String Structure Research Articles

A Smooth Model for the String Group

We construct a model for the string group as an infinite-dimensional Lie group. In a second step we extend this model by a contractible Lie group to a Lie 2-group model. To this end we need to establish some facts on the homotopy theory of Lie 2-groups. Moreover, we provide an explicit comparison of string structures for the two models and a uniqueness result for Lie 2-group models.

A form-finding method of beam string structures — Offload by steps method

The problem of form-finding of beam string structures was studied, and the method named offload by steps was put forward in accordance with the properties of the mechanical status of the structures. This method was used to find the form of the unstrained state on the basis of the pre-stressed state without the need to assume the unstrained form first. Numerical simulations and experimental research on the form-finding of beam string structures were carried out to verify the offload by steps method and, more importantly, to study the application of the method in engineering practice. The scale of the experimental model was 1/20, and the stretching pattern was the same as that in practical engineering. Comparisons of internal forces and deformations corresponding to unstrained and pre-stressed states of the model were made between experimental and calculation results. The following conclusions were drawn. First, the offload by steps method can be applied to the engineering practice without assuming the form of the unstrained state, and the form of the unstrained state corresponding to that of the pre-stressed state can be obtained directly. Second, the internal forces of the beam string structures in their pre-stressed states can be obtained easily by using the statically-determinate calculation model in the offload by steps method, which can guide design effectively. Third, the method for estimating the cable tension by balancing the deadweight of the beam string truss can be applied to engineering practice.

LATERAL BUCKLING OF THE STRUTS IN BEAM STRING STRUCTURES CONSIDERING THE LAYOUT OF STRINGS

The struts in a beam string structure (BSS) may buckle laterally under compression. The lateral buckling of the struts is determined not only by the rotational stiffness of the beam–strut joints and the length and bending stiffness of the struts, but also by the rise and lateral stiffness of the beam, the number of struts, and the layout of strings. In this paper, the multi-strut BSS with several types of layout of strings is studied. An analytical method for estimating the lateral buckling load of the struts in BSS is proposed. Parametric studies are carried out to investigate the variation of the lateral buckling of the struts in the BSS for different string layouts. In the end, the validity of the proposed method is examined by means of numerical simulations using the geometrically nonlinear finite element method.

The Response of the Bi-Directional Beam String Structure under Vertical Seismic Considering Supporting Frame

This paper using time time-procedure analysis method to analyze seismic response on a 80 m × 80 m bidirectional beam string structure model. Under vertical seismic action, we respectively compared to the seismic performance under the structure have or no supporting frame and have the same supporting frame but different support conditions. Under vertical seismic action, the axial force of brace is almost the same considering or unconsidering the supporting frame, while the upper beam vertical displacement is increased and the surrounding of the roof even increased several times considering supporting frame; the boundary conditions for the sliding hinge support bidirectional beam string structure which under vertical seismic ( middle seismic ) action the brace axial force and winding beam vertical displacement are nearly same with the fixed hinged support, while the horizontal displacement of the winding beam is larger than the fixed hinged support; the change of support conditions affect the order of the various modes of the structure but no affect the structural vibration modes.

Research of Mechanical Influence of Initial Imperfections on Beam String Structure

Initial imperfections on beam string structure (BSS) include geometric imperfections and residual stresses, which negatively influence the mechanical properties of BSS. This paper analyzed the mechanical influences of initial imperfections on BSS by FEA, pointed out that initial imperfections do not remarkably influence the properties of BSS in stage of prestressing, but geometric imperfections obviously influence the displacement out of plane in stage of use, which should be controlled to improve the safety of BSS by installing enough lateral supports at the upper chords of BSS in construction.

Vortex lines in a ferromagnetic spin-triplet superconductor

Based on Duan's topological current theory, we show that in a ferromagnetic spin-triplet superconductor there is a topological defect of string structures which can be interpreted as vortex lines. Such defects are different from the Abrikosov vortices in one-component condensate systems. We investigate the inner topological structure of the vortex lines. The topological charge density, velocity, and topological current of the vortex lines can all be expressed in terms of δ function, which indicates that the vortices can only arise from the zero points of an order parameter field. The topological charges of vortex lines are quantized in terms of the Hopf indices and Brouwer degrees of φ-mapping. The divergence of the self-induced magnetic field can be rigorously determined by the corresponding order parameter fields and its expression also takes the form of a δ-like function. Finally, based on the implicit function theorem and the Taylor expansion, we conduct detailed studies on the bifurcation of vortex topological current and find different directions of the bifurcation.

Potential calculation and grading ring design for ceramic insulators in 1000 kV UHV substations

The electromagnetic environment of insulators in substations is more complicated than that in transmission lines, this difference gets more prominent as the system voltage increases. Considering all the influencing factors, this paper presents the calculation results of the potential and electric field distribution of the ceramic insulator strings in 1000 kV ultra-high voltage (UHV) substations, using a three-dimensional (3-D) finiteelement method (FEM) software. Factors that affect the potential distribution such as grading ring, jumper, string structure, mounting location and drop conductors have been analyzed. The structural parameters of grading ring were optimized. A use of double ring was proposed for terminal tension insulators. A true-type test was carried out to verify the reliability of the FEM calculation method and results. The optimized grading ring configuration was successfully applied on the 1000 kV UHV pilot project in China and it was proved very effective by field observations with an ultraviolet camera.

基于阵列式多路信号采集的射击训练激光模拟系统

Existing small arms shooting training simulation system has the shortage of shot coordinate signal detection,In order to designing and solving this problem,the laser modulation technology and the multichannel data quick collection structure is introduced.The method of array multichannel modulation laser signals detection is put forward.A sort of diode string and signal detection structure is invented.The abscissa and ordinate is used to ensuring shooting coordinate,and the membrane is used for solving the problem of ordinary laser spot is too large in distance.

Suppression of Bending Vibration of Drill-Strings via an Adjustable Vibration Absorber

Vibration control of the drilling process in the gas and oil industries is of great importance. Applying an effective control system diminishes both costs and process time and increases work efficiency. Typically, the drill string vibrates in a combination of three distinct modes of transverse, torsional, and axial vibrations. Due to the importance of torsional vibration and the associated stick-slip phenomenon, many works have been devoted to this area. However, transverse vibration is another major source of vibration arisen from the long length of the drill string structure. In this paper, a tunable vibration absorber as a semiactive controller is designed to suppress the transverse vibration. After modeling the drill string as an Euler-Bernoulli beam and formulating the problem, the optimum specifications of the absorber, such as spring stiffness, absorber mass, and its position, are determined using an algorithm based on the mode summation method. The effect of bit rotational speed under the non-resonance and resonance condition is studied. It is shown that the best position of the absorber depends on the spring stiffness and bit rotational speed.

Locality from Circuit Lower Bounds

We study the locality of an extension of first-order logic that captures graph queries computable in ${AC}^0}$, i.e., by families of polynomial-size constant-depth circuits. The extension considers first-order formulas over relational structures which may use arbitrary numerical predicates in such a way that their truth value is independent of the particular interpretation of the numerical predicates. We refer to such formulas as Arb-invariant first-order. We consider the two standard notions of locality, Gaifman and Hanf locality. Our main result gives a Gaifman locality theorem: An Arb-invariant first-order formula cannot distinguish between two tuples that have the same neighborhood up to distance $(\log n)^c$, where $n$ represents the number of elements in the structure and $c$ is a constant depending on the formula. When restricting attention to string structures, we achieve the same quantitative strength for Hanf locality. In both cases we show that our bounds are tight. We also present an application of our results to the study of regular languages. Our proof exploits the close connection between first-order formulas and the complexity class ${AC}^0}$ and hinges on the tight lower bounds for parity on constant-depth circuits.

Vibration Reducing Analysis of Beam String Structure with Seismic Isolation Bearings

A vibration reducing system of seismic isolation bearings is introduced into beam string structures. The vibration control on seismic response of beam string structures (BSS) with seismic isolation bearings is discussed. Firstly finite element models for different analyses are established by using explicit dynamic analysis program LS-DYNA. Then the seismic response analyses are performed on a single beam string structure with and without seismic isolation bearings to investigate the effectiveness of the seismic isolation bearings in reducing vibration response of BSS. Furthermore, parametric analyses are conducted to examine the effects of lateral stiffness and damping of the seismic isolation bearings on seismic isolation. The analytical results indicate that the vibration reducing system can effectively reduce the vibration response of BSS against seismic force, and be applied in the vibration control of BSS.

A note on $n$-gerbes and transgressions

In this note we provide an explicit interpretation of a class of (q-1) -gerbes with multi-layered connections in terms of transgression of a fibrewise closed q -form on a fibration to a closed (q+1) -form on the base manifold, with the basic example of the Euler class of an oriented vector bundle in mind ( q \geq 0 ). Picken's and Ferreira–Gothen’s n -gerbopoles are discussed from this point of view. Furthermore, string structures (à la Cocquereaux–Pilch and à la Spera–Wurzbacher) are briefly addressed and recast within the proposed framework.

Effects of Body Doping in a NAND Flash String without Source/Drain

Cell structure using fringing field from control gate (CG) is very promising for a scaled NAND flash memory beyond sub-40 nm node. We investigated a new NAND string structure not with n-type source/drain (S/D) regions but with p-type regions in the space between gates. Even though the NAND string has a p-type region instead of n-type S/D in the space between adjacent two cells, induced layer (virtual source/drain) can be easily formed in the space by the fringing field from the CGs. When comparing a conventional NAND string with n-type S/D, the proposed structure shows better drain induced barrier leakage (DIBL) and subthreshold swing (SS) characteristics, and also shows better immunity against the process variation than conventional structure with n-type S/D. The electrical characteristics of the proposed structure were investigated as parameters of the width and doping concentration at the p/n-type region. As a NAND cell string, the current drivability of the proposed structure was also studied.

Vertical 3D NAND Flash Memory Technology

We've developed Bit Cost Scalable (BiCS) flash technology as a three-dimensional memory for the future ultra high density storage devices, which extremely reduces the chip costs by vertically stacking memory arrays with punch and plug process. We've advanced it into Pipe-shaped BiCS flash memory introducing U-shaped NAND string structure, to improve operation window, speed and reliability. 32 G bit test chips with 16 stacked layers by 60nm P-BiCS flash process have been fabricated, and the functionality of Multi-Level-Cell (MLC) operation has been successfully demonstrated. P-BiCS is the most promising candidate of three-dimensional ultra high density data storage memories.

String Structures and Trivialisations of a Pfaffian Line Bundle

The present paper is a contribution to categorial index theory. Its main result is the calculation of the Pfaffian line bundle of a certain family of real Dirac operators as an object in the category of line bundles. Furthermore, it is shown how string structures give rise to trivialisations of that Pfaffian.

Mode Jumping in Structural Damage Identification for Beam String Structure

Modal parameters are widely adopted to identify structural damages. This paper explores the mode jumping problems in damage identification for Beam string structure (BSS). The characteristics of structural mode are discussed firstly. It is found that the modal concentration is obvious for BSS, and this may cause modes after damage not in the same order as those corresponding ones before damage due to proper structural damages. The reasons for mode jumping are analyzed in detail. Based on the principle of relativity, the correspondence of the structural modes before damage and after damage can be determined by calculating the mode correlation coefficients. Numerical experiments show that this method is of higher precision, and can be applied successfully in structural damage identification for BSS.

On the structure of run-maximal strings

We present a combinatorial structure consisting of a special cover of a string by squares. We characterize the covering property of run-maximal strings, i.e. strings achieving the maximal number of runs. The covering property leads to a compression scheme which is particularly efficient for run-maximal strings. It also yields a significant speed improvement in the computer search for good run-maximal string candidates. The implementation of the search and preliminary computational results are discussed.

Luttingers wake

A strictly one-dimensional electron liquid or 'Luttinger liquid' may seem a purely theoretical construct. But measurements of the electronic structure of strings of gold atoms self-aligned on a germanium surface suggest this mythic state of matter is real, offering new possibilities to investigate and ultimately control its properties and behaviour.

CROSSED MODULE BUNDLE GERBES; CLASSIFICATION, STRING GROUP AND DIFFERENTIAL GEOMETRY

We discuss nonabelian bundle gerbes and their differential geometry using simplicial methods. Associated to a (Lie) crossed module (H → D) there is a simplicial group [Formula: see text], the nerve of the groupoid [Formula: see text] defined by the crossed module, and its geometric realization, the topological group [Formula: see text]. We introduce crossed module bundle gerbes so that their (stable) equivalence classes are in a bijection with equivalence classes of principal [Formula: see text]-bundles. We discuss the string group and string structures from this point of view. Also, we give a simplicial interpretation to the bundle gerbe connection and bundle gerbe B-field.

Analysis of Dynamic Characteristics of One-way and Crossways Beam String Structures

Analysis of Dynamic Characteristics of One-way and Crossways Beam String Structures