Dependence Of Penetration Depth Research Articles

Anomalously strong size effect on thermal conductivity of diamond microparticles

Diamond has the known highest thermal conductivity of around 2000 W m−1 K−1 and is, therefore, widely used for heat dissipation. In practical applications, synthetic diamond microparticles are usually assumed to have similar thermal conductivity to that of bulk diamond because the particle size is larger than the theoretical phonon mean free path, so that boundary scattering of heat-carrying phonons is absent. In this report, we find that the thermal conductivity of diamond microparticles anomalously depends on their sizes. The thermal conductivity of diamond microparticles increases from 400 to 2000 W m−1 K−1 with the size growing from 20 to 300 μm. We attribute the abnormally strong size effect to the long-range defects during the growth process based on analysis of point defects, dislocations, and thermal penetration depth dependence of thermal conductivity. Our results play a vital role in the design of diamond composites and in the improvement of the thermal conductivity of synthetic diamonds.

THE PENETRATION DEPTH OF H3S SUPERCONDUCTOR BY SEMICLASSICAL APPROACH

The penetration depth is a magnetic field mechanism by which an external magnetic field penetrates into superconductors’ surfaces and is related to the Meissner effect. The penetration depth property was studied by the semiclassical approach to identify other properties of superconductors. In this study, we investigated the penetration depth of the H3S superconductor under external pressure. The H3S superconductor is high Tc, s-wave isotropic, and high pressure prepared superconductors. We derive an analytical equation for the near-zero temperature penetration depth with pressure effect parameters. The derived equations were then numerically calculated and predicted the experimental data on H­3S superconductor penetration depth. We discovered that the temperature dependent penetration depth under pressure of H­3S superconductor is reasonable at Tc(χ = 473, ε0 = 91,Qp = 0.1) = 200.832 K. , as well as is the influence of the directly parameter on Tc(χ,ε0,Qp), Δ(0,χ,ε0,Qp), and λ(T,χ,ε0,Qp)/λ(0,χ,ε0,Qp), with Qp>0.1 does not corresponding theory

Photoswitchable Liquid‐to‐Solid Transition of Azobenzene‐Decorated Polysiloxanes

AbstractHaving external control over fundamental properties of polymers, such as their physical state, is a crucial yet challenging design criterion for smart materials. Liquifying polymers through photochemical events has significantly advanced various research lines. However, the opposite process of solidifying a polymer that is intrinsically in a liquid state reversibly with light is unattained. Herein, the light‐controlled liquid‐to‐solid transition of polysiloxanes is reported, which are decorated with a small number of azobenzene‐functionalized ureidopyrimidinone (Azo‐UPy) pendants. The UPy moieties toggle between intra‐ and intermolecular hydrogen bonding via trans→cis photoisomerization of the azobenzene. This transformation on the molecular level leads to the formation of strong supramolecular cross‐links, which, in turn, results in the macroscopic solidification of the material. The photoswitching event enables the post‐synthetic tailoring of the polymers’ mechanical properties, thus providing an alternative to the addition of plasticizers or hardeners. Moreover, the adhesion strength of the photochromic material increases by a factor of 6 upon exposure to UV light. In situ illumination during rheological measurements reveals the delicate interplay between wavelength dependent penetration depth and photoswitching efficiency. This conceptually new (de)bonding on demand strategy paves the way for creating light‐responsive materials with exciting applications in temporal adhesion, recycling, lithography, and material processing.

ELECTROMAGNETIC SHIELDING AS A WAY OF PROTECTING INFORMATION FROM ITS LEAKAGE BY TECHNICAL CHANNELS

In this paper, investigated one of the way of protecting information from its leakages through the technical channels, such as shielding. The first part of the work mainly consider the theoretical principles of shielding, such as definition and process of shielding, its types, main task of the shield, highlighted the concept of shielding efficiency, presented dependence for calculating the efficiency of electromagnetic shield, provided shields classification according to three characteristics: type of field interference, design and material, shield forms, for each of them presented dependence for calculating shielding efficiency of magnetic and electromagnetic field, presented dependence for calculating depth of penetration, as a value that characterizes shielding effect of shielding material. The second part of work consider separate types of shielding such as shielding of the electric field, dependence for calculating its effectiveness, presented main requirements for electric shields, considered the principles of shielding for low-frequency and high-frequency magnetic fields, dependences for calculating its shielding efficiency, presented main requirements for magnetostatic shields, considered shielding of electromagnetic fields, provided main mechanisms of protection against electromagnetic interference, presented dependence for calculating shielding efficiency of electromagnetic field. In the third part of the work calculated shielding efficiency and penetration depth of electromagnetic field for magnetic and non-magnetic materials at given frequencies with different conductivity and different thickness of shield walls, provided graphs of frequency dependence of shielding efficiency at different thickness of the shield walls, shown graph of frequency dependence of penetration depth for different materials, made conclusions and provided recommendations regarding selection of shielding materials at high and low frequencies, presented shielding materials for permanent magnetic field and high-frequency electromagnetic field.

ZnO Nanorod FET Biosensors With Enhanced Sensing Performance: Design Issues for Rational Geometry Selection

ZnO nanorod field effect transistor (FET) biosensors enable ultrasensitive, rapid and label free detection of biomolecules. However, the fabrication of these nanorods without any design guideline results in poor signal to noise ratio, limiting their commercial deployment. The various forces operating within the spacing of the nanorods may prevent complete penetration of the liquid for large aspect ratios and hence mere enhancement of the geometric surface area may not yield the optimum output which indicates the intricacies involved in the design of such sensors. The present work consistently models the analyte and the device regions of the sensor by transforming the understanding of the transduction mechanism of biomolecule capture in nanowire FETs into nanorod FET structure and integrating the spacing dependent liquid penetration depth along with the various temporal fluctuations of the sensor to enhance the signal to noise ratio ( SNR ) and lower the molecule detection limit(MDL). Simulation results, verified experimentally for prostate specific antigen (PSA) shows that the optimal geometry does not correspond to the maximum surface area. Instead it is dependent on the developed surface potentials after receptor immobilization and ligand capture which vary non-monotonically with nanorod radius due to nonlinear dependence of buffer penetration for high aspect ratios. This approach has significantly increased the SNR leading to reliable quantification of PSA in human serum with MDL reduced by almost three orders of magnitude in comparison to recent reports. In summary, this work brings the ZnO nanorod sensors a step closer towards practical application for early diagnosis.

Anisotropy of field dependent penetration depth and the Sommerfeld coefficient in the pnictide superconductor

The modified phenomenological Ginzburg-Landau (MPGL) theory used to observe the anisotropy of the penetration depth as well as the Sommerfeld coefficient in the pnictide superconductor of the composition Ba0.6K0.4Fe2As2. The values of such thermodynamic parameters have been theoretically calculated and presented in this context. The qualitative, as well as quantitative results of such anisotropies indicate the successful accomplishment of this theory to the superconducting system of Ba1-xKxFe2As2composition.

Research on Workability of Tool Cutters Working under Conditions of Shockless Loads and Friction

The paper deals with hard cutters of drill bits for drilling rocks. The research on geometry of hard alloy and steel cutters of bits that work either under conditions of shockless loads was carried out in this work. The rationale of tungsten carbide and cobalt composition according to their hardness and robustness is provided. Different alloys were suggested to be used for tools working either under conditions of shockless loads or under shock loads for drilling rocks of high hardness. The rock deformation process was identified to occur by cutting and shearing forces. The highest influence on the cutting process is exerted by the acuity angle and back rake angle. Peculiarities of work of cutters with positive, negative and neutral back rake angles were determined as part of the main research. The dependence of penetration depth on the back rake angle of the cutter was obtained. Indicators of wearing identified in the research are including the type and properties of interacting surfaces characterized by the roughness of cutting bit surface, the hardness of materials in contact zone, friction mode that depends on unit pressure, movement rate, the nature of load application, and the rate of interaction of working parts of bit.

Power-Law Temperature Dependence of the Penetration Depth in a Topological Superconductor Due to Surface States.

We study the temperature dependence of the magnetic penetration depth in a 3D topological superconductor (TSC), incorporating the paramagnetic current due to the surface states. A TSC is predicted to host a gapless 2D surface Majorana fluid. In addition to the bulk-dominated London response, we identify a T^{3} power-law-in-temperature contribution from the surface, valid in the low-temperature limit. Our system is fully gapped in the bulk, and should be compared to bulk nodal superconductivity, which also exhibits power-law behavior. Power-law temperature dependence of the penetration depth can be one indicator of topological superconductivity.

Determination and validation of photon energy absorption buildup factor in human tissues using Monte Carlo simulation

In this study, the Energy Absorption Buildup Factor (EABF) of different tissue equivalent materials have been calculated using the Monte Carlo code MCNP5. The results of MCNP5 calculations are validated against the results obtained using the Geometric Progression (G-P) fitting method. The energy range for the gamma rays was 0.1–15 MeV and penetration depth was up to 20 mfps. Chemical compositions for different tissue materials are implemented into the MCNP5 to estimate the buildup factor for each tissue type. Energy and penetration depth dependence of the EABF are also analyzed. The results show that the adipose tissue has the largest buildup factor while the bone tissue has the lowest. Comparison of MCNP5 results with the G-P fitting method demonstrated a good agreement, with 90% of all MCNP5 EABF calculated values deviating less than 5% from the G-P. The average deviation for all EABF values is 2.3%. The results from this study can be used for radiotherapy treatment, radiation dosimetry and for medical diagnostics based on the practical thicknesses and energy ranges investigated.

Evidence for unconventional superconductivity in half-Heusler YPdBi and TbPdBi compounds revealed by London penetration depth measurements

The half-Heusler compounds YPdBi and TbPdBi, while having similar band structure, exhibit different magnetic properties. YPdBi is a diamagnet, while TbPdBi shows antiferromagnetic order below 5.5 K. Both are superconductors with T${_c}\approx$1 K for YPdBi and T${_c}\approx$1.75 K for TbPdBi. Such a contrast in properties between these two compounds opens a question about the effects of band structure or magnetic correlations on superconductivity. Using the combination of a tunnel diode oscillator (TDO) and a commercial dilution refrigerator, we measured temperature dependent magnetic penetration depth $\Delta\lambda(T)$ in single crystals of YPdBi and TbPdBi, down to temperatures as low as 0.1K. We found that penetration depths of both compounds do not show exponential temperature dependence and saturation at low temperatures, as expected for conventional BCS superconductors. Instead, in both compounds, the penetration depth can be described by a power law $\Delta\lambda(T) = A\times T^{n}$. The coefficient A was found to be about 50$\%$ smaller in TbPdBi, but the exponents are very similar, $n = 2.76\pm 0.04$ in YPdBi and $n = 2.6\pm 0.3$ in TbPdBi, respectively. Our results suggest unconventional superconductivity in both YPdBi and TbPdBi.

Significant Structural Distortion in the Surface Region of 4H-SiC Induced by Thermal Oxidation and Recovered by Ar Annealing

The impacts of O2-oxidation and Ar-annealing processes on the local lattice distortion at surface of thermally-oxidized 4H-SiC (0001) were investigated by using in-plane XRD. The surface oxidation induces a significant increase of the lattice constant, whereas Ar-annealing results in a gradual relaxation of it. From the x-ray penetration depth dependence of the observed lattice constant, those anomalous changes of lattice constants occur only in the surface region of SiC substrate.

Indentation size and loading strain rate dependent creep deformation of nanocrystalline Mo

The creep behavior of nanocrystalline body-centered cubic Mo thin films was evaluated using nanoindentation testing. The creep rate and the corresponding strain rate sensitivity (m) were found to be strongly dependent upon indentation size and loading strain rate (LSR). Other than the mechanism of diffusion along indenter tip-sample interface previously proposed for face-centered cubic metals and metallic glasses, alternative mechanisms involving surface effect enhanced screw dislocation activities, inverse indentation size effect of hardness and LSR dependent microstructural and stress states, were proposed to interpret the observed dependence of penetration depth and LSR of m.

L-Band InSAR Penetration Depth Experiment, North Slope Alaska

Since the first spacecraft-based synthetic aperture radar (SAR) mission NASA’s SEASAT in 1978 radars have been flown in Low Earth Orbit (LEO) by other national space agencies including the Canadian Space Agency, European Space Agency, India Space Research Organization and the Japanese Aerospace Exploration Agency. Improvements in electronics, miniaturization and production have allowed for the deployment of SAR systems on aircraft for usage in agriculture, hazards assessment, land-use management and planning, meteorology, oceanography and surveillance. LEO SAR systems still provide a range of needful and timely information on large and small-scale weather conditions like those found across the Arctic where ground-base weather radars currently provide limited coverage. For investigators of solid-earth deformation attention must be given to the atmosphere on Interferometric SAR (InSAR) by aircraft and spacecraft multi-pass operations. Because radar has the capability to penetrate earth materials at frequencies from the P- to X-band attention must be given to the frequency dependent penetration depth and volume scattering. This is the focus of our new research project: to test the penetration depth of L-band SAR/InSAR by aircraft and spacecraft systems at a test site in Arctic Alaska using multi-frequency analysis and progressive burial of radar mesh-reflectors at measured depths below tundra while monitoring environmental conditions. Knowledge of the L-band penetration depth on lowland Arctic tundra is necessary to constrain analysis of carbon mass balance and hazardous conditions arising from permafrost degradation and thaw, surface heave and subsidence and thermokarst formation at local and regional scales.

Mathematical Modeling of the Concentrated Energy Flow Effect on Metallic Materials

Numerous processes take place in materials under the action of concentrated energy flows. The most important ones include heating together with the temperature misdistribution throughout the depth, probable vaporization on the surface layer, melting to a definite depth, and hydrodynamic flotation; generation of thermo-elastic waves; dissolution of heterogeneous matrix particles; and formation of nanolayers. The heat-based model is presented in an enthalpy statement involving changes in the boundary conditions, which makes it possible to consider melting and vaporization on the material surface. As a result, a linear dependence of penetration depth vs. energy density has been derived. The model of thermo-elastic wave generation is based on the system of equations on the uncoupled one-dimensional problem of dynamic thermo-elasticity for a layer with the finite thickness. This problem was solved analytically by the symbolic method. It has been revealed for the first time that the generated stress pulse comprises tension and compression zones, which are caused by increases and decreases in temperature on the boundary. The dissolution of alloying elements is modeled on the example of a titanium-carbon system in the process of electron beam action. The mathematical model is proposed to describe it, and a procedure is suggested to solve the problem of carbon distribution in titanium carbide and liquid titanium-carbide solution in terms of the state diagram and temperature changes caused by phase transitions. Carbon concentration vs. spatial values were calculated for various points of time at diverse initial temperatures of the cell. The dependence of carbon particle dissolution on initial temperature and radius of the particle were derived. A hydrodynamic model based on the evolution of Kelvin-Helmholtz instability in shear viscous flows has been proposed to specify the formation of nanostructures in materials subjected to the action of concentrated energy flows. It has been pointed out for the first time that, for certain parameters of the problem, that there are two micro- and nanoscale peaks in the relation of the decrement to the wavelength of the interface disturbance.

Critical Current and Flux Pinning Characteristics in Sr0.6K0.4Fe2As2 Superconducting Tapes

Since novel iron-based pnictide of Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconductor was discovered, the applications on high magnetic field and large current transportation are highly expected due to its low cost and unique superconductivity such as low anisotropy, relatively high critical current density, and critical temperature. Recently, we have successfully developed the Fe-clad superconducting Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> tape with the critical temperature of 32.5 K and fairly high critical current density of 1.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> A/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 10 T and 4.2 K. Since the critical current density is considered as one of the most important factors for applications of superconducting materials, detailed investigation on the critical current characteristic and flux pinning mechanism in the supposed operation temperature range is necessary. In this paper, the critical current densities in the temperature range of about 20 K-30 K and at the magnetic field of up to 7 T were measured by using an inductive method (Campbell's method). It turned out that the critical current density of the tape is fairly high around 20 K. In this paper, basing on the experimental results of the penetrating ac magnetic flux profile and the feature of ac magnetic field dependence of penetration depth, the flux pinning mechanism of the sample was discussed.

Dimensional analysis and extended hydrodynamic theory applied to long-rod penetration of ceramics

Abstract Principles of dimensional analysis are applied in a new interpretation of penetration of ceramic targets subjected to hypervelocity impact. The analysis results in a power series representation – in terms of inverse velocity – of normalized depth of penetration that reduces to the hydrodynamic solution at high impact velocities. Specifically considered are test data from four literature sources involving penetration of confined thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron carbide. Test data can be accurately represented by the linear form of the power series, whereby the same value of a single fitting parameter applies remarkably well for all four ceramics. Comparison of the present model with others in the literature (e.g., Tate's theory) demonstrates a target resistance stress that depends on impact velocity, linearly in the limiting case. Comparison of the present analysis with recent research involving penetration of thin ceramic tiles at lower typical impact velocities confirms the importance of target properties related to fracture and shear strength at the Hugoniot Elastic Limit (HEL) only in the latter. In contrast, in the former (i.e., hypervelocity and thick target) experiments, the current analysis demonstrates dominant dependence of penetration depth only by target mass density. Such comparisons suggest transitions from microstructure-controlled to density-controlled penetration resistance with increasing impact velocity and ceramic target thickness.

Neutron shielding qualities and gamma ray buildup factors of concretes containing limonite ore

Neutron dose transmissions for fast neutrons produced by 5.486MeV alpha particles on beryllium are measured in concrete samples with and without limonite ore to investigate their neutron shielding qualities. Using measured values, macroscopic removal cross-sections (ΣR, cm−1) have been determined experimentally and also ΣRvalues have been calculated theoretically using the elemental composition of the concrete mixes. The best neutron shielding property of concrete sample containing 100% limonite ore (FCL: fine and coarse limonite) was found. Additionally, energy absorption buildup factor (EABF) and exposure buildup factor (EBF) of concrete sample were calculated using the five-parameter Geometric Progression (G-P) approximation in the energy range of 0.015–15MeV for penetration depths up to 40 mean free path (mfp). The incident photon energy and penetration depth dependence of buildup factors were examined. Finally, we observed that concrete samples have maximum values of buildup factors in the intermediate energy region around 0.1–0.3MeV. FCL has the minimum values of both of the buildup factors. FCL has the excellent gamma shielding properties compared to the concrete samples.

Using the inertia of spacecraft during landing to penetrate regoliths of the Solar System

The high inertia, i.e. high mass and low speed, of a landing spacecraft has the potential to drive a penetrometer into the subsurface without the need for a dedicated deployment mechanism, e.g., during Huygens landing on Titan. Such a method could complement focused subsurface exploration missions, particularly in the low gravity environments of comets and asteroids, as it is conducive to conducting surveys and to the deployment of sensor networks. We make full-scale laboratory simulations of a landing spacecraft with a penetrometer attached to its base plate. The tip design is based on that used in terrestrial Cone Penetration Testing (CPT) with a large enough shaft diameter to house instruments for analysing pristine subsurface material. Penetrometer measurements are made in a variety of regolith analogue materials and target compaction states. For comparison a copy of the ACC-E penetrometer from the Huygens mission to Titan is used. A test rig at the Open University is used and is operated over a range of speeds from 0.9 to 3ms−1 and under two gravitational accelerations.The penetrometer was found to be sensitive to the target’s compaction state with a high degree of repeatability. The penetrometer measurements also produced unique pressure profile shapes for each material. Measurements in limestone powder produced an exponential increase in pressure with depth possibly due to increasing compaction with depth. Measurements in sand produced an almost linear increase in pressure with depth. Iron powder produced significantly higher pressures than sand presumably due to the rough surface of the grains increasing the grain-grain friction. Impacts into foamglas produced with both ACC-E and the large penetrometer produced an initial increase in pressure followed by a leveling off as expected in a consolidated material. Measurements in sand suggest that the pressure on the tip is not significantly dependent on speed over the range tested, which suggests bearing strength equations could be applied to impact penetrometry in sand-like regoliths.In terms of performance we find the inertia of a landing spacecraft, with a mass of 100kg, is adequate to penetrate regoliths expected on the surface of Solar System bodies. Limestone powder, an analogue for a dusty surface, offered very little resistance allowing full penetration of the target container. Both iron powder, representing a stronger coarse grained regolith, and foamglas, representing a consolidated comet crust, could be penetrated to similar depths of around two to three tip diameters. Speed tests suggest a linear dependence of penetration depth on impact speed.

Superconducting and magnetic properties ofSr3Ir4Sn13

Magnetization and muon spin relaxation or rotation (muSR) measurements have been performed to study the superconducting and magnetic properties of Sr3Ir4Sn13. From magnetization measurements the lower and upper critical fields of Sr3Ir4Sn13 are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field muSR data show no sign of any magnetic ordering or weak magnetism in Sr3Ir4Sn13. Transverse-field muSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth. The dependence of penetration depth with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr3Ir4Sn13 with a gap value of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature is 291(3) nm. The gap to Tc ratio is 2.1(1), indicates that Sr3Ir4Sn13 should be considered as a strong-coupling superconductor.

Grain size dependence of penetration depth of hydrogen injection into polycrystalline graphite by molecular simulation

Many different carbon materials are developed for diverse applications for industrial and scientific uses. It is known that the amount of hydrogen retained in carbon materials under plasma irradiation strongly depends on the structural characteristics of the material, such as grain size. To clarify the cause of the difference in the amount of hydrogen retained in different carbon materials, hydrogen atom injection into polycrystalline graphite is investigated on the atomic scale by a hybrid simulation technique consisting of binary-collision-approximation-based simulation and molecular dynamics simulation. Then, the incident energy and grain size dependences of the penetration profile of incident hydrogen atoms are carefully investigated.