Polarization structure of lidar signals reflected from ice crystal clouds

Polarization characteristics of signals of a monostatic lidar intended for sensing of homogeneous ice crystal clouds are calculated by the Monte Carlo method. Clouds are modeled as monodisperse ensembles of randomly oriented hexagonal ice crystals. The polarization state of multiply scattered lidar signal components is analyzed for different scattering orders depending on the crystal shapes and sizes as well as on the optical and geometrical conditions of observation. Light-scattering phase matrices (SPMs), calculated by the beam splitting method (BSM), are used as input data for solving the vector radiative transfer equation. The principles of the BSM method are briefly described, and the SPM components are given for hexagonal ice plates and columns of different sizes and linearly polarized incident radiation with the wavelength lambda = 0.55 microm.     

Electromagnetic properties of sea ice

Investigations of the in situ complex dielectric constant of sea ice were made using time-domain spectroscopy. It was found that (1) for sea ice with a preferred horizontal crystal c-axis alignment, the anisotropy or polarizing properties of the ice increased with depth, (2) brine inclusion conductivity increased with decreasing temperature down to about ?8°C, at which point the conductivity decreased with decreasing temperature, (3) the DC conductivity of sea ice increased with increasing brine volume, (4) the real part of the complex dielectric constant is strongly dependent upon brine volume but less dependent upon the brine inclusion orientation, (5) the imaginary part of the complex dielectric constant was strongly dependent upon brine inclusion orientation but much less dependent upon brine volume. Because the electromagnetic (EM) properties of sea ice are dependent upon the physical state of the ice, which is continually changing, it appears that only trends in the relationships between the EM properties of natural sea ice and its brine volume and brine inclusion microstructure can be established.     

Fracture toughness of sea ice

Linear elastic fracture mechanics, which has been applied to fragile substances and successfully used for studying the brittle fracture of metallic materials, was utilized to gain an understanding of the fracture phenomena of sea ice.The present paper reports the first results of investigations into the fracture-toughness value of sea ice, which was analyzed experimentally as a function of strain rate on the basis of the stress-intensity-factor concept.The fracture toughness, K_IC, of sea ice, which was measured by an in-situ three-point bending test on notched specimens, shows almost constant value if the strain rate is less then 10^?3 s^?1 and decreases with increasing strain rate if the strain rate exceeds 10^?3 s^?1. K_IC data show considerably less scatter than existing data such as the compressive, tensile and flexural strengths.It was confirmed in the present study that the linear elastic-fracture-mechanics concept is effective for analyzing the fracture phenomena of sea ice. Moreover, the K_IC value was shown to be closely related to sea-ice structures (e.g. the size of crack-like flaws such as brine cells).It is also suggested that the fracture-toughness test might prove to be a standard testing method to obtain the sea-ice strength, since once K_1C and crack-like flaw sizes are determined, the less-scattered critical-fracture stress can be calculated.     

Mapping sea ice overflood using remote sensing: Alaskan Beaufort Sea

The U.S. Department of Interior, Minerals Management Service (MMS), Alaska Outer Continental Shelf Region commissioned a study designed to map the extent of peak river overflooding onto the fast ice in the nearshore region of the Alaskan Beaufort Sea (Hearon et al., 2009). This phenomenon occurs annually during a brief period in the spring when the river stage increases rapidly as the snow pack melts, while the sea ice of the Delta front is still intact. River overflood constitutes a potential hazard to offshore oil and gas development, as it relates to facilities access, oil spill spreading, and the associated phenomenon of strudel drainage and potential seabed scouring. The overall goal of the study was to improve the knowledge of the spatial and temporal variability of overflooding and related pipeline and facility siting concerns. Historical overflood boundaries were mapped for the 13-year period from 1995 to 2007, using a combination of helicopter surveys and satellite imagery. Hazards associated with strudel scouring were assessed with strudel drain and scour databases developed for several industry projects.     

DC resistivity and thermoelectric power in Ni-Cd ferrites

The electrical resistivity and Seebeck coefficient for Ni-Cd ferrites have been studied as a function of temperature. The lattice constant of the phases have been evaluated from X-ray powder data. The thermoelectric power measurements indicate that the samples aren-type semiconductors and the conduction mechanism is interpreted on the basis of localized model of polarons.     

Thermophysical properties of ice,snow, and sea ice

The paper reviews and discusses data and information on the thermophysical properties of ice, snow, and sea ice. These properties include thermal conductivity, specific heat, density, thermal diffusivity, latent heat of fusion, thermal expansion, and absorption coefficient. The available data are shown graphically for convenience in conjunction with the recommended correlation equations.Paper presented at the Second U.S.-Japan Joint Seminar on Thermophysical Properties, June 23, 1988, Gaithersburg, Maryland, U.S.A.     

Detection of polycyclic aromatic hydrocarbons using quartz crystal microbalances

A chemically coated piezoelectric sensor has been developed for the determination of PAHs in the liquid phase. An organic monolayer attached to the surface of a gold electrode of a quartz crystal microbalance (QCM) via a covalent thiol-gold link complete with an ionically bound recognition element has been produced. This study has employed the PAH derivative 9-anthracene carboxylic acid which, once bound to the alkane thiol, functions as the recognition element. Binding of anthracene via pi-pi interaction has been observed as a frequency shift in the QCM with a detectability of the target analyte of 2 ppb and a response range of 0-50 ppb. The relative response of the sensor altered for different PAHs despite pi-pi interaction being the sole communication between recognition element and analyte. It is envisaged that such a sensor could be employed in the identification of key marker compounds and, as such, give an indication of total PAH flux in the environment.     

DC resistivity of alumina and zirconia sintered with TiC

Pure alumina and zirconia powders were sintered separately with increasing amount of TiC up to ∼ 65 vol.%, as a conducting second phase with an aim to prepare conducting structural ceramics which can be precisely machined by EDM technique. TiC did not help in sintering the parent phase but it decreased the d.c. resistivity of the composite to 1 ohm.cm at ∼ 30 vol.% loading. The conductivity is explained by the effective media and percolation theories.     

Assessment of transverse impact damage in GF/EP laminates of conductive nanoparticles using electrical resistivity tomography

GF/EP composite laminates with an epoxy matrix modified by carbon black (CB) of 2.0 wt.% and copper chloride (CC) were manufactured by the vacuum assisted resin infusion (VARI) technique. The effects of CB nanoparticles and CC on improvement in Modes I and II interlaminar fracture toughness and impact damage resistance and on the electrical conductivity of GF/EP laminate composites were investigated. Delamination growth was calibrated by in situ electrical resistance changes during interlaminar fracture tests. The relationship between growth of delamination and change in electrical resistance was characterised. A damage index based on the change in electrical resistance was introduced, and a new method of electrical resistivity tomography was developed to access transverse impact damage in GF/EP laminates based on a matrix of conductive points in both in-plane and through-thickness directions. The damage images from in-plane and through-thickness electrical resistivity tomography were finally estimated with the corresponding C-scan.     

Flexural strength and fracture toughness of sea ice

A series of mid-winter experiments were carried out on the ice in the rubble field around Tarsiut Island in the Beaufort Sea. The tests included grain structure determinations, salinity and density of the ice, small beam flexural strength and fracture toughness. Typical values for flexural strength and fracture toughness were 0.6–1.0 MPa and 100–140 kPa m^{$\text{1}\text{2}$} respectively. Both properties were dependent on brine volume and depth in the ice sheet. In comparing these results with identical tests on finegrained freshwater ice it was found that for comparable loading conditions, the strength of the sea ice was significantly lower than the strength of the freshwater ice, whereas the fracture toughness of the sea ice was higher than the fracture toughness of the freshwater ice.     

Internal structure of composite materials by using computer tomography

Results are presented of tomographic investigations of the internal structure parameters of composite materials characterized by an elementary cell density distribution over the specimen volume.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 6, pp. 1021–1027, December, 1986.     

On modelling an iceberg embedded in shore-fast sea ice

The effect of long ice-coupled waves impinging on a tabular iceberg, an ice island or a thick sea ice floe trapped within a thin veneer of shore fast sea ice of substantial extent is considered. The waves most likely originate as ocean waves in the open sea beyond the fast ice boundary, from where they propagate into the sea ice. There their character is altered because of the flexural properties of the ice. The geophysical/engineering problem posed is solved by a Green's function method that redevelops, for a different surface boundary condition, an earlier study concerned with a freely floating ice floe. Reflection and transmission coefficients for the berg are found to depend strongly on its thickness and length. Amongst other things, the work relates to the operational safety of natural and artificially thickened Arctic ice platforms located in a contiguous ice sheet.     

Control of the temperature coefficient of the DC resistivity in polymer-based composites

In this study, the roles of polymer matrices and filler additives in controlling the positive temperature coefficient (PTC)/negative temperature coefficient (NTC) behavior of DC resistivity at high temperature for semicrystalline ethylene vinyl acetate copolymer, amorphous acrylonitrile butadiene copolymer, and their blend composites filled with different carbon fillers like Conductex carbon black, Printex carbon black, and short carbon fiber have been investigated. It is seen that the PTC/NTC behavior of resistivity depends on the characteristics of both polymer matrices and filler additives. The anomaly in the results are due to polymer crystallinity, shape and size of fillers, and their thermal expansion coefficient, that play major role in controlling the PTC/NTC of resistivity at high temperature for the composites. Finally, reproducibility of composite resistivity has been evaluated with their some proposed practical applications. These composites can be used as both PTC and NTC thermistors.     

Detection of biotin in individual sea urchin oocytes using a bioluminescence binding assay

The ability to detect biomolecules in single cells is important in order to fully understand the processes by which many biochemical events occur. To that end, we have developed a bioluminescence binding assay capable of measuring the intracellular biotin content of individual cells. The assay depends on competition between an aequorin-biotin conjugate (AEQ-biotin) and free biotin within the oocytes for binding sites on the protein avidin. The assay is performed by microinjecting each component into the oocytes and following the resulting bioluminescence within the oocyte upon triggering of aequorin. Results obtained using sea urchin oocytes show that the assay performed within the cells behaves in a manner consistent with assay theory. Using the assay, the individual biotin content of the oocytes is an average of approximately 20 amol. To our knowledge, this is the first reported multicomponent binding assay to be performed inside an intact single cell.     

Three-dimensional structure of helical and zigzagged nanowires using electron tomography

Electron tomography and high-resolution transmission electron microscopy were used to characterize the unique three-dimensional structures of helical or zigzagged GaN, ZnGa2O4, and Zn2SnO4 nanowires. The GaN nanowires adopt a helical structure that consists of six equivalent <011> growth directions with the axial [0001] direction. We also confirmed that the ZnGa2O4 nanosprings have four equivalent <011> growth directions with the [001] axial direction. The zigzagged Zn2SnO4 nanowires consisted of linked rhombohedrons having the side edges matched to the <110> direction and the [111] axial direction.     

应用chirp声呐探测海冰的试验研究

应用声呐技术可以实现在水下连续监测海冰的厚度和速度等参数,为海洋研究和工程提供重要的数据.采用chirp 信号的声呐能有效探测冰水界面,试验表明声呐测距的精度优于1cm,能够满足探测渤海海冰的指标要求.     

Laboratory studies of angle- and polarization-dependent light scattering in sea ice

The angle- and polarization-dependent light scattering were measured for oriented first-year and multiyear sea ice taken from the Chukchi Sea near Pt. Barrow, Alaska. The entire Mueller matrix for these samples was determined at 532 nm. Mueller matrices were also determined for artificially grown saline ice samples and melted samples of the respective ice types. Phase functions for thin-slab samples are qualitatively consistent with calculations for scattering from brine inclusions in a solid ice medium and depend strongly on the shape of the scattering sample. Small orientation-dependent effects are observed for scattering from oriented sea ice. A simple model is used to describe qualitatively some features of the measured sea ice Mueller matrices. This model combines the effects of scattering from spherical inhomogeneities and the intrinsic birefringence of pure water ice. A set of Mueller matrix inequalities is presented and used to obtain physical insight into the measurement results.     

Measurement of shear strength of granular/discontinuous-columnar sea ice

A method of performing shear tests using asymmetrical four-point bending was applied to sea ice. The method leads to less uncertainty in the stress field created. The tests were performed on specimens of granular/discontinuous-columnar ice obtained from the Beaufort Sea. For a test temperature of $\text{?13 ± 2°C}$ and salinity of 4.2%, the average shear strength was 550 kPa with a standard deviation of 120 kPa.