Rigid Modes Research Articles

Micro Terrain Construction of Service Facilities along the Expressway

The service facilities along the expressway are designed to meet the needs of drivers and passengers, which is directly related to the convenient travel of the general public. In order to break through the rigid construction mode of expressway service facilities, this paper analyses the micro terrain design and construction of different types of expressway service facilities, and discusses the micro terrain construction of expressway service facilities, so as to improve the view of the landscape and the sense of physical and mental pleasure of the drivers, passengers and service personnel, eliminate security risks and improve service efficiency.

Anharmonicity and scissoring modes in the negative thermal expansion materials ScF3 and CaZrF6

We use a symmetry-motivated approach to analysing X-ray pair distribution functions to study the mechanism of negative thermal expansion in two ReO$_3$-like compounds; ScF$_3$ and CaZrF$_6$. Both average and local structure suggest that it is the flexibility of M-F-M linkages (M = Ca, Zr, Sc) due to dynamic rigid and semi-rigid "scissoring" modes that facilitates the observed NTE behaviour. The amplitudes of these dynamic distortions are greater for CaZrF$_6$ than for ScF$_3$, which corresponds well with the larger magnitude of the thermal expansion reported in the literature for the former. We show that this flexbility is enhanced in CaZrF$_6$ due to the rock-salt ordering mixing the characters of two of these scissoring modes. Additionally, we show that in ScF$_3$ anharmonic coupling between the modes responsible for the structural flexibility and the rigid unit modes contributes to the unusually high NTE behaviour in this material.

Decomposition and Aggregation-Based Real-Time Analysis of Assembly Systems With Geometric Machines and Small Batch-Based Production Tasks

Steady-state analysis on production systems, especially serial lines with rigid production mode, have been carried out in a large amount of research literature. With the development of the advanced manufacturing technologies, as well as the national strategies, for example, Made in China 2025, real-time performance evaluation, prediction, production management, and efficient control of systems with flexible production mode are gradually becoming important issues. Under the assumption of assembly systems with small batch-based production tasks, we develop a mathematical model for the real-time performance analysis of such systems with the geometric machine reliability model, which is applicable in many manufacturing environments. The formulas for real-time performance analysis are derived first using the Markovian approach for three-machine assembly systems. Then, based on the idea of decomposition and aggregation, an algorithm with high accuracy and efficiency for system real-time performance approximation is proposed. Finally, the decomposition and aggregation-based real-time analysis approach is extended to the generalized assembly systems. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —As the concept of manufacturing intelligence being proposed and promoted, system flexibility appears frequently in production in recent years. A flexible production refers to the implementation of small batch-based production with multitype of products on the same production line, by quick setup or machine adjustments. The steady-state analysis method that is traditionally used might be not applicable in this case since most of the production process is in transient state. An approximation-based analytical method, for real-time performance evaluation of assembly systems with small batch-based production tasks and with machines having the geometric reliability model, is proposed. The algorithm developed in this article can be utilized by production managers and engineers, with which the real-time performance of the systems can be predicted with high accuracy. It can also provide assistance for decision-making on activities of production control.

On the Principle and Applications of Conditional Disturbance Negation

It is commonly believed that observer-based compensation is an effective way for disturbance rejection. A less talked about fact is that such disturbance rejection control technique may also degrade control performance. In this article, we present a typical cross-coupling system to reveal this problem and, more importantly, propose a new design principle of conditional disturbance negation (CDN) to eliminate its potential drawbacks of disturbance observer-based compensation. Qualitative analysis is first given for a general form of such cross-coupling systems, indicating the necessity of CDN. The analysis and control design principle of CDN is then exemplified through two applications. A numerical linear application produces abundant quantitative results through the powerful transfer function and frequency domain tools. A more complex nonlinear flexible air-breathing hypersonic vehicle application shows how conventional compensation deteriorates the couplings between rigid and flexible modes, and validates the effectiveness of CDN through comprehensive model analysis and simulation results. The proposed CDN design principle also arouses awareness of the importance of: 1) understanding the characteristics of the plant to be controlled and 2) recognizing the critical role the information plays in engineering practice.

Electronic Structures and Lattice Dynamics of Layered BiOCl Single Crystals.

BiOCl has recently elicited intense interest for its excellent photochemical catalysis, energy conversion, and photodetection performance. In this Letter, we systematically investigate BiOCl electronic properties, lattice dynamics, and structural stability. From first-principles calculations, bulk and monolayer BiOCl have ultraviolet indirect band gaps around 3.6 eV, consistent with reflection spectroscopy measurements. The large spin-orbit coupling effect of the Bi atom makes the lowest conduction band near the Z point in the Brillouin region move down 230 meV. However, because of the symmetrical crystal potential, BiOCl has no strong Rashba effect. We further observed all 6 BiOCl Raman-active modes with the lowest-frequency rigid layer in-plane vibrational mode at 63 cm-1, consistent with our calculations. Up to 500 K or down to monolayer thickness, the crystal structure of BiOCl remains stable. Our work provides detailed information on BiOCl electronic and vibrational properties and stability up to high temperature or down to monolayer, identifying it as a promising layered material for further nano-optoelectronic applications.

Tilts and shifts in molecular perovskites

A survey of the rigid unit modes in molecular perovskites is presented, showing how the prevalence of conventional tilts, unconventional tilts and columnar shifts vary across the different classes of molecular perovskites.

Дослідження січних модулів листяних та хвойних порід деревини з різним показником вологості

Most wood-based materials, elements, products and structures work in both non-aggressive and aggressive environments. Aggressive also include environments with high humidity. Humidity of wood in such conditions is higher than standard (in an unprotected condition), that is more than 12&nbsp;%. The humidity content of wood directly affects its physical and mechanical properties, in particular the initial modulus of elasticity and the modulus of deformation. The method of experimental researches of wooden prisms in the size of 30´30´120 mm on compression along fibers at a rigid mode of loadings (on increase of movements of a press of the testing machine) is in detail given. The following species of wood were tested: coniferous species — larch, pine, spruce; deciduous — birch, alder, ash. The trees from which the samples were made were grown, in particular, pine, spruce — in the forests of Rivne region; birch, alder, ash — in the forests of Volyn region; larch — in the forests of Ivano-Frankivsk region. The tested wood had a humidity content of 30&nbsp;%, 21&nbsp;%, 12&nbsp;% at the age of 60 years and grade without defects and damage. Wood blanks were pre-dried in the laboratory to an average humidity of 30&nbsp;% and in special drying chambers to a humidity of 21&nbsp;% and 12&nbsp;%. The humidity of the wood was controlled using a humidity meter MD-814. Experimental studies were performed on a servo-hydraulic testing machine STM-100 with an automated control and data recording system. On the basis of experimental researches diagrams (secant modulus—stress level) of continuous deciduous (birch, alder, ash-tree) and coniferous (larch, pine, spruce) breeds of wood were constructed. The initial modulus of elasticity and modulus of deformation of different types of wood in the range from 30&nbsp;% to 12&nbsp;% of humidity were obtained experimentally and theoretically. It is established that with a decrease in humidity from 30&nbsp;% to 12&nbsp;%, the strength of wood of all species increases the initial modulus of elasticity and the modulus of deformation increases significantly

Super-hard modes of capacitor welding during the formation of joints from dissimilar materials

The article provides an analytical overview of ways to contact the capacitor welding. Using rigid modes effects on the bonding region in most cases causes the formation of a contact during the crystallization in the liquid phase, which is highly undesirable when connecting non-ferrous metals and their alloys. Forming permanent joints in the liquid phase facilitate processes atomic hetero diffusion or reactive diffusion, which intensifies the nucleation of intermetallic phases.The use of high-voltage capacitor welding with an induction-dynamic drive allows minimizing the processes of nucleation of intermetallic phases due to the use of super-hard modes of action on the connection zone when converting the stored energy in capacitor banks to synchronous thermodynamic effects.The proposed methods of high-voltage capacitor welding for joining dissimilar alloys and powder compositions are considered, the physical nature of the process and the kinetics of the impact are described.The results of the energy-spectral analysis of compounds in a heterogeneous combination of AlMg2.5, Cu01, Br63, and HfC alloys showed the absence of atomic hetero diffusion or reactive diffusion and the formation of compounds during high-voltage capacitor welding in super-hard modes in the solid phase.

Rose pattern for heliostat field optimization with a dynamic speciation‐based mutation differential evolution

Concentrated solar power technology is one of the most promising technologies in energy field. Arguably, the heliostat field layout is a crucial component in solar power tower system. Numerous studies have been developed for heliostat field optimization. However, most of the existing layouts which utilize radial staggered patterns are based on only two or four variables, leading to relatively rigid modes due to strong configuration constraints. In this article, we propose a new method called rose layout, which divides the regular radial staggered pattern into six sectors and they are optimized separately. Therefore, the radial increments between consecutive rows are not restricted to zones or rows, only relevant to which sector they belong to. This arrangement is more flexible and also efficient. Furthermore, a new differential evolution algorithm with a dynamic speciation-based mutation strategy (DSM-DE) is developed to solve this high-dimensional problem. In order to validate the proposed rose pattern and DSM-DE, three sets of comparative experiments were carried out. The first set of tests were operated with the conventional four optimization variables, the second series optimized total 43 radial increments between consecutive rows, whereas the third series employed the rose layout. All sets of cases were optimized by four competitive variants of differential evolution algorithm, ie, JADE, SHADE, EB-LSHADE, and DSM-DE. Experimental results verified that the rose layout can obtain higher overall optical efficiency and less land coverage than previous methods and DSM-DE is superior to other DE variants for this high-dimensional problem. The heliostat field studied in this article is simulated in Qinghai, China. By integrating rose layout with DSM-DE, the field unweighted efficiency progressed from 44.386% to 53.972%, and the annual weighted efficiency reached 59.091%, which was 0.318% higher than the 43-variable optimization.

Revising the penetration behavior of concrete-like and metal-like materials against the rigid projectile impact

Many studies indicate that projectile deceleration exhibits a quasi-constant behavior in the tunneling penetration stage of the rigid penetration mode for both metal-like and concrete-like materials. As to the issue, in the present paper the penetration process under the rigid penetration mode was revised, where a two-phase penetration theory is proposed including the ‘Squeeze and Push’ penetration phase and the dynamic spherical cavity expansion penetration phase. When the striking velocity is below the critical striking velocity, the ‘Squeeze and Push’ effect is generated since the cavitation size is less than the projectile diameter, where the quasi-static term overshadows the dynamic term. The interaction from the surface friction between projectile and target and the penetration force due to the main quasi-static term contributes to the occurrence of the quasi-constant phenomenon. Conversely, when the striking velocity is above the critical velocity, the penetration enters into the dynamic spherical cavity expansion penetration phase, the accompanying feature is that the tunnel becomes large beyond the projectile diameter, meanwhile the friction effect between the projectile and target disappears, the deceleration shows a well-defined peak with the rise of the striking velocity. Following the features, semi-empirical formulas are obtained. Finally, the semi-empirical formulae are discussed and validated by comparing with the typical penetration experiments including concrete-like and metal-like materials.

Numerical study on the influence of suspension damping on the bogie vertical vibration

The paper presents a study on the influence of suspension damping (SD) on bogie vertical vibrations generated by vertical track irregularities. The study is based on the results of the numerical simulations developed on the basis of a linear model with seven-degree of freedom of the bogie-track system, that takes into account the rigid vertical vibration modes of the bogie – bounce and pitch, vertical displacements of the wheels and rails, and the wheel-rail contact elasticity. The bogie vibration behaviour is assessed based on the dynamic response of the bogie chassis, expressed as the power spectral density of the vertical acceleration (PSD acceleration) at three reference points – at the bogie chassis centre and over the axles, and root mean square of vertical acceleration (RMS acceleration). It is highlighted the main characteristics of the bogie vibration behaviour according to the SD in correlation with the speed and quality of the railway track.

Active oscillation control of electric vehicles with two-speed transmission considering nonlinear backlash

The nonlinear backlash can influence the driveability of the electric driveline due to the lack of the traditional clutches and torsional damper devices. During the stand-start, regenerative braking and gear shift process of the electric drive system equipped with two-speed transmission, the request of transient traction motor change will transverse the powertrain backlash, which will excite the driveline oscillations coupled to the first rigid mode of the entire powertrain, referred as shuffle or shunt. These vibrations are transmitted to the chassis, causing deterioration in passenger comfort. In this paper, the nonlinear driveline model including the traction motor, half shaft, driveline backlash, and car wheel are developed. Then, dual extended Kalman filter method is employed to estimate vehicle mass and half shaft torsional angle of the proposed driveline. Based on the estimated information, a hierarchical architecture of the active oscillation compensation is proposed to alleviate the vibration in both contact and backlash mode. The experimental results show that the estimation method is effective and the vehicle shuffle can be significantly decreased by the developed control algorithm.

Characterization of the behaviour of welded steel joints through modal components

ABSTRACTThe analysis and design of joints constitutes one of the most important aspects when designing steel structures. It is a common practice to model the joint behaviour by zero‐length rotational springs placed between the beam and corresponding column, or by mechanical models composed of springs and rigid bars. These models have serious limitations when considering the interactions between the shear, bending and axial forces and deformations of the panel zone.In this research, a new approach based on the characterization of modal components is presented. First, the steel joint is modelled as a cruciform finite element of 12 degrees of freedom. Then, the stiffness matrix is decomposed in eigenvectors and eigenvalues. The eigenvectors provide information about the joint deformation modes, while the eigenvalues give information about the stiffness associated with each mode. To identify the main modes and their characteristics, a parametric study has been carried out for welded joints with and without stiffeners. For both cases, all combinations of IPE 120 to IPE 600 profiles for beams and HEA 160 to HEA 1000 profiles for columns have been studied. The only restraint imposed in the combination process is that the beam width be smaller than the column width.First, the cruciform finite element stiffness matrices are obtained. Subsequently, a spectral decomposition is carried out using MATLAB, and then Python scripts are developed to classify the modes and eigenvalues. The statistical analysis of the results shows that after removing the three rigid solid modes the most relevant deformation modes are the shear and the two possible bending modes including their interaction. The remaining six modes correspond to deformation modes with high stiffness values that are not excited under common loading situations.

A Survey on the Educational Benefits of Compulsory Education in B Land of Tibet

The outcome of education includes students’ academic achievement and social adaptability. In order to explore the current situation and factors of outcome of education in the compulsory education stage of Tibetan agricultural and pastoral areas, junior high school students from 5 counties of B agricultural and pastoral areas are selected as survey objects. A research method combining questionnaires and interviews was conducted to investigate. The study found that: the local curriculum resources are estranged from the students’ life experience, the difficulty of understanding the teaching language and the rigid management mode are the reasons for the low outcome of education in the agricultural and pastoral areas.

Effect of train speed and track geometry on the ride comfort in high-speed railways based on ISO 2631-1

The operational speeds of passenger trains have been increasing and now often exceed 300 km/h. Higher speeds can lead to increased vibration and reduced ride comfort for railway passengers. This study investigates the combined effect of speed and track geometry on vibration discomfort in high-speed trains. Railway vehicle dynamic models with various levels of complexity are used, with the measured geometry of a section of a high-speed track as an input. The models have been calibrated with vibration measurements carried out in a train running over this section of the track and then applied to predict the vibration discomfort at increased speeds. To evaluate the vibration discomfort at speeds up to 400 km/h, information on track geometry should include wavelengths up to at least 150 m. Vertical irregularities have the greatest effect at all speeds but lateral irregularities are also important. Both the vertical and lateral irregularities of a high-speed track should be controlled at wavelengths of 50–100 m that excite rigid modes of the car body, corresponding to frequencies of typically 1–2 Hz. Additionally, vertical irregularities with wavelengths of 5–12 m that excite the fundamental flexible mode of the car body, typically around 10–15 Hz, should also be controlled. The effects of cant, the rates of change of cant, and the radius of vertical curves are also evaluated although they only have a small effect on vibration discomfort.

IMPROVEMENT OF ALGORITHMS OF ADAPTIVE EDUCATIONAL TESTS FOR HIGHER AND APPLIED MATHEMATICS

The paper presents an adaptive test algorithm that has a sequential or parallel structure for selecting tasks depending on the educational content. Such adaptive tests are proposed to be used in independent work of students as a continuation of classroom studies. The structure of test assignments offers a combination of standard test questions of a closed type, step-by-step tests, and also «integrated testlets». In the training mode, the test algorithm uses the answer-until-correct responce format, thus providing immediate feedback. At the choice of the student, the testing algorithm provides for passing the test in a more rigid mode, when only one attempt is given for each answer. In strict mode with interrelated questions in the case of a single error, all the answers to the end of the current logical chain are counted as incorrect. The complexity of the tasks changes as the student passes the adaptive test, and each thematic block of tasks has its own parameters for changing the complexity of testing. If necessary, these parameters can be changed by the teacher. In work the algorithm of change of complexity of tasks depending on the test settings set by the teacher is described.To reduce the likelihood of single-type questions, it is proposed to create clusters of homogeneous tasks. As an additional function of the test algorithm, we propose selective chronometric and distractor analysis. The adaptive test algorithm provides for stopping work at the request of the student, with the possible continuation of testing in the future. Returning to the beginning of the test is not required. After passing the test, depending on the errors, the student automatically receives the recommended methodological materials for studying. In addition, when the test is interrupted, the student may also request individually selected training content.The testing algorithm provides for the possibility of jointly passing retesting by groups of students. With a sufficient number of tasks developed, it is possible to reserve some questions for group work or rigid mode testing. This reduces the likelihood of mechanical recognition of questions and increases the learning value of the adaptive test.

First-order phase transition and unexpected rigid rotation mode in hybrid improper ferroelectric (La, Al) co-substituted Ca3Ti2O7 ceramics

Ca3Ti2O7 with Ruddlesden-Popper structure exhibits the largest polarization among the known hybrid improper ferroelectrics. However, the high Curie temperature impedes the thorough study of phase transition through dielectric characterization. According to the previous theoretical design rule, the Curie temperature can be suppressed by increasing the tolerance factor. So, in the present work, high-quality Ca3-xLaxTi2-xAlxO7 (x = 0.0, 0.1, 0.2, 0.3) ceramics with increased tolerance factors were successfully prepared. The amplitude of oxygen octahedral tilt mode indeed decreases with increasing tolerance factors, leading to a degeneration of ferroelectric polarization. However, the unexpected rigid rotation mode causes the composition-invariable coercive fields. The Curie temperatures decrease linearly with increasing x and tolerance factors. The variable-temperature dielectric constant confirms first-order improper ferroelectric transitions in Ca3Ti2O7-based ceramics. The results of variable temperature X-ray diffraction reveal the coexistence of two-phases below Curie temperature. The present work confidently confirms the first-order improper ferroelectric transition in Ca3Ti2O7-based ceramics by combining results of variable-temperature dielectric response and in-situ X-ray powder diffraction.

Numerical Analysis of Robotic Manipulator Subject to Mechanical Flexibility by Lagrangian Method

In this work, a systematic approach is presented for the development of dynamic equations of motion of a robot manipulator with mechanical flexibility. A simple structural lightweight rotating manipulator with joint elastic flexibility is considered for the mechanical flexibility study. The complexity of mathematical equations involved in mechanical flexibility is analyzed. The analytical approach helps the design for controls of flexible manipulator. A set of decoupled dynamic equations are derived incorporating both the structural and joint flexibility. The dynamic equations are compared with a detailed model, and the results are showing that equations are accurate for small joints. Also the results from the simulation show that in a flexible joint system, there is no rigid mode.

A Nonheroic Cancer Narrative: Body Deterioration, Grief, Disenfranchised Grief, and Growth.

This longitudinal nonheroic narrative study allows familiarity with personal and societal transitions in the self-identity of individuals with life-threatening cancer. The theoretical anchor is Bion's container-contained theory. Five interviews with a terminally ill hospitalized male in his 30s were conducted along intervals of between 6 and 8 weeks, up to 2 months before his death. Data were analyzed using the selection mechanisms method. Findings provide insights about the hospitalization experience, his grief, and disenfranchised grief. A rigid mode of container-contained relationships with clinicians created disenfranchised grief. Reflection and coherence among self-identities lead to inner strength and emotional growth despite the body's deterioration. Clinicians have a role in holistic identity transitions of individuals with cancer. Findings illuminate practical recommendations that clinicians may adopt to improve the experience of individuals suffering from cancer at the chronic and terminal phase of illness.

Dynamic modeling and experimental validation of skid-steered wheeled vehicles with low-pressure pneumatic tires on soft terrain

Wheeled skid-steered technology has an increasing interest in its use for off-road unmanned ground vehicles, because of its great mobility and compact mechanical structure. By integrating multibody dynamics model and semi-empirical tire-terrain model, this paper presents a dynamic modeling approach for skid-steered wheeled vehicles with low-pressure pneumatic tires on soft terrain to predict and investigate its steering performance. The forward dynamics equations are built by spatial vector algebra. The tire–terrain model estimates flexible deformation and sinkage of the tire, and calculates forces and torques exerted on the tire according to relative motions of tire–terrain contact. The combined longitudinal slip and lateral skid of tires, and the vertical coupled deformations of tires and terrain are also considered in tire-terrain model. This approach optimizes the solution procedure and improves the computing efficiency. The simulation results show that the proposed tire–terrain model can predict the effects of rigid and flexible operation modes of tires on mechanical properties of tires and steering performances of the vehicle. The proposed dynamic model is validated on a six-wheeled skid-steered vehicle. The comparisons between experimental results and simulations show that the proposed dynamic model provides a better accuracy of steering performance simulation for skid-steered vehicles.