Perpendicular Direction Research Articles

Developing Superperforming Composites by Harnessing Fiber Orientation and Processing Technology.

The current research on the development and performance evaluation of unique composites focuses on an unexplored combination of fibers of PBO (polybenzoxazole Zylon) as reinforcement and PEEK (polyetheretherketone) as a matrix. Their fibers were braided in equal ratios and then compression-molded to develop composites by manipulating all long fibers in one direction (unidirectional, a UD composite) and for the other one half in one direction and the remaining half in the perpendicular direction (bidirectional, a BD composite). The performance was evaluated by hardness (micro- and scratch) studies followed by tensile and impact strength. Furthermore, the lap shear strength of the adhesive joints developed with these fibers in various orientations was also analyzed. The performance properties were compared with those of neat PEEK. It was observed that an exceptional increase compared to neat PEEK in impact strength of 10,000% and tensile strength of 662% was achieved in the case of the UD composite. Scanning electron microscopy (SEM) and microcomputed X-ray tomography were used on failed specimens to analyze the reasons for failure.

Simulation study of phonon transport at the GaN/AlN superlattice interface: Ballistic and non-equilibrium phenomena

GaN/AlN superlattice structures have potential for high electron mobility transistors (HEMTs) applications; however, nonequilibrium phonon transport mechanisms within the superlattice have not been systematically investigated. Therefore, we investigate in detail the non-Fourier thermal conductivity of superlattice structures in the perpendicular interface direction and in the parallel interface direction around the phonon BTE numerical solution in this paper, taking the kinetic parameter based on the first principle as the input parameter of the equations and based on the DOM numerical solution scheme. The study reveals that mode temperature non-equilibrium in superlattices arises from ballistic transport within the layers and interface scattering between the layers. The thermal conductivity (TC) of superlattices can be modulated by scale effects, and in superlattices with small thicknesses, phonons exhibit quasi-ballistic transport. The interface thermal resistance predominantly originates from contributions by acoustic phonon (AP) and the first optical phonon (OP1). With increasing interface density, the combined effects of interface scattering and boundary scattering lead to strong phonon scattering, resulting in a decrease in TC parallel to the interfaces. This work provides valuable insights into the thermal transport properties of GaN/AlN superlattice semiconductors and offers useful theoretical guidance for thermal management through phonon particle properties.

Magnetic splitting induced ferromagnetism in chromium-doped HfSe2

Two-dimensional (2D) magnetic layered materials have gained significant interest in spintronic for memory storage devices. Herein, the electronic and magnetic properties of high-quality single crystals of chromium (Cr)-doped hafnium diselenide were studied. The electronic study indicated that the Cr-doped HfSe2 reveals the semiconducting nature with a proper bandgap as identified by angle-resolved photoemission spectroscopy and first-principle density functional theory (DFT) calculations. The magnetic results indicate that the HfSe₂ exhibited ferromagnetic characteristics with the substitution of Cr atoms in a perpendicular direction. The Cr-doped HfSe2 sample shows a ferromagnetic phase below ∼58 K, indicating the critical temperature (Tc) of magnetic order, while above this temperature, it shows a paramagnetic phase that can follow the Curie-Weiss Law. It can be seen that the magnetic moment is approximately 0.16 emu/g at 5 K, which further decreases with increasing temperature until 60 K and then transforms to a paramagnetic phase. The sample can clearly show a weak out-of-plane magnetic anisotropy with a coercivity of around 50.56 Oe and a saturation magnetization value of 0.029 emu/g. Convincingly, it was observed from the ARPES results that the valence band is split due to the spin-orbit interaction of Cr atoms, which can induce ferromagnetic order. At the same time, the temperature-dependent ARPES data shows that the splitting is higher below the Tc, while it is weaker above the Tc. The DFT results revealed that near the Fermi level, the spin-up and spin-down are spin-polarized with asymmetric trends. It can be observed that substituting Cr on the octahedral sites of Hf atoms influences the electron spin order created by Hf vacancies (as validated by the magnetic coupling measured by electron paramagnetic resonance spectroscopy experiments), which can change the magnetic alignment to induce the magnetism in HfSe2. This study highlights that doping transition metal in HfSe2 has promising potential for future applications, especially in memory devices and spintronic technologies.

(Invited) Electrochemical Tuning of Thermoelectric Performance of Carbon Nanotubes

One-dimensional materials have potential for high performance thermoelectric energy conversion. To experimentally understand how one-dimensional electronic structures can enhance thermoelectric performance, we have investigated the thermoelectric properties of single walled carbon nanotubes (SWCNTs) such as the relationships among electronic structures, the location of Fermi-level, Seebeck coefficients, and Power factor by combining thermoelectric measurements and electrolyte gating techniques. Through the studies, we have revealed unique properties such as violation of thermoelectric trade-off, isotropic Seebeck coefficient, and gigantic power factor [1]. However, in addition to that, it is important to understand how the carrier density also affects the thermal conductivity of the carbon nanotube thin films for correct evaluation of ZT value. Therefore, we have developed a measurement system which can evaluate thermal conductivity by tuning the location of Fermi-level through electrochemical gating techniques. Time-domain thermoreflectance (TDTR) measurement is one of methods which can evaluate the thin film thermal conductivity. In conventional TDTR system, Al is used as metal transducer, but Al is electrochemical reactive, and thus it is very difficult to combine the TDTR measurements with electrochemical techniques. To solve this problem, we developed a TDTR system using Au as a metal transducer [2]. By using Au as a metal transducer, we can evaluate both the electrical and thermal properties at the same time. By using system, we can evaluate thermal properties of thin films during electrolyte gating, and have evaluated how the change of charrier density affects the thermal conductivity of carbon nanotube thin films [3]. By preparing the aligned single-walled carbon nanotube thin film, we evaluated the ZT value in the perpendicular direction to the nanotube axis as a function of carrier density. The ZT value in this direction can be maximized to be 0.1 by tuning the Femi-level around 1st van hove singularity [4].

Simulated structure and thermodynamics of decagonal Al-Co-Cu quasicrystals

Atomic structures of Al-Co-Cu decagonal quasicrystals (dQCs) are investigated using empirical oscillating pair potentials (EOPP) in molecular dynamic (MD) simulations that we enhance by Monte Carlo (MC) swapping of chemical species and replica exchange. Predicted structures exhibit planar decagonal tiling patterns and are periodic along the perpendicular direction. We then recalculate the energies of promising structures using first-principles density functional theory (DFT), along with energies of competing phases. We find that our τ-inflated sequence of QC approximants (QCAs) are energetically unstable at low temperature by at least 3 meV/atom. Extending our study to finite temperatures by calculating harmonic vibrational entropy, as well as anharmonic contributions that include chemical species swaps and tile flips, our results suggest that the quasicrystal phase is entropically stabilized at temperatures in the range 600-800 K and above. It decomposes into ordinary (though complex) crystal phases at low temperatures, including a partially disordered B2-type phase. We discuss the influence of density and composition on QC phase stability; we compare the structural differences between Co-rich and Cu-rich quasicrystals; and we analyze the role of entropy in stabilizing the quasicrystal, concluding with a discussion of the possible existence of “high entropy” quasicrystals. Published by the American Physical Society 2024

The Relation between Variances of 3D Density and Its 2D Column Density Revisited

We revisit the relation between the variance of three-dimensional (3D) density ( σρ2 ) and that of the projected two-dimensional (2D) column density ( σΣ2 ) in turbulent media, which is of great importance in obtaining turbulence properties from observations. Earlier studies showed that σΣ/Σ02/σρ/ρ02=R , where Σ/Σ0 and ρ/ρ 0 are 2D column and 3D volume densities normalized by their mean values, respectively. The factor R depends only on the density spectrum for isotropic turbulence in a cloud that has similar dimensions along and perpendicular to the line of sight. Our major findings in this paper are as follows. First, we show that the factor R can be expressed in terms of N, the number of independent eddies along the line of sight. To be specific, σΣ/Σ02/σρ/ρ02 is proportional to ∼1/N due to the averaging effect arising from independent eddies along the line of sight. Second, we show that the factor R needs to be modified if the dimension of the cloud in the line-of-sight direction is different from that in the perpendicular direction. However, if we express σΣ/Σ02/σρ/ρ02 in terms of N, the expression remains same even in the case the cloud has different dimensions along and perpendicular to the line of sight. Third, when we plot NσΣ/Σ02 against σρ/ρ02 , two quantities roughly lie on a single curve regardless of the sonic Mach number, which implies that we can directly obtain the latter from the former. We discuss observational implications of our findings.

The Influence of Gas Pulsed Flow on Hydrodynamic Behaviors of Refined Standard Sugar

The influence of gas-pulsed flow when supplied in the perpendicular direction to the refined standard (RS) sugar layer has been studied in this article. Some hydrodynamic parameters of the RS sugar in the gas-pulsed fluidized bed have also been determined. The research results have been applied in the design of the RS sugar dryer using the modern pulsed fluidized bed drying method. The bed porosity in the static particle layer (e0) was 0.44 while the bed porosity in the minimum fluidized bed (emg) was 0.484 and the minimum fluidized bed velocity (Umg) was 0.65 m/s. The bed porosity in the homogeneous fluidization bed (ehg) was 0.67, and the homogeneous fluidization velocity (Uhg) of 1.63 m/s has been calculated. The critical velocity (Ucg) of 2.7 m/s and the bed porosity (ecg) of 0.8 in the circulating particle bed were determined. The pressure drop through the layer of RS sugar with a thickness of 300 mm was 3808 N/m2.

Spin noise spectroscopy of an alignment-based atomic magnetometer

Optically pumped magnetometers (OPMs) are revolutionizing the task of magnetic-field sensing due to their extremely high sensitivity combined with technological improvements in miniaturization which have led to compact and portable devices. OPMs can be based on spin-oriented or spin-aligned atomic ensembles which are spin polarized through optical pumping with circular or linear polarized light, respectively. Characterization of OPMs and the dynamical properties of their noise is important for applications in real-time sensing tasks. In our work, we experimentally perform spin noise spectroscopy of an alignment-based magnetometer. Moreover, we propose a stochastic model that predicts the noise power spectra exhibited by the device when, apart from the strong magnetic field responsible for the Larmor precession of the spin, white noise is applied in the perpendicular direction aligned with the pumping-probing beam. By varying the strength of the noise applied as well as the linear-polarization angle of incoming light, we verify the model to accurately predict the heights of the Larmor-induced spectral peaks and their corresponding linewidths. Our work paves the way for alignment-based magnetometers to become operational in real-time sensing tasks. Published by the American Physical Society 2024

The influence of temperature and the magnetic field on Ni electrodeposition from citrate bath and its electrocatalytic performance towards hydrogen evolution reaction

The demand for energy surpasses the available supply, leading to various economic, social, and environmental consequences. Hydrogen is one of the most clean and renewable source for energy. Therefore, the electrocatalytic hydrogen evolution reaction (HER) presents a promising eco-friendly approach for generating sustainable hydrogen energy. However, in alkaline conditions, HER encounters slow kinetics due to challenges associated with hydrogen adsorption and hydrolysis. In this article, thin Ni films were synthesized using the electrodeposition technique from citrate electrolyte. Their suitability as electrocatalysts for the hydrogen evolution reaction (HER) in a 1 M NaOH solution was estimated. This research investigates how the uniform magnetic field and temperature affect the process of nickel electrodeposition from a citrate bath and its subsequent influence on surface morphology and catalytic properties for the hydrogen evolution reaction (HER). Additionally, alterations in surface material wettability were examined based on changing the temperature during using the magnetic field for the electrodeposition process and shows how this effect on the catalytic performance towards HER. The outputs show that using the magnetic field for fabrication of Ni thin films at room temperature enhances the surface morphology and its catalytic performance for HER. However, the study reveals that using the temperature for Ni electrodeposition improves its catalytic performance independently of the magnetic field, whereas combining temperature with the magnetic field for Ni thin film fabrication diminishes their catalytic performance for the hydrogen evolution reaction (HER). The nickel thin film produced at 25 °C under the influence of a magnetic field, whether parallel or perpendicular, demonstrates the lowest overpotential of − 268 mV to achieve a current density of 10 mA cm−2. Additionally, it exhibits the smallest Tafel slope values of 106 mV dec−1 and 128 mV dec−1 for the parallel (Bǁ) and perpendicular (BꞱ) directions, respectively. However, the magnetic field effect diminishes at elevated temperatures. Nickel thin films prepared at 35 °C under the influence of perpendicular (BꞱ) and parallel (Bǁ) directions exhibit higher overpotential values of − 314 mV and − 322 mV, respectively.

Development of rare earth element and carbon fiber‐based filler for polyethylene—Mechanical and thermal performance

AbstractIn the present study, three fillers produced with carbon fiber powder (CFP) and rare earth elements were developed for low‐density polyethylene production. These fillers included CFP with a grain size of less than 400 microns and over 90% pure lanthanum and cerium oxides. Polyethylene was employed to ensure the thermoplasticity and homogeneity of the fillers. The fillers were mixed with the matrix material separately, first mechanically and then homogenously in the extruder, then the test bars were produced with an injection machine. In the mechanical tests, it was determined that the tensile strength of the test bars improved by ~20% and the elastic region increased due to the increasing amount of filler. Similarly, an improvement of about 40% in bending stress was realized. In addition, as the fluidity of the mixtures has improved, it has been possible to produce at lower temperatures and save energy in the production. Thermogravimetric analysis was conducted to determine the melting/crystallization temperatures and material losses in the compounds. The scanning electron microscope analysis showed that the fillers were irregularly distributed on the surface in parallel and perpendicular directions. In addition, x‐ray diffraction and energy dispersive spectroscopy analyses were performed on the surfaces.

Testing of wood shear modulus based on cantilevered square plate torsional vibration method

ABSTRACT The application of the energy method has proposed a dynamic testing method for the shear modulus in two mutually perpendicular directions on the principal surface of wood using a cantilevered square plate torsional vibration method. In the study, this method was applied to measure the shear modulus of larch wood in the LT and TL directions, as well as the longitudinal and transverse shear modulus of Laminated Veneer Lumber (LVL) sheets. The validity of the results was confirmed through experimental verification using the asymmetric four-point bending beam method, the free plate torsional vibration method, and the free square plate torsional mode method. Simulation calculations of the principal shear modulus for six species of trees with width-to-thickness ratios ranging from 10 to 25 were also conducted using this method. The conclusions drawn suggest that a width-to-thickness ratio of 15 for the cantilevered square plate provides sufficient accuracy for testing the principal shear modulus of wood. Furthermore, the difference in shear modulus between two mutually perpendicular directions on the principal surface of wood is dependent on the width-to-thickness ratio of the cantilevered square plate, indicating that this method outperforms other dynamic methods for testing wood shear modulus.

A facile spinning approach towards the continuous production of aligned nanocellulose films

In this work, we present an alternative approach to cellulose nanofibril film (CNF) production, taking inspiration from the wet spinning of fibers to wet spin films. During the spinning process, a CNF suspension is injected into a coagulation bath, where the partially aligned CNF network is locked. The CNF alignment of the dry films is then detected by wide angle X-ray scattering (WAXS). The comparison between the ultimate strengths and strengths at breaks of the films produced with different process parameters, including the suspension injection rate, bath pH, and bath flow rate, indicated no significant change in mechanical properties, suggesting a reliable and constant outcome for large-scale film fabrication. Furthermore, the produced films demonstrated high total light transmittance of 93 % at the wavelength of 550 nm, making them suitable for optoelectronic applications. Polarized optical microscopy revealed that even a low degree of CNF alignment can lead to anisotropic optical properties. Moreover, an anisotropic response to humidity was observed, in which the films preferentially bend in the perpendicular direction of the CNF orientation, thus opening a way for humidity-driven actuators.

Probability Prediction of Curing Process-Induced Deformation for V-Shape Composite Structures Based on FEM Method and Data Mining.

Continuous fiber-reinforced composites are increasingly used in industry for their superior specific modulus and strength. The curing process-induced deformation (PID) has been a critical problem during manufacturing, which always exhibits dispersed values even if the curing process curve and structural parameters remain consistent. This work conducted probability prediction of PID for V-shape composite structures based on the FEM method and data mining. A sequential coupling thermal-chemical-mechanical coupling FE model is established in ABAQUS. The prediction accuracy of the included angle between two sides is verified by the experimental results. Material parameter uncertainties are considered for V-shape structures with different radii and thicknesses. Based on the dataset from the FE model, a decision tree is established and trained to analyze the sensitivity and to predict the probability distribution of PID. The results show that PID increases with the coefficients of thermal expansion in the in-plane perpendicular fiber direction and out-of-plane normal direction. The data-mining method is accurate enough for the PID prediction, and its efficiency provides an additional calculation option in engineering applications.

Trinocular 360-degree stereo for accurate all-round 3D reconstruction considering uncertainty

This research proposes a method for accurate all-round 3D reconstruction of an indoor environment in one-shot using a system of trinocular 360-degree cameras. Binocular 360-degree stereo is unable to reconstruct in all directions due to lack of disparity along epipolar directions. Thus, a third camera along a perpendicular epipolar direction is introduced to cover for this, making the system trinocular. However, previous works with trinocular stereo did not adequately take into account the uncertainty of disparity estimation and geometric constraints around 3D reconstruction. Therefore, we propose a geometric optimization scheme considering disparity estimation uncertainty and show that this results in both higher accuracy and lesser outliers along epipolar directions, in both simulated and real environments.

Accuracy Improvement Quantification Using Phase-Separated PIV Measurements

This paper aims to quantify the Particle Image Velocimetry (PIV) measurement accuracy improvement along the phase boundaries of two-phase flows, due to the use of phase-separated PIV analysis, compared to conventional PIV analysis without separating the phases. To compute the true error produced by PIV analysis, a patchwork of synthetic image pair with a known displacement is used (ground truth). As real flows might have arbitrary flow direction and magnitude across the phase boundary, the patchwork of image-pair includes a variety of direction combinations, i.e. flows running into each other or away from one another, shear flow, sink flow, flow towards a wall and flow away from a wall, flow running into a stagnant phase, flows with perpendicular directions, and flows that are 45° to each other. The relative error distribution along the boundaries reveals that the relative error level depends on the flow direction on each side of the boundary. Results also indicate that phase-separated PIV measurements can bring the relative error level from ~200% down to ~5% along the boundaries.

Assessment of Methods to Derive Tensile Properties of Ultra-High-Performance Fiber-Reinforced Cementitious Composites.

There is no unified method for deriving the tensile properties of fiber-reinforced ultra-high-performance cementitious composites (UHPCC). This study compares the most common material tests based on a large series of laboratory tests performed on a self-developed UHPCC mixture. The cementitious matrix, with a compressive strength of over 150 MPa and a matrix tensile strength of 8-10 MPa, was reinforced with 2% by volume of 15 mm long and 0.2 mm diameter straight high-strength steel microfibers. Over 100 uniaxial tensile tests were performed on three test configurations using cylindrical cores drilled out from larger prismatic specimens in three perpendicular directions. In addition to uniaxial tests, flexural tests on prismatic elements and flexural tests on thin plates were conducted, and the tensile properties were derived through digital image correlation (DIC) measurements and inverse analysis. Furthermore, splitting tensile tests on cylindrical specimens were employed to ascertain the tensile properties of the matrix. The outcomes of the diverse laboratory tests are presented and discussed in detail. The relationships between crack width and deflection in the context of flexural tests were developed and presented. In conjunction with compression tests and modulus of elasticity tests, the constitutive law is presented for the investigated materials.

Analysis on power flow of Lamb waves generated by laser illumination in carbon fiber reinforced plastic laminates

Abstract The laser ultrasonics using guided waves excited by laser irradiation has attracted attention as an efficient non-destructive inspection method for carbon fiber reinforced plastic (CFRP) composite laminates. In this paper, to clarify the properties of laser-excited Lamb waves, we investigate the power flow of Lamb waves in an anisotropic CFRP laminate. The temperature rising caused by laser absorption is analytically calculated, and the derived thermal force is input to a finite element model to simulate the generation of Lamb waves. It is found that the power flow has an obvious directivity in a quasi-isotropic CFRP laminate. The power flow is smaller in the direction parallel to the carbon fibers of the surface layer and is larger in the perpendicular direction, but the maximum is in slightly different direction; this result was validated by an experiment. Such directivity pattern is determined by two factors: the distribution of thermal force and the stacking sequence of CFRP laminates. Moreover, we investigate the different simulation models (metal-coated CFRP and cross-ply CFRP) to discuss the influence of each factor on the distribution of power flow separately.

Improved calibration method based on phase-slope description in phase-shift deflectometry

Phase-shift deflectometry is a widely used high-precision gradient measurement method for assessing the topography of specular objects. The calibration of phase-shift deflectometry measurement systems involves establishing the phase-slope mapping relationship. This paper analyzes the causes of phase variations at different calibration points in existing phase-slope analysis models. Based on the fact that changes in height simultaneously produce phase variations in two perpendicular directions, a decoupling method is proposed to address the phase ambiguity problem to some extent. Through simulation, the variation in height phase and slope distribution were quantitatively analyzed for a unidirectional inclined plane to validate the proposed algorithm. Additionally, measurement experiments were performed on a unidirectional inclined plane with an inclination angle of −2.584° and a concave mirror with a curvature radius of 779.87 mm. Based on the findings, the decoupling method reduced the relative root-mean-square error of the gradient measurement for the inclined plane in the inclined direction by 2.206% and improved the error range of the curvature radius for the concave mirror from [0.55%, 4.1%] to [0.22%, 3.86%]. By comparing with the existed method, the decoupling method showed a certain advantage in practicality.

Line-scanning microscopy with laterally symmetric imaging using simultaneous cross-line illumination

Using an on-the-fly scanning scheme, line confocal microscopy can obtain complex structures of large biological tissues with high throughput. Yet, it suffers from lateral imaging asymmetry and thus introduces the potential deformations of the observation results. Here, we propose cross-line illumination microscopy (cLIM) that acquires the imaging data of two perpendicular directions simultaneously through the same objective lens in a line scanning and utilizes two-direction deconvolution fusion to achieve lateral symmetric imaging performance. Imaging fluorescence beads indicates that cLIM reduces lateral resolution asymmetry from 46.1% to 2.5% and improves lateral resolution by 31.0%, compared with traditional line-scanning imaging. Compared with commercial point-confocal microscopy, the cLIM has a 25.84× increase in imaging speed and 1.93× better background-suppressing ability when imaging an 11,306 μm×7783 μm×100 μm mouse kidney slice. We also show the advantages of the cLIM in observing direction-sensitive texture features by imaging a muscular tissue slice. cLIM offers a novel solution to achieve laterally symmetric line-scanning imaging with simple modifications while maintaining high throughput and accuracy for imaging large-scale samples.

TESTING OF BLEACHING ON COCOBOLO (Dalbergia retusa Hemsl.,) WOOD

In this study, the effects of single and double component wood bleaching chemicals on the color parameters, glossines values and whiteness index values of cocobolo (Dalbergia retusa Hemsl.,) wood were investigated. Single and double component bleaching chemicals were applied to the wood material surfaces with the application technique in line with the company’s recommendations. Test measurements were made on bleached and unbleached wood materials. Obtained results were compared with each other. According to the determined results, lightness (L*) value, chroma (C*) value, red (a*) color tone, yellow (b*) color tone, hue (ho) angle value, glossiness values perpendicular to fibers (⊥) and parallel (║) directions at 60o, glossiness value at 85o in parallel (║) direction to the fibers, and whiteness index (WI*) values in perpendicular (⊥) and parallel (║) directions to the fibers were determined. The ∆E* values were found to be 10.22 in the double component and 2.31 in the single component. While the two-component bleaching chemical caused an increase in L*, b*, a*, C* and ho values, it caused a decrease in the one-component bleach chemical. All WI* values were increased with two component bleaching chemicals. The glossiness values at 60° in the perpendicular and parallel directions to the fibers were decreased with one component bleaching chemical. The bleaching chemicals used in the study caused different results on wood material surfaces.