Rectangular Parallelepiped Shape Research Articles

Plasmon-Free Surface-Enhanced Raman Spectroscopy Using α-Type MoO3 Semiconductor Nanorods with Strong Light Scattering in the Visible Regime.

Recent developments in semiconductor-based surface-enhanced Raman scattering (SERS) have achieved numerous advancements, primarily centered on the chemical mechanism. However, the role of the electromagnetic (electromagnetic mechanism) contribution in advancing semiconductor SERS substrates is still underexplored. In this study, we developed a SERS substrate based on densely aligned α-type MoO3 (α-MoO3) semiconductor nanorods (NRs) with rectangular parallelepiped ribbon shapes with width measuring several hundred nanometers. These structural attributes strongly affect light transport in the visible range by multiple light scattering generated in narrow gaps between NRs, contributing to the improvement of SERS performance. Engineering the nanostructure and chemical composition of NRs realized high SERS sensitivity with an enhancement factor of 2 × 108 and a low detection limit of 5 × 10-9 M for rhodamine 6G (R6G) molecules, which was achieved by the stoichiometric NR sample with strong light scattering. Furthermore, it was observed that the scattering length becomes significantly shorter compared with the excitation wavelength in the visible regime, which indicates that light transport is strongly modified by mesoscopic interference related to Anderson localization. Additionally, high electric fields were found to be localized on the NR surfaces, depending on the excitation wavelength, similar to the SERS response. These optical phenomena indicate that electromagnetic excitation processes play an important role in plasmon-free SERS platforms based on α-MoO3 NRs. We postulate that our study provides important guidance for designing effective EM-based SERS-active semiconductor substrates.

Elastic constants of equiatomic Fe–Ni Invar alloy single crystal

In a disordered fcc structure, the equiatomic Fe–Ni alloy is of great interest as a soft magnetic Invar alloy with a near zero or low thermal expansion coefficient. In the L10 ordered phase, it is of interest as a potential high-performance permanent magnet alloy. In this work, the first detailed measurements of the elastic constants in a [001]-oriented Fe-50 at. % Ni alloy single crystal under a no magnetic field condition were made using the resonant ultrasound spectroscopy technique. The elastic constants measured allow one to understand the nature of atomic bonding in a material and the mechanical response to applied stress. The single crystal sample having a rectangular parallelepiped shape was prepared from a single crystal grown using the vertical Bridgman technique. The elastic constants C11, C12, and C44 were obtained from the resonant frequencies observed over a frequency range of 100–900 kHz. Using these C11, C12, and C44 values, Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio were calculated to be 99.1 GPa, 73.4 GPa, 176.7 GPa, and 0.20, respectively. The large anisotropy factor of 3.29 highlights the strong directional dependence of the material’s mechanical behavior.

DEVELOPMENT OF METHODS AND ALGORITHMS FOR ESTIMATING THE TEMPERATURE DISTRIBUTION IN THE BODY OF A RECTANGULAR PARALLELEPIPED SHAPE UNDER THE INFLUENCE OF HEAT FLOW AND THE PRESENCE OF HEAT EXCHANGE

The article describes methods and computational algorithms for estimating the temperaturedistribution law in the body of a rectangular parallelepiped shape under the influence of heat flowand the presence of heat exchange. It is believed that one of the faces is amenable to heat flow, andthe other faces are insulated or are under the influence of the environment. To use the variationalapproach, the total energy functional is calculated, taking into account the boundary conditions.Minimizing the functional and equating it to zero, we obtain a system of linear equations, thesolution of which gives the temperature of a rectangular parallelepiped at the nodal points. Further,substituting these nodal temperature values into the approximating function, we obtain the law oftemperature distribution in the body in the form of a rectangular parallelepiped. The temperaturedistribution law is obtained by dividing a rectangular parallelepiped into one, two and threeelements. To speed up the process of calculating the temperature distribution law, an algorithm hasbeen developed that allows you to create a program code that increases the calculation efficiency byan order of magnitude. This is achieved by the fact that the created code contains only a systemof linear equations, unlike the main program, which forms a general functional of full energies,calculates derivatives of this functional and obtains a system of equations.

A Variational Approach for Estimating the Temperature Distribution in the Body of a Rectangular Parallelepiped Shape

The novelty of this study is a variational approach for estimating the temperature distribution in the body of a rectangular parallelepiped shape when a heat flow enters one of the faces of a rectangular parallelepiped, and heat exchange with the environment occurs on the opposite side. At the same time, options are considered when the remaining faces of a rectangular parallelepiped are thermally insulated or vice versa. My contribution of this work is that we calculated the laws of temperature distribution when dividing a rectangular parallelepiped into a different number of elements. It is shown that acceptable accuracy is achieved already by dividing the sides of a rectangular parallelepiped into three or 4 parts. In addition, a comparison of the temperature distribution law for a rectangular parallelepiped and a rod close in size, other things being equal, was carried out. Their slight difference is shown.

Electronic and lattice properties of nanostructured TiN/MgO and ScN/MgO superlattices

Various nanostructured TMN(001) dot/MgO(001) (TM = Sc, Ti) superlattices have been investigated. Here, we consider single and double layered TM dot structures with rectangular and rectangular parallelepiped shapes. MgO-2 × 2 and −3 × 3 substrates were used. Their electronic states were obtained using a total energy pseudopotential method. The internal atomic coordinates from the repeated slab model in the unit cell were fully relaxed. Various relaxed structures and electronic properties of the TMN(001) dot/MgO-2 × 2 and −3 × 3 superlattices were obtained. We determined their total and partial densities of states. Peaks of density of states (DOS) of the ScN dot/MgO superlattices around the band gap consist of Sc 3d and N 2p states and those of the TiN dot/MgO superlattices consist of mainly Ti 3d states. The largest band gap value in the TiN(001) dot/MgO(001) (ScN(001) dot/MgO(001)) superlattice is 1.22 eV (1.48 eV) from the density-functional theory-local density approximation calculation. The electronic properties (band gap values, DOS curves, and many more) vary with varying dot shape and substrate size. Most band gap values corrected using a generalized density-functional theory were improved.

Particle Swarm Optimization-Based Identification of the Elastic Properties in Resonant Ultrasound Spectroscopy.

Resonant ultrasound spectroscopy (RUS) is an experimental measurement method for obtaining elastic constants of an anisotropic material from the free resonant frequencies of a sample. One key step of the method is to adjust elastic constants to minimize the difference between calculated and experimental frequencies. The method has been widely used in the determination of elastic constants of solid materials with high Q value, such that the resonant frequencies can be easily extracted from the measured spectrum. However, for materials with high damping, the identification of the resonant modes becomes difficult due to the overlap of resonant peaks and the absence of some modes. Thus, the success of RUS depends largely on initial guessing of elastic constants. In this article, these limitations are addressed with a new RUS approach. First, the identification of resonant modes is transformed into a linear assignment problem solved by the Hungarian algorithm. Second, the inversion of the elastic tensor is achieved using the particle swarm optimization (PSO) algorithm. This method, having the ability of global optimization in the search space, is less sensitive to the initial guess of the elastic constants. The PSO algorithm was successfully applied for the first time to RUS data, providing estimates of elastic constants that were in good agreement with reference values. First, simulated data for a transversely isotropic sample of enamel of rectangular parallelepiped shape were used to validate the proposed RUS method. Second, the proposed RUS approach was validated using experimental data collected on a sample of transversally isotropic bone-mimicking material.

OPERATIONAL EVALUATION OF THE PROBABILITY OF PERFORMANCE OF THE ORDER IN THE CONDITION OF UNCERTAINTY OF CONSUMER DEMAND

Modern software allows industrial enterprises to rationalize the use of employees' working hours, to reduce labor intensity and material consumption of manufactured products, but the factor of consumer demand uncertainty forces us to focus on a probabilistic model when forming a portfolio of orders. The paper considers the method of operational forecasting of production costs and the probability of execution of the application by an enterprise operating in the market of perfect competition in the conditions of clients filing applications with an incomplete amount of information. The author's approach to the operational assessment of production costs is based on the ABC method and the rules of cutting design "Muller and son". It allows the calculation step of the request to edit a group of multidimensional products according to customer's requirements, the result is the ratio of the balance between expected customer price and pledged the company profitability. It allows at the stage of calculating the application to edit a group of multidimensional products according to customer requirements, as a result, a balance is reached between the price expected by the client and the profitability laid by the enterprise. According to this method, for calculating a non-standard request, a multidimensional product is represented as a group of rectangular parallelepiped shapes. Costs for each material layer used in the product are considered separately in the calculation process. The study of the nature of the relationship between the consumption rates of sheet material, the dimensions of a multidimensional product and the useful width of the roll made it possible to establish their proportions leading to peak values of the consumption of material. To exclude additional material costs, a method has been developed and tested to find the optimal material consumption taking into account the probability of order fulfillment. Application of these recommendations will allow industrial enterprises to increase the value of products and the enterprise for each participant of relations; will be the basis for the growth of competitiveness of domestic products.

Relative equilibria of dynamically symmetric CubeSat nanosatellite under the action of aerodynamic and gravitational torques

Motion of a dynamically symmetric CubeSat nanosatellite around the mass center on the circular orbit under the action of aerodynamic and gravitational torques is considered. We determined the nanosatellite equilibrium positions in the flight path axis system. We took into account the fact that the CubeSat nanosatellite has a rectangular parallelepiped shape and, therefore, the aerodynamic drag force coefficient depends on the angles of attack and proper rotation. We obtained formulae which allow calculating the values of the angles of attack, precession and proper rotation that correspond to the equilibrium positions, depending on the mass-inertia and geometric parameters of the nanosatellite, the orbit altitude, and the atmospheric density. It is shown that if the gravitational moment predominates over the aerodynamic one, there are 16 equilibrium positions, if the aerodynamic moment predominates over the gravitational one, there are 8 equilibrium positions, and in the case when both moments have comparable values there are 8, 12 or 16 equilibrium positions. Using the formulae obtained, we determined the equilibrium positions of the SamSat-QB50 nanosatellite. We calculated the ranges of altitudes where SamSat-QB50 nanosatellite has 8, 12, or 16 relative equilibrium positions.

Elongational Viscosity of Weakly Entangled Polymer Melt via Coarse-Grained Molecular Dynamics Simulation

We investigated the elongational flows of the weakly entangled linear polymer melt using a coarse-grained molecular dynamics simulation. We extended the uniform extensional flow (UEF) method developed by Nicholson and Rutledge (D. A. Nicholson and G. C. Rutledge, J. Chem. Phys., 145, 244903 (2016)) for application to Langevin dynamics. We succeeded in observing the elongational viscosity of the weakly entangled linear polymer melt from the equilibrium state to the steady state using the extended UEF method, whereas the conventional rectangular parallelepiped shape technique for extensional flows has failed to do so for over 20 years.

Formation of annular cracks in glass during contact interaction

Experimental results are presented on the indentation of steel balls of various diameters into glass samples having a rectangular parallelepiped shape. The ultimate load in the formation of an annular crack in the vicinity of the contact region and the radius of this crack were determined experimentally. The annular crack appeared outside the contact area almost in all tests. Due to the fact that the diameter of the contact area was much smaller than the dimensions of the samples, the glass samples were considered as an elastic half-space. Huber’s solution for Hertz’s problem of pressing a ball into an elastic half-space was used to determine the field of contact stresses in the fracture zone. Local criterion for maximum stresses and nonlocal failure criteria (average stress criterion, the Nuismer criterion, and the gradient criterion) were used to model fracture in a contact interaction. The ultimate tensile stress and the critical stress intensity factor of the glass were experimentally determined on beams without a notch and with a notch for calculating a parameter having a dimension of length and entering nonlocal failure criteria. It is shown that the estimates of the radius of the annular crack that are closest to the experimental data give a gradient criterion among the applied criteria. Estimates of the ultimate tensile stress according to this criterion exceed the values obtained when the beams are bent, which can be explained by the scale factor.

Investigation of symmetric non-spherical particle shapes by applying low-resolution spherical harmonics

The issue of mathematical modelling of non-spherical shapes of particles is considered. Thus, application of the spherical harmonics (SH) technique in modelling the simplest symmetric star-shaped particles is demonstrated by applying low-resolution functions. The investigation was restricted to a circular cylinder and a rectangular parallelepiped, geometrically primitive, but widespread oblate industrial shapes. The modelling quality was studied by considering selected error norms and the most important integral characteristics of a particle geometry, including the surface area and volume. The presented results discovered new features of the spherical harmonic technique and enhanced understanding of their applicability to describe non-spherical shapes.

Thermal conductivities under unsaturated condition and mechanical properties of cement-based grout for vertical ground-heat exchangers in Korea—A case study

In this study, the thermal conductivities of cement-based grouts for backfilling of vertical ground-heat exchangers were investigated under the saturated, air-dried and unsaturated conditions. The mechanical properties including the p-wave velocity, elastic modulus and Poisson’s ratio also were measured. The mix proportions applied were quartzite sand/cement ratios of 1, 1.5, 2, 2.5 and 3, with a fixed water/cement ratio of 0.7. Mixed-grout specimens were prepared in both rectangular parallelepiped shape (11cm×6cm×4cm) and cylindrical shape (5cmdia.×10cm height). Their thermal conductivities decreased linearly with decreasing degree of saturation. Also, as the sand/cement ratio was increased, the thermal conductivity at the same degree of saturation was higher, and the thermal conductivity decreased more steeply as the degree of saturation decreased. Based on these results, an empirical equation representing the relationship between the degree of saturation and the thermal conductivity of the cement-based grouts was derived. The results obtained in this study are expected to be utilized as input data for thermal and mechanical behavior analyses of ground-heat exchangers and their installations.

Experimental and constitutive modeling approaches for a study of biomechanical properties of human coronary arteries

The study concerns the determination of mechanical properties of human coronary arterial walls with both experimental and constitutive modeling approaches. The research material was harvested from 18 patients (range 50-84 years). On the basis of hospital records and visual observation, each tissue sample was classified according to the stage (0, I, II, III) of atherosclerosis development (SAD). Then, strip samples considered as a membrane with the shape of rectangular parallelepiped were preconditioned and subjected to uniaxial tensile tests in longitudinal (n=27) and circumferential (n=4) direction. With experimental data obtained, the stress-strain characteristics were prepared. Furthermore, tensile strengths and related strains, stiffness coefficients and tangent modules of elasticity were computed. For a constitutive model of passive mechanical behavior of coronary arteries, values of material parameters were computed. The studies led to the following conclusions. Most importantly, the atherosclerotic changes affect all the mechanical properties of arterial walls. A progress of arteriosclerosis contributes to an increase of vascular stiffness. The highest values of the stiffness coefficients are obtained for the tissues in the advanced stage of the disease. We were also able to observe that gradual calcification, progression of atherosclerosis and degradation of collagen in the tissue caused a decrease of tensile strengths and related strains. Finally, a comparison made for the tissues with the advanced SAD showed that the tensile strengths and strains were much higher in the case of the samples with the circumferential orientation rather than those with the longitudinal one.

Relationship between thermal conductivity and soil–water characteristic curve of pure bentonite-based grout

The relationship between the soil–water characteristic curve (SWCC) and thermal conductivity of pure bentonite and bentonite–sand grouts used as backfilling materials in ground heat exchangers was investigated in a laboratory experiment. The mix proportions utilized in this study were bentonite to 20% and 30% of the total weight, adding quartzite sand to 30% and 50% of the total weight (bentonite+water). Mixed grout specimens were prepared in rectangular parallelepiped shapes. The thermal conductivity, volumetric water content and matric suction of unsaturated specimens were measured as the saturated specimens were slowly dried at room temperature until there was little change in the measured values. The matric suction and thermal conductivity showed a bilinear relationship, with a breaking point identifying the air-entry value (AEV) and the SWCC describing the relationship between the matric suction and the volumetric water content (VWC). As the matric suction slowly increased to the AEV, the VWC of the specimens decreased, whereas the thermal conductivity increased; then, beyond the AEV, it rapidly decreased again. That is, as the specimens dried out, attaining the maximum at the AEV, their thermal conductivity decreased. The thermal conductivity and the VWC showed a parabolic relationship with the maximum thermal conductivity value at around the VWC corresponding to the AEV of each specimen. Revised empirical equations representing the relationship between these two parameters were suggested for prediction of the thermal characteristics of bentonite-based grout in geothermal heat pump applications.

Changes in the thermal conductivity of bentonite-based grouts with varying volumetric water content

In this study, the thermal characteristics of pure bentonite and bentonite–sand grouts for backfilling geothermal heat exchangers were investigated. Mix proportions were 20% and 30% of the total weight of bentonite, to which 30% and 50% of the total weight of quartzite sand were added. Specimens were prepared in rectangular parallelepiped shapes, and the thermal conductivity of partially saturated specimens with varying volumetric water content was measured. As the saturated specimen slowly dried out at room temperature, the change in volumetric water content with the elapsed time showed a typical soil–water characteristics curve. Thermal conductivity of the specimens increased and, after reaching the peak value, decreased again. A parabolic trend curve could be drawn to deduce the relationship between the thermal conductivity and the volumetric water content for each specimen. Empirical equations representing the correlation between these two parameters were also suggested for predicting the thermal characteristics of bentonite-based grouts in geothermal heat pump applications.

Effect of the preparation conditions of a barium–tantalate photocatalyst on the overall photocatalytic splitting of H2O

The photocatalytic activity of a barium tantalum (Ba–Ta) mixed oxide prepared by the polymerizable complex method (PC method) for the overall splitting of H2O was related to its morphology originating from its preparation conditions. Photocatalysts with a rectangular parallelepiped shape showed the highest photocatalytic activity.

AUDIO CONFERENCING APPARATUS

Microphones arranged in an array shape along a longitudinal direction are respectively formed in both the longitudinal side surfaces of a housing 2 with substantially an elongated rectangular parallelepiped shape, and speakers arranged in an array shape along the longitudinal direction are formed in a lower surface. The speaker array forms sound emission beams based on sound emission directivity set according to a conference environment. On the other hand, when the microphone array forms sound collection beams by sound collection signals collected, a talker direction is detected from these beams and an output sound signal corresponding to this direction is formed and also is reflected on setting of the sound emission directivity. Also, when there are plural input sound signals, the sound emission directivity is set according to a use situation of the plural input sound signals.

Effects of additional permanent magnet on the levitation force of single domain GdBCO bulk superconductor

Effects of additional permanent magnet on the levitation force of a single domain GdBCO bulk superconductor have been investigated with a cylindrical permanent magnet in their coaxial configuration under zero field cooled state at liquid nitrogen temperature. The magnetic polarity N of cylindrical permanent magnet is pointed to the GdBCO bulk superconductor, and the two additional permanent magnet of rectangular parallelepiped shape are fixed on two sides of the GdBCO bulk superconductor in different arrangments. It was found that the levitation force can be improved to about 61.5 N, which is more than 2 times higher than that (29.8 N) of the system without the additional permanent magnet, when the magnetic polarity N of two additional permanent magnets points to the GdBCO bulk superconductor in horizontal direction. The levitation force is reduced to 19.6N, which is about 65.8% of the levitation force 29.8N of the system without the additional permanent magnets, when the magnetic polarity N of two additional permanent magnet are antiparallel to the magnetic polarity N of the cylindrical permanent magnet. The results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on reasonably designing the system configuration, which is very important during the practical design and applications of superconducting magnetic levitation systems.

Approach to 3D dose verification by utilizing autoactivation

To evaluate the deposited dose distribution in a target, we have proposed to utilize the annihilation gamma-rays emitted from the positron emitters distributed in the target irradiated with stable heavy-ion beams. Verification of the one dimensional (1-D) dose distributions along and perpendicular to a beam axis was achieved through our previous works. The purpose of this work is to verify 3-D dose distributions. As the first attempt uniform PMMA targets were irradiated in simple rectangular parallelepiped shapes, and the annihilation gamma-rays were detected with a PET scanner. By comparing the detected annihilation gamma-ray distributions with the calculated ones the dose distributions were estimated. As a result the estimated positions of the distal edges of the dose distributions were in agreement with the measured ones within 1 mm. However, the estimated positions of the proximal edges were different from the measured ones by 5–9 mm depending on the thickness of the irradiation filed.

Synthesis of Structurally Defined Ta3N5 Particles by Flux-Assisted Nitridation

The synthesis of a transition metal nitride, Ta3N5, was studied. Morphological changes of Ta3N5 particles, depending on the synthetic method, starting materials, and nitridation conditions, were examined in detail. Flux-assisted nitridation was found to be a facile one-step route to a metal nitride with morphological control of the resulting particles. Scanning electron microscopy (SEM) observation revealed that morphologically defined particles of Ta3N5 were obtained using Zn, NaCl, or Na2CO3 as a flux. Flux-assisted nitridation of TaCl5 with Zn or NaCl produced nearly monodisperse fine particles larger than a few tens of nanometers. The size of these particles could be controlled by variation of the nitridation temperature. Highly crystallized Ta3N5 particles with a rectangular parallelepiped shape were produced from TaCl5−NaCl or Ta2O5−Na2CO3 mixtures by nitridation above 1123 K, because of the annealing effect of the flux.