Modular Matrix Research Articles

Modular Matrix Converter Based Solid State Transformer for smart grids

This paper proposes a grid forming Modular Matrix Converter Based Solid State Transformer for smart grids. The Modular Matrix Converter Based Solid State Transformer regulates the voltage amplitude and frequency of the low voltage grid, enabling sag and swell mitigation. Each module includes a three-phase Matrix Converter, connected to a three-phase High Frequency Transformer, whose secondaries are connected to three Single-Phase Matrix Converters. Input and output LC filters are required to guarantee nearly sinusoidal waveforms in the MV connection and in the LV grid.The three-phase Matrix Converter uses a modified High Frequency Space Vector Modulation, with a novel feature to guarantee the non-saturation of the High Frequency Transformer at 2kHz operation. To restore the waveform that would result from the original Space Vector Modulation the High Frequency Transformer is connected to three Single-Phase Matrix Converters. Combining the advantages of Matrix Converters with high frequency operation, the volume of the galvanic isolation transformer can be reduced, and using decoupled controllers, the output voltage waveforms are regulated both in amplitude and frequency, to form a low voltage grid.The proposed Modular Matrix Converter Based Solid State Transformer is simulated and the obtained results show that it is able to regulate the secondary side voltage and frequency, even in a bidirectional power flow operation scenario, allowing power factor correction in the local MV connection, and providing mitigation capability of voltage sags and swells up to 20%, therefore improving power quality in the smart grid.

An Approach to Integrated Modularization

A modular architecture is a strategic means to deliver external variety (to the customers) and internal commonality (to the manufacturing organization). A common view is that a module should be a physical and functional building block, with well-defined and standardized interfaces between modules, and that it should be chosen for company specific reasons. Existing methodologies, such as Modular Function Deployment with the Modular Indication Matrix (MIM) representation of identified company-specific module drivers, can be used to assist the task to identify modules. Other approaches, such as clustering of the Design Structure Matrix product representation, may be used to identify modules from a technical complexity point of view. A new methodology for product modularization that integrates technical complexity and company strategies is proposed in this paper. The core of the presented methodology is to adapt the component-DSM with MIM-strategies, before clustering this hybrid representation with the previously presented IGTA++ clustering algorithm. The proposed methodology is exemplified and logically verified with an industrial test rig modularization case. The modular test rig architecture chosen with the new methodology is shown to have 53% less complexity, as defined by Pugh, compared with the original architecture, and it could potentially reduce the risk of design mistakes, and reduce the development time by up to 70%. It is also estimated that it would be possible to reuse up to 57% of the modules, in future test rig redesign projects, which indicates potentially large savings in cost and development time.

Independent Control of Input Current, Output Voltage, and Capacitor Voltage Balancing for a Modular Matrix Converter

This paper presents a novel control scheme for the modular matrix converter (MMxC), in terms of balancing capacitor voltages in addition to controlling output voltage and input current along with a comprehensive mathematical model. The proposed technique has been designed based on a fully decoupled current control of the positive-, negative-, and zero-sequence components of each MMxC subconverter in addition to the feedforward instantaneous power control to suppress the capacitor voltages fluctuation. The frequency of the zero-sequence is the output frequency for the load. Therefore, the positive-sequence current component is used to control the input current to achieve unity input power factor, the negative-sequence current component is used to balance the capacitor voltages among all MMxC arms, and the zero-sequence current component is used to control the output voltage. The effectiveness of the proposed control scheme for controlling the MMxC has been verified theoretically, using simulation software, and experimentally, using a laboratory prototype based 3 kVA, 200 V.

Structure and unfolding of the third type III domain from human fibronectin.

Fibronectin is a modular extracellular matrix protein that is essential for vertebrate development. The third type III domain (3FN3) in fibronectin interacts with other parts of fibronectin and with anastellin, a protein fragment that causes fibronectin aggregation. 3FN3 opens readily both as an isolated domain in solution and when part of fibronectin in stretched fibrils, and it was proposed that this opening is important for anastellin binding. We determined the structure of 3FN3 using nuclear magnetic resonance spectroscopy, and we investigated its stability, folding, and unfolding. Similar to most other FN3 domains, 3FN3 contains two antiparallel β-sheets that are composed of three (A, B, and E) and four (C, D, F, and G) β-strands, respectively, and are held together by a conserved hydrophobic interface. cis-trans isomerization of P847 at the end of β-strand C leads to observable conformational heterogeneity in 3FN3, with a cis peptide bond present in almost one-quarter of the molecules. The chemical stability of 3FN3 is relatively low, but the folding rate constant in the absence of denaturant is in the same range as those of other, more stable FN3 domains. Interestingly, the unfolding rate constant in the absence of denaturant is several orders of magnitude higher than the unfolding rate constants of other FN3 domains investigated to date. This unusually fast rate is comparable to the rate of binding of 3FN3 to anastellin at saturating anastellin concentrations, consistent with the model in which 3FN3 has to unfold to interact with anastellin.

負荷周波数が電源周波数に同期したときのモジュラーマトリックスコンバータ制御

負荷周波数が電源周波数に同期したときのモジュラーマトリックスコンバータ制御

Chiral spin liquid in a frustrated anisotropic kagome Heisenberg model.

Kalmeyer-Laughlin (KL) chiral spin liquid (CSL) is a type of quantum spin liquid without time-reversal symmetry, and it is considered as the parent state of an exotic type of superconductor--anyon superconductor. Such an exotic state has been sought for more than twenty years; however, it remains unclear whether it can exist in a realistic system where time-reversal symmetry is breaking (T breaking) spontaneously. By using the density matrix renormalization group, we show that KL CSL exists in a frustrated anisotropic kagome Heisenberg model, which has spontaneous T breaking. We find that our model has two topological degenerate ground states, which exhibit nonvanishing scalar chirality order and are protected by finite excitation gap. Furthermore, we identify this state as KL CSL by the characteristic edge conformal field theory from the entanglement spectrum and the quasiparticles braiding statistics extracted from the modular matrix. We also study how this CSL phase evolves as the system approaches the nearest-neighbor kagome Heisenberg model.

A review of offshore wind turbine nacelle: Technical challenges, and research and developmental trends

The turbine nacelle with traditional wind power generation system is heavy, especially in offshore applications due to the large mass of the power frequency step-up-transformer operated at 50 or 60 Hz, and copper conductor generator. For example, the weight and volume of a 0.69/33 kV 2.6 MVA transformer are typically in the range of 6–8 t and 5–9 m 3 , respectively. The weight for a 10 MW direct drive permanent magnet generator is about 300 t. These penalties significantly increase the tower construction, and turbine installation and maintenance costs. The tower cost represents 26% of the total component cost of the turbine and on average about 20% of the capital costs are associated with installation. Typical maintenance cost of an offshore wind turbine is about 2.3 cents/kWh, which is 20% higher than that of an onshore based turbine. As alternative approaches to achieve a compact and lightweight offshore wind turbine nacelle, different concepts have been proposed in recent years, such as step-up-transformer-less system, medium-frequency (in the range of a few kHz to MHz) power transformer-based system, multilevel and modular matrix converter-based system and superconducting generator-based system. This paper aims to review the technical challenges, current research and developmental trends, and possible future directions of the research to reduce the weight and volume of the nacelle. In addition, a comprehensive review of traditional wind power generation technologies is conducted in this article as well.

Minimal entangled states and modular matrix for fractional quantum Hall effect in topological flat bands

We perform an exact diagonalization study of the topological order in topological flat band models through calculating entanglement entropy and spectra of low energy states. We identify multiple independent minimal entangled states, which form a set of orthogonal basis states for the ground-state manifold. We extract the modular transformation matrices S (U) which contains the information of mutual (self) statistics, quantum dimensions and fusion rule of quasi-particles. Moreover, we demonstrate that these matrices are robust and universal in the whole topological phase against different perturbations until the quantum phase transition takes place.

Generalised analytical methods and current‐energy control design for modular multilevel cascade converter

Modular multilevel cascade converter (MMCC) is a family of the emerging multilevel converters that are configured with a cascaded connection of full-bridge submodules or half-bridge ones by distinct topological structures. So far, MMCC family can be classified by basic configurations and submodule types into single-star full-bridge, double-star half-bridge (modular multilevel converter (MMC)), double-star full-bridge, double-star half-bridge back-to-back (indirect MMC), triple-star full-bridge (modular multilevel matrix converter, M3C), single-delta full-bridge and double-delta full-bridge (Hexverter). This study introduces a generalised and standard analytical procedure for MMCC and deals with the double-star half-bridge case (MMC) as example. A particular defined circulating current with a clearer physical meaning is used to analyse the complicated branch current composition and branch energy fluctuation. A full mathematical model based on state-space equations is established for MMC and a corresponding energy-current control strategy is presented. The validity of the control design and effectiveness of MMC is confirmed by simulation and experiment.

New Practical Algebraic Public-Key Cryptosystem and Some Related Algebraic and Computational Aspects

The most popular present-day public-key cryptosystems are RSA and ElGamal cryptosystems. Some practical algebraic generalization of the ElGamal cryptosystem is considered-basic modular matrix cryptosystem (BMMC) over the modular matrix ring M2(Zn). An example of computation for an artificially small number n is presented. Some possible attacks on the cryptosystem and mathematical problems, the solution of which are necessary for implementing these attacks, are studied. For a small number n, computational time for compromising some present-day public-key cryptosystems such as RSA, ElGamal, and Rabin, is compared with the corresponding time for the ВММС. Finally, some open mathematical and computational problems are formulated.

Nanomechanics of Ig-like domains of human contactin (BIG-2)

Contactins are modular extracellular cell matrix proteins that are present in the brain, and they are responsible for the proper development and functioning of neurons. They contain six immunoglobulin-like IgC2 domains and four fibronectin type III repeats. The interactions of contactin with other proteins are poorly understood. The mechanical properties of all IgC2 domains of human contactin 4 were studied using a steered molecular dynamics approach and CHARMM force field with an explicit TIP3P water environment on a 10-ns timescale. Force spectra of all domains were determined computationally and the nanomechanical unfolding process is described. The domains show different mechanical stabilities. The calculated maxima of the unfolding force are in the range of 900–1700 pN at a loading rate of 7 N/s. Our data indicate that critical regions of IgC2 domains 2 and 3, which are responsible for interactions with tyrosine phosphatases and are important in nervous system development, are affected by even weak mechanical stretching. Thus, tensions present in the cell may modulate cellular activities related to contactin function. The present data should facilitate the interpretation of atomic force microscope single-molecule spectra of numerous proteins with similar IgC2 motives. FigureThe general fold of IgC2 domains of contactin 4 protein. Vectors show directions of pulling forces applied in mechanical unfolding computer experiments. Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-011-1010-y) contains supplementary material, which is available to authorized users.

Multi‐objective topology optimisation for microstructure of periodic composite material

By using the homogenisation method and finite element method (FEM) jointly, a multi‐objective optimisation model for the microstructure of a periodic composite material was developed in which the objective was to maximise the weighted sum of the main diagonal elements of the equivalent elasticity modular matrix and to restrain the amount of material in the microstructure. An optimisation of material distribution in the microstructure was carried out. In the optimisation, the design objective and material distribution were controlled by the optimisation criteria method and the chequerboard influence was eliminated using the sensitivity filter method. Influences of volume fraction and finite element (FE) mesh sizes on the optimal microstructures are discussed. Numerical examples indicate that the present optimisation model and method are effective.

Applying linear algebra routines to modular ore polynomial matrix algorithms

Applying linear algebra routines to modular ore polynomial matrix algorithms

Zinc Induces Structural Reorganization of Gelatin Binding Domain from Human Fibronectin and Affects Collagen Binding

Fibronectin is a modular extracellular matrix protein involved in cell adhesion, cell motility, wound healing, and maintenance of cell morphology. It is composed of multiple repeats of three distinct modules: F(I), F(II), and F(III). Various combinations of these modules create fragments able to interact with different constituents of the extracellular matrix. Here, we present the 2.5-A resolution crystal structure of its 45-kDa gelatin-binding domain (GBD; 6F(I)-1F(II)-2F(II)-7F(I)-8F(I)-9F(I)), which also corresponds to the C-terminal half of the migration stimulating factor, a Fn splice variant expressed in human breast cancers. GBD forms a very compact zinc-mediated homodimer, in stark contrast with previous structures of fibronectin fragments. Most remarkably, 8F(I) no longer adopts the canonical F(I) fold but is composed of two long strands that associate with 7F(I) and 9F(I) into a large beta-sheet superdomain. Binding studies in solution confirmed that Zn induces conformational rearrangements and causes loss of binding of Fn-GBD to high-affinity collagen peptides. These data suggest the Zn may play a regulatory role for the cellular functions of fibronectin.

A New Method for Analysing Large Elasto-Plastic Deformations of a Thin Cosserat Shell

One of the best approaches for modelling the large deformation of shells is the Cosserat surface; however, the finite-element implementation of this model suffers from membrane and shear locking, especially for very thin shells. If the director vector is constrained to remain perpendicular to the mid-surface, during deformation, locking will be prevented. This constraint is in fact a limiting analysis of the Cosserat theory in which Kirchhoff's hypothesis is enforced. This has been considered for the first time. Simo's plastic approach is modified to implement the constrained director. This model includes both kinematic and isotropic hardening behaviours. A consistent elasto-plastic tangent modular matrix is extracted. Numerical solution is performed by interpolation of displacement on the whole domain, and a hierarchical finite-element scheme is developed. The principle of virtual work is used to obtain the weak form of the governing differential equations and the material and geometric stiffness matrices are derived through a linearization process. The validity and the accuracy of the method are illustrated by numerical examples.

Predicting strength and function for promoters of the Escherichia coli alternative sigma factor, σ E

Sequenced bacterial genomes provide a wealth of information but little understanding of transcriptional regulatory circuits largely because accurate prediction of promoters is difficult. We examined two important issues for accurate promoter prediction: (1) the ability to predict promoter strength and (2) the sequence properties that distinguish between active and weak/inactive promoters. We addressed promoter prediction using natural core promoters recognized by the well-studied alternative sigma factor, Escherichia coli sigma(E), as a representative of group 4 sigmas, the largest sigma group. To evaluate the contribution of sequence to promoter strength and function, we used modular position weight matrix models comprised of each promoter motif and a penalty score for suboptimal motif location. We find that a combination of select modules is moderately predictive of promoter strength and that imposing minimal motif scores distinguished active from weak/inactive promoters. The combined -35/-10 score is the most important predictor of activity. Our models also identified key sequence features associated with active promoters. A conserved "AAC" motif in the -35 region is likely to be a general predictor of function for promoters recognized by group 4 sigmas. These results provide valuable insights into sequences that govern promoter strength, distinguish active and inactive promoters for the first time, and are applicable to both in vivo and in vitro measures of promoter strength.

Modular bootstrap in Liouville field theory

The modular matrix for the generic 1-point conformal blocks on the torus is expressed in terms of the fusion matrix for the 4-point blocks on the sphere. The modular invariance of the toric 1-point functions in the Liouville field theory with DOZZ structure constants is proved.

A Radial Return Algorithm Application in Elastoplastic Frame Analysis Using Plastic Hinge Approach

A new method is presented for first-order elastoplastic analysis of framed structures using a radial return predictor/corrector solution strategy. The proposed method assumes plastic hinge formation coupled with a yield surface. The yield surface is defined as a general function of axial force, shear forces, twisting, and biaxial bending moments on the cross-section of the frame. The material is regarded as linear and elastic-perfect plastic. The plastic deformations are governed by the normality criterion. Combining the Newton-Raphson method and the radial return algorithm, a consistent tangent modular matrix is proposed and fast and converging algorithms are presented. Examples demonstrate the accuracy and effectiveness of the proposed method.

The PET/CT Report: The Most Important Part of the Study

<h3>Abstract</h3> The field of three-dimensional (3D) bioprinting has advanced rapidly in recent years. Significant reduction in the costs associated with obtaining functional 3D bioprinting hardware platforms is both a cause and a result of these advances. As such, there are more laboratories than ever integrating bioprinting methodologies into their research. However, there is a lack of standards in the field of biofabrication governing any requirements or characteristics to support cross-compatibility with biomaterial bioinks, hardware, and different tissue types. Here we describe a modular extracellular matrix (ECM) inspired bioink comprised of collagen and hyaluronic acid base components that: 1) employ reversible internal hydrogen bonding forces to generate thixotropic materials that dynamically reduce their elastic moduli in response to increased shear stress, thus enabling increased compatibility with printing hardware; and 2) modular addons in the form of chemically-modified fibronectin and laminin that when covalently bound within the bioink support a variety of tissue types, including liver, neural, muscle, pancreatic islet, and adipose tissue. These features aim to accelerate the deployment of such bioinks for tissue engineering of functional constructs in the hands of various end users.

On graphs of central episturmian words

Episturmian sequences are a natural extension of Sturmian sequences to the case of finite alphabets of arbitrary cardinality. In this paper, we are interested in central episturmian words, or simply, epicentral words, i.e., the palindromic prefixes of standard episturmian sequences. An epicentral word admits a variety of faithful representations including as a directive word, as a certain type of period vector, as a Parikh vector, as a certain type of Fine and Wilf extremal word, as a suitable modular matrix, and as a labeled graph. Various interconnections between the different representations of an epicentral word are analyzed. In particular, we investigate the structure of the graphs of epicentral words proving some curious and surprising properties.