Torsional Phenomena Research Articles

Shape Reconstruction of Extensible Continuum Manipulator Based on Soft Sensors.

Continuum manipulators can improve spatial adaptability and operational flexibility in constrained environments by endowing them with contraction and extension capabilities. There are currently desired requirements to quantify the shape of an extensible continuum manipulator for strengthening its obstacle avoidance capability and end-effector position accuracy. To address these issues, this study proposes a methodology of using silicone rubber strain sensors (SRSS) to estimate the shape of an extensible continuum manipulator. The way is to measure the strain at specific locations on the deformable body of the manipulator, and then reconstruct the shape by integrating the information from all sensors. The slender sensors are fabricated by a rolling process that transforms planar silicone rubber sensors into cylindrical structures. The proprioceptive model relationship between the strain of the sensor and the deformation of the manipulator is established with considering the phenomenon of torsion of the manipulator caused by compression. The physically extensible continuum manipulator equipped with three driving tendons and nine SRSS was designed. Comprehensive evaluations of various motion trajectories indicate that this method can accurately reconstruct the shape of the manipulator, especially under end-effector loads. The experimental results demonstrate that the mean (maximum) absolute position error of the endpoint is 1.61% (3.45%) of the manipulator length.

Torsion phenomena for zero-cycles on a product of curves over a number field

For a smooth projective variety X over an algebraic number field k a conjecture of Bloch and Beilinson predicts that the kernel of the Albanese map of X is a torsion group. In this article we consider a product X=C1×⋯×Cd\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X=C_1\ imes \\cdots \ imes C_d$$\\end{document} of smooth projective curves and show that if the conjecture is true for any subproduct of two curves, then it is true for X. For a product X=C1×C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X=C_1\ imes C_2$$\\end{document} of two curves over Q\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathbb {Q} $$\\end{document} with positive genus we construct many nontrivial examples that satisfy the weaker property that the image of the natural map J1(Q)⊗J2(Q)→εCH0(C1×C2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$J_1(\\mathbb {Q})\\otimes J_2(\\mathbb {Q})\\xrightarrow {\\varepsilon }{{\\,\ extrm{CH}\\,}}_0(C_1\ imes C_2)$$\\end{document} is finite, where Ji\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$J_i$$\\end{document} is the Jacobian variety of Ci\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C_i$$\\end{document}. Our constructions include many new examples of non-isogenous pairs of elliptic curves E1,E2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_1, E_2$$\\end{document} with positive rank, including the first known examples of rank greater than 1. Combining these constructions with our previous result, we obtain infinitely many nontrivial products X=C1×⋯×Cd\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X=C_1\ imes \\cdots \ imes C_d$$\\end{document} for which the analogous map ε\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varepsilon $$\\end{document} has finite image.

Shaking table test on irregular and complex connected structure

Affected by the external environment, it is easy to cause complex and irregular problems in the building structure, bringing new safety hazards to the seismic resistance of the structure. Based on the background of the east building of the railway station with cross ground crack, the seismic performance of irregular and complex connected structures under different seismic intensities was analysed.The research results indicate that under the action of a 7-degree seismic fortification, the structure is basically in an elastic state, with a stiffness degradation of 12.9%, meeting the performance requirements of being undamaged during small earthquakes; Under seismic fortification, the structure is mainly characterized by cracking at the bottom beam end, with a small crack width and a stiffness degradation of 41.7%, meeting the requirements for moderate earthquake repairability; Under the rare earthquake of 8degree , plastic hinges begin to form at the beam and column ends of the structure and gradually develop, with stiffness degradation reaching 81.9%. All seismic responses of the structure comply with the limit requirements of the code (GB 50011-2010); Under the rare earthquake of 8 degree , there is a serious torsion phenomenon in the small triangle area, which leads to the disharmony of forces on the inner and outer beams and columns. In earthquakes, it is easy to cause structural collapse due to the first failure of the outer columns. Suggesting to increasethe stiffness of the small triangular column to solve the above problem. Under extremely rare earthquakes, the plastic hinge mechanism of the structure has developed completely, with stiffness degradation approaching 90% and no collapse phenomenon, indicating that complex connected structures have excellent seismic performance.

A study on torsional behaviour of rectangular reinforced concrete beams with U-shaped encased welded wire mesh

Concrete is one type of composite material composed of fine and coarse aggregate bonded together with cementitious paste that is durable in its hardened state over time. It has now become an important and widely used building material. However, it possesses a brittleness material property in tension even though it is strong in compression. Here the study is restricted to the concrete subjected to torsion phenomena. In the past decades, various ways have been explored to improve the ductile material strength property of the concrete matrix in proposed new construction. Reinforced concrete is constructed by using conventional reinforcements; prestressed concrete is an example of that. Also, various types of fibers in the form of discrete nature are applied to improve the tensile strength capacity of concrete in proposed construction, and retrofitting techniques using various materials are exercised to strengthen the existing structures. Hence, remarkable research in the literature on fiber reinforced concrete and on FRP techniques has been carried out. However, welded wire mesh with high yield strength can be encased in concrete members to improve composite material property and avoid abrupt cracking with an increase in torque carrying capacity of plain and reinforced concrete beam specimens used for proposed construction.

Improvement and compensation of temperature drift of scale factor of a SOI-based MEMS differential capacitive accelerometer

In recent years, the analysis and improvement of temperature characteristics of Si-based capacitive accelerometers has received considerable research attention in the field of Microelectromechanical system (MEMS) sensors. Generally, the influence of temperature on the accelerometers can be mitigated by optimizing the structural design and compensating the output signal. Herein, the output characteristics of an accelerometer designed with asymmetrically arranged combs were analyzed under various temperatures. The purpose of this paper is to improve the temperature drift of scale factor (TDSF) of MEMS capacitive accelerometer, using the asymmetric layout structure to improve the TDSF fundamentally, and the least square method to achieve temperature compensation efficiently. The variations in the TDSF were compared for the symmetric and asymmetric structures. In addition, we modeled the accelerometer with an asymmetric structure for simulations to analyze the errors resulting from the electrostatic torsion phenomenon induced by the asymmetric structure. Moreover, a temperature compensation model was developed for the scale factor of the accelerometer, which was validated and verified with the data obtained from simulations and experiment. Furthermore, an accelerometer based on silicon on insulator was fabricated and tested to verify the simulation results and the compensation effects. According to the results, the scale factor of the studied accelerometer was 171.83 mV g−1 and the average value of the TDSF was 83.56 ppm °C−1 Overall, the experimental results were almost consistent with the simulation results. Under the asymmetric layout, the scale-factor stability improvement of the accelerometer could reach up to 86.96%, and the error caused by electrostatic torsion was ∼2.93%, which is relatively negligible. After compensation, the range and standard deviation of the scale factor of the accelerometer with respect to temperature were reduced by 94.46% and 95.69%, respectively, and the average value of TDSF was reduced by 95.90%, which verified the effectiveness of the compensation model.

An experimental behaviour of RCC rectangular beams with U-shaped encased welded wire mesh under torsion phenomena

Concrete is one form of composite material composed of fine and coarse aggregate bonded together with cementitious paste that is durable in its hardened state over time. Although it is robust in compression, it has a brittle material property in tension. Axial and shear forces, bending moments, and torsion moments may arise in the concrete body in a reinforced concrete design depending on the loading conditions. In this sequel, the encased welded wire mesh with high yield strength is used in order to improve composite material characteristics and reduce abrupt cracking with an increase in torque carrying capacity of concrete specimens. A total of 18 beam specimens were casted and tested under pure torsion, in that six numbers were control specimens and the remaining twelve numbers were specimens with encased welded wire mesh. U-shaped wrapped WWM, both in the form of transverse strips and continuous U-shaped sheets are used to observe enhancement in the cracking and ultimate torsional strength of plain and RCC rectangular beams respectively. The curves of tested specimens containing WWM wrapping patterns showed the specimens containing WWM resist more torsional loads as compared to control specimens. The ultimate torque get increased effectively due to the introduction of U-shaped WWM wrap in fully reinforcement type means longitudinal reinforcement with closed stirrups beam specimens.

A New Insight into the Stability of Precariously Balanced Rocks

Large granitic boulders resting on steep slopes represent considerable safety hazards that largely depend on the location of the contact surface characterized by the impression d, denoting the parallel distance between the contact surface and the original rock surface. On the other hand, this impression reflecting the often convex nature of the contact between boulders and resting platforms, cannot be measured precisely, so Factors of Safety (FoS) computed with this input may have significant uncertainties. Using geometric 3D analysis, here, we present the concept of computing FoS as a function of the impression d, admitting a much more reliable estimate of the actual hazards. Beyond introducing the FoS functions, we also identify all failure modes, some of which have not yet been investigated. We compute the FoS functions for the boulder Pena do Equilibrio, located in Spain. Our computations for FoS against sliding match all earlier results. However, we also compute FoS against toppling and against torsion and show that the latter may be critical. Since our methods are general, this suggests that torsion phenomena, which have been scarcely studied so far, may be relevant to analyze the stability of other natural rock boulders.

Quantum tilting modules over local rings

AbstractWe show that tilting modules for quantum groups over local Noetherian domains of quantum characteristic 0 exist and the indecomposable tilting modules are parametrized by their highest weight. For this, we introduce a model category associated with a Noetherian ‐domain and a root system . We show that if is of quantum characteristic , the model category contains all ‐modules that admit a Weyl filtration. If is in addition local, we study torsion phenomena in the model category. This leads to a construction of torsion free, or “maximal” objects in . We show that these correspond to tilting modules for the quantum group associated with and .

Large deflection of composite beams by finite elements with node-dependent kinematics

In this paper, the use of the node-dependent kinematics concept for the geometrical nonlinear analysis of composite one-dimensional structures is proposed With the present approach, the kinematics can be independent in each element node. Therefore the theory of structures changes continuously over the structural domain, describing remarkable cross-section deformation with higher-order kinematics and giving a lower-order kinematic to those portion of the structure which does not require a refinement. In this way, the reliability of the simulation is ensured, keeping a reasonable computational cost. This is possible by Carrera unified formulation, which allows writing finite element nonlinear equilibrium and incremental equations in compact and recursive form. Compact and thin-walled composite structures are analyzed, with symmetric and unsymmetric loading conditions, to test the present approach when dealing with warping and torsion phenomena. Results show how finite element models with node-dependent behave as well as ones with uniform highly refined kinematic. In particular, zones which undergo remarkable deformations demand high-order theories of structures, whereas a lower-order theory can be employed if no local phenomena occur: this is easily accomplished by node-dependent kinematics analysis.

High performance Mg-8Gd-4Y-1Zn-0.5Al alloy with long-period stacking ordered structure by hot rolling

The Mg-8Gd-4Y-1Zn-0.5Al (wt%) alloy prepared by metal type casting were homogenized, rolled or extruded-rolled to obtain sheets, and followed by aging treatment. The microstructures were analyzed by OM, SEM, TEM, EBSD and XRD, the hardness and tensile mechanical properties were tested. The results show that the optimal process is rolling at 793 K with the deformation of 70% for the homogenized sheet. The microstructure of the sheet is composed of fully dynamic recrystallized grains with a strong basal texture, and the aggregated 18R-LPSO structures randomly distribute in the matrix. After peak aging treatment, the yield strength (YS), ultimate tensile strength (UTS) and elongation to failure (EL) of the sheet are 343 MPa, 380 MPa and 7.5%, respectively. After the extruded sheets were rolled at 793 K with 50% deformation, the grains grew up. The texture changes from a silk type to the strong basal type. The 18R-LPSO structures reduce the torsion phenomena, but get together. After peak aging treatment, the YS, UTS and EL reach 391 MPa, 462 MPa and 5.5%, respectively. The 18R-LPSO structures with streamlined distribution along rolling direction increase the anisotropy of mechanical properties of the extruded-rolled sheet.

Connective $K$-theory and Adams operations

We investigate the relations between the Grothendieck group of coherent modules of an algebraic variety and its Chow group of algebraic cycles modulo rational equivalence. Those are in essence torsion phenomena, which we attempt to control by considering the action of the Adams operations on the Brown–Gersten–Quillen spectral sequence and related objects, such as connective K_0 -theory. We provide elementary arguments whenever possible. As applications, we compute the connective K_0 -theory of the following objects: (1) the variety of reduced norm one elements in a central division algebra of prime degree; (2) the classifying space of the split special orthogonal group of odd degree.

Design study of electric vehicle roll-cage obtained using modal analysis

Understanding the dynamic behaviour of structures has become increasingly essential in the design process of any mechanical system. Modal factors like natural frequencies and mode shapes characterize the dynamic response of the structure and can be used for determination of the possible bending and torsion phenomenon. The Computer-Aided Drafting (CAD) model plays an important role in the design and development phases of an electric vehicle. For doing Finite Element Analysis (FEA) using software CAD model has to be imported so that after conversion Finite Element (FE) model can be solved. In the present case the CAD model is imported in HyperMesh. The FE model is generated and solved by using OptiStruct. Ignoring the first six natural frequencies and mode shapes due to its association with six degrees of freedom, subsequent six natural frequencies and mode shapes are proposed for an electric vehicle roll-cage. We can learn even more from CAD geometry and mode shapes in every direction about its stiffness and weight. Once we know our design baseline, we can use a software simulation to use a design study and improve its performance. We have considered the pipe diameter, thickness, tube width and height as main design parameters which needs to be optimized. In this paper, we optimized all these design parameters to make driver comfortable during driving by increasing natural frequency of the roll-cage structure by 3.34 times the human body threshold.

Design methodology in transverse webs of the torsional box structure in an ultra large container ship

Container ships has a transverse section in the form of an open profile, making it very sensitive to torsion phenomena. To minimize this effect, a structure known as a torsion box exists, which is subject to high stresses influenced by the fatigue phenomenon and the existence of cut-outs, for the passage of the longitudinal stiffeners, acting as stress concentrators. The aim of this study is to propose a two-stage design methodology to aid designers in satisfying the structural requirements and contribute with to a better understanding of the considered structure. The transverse webs of a torsional box structure are examined by comparing different cut-out geometries from numerical models with different regular load conditions to obtain the variables of the fatigue safety factor through linear regression models. The most appropriate geometry of the torsion box is established in terms of minimum weight, from nonlinear multivariable optimization models.

Registration method for maintenance-work support based on augmented-reality-model generation from drawing data

Abstract The importance of operations and maintenance (O&M) and piping inspection in shipbuilding and offshore plant industries has significantly increased recently. Therefore, this study proposes a system that uses augmented reality (AR) to support these operations. AR in O&M and inspection systems can increase work comprehension and efficiency by utilizing 3D graphics, instead of drawings, to describe specific work functions. To realize this improvement, the augmented model should correspond to the reality; if accurate registration is not achieved, it can disrupt the work functions. Therefore, marker-based AR is used to generate specific recognition objects and correct the location of the augmented model. However, owing to certain characteristics of the shipbuilding and offshore plant industries, the markers are likely to be damaged, and thus the cameras fail to clearly detect them. In this study, a 3D camera was used to generate a point cloud based on 3D image information. Accordingly, the area around the model to be detected was designated as the region of interest (ROI). Furthermore, it is difficult to support a high-end device environment because it is tested as a portable device that can be used in a working environment; therefore, superfluous data were removed by detecting the 3D edges in the ROI, thereby minimizing data operation. The scalability of this work was enhanced using the computer-aided design (CAD) file information extracted from the CAD tool (used in the shipbuilding industry) and converting it into a point cloud. The proposed system is expected to eliminate the issues related to understanding the O&M work by addressing registration errors that might occur in constrained environments and to improve the torsional phenomenon of the augmented models.

Two applications of the integral regulator

We review Li's refinement of the KLM regulator map, and use it to detect torsion phenomena in higher Chow groups.

The Baum–Connes property for a quantum (semi-)direct product

The well known “associativity property” of the crossed product by a semi-direct product of discrete groups is generalized into the context of discrete quantum groups. This decomposition allows to define an appropriate triangulated functor relating the Baum–Connes property for the quantum semi-direct product to the Baum–Connes property for the discrete quantum groups involved in the construction. The corresponding stability result for the Baum–Connes property generalizes the result [5] of J. Chabert for a quantum semi-direct product under torsion-freeness assumption. TheK-amenability connexion between the discrete quantum groups involved in the construction is investigated as well as the torsion phenomena. The analogous strategy can be applied for the dual of a quantum direct product. In this case, we obtain, in addition, a connection with the Künneth formula , which is the quantum counterpart to the result [7] of J. Chabert, S. Echterhoff and H. Oyono-Oyono. Again the K -amenability connexion between the discrete quantum groups involved in the construction is investigated as well as the torsion phenomena.

Delayed Diagnosis and Treatment of Simultaneous Bilateral Adnexal Torsion

Adnexal torsion (AT) is a gynecologic emergency that requires prompt diagnosis and treatment to relieve patient symptoms and to achieve viable adnexa. We present a case that resulted in delayed diagnosis and treatment of simultaneous bilateral adnexal torsion most following the use of ART. Our delayed diagnosing resulted likely from the identical appearance of the ovaries on ultrasound and alternative diagnosis of ovarian hyperstimulation syndrome, an awareness to this rare phenomenon of simultaneous bilateral adnexal torsion might have helped to perform the surgery earlier.

Design Principles for Minimum Torsional Response of Wall-Frame Concrete Structures

ABSTRACTA seismic design procedure is described incorporating the well-accepted property that the stiffness of reinforced concrete elements is strength dependent and the requirement that the method of assigning strength to elements should be aiming at minimum torsional phenomena. Such a response allows a direct comparison with the findings of a static nonlinear analysis, which may provide the limits of story drifts and the induced plastic rotations in potential plastic hinges. The requirement of a practically translational response implies that the element strength assignment should be based on planar considerations and the initially elastic response should be of minimum torsion.

The experimental and analytical investigations of torsion phenomenon of thin-walled cold formed channel beams subjected to four-point bending

Thin-walled beams have many practical applications. This stimulates practical and scientific researches on them. The recent developments in metal cold forming makes it possible to produce more complicated shapes to reduce the mass of structural members. However, vast variety of cross-section of such beams make their analysis difficult. In the paper the authors have investigated thin-walled cold formed steel beams with open section loaded subjected to pure bending. Experimental results were compared with analytical ones. This gave the answer why the actual tested beams rotated around the shear centre though they were subjected to pure bending. The authors described the factors which are responsible for the torsion moment in the investigated thin-walled steel beams with open sections subjected to pure bending. Two different cross-sections of thin-walled beams were investigated and the more resistant to torsion phenomena was indicated.

Wave Response Analysis for Pontoon-type Pier: Very Large Floating Structure

In this study, we proposed a pier of pontoon-type, Very Large Floating Structure (VLFS), with the length of 500m, breadth of 200 m and height of 2 m in Yeosu domestic port. Since this structure ought to endure wave loads for long periods at sea, it is essential to analyze the wave response characteristics. Direct-method is used to analyze the fluid-structure problem and the coupled motion of equation is used to obtain response results. The structural part is calculated by using finite element method (FEM) and the fluid part is analyzed by using boundary element method (BEM). Dynamic responses caused by the elastic deformation and rigid motion of structure are analyzed by numerical calculation. To investigate response characteristics of the pier in regular waves, several factors such as the wavelength, water depth, wave direction and flexural rigidity of structure are considered. As a result, wave response of pier changed at the point of 1.5 and represented the torsional phenomenon according to the various incident waves. And the responses showed increasing tendency as the water depths increase at the incident point in case of $L/{\lambda}