Step Interval Research Articles

Constructing and Characterizing TiAlN Thin Film by DC. Pulsed Magnetron Sputtering at Different Nitrogen/Argon Gas Ratios

In this survey, the magnetron sputtering with Dc. Pulsed mode was embroiled to deposit TiAlN thin film on AISI 316 as a substrate. All the plasma magnetron parameters were fixed excluding the nitrogen gas ratio which was varied from 10% to 50% with step interval of 10% with respect to argon. The structure, mechanical, tribological and electrochemical peculiarities of TiAlN films were studied. The TiAlN deposition rate is decreased in regard with increasing the nitrogen gas ratio where, the film thickness recorded a maximum value of 3 µm at nitrogen gas ratio of 10 %. X-ray configurations demonstrated the formation of solid solution phase of TiAlN with different orientations. The TiAlN coating has (111) preferred orientation at 10 and 20% nitrogen gas ratios while has (200) preferred orientation at 30- 50% nitrogen gas ratios. The crystallite size is decreased with increasing the nitrogen gas ratio. The results depicted that, the microhardness of TiAlN film is increased with decreasing the nitrogen gas ratio and recorded a maximum value of approximately 850 HV0.015 at 10% N2. Additionally, the tribological properties of the coated AISI 316 with TiAlN are enhanced compared with the uncoated sample. The wear volume loss of the coated sample at 10% N2 has a value of nearly 9X104 µm3 which is low in comparison with AISI 316 substrate that has a value of 4.5X106 µm3. The corrosion resistance of all TiAlN coatings was better than the uncoated sample. It was demonstrated; the change in nitrogen gas ratio affected the physicochemical characteristics of the TiAlN coating.

Dual lattice-path transformations and the dynamics of the major and minor exo-modes

The article investigates an extension of the theory of well-formed modes and proposes a model of the major and minor modes in harmonic tonality. The established theory of well-formed modes is well adapted to the description of the medieval diatonic modes. Its core is the conversion of the circle-of-fifths encoding into the circle-of-steps encoding of the seven generic scale degrees. This conversion is a linear automorphisms of the cyclic group of order 7 (known from well-formed scale theory). This automorphism can be lifted to three refined levels of description: (1) to the diatonic Regener transformation on the two-dimensional note-interval system and (2) to a conjugacy class of Sturmian morphisms, corresponding to the filling of the authentically (or plagally) divided octave by the modal species of the fifth and the fourth and (3) to associated lattice path transformations on chains of anchored note intervals. In the present paper the place of the authentic division of the octave into a perfect fifth and a perfect fourth is taken by a triadic division of the octave into a major third, a minor third, and a perfect fourth. The three triadic intervals are filled with patterns formed by three different step intervals. In the consequence, all the above-mentioned constructions on two-dimensional note-interval system have to be replaced by analogous constructions which are based on a three-dimensional system of Euler-notes and intervals. The resulting constructions are mathematically inspired by Arnoux and Ito [2001. “Pisot Substitutions and Rauzy Fractals.” Bulletin of the Belgian Mathematical Society Simon Stevin 8 (2): 181–207] and include the lifting of the diatonic Euler-Regener-transformation to substitutions on words in three letters, their geometrical action as lattice-path transformations and the study of their duals. A constitutive innovation is the music-theoretical interpretation of the eigen-values, eigen-vectors and eigen-co-vectors of the Euler-Regener-transformation and its dual. A modified instance of the classical Euler-Oettingen-Riemann tone net can be defined on the Handschin plane, the kernel of the linear eigen-height form. Finally, comparing the image under the dual lattice-path transformations of the dual of the step-interval trihedron anchored at the Euler-note C4 and of the dual of the step-interval anti-trihedron targeting the Euler-note C4, a dynamical system arises on a region of the continuous Handschin plane.

Value‐based deep reinforcement learning for adaptive isolated intersection signal control

Under efficiency improvement of road networks by utilizing advanced traffic signal control methods, intelligent transportation systems intend to characterize a smart city. Recently, due to significant progress in artificial intelligence, machine learning-based framework of adaptive traffic signal control has been highly concentrated. In particular, deep Q-learning neural network is a model-free technique and can be applied to optimal action selection problems. However, setting variable green time is a key mechanism to reflect traffic fluctuations such that time steps need not be fixed intervals in reinforcement learning framework. In this study, the authors proposed a dynamic discount factor embedded in the iterative Bellman equation to prevent from a biased estimation of action-value function due to the effects of inconstant time step interval. Moreover, action is added to the input layer of the neural network in the training process, and the output layer is the estimated action-value for the denoted action. Then, the trained neural network can be used to generate action that leads to an optimal estimated value within a finite set as the agents' policy. The preliminary results show that the trained agent outperforms a fixed timing plan in all testing cases with reducing system total delay by 20%..

An Accurate 3-D CFS-PML Based Crank–Nicolson FDTD Method and Its Applications in Low-Frequency Subsurface Sensing

An unsplit-field and accurate Crank–Nicolson cycle-sweep-uniform finite-difference time-domain (CNCSU-FDTD) method based on the complex-frequency-shifted perfectly matched layer (CFS-PML) is proposed. It is applied to 3-D low-frequency subsurface electromagnetic sensing problems. The presented CNCSU-FDTD takes advantage of both CFS-PML and unconditionally stable CN method so that it can attenuate evanescent waves, eliminate late-time reflections, and overcome the stability limits of the FDTD method. The time step intervals in CNCSU-FDTD can be 1000 times larger than that in the regular FDTD for the low-frequency sensing centered at 25 Hz while remaining accurate. Several 3-D numerical examples in the airborne transient electromagnetics system have been demonstrated to validate the proposed method. The CFS-PML-based CNCSU-FDTD method not only attains good accuracy but also saves several dozen times of CPU time as compared with the regular FDTD method.

IMU-based gait analysis in lower limb prosthesis users: Comparison of step demarcation algorithms

BackgroundInertial Measurement Unit (IMU)-based gait analysis algorithms have previously been validated in healthy controls. However, little is known about the efficacy, performance, and applicability of these algorithms in clinical populations with gait deviations such as lower limb prosthesis users (LLPUs). Research questionTo compare the performance of 3 different IMU-based algorithms to demarcate steps from LLPUs. MethodsWe used a single IMU sensor affixed to the midline lumbopelvic region of 17 transtibial (TTA), 16 transfemoral (TFA) LLPUs, and 14 healthy controls (HC). We collected acceleration and angular velocity data during overground walking trials. Step demarcation was evaluated based on fore-aft acceleration, detecting either: (i) maximum acceleration peak, (ii) zero-crossing, or (iii) the peak immediately preceding a zero-crossing. We quantified and compared the variability (standard deviation) in acceleration waveforms from superposed step intervals, and variability in step duration, by each algorithm. ResultsWe found that the zero-crossing algorithm outperformed both peak detection algorithms in 65% of TTAs, 81% of TFAs, and 71% of HCs, as evidenced by lower standard deviations in acceleration, more consistent qualitative demarcation of steps, and more normally distributed step durations. SignificanceThe choice of feature-based algorithm with which to partition IMU waveforms into individual steps can affect the quality and interpretation of estimated gait spatiotemporal metrics in LLPUs. We conclude that the fore-aft acceleration zero-crossing serves as a more reliable feature for demarcating steps in the gait patterns of LLPUs.

Investigation of influence of part inclination and rotation on surface quality in robot assisted incremental sheet metal forming (RAISF)

In incremental sheet metal forming (ISF), by maintaining contact between tool and sheet metal can help in uniform thickness distribution and improved surface quality. In the present work the tool path versatility has been explored by transferring some of the tool-sheet relative movements to the work piece by using a two-degree of freedom robotic manipulator with an aim to improve surface finish and achieve greater wall angles. The robotic manipulator has been designed to orient the sheet metal part with respect to the forming tool fixed in the three-axis machine tool to form steeper wall angle parts with better surface finish. The effect of rotational speed, wall angle, tilting angle and tool linear step interval on forming quality in robot assisted incremental forming has been studied and analyzed. Steeper wall angles and better surface finish were found to be obtained with the help of the robotic manipulator than the conventional incremental forming. The results of design of experiments based parametric study on surface finish have been presented.

Tuning band gap, color switching, optical contrast, and redox stability in solution-processable BDT-based electrochromic materials

Abstract 2,6-bis(trimethylstannane)-4,8-bis(2-octyldecyloxy)benzo[1,2-b:4,5-b′]dithiophene coupled with 2,5-didecyloxy-1,4-dibromobenzene and 4,7-dibromo-5,6-dioctyloxy-2,1,3-benzothiadiazole using Stille-coupling polymerization to afford the non D-A type polymer P1 and D-A type polymer P2, respectively. Two polymers displayed excellent solubility in normal organic solvents, so series of chemical instrumental analysis, such as NMR, GPC and elemental analysis, were carried out to confirm the inner structure and composition of the polymers. Different structure types exerted great influence on polymer's optical, electrochemical and electrochromic properties. Compared with P1 film, the introduction of the strong electron-withdrawing group benzothiadiazole improved conjugate effect along the polymer backbone of P2, which caused the redshift of ultraviolet–visible absorption spectrum and significant reduction in energy band gap. In addition, electrochromic performance test results showed that the P1 polymer film can switch between the orange-yellow and gray, while P2 film changed from blue in the neutral state to light yellow in the oxidation state. Moreover, the optical contrasts and response times of the polymer films also showed great differences due to the different molecular structure types. Higher transmittance changes and less sensitivity to the step interval on optical contrast indicated the fast switching speed and the superior cycle stability of P2 film.

Perfect balance and circularly rich words

A recent article [Milne, Andrew J., David Bulger, and Steffan A. Herff. 2017. “Exploring the Space of Perfectly Balanced Rhythms and Scales.” Journal of Mathematics and Music 11 (2):101--133] posits the notion of balance and contrasts it with evenness, which may be associated with the patterns of step intervals in either maximally even sets or well-formed scales. Scales defined as “perfectly balanced” are optimal in this regard. In this paper, we propose that perfectly balanced scales that display circular palindromic “richness” and also exhibit relatively few step “differences” may prove to be advantageous from a cognitive and musical perspective. For context, all circularly rich sets among 5-, 6-, and 7-note sets in 12-TET are identified. Finally, the minimal perfectly balanced sets in divisions of 30, 42, and 70 identified in Milne, Bulger, and Herff (2017) above are examined for the two constraints proposed here.

Formation of uniform metal traces using alternate droplet printing

Abstract Formation of uniform traces is fundamental, but challenging, in droplet-based 3D printing. Due to the scalloped surface topography of metal droplets and complex thermal deformation between them, sequentially printed traces tend to form low-quality shapes. Here, an alternate droplet printing method is proposed to print uniform metal traces. Instead of printing droplets successively, discrete droplet array with uniform intervals was first printed. Then, the gaps between droplets were fully filled up in a later printing iteration. Herein, the proper combination of the step interval and the thermal state in the droplet printing process were first investigated to ensure the success of the proposed printing method. Four typical shapes of segments were identified using multiple three-droplet deposition experiments. Moreover, metal trace printing experiments further revealed five distinct trace topographies. In addition, the relationship between the topographies of printed traces and the printing parameters (i.e., temperature of the substrate and printing step size) was studied to establish a trace-shape map. Finally, experiments show that metal traces with the dimensionless roughness (Ra/Dd) of 1.8% were successfully printed. The results demonstrate a significant reduction of the roughness comparing to the literature results printed in consecutive sequence.

Growth of Hexagonal AlN Crystalline Microrod by Physical Vapor Transport Method

Hexagonal aluminium nitride (AIN) microrods with high crystalline quality were grown by physical vapor transport (PVT) method at low growth temperature between 1700 and 1850 degrees C. The length of as-grown microrod is around 1 cm, and the width between 200-400 mu m. The microrod exhibits typical hexagonal geometrical shape with pale yellow color under optical microscopy. Scanning electron microscope (SEM) and atomic force microscope (AFM) images show each microrod with closely arranged step waviness, of which the step interval is 2-4 mu m and the height several nanometers. Raman spectrum characterization showed characteristic peaks of high crystalline AlN. The rod-like structure is attributed to slow growth velocity at lower crystalline temperature, enabling Al and N atoms having enough time to move to the lower energy site and to form heiagonal microrod along direction. High quality hexagonal AlN microrod is an enrichment to one-dimensional semiconductor materials. Data from this study suggest that, by further study on size and impurity control, high performance miniaturized opto-electronic device is hopeful to be achieved.

Void Fraction Measurement of Two Phase Flow in an External Air-Lift Loop with Middle Riser

Background/Objectives: The key objective of the present investigation is to study the void fraction distribution of two phase flow in a riser of an External Air-Lift Loop with middle riser and two downcomers on either side. Methods/ Statistical Analysis: Experimentation is performed to measure void fraction by using conductivity probe technique with the appropriate electrical processing circuit. The operating fluids considered were air and water. Air flow rate is varied from 0.00017 m3/s to 0.00116 m3/s with step interval of 0.0001 m3/s. The conductivity probe data obtained consists of qualitative change of voidage and radial distribution of void fraction. Findings: From the present investigation it is evident that the increase of air flow rate brings the more increase of void fraction. At all air flow rates void fraction got increased from centre of tube to the wall. Cubic profile is obtained at the high airflow rates, which is dependent again upon air flow rate. Different flow patterns were obtained from radial distribution of void fraction graph. Application/Improvements: By introducing the two downcomers to External Air-Lift loop, loop flow rate got increased and as a result the amount of water coming into the riser increased which resulted in lower averaged void fraction.

Pelvic movement variability of healthy and unilateral hip joint involvement individuals

Abstract Data variability analysis has been the focus of a number of studies seeking to capture differences of patterns generated by biological systems. Although there are several studies reporting variability in gait analysis we still have lack of researches that employ inertial sensors for the characterization of the variability of the duration of the gait cycle and pelvic movements for groups of individuals in healthy and hip joint involvement conditions. In this research this variability is characterized within the step and stride time intervals. Data were collected with subjects walking on a treadmill at a velocity of 2 km/h, being the group G1 with 10 healthy subjects (30.7 ± 6.75 years old) and G2 with 24 individuals with unilateral hip joint involvement (65 ± 8.5 years old). Two sets of inertial measurement units were employed for movement detection, and then features were extracted for the characterization of their variability. The coefficient of variation was used for assessing the variability. Significant differences (p

Morphic transitions of nanocarbons via laser pyrolysis of polyimide films

Attempting a thorough investigation of polyimide pyrolysis via CO2 lasers, we revisit the Laser-Induced Graphene (LIG) method, and determine the optimal operating window for producing pyrolytic nanocarbons. We design an experimental investigation that targets the full parameter space of available laser operating parameters: laser power, scan rate, and step interval. This allows us to produce different morphic groups of nanocarbons with properties depending on their surface morphology by directly controlling surface patterning. We further establish that the base material comprises a network of vertically aligned graphene channels, hereby referred to as graphene foam, thus readdressing the classification of Multi-Layer Graphene (MLG) given in previous research. We show how the laser pyrolysis method can be adapted for the production of carbon nanotubes (CNTs) via repeated pyrolysis of the starting graphene foam over high laser fluence levels. We characterize the pyrolytic nanocarbons via optical and scanning electron microscopy, Raman and UV–vis spectroscopy, surface tension measurements, and thermogravimetric analysis.

Imaging lightning intracloud initial stepped leaders by low‐frequency interferometric lightning mapping array

AbstractBy comparing the source position of pulses during initial leaders and the paths of subsequent dart leaders from typical bilevel intracloud (IC) flashes, we demonstrate a new method to image the detailed three‐dimensional (3‐D) structure and stepping dynamics of IC initial leaders. Using this approach, we show that nearly half of the initial breakdown pulses are not involved in the main channel extension but instead originate in nonpropagating branches. The primary upward but significantly tilted initial leader channels propagated with measured mean/median 3‐D step length of 295/265 m and mean/median step interval of 1.05/0.6 ms. The structure and dynamics of IC initial upward negative leaders are distinct from those of highly branched cloud‐to‐ground downward negative leaders. We suggest that the tilted initial leader channel and electric field could affect the observation on leader‐associated high‐energy radiation phenomena, such as the position‐dependent observation of terrestrial gamma ray flashes from space‐based detectors.

The Response of a Heat Loss Flowmeter in a Water Pipe Under Changing Flow Conditions

A heat loss flowmeter for measuring the volume flow rate of water in real time ( $t)$ was formed using two thick film segmented thermistors, range constant voltage (RCV) power supply, acquisition card, PC, and software. The input water temperature $T_{w}(t)$ was measured by a cold thermistor, while the water flow rate $Q(t)$ was determined using the heat loss principle by measuring the self-heated thermistor current $I(t)$ . The flowmeter inertia, stability, and accuracy were measured and analyzed on a flowmeter prototype in real-time and real conditions on the water mains. The flowmeter response was measured for different durations of step input water flow-out functions and intervals between steps. An independent ultrasonic flowmeter was connected in series with the thermal flowmeter to measure the ordered input water flow functions. The realized intelligent functions in real time were: measuring the input water temperature $T_{w}(t)$ and self-heating temperature $T_{s}(t)$ , auto-selection of RCV supply voltage $U(T_{w})$ , determination and modeling of the water flow rate in real time $Q(t)$ , determination of the water volume $V(t)$ , and determination of the thermal gradient on the self-heating thermistor as a water flow indicator $\Delta R_{s}(t)$ .

Numerical Study of Impurity-Induced Growth Hysteresis on a Growing Crystal Surface

Growth hysteresis is one of the remarkable phenomena of crystal growth induced by impurities; namely, the growth rates of crystal take different values between when supersaturation is decreased and is increased. The appearance of hysteresis has been explained on the basis of the mean field theory, in which the physical quantities such as step velocity, step interval, and density of impurities adsorbed on the crystal surface are averaged over space and time. Here, we propose a new method for the numerical simulation of step dynamics with impurity adsorption–desorption kinetics on a growing crystal surface. We numerically reproduce the growth hysteresis in a more realistic situation, in which the physical quantities fluctuate. The calculated hysteresis agrees with the prediction of the mean field theory. We have also found that the supersaturation should be changed within a period that is similar to the impurity adsorption time scale or slightly longer in order to observe obvious growth hysteresis. Measurem...

Numerical treatment for the point reactor kinetics equations using theta method, eigenvalues and eigenvectors

The point reactor kinetics model is a stiff system of linear/nonlinear ordinary differential equations. In fact, the numerical solutions of this stiff model need a smaller time step intervals within various computational schemes. The aim of this work is an accurate numerical solution without need to the smaller time step intervals. Theta method is the most popular, simplest and widely used method for solving the first order ordinary differential equations. In light of this fact, theta method is treated for solving the matrix form of this model via the eigenvalues and corresponding eigenvectors of the coefficient matrix. In this work, the matrix form of the stiff point kinetics equations with multi-group of delayed neutrons is introduced. The treatment theta method is applied to solve the stiff point kinetics equations with six groups of delayed neutrons. The performance of the treatment theta method is evaluated in several case studies involving step, ramp, sinusoidal and pulse reactivities. The results of the treatment theta method are more accurate than the theta method comparing with the conventional methods.

Control of coupling mass balance error in a process‐based numerical model of surface‐subsurface flow interaction

AbstractA process‐based numerical model of integrated surface‐subsurface flow is analyzed in order to identify, track, and reduce the mass balance errors affiliated with the model's coupling scheme. The sources of coupling error include a surface‐subsurface grid interface that requires node‐to‐cell and cell‐to‐node interpolation of exchange fluxes and ponding heads, and a sequential iterative time matching procedure that includes a time lag in these same exchange terms. Based on numerical experiments carried out for two synthetic test cases and for a complex drainage basin in northern Italy, it is shown that the coupling mass balance error increases during the flood recession limb when the rate of change in the fluxes exchanged between the surface and subsurface is highest. A dimensionless index that quantifies the degree of coupling and a saturated area index are introduced to monitor the sensitivity of the model to coupling error. Error reduction is achieved through improvements to the heuristic procedure used to control and adapt the time step interval and to the interpolation algorithm used to pass exchange variables from nodes to cells. The analysis presented illustrates the trade‐offs between a flexible description of surface and subsurface flow processes and the numerical errors inherent in sequential iterative coupling with staggered nodal points at the land surface interface, and it reveals mitigation strategies that are applicable to all integrated models sharing this coupling and discretization approach.

NEW EFFICIENT IMPLICIT TIME INTEGRATION METHOD FOR DGTD APPLIED TO SEQUENTIAL MULTIDOMAIN AND MULTISCALE PROBLEMS

The discontinuous Galerkin's (DG) method is an efficient technique for packaging problems. It divides an original computational region into several subdomains, i.e., splits a large linear system into several smaller and balanced matrices. Once the spatial discretization is solved, an optimal time integration method is necessary. For explicit time stepping schemes, the smallest edge length in the entire discretized domain determines the maximal time step interval allowed by the stability criterion, thus they require a large number of time steps for packaging problems. Implicit time stepping schemes are unconditionally stable, thus domains with small structures can use a large time step interval. However, this approach requires inversion of matrices which are generally not positive definite as in explicit shemes for the first-order Maxwell's equations and thus becomes costly to solve for large problems. This work presents an algorithm that exploits the sequential way in which the subdomains are usually placed for layered structures in packaging problems. Specifically, a reordering of interface and volume unknowns combined with a block LDU (Lower-Diagonal-Upper) decomposition allows improvements in terms of memory cost and time of execution, with respect to previous DGTD implementations.

Logic circuit design for high-speed computing of dynamic response in real-time hybrid simulation using FPGA-based system

One of the issues in extending the range of applicable problems of real-time hybrid simulation is the computation speed of the simulator when large-scale computational models with a large number of DOF are used. In this study, functionality of real-time dynamic simulation of MDOF systems is achieved by creating a logic circuit that performs the step-by-step numerical time integration of the equations of motion of the system. The designed logic circuit can be implemented to an FPGA-based system; FPGA (Field Programmable Gate Array) allows large-scale parallel computing by implementing a number of arithmetic operators within the device. The operator splitting method is used as the numerical time integration scheme. The logic circuit consists of blocks of circuits that perform numerical arithmetic operations that appear in the integration scheme, including addition and multiplication of floating-point numbers, registers to store the intermediate data, and data busses connecting these elements to transmit various information including the floating-point numerical data among them. Case study on several types of linear and nonlinear MDOF system models shows that use of resource sharing in logic synthesis is crucial for effective application of FPGA to real-time dynamic simulation of structural response with time step interval of 1 ms.