Longitudinal Gap Research Articles

An elastic model for bioinspired design of carbon nanotube bundles

Collagen fibers provide a good example of making strong micro- or mesoscale fibers from nanoscale tropocollagen molecules through a staggered and cross-linked organization in a bottom-up manner. Mimicking the architectural features of collagen fibers has been shown to be a promising approach to develop carbon nanotube (CNT) fibers of high performance. In the present work, an elastic model is developed to describe the load transfer and failure propagation within the bioinspired CNT bundles, and to establish the relations of the mechanical properties of the bundles with a number of geometrical and physical parameters such as the CNT aspect ratio and longitudinal gap, interface cross-link density, and the functionalization-induced degradation in CNTs, etc. With the model, the stress distributions along the CNT–CNT interface as well as in every individual CNT are well captured, and the failure propagation along the interface and its effects on the mechanical properties of the CNT bundles are predicted. The work may provide useful guidelines for the design of novel CNT fibers in practice. Mimicking the staggered and cross-linked features of collagen fibril structure has been shown to be a promising approach to develop carbon nanotube (CNT) fibers of high performance. In this work, an elastic model is developed to describe the load transfer and failure propagation within the collagen-inspired CNT bundles. With the model, the relations of the mechanical properties of the bundles with a number of geometrical and physical parameters are established, two failure modes and their transition are predicted, and optimal interface design to eliminate interface stress concentration are discussed.

Joint modelling of longitudinal biomarker and gap time between recurrent events: copula-based dependence

In this paper, we will extend the joint model of longitudinal biomarker and recurrent event via copula function for accounting the dependence between the two processes. The general idea of joining separate processes by allowing model-specific random effect may come from different families distribution. It is a main advantage of the proposed method that a copula construction does not constrain the choice of marginal distributions of random effects. A maximum likelihood estimation with importance sampling technique as a simple and easy understanding method is employed to model inference. To evaluate and verify the validation of the proposed joint model, a bootstrapping method as a model-based resampling is developed. Our proposed joint model is also applied to pemphigus disease data for assessing the effect of biomarker trajectory on risk of recurrence.

Near-infrared longitudinal plasmon polariton photonic gaps in a semiconductor metamaterial photonic crystal

We perform a theoretical investigation on the near-infrared longitudinal plasmon polariton gaps in a one-dimensional semiconductor metamaterial photonic crystal. The considered structure is (AB)N where N is the number of periods, layer A is a dielectric, and layer B is a semiconductor metamaterial composed of Al-doped ZnO (AZO) and ZnO. For oblique incidence under transverse magnetic mode, it is found that, due to the anisotropic permittivity of semiconductor metamaterial, there exist multiple longitudinal plasmon polariton gaps which are ascribed to the coupling between photon mode and metamaterial bulk electric plasmon. The photonic band and gap structures are investigated as functions of incident angle, filling factor of semiconductor metamaterial, thicknesses of constituent layers, and number of periods as well.

Why do three-wheelers carrying schoolchildren suffer very low fatal crashes?

This paper investigates the possible causes of low fatalities in three-wheelers (autorickshaw) carrying schoolchildren in India. The data was collected in the form of First Information Report (FIR) from local police stations from 2007 to 2012 and video-graphic surveys were done on four arterial roads running through Ludhiana, Punjab, India. Surveys were also done on one subarterial road near school zone which was used by three-wheelers carrying schoolchildren. The objective of the study was to investigate the hypothesis that drivers behave differently while following or overtaking three-wheelers carrying children. Many researchers have investigated the effect of passengers on the driver of the same vehicle, but there was no evidence of any study which investigated the effect of child passengers on nearby vehicles. It was found that heavy vehicles maintain more gaps while following or overtaking three-wheelers carrying children as compared to those not carrying children. It was also found that this effect is more prominent at speeds higher than 40km/h. On the other hand lighter vehicles keep the highest lateral and longitudinal gaps to heavy vehicles and three-wheelers without children respectively.

Bose-Einstein condensation and Silver Blaze property from the two-loopΦ-derivable approximation

We extend our previous investigation of the two-loop $\mathrm{\ensuremath{\Phi}}$-derivable approximation to the case of a finite chemical potential $\ensuremath{\mu}$ and discuss Bose-Einstein condensation in the case of a charged scalar field with $O(2)$ symmetry. We show that the approximation is renormalizable by means of counterterms which are independent of both the temperature and the chemical potential. We point out the presence of an additional skew contribution to the propagator as compared to the $\ensuremath{\mu}=0$ case, which comes with its own gap equation (except at Hartree level). We solve this equation together with the field equation, and the usual longitudinal and transversal gap equations to find that the transition is second order, in agreement with recent lattice results to which we compare. We also discuss a general criterion an approximation should obey for the so-called Silver Blaze property to hold, and we show that any $\mathrm{\ensuremath{\Phi}}$-derivable approximation at finite temperature and density obeys this criterion if one chooses an UV regularization that does not cut off the Matsubara sums.

Numerical research on dynamic stress of phononic crystal ROD in longitudinal wave band gap

For the propagation of harmonic longitudinal stress wave in phononic crystal rod (PCR), transfer matrix of elastic wave in PCR was derived based on the wave equation and band structure of infinite PCR was calculated. For semi-infinite PCR, theoretical derivation of dynamic stress solutions of arbitrary section and internal interfaces was conducted with Bloch theorem. Inherent relationship between dynamic stress and surface wave modal frequency (SWMF) was analyzed. Afterwards, numerical computation mainly focusing on dynamic stress level of the internal interfaces of PCR was given in detail. Finally, numerical analysis for finite PCR was carried out and verified by finite element simulation. Our results show that SWMF has a significant influence on the dynamic stress, and exactly it is the formal pole of stress solution whose nature is directly determined by the sort order of the two materials constituting the PCR.

Solar Astronomy at High Altitude

A major project called the National Lar ge Solar Telescope (NLST) has been proposed for pursuing Solar Astronomy at High Altitude. The project envisages the development of a state-of-the-art 2-m class telescope to carry out high-resolution studies of the solar atmosphere. This project is led by the Indian Institute of Astrophysics and has national and international partners. Its geographical location will fill the longitudinal gap between Japan and Europe and is expected to be the lar gest solar telescope with an aperture lar ger than 1.5 m till ATST and EST come into operation. NLST is an on-axis alt-azimuth Gregorian multi-purpose open telescope with the provision of carrying out nighttime stellar observations using a spectrograph at the Nasmyth focus. The telescope utilizes an innovative design with low number of reflections to achieve a high throughput and low polarization. High order adaptive optics is integrated into the design that works with a modest Frieds parameter of 7-cm to give diffraction limited performance. The telescope will be equipped with a suite of post-focus instruments including broad and narrow band imagers, a high-resolution spectrograph and a polarimeter . A comprehensive site characterization programme has demonstrated the presence of at least two excellent sites for setting up observational facilities for solar astronomy at high altitude in India.

Effects of Material Parameters on Longitudinal Vibration Band Gaps in Thin Phononic Crystal Plates

The improved plane wave expansion method is used to investigate the effects of material parameters on the longitudinal vibration band gaps in thin phononic crystal plates. Both square lattice and graphite lattice are considered. Results show that the parameters playing the essential roles are the mass density ratio and the Young modulus ratio of the scatterers and the host materials.

Longitudinal Excitations in Bipartite and Hexagonal Antiferromagnetic Spin Lattices

Based on our recently proposed magnon-density-waves using the microscopic many- body approach, we investigate the longitudinal excitations in quantum antiferromagnets by including the second order corrections in the large-s expansion. The longitudinal excitation spectra for a general spin quantum number using the antiferromagnetic Heisenberg Hamiltonian are obtained for various spin lattice models. For bipartite lattice models, we find that the numerical results for the energy gaps for the longitudinal modes at q → 0 and the magnetic ordering wavevector Q are reduced by about 40-50 % after including the second order corrections. Thus, our estimate of the energy gaps for the quasi-one-dimensional (quasi- 1D) antiferromagnetic compound KCuF3 is in better agreement with the experimental result. For the quasi-1D antiferromagnets on hexagonal lattices, the full excitation spectra of both the transverse modes (i.e., magnons) and the longitudinal modes are obtained as functions of the nearest-neighbor coupling and the anisotropy constants. We find two longitudinal modes due to the non-collinear nature of the triangular antiferromagnetic order, similar to that of the phenomenological field theory approach by Affleck. We compare our results for the longitudinal energy gaps at the magnetic wavevectors with the experimental results for several antiferromagnetic compounds with both integer and non-integer spin quantum numbers, and also find good agreement after the higher-order contributions are included in our calculations.

SPSS: A Data Mining Tool for Analyzing the Results of Flow Induced Vibration Excitation in an Elastically Mounted Circular Cylinder at Different Interference Conditions

s: In this article, results of an analysis is investigated by using a data mining tool called ‘SPSS’, to identify the flow characteristics and response of an elastically mounted circular cylinder at different interference conditions. Numerical investigation is performed on a range of longitudinal gap ratios (2.0 ≤ L/D ≤ 4) and transverse gap ratios (2.0 ≤ T/D ≤ 4) between the cylinders arranged in tandem and staggered configuration. The effects of the interference cylinders were analyzed at specific relative positions were observed and it has been identified that the parameters, reduced velocity (U/fD) and relative positions were significantly influences the flow induced vibration excitation. Hence, in this article, an accent is laid on the efficient of ‘SPSS Tool’ for analyzing the results of flow induced vibration excitation in an elastically mounted circular cylinder at different interference conditions. From the results, it is observed that, reduced velocity must be lesser than the threshold value and also the observed that the relative positions (spacing ratios) is playing a significant role when compared to the reduced velocity. Further, the results shows that, at the fluid flow characteristics of elastically mounted circular cylinder in staggered arrangement with two interfering cylinders in upstream conditions the oscillatory amplitude ratio (A/D=0.250) is found to be minimum.

Absorption effects on plasmon polariton-gap solitons in Kerr/metamaterial superlattices

A thorough study of the absorption effects on the plasmon polariton-gap soliton-induced transparency in 1D Kerr/metamaterial superlattices is presented. Results indicate that for frequencies close to the bottom or top edge of the bulk-like longitudinal plasmon-polariton gap, the transmission of a finite Kerr/metamaterial superlattice presents a multistable behavior, switching from very low values to the maximum transparency at particular values of the incident power even in the presence of loss effects. Moreover, calculations suggest the existence of resonant plasmon polariton-gap solitons of various orders depending on the particular value of the incident power. The present results reveal that plasmon polariton-gap soliton-induced resonant solutions lead to the transparency of a stack with nonlinear inclusions, a nonlinear optical analog of the electronic barrier-transmission resonances.

Dynamic characteristics of a periodic rib-skin structure

Periodic rib-skin structure is composed of an array of identical elements connected in parallel and each element is a stiffened structure consisting of skins and ribs which are modeled as elastic beams and rigid bodies respectively. The periodic structure is designed to gain excellent longitudinal and flexural vibration band gaps in which corresponding waves cannot propagate in the structure freely. Firstly, longitudinal and flexural vibration mobility matrices of the skins and ribs are derived to obtain mobility equations of single-floor and multi-floor periodic elements. Then, propagation constants of the infinite rib-skin structure are calculated and an in-depth numerical study is performed to examine the relationships between the wave propagation constants and dynamic response of semi-infinite and finite periodic structures. Furthermore, flexural vibration reduction performances of the periodic rib-skin structure below 3000 Hz are discussed in detail. Finally, an experimental setup for measuring the acceleration frequency response of a two-floor periodic rib-skin structure is carried out to verify the numerical solution. Both predicted and measured results have demonstrated that longitudinal and flexural band gaps exist in the periodic rib-skin structure. The flexural vibration transmitted through the structure is substantially suppressed in a wide frequency range below 3000 Hz.

Marginal adaptation of new bioceramic materials and mineral trioxide aggregate: a scanning electron microscopy study.

This study aimed to compare the marginal adaptation of new bioceramic materials, EndoSequence Root Repair Material (ERRM putty and ERRM paste), to that of mineral trioxide aggregate (MTA) as root-end filling materials. Thirty-six extracted human single-rooted teeth were prepared and obturated with gutta-percha and AH-26 sealer. The roots were resected 3 mm from the apex. Root-end cavities were then prepared with an ultrasonic retrotip. The specimens were divided into three groups (n=12) and filled with MTA, ERRM putty or ERRM paste. Epoxy resin replicas from the resected root-end surfaces and longitudinally sectioned roots were fabricated. The gaps at the material/dentin interface were measured using scanning electron microscope (SEM). Transversal, longitudinal, and overall gap sizes were measured for each specimen. The data were analyzed using the Kruskal-Wallis test. In transversal sections, no significant difference was found between MTA, ERRM putty and ERRM paste (P=0.31). However, in longitudinal sections, larger gaps were evident between ERRM paste and dentinal walls compared to MTA and ERRM putty (P=0.002 and P=0.033, respectively). Considering the overall gap size values, the difference between three tested materials was not statistically significant (P=0.17). Within the limits of this study, the marginal adaptation of ERRM paste and putty was comparable to that of MTA. However, ERRM putty might be more suitable for filling the root-end cavities because of its superior adaptation compared to ERRM paste in longitudinal sections.

Microresistivity borehole image inpainting

Images rendered from measurements made by wireline microresistivity imaging tools include longitudinal gaps whenever the well circumference exceeds the total width of the pad-mounted electrode arrays. The fraction of an image containing null data depends on tool design, and it is commonly approximately 30% for 261 mm (8.5 in.)-bit size wells increasing to approximately 50% in 311 mm (12.25 in.) wells. We use cues from the measured parts to infer information missing from the gaps; a method has been developed that simulates the process by decomposing the measured parts into their morphological components using sparse representations of multiscale multiorientation transforms, then recomposing the full-bore image assuming it to be efficiently represented by the transform’s elemental bases. The approach was evaluated using real data sets with a variety of geologic features, including full-coverage images from small diameter wells artificially obscured to simulate images from larger diameter wells. For borehole images dominated by curvilinear features, reconstructions from artificially obscured images were visually indistinguishable from the original unobscured images for a broad range of coverage loss and for all apparent dip angles below near-vertical, regardless of degree of parallelism (or lack thereof). Successful reconstruction of near-vertical features (including those with complex boundaries such as breakouts) was more dependent on coverage loss, but in these cases, the results were consistent with judgments made by interpreters. Therefore, we found that inpainting provides a consistent starting point for reproducible quantitative geologic analysis, and it is an enabler for automated feature recognition.

Tunability of longitudinal wave band gaps in one dimensional phononic crystal with magnetostrictive material

Ways for controlling and adjusting the longitudinal wave band structures of one dimensional (1-D) rod phononic crystals with magnetostrictive material are theoretically investigated by the plane wave expansion method. Z-L model is adopted to accurately describe the constitutive relations of phononic crystal containing magnetostrictive material. Taking the magneto-mechanical coupling into account, the longitudinal wave band structures are calculated through the development of effective elastic constant, piezomagnetic constant, and magnetic permeability for magnetostrictive rod. Numerical results show that the longitudinal wave band gaps characteristics are significantly influenced by the applied static magnetic field and compressive pre-stress. Some new phenomena, such as the multi-peaks of the band gap widths corresponding to the varying filling fraction of the binary rod phononic crystal, are investigated.

Measured pressures on the basis of bottom slab with gaps in the flow direction in a channel

A study was conducted to determine whether the back edges of the longitudinal gaps of a floor tile fixed to the bottom of a canal with a supercritical flow convert kinetic energy into pressure energy using Froude numbers in the range of 2.84 to 10.12. In each test the pressure was measured on 16 points on the bottom surface of the tile with piezo-resistive transducers along three longitudinal lines: one central line with 8 sensors and two lateral lines with 4 sensors each on either side of the central line. In this manner the distribution of the median pressures under the test tile was determined. The test tile is similar to those used in civil engineering structures for the purpose of avoiding the erosive action of the turbulence of a supercritical flow. The analysis of the measured pressures shows that even when the top surfaces of the canal floor and of the protective block are in the same horizontal plane, the back edges of the longitudinal gaps transform the energy of velocity into pressure energy. In such a way a factor has been identified that intervenes in the production of the hydrodynamic force that lifts revetments of different structures, and that has until now been ignored in the study of this problem.

Electronic features induced by Stone–Wales defects in zigzag and chiral carbon nanotubes

It has been recently shown [P. Partovi-Azar, A. Namiranian, J. Phys.: Condens. Matter, 24 (2012) 035301.] that Stone–Wales (SW) defects induce different electronic features when they are formed with different angels with respect to the axis of armchair carbon nanotubes. However, the electronic features introduced by SW defects in metallic zigzag and chiral carbon nanotubes is less considered in the literature. In this paper, by means of density functional calculations, we study the electronic effects induced by SW defects in metallic zigzag and chiral tubes. We inspect how these effects change with defect orientation and concentration. We show that two and three distinctive orientations of SW defects, respectively in the case of zigzag and chiral tubes, unlike those in armchair ones, behave the same and both introduce a semiconducting gap and an electron-rich region around the defects. For zigzag tubes, the longitudinal defects open wider band gaps than circumferential ones. The value of the gaps in zigzag and chiral tubes are attributed to the degree of deformation caused by the defects.

Excited states of quasi-one-dimensional hexagonal quantum antiferromagnets

We investigate the excited states of the quasi-one-dimensional quantum antiferromagnets on hexagonal lattices, including the longitudinal modes based on the magnon-density waves. A model Hamiltonian with a uniaxial single-ion anisotropy is first studied by a spin wave theory based on the one-boson method; the ground state thus obtained is employed for the study of the longitudinal modes. The full energy spectra of both the transverse modes (i.e., magnons) and the longitudinal modes are obtained as functions of the nearest-neighbor coupling and the anisotropy constants. We have found two longitudinal modes due to the noncollinear nature of the triangular antiferromagnetic order, similar to that of the phenomenological field theory approach by Affleck. The excitation energy gaps due to the anisotropy and the energy gaps of the longitudinal modes without anisotropy are then investigated. We then compare our results for the longitudinal energy gaps at the magnetic wave vectors with the experimental results for several antiferromagnetic compounds with both integer and noninteger spin quantum numbers, and we find good agreement after the higher-order contributions are included in our calculations.

Problem solving in biochemistry: assessment, learning strategies, and preconceptions

Discipline‐based education research has produced varied perspectives on defining and assessing scientific problem solving. The goals of this dissertation work are to describe and explain longitudinal performance gaps across a two‐year biochemistry curriculum, as well as to synthesize a more advanced pedagogical understanding of scientific problem solving from previously fragmented sources. Student performance will be measured using the Individual Problem Solving Assessment (IPSA), and achievement rates in each domain of problem solving will describe longitudinal performance. The results of a pilot study indicate that after the first year of the curriculum, domain achievement rates for students pursuing a B.S. in Biochemistry range from 9% to 64%. To explain performance gaps, potential contributors will also be investigated, using two additional measures that reflect alternate views of problem solving. The impact of our corresponding problem‐based learning strategies will also be evaluated. Multivariate multiple linear regression analyses will be used to generate quantitative models of the performance phenomena. Additionally, students’ preconceptions about problem solving are being identified. This study will ultimately elucidate connections among emerging theories of defining and assessing scientific problem solving.Research support is provided under NSF TUES Award #DUE‐1043079.

A low loss mechanical splice for gas sensing using Hollow-Core Photonic Crystal Fibre

In this paper, a low loss mechanical splice for Hollow-Core Photonic Crystal Fibre (HC-PCF) based multi-gas sensing system is introduced. Compared with the recent micro-structured optical fibre gas cells, the proposed HC-PCF gas cell has relatively simpler construction. The gas cell is composed of HC-PCF of 50cm length and core diameter is 10±1μm. The HC-PCF is connected to the single mode fibre (SMF) and multi mode fibre (MMF) via FC-APC connector. This creates a longitudinal gap between the two fibres which acts as a channel of gas diffusion in HC-PCF. The hollow-core and the capillaries in the cladding of HC-PCF act as gas channels. A measurement system for low gas concentrations based on this approach is also proposed.