bluuebunny/crossref_metadata_2025 huggingface dataset:
A National Survey of Speech-Language Pathologists' Engagement in Interprofessional Collaborative Practice in Schools: Identifying Predictive Factors and Barriers to Implementation
Authors: Pfeiffer Danika L. , Pavelko Stacey L. , Hahs-Vaughn Debbie L. , Dudding Carol C.
Published: August 2019

Purpose

This study examined the models of collaboration used by school-based speech-language pathologists (SLPs) during the provision of special education services including factors predicting use of the interprofessional collaborative practice (IPP) model and barriers to collaboration.

Method

School-based SLPs responded to a survey on models of collaboration within their work setting. Anchored vignettes were created to determine their engagement in 3 different models (i.e., multidisciplinary, interdisciplinary, and interprofessional) used in the provision of special education services during evaluation and intervention. Predictive factors supporting and/or hindering the use of IPP were identified.

Results

Results demonstrated low percentages of school-based SLPs engaging in IPP during initial evaluations (8%), eligibility meetings (43%), and intervention sessions (14%). Three factors predicted use of IPP in schools: prior training in collaboration, years of experience, and educational setting. The most frequently cited barriers to SLPs' engagement in collaboration included time constraints/scheduling (48%), resistance from other professionals (23%), and lack of support from employers/administration (11%).

Conclusions

The results of the current study indicated that systemic change is needed at both the university and public school levels. At the university level, preprofessional students need collaborative learning opportunities that are integrated across programs and colleges. School-based SLPs and other education professionals could benefit from job-embedded learning focused on IPP to increase their knowledge and engagement in IPP and improve student outcomes.

Supplemental Material

https://doi.org/10.23641/asha.9340760
Combined probabilistic forecasting method for photovoltaic power using an improved Markov chain
Authors: Chen Bo , Li Jinghua
Published: August 2019

A novel combined probabilistic forecasting method based on an improved Markov chain for photovoltaics (PVs) to enhance the accuracy of probabilistic PV power forecasting is presented. First, a Markov chain (MC) forecasting structure combining precise factors is proposed that considers more influence factors beyond the statistical information of historical data as compared with conventional MCs. Rough set theory is then used to refine the major factors to quantify the influence of those factors. Furthermore, a k‐nearest neighbours algorithm is used to select similar samples for building an accurate forecasting model. Based on similar samples, the changing PV trends are more obvious than when using whole historical samples, thus further improving forecasting accuracy. Finally, the effectiveness and superiority of the proposed method are verified by comparing results from simulations with the results from competing methods for two cases using datasets from DESERT KNOWLEDGE AUSTRALIA Solar Centre and GEFCom2014. The simulation results show that the proposed method can provide probabilistic forecasting results with better performance, also, the proposed method can be adapted to various forecasting scenarios.
Toward an understanding of recent developments in RPL routing
Authors: Alsukayti Ibrahim S. , Alreshoodi Mohammed
Published: August 2019

The ability to enhance network routing for flexible support of different application requirements is essential to widen the horizon for the Internet of things (IoT) deployments. The Internet protocol (IP) version 6 routing protocol for low‐power and lossy networks (RPL) provides an effective routing solution addressing such a challenge. It realises flexible end‐to‐end IP routing that can be adapted to support different IoT applications. This is based on the concept of customisable objective functions (OFs), which facilitates application‐specific routing using a wide range of routing metrics. There are only two default OFs of basic routing metrics, which are specified by the Internet engineering task force for RPL. However, a number of others have been proposed by the network research community to address single‐ and multi‐objective RPL routing enhancement. These research proposals followed different methodological approaches and adopted a variety of routing metrics to achieve different optimisation goals. Up‐to‐date research efforts to improve RPL routing and topology optimisation have been reviewed, and recent RPL OFs and routing metrics in the literature have been discussed. The major aim is shedding light on relevant contributions to establish a firm understanding of recent RPL developments and outline plausible areas for follow‐up researches.
Data‐driven XGBoost‐based filter for target tracking
Authors: Zhai Bowen , Yi Wei , Li Ming , Ju Hao , Kong Lingjiang
Published: August 2019

In recent years, the data‐driven approach has been introduced in the field of target tracking as a powerful tool developing the end‐to‐end mapping relationship between input features and outputs. Typically, in data‐driven methods, neural networks serve as a supplement of traditional Bayesian filters for improved estimation accuracy. However, these hybrid methods are somehow complicated to realise. In this study, inspired by the idea of direct‐mapping from measurements to states, simpler method by developing a data‐driven XGBoost‐based Filter (DXGBF) is proposed. The DXGBF consists of four components, namely data generator, sliding window, centralisation strategy and XGBoost learner (XL). The data generator generates simulated data from the probabilistic model in the training phase. By intercepting the measurements, the sliding window enables DXGBF to track targets online. The centralisation strategy extracts the relevant kinematic information from different tracks that enables DXGBF to track randomly initialised targets. The XL is responsible for learning a function that mapping to estimate states. Simulation results show that the estimation accuracy of DXGBF is higher than those of Kalman filter, sampling importance resampling particle filter and the data‐driven random‐forest‐based filter.
Null widening method for conformal array based on covariance matrix enhancement
Authors: Wang Zhanze , Sun Yuze , Li Shuai , Yang Xiaopeng
Published: August 2019

Conformal arrays are widely used in various aircrafts since they do not affect the aerodynamic performance of the carriers. When conformal arrays are used to suppress fast‐moving interference, it is possible that the weight mismatches the data of measurement due to the perturbation of the interference location. Traditional null widening methods are based on linear or planar arrays and cannot be applied to conformal arrays directly. Therefore, a null widening method used for conformal arrays is proposed in this article. In the method, the spatial spectrum of the signal is first calculated, and then the convolution of spatial spectrum in the interference region and 2‐D window function is calculated to enhance the spatial spectrum. Next, the enhanced covariance matrix is calculated based on the convolution results. Finally, the sample matrix inversion (SMI) method is used to calculate the weight. This method can be used for common conformal arrays and can form two‐dimensional nulls in space. Based on the numeral simulation results, it is verified that the proposed method can form widened nulls and improve the robustness of interference suppression effectively.
The chemical structure of the very young starless core L1521E
Authors: Nagy Z. , Spezzano S. , Caselli P. , Vasyunin A. , Tafalla M. , Bizzocchi L. , Prudenzano D. , Redaelli E.
Published: August 2019

Context. L1521E is a dense starless core in Taurus that was found to have relatively low molecular depletion by earlier studies, thus suggesting a recent formation.

Aims. We aim to characterize the chemical structure of L1521E and compare it to the more evolved L1544 pre-stellar core.

Methods. We have obtained ~2.5 × 2.5 arcminute maps toward L1521E using the IRAM-30 m telescope in transitions of various species, including C17O, CH3OH, c-C3H2, CN, SO, H2CS, and CH3CCH. We derived abundances for the observed species and compared them to those obtained toward L1544. We estimated CO depletion factors using the C17O IRAM-30 m map, an N(H2) map derived from Herschel/SPIRE data and a 1.2 mm dust continuum emission map obtained with the IRAM-30 m telescope.

Results. Similarly to L1544, c-C3H2 and CH3OH peak at different positions. Most species peak toward the c-C3H2 peak including C2S, C3S, HCS+, HC3N, H2CS, CH3CCH, and C34S. C17O and SO peak close to both the c-C3H2 and the CH3OH peaks. CN and N2H+ peak close to the Herschel dust peak. We found evidence of CO depletion toward L1521E. The lower limit of the CO depletion factor derived toward the Herschel dust peak is 4.3±1.6, which is about a factor of three lower than toward L1544. We derived abundances for several species toward the dust peaks of L1521E and L1544. The abundances of most sulfur-bearing molecules such as C2S, HCS+, C34S, C33S, and HCS+ are higher toward L1521E than toward L1544 by factors of ~2–20, compared to the abundance of A-CH3OH. The abundance of methanol is very similar toward the two cores.

Conclusions. The fact that the abundances of sulfur-bearing species toward L1521E are higher than toward L1544 suggests that significant sulfur depletion takes place during the dynamical evolution of dense cores, from the starless to pre-stellar stage. The CO depletion factor measured toward L1521E suggests that CO is more depleted than previously found. Similar CH3OH abundances between L1521E and L1544 hint that methanol is forming at specific physical conditions in the Taurus Molecular Cloud Complex, characterized by densities of a few ×104 cm−3 and N(H2) ≳ 1022 cm−2, when CO starts to catastrophically freeze-out, while water can still be significantly photodissociated, so that the surfaces of dust grains become rich in solid CO and CH3OH, as already found toward L1544. Methanol can thus provide selective crucial information about the transition region between dense cores and the surrounding parent cloud.
Vibrations piezo-control of FGM beam in a thermal environment
Authors: El Harti K. , Rahmoune MED. , Sanbi M. , Saadani R. , Bentaleb M. , Rahmoune M.
Published: August 2019

An analytical method on the active vibration control of a functionally graded beam equipped with layers of piezoelectric sensors and actuators, in a thermal environment, is studied. The study based on Euler-Bernoulli theory and finite element method, applied to a flexible beam divided into a finite number of elements. The equations of motion are obtained by applying the principle of Hamilton. The structure is modeled analytically then numerically and the results of the simulations are presented to visualize the states of their dynamics.
Nonlinear multimodal electromagnetic device for vibration energy harvesting
Authors: Aouali K. , Zergoune Z. , Kacem N. , Mrabet E. , Bouhaddi N. , Haddar M.
Published: August 2019

A multimodal vibration energy harvesting in a periodic system is proposed. The multimodal approach and the nonlinearity are implemented in order to improve the performances of the studied device. The periodic system, based on electromagnetic transduction, consists of two weakly coupled magnets mechanically guided by two elastic beams. The quasi-periodic system is obtained by varying the mass of one of the moving magnets which leads to the vibration energy localization in regions close to the imperfections. This phenomenon is exploited to maximize the harvested energy. The mechanical nonlinearity is introduced by considering large displacements of the beams. The system is modeled by two coupled forced Duﬃng equations. The governing equations are solved using finite diﬀerence method combined with arc-length method. It is shown that the introduction of the nonlinearity leads to the enlargement of the bandwidth and the increase of the amplitude of the vibration.
Flutter and parametric stability analysis of axially moving composite graphene sheets
Authors: Azrar A. , Fakri N. , Aljinaidi A.A. , Azrar L.
Published: August 2019

The dynamic analysis instability of axially moving rectangular composite graphene sheets with visco elastic foundation is modeled and numerically simulated for various boundary conditions based on the differential quadrature method (DQM). The partial differential equation of motion based on the nonlocal elasticity and the Kirchhoff plate theories is given. The Galerkin and harmonic balance methods are used for the linear and parametric vibration analysis. The influences of nonlocal parameter, the fibers orientation and the viscoelastic foundation effects on the dynamic behaviors of the rectangular graphene sheet as well as the instabilities induced by the time dependent axial speed and its excitation frequency are investigated.
Probabilistic methodology for reliability assessment of electronic packages
Authors: Hamdani H. , Radi B. , El Hami A.
Published: August 2019

In the mechatronic devices, the finite element analyses are the most used method to determine time-dependent solder joint fatigue response under accelerated temperature cycling conditions, the deterministic analyses are the most used methods. However, the design variables show variability and randomness which will aﬀect the lifetime prediction quality. This paper focuses on solder joint reliability in tape-based chip-scale packages(CSP) with the consideration of uncertainties in material parameters.
A review and application of the failure criteria on a graphite epoxy under three-point bending test
Authors: Benbouras Y. , Bellahkim M. , Maziri A. , Mallil E. , Echaabi J.
Published: August 2019

The application of failure criteria are difficult partly because they are too various and must be validated by biaxial tests, which are expensive to be achieved. In this work, an analytical modeling based on a software program has been elaborated for application of the most general failure criteria and prediction of successive failure. Finally, the results obtained by this analytical modeling show a good correlation with those carried out by experimental study.
Modeling and simulation of an underactuated system
Authors: Nader K. , Sarsri D.
Published: August 2019

One of the most active research areas in mechatronic systems is the control of mechanical systems controlled by electronic systems using computer programs. These programs execute algorithms called control laws.

Our study focuses on the control of underactuated mechanical systems: Case of a reversed two-wheeled pendulum. It consists of developing a control law to stabilize this system. This class of system is rich in practical as well as theoretical applications (SEGWAY, Acrobot robots ...) and this is why the control synthesis for underactuated mechanical systems constitutes a very active research axis and still constitues an open domain for technological research.
The possibility of using a smartphone in a single plane rotor balancing
Authors: Ait Ben Ahmed A. , Touache A. , El Hakimi A. , Chamat A.
Published: August 2019

This paper aims to investigate and to describe the possibility of using the smartphones in the rotors balancing. It shows in the beginning a method to extract the necessary parameters for implementing the field balancing operation. An Android app was developed in order to record the smartphone sensors data of unbalanced rotors. The recorded data is then processed and used to identify the quantity of mass necessary and its position via a Matlab app. At the end, the smartphone results were compared by the exact results.
Optimization of elasticity of unidirectionnal non-overlapping fiber reinforced materials
Authors: Lakhal L. , Brunet Y. , Kanit T.
Published: August 2019

The aim of this work is to efficiently select samples of non-overlapping parallel fiber reinforced composites with regard to their elasticity and their fiber distribution in the composite cross-section.

The samples were built with the help of the simulated annealing technique according to chosen Radial Distribution Functions. For each sample the fields of local stresses were simulated by finite element method, then homogenized by volume averaging in order to investigate their elastic properties. The effect of RDF shape on elastic properties was quantified. The more the fiber distributions deviate from Poisson’s Law the higher the effective elastic moduli are. A method to select samples of real fiber reinforced composites according to their elasticity is proposed.
Vibration of composite thin-walled beams with variable open cross section by a high order implicit algorithm
Authors: El Kaimbillah A. , Bourihane O. , Jamal M. , Braikat B. , Mohri F. , Damil N.
Published: August 2019

In this work, we study the forced nonlinear vibrations with large amplitude and large torsion of composite thinwalled beams with open variable cross sections under external dynamic loads using a high order implicit algorithm. The used algorithm is based on the temporal and spatial discretizations, the homtopoy transformation, Taylor series expansion and the continuation technique. A 3D beam element with two nodes and seven degrees of freedom per node is adopted. The obtained results are compared with those computed by the industriel Abaqus code.
Analytical estimation of the reliability of wire rope based on cumulative damage
Authors: Wahid Achraf. , Mouhib Nadia. , Sabah Fatima. , Chakir Hamid. , Ghorba M.EL
Published: August 2019

The main objective of this manuscript is the elaboration of a behavior model of the cable system, designed to the prediction of its damage from the behavior of its components (wires, strands). This multi-faceted scale is based primarily on the results experiments of the central core and helical strands components. At first, a resolution numerical probabilistic equation for the different configurations was established by the programming the system resolution scheme obtained, Subsequently, each damage curves obtained, corresponding to a particular configuration has been interpreted independently.
Consideration of the reconfigurable aspect in evaluating predictive reliability of mechatronic system
Authors: Amrani Nabil B. , Sarsri Driss , Barreau Mihaela , Saintis Laurent
Published: August 2019

More than a multi-technology fusion, mechatronic systems are becoming more and more complex, these systems can be reconfigured with changes in the environment and states of the functional units, evaluating and improving the reliability of mechatronic system requires to take into account the reconfigurable aspect. This point has become a major challenge for reliability engineers during the design phase. Therefore their dysfunctional modeling is very diﬃcult. This communication presents an original proposed methodology for evaluating the reliability of mechatronic system with taking account the reconfigurable aspect. This reliability model integrates the change of the configuration related to the external and internal conditions.
Investigational methods for the modeling of infiltration process in the soil and the estimating the soil hydrodynamic parameters
Authors: Hachimi M. , Maslouhi A. , Tamoh K. , Qanza H.
Published: August 2019

Unsaturated zone in the soil generally plays an important role in the transfer of water and pollutants in the underground environment. In this context, the determination of the hydrodynamic parameters constitutes an essential step for any study of transfers of water and solutes in the unsaturated zone. The purpose of this article is the estimation the soil hydrodynamic parameters by the direct method and the inverse method, from the infiltration data by using the disc infiltrometer in the soil the basin Loukkos located in northern Morocco. Our results the numerical modeling reproduced correctly the experimental measurements. These results show that the inverse method remains a robust and accurate method for determining the soil hydrodynamic parameters compared to other conventional methods.
Magnetohydrodynamic effects on finite and infinite slider bearings
Authors: Mouda M. , Nabhani M. , El Khlifi M.
Published: August 2019

This paper presents a numerical investigation of lubricating slider bearings with conducting couple stress fluids using externally applied magnetics fields. The modified two-dimensional magnetohydrodynamic couple stress Reynolds-type equation is obtained. This governing equation is resolved numerically by using finite diﬀerence scheme, which involves the Gauss–Seidel method to compute the bearing characteristics. Numerical results using different considered values of the couple stress and Hartman number are presented. These results demonstrate that the transverse magnetic field and couple stress effects are significant.
Importance of rheology in the prediction of structural transition phenomena in geopolymer matrices loaded with phosphogypsum
Authors: Lahlou N. , Ouazzani Touhami M. , Hattaf R. , Moussa R.
Published: August 2019

Through a purely experimental approach, we proceed here to the description of the rheological behavior of the geopolymer matrices in the fresh state according to one or other of the parameters characterizing their formulation. This consolidates the different physicochemical techniques usually used for their characterization. This comes to allow us especially the definition of drafts for the implementation of empirical laws ensuring a better follow-up in the elaboration of these materials or even more optimization in their formulation. This description also allows us to follow the structural transition phenomena from the fresh state to the hardened state. We are particularly interested in demonstrating the impact of the addition of Phosphogypsum on the rheological behavior of geopolymers or on their kinetics of setting.
Data assimilation for control of a plane mixing layer
Authors: Kumar N. , Kerhervé F. , Cordier L.
Published: August 2019

The design of active model-based flow controllers requires the knowledge of a dynamical model of the flow. However, real-time and robust estimation of the flow state remains a challenging task when only limited spatial and temporal discrete measurements are available. In this study, the objective is to draw upon the methodologies implemented in meteorology to develop dynamic observers for flow control applications. Well established data assimilation (DA) method using Kalman filter is considered. These approaches are extended to both estimate model states and parameters. Simple non-linear dynamical models are first considered to establish quantitative comparisons between the diﬀerent algorithms. An experimental demonstration for the particular case of a plane mixing layer is then proposed.
Permeation of Toluene into (Polypropylene/Acrylonitrile-co-butadiene Rubber) immiscible blend
Authors: Hairch Y. , El Afif A.
Published: August 2019

This study examines the unsteady permeation process of a solvent through a mixture of two immiscible polymers with a complex dividing interface. The mathematical model consists of three nonlinear PDEs that incorporate the coupling arising between mass transport and the dynamic changes of the blend internal structure. In addition to the solvent mass fraction c, we choose, as additional state variables, the conformation tensor m to characterize the macromolecular chains while the embedded interface is described by a scalar Q and a traceless second-order tensor q respectively for the size and shape anisotropy of the area. We extend the Fick's first law by two new non-Fickian terms. Among the obtained results, we present the transient permeation mass flux profiles of toluene through PP/NBR blend system at different compositions and predict the corresponding time lag.
Synthesis study on thermal insulation improvement in construction materials
Authors: Lachheb A. , Kabiri M.R. , Saadani R.
Published: August 2019

Improving thermal insulation of buildings envelopes can reduce their energy consumption and related CO2 emissions considerably. Searching for new and innovative insulation materials is therefore a key challenge. This work presents a synthesis study on series of experiments showing the addition effect of different additives on plaster and cement composite thermal properties. The results obtained using the box method show a significant improvement of thermophysical properties with the increase of additives incorporation rate. From an energy and environmental point of view, the results of the annual simulations carried out for a typical building located in Meknes indicated that the use of the proposed materials has economic and environmental benefits.
Computational parametric study of latent melting heat storage
Authors: Faraji Hamza , Faraji Mustapha , El Alami Mustapha
Published: August 2019

This paper presents a numerical study of the melting process of a phase change material for the cooling of a heat source “electronic component”. The latter is protruding and mounted on a substrate "motherboard" in the center of the bottom wall of a rectangular enclosure. The enclosure is filled completely with PCM. A 2D non-dimensional mathematical model is developed based on the conservation equations of mass, momentum and energy. The enclosure aspect ratio ‘A’ effect on the thermal and hydrodynamic behavior of the PCM-based heat sink is investigated.
Numerical Study Of Thermal Behavior Of Anisotropic Medium In Bidirectional Cylindrical Geometry
Authors: Idmoussa Rabiâ , Hanchi Nisrine , Hamza Hamza , Lahjomri Jawad , Oubarra Abdelaziz
Published: August 2019

In this work, we investigate the transient thermal analysis of two-dimensional cylindrical anisotropic medium subjected to a prescribed temperature at the two end sections and to a heat flux over the whole lateral surface. Due to the complexity of analytically solving the anisotropic heat conduction equation, a numerical solution has been developed. It is based on a coordinate transformation that reduces the anisotropic cylinder heat conduction problem to an equivalent isotropic one, without complicating the boundary conditions but with a more complicated geometry. The equation of heat conduction for this virtual medium is solved by the alternating directions method. The inverse transformation makes it possible to determine the thermal behavior of the anisotropic medium as a function of study parameters: diagonal and cross thermal conductivities, heat flux.
Effects of Rheological Parameters of a Viscoplastic Fluid on Peristaltic Pumping in a Cylindrical Tube
Authors: Rachid H. , Ouazzani Touhami M.
Published: August 2019

In this paper, we study theoretically the peristaltic transport of a generalized four-parameter plastic fluid in a circular cylindrical tube. The present fluid model is presented for the rheological characterization of inelastic fluid foods. Long wavelength and low Reynolds number approximations are taken into account to get solution. The effects of embedded parameters on pressure rise, frictional force and especially on the mechanical efficiency have been numerically displayed and physically discussed.
Study of the tooth contact for high contact ratio spur gears with long tip relief
Authors: Pedrero José I. , Pleguezuelos Miguel , Sánchez Miryam B.
Published: August 2019

Profile modifications are commonly used to avoid shocks between meshing gear teeth produced by the delay of the driven gear, and the subsequent sooner start of contact, due to the teeth deflections. A suitable tip relief at the driven tooth shifts the start of contact to the proper location at the theoretical inner point of contact. The shape of the relief governs the loading curve of the tooth pair, while the length of relief determines the intervals in which this actual loading curve differs from the theoretical one of unmodified teeth. As at least one tooth pair should be in contact at the unmodified involute profile interval, the length of modification should be smaller than the length of the intervals of two pair tooth contact; otherwise, a shock at the end of contact of the previous pair is unavoidable. However this problem does not occur for high contact ratio spur gears, in which at least two couples of teeth are in contact at any moment. In this work, a study on the load sharing and the quasi-static transmission error for high contact ratio spur gears with long profile modification has been performed, and a model for the tooth contact has been developed.
Modeling and optimization of the delivery fluctuation of gear pumps
Authors: Tsolakis Efstratios , Tzanopoulos Antonios , Vasileiou Georgios , Rogkas Nikolaos , Spitas Vasilios , Zalimidis Pavlos
Published: August 2019

Presented work aims to minimize the delivery fluctuation of a gear pump through geometrical optimisation of the tooth flank. Therefore, instead of examining various configurations, which would reduce the flow ripple ad hoc, the current study suggests the dependence the delivery fluctuation to the tooth flank profile. Taking into account the secondary derivative of the tooth profile, the optimisation process is able to also affect the secondary delivery fluctuation, which is connected to the compression of the fluid over the meshing cycle. Bezier-Bernstein polynomial curves were used to model the tooth flank in order to satisfy the objective function. A dependency between the total length of the path of contact curve and the flow ripple was found. It is stated in this work that for every design point on a closed path of gear set, there is a threshold on the contact length, over which the resulted flow ripple starts to deviate from the optimum value. That conclusion was used to further enhance the optimisation algorithm. The presented optimum gear profile design was evaluated through a comparative study between every design point and the corresponding solution of the existing state of the art in terms of delivery fluctuation.
A heuristic method for transmission design
Authors: Ivanov Viktor , Dimitrov Lubomir , Ivanova Svitlana , Naleva Galyna
Published: August 2019

The application of heuristic methods in the design of transmissions is investigated. The structure of heuristic methods is revealed and the heuristic techniques that compose them are established. These techniques are combined into one generalized method, which allows replacing all the considered methods. A heuristic method specially allotted for the design of transmission is also developed. This method contains, among other things, the following heuristic techniques. Search for all possible variants of elements location corresponding to one of the same graph. Introduction nodes to the graph that corresponding certain function, for the implementation of which a node can be added to the design or vice versa, a node can be removed from the design, and the function it has implemented will be implemented by other elements.The advantages of a heuristic search on the example of designing a double row thrust bearing are evidenced. The bearing contains a node through which the speed of the intermediate ring is always equal to half the speed of the shaft. Due to this, the distance that the rolling element path is reduced, and the bearing has greater durability.
Interference of the profiles when meshing internal straight splines with gear shapers
Authors: Marinov Svetlin , Alipiev Ognyan , Uzunov Toni
Published: August 2019

The possibilities for cutting internal straight splines with gear shapers by internal meshing, without interference between meshed profiles, are shown in this article. The interference is an undesirable occurrence whereby the straight profile of the splines and the instrumental contour intersect with each other beyond the meshing line. As a result, the shaper teeth cut off a part of the splines’ straight profile and they are made with some defects. The research shows that the undesirable interference depends directly on the parameters of the splined opening and the number of shaper teeth. Also, it is determined that the interference can be avoided by reducing the number of shaper teeth and the height of the splines. Furthermore, the maximum number of shaper teeth for all standard splines for which the interference is absent, are defined in the article. The results are confirmed by computer simulations of the corresponding instrumental meshing.
Multi-criteria optimization of tracked vehicle transmissions
Authors: Ustynenko Oleksandr , Bondarenko Oleksiy , Klochkov Illia , Serykov Volodymyr
Published: August 2019

The article is devoted to the problem of computer modeling of rational design of tracked vehicle transmissions with multiple criteria. The problems of finding optimal geometric parameters that satisfy several quality criteria. All the complexity of the layout and the relationship of the parameters make difficult their choice, which is simplified when using approaches of mathematical optimization. Using the famous pseudo-random method LPτ-search with the author's modification made it possible to avoid problems associated with the discreteness and the number of parameters. The main optimization criteria for transmission are minimum center distance, minimum length, minimum mass, and maximum uptime probability. To solve this problem, the problem was formulated and design parameters with constraints were specified, criteria were recorded and a transformation from multicriteria to a single criterion was proposed. The approach is based on analysis of test points that obtained using LPτ-search, and further processing of the information received. The approach of transformation from many criteria to one is proposed by introducing the scale of importance by the designer and assigning the importance of each of the criteria, finding the desired solution for each trial point of relative offset, which is proposed to be used as a unifying criterion. Basic schemes and flowcharts of the algorithm elements are provided. The implementation of the computer model was carried out in the Delphi 7 environment.
An algorithm for topology optimization of gear reducer housing elements
Authors: Slavov Stoyan D. , Konsulova-Bakalova Mariya Iv.
Published: August 2019

In recent years, topology optimization methods are becoming more widely used in many engineering fields, and they are already being successfully integrated at the design stage of the different types of products. An active field of research in this area is the definition of appropriate constraints in topology optimization models in order to facilitate the production of the optimized objects. An algorithm for topology optimization of housing elements from gear reducers by using the capabilities of CAD-CAE topology optimization software is presented in the current work. The purposed algorithm is taking into account the resulting loads during operation of the reducer, the geometrical and manufacturing constraints of the production process of these housing elements. Obtained results from conducted Taguchi experimental study to investigate the impact of some topology optimization control parameters over optimized 3D-model also are shown and discussed. Conclusions on the applicability of the algorithm have been made.
Oscillation damping in the powertrain unit of transport vehicles
Authors: Taratorkin Alexander , Derzhanskii Viktor , Taratorkin Igor
Published: August 2019

The paper presents the results of an analytical experimental research of conditions for excitation of oscillatory processes in steady-state conditions and in the process of starting-up an engine equipped with a modern Common Rail fuel supply control system. Based on the results of mathematical simulation, the dependence of the dynamic torque amplitude on boosting acceleration during engine start-up and on the parameters of the elastic-dissipative coupling (connection) of the engine with the transmission is analyzed. It establishes the rationale for a possibility of optimizing the fuel supply system control algorithms for a modern diesel engine, taking into consideration the dependence of the process on the properties of the transmission and the peculiarities of its operation.
The Influence of the Bearing Lifetime on the Performance of Universal Gear Drives with High Gear Ratio Values
Authors: Rackov Milan , Kuzmanović Siniša , Knežević Ivan , Čavić Maja , Penčić Marko , Stefanović Darko , Starzhinsky Victor E. , Shil’ko Sergey V. , Algin Vladimir B.
Published: August 2019

The problem of defining the load (nominal torque on the output shaft - T2N) of universal gear drives depending on the size of the gear ratio is analysed in this paper. It is logical that the load capacity of gear drive depends on the weakest gear component. Since the gears are the most expensive components of gear unit, it tends to maximize their performance. However, for low gear ratio, i.e. for high speeds, the bearings often limit their load capacity since the same bearings are used in all transmission ratios because it is not practiced to oversize the bearings at low speeds. Nowadays, when high values of gear ratio are used, it is interesting to consider the dependence of the nominal torque at the output regarding to gear ratio and operating life of the unit.
Analysis of the cutting moments for the selected chopper’s cutting drums constructions
Authors: Zastempowski Marcin , Bochat Andrzej
Published: August 2019

The analysis of the drum cutting assembly’s movement dynamics is presented in the article. The derived mathematical dependences describing the dynamic load, may be used at the stage of designing of these types of cutting assemblies and of their drive systems. The simulation calculations conducted on the derived mathematical dependences, allowed the authors to develop a computational tool for quick identification of the demand for power and forces operating in the drum cutting assemblies under the impact of changes in characteristic input quantities.
The simulation of the service life of the rotary shaft of a centrifugal pump
Authors: Isametova Madina , Nussipali Rollan , Isametov Aysen
Published: August 2019

The article describes an automated calculation of such an essential part of a centrifugal pumps the rotor shaft, so the highest level CAD NASTRAN system PATRAN module was used for the analysis. The computational mechanical scheme was drawn up, the axial and radial force acting on the impeller and the pump shaft were determined. The stress for the maximum feed case are determined. The results of the automated strength calculation were used for further analysis of the service life of the rotor shaft of a centrifugal pump. A computer technique for determining the service life of the shaft is given, taking into account the technological, mechanical conditions of operation and taking into account the projected service life equal to the lifetime of the uranium well. Using the automated MSC FATIGUE module, the number of loading cycles was determined, the service life safety factor was determined, which showed the efficiency of the pump throughout the entire operating time of the uranium well.
The use of pneumatic cylinders with a return spring to compensate for balance losses in mechanical regenerative drives for reciprocating movements
Authors: Zhao Wen , Zhavner Victor Leonidovich
Published: August 2019

Mechanical spring drives with energy recovery are designed to produce return-rotational movements in various technological equipment and reduce energy costs by several times compared with traditional electromechanical, hydraulic and pneumatic drives. The use of pneumatic motors in spring drives to compensate for dissipative losses, fixing the drive in extreme positions and the primary charging of spring batteries is considered. The class of tasks in which spring drives with energy recovery are created using only pneumatic cylinders with return springs is highlighted. This study examines mechanical spring drives with energy recovery, based on nonlinear spring batteries with spring preload in the middle position of the output link. The use of pneumatic actuators with return springs in mechanical drives based on linear spring batteries with two springs is proposed. Mechanical spring drives with energy recovery are designed to produce return-rotational movements in various technological equipment and reduce energy costs by several times compared with traditional electromechanical, hydraulic and pneumatic drives. The amount of energy expended in spring recuperative drives is actually determined by the energy expended on compensating for dissipative losses in kinematic pairs. The results of the study allow the designers of such drives to consciously approach the choice of their schemes and design parameters.
Durability Investigation of plastic gears
Authors: Hlebanja Gorazd , Hriberšek Matija , Erjavec Miha , Kulovec Simon
Published: August 2019

Plastic materials can be used for various gears and gear mechanisms due to their qualities, like wear resistance when running dry, low noise, vibration damping, low inertia, low manufacturing cost, etc. However, they also expose with temperature connected problems like rapidly decreasing load, thermal expansion and accuracy of moulded gears. Therefore, it is a challenge to produce gears with adequate accuracy and durability to serve in contemporary mechatronic applications in automotive, in medical equipment and many other industries. Such materials are POM, PA6, PA66, PEEK, reinforced plastic materials, etc. and steel. Proper combination of such materials can result in long and reliable operation of such mechanisms. On the other hand, S-gears offer improved properties in comparison to involute (Egears), which essentially comprise lower contact pressure, less sliding and frictional losses, stronger root and improved oil film when lubricated. The goal is development of advanced power transmission drive components made of polymers. So, a material database, a testing system and testing procedures with varying material combinations and gear pairs according to VDI are necessary to support a designer in proper decisions. Some material properties, especially fillers are presented. Furthermore, testing facilities, gears and some results are discussed.
Performance assurance of mechanical engineering construction in the existence of cracks
Authors: Velikanov Nikolay , Koryagin Sergey , Sharkov Oleg
Published: August 2019

The purpose of this paper is to consider the development of engineering ways of preventing the further development of through cracks in the sheet elements of the complex technical structures. The latest individual approach to the assessment and assurance of performance of structures with cracks, which is to take into account the features of their operation, has been applied in this work. Preference is given to methods that reduce the concentration in the danger zone. Studies have shown that the most appropriate and effective ways to prevent the further development of a through crack are the structural methods and combinations of the structural and technological methods. The effectiveness of these methods was determined on the basis of the strength uniformity approach of structural elements with a crack. The criterion of strength uniformity from the position of fatigue and brittle strength with an error on the safe side is the value of theoretical stress concentration factor [K]. The[K] value was made on the basis of generalization and analysis of cases of crack formation, the results of tests of typical components of hull structures and welded joints. The safe concentration of stresses near the holes of various purposes in the members of the machine-building structures is in the range from 2 to 4. Taking into account the relevant requirements for the ratio of the radius of curvature and the width of the cutout, we obtain 3.5. The value of the criterion К1 is determined by the ratio of the calculated crack length to the diameter of the hole drilled at its ends and the location of the crack.
Numerical simulation of elastoplastic contact of heavy-loaded spiroid gears
Authors: Sannikov Alexander
Published: August 2019

The paper presents the analysis of heavy-loaded low-speed multi-pair spiroid gears under the effect of elastic contact, bending and shearing, and elastoplastic contact interaction of spiroid gearwheel teeth and spiroid worm threads. The main stages of the developed algorithm for analysis of load distribution and plastic strain of flanks with account of elastic and elastoplastic contact conditions, multi-pair contact and macro-roughnesses on flanks are described in short. At elastoplastic contact the zones of plastic contact on flanks of spiroid gearwheel teeth are determined and the value of plastic strain is analyzed. The flanks of the spiroid gearwheel teeth and worm threads are represented in the algorithm as the set of segments (cells) with coordinates of centers determined with account of the analyzed factors that influence the load distribution in spiroid gearing. These factors are the errors of manufacturing and (or) assembly, micro-roughnesses, and deformations of spiroid gear supports. The paper gives the numerical results of research of the real spiroid gears of gearboxes for pipeline valves (PV) at elastic and elastoplastic contact represented as summary tables and diagrams of contact stress distribution along contact areas and of plastic strain, that show the workability of the algorithm. The presented numerical results of the algorithm functioning are well agreed with the experience of operation of spiroid gears and can be applied for analysis of load-carrying capacity of spiroid gears.
Tribological researches of triboelements topography of hob milling process of cylindrical gear serration
Authors: Sovilj Bogdan , Sovilj-Nikic Sandra , Javorova Juliana
Published: August 2019

Hob milling process is one of the most important links in the chain of machining because productivity, final geometrical accuracy and gear cutting are very dependent on it. The quality of the machining of gear serration is one of the conditions for achieving the required quality of the work-piece. In this paper the methodology for the identification of topography of tool teeth and gear serration produced by uncoated and coated model and real hob milling tool is presented.
Examination of a repetitive process control system
Authors: Nikolova Nina G.
Published: August 2019

In the present work, the application of repetitive filters in the robust process control systems is examined. The functionality of the proposed system and the improved performance, robust performance and filtering properties has been proven.
A study on surface roughness of workpiece when grinding SKD11 and SUJ2 steels using Al2O3 and CBN wheels
Authors: Dung Hoang Tien , Trung Do Duc , Van Thien Nguyen , Ky Le Hong
Published: August 2019

This paper presents a study on surface roughness of workpiece when grinding SKD11, SUJ2 steels using Al2O3 and CBN grinding wheels. The method on modeling and predicting of surface roughness of workpiece in the grinding theoretical research was applied. However, when applying this method, it is necessary to identify the value of the roughness adjust factor in practical case. In this paper, this factor was found by experimental process when surface grinding SKD11 and SUJ2 steels by Al2O3 and CBN wheels. It helps values of calculating surface roughness to be similar to experimental datas.
GA Tuning PID Controller Based on Second-order Time-delay Industrial System
Authors: Wang Zhi , Ran Xiangtao , Zhao Bin , Zhao Jie
Published: August 2019

For a typical second-order time-delay system model, an intelligent genetic algorithm is used to initially optimize the initial parameters of the PID controller, and a step response curve of the system is obtained, and the performance index is compared with performance indexes obtained by other optimization methods. The results show that the GA optimization method is more robust.