Link Dimensions Research Articles

ГЕОМЕТРИЧЕСКИЙ АНАЛИЗ ШАРНИРНОГО МЕХАНИЗМА ЦЕНТРОБЕЖНОГО ОГРАНИЧИТЕЛЯ СКОРОСТИ ЛИФТА С ДВУМЯ ВЫХОДНЫМИ ЗВЕНЬЯМИ

The article draws attention to the emergence of new promising designs of double-acting centrifugal speed limiters with a horizontal position of the axes of their devices controlling the excess speed, for example, the design of the speed limiter Vega, manufactured by Dynatech, with a horizontal position of the axis of its centrifugal device controlling the overspeed and the counter arrangement of its working bodies. The structural scheme of a similar speed limiter developed at JSC “Mogilevliftmash” is presented, which differs by collinear arrangement of the pulley and its centrifugal mechanism. The attention is paid to the absence in the free press of the design and calculation methodology of the above-mentioned speed limiters with the counter arrangement of the working bodies. The structural scheme is analyzed and attention is drawn to its asymmetry. The geometrical analysis of the articulated crank-and-rocker mechanism of the speed limiter with two output links (rocker arms) connected by connecting rods with a common input link (crank) is carried out. The dependences of the displacement of the output links on the angle of rotation of the input link are established for both parts of the mechanism, and their difference is confirmed. For the investigated speed limiter with specific dimensions of the mechanism links, the actual asynchrony of the displacement of the output links is determined. Attention is drawn to the necessity to ensure invariance of operation of the double-acting speed limiter regardless of the direction of rotation of its pulley. It is shown that non-synchronous movement of working bodies can lead to partial loss of functionality of the speed limiter and, accordingly, transformation of the double-sided limiter into a single-acting one. The problem of expediency of selection of possible variants of optimum combination of sizes of links of the mechanism is formulated for reduction of movement asynchrony of its output links and possibility of using the investigated structural scheme in precision mechanisms, in particular, in the double-acting centrifugal lift speed limiter.

Deep Learning-Driven Analysis of a Six-Bar Mechanism for Personalized Gait Rehabilitation

Abstract Recent advances in robotics and artificial intelligence have highlighted the potential for the integration of computational intelligence in enhancing the functionality and adaptability of robotic systems, particularly in rehabilitation. Designing robotic exoskeletons for the lower limb rehabilitation of post-stroke patients requires frequent adjustments to accommodate individual differences in leg anatomy. This complex engineering challenge necessitates a deep understanding of human physiology, robotics, and optimization to develop adaptive robotic systems and also to swiftly quantify the required adjustments and implement them for each patient. The conventional approaches, which mostly rely on heuristics and manual tuning, often struggle to achieve optimal results. This paper presents a novel method that integrates a genetic algorithm with a deep learning approach to generate a gait trajectory of the ankle joint from a six-bar linkage mechanism of fixed dimensions. Later, using the same approach, the inverse kinematics solution for this mechanism is also devised whereby, the set of the link dimensions of the six-bar linkage mechanism is obtained for the given gait trajectory of an individual to achieve customization. We simulated the kinematic behavior of the six-bar linkage mechanism within defined mechanical constraints and utilized the generated data for training a feedforward neural network and long short-term memory models. The proposed model, when trained, can produce accurate lengths for the desired gait trajectories in the sagittal plane and vice versa, which further validates our proposed approach for inverse kinematics solution. Moreover, to evaluate the efficiency of deep learning models, we have conducted an extensive error-based, comparative, and sensitivity analysis using different performance indices. The results highlight the potential of the proposed deep-learning-driven approach in the design analysis of gait rehabilitation robots.

ОБОСНОВАНИЕ РАЦИОНАЛЬНОЙ КОНСТРУКЦИИ КРИВОШИПНОГО МЕХАНИЗМА КОЛЕСНО-ШАГАЮЩЕГО ДВИЖИТЕЛЯ

The article substantiates the rational design of the crank mechanism of a wheel-step mover. Kinematics analysis of a prototype of the wheel-step mover revealed the presence of oscillations in the vertical coordinate of the central axis during movement. To eliminate this drawback, differential geometry methods were used, thanks to which a method for calculating the non-circular profile of support shoes was created. Studies of the dynamics of the crank mechanism of the wheel-step mover showed that even in a steady state of motion, periodically acting inertial forces arise. To reduce their effect, non-circular gears should be used in the mover power drive. The dimensions of the crank mechanism links have been calculated, at which the cross-country ability of the running system, its kinematics and dynamics characteristics are improved, energy costs when laying a track are reduced, as well as the negative impact of the machine on the fertile soil layer. The polar coordinates of the involute points have been calculated. They are needed to construct the tooth profiles of non-circular gears. As the power drive of the crank mechanism, non-circular gears have symmetrical geometric parameters along two axes and provide a constant movement speed. Thus, the wheel-step running system can be used in agriculture, the timber industry, mining, and when working in emergency situations. The mover design being developed is intended for unmanned ground vehicles. This type of unmanned vehicles is at the initial stage of its development, inferior in frequency to air and marine unmanned vehicles. A targeted concentration of production and financial resources is necessary to ensure that domestic industry has a leading position in the production and sale of unmanned ground vehicles.

Optimizing Energy Consumption of Industrial Robots with Model-Based Layout Design

The paper describes the development of an optimization model for the layout of an industrial robot relative to known locations of served machines and operations to be performed. Robotized material handling applications, defined by trajectories (paths, speed profiles) and final points, are considered in this research. An energy-monitoring framework set up by joint velocities provides input data that are fed to the optimization model. The physical placement of the robot base stands for the decisional variables, while the objective function is represented by the total distance covered by individual joints along established task routes transposed into energy consumption. The values of the decisional variables are restricted by trajectory constraints (waypoints on paths), joint operating values and link dimensions. Modelling technique and practical results using the Microsoft Solver optimization tool from Excel for Microsoft 365, Version 2312 are reported for SCARA-type robots. The performance of the optimization model is compared with actual measurements of consumed energy on an Adept Cobra S600 SCARA robot.

Coordinated monitoring and mergers and acquisitions

AbstractThis paper shows that coordinated monitoring by institutional investors affects how firms behave in the M&A market. We employ the spatial dimension of geographic links between major institutions as a proxy for interaction and information exchange—a process that determines the effectiveness of investor monitoring over firm management. Using data over the last 30 years, we show that the returns to acquiring shareholders are significantly higher, and M&A activity is significantly more intense when institutions coordinate better their monitoring efforts. Our results are robust to series of tests to gauge their sensitivity to different model specifications and estimation procedures.

Study on transmission angle and singularity in 5R planar mechanism

Transmission angle is one of the important design criteria to be considered for the effective force and motion transmission of a mechanism. Poor transmission angles are detrimental to the performance of a mechanism as they exaggerate the effect of friction and clearances. In addition, the torque required to overcome external load tends to increase and the required torque capacity of the drive increases unnecessarily. The singularity positions in a workspace are closely related to the transmission angle of the manipulator configuration. For achieving a large singularity-free area, the configuration dimension needs to be increased. Even though the objective is to design a compact five-bar planar mechanism, the link dimensions are likely to increase to some extent while achieving the desired transmission angles. This paper deals with estimating the singularity-free area of a five-bar mechanism by considering variations in transmission angles for different link lengths. The generalized methodology presented in this work demonstrates the estimation of singularity-free largest reachable area and link proportions at which intra-link transmission angles are confined. A dimensionless singularity-free workspace index is proposed to quantify performance at various transmission angles.

دور البراعة التنظيمية في تعزيز الانغراز الوظيفي (دراسة تحليلية في دائرة صحّة واسط)

The subject of organizational dexterity is one of the important vital issues through which organizations seek to provide renewable mindsets and maintain their survival and continuity according to different organizational methods and reach the Job Embeddedness of employees. The main objective of this research is to identify the impact of organizational dexterity with its dimensions of (exploration and exploitation) in promoting Job Embeddedness with its dimensions of (links, convenience, sacrifice) in the Wasit Health Department, as the research problem lies in the extent of the interest of the researched organization in organizational dexterity and functional attachment By distancing them as well as the relationship between them, and the importance of the research is in diagnosing the impact of organizational dexterity in its dimensions in enhancing functional involvement in its dimensions. In order to achieve the goal of the research, a sample of employees in the Wasit Health Department was selected, and the researcher relied on the questionnaire as a tool for collecting the necessary data. In order to complete the research and achieve the goals it seeks, (75) questionnaires were distributed. , The statistical program (v.16 SPSS) was used, and the research reached a set of conclusions, the most important of which is that there is a significant correlation and influence between organizational dexterity in its dimensions and job Embeddedness. The research presented a set of recommendations, the most important of which is that the management of the researched organization should strengthen organizational relations within the organization and remove obstacles between employees and management, which reflects positively on enhancing job Embeddedness

ANALYTICAL SOLUTION OF THE DYNAMIC SYNTHESIS PROBLEM OF THE VIBRATION EXCITATION MECHANISM

In this article, an optimal dynamic synthesis of lever mechanisms was created and, on its basis, a dynamic synthesis of the mechanism of vibrational excitation of pulsed impact on the foundation was developed. An analytical-optimization method has been developed that allows, by introducing a modified objective function, to also determine the optimal dimensions of the mechanism links. Since the geometrical dimensions of the mechanism enter the objective function non-linearly (implicitly through the angles of rotation of the links, analogs of velocities and analogs of accelerations), numerical optimization methods are used to find them. In this case, at each step of the descent to the minimum, the mass-inertial parameters of the mechanism are determined analytically.

Dynamic tasks in models of product operability

When developing models of critical mechanical engineering products, it is necessary to solve dynamic problems, taking into account changes in the dimension chains of links in the process of functioning of mechanisms. A method of calculating dynamic dimension chains as applied to solving direct and inverse problems is proposed. The solution of a direct problem is given under the condition that the stray field of the master link includes the errors of production and those related to the changes in the dimensions of the initial links under the action of operational loads. To obtain the value of the product part wear rate we propose using empirical dependences of the relation between the wear rate and formation of hydrogen in the process of interaction of materials.

Vital triangle: A new concept to evaluate urban vitality

Urban vitality is a driving force of urban sustainable development and influences the well-being of its residents. To better understand and evaluate it, we defined urban vitality from the perspective of the urban organism and proposed the “vital triangle” conceptual framework linked to the three aspects of growth, diversity, and mobility. We designed an evaluation index system that includes the six dimensions of population, economy, society, government, environment, and external links by integrating multiple sets of heterogeneous data, and applied it to cities in the Yangtze River Delta. The results show that Shanghai, Nanjing, Suzhou, and Hangzhou have the highest vitality levels but are weak regarding their eco-environments. Cities with high vitality are distributed on the Z-shaped key development belt of the Yangtze River Delta urban agglomeration planning. Regional differences in external links and population vitality are significant, and these two dimensions pose weaknesses to many cities. The interregional differences linked to social vitality are the smallest. Vitality not only comes from within the urban system, but also greatly depends on the external environment. The concept “vital triangle” and relevant evaluation framework are intended to serve as a basis for future research, and the case study could provide some key decision-making support for urban planning and management.

The development and pilot of the university student embeddedness (USE) scale for student retention within universities: validation with an Australian student sample

A significant number of university students are leaving their institutions before completing their degrees. The present research project applied embeddedness theory, from organizational research, to understand student retention in a tertiary student population, and develop a quantitative instrument that measured university student embeddedness. In Study One, a mixed-methods approach was employed to determine whether the Fit (similarity between the student and the university), Links (count of relationships at university), and Sacrifice (losses upon leaving university) dimensions of embeddedness related to students’ self-reported reasons for remaining enrolled at their university. Qualitative results from 15 undergraduate students indicated that intent to remain could be understood within the embeddedness dimensions of Fit, Links, and Sacrifice. These themes were employed to build the University Student Embeddedness (USE) scale. The measure was examined against Rasch measurement model assumptions for each of its subscales using data collected from 299 Australian tertiary students. Study Two sought to examine exploratory evidence of the concurrent validity of the scores from this developed measure. Responses from a separate sample of 196 Australian tertiary students showed only the Fit scale significantly related to student intentions to stay at university. All USE scales correlated with academic-related skills and motivations. These results suggest that the Fit scale may be valuable in identifying students at risk of dropout. Early identification of “at risk” students may lead to the development of targeted retention interventions. However, the USE’s role in detection requires further validation and the development of consistent findings within other student cohorts.

Hybrid Regression Model for Link Dimensioning in Spectrally-Spatially Flexible Optical Networks

The latest trends in computer networks bring new challenges and complex optimization problems, one of which is link dimensioning in Spectrally-Spatially Flexible Optical Networks. The time-consuming calculations related to determining the objective function representing the amount of accepted traffic require heuristics to search for good quality solutions. In this work, we address this problem by proposing a hybrid regression model capable of the objective function estimation. The presented algorithm uses a machine learning model built on already evaluated solutions for choosing new promising ones, providing a fast and effective method for solving the considered problem. The experimental evaluation conducted on two representative network topologies demonstrates that the proposed approach can significantly outperform other methods in the case of the EURO28 topology, while for the US26 topology, it provides results comparable to the solutions obtained so far.

Mathematical represantation of the branch kinematics of a transmission with descreteflexible connection

The paper deals with the mathematical model development of the kinematical behavior of the flexible transmission branch exemplified. A typical example of transmission with discrete-flexible connection can be considered as the movement of the drive elements of the chain. The use of chain gears as a drive for a wide range of technological machines with high requirements in order to ensure a certain law of motion of the executive bodies is the task of studying changes in its kinetic characteristics during operation. It is established that random deviations of the chain step from the nominal are the result of manufacturing inaccuracy elements of transmission and wear during operation. The mathematical model of motion gives an idea of the real interpretation of the kinematics of the chain transmission taking into account the uneven dimensions of individual links. The model makes it possible to present the components of deviations of the transmission movement from the given in two groups: deviations created by the accumulated error of the chain section, and movement. Calculations based on the developed mathematical model show that when the hinges of the sleeve-roller chain are worn by 2.5%, the value of the coefficient of non-uniformity of the transmission increases threefold.

Kinematic reliability evaluation of high-precision planar mechanisms experiencing non-uniform wear in revolute joints

Joint clearance significantly influences the motion accuracy of a mechanism. Most of the existing studies assumed that the clearance is regular with constant size. The effect of irregular joint clearance due to wear on the kinematic accuracy is ignored. Hence, this study conducts kinematic reliability analysis of high-precision planar mechanisms experiencing non-uniform wear. Firstly, under the framework of multi-body dynamics, an efficient wear prediction method based on Archard’s wear model is presented for parameterized description of the clearance boundary. Secondly, fractional moments of the motion output considering the uncertainties of driving actuators, link dimensions and non-uniform joint clearance are derived with the dimension reduction method. On this basis, the maximum entropy model constrained by fractional moments is employed to approximate the distribution of the motion output. Then the kinematic reliability is accordingly calculated using the numerical integral. Meanwhile, a Monte Carlo simulation (MCS) based method is developed for kinematic reliability analysis by virtue of slicing sampling technique to provide a reference solution. Finally, experimental testing of a slider-crank mechanism is presented to verify the wear prediction method. The slider-crank mechanism is also used to demonstrate the effectiveness of the proposed kinematic reliability evaluation method.

Using digital humanity approaches to visualize and evaluate the cultural heritage ontology

PurposeThis study applies digital humanity tools (Gephi and Protégé) for establishing and visualizing ontologies in the cultural heritage domain. According to that, this study aims to develop a novel evaluation approach using five ontology indicators (data overview, visual presentation, highlight links, scalability and querying) to evaluate the knowledge structure presentation of cultural heritage ontology.Design/methodology/approachThe researchers collected and organized 824 pieces of government’s open data (GOD), converted GOD into the resource description framework format, applied Protégé and Gephi to establish and visualize cultural heritage ontology. After ontology is built, this study recruited 60 ontology participants (30 from information and communications technology background; 30 from cultural heritage background) to operate this ontology and gather their different perspectives of visual ontology.FindingsBased on the ontology participant’s feedback, this study discovered that Gephi is more supporting than Protégé when visualizing ontology. Especially in data overview, visual presentation and highlight links dimensions, which is supported visualization and demonstrated ontology class hierarchy and property relation, facilitated the wider application of ontology.Originality/valueThis study offers two contributions. First, the researchers analyzed data on East Asian architecture with novel digital humanities tools to visualize ontology for cultural heritage. Second, the study collected participant’s feedback regarding the visualized ontology to enhance its design, which can serve as a reference for future ontological development.

Reliability-Based Analysis and Optimization of the Gravity Balancing Performance of Spring-Articulated Serial Robots With Uncertainties

Abstract This article proposes a method for analyzing the gravity balancing reliability of spring-articulated serial robots with uncertainties. Gravity balancing reliability is defined as the probability that the torque reduction ratio (the ratio of the balanced torque to the unbalanced torque) is less than a specified threshold. In this paper, the reliability analysis is performed by exploiting a Monte Carlo simulation (MCS) with consideration of the uncertainties in the link dimensions, masses, and compliance parameters. A reliability-based design optimization (RBDO) method is also developed to seek reliable spring setting parameters for maximized balancing performance under a prescribed uncertainty level. The RBDO is formulated with consideration of a probabilistic reliability constraint and solved by using a particle swarm optimization (PSO) algorithm. A numerical example is provided to illustrate the gravity balancing performance and reliability of a robot with uncertainties. A sensitivity analysis of the balancing design is also performed. Lastly, the effectiveness of the RBDO method is demonstrated through a case study in which the balancing performance and reliability of a robot with uncertainties are improved with the proposed method.

Link dimension and exact construction of graphs from distance vectors

Minimum resolution set and associated metric dimension provide the basis for unique and systematic labeling of nodes of a graph (G) using distances to a set of landmarks. Such a distance vector set, however, may not uniquely identify the graph or allow for its exact construction. The concept of construction set is presented, which overcomes these limitations. Link dimension (ξ(G)) is the minimum cardinality of a construction set. We study ambiguity in the given distance vector set and conditions for resolving them. Bounds over link dimension, proofs for link dimension for various graph families and relationship between graph dimensions and graph spectra are presented. The inverse problem of identifying whether a given set of non-negative distance vectors can be associated with a graph is also addressed, introducing the concept of graphability of distance vectors. A graph of N nodes can now be compressed to a representation with an N×ξ(G) matrix which allows for its exact reconstruction.

Linking undergraduate professional identity development in engineering to major embeddedness and persistence

Although the development of professional identity is thought to play a central role in the career development process, little empirical research has examined change in professional identity over time and its connection to adjustment and persistence in a professional field of study. In this research, latent growth modeling was used to examine the effects of pre-college professional identity and change in professional identity through the first year of college in a sample of engineering students (N = 295). Results indicated that professional identity prior to entering college and rate of change in professional identity over the first year of study were related to major embeddedness dimensions of fit (i.e., match between oneself and the major), links (i.e., professional connections), and sacrifice (i.e., costs and benefits associated with leaving the major). Rate of change in professional identity was also positively related to persistence in the engineering major the following year. Despite the general utility of professional identity in predicting embeddedness, men and women differed in several important parameter estimates. This research suggests professional identity development is best conceptualized and empirically examined as a dynamic process that occurs over time, contributes to understanding of the factors underlying adjustment and persistence of women and men in STEM career pathways, and emphasizes the importance of fostering pre-college professional identity and professional identity development early in professional programs of study.

Toward A Framework for Assessing the Fair Distribution of Space in Urban Streets

The increasing popularity of street redesigns highlights the intense competition for street space between their different users. More and more cities around the world mention in their planning documents their intention to rebalance streets in favor of active transportation, transit, and green infrastructure. However, few efforts have managed to formalize quantifiable measurements of the balance between the different users and usages of the street. This paper proposes a method to assess the balance between the three fundamental dimensions of the street—the link, the place, and the environment—as well as a method to assess the adequation between supply and demand for the link dimension at the corridor level. A series of open and government georeferenced datasets were integrated to determine the detailed allocation of street space for 11 boroughs of the city of Montréal, Canada. Travel survey data from the 2013 Origine-Destination survey was used to model different demand profiles on these streets. The three dimensions of the street were found to be most unbalanced in the central boroughs of the city, which are also the most dense and touristic neighborhoods. A discrepancy between supply and demand for transit users and cyclists was also observed across the study area. This highlights the potential of using a distributive justice framework to approach the question of the fair distribution of street space in an urban context.

Influence of dynamic loads in joints on dimensional stability

In small arms manufacturing the lock dimensional chain final link precision is secured with manual file fitting and removing the tolerance intentionally left on the recoil lugs. The manual process reduces the contact stiffness of the lock components, and the final link dimension (between the cylindrical gauge end that simulates a cartridge, and the breeching lock face) set during the assembly is distorted when the breech lock components are exposed to shot impact loads. For this reason, the cylindrical cartridge dummy used for the initial assembly is sized to allow for subsequent plastic deformation at the breech lock component interfaces. The deformation value is determined experimentally on an ad hoc basis. Polynomial expressions have been obtained experimentally for the interface plastic deformation vs. relative positioning errors and surface finish relation for parts made of typical military steel grades. To study the relation between the interface surface machining methods and contact stiffness flat specimens, 50RA steel quenched to HRC 40…45 (the roughness Rz is 10…15 μm) were machined as follows: peripheral pregrinding; flank milling; file crosswise (at 45°) movements. The results generated after processing the measurements made with a HOMMEL TESTER W55 instrument show that finish flank milling yields the best results.