Asymmetric Part Research Articles

Basic quantities of the equation of state in isospin asymmetric nuclear matter

Based on the Hugenholtz–Van Hove theorem, six basic quantities of the EoS in isospin asymmetric nuclear matter are expressed in terms of the nucleon kinetic energy t(k), the isospin symmetric and asymmetric parts of the single-nucleon potentials \(U_0(\rho ,k)\) and \(U_{\text {sym},i}(\rho ,k)\). The six basic quantities include the quadratic symmetry energy \(E_{\text {sym,2}}(\rho )\), the quartic symmetry energy \(E_{\text {sym,4}}(\rho )\), their corresponding density slopes \(L_2(\rho )\) and \(L_4(\rho )\), and the incompressibility coefficients \(K_2(\rho )\) and \(K_4(\rho )\). By using four types of well-known effective nucleon–nucleon interaction models, namely the BGBD, MDI, Skyrme, and Gogny forces, the density- and isospin-dependent properties of these basic quantities are systematically calculated and their values at the saturation density \(\rho _0\) are explicitly given. The contributions to these quantities from t(k), \(U_0(\rho ,k)\), and \(U_{\text {sym},i}(\rho ,k)\) are also analyzed at the normal nuclear density \(\rho _0\). It is clearly shown that the first-order asymmetric term \(U_{\text {sym,1}}(\rho ,k)\) (also known as the symmetry potential in the Lane potential) plays a vital role in determining the density dependence of the quadratic symmetry energy \(E_{\text {sym,2}}(\rho )\). It is also shown that the contributions from the high-order asymmetric parts of the single-nucleon potentials (\(U_{\text {sym},i}(\rho ,k)\) with \(i>1\)) cannot be neglected in the calculations of the other five basic quantities. Moreover, by analyzing the properties of asymmetric nuclear matter at the exact saturation density \(\rho _{\text {sat}}(\delta )\), the corresponding quadratic incompressibility coefficient is found to have a simple empirical relation \(K_{\text {sat,2}}=K_{2}(\rho _0)-4.14 L_2(\rho _0)\).

Role of Symmetry in Quantum Search via Continuous-Time Quantum Walk

For quantum search via the continuous-time quantum walk, the evolution of the whole system is usually limited in a small subspace. In this paper, we discuss how the symmetries of the graphs are related to the existence of such an invariant subspace, which also suggests a dimensionality reduction method based on group representation theory. We observe that in the one-dimensional subspace spanned by each desired basis state which assembles the identically evolving original basis states, we always get a trivial representation of the symmetry group. So, we could find the desired basis by exploiting the projection operator of the trivial representation. Besides being technical guidance in this type of problem, this discussion also suggests that all the symmetries are used up in the invariant subspace and the asymmetric part of the Hamiltonian is very important for the purpose of quantum search.

Effect of Geometrical Factors on Torsion in Cold Roll Forming of the Lower Side Beam of a Car

Cold roll forming is a continuous metal forming process used to produce a large variety of profiles. A significant product of cold roll forming is asymmetric profiles, whose application is expanding in the construction of cars, houses, bridges, etc. Torsion is one of the common defects in the cold roll forming process of asymmetric section steel and sometimes seriously affects cold roll forming products. With the development of the economy and technology, many asymmetric cold roll-formed parts are being gradually applied to automobiles. Three-dimensional finite element analysis models of 12 stands with 700L sheet material were carried out using the professional COPRA RF and MSC MARC software, taking the lower beam of an automobile as the research object. Five geometric factors of the lower side beam were researched, and the influence rules of different geometric elements on the forming torsion were analyzed. We found that with the increase of web width, flange width, and vertical edge height and the decrease of the corner radius and strip thickness, the torsion defects of cold roll forming were improved to different degrees. The results also showed that the width of the flange has the most significant effect on torsion.

Microstructures, mechanical properties and solidification mechanism of a hot tearing sensitive aluminum alloy asymmetric part fabricated by squeeze casting

In this work, 7075 Al alloy, a high-strength wrought aluminum alloy with high hot tearing sensibility, was used in the squeeze casting of an asymmetric part. The solidification defects, microstructures and mechanical properties of the part solidified under different forming pressures were studied. Furthermore, the uniformities of the microstructures, mechanical properties and the solidification mechanisms were investigated. Results show that increasing the forming pressure is helpful to improve the liquid/solid feeding for counteracting the particularly serious shrinkage during the wide mushy zone of 7075 Al alloy. Therefore, the solidification defect can be avoided. Moreover, increasing the forming pressure is helpful to not only obtaining fine equiaxed grains, but also diminishing the intergranular segregation of alloying elements. With the increasement of forming pressures, the strengths of the part increased, along with the decreases in the ductile due to the work hardening resulted from the serious solid feeding. The microstructures and mechanical properties are impacted by the solidification rate of the melt at different regions. When the forming pressure was 150 MPa, fine microstructures and excellent mechanical properties were obtained. The uniformity of the microstructures and mechanical properties are dominated by the solidification location sequence of the melt. Further on, it is determined by the thermal gradient of the melt at different locations. For 7xxx series alloys, more solid feeding is needed for counteracting the serious shrinkage at the first solidified regions, causing a work hardening and associated strengths increasements. A near uniform part thickness and direct feeding loads are appreciated to improve the uniformities. In this work, the optimal tensile properties tested in the part were tested to be as follows: the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) are 345.5 MPa, 483.2 MPa, and 7.6%, respectively. The UTS uniformity is tested to be 86.4%.

The study of the welding relief shape influence on the linear friction welding process

The study of the welding process of asymmetric parts made of Ti-6A1-4V alloy was made to expand the field of application of the process of linear friction welding and to improve the use of technology of existing assemblies. During of the study, it was found that the process of welding T-joints has features in a longer duration of the unsteady stage and an increase in the amplitude value of the shear force during the steady state. Welded joints do not contain seam flaws over the area of the welded joint, which it made unnecessary to assign an allowance along the perimeter of the welded section. The change in conditions at the joint is expressed in an increase in the microhardness of the welded seam in comparison with the Ti-6A1-4V joints, which are produced by the traditional technology more than 50 HV.

A modified Zerilli–Armstrong model as the asymmetric visco-plastic part of a multi-mechanism model for cutting simulations

A modified Zerilli–Armstrong model as the asymmetric visco-plastic part of a multi-mechanism model for cutting simulations

Constraints on the Latitudinal Profile of Jupiter's Deep Jets

AbstractThe observed zonal winds at Jupiter's cloud tops have been shown to be closely linked to the asymmetric part of the planet's measured gravity field. Here, we examine to what extent, and at which latitudes, must the flows at depth resemble those at the cloud level to match the gravity signal. We show, using both the symmetric and asymmetric parts of the measured gravity field, that the observed cloud‐level wind profile between 25°S and 25°N must extend unaltered to depths of thousands of kilometers. Poleward, the midlatitude deep jets also contribute to the gravity signal, but might differ somewhat from the cloud‐level winds. We analyze the likelihood of this difference and give bounds to its strength. We also find that to match the gravity measurements, the winds must project inward in the direction parallel to Jupiter's spin axis, and decay inward in the radial direction.

Accurate feature extraction for multimodal biometrics combining iris and palmprint

Multimodal biometric systems provide a way to combat with the limitations of a unimodal biometric system which include less accuracy and user acceptability. In this context, a coding based approach called bit-transition code, is proposed for addressing the less-explored problem of designing a biometric-based authentication system by combining the iris and palmprint modalities. The approach is based on the encoding of binary transitions of symmetric and asymmetric parts of the Gabor filtered images at all pixel locations. Score-level fusion is employed to integrate the individual iris and palmprint performances. Experiments are carried out with three benchmark iris/palmprint databases, namely IITD iris and palmprint databases and PolyU palmprint database. The performance is measured in terms of receiver operator characteristics (ROC) curves and other metrics, like equal error rate and area under ROC curves. A comprehensive comparison, with several state-of-the-art approaches, is presented in order to validate the usefulness of the proposed approach.

Synaptic learning rules for sequence learning.

Remembering the temporal order of a sequence of events is a task easily performed by humans in everyday life, but the underlying neuronal mechanisms are unclear. This problem is particularly intriguing as human behavior often proceeds on a time scale of seconds, which is in stark contrast to the much faster millisecond time-scale of neuronal processing in our brains. One long-held hypothesis in sequence learning suggests that a particular temporal fine-structure of neuronal activity - termed 'phase precession' - enables the compression of slow behavioral sequences down to the fast time scale of the induction of synaptic plasticity. Using mathematical analysis and computer simulations, we find that - for short enough synaptic learning windows - phase precession can improve temporal-order learning tremendously and that the asymmetric part of the synaptic learning window is essential for temporal-order learning. To test these predictions, we suggest experiments that selectively alter phase precession or the learning window and evaluate memory of temporal order.

A Fully Symmetrical High Performance Modular Milling Cutter

Milling cutters belong to a widely used category of cutting tools. In this category, modular milling cutters are a narrow niche, less studied, and developed. Usually, they are symmetrical cutting tools. A milling cutting tool that can be reconfigured due to its modularity and still keeps its symmetry becomes more interesting and useful for machining. The paper presents such a new concept in a computer aided design (CAD) model of a cutting tool based on some novel features. The tool itself is designed as a modular complex. The way the torque is transmitted from the shaft to the elementary cutters is an original one, as they are joined together based on a profiled assembling. The profile is one formed of filleted circular sectors and segments. The reaming of the elementary cutters has two sections each of them assuming a task: transmitting the torque, and precisely centring, respectively. The cooling system, which is a component of the tool, provides the cutting area with coolant both on the front and side face of the cutting tool. Some nozzles placed around the cutting tool send jets or curtains of coolant towards the side surface of the cutter, instead of parallel, as some existing solutions do. The source of the coolant supply is the inner cooling system of the machine tool. This provides the tool with coolant having proper features: high enough flow and pressure. The output of the research is a CAD-based model of the modular milling cutter with a high performance cooling system. All of this model’s elements were designed taking into account the design for manufacturing principles, so it will be possible to easily manufacture this tool. Several variants of milling cutters obtained by reconfiguring the complex tool are presented. Even if the tool is usually a symmetric complex, it can process asymmetric parts. Symmetry is intensively used to add some advantages to the modular cutting tool: balanced forces in the cutting process, the possibility of controlling the direction of the axial cutting force, and a good machinability of the grooves used to assemble the main parts of the cutting tool.

Analysis of the skin wrinkling in out-of-plane joints of CFRP hat-shaped structure

Abstract Out-of-plane joints, between hat (omega) stiffeners and skin panels are asymmetric parts of the composite structure. Studies show that physical-mechanical conditions in these joints significantly affect skin forming quality. In the present article, aimed to investigate the mechanism of the skin wrinkle in the joints of carbon fiber reinforced plastics (CFRP) hat-shaped structure, the pressure testing apparatus based on the Pascal principle is used to surveillance the resin pressure dynamically in out-of-plane joints. In this regard, several influencing factors such as first-order holding time, forming pressure and relative volume of unidirectional fillers are studied. Obtained results show that increasing the first stage holding time can prolong the viscous flow state of the resin, and time to achieve pressure equalization at each detection point, thereby improving the dispersion of the pressure and reducing the possibility of wrinkles. It is found that as the forming pressure increases, the degree of skin wrinkles in the out-of-plane joints ameliorates. Moreover, for fillers with a relative volume within the range of 0–50%, the pressure transfer effect and the skin flatness is relatively dissatisfactory. It is concluded that the filler with a relative volume of 80–120% improves the skin wrinkle in out-of-plane joints.

КЛАСТЕРНЫЙ АНАЛИЗ РЕЗНЫХ ТЕРРАСНЫХ ОКОН ВОТКИНСКА

Terraced windows, along with frames, are a unique element of Russian wooden architecture. But if in the major cities of the Pre-Urals, the old wooden quarters were demolished for serial building in the middle of the 20th century, the center of Votkinsk retained its almost original appearance of the mid-19th century. As a result, the carved terraced windows are no longer so massively represented in other cities of Udmurtia and the Urals. Nevertheless, due to economic activity, the private sector of Votkinsk is actively being built up, and the owners of wooden houses that are not architectural monuments everywhere are replacing carved terraced windows with plastic windows that are more comfortable in everyday life. As a result, it is likely that in a couple of decades such an expressive element of Russian wooden architecture as the Votkinsk carved terrace windows can be lost forever. Therefore, the objective of this work consisted, firstly, in photo fixing windows still available in Votkinsk, and secondly, in their cluster analysis to identify typical signs. Their definition is necessary, for example, if, with the improvement of the production technology of serial windows, it again becomes possible to return this element of architecture, then the starting point can be not only simple imitations of preserved monuments of wooden architecture, but the existing database in all its richness of forms. In 2013-2015 the authors surveyed 35 terrace windows of Votkinsk were surveyed, mainly central streets: Kirov, May 1 and Lenin, which are presented in the appendix. During cluster analysis, it was revealed that the most common type of window consists of three modules with an arched completion with the same width of modules. As a rule, the upper part of the window consists of three elements, divided by straight partitions. The ornament of the window itself, as a rule, has axial symmetry and consists of two parts. The presence of elements that are difficult to manufacture, including semicircular and parabolic ornament lines, testifies to the high production culture and craftsmanship of the workers who made the terrace windows, the production technology of which was possible only in the workshop or artel conditions. Undoubtedly, the influence on the windows of the neo-Gothic style, which could have been brought to Votkinsk by invited foreign experts. Local culture also had a great influence. But Udmurt motifs are extremely limited, as evidenced, for example, by the lack of asymmetric parts built on the principle of rotation. In addition, obviously Orthodox motifs have been found, for example, the use of the triptychiconostasis form, ornaments in the form of a “forked” cross superimposed on the silhouette of an Orthodox church cloth. In general, Votkinsk terrace windows can be considered as a unique cultural phenomenon on the territory of Udmurtia, which is so massively not found now.

Assembly of single-deck small vessels from volumetric asymmetric parts

A comparative analysis of the structural and technological features of the assembly of multi-deck and single-desk vessels of presented, indicating the distribution of the volume of saturation of the latter with pipe elements, systems and mechanisms. On the basis of the principles of zonal aggregation, a solution to the zonal module of the engine room of small vessels is proposed. In order to eliminate the diffi culties of assembling the hulls if single-deck small vessels and mounting saturation in them a new scheme for dividing these hulls into two volumetric asymmetric parts with the allocation of the engine room module, extremities, deckhouse and burl is considered. The calculated data on the reduction of labor intensity and duration of the assembly of hulls of single-desk small vessels in the implementation of their division according to the new scheme are given.

On non-axisymmetric buckling modes of inhomogeneous circular plates

Unsymmetrical buckling of nonuniform circular plates with elastically restrained edge and subjected to normal pressure is studied in this paper. The asymmetric part of the solution is sought in terms of multiples of the harmonics of the angular coordinate. A numerical method is employed to obtain the lowest load value at which waves in the circumferential direction can appear. The effect of material heterogeneity and boundary on the buckling load is examined. For a plate with elastically restrained edge, the buckling pressure and mode number increase with a rise of spring stiffness. Increasing of the elasticity modulus to the plate edge leads to increasing of the buckling pressure, but the mode number does not change. If the translational flexibility coefficient is small, decreasing of the elasticity modulus to the shell (plate) edge leads to sufficient lowering of the buckling pressure.

Non-reciprocal acoustics in a viscous environment.

It is demonstrated that acoustic transmission through a phononic crystal with anisotropic solid scatterers becomes non-reciprocal if the background fluid is viscous. In an ideal (inviscid) fluid, the transmission along the direction of broken P symmetry is asymmetric. This asymmetry is compatible with reciprocity since time-reversal symmetry (T symmetry) holds. Viscous losses break T symmetry, adding a non-reciprocal contribution to the transmission coefficient. The non-reciprocal transmission spectra for a phononic crystal of metallic circular cylinders in water are experimentally obtained and analysed. The surfaces of the cylinders were specially processed in order to weakly break P symmetry and increase viscous losses through manipulation of surface features. Subsequently, the non-reciprocal part of transmission is separated from its asymmetric reciprocal part in numerically simulated transmission spectra. The level of non-reciprocity is in agreement with the measure of broken P symmetry. The reported study contradicts commonly accepted opinion that linear dissipation cannot be a reason leading to non-reciprocity. It also opens a way for engineering passive acoustic diodes exploring the natural viscosity of any fluid as a factor leading to non-reciprocity.

The comparative analysis of the properties and structures of purine nucleoside phosphorylases from thermophilic bacterium Thermus thermophilus HB27

Two recombinant purine nucleoside phosphorylases from thermophilic bacterium Thermus thermophilus HB27 encoded by genes TT_C1070 (TthPNPI) and TT_C0194 (TthPNPII) were purified and characterized. The comparative analysis of their sequences, molecular weight, enzymes specificity and kinetics of the catalyzed reaction were realized. As a result, it was determined that the TthPNPI is specific to guanosine while the TthPNPII to adenosine. According to the results of the size exclusion chromatography and SAXS study both enzymes are hexameric molecules. Based on the sequence alignment with homologous purine nucleoside phosphorylases (PNPs), Asn was identified as a purine base recognizing residue in the active site of TthPNPI and Asp in TthPNPII. The three-dimensional structure of TthPNPII was solved at 2.5 Å resolution by molecular replacement method using crystals grown in microgravity. Position of phosphate in the active site cavity is located. The possible arrangement of adenosine and guanosine in TthPNPII active site cavity is considered using superposition with the structures of homologous trimeric and hexameric PNPs complexed with corresponding substrates. The peculiarities of oligomeric structure of TthPNPII in comparison with homologous PNPs are described. It is shown that two trimeric molecules of TthPNPII in the asymmetric part of the unit cell are connected by three two-fold axis into a hexamer with 32-point symmetry. This type of hexameric structure of PNP is found for the first time. The interface area between the subunits in trimeric molecule and between the trimers in TthPNPII hexamer is described. Communicated by Ramaswamy H. Sarma.

Synthesis, crystal structure and luminescent properties of isoreticular lanthanide–organic frameworks based on a tetramethyl-substituted terphenyldicarboxylic acid

A series of 3D metal–organic frameworks derived from 2′,3′,5′,6′-tetramethyl-[1,1′:4′,1′′-terphenyl]-4,4′′-dicarboxylic acid (H2L) as organic linker and various lanthanides have been prepared. The resulting coordination polymers [Ln3L4(NO3)(DMF)x(H2O)]n (where x = 2 or 3) were characterized by elemental analysis, thermogravimetric investigations, IR and TG-FTIR spectroscopy, as well as powder X-ray diffraction measurements. The crystal structure for six of these isostructural networks based on La(III), Ce(III), Nd(III), Sm(III), Tb(III) and Dy(III) was established using single crystal X-ray crystallography. As an example, the asymmetric part of [La3L4(NO3)(DMF)3(H2O)]n consists of two deprotonated ligand molecules L2- and two La(III) ions, one of them occupying a general position with full site occupancy, while the other one has a fractional occupancy of 0.5. Investigation of the luminescence of these coordination polymers showed that compounds containing La3+, Nd3+ and Gd3+ possess only the emission associated with the anion of the organic ligand (L2-), polymers containing Eu3+ and Tb3+ show pure metal-centered radiation, while networks containing Dy3+ and Sm3+ display dual metal- and ligand-centered luminescence. The organic linker acts as a good antenna for Tb3+, Eu3+, Dy3+ and Sm3+ ions.

Connection and Control Strategy of PV Converter Integrated into Railway Traction Power Supply System

In order to supply the single-phase locomotive load and mitigate the negative sequence current, this paper develops a V/V transformer-based connection and control strategy of three-phase photovoltaic (PV) converters integrated into railway traction power supply systems. In this V/V transformer-based connection, the two-phase traction voltage is converted into the three-phase voltage. This approach can offer a common low voltage AC bus, which is more convenient for more access to three-phase PV converters. Based on this V/V transformer-based connection, an individual phase current control strategy with the hybrid current reference is fully designed. In this control strategy, the current reference, containing two parts, is generated. One is the asymmetrical part for powering the single-phase locomotive load and mitigating the negative sequence current. The other is the symmetrical part for feeding the surplus power back to the utility grid. Then, each phase current replaces the dual-sequence current to be controlled to track the corresponding phase current reference. Consequently, PV converters can flexibly inject the symmetrical and asymmetrical currents without the dual-sequence extraction for a simpler implementation. Finally, the effectiveness of the developed connection and control strategy is validated by the simulation studies.

A Variational Method for Analyzing Vortex Flows in Radar-Scanned Tornadic Mesocyclones. Part I: Formulations and Theoretical Considerations

AbstractA variational method is formulated with theoretical considerations for analyzing vortex flows in Doppler radar–scanned tornadic mesocyclones. The method has the following features. (i) The vortex center axis (estimated as a continuous function of time and height in the four-dimensional space) is used as the vertical coordinate, so the coordinate system used for the analysis is slantwise curvilinear and nonorthogonal in general. (ii) The vortex flow (VF), defined by the three-dimensional vector wind minus the horizontal moving velocity of vortex center axis, is expressed in terms of the covariant basis vectors (tangent to the coordinate curves), so its axisymmetric part can be properly defined in that slantwise-curvilinear coordinate system. (iii) To satisfy the mass continuity automatically, the axisymmetric part is expressed by the scalar fields of azimuthally averaged tangential velocity and cylindrical streamfunction and the remaining asymmetric part is expressed by the scalar fields of streamfunction and vertically integrated velocity potential. (iv) VF-dependent covariance functions are formulated for these scalar variables and then deconvoluted to construct the square root of background error covariance matrix analytically with the latter used to transform the control vector to precondition the cost function. (v) The deconvoluted covariance functions and their transformed control variables satisfy two required boundary conditions (i.e., zero vertical velocity at the lower rigid boundary and zero cross-axis velocity along the vortex center axis), so the analyzed VF satisfies not only the mass continuity but also the two boundary conditions automatically.

Cationic amphiphiles based on malonic acid amides as transfection mediators

Objectives. The aim of this work is to synthesize cationic amphiphiles based on malonic acid amides. The target compounds should contain saturated and unsaturated alkyl chains in the hydrophobic portion, and one or two positive charges in the polar head as created by ethylenediamine and amino acid L-ornithine. For such cationic amphiphiles, we determined physicochemical properties and transfection efficiency of liposomes based on them.Methods. The initial compound in the synthesis is diethylmalonate. We used C-alkylation to add the first hydrophobic chain (with octylbromide, dodecylbromide, or octadecylbromide). N-oleylamine was used as the second hydrophobic chain, which was attached at the carboxyl group of the malonic acid via amide bond formation. The polar head was represented by ethylenediamine, which was then attached at the second carboxyl group of the malonic acid. Further, L-ornithine was attached to ethylenediamine to produce cationic lipids with two positive charges in the head group. The structures of the compounds were characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, and elemental analysis. Particle size distribution was evaluated by photon correlation spectroscopy. The luciferase test was used to determine transfection efficiency using HeLa cells.Results. We have developed a synthesis scheme to produce new cationic amphiphiles with an asymmetric hydrophobic part. The obtained liposomal particles are approximately 120 nm in size and have a relatively high zeta potential of 29–30 mV.Conclusions. The size of these liposomes allows them to penetrate into cells, which makes it possible to use these compositions for transfection. The high zeta potential shows that the particles are stable. Our results demonstrate that the transfection efficiency of our liposomes (mixed with cholesterol) is comparable to a commercial formulation. Cationic amphiphiles based on malonic acid amides have great potential for liposome development for transfection.