Core Width Research Articles

Atomistic-to-continuum description of edge dislocation core: Unification of the Peierls-Nabarro model with linear elasticity

Conventional linear elasticity theory predicts the strain fields of a dislocation core to diverge, whereas it is known from atomistic simulations that core strains should remain finite. We present an analytical solution to a generalized, variational Peierls-Nabarro model of edge dislocation displacement fields that features a finite core width and correct isotropic elastic behavior at large distances away from the core. We derive an analytical expression for the dislocation core radius, representing the convergence radius of the linear elasticity far-field expansion. The strain fields are in qualitative agreement with atomistic simulations of $\frac{1}{2}[111](10\overline{1})$ edge dislocations in bcc tungsten and iron. The treatment is based on the multistring Frenkel-Kontorova model that we reformulate as a generalized Peierls-Nabarro model using the principle of least action.

Studying the [O iii]λ5007 Å emission-line width in a sample of ∼ 80 local active galaxies: a surrogate for σ⋆?

For a sample of $\sim$80 local ($0.02 \leq z \leq 0.1$) Seyfert-1 galaxies with high-quality long-slit Keck spectra and spatially-resolved stellar-velocity dispersion ($\sigma_{\star}$) measurements, we study the profile of the [OIII]$\lambda$5007A emission line to test the validity of using its width as a surrogate for $\sigma_{\star}$. Such an approach has often been used in the literature, since it is difficult to measure $\sigma_{\star}$ for type-1 active galactic nuclei (AGNs) due to the AGN continuum outshining the stellar-absorption lines. Fitting the [OIII] line with a single Gaussian or Gauss-Hermite polynomials overestimates $\sigma_{\star}$ by 50-100%. When line asymmetries from non-gravitational gas motion are excluded in a double Gaussian fit, the average ratio between the core [OIII] width ($\sigma_{\rm {[OIII],D}}$) and $\sigma_{\star}$ is $\sim$1, but with individual data points off by up to a factor of two. The resulting black-hole-mass-$\sigma_{\rm {[OIII],D}}$ relation scatters around that of quiescent galaxies and reverberation-mapped AGNs. However, a direct comparison between $\sigma_{\star}$ and $\sigma_{\rm {[OIII],D}}$ shows no close correlation, only that both quantities have the same range, average and standard deviation, probably because they feel the same gravitational potential. The large scatter is likely due to the fact that line profiles are a luminosity-weighted average, dependent on the light distribution and underlying kinematic field. Within the range probed by our sample (80-260 km s$^{-1}$), our results strongly caution against the use of [OIII] width as a surrogate for $\sigma_{\star}$ on an individual basis. Even though our sample consists of radio-quiet AGNs, FIRST radio-detected objects have, on average, a $\sim$10% larger [OIII] core width.

Mitigation of Gap Losses in Nanocrystalline Tape-Wound Cores

A split-core technique is proposed to mitigate the gap losses in high-frequency nanocrystalline cores, which enables significant size reductions in thermally limited designs. Finite element analysis is used to examine the gap loss dependence on core width D revealing a nonlinear relationship of the form loss ∝ $D^{\alpha }$ . α is approximately constant for frequencies of 10–200 kHz over the range of core widths typically used in power electronics, but α increases with gap length. Splitting the core into a number of subcores can therefore provide significant reductions in gap loss, especially with larger gap lengths. The results from a 300-A (peak), 200-A (continuous) inductor show that with three subcores and a gap length of 4 mm, the gap losses are reduced by 50%, and the hot-spot temperature is reduced by 24.5 °C. Using the technique it is estimated that the original inductor weight could be reduced by 40% with four split cores, making a significant impact on converter power density.

Three-dimensional stability of leapfrogging quantum vortex rings

It is shown by numerical simulations within a regularized Biot-Savart law that dynamical systems of two or three leapfrogging coaxial quantum vortex rings having a core width ξ and initially placed near a torus of radii R0 and r0 can be three-dimensionally (quasi-)stable in some regions of parameters Λ = ln(R0/ξ) and W = r0/R0. At fixed Λ, stable bands on W are intervals between non-overlapping main parametric resonances for different (integer) azimuthal wave numbers m. The stable intervals are most wide (ΔW ∼ 0.01–0.05) between m-pairs (1, 2) and (2, 3) at Λ ≈ 4–12, thus corresponding to micro/mesoscopic sizes of vortex rings in the case of superfluid 4He. With four and more rings, at least for W > 0.1, resonances overlap for all Λ and no stable domains exist.

Structural Characterization and Analysis of Human Immunodeficiency Virus Encapsulating Quantum Dots.

Virus internal labeling by inorganic nanoparticle is a suitable technique for single virus imaging. However, it is unknown that the effect of the internal inorganic nanoparticle on morphology and structure of viral core in mature enveloped Human immunodeficiency virus 1 (HIV-1). Also, the analysis of intact HIV-1 particles and virus-inorganic nanoparticle hybrids is almost impossible with conventional negative staining because HIV-1 is inherently fragile and unstable. Herein, we carried out morphological and structural analysis of a newly constructed quantum dot (QD)-encapsulated infectious HIV-1 particle by using an optimized procedure for the electron microscopic analysis of negatively stained HIV-1 particles. The virus fixation and staining conditions were optimized to ensure the integrity of HIV-1, allowing the ready access to structural information on the viral envelope and core. Morphological and structural analysis by optimized TEM provide key information about viruses, viral core and nanoparticles, which indicates that the encapsulation of quantum dots had no effect on the morphology or mean size of the viral particle, or on the shape, length, width, or angle of the HIV-1 core.

Stress-Strain State in the Deformation of the Rogun Dam During the Construction Period

The stress-strain state and stability of the Rogun Dam are investigated under the action of static loads, taking into account the time and stage-by-stage construction in conditions of flat and spatial work. Three variants of the core width at the base of the dam are considered. Comparison of the options showed that the configuration of the canyon has significant effect on the efficiency.

Low-loss and low-crosstalk multimode waveguide bend on silicon.

A low-loss and low-crosstalk multimode waveguide bend is proposed and demonstrated for mode-division-multiplexed optical interconnects. The proposed 90°-bend is composed of two identical 45°-bends, which are defined as modified Euler curves. For the designed 90° Euler-bend with a core width of 2.36 μm for supporting four TM-polarization modes, it is allowed to achieve an effective radius as small as 45 μm, which is about 1/4 of the radius (~175 μm) for a regular 90° arc-bend. In theory, this proposed 90° Euler-bend has very low excess losses (<0.1 dB) and very low inter-mode crosstalks (<-25 dB) over a broad wavelength-band. A silicon photonic integrated circuit is designed, fabricated and characterized by integrating a pair of mode (de)multiplexers and a multimode bus waveguide with a Euler S-bend consisting of two cascaded 90° Euler-bends. The measurement results show that the fabricated Euler S-bend has low excess losses of <0.5 dB and low inter-mode crosstalks of <-20 dB over a broad band from 1520 nm to 1610 nm for all the 4 mode-channels of TM polarization.

Pedestrian-level wind conditions in the space underneath lift-up buildings

Lift-up buildings are advantageous in improving the wind circulation in a congested and compact city. However, the wind conditions in the void underneath a lift-up building, also known as the lift-up area, are vital for wind comfort of occupants of lift-up buildings. This study tested 28 lift-up buildings in a boundary layer wind tunnel to assess the influence of key design parameters; height and width of the main structure, and height, width, depth, and the shape of the central core on the wind conditions in the lift-up area. The results of the analyses show a significant influence of building height on the magnitude of wind speeds in the lift-up area while the width of the central core controls the area with low wind speeds. Tall buildings with short lift-up cores have small areas with acceptable pedestrian wind comfort, which can be increased by adopting corner modifications for the central core. The area of acceptable pedestrian wind comfort increases in oblique wind directions as the areas of high (>3.5 m s−1) and low (<1.5 m s−1) wind speeds are decreased. Finally, a non-linear second-order multivariable regression model is developed to predict pedestrian wind comfort in the lift-up area.

Polarization-insensitive 2 × 2 thermo-optic Mach-Zehnder switch on silicon.

A polarization-insensitive 2×2 thermo-optic Mach-Zehnder switch (MZS) on silicon is proposed and demonstrated experimentally by utilizing silicon-on-insulator (SOI) nanophotonic waveguides with a 340-nm-thick silicon core layer. The present MZS consists of two 2×2 3dB multimode interference (MMI) couplers, which are designed to be polarization-insensitive by choosing the core width optimally. Meanwhile, the MZS arms are designed with square SOI nanophotonic waveguides with a cross section of 340 nm×340 nm in order to achieve polarization-insensitive phase shift. The fabricated silicon MZS has an excess loss of 1∼4 dB and an extinction ratio of >20 dB in the C-band (1530∼1565 nm) for both TM and TE polarizations.

An Iwasawa–Taniguchi effect for Compton-thick active galactic nuclei

We present the first study of an Iwasawa-Taniguchi/X-ray Baldwin effect for Compton-thick active galactic nuclei (AGN). We report a statistically significant anti-correlation between the rest-frame equivalent width (EW) of the narrow core of the neutral Fe K$\alpha$ fluorescence emission line, ubiquitously observed in the reflection spectra of obscured AGN, and the mid-infrared 12$\,\mu$m continuum luminosity (taken as a proxy for the bolometric AGN luminosity). Our sample consists of 72 Compton-thick AGN selected from pointed and deep-field observations covering a redshift range of $z\sim0.0014-3.7$. We employ a Monte Carlo-based fitting method, which returns a Spearman's Rank correlation coefficient of $\rho=-0.28\pm0.12$, significant to 98.7% confidence. The best fit found is ${\rm log}({\rm EW}_{{\rm Fe\,K}\alpha})\,\propto\,-0.08\pm0.04\,{\rm log}(L_{12\,\mu{\rm m}})$, which is consistent with multiple studies of the X-ray Baldwin effect for unobscured and mildly obscured AGN. This is an unexpected result, as the Fe K$\alpha$ line is conventionally thought to originate from the same region as the underlying reflection continuum, which together constitute the reflection spectrum. We discuss the implications this could have if confirmed on larger samples, including a systematic underestimation of the line of sight X-ray obscuring column density and hence the intrinsic luminosities and growth rates for the most luminous AGN.

Influence of Compaction During Reaction Heat Treatment on the Interstrand Contact Resistances of Nb 3Sn Rutherford Cables for Accelerator Magnets

The high field superconducting magnets required for ongoing and planned upgrades to the Large Hadron Collider (LHC) will be wound with Nb3Sn Rutherford cables for which reason studies of Nb3Sn strand, cable, and magnet properties will continue to be needed. Of particular importance is field quality. The amplitudes of multipoles in the bore fields of dipole and quadrupole magnets, induced by ramp-rate-dependent coupling currents, are under the control of the interstrand contact resistances—crossing-strand, $R_{c}$ , adjacent strand, $R_{a}$ , or a combination of them, $R_{{\text{eff}}}$ . Although two decades ago it was agreed that for the LHC $R_{c}$ should be in the range 10–30 μ Ω, more recent measurements of LHC quadrupoles have revealed $R_{c}$ values ranging from 95 to 230 μ Ω. This paper discusses ways in which these values can be achieved. In a heavily compacted cable $R_{{\text{eff}}}$ can be tuned to some predictable value by varying the width of an included stainless steel (effectively “insulating”) core. But cables are no longer heavily compacted with the result that the crossing strands of the impregnated cable are separated by a thick epoxy layer that behaves like an insulating core. If a stainless steel core is actually present, $R_{{\text{eff}}}$ must be independent of core width. Since there is no guarantee that a fixed predetermined amount of interlayer separation could be reproduced from winding to winding it would be advisable to include a full width core.

Long-Lived Quantum Vortex Knots

Dynamics of simplest quantum vortex knots of torus type in a superfluid at zero temperature has been simulated within a regularized Biot-Savart law (the torus radii $R_0$ and $r_0$ for initial vortex configuration were large in comparison with a vortex core width $\xi$). Computations of evolution times of knots until their significant deformation were carried out with a small step on parameter $B_0=r_0/R_0$ for different values of parameter $\Lambda=\log(R_0/\xi)$. It has been found that at $\Lambda\gtrsim 3$, bands of quasi-stability appear in a region of $B_0\lesssim 0.2$, which correspond to long knot lifetimes and to very large traveling distances --- up to several hundreds of $R_0$. This result is new and quite unexpected, because previously it was believed that maximal lifetime of torus knots until reconnection does not exceed several typical periods. The opening of quasi-stable 'windows' at increasing $\Lambda$ is due to narrowing main parametric resonances of the dynamical system on parameter $B_0$.

THz wavefront manipulation based on metal waveguides

In this paper, two waveguiding structures for arbitrary wavefront manipulation in the terahertz spectral region were proposed, designed and characterized. The first structure consists of parallel stack copper plates forming an array of parallel-plate waveguides (PPWGs). The second structure is three-dimensional metal rectangular waveguides array. The phase delay of the input wave after passing through the waveguide array is mainly determined by the effective index of the waveguides. Therefore, the waveguide array can be engineered using different core width distribution to generate any desired light beam. Examples, working at the frequency of 0.3 THz show that good focusing phenomenon with different focus lengths and spot sizes were observed, as well as arbitrarily tilted propagation of incident plane waves. The structure introduces a new method to perform wavefront manipulation, and can be utilized in many important applications in terahertz imaging and communication systems.

Pressure-driven flow of a Herschel-Bulkley fluid with pressure-dependent rheological parameters

The lubrication flow of a Herschel-Bulkley fluid in a symmetric long channel of varying width, 2h(x), is modeled extending the approach proposed by Fusi et al. [“Pressure-driven lubrication flow of a Bingham fluid in a channel: A novel approach,” J. Non-Newtonian Fluid Mech. 221, 66–75 (2015)] for a Bingham plastic. Moreover, both the consistency index and the yield stress are assumed to be pressure-dependent. Under the lubrication approximation, the pressure at zero order depends only on x and the semi-width of the unyielded core is found to be given by σ(x) = −(1 + 1/n)h(x) + C, where n is the power-law exponent and the constant C depends on the Bingham number and the consistency-index and yield-stress growth numbers. Hence, in a channel of constant width, the width of the unyielded core is also constant, despite the pressure dependence of the yield stress, and the pressure distribution is not affected by the yield-stress function. With the present model, the pressure is calculated numerically solving an integro-differential equation and then the position of the yield surface and the two velocity components are computed using analytical expressions. Some analytical solutions are also derived for channels of constant and linearly varying widths. The lubrication solutions for other geometries are calculated numerically. The implications of the pressure-dependence of the material parameters and the limitations of the method are discussed.

MORPHOLOGICAL AND CHEMICAL CHARACTERISTICS OF VARIOUS PUMMELO (Citrus maxima (Burm.) Merr.) ACCESSIONS FROM MAGETAN REGENCY

Magetan Regency was the production centre of pummelo that have many accessions with various morphological and chemical characteristics, but only a few of them were identificated. This study was aimed at identifying morphological and chemical characteristics of pummelo fruits in Magetan Regency. The study was conducted in the Biology Laboratory of Djuanda University, Bogor from May to July 2015. Results showed with regard to their morphological characteristic, pomelo plants in this region were found to have spheroid and spheroid-pyriform fruits and the weight of their fruit parts, fruit core width, mesocarp thickness, fruit circle before peeling, fruit circle after peeling, number of fruit segments, number of developed seeds, and edible parts of the fruit were varied. Chemical characteristics were also found to be varied with vitamin C content of 29.80−44.66 mg/100g, total soluble solids (TSS) content of 8.10−9.72°Brix, total titratable acidity (TAA) of 0.31−0.53 g/100 ml, and TSS/ TAA ratio of 17.69−28.58. Key words: production centre of pummelo, spheroid, vitamin C, TSS

Quasi-soliton solution of Korteweg-de Vries equation and its application in ion acoustic waves

Investigation of interaction between solitons and their background small amplitude waves has been an interesting topic in numerical study for more than three decades. A classical soliton accompanied with oscillatory tails to infinite extent in space, is an interesting quasi-soliton, which has been revealed in experimental study and really observed. However, analytical solution of such a special quasi-soliton structure is rarely considered. In this paper, two branches of soliton-cnoidal wave solution as well as the two-soliton solution of the Korteweg-de Vries (KdV) equation are obtained by the generalized tanh expansion method. The exact relation between the soliton-cnoidal wave solution and the classical soliton solution of the KdV equation is established. By choosing suitable wave parameters, the quasi-soliton behavior of the soliton-cnoidal wave solution is revealed. It is found that with modulus of the Jacobi elliptic function approaching to zero asymptotically, the oscillating tails can be minimized and the soliton core of the soliton-cnoidal wave turns closer to the classical soliton solution. In addition, the quasi-soliton structure is revealed in a plasma physics system. By the reductive perturbation approach, the KdV equation modeling ion acoustic waves in an ideal homogeneous magnetized plasma is derived. It is confirmed that the waveform of the quasi-soliton is significantly influenced by the electron distribution, temperature ratio of ion to electron, magnetic field strength, and magnetic field direction. Interestingly, the amplitude of the quasi-soliton keeps constant due to the -independence of nonlinear coefficient A. The width of the soliton core and the wavelength of the surrounded periodic wave become constant with the further increase of . The explicit soliton-cnoidal wave solution with quasi-soliton behavior obtained here is applicable to many physical scenarios. For instance, the quasi-soliton structure can be viewed as a classical soliton with perturbations, and can correct the classical soliton in both theoretical and experimental study.

Experimental Studies on the Formation of Air-core inside the Drop Shaft

In this study, the drainage efficiency of the multi-stage intake structure, which transports flood to the underground storage, was investigated from the laboratory experiments. The multi-stage intake structure was designed based on the tangential intake and the steps on the bed were purposes to decrease the energy of approaching flow. The experimental results show that the maximum water depth was effectively decreased in the entrance of the drop shaft. The measurements results of the air core width in the drop shaft show that the flow was stably drained without the choking. Furthermore, the air core width tends to increase with the Froude number, and these results indicate that the multi-stage intake structure is applicable to convey the approaching flow with relatively high velocity.

Effect of non-local interactions on the vortex solution in Bose-Einstein Condensates

We consider the Gross-Pitaevskii (GP) model of a Bose-Einstein Condensate (BEC) to study a single vortex line in the presence of non-local repulsive s-wave scattering. We show that in addition to the vortex solution with core width of the order of the healing length, there exists a vortex solution whose width is a microscopic length scale of the order of s-wave scattering length and is independent of the healing length. We compare the two classes of vortex solution and show the region where one can possibly observe the vortex whose width is of the order of scattering length.

Development and optimization of a miniaturized fiber-optic photoplethysmographic sensor

Photoplethysmography (PPG) is a widely used technique for measuring blood oxygen saturation, commonly using an external pulse oximeter applied to a finger, toe, or earlobe. Previous research has demonstrated the utility of direct monitoring of the oxygen saturation of internal organs, using optical fibers to transmit light between the photodiode/light emitting diode and internal site. However, little research into the optimization and standardization of such a probe has yet been carried out. This research establishes the relationship between fiber separation distance and PPG signal, and between fiber core width and PPG signal. An ideal setup is suggested: 1000-μm fibers at a separation distance of 3 to 3.5 mm, which was found to produce signals around 0.35 V in amplitude with a low variation coefficient.

Architecture of buried reverse fault zone in the sedimentary basin: A case study from the Hong-Che Fault Zone of the Junggar Basin

It is widely accepted that the faults can act as the conduits or the barrier for oil and gas migration. Years of studies suggested that the internal architecture of a fault zone is complicated and composed of distinct components with different physical features, which can highly influence the migration of oil and gas along the fault. The field observation is the most useful methods of observing the fault zone architecture, however, in the petroleum exploration, what should be concerned is the buried faults in the sedimentary basin. Meanwhile, most of the studies put more attention on the strike-slip or normal faults, but the architecture of the reverse faults attracts less attention. In order to solve these questions, the Hong-Che Fault Zone in the northwest margin of the Junggar Basin, Xinjiang Province, is chosen for an example. Combining with the seismic data, well logs and drill core data, we put forward a comprehensive method to recognize the internal architectures of buried faults. High-precision seismic data reflect that the fault zone shows up as a disturbed seismic reflection belt. Four types of well logs, which are sensitive to the fractures, and a comprehensive discriminated parameter, named fault zone index are used in identifying the fault zone architecture. Drill core provides a direct way to identify different components of the fault zone, the fault core is composed of breccia, gouge, and serpentinized or foliated fault rocks and the damage zone develops multiphase of fractures, which are usually cemented. Based on the recognition results, we found that there is an obvious positive relationship between the width of the fault zone and the displacement, and the power-law relationship also exists between the width of the fault core and damage zone. The width of the damage zone in the hanging wall is not apparently larger than that in the footwall in the reverse fault, showing different characteristics with the normal fault. This study provides a comprehensive method in identifying the architecture of buried faults in the sedimentary basin and would be helpful in evaluating the fault sealing behavior.