternary compound layer differed in samples which had been relaxed prior to Au deposition from the kinetics for unrelaxed samples. Furthermore, cross section TEM micrographs showed that relaxed and unrelaxed samples exhibit different microstructures after the early stages, of annealing. We interpret this result to indicate that the reaction stages in relaxed samples are not as advanced as those in the unrelaxed samples.
Single probe infrared low coherence optical interferometry has been proven to be an effective tool for characterization of thin and ultra-thin semiconductor Si and compound materials wafers. Its application was however limited to wafers transparent at probing wavelength, and having relatively smooth surfaces. Purpose of this paper is to present an extension of low coherence interferometry to characterization of non-transparent wafers, and wafers with rough surfaces.
A new method has been developed for making self-supporting, thin films which can be used for the in situ study, by hot-stage, transmission electron microscopy, of the reaction between Ni and GaAs. The thin-film, lateral diffusion-couples have been used to study both the kinetics and the formation of new phases. The growth rate of the ternary compound, N2GaAs showed a parabolic time dependence. At an annealing temperature of 300*C, the present experimental results show that Ni is the diffusing species and that the Ga and As remain essentially immobile. Diffusion coefficients obtained by this method are in very good agreement with those which have been obtained using conventional thin-film techniques. The results of this new technique are particularly important in view of the difficulty in identifying the composition of the product phase by methods which do not have the same lateral resolution.
Alternating layers of Ni and Nb with a total thickness of 1060Å, and Ni and Cr with a total thickness of 840Å were deposited by electron beam evaporation on silicon. The individual layer thicknesses were adjusted in such a way as to obtain 50/50 at% compositions of Ni-Nb and Ni-Cr; the thicknesses were around 100Å for Ni and 170Å for Nb, and 100Å of Ni and 110Å of Cr. The films were bombarded with 350 keV Cr+ ions at a dose of 2 × 10 ions cm. RBS and TEM techniques were used to study the mixing and microstructure. Almost complete mixing and amorphization have been observed for the Ni-Nb system. Ni-Cr film has revealed very little mixing compared to Ni-Nb film and the microstructure remained polycrystalline. Sputter (rf) deposited Ni-Cr film also remained polycrystalline both before and after ion irradiation. The Ni-Cr System appears to be an exception to the structural difference rule for amorphous phase formation by ion irradiation.
An n+ /i/p /i/n amorphous silicon bipolar transistor has been successfully fabricated with a current gain of 12 and a response speed of 30 yS This new structure of bipolar transistor has a very thin base (200Å), therefore, high gain and high speed is obtainable. This device has a very promising applications as a flat panel display transistor and a phototransistor in photosensing element/array and photo coupler. Electrical and optical characteristics have been extensively investigated. Theoretical model and experimental results are plausibly in good agreement.
Variation from the fundamental structure is also been developed, such as the Schottky emitter Al/i/p /i/n bipolar transistor.
The interaction of Ti with A12O3 under UHV conditions has been studied by AES and UPS. Ti was deposited by iterated and successively thicker evaporations (up to a total thickness of 91 Å) under UHV conditions onto the alumina substrate at room temperature. The oxide substrate was grown on Al/Si(111) in an adjacent VHV preparation chamber. The last deposition was followed by in situ annealing. It was found that, contrary to indications of thermodynamic considerations using bulk equilibrium data, Ti interacts strongly with alumina at room temperature, dissociating it to metallic Al and forming TiO2 at the interface. This reaction is limited, resulting in an interface width of ∼10 Å and allowing subsequent evaporations to homogeneously cover the products. Annealing to 500°C does not produce any evidence of outdiffusion or extensive interface reactions, implying that the interface oxide is stable and an effective barrier to Al (and/or Ti) diffusion up to this temperature.
Ion beam mixing effects on metals and highly doped semiconductors on GaAs for formation of ohmic contacts have been studied. In this study, we have principally selected Pt as metal and Ge as semiconductors electrodes for GaAs. In Pt/GaAs system, we observed alloying phenomena induced by Si+, Ar+, Ge+ ion mixing effects. The amount of GaAs reacted with Pt was found to be proportional to the mass of the incident ions for constant dose. Concernig with the formation of ohmic contacts, only in the case of Si implantation through Pt films, the conversion from Schottky- to ohmic-contact was observed due to ion beam mixing effects. In Ge/GaAs system, we observad the solid state epitaxy for implanted Ge layer by the first annealing at 450°C in the two step annealing, but no activation of the implanted species. For activating implanted species, the second annealing at 800°C was effective. Concerning with the formation of ohmic contacts, we observed that the ohmic I-V characteristics for Ge/GaAs system could be obtainable when the following conditions were satisfied at the same time: 1) high dose implantation of As+ into Ge layer, 2) low dose implantation of Si into Ge/GaAs boundary and 3) relatively short period annealing in the second annealing step. From such study, it is concluded that ion beam mixing in conjunction with rapid annealing would be most promising for forming stable and reproducible ohmic contacts.