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The Baltic Sea is a semi-enclosed brackish water basin where sea ice occurs annually. The sea-ice study discussed here was conducted as a Finnish-Japanese cooperative research programme entitled "Ice Climatology of the Okhotsk and Baltic Seas’’ to investigate the structure and properties of the brackish ice in the Baltic Sea. Ice, snow and water samples were collected at Santala Bay, near the mouth of the Gulf of Finland, once a week from 20 January to 12 April 1999. The salinity and oxygen isotopic composition (δ18O) of the samples were measured. The ice samples were analyzed stratigraphically. The ice was composed of a granular upper layer, occupying approximately one-third of the entire ice thickness, and underlying columnar ice toward the bottom. The crystallography structure and δ18O values reveal that the granular ice consisted of two layers with different origins, i.e. snow ice and superimposed ice. The fraction of snow relative to the total thickness was estimated. The limited data show a significant contribution of the snow cover to the sea-ice development. The salinity of the granular ice was higher than that of the columnar ice, implying that the mechanism of entrapment of brine may be different between the two ice types.
Electromagnetic–induction (EM) instruments can be used to estimate Sea-ice thickness because of the large contrast in the conductivities of Sea ice and Sea water, and are currently used in investigations of Sea-ice thickness. In this Study we analyze Several Snow, ice and Sea-water Samples and attempt to derive an appropriate formula to transform the apparent conductivity obtained from EM measurements to the total thickness of Snow and ice for all regions and Seasons. This was done to Simplify the EM tuning procedure. Surface EM measurement transects with the instrument at varying heights above the ice were made in the Chukchi Sea, off East Antarctica, in the Sea of Okhotsk and in Saroma-ko (lagoon). A Standardized transformation formula based on a one-dimensional multi-layer model was developed that also considers the effects of water-filled gaps between deformed ice, a Saline Snow Slush layer, and the increase in the footprint Size caused by increasing the instrument height. The overall average error in ice thickness determined with the Standardized transform was <7%, and the regional average errors were 2.2% for the Arctic, 7.0% for the Antarctic, 6.5% for the Sea of Okhotsk and 4.4% for Saroma-ko.
In 1987 an ice core to the bedrock at a depth of 85.6 m was drilled at the top of Høghetta ice dome in northern Spitsbergen. Chronology of the ice core was examined by tritium and 14C methods showing time gap at about 50 m depth. The age of three bottom ice samples was determined as 4150–5670 year B.P. by 14C method done for frozen bacteria colonies and a frozen petal. This chronology and negative bottom temperature of −9.4°C suggest that glaciers in Spitsbergen shrank considerably during the hypsithermal. The pH of melt-water samples lower than 5.0 corresponds well to large northern hemispheric volcanic eruptions during the last 300 years. Increase of acidity from 30 m depth to the surface may reflect the spread of air pollution to the Arctic during the past 200 years. On the basis of ice-core analyses on electrical conductivity, pH, chemical composition and air bubble pattern, climate and environment in Spitsbergen during the last 6000 years are discussed.
Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice-sheet contribution to global mean sea-level change. Here we reconstruct past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronization of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 a, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. Our results therefore reveal larger amplitudes of changes in SMB at EDC compared with DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared with DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 0.2 from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends.
We have made a 12CO(J = 1−0) survey of the LMC with NANTEN. A sample of 55 giant molecular clouds has been identified and comparisons with stellar clusters, HII regions and SNRs are presented. The connection between the clouds and cluster formation is discussed.
We have made 12CO(J=1−0) observations of the LMC with NANTEN. We report the results of a comparison between CO clouds and SNRs in the LMC. Among the 35 known SNRs, only 10 are possibly associated with CO clouds. These 10 CO clouds and SNRs deserve follow-up studies for possible interactions. We present overlays of CO clouds on the optical images of some of these SNRs.
We have made 12CO(J=1-0) observations in the LMC with NANTEN, and compared the detected giant molecular clouds (GMCs) with HII regions and stellar clusters. It is found that ~ 80% of the GMCs are associated with HII regions. The results of comparisons of the GMCs with the HII regions and the stellar clusters are presented.
We have made 12CO(J=1−0) observations of the LMC with the NANTEN millimeter-wave telescope and identified about 100 distinct giant molecular clouds (GMCs). A detailed comparison of the GMCs with stellar clusters and a UV image is discussed.
Fully sampled 12CO(J=1−0) observations of the whole extent of the LMC have been made with a linear resolution of ~ 30 pc at a detection limit of N(H2) = 2 × 1021 cm−2. In addition, several selected regions have been mapped with higher sensitivity corresponding to a detection limit of 1 × 1021 cm−2. Based on these results, a new estimate of the molecular mass in the LMC is presented.
Atomic structures of amorphous silicate dusts with the MgSiO3 composition were simulated by molecular dynamics method as a function or the dust density based on the assumption that the density corresponds to cooling rate of dust formation. The SiO4 tetrahedra are more polymerized with decreasing density, suggesting phase separation between SiO2-rich and MgO-rich components in less dense dusts formed by rapid condensation. A mode of atomic vibration probably due to the Si-0 bending is different in the amorphous silicates with different densities. This may cause changes of the 20 μm bands of IR spectra of silicate dusts with different cooling rates.
Electron beam excited plasma (EBEP) CVD is a novel fabrication route for poly Si. Deposition was carried out on Si and SiO2 layer from pure SiH4 without hydrogen dilution. Crystalline silicon (μc-Si:H) films were made with electron acceleration voltage, discharge current, source gas flow rate, chamber presser, substrate temperature varied systematically. Average grain size was about 10 nm. Crystalline ratio was up to 0.7 at the maximum. The films contain about 19 at% hydrogen in spite of no dilution. It is considered that EBEP supplies much about atomic hydrogen due to the high decomposability of the source gas.
A fundamental concept combining a molecular behavior and macro-continuum phenomenon is presented for a multicomponent solute diffusion problem in bentonite clay, which is a key component of the Engineering Barrier System (EBS) of high-level radioactive waste disposal (HLRW). Bentonite is a micro-inhomogeneous material. Properties of the saturated bentonite are characterized by the constituent clay mineral (montmorillonite) and water, namely montmorillonite hydrate. We analyze its molecular behavior by applying a molecular dynamics (MD) simulation to inquire into the physicochemical properties such as diffusivity of chemical species. For extending the microscopic characteristics of constituent materials to a macroscopic diffusion behavior of the micro-inhomogeneous material we apply a homogenization analysis (HA).
From the point of view of clear demonstration of long-term safety, some of the long-lived intermediate-level wastes (ILW) are probably the most challenging of all waste types. Repository concepts for such wastes are reviewed with respect to optimization of operational procedures, post-closure performance, ease of making the safety case and costs. In particular, the advantages of designs incorporating a hydraulic cage and partitioning of wastes with different properties are discussed.
A Mg-Zn-Y alloy including a Mg12ZnY intermetallic compound exhibits excellent mechanical properties as compared to conventional magnesium alloys. The superior mechanical properties of this alloy seem to originate from the Mg12ZnY intermetallic compound; however, the mechanical properties of Mg12ZnY itself have not yet been fully investigated owing to the small size of this compound. In this study, a microfracture test was performed to investigate the fracture properties of the Mg12ZnY intermetallic compound. The material used in this test was a Mg88Zn5Y7 alloy. Micro-sized cantilever specimens composed of Mg12ZnY, with dimensions of 10 × 20 × 50 μm3, were prepared selectively isolated from the Mg88Zn5Y7 alloy using focused ion beam (FIB) machining. Notches with a width of 0.5 μm and a depth of 5 μm were also introduced into the micro-sized specimens. Microfracture tests were performed using a mechanical testing machine for microscale materials. The fracture toughness values (KQ) of Mg12ZnY were 1.2−3.0 MPam1/2. TEM observations indicated that the KQ values were dependent on the crack orientation in Mg12ZnY, with the higher KQ values correlating with cracks propagating parallel to the c-axis of Mg12ZnY. This suggests that the fracture toughness of Mg-Zn-Y alloys can be improved by controlling the orientation of the Mg12ZnY compound.
New types of multilayered photoreceptors using photosensitive a-SiC:H and a-Si:H have been investigated. The a-Si1-xCx:H was deposited at high rate of 1–6 µm/h from SiH4-C2H2 by a plasma CVD and used as a carrier generation layer (CGL) or a carrier transport layer (CTL). The type with the a-SiC:H(x=0.1) as CGL for positive charging shows higher sensitivity at λ<700 nm than the a-Si:H photoreceptors, reflecting the higher photosensitivity and wider band gap of the a-SiC:H. Furthermore, the negative charging type using the a-SiC:H(x=0.1) as CTL shows excellent sensitivity over full visible rangq compared with other positive charging types, because the transport ability of electron is superior to that of hole in both a-Si:H and a-SiC:H.
The reliability of the a-Si drum has been investigated via environmental tests and durability copy testing, and its electrophotographic properties have been confirmed to be very stable. Regarding imaging properties, a-SiC surface layer plays an important part suppressing the noise within the image. It has been discovered that the blurring of the image in high humidity after many copying cycles is caused by the deterioration of the surface layer which occurs through exposure to corona discharge. This blurring is eliminated by preventing absorption of moisture at the surface, such as heating the drum. In this manner, it has been observed that a-Si drum maintains a high quality image up to 1,000,000 copy sheets.
Highly photosensitive a-SiC:H films exhibiting ημτ-product more than 10−6 cm2/V at the band gap of 1.9 eV are prepared under the high deposition rate around 6μm/h by a plasma decomposition of SiH4-C2H2 source mixture gas at higher rf power. It is also shown that the SiH4-C2H2 gas system has a feature of the carbon incorporation into the films with the content nearly equal to that in the source mixture gas and hence is suitable for the high rate deposition process. This advantage and in addition the requirement of the higher rf power for obtaining the films with good electrical performance are discussed in terms of the dissociation reaction of the source gas and the secondary gas phase reactions in the plasma.
Seeded lateral epitaxial laser-recrystallization of silicon film on SiO2 is applied to fabricate 3-dimensional (3-D) integrations: 3-D CMOS 7-stage ring oscillators. Top p-channel Si-gate SOI MOSFET's are fabricated in the seeded recrystallized silicon directly above bottom n-channel Si-gate bulk MOSFET's with insulator in between. The recrystallized silicon at the seed region can be utilized for buried contact to interconnect bottom and top MOSFET's. At the arsenic implantation step to fabricate source and drain of the bottom MOSFET's, ions are not implanted into the seed region to prevent heavy doping and crystal disorder there; otherwise the dopant diffuses laterally and residual crystal disorder disturbs the epitaxial recrystallization. After the laser-recrystallization, the seed region is implanted with phosphorus to interconnect the top and bottom MOSFET's.
The Ar+ laser irradiation is performed with a 10 W power, a 50 μm spot size, a 13 cm/s scanning speed and a 13 μm step at 400 °C in air. Propagation delay of 460 psec is obtained for the seven stage 3-D CMOS ring oscillator at a power supply voltage of 17 V for a channel length of 3 μm and a channel width of 18 μm. In the seeded SOI films, grain boundary generation and crystal orientation can be controlled.
New DC bias method for the electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) is demonstrated, where the highly photosensitive a-Si:H film of the device grade is deposited on the dielectric substrate. The measurement of plasma parameters using a probe technique indicates that the impinging of ion H+ on the growing surface is the key to the high quality a-Si:H film and this DC bias method controls the film properties by the ion density rather than the ion energy.