Divergent Length Research Articles

Friction Drilling of Cast Aluminum Alloy A380 Without Significant Petal Formation and Radial Fracture

Cast aluminum alloy A380 is one of the most commonly specified alloys that has light weight and exhibits excellent resistance to hot cracking, which makes it necessary in many industrial applications. An idea is investigated to generate a cylindrical bushing without significant petal formation and radial fracture that are expected to be obtained by friction drilling of cast metals. Three materials; namely, 316 stainless steel, Al6060 aluminum alloy, and red copper alloy are used in which each of them is located on the upper and lower surfaces of A380 workpiece, so achieving the idea of the functionally graded material. The process parameters were studied for reducing the resultant axial force, the gap between surfaces, and achieving a longer bushing without petal formation and radial fracture. Lower feed rate achieves minimum axial force and gap thickness with maximum bushing length for all material sandwiches. An optimized decision making by the help of fuzzy logic techniques is performed, revealing that red copper sandwich exhibits the optimal multiple performance characteristic index based on axial force, bushing length, gap thickness, and gap divergence.

CFD analysis of the flashing flow characteristics of subcritical refrigerant R134a through converging-diverging nozzles

A CFD-based numerical analysis of the choking flashing flow characteristics in R134a converging-diverging nozzles is presented in this paper. The CFD results are validated with available experimental data of R134a converging-diverging nozzles. After that, the critical mass flux and effects of geometric dimensions on the performance of converging-diverging nozzles are investigated. Furthermore, the calculated critical mass fluxes are compared to that of the classical models. Results show that the metastable state in R134a converging-diverging nozzle is weaker than that of water at the same operating parameters and a higher choking correction factor of R134a compared to that of water is obtained. The optimum ratio of nozzle exit diameter to the throat diameter of 2.4 is recommended among the studied nozzle geometry dimensions. Effect of the divergent length on the nozzle flow characteristics is relatively smaller than that of the nozzle exit diameter.

Many-Body Delocalization as a Quantum Avalanche.

We propose a multiscale diagonalization scheme to study disordered one-dimensional chains, in particular, the transition between many-body localization (MBL) and the ergodic phase, expected to be governed by resonant spots. Our scheme focuses on the dichotomy of MBL versus validity of the eigenstate thermalization hypothesis. We show that a few natural assumptions imply that the system is localized with probability one at criticality. On the ergodic side, delocalization is induced by a quantum avalanche seeded by large ergodic spots, whose size diverges at the transition. On the MBL side, the typical localization length tends to the inverse of the maximal entropy density at the transition, but there is a divergent length scale related to the response to an inclusion of large ergodic spots. A mean-field approximation analytically illustrates these results and predicts a power-law distribution for thermal inclusions at criticality.

Optimum Design of Nozzle Geometry of Dry Ice Blasting Using CFD for the Reduction of Noise Emission

Dry ice blasting has been used in the modern cleaning industry. However, the primary disadvantage of dry ice blasting is high noise exposure. At a high blasting pressure, the process reaches a harmful noise level of up to 130 dBA. The situation significantly impairs to a human being when the noise emission occurs in an inaudible frequency area. Present safety measures are only based on administrative control by encapsulating the entire system with sound insulation. The main objective of this project is to study the optimum nozzle configuration on the effect of dry ice blasting particle velocity and acoustic noise emission. Different nozzle geometry were simulated several times until optimization is achievable. Three-dimension models are designed using CATIA V5. Then the models are simulated with Ansys Fluent V18.2. The numerical studies have been carried out using density based, standard k- e turbulence and Acoustic Broadband Noise Sources model. Six (6) different nozzle configuration namely divergent length, the angle of particle inlet, convergent diameter, expansion ratio, gas inlet diameter and length ratio are analyzed in term of particle velocity magnitude and acoustic power level. The result shows that the optimum nozzle configuration for divergent length, the angle of particle inlet, convergent diameter, expansion ratio, gas inlet diameter and length ratio are 230 mm, 30 mm, 35 mm, 1.00, 6 mm and 0.80 respectively. This configuration provides minimum lowest acoustic noise emission and maximum particle velocity magnitude.

Effect of Convergent Section Contour on the Sonic Line in Rocket Engine Nozzles

This study made a numeric evaluation of the effect of convergent geometry on the position and profile of the sonic line in rocket engine nozzles. To validate the numerical solution, two conical nozzles, from which experimental results are available in the literature, were used as reference. The tested convergent geometries have the same values for throat radius (Rt), radius of curvature at the throat of the divergent section (Rc3), divergent length, and ratio of areas. The numerical solutions have shown that convergent geometry changes the shape of the sonic line, and nozzles with lower radius ratios (Rc2/Rt) are more sensitive to the shape of the convergent section.

Recurrence Quantification Analysis at work: Quasi-periodicity based interpretation of gait force profiles for patients with Parkinson disease

In this letter, making use of real gait force profiles of healthy and patient groups with Parkinson disease which have different disease severity in terms of Hoehn-Yahr stage, we calculate various heuristic complexity measures of the recurrence quantification analysis (RQA). Using this technique, we are able to evince that entropy, determinism and average diagonal line length (divergence) measures decrease (increases) with increasing disease severity. We also explain these tendencies using a theoretical model (based on the sine-circle map), so that we clearly relate them to decreasing degree of irrationality of the system as a course of gait’s nature. This enables us to interpret the dynamics of normal/pathological gait and is expected to increase further applications of this technique on gait timings, gait force profiles and combinations of them with various physiological signals.

Entanglement scaling at first order quantum phase transitions

First order quantum phase transitions (1QPTs) are signalled, in the thermodynamic limit, by discontinuous changes in the ground state properties. These discontinuities affect expectation values of observables, including spatial correlations. When a 1QPT is crossed in the vicinity of a second order one, due to the correlation length divergence of the latter, the corresponding ground state is modified and it becomes increasingly difficult to determine the order of the transition when the size of the system is finite. Here we show that, in such situations, it is possible to apply finite size scaling (FSS) to entanglement measures, as it has recently been done for the order parameters and the energy gap, in order to recover the correct thermodynamic limit (Campostrini et al 2014 Phys. Rev. Lett. 113 070402). Such a FSS can unambiguously discriminate between first and second order phase transitions in the vicinity of multicritical points even when the singularities displayed by entanglement measures lead to controversial results.

Fermion-induced quantum criticality with two length scales in Dirac systems

The quantum phase transition to a $\mathbb{Z}_3$-ordered Kekul\'e valence bond solid in two-dimensional Dirac semimetals is governed by a fermion-induced quantum critical point, which renders the putatively discontinuous transition continuous. We study the resulting universal critical behavior in terms of a functional RG approach, which gives access to the scaling behavior on the symmetry-broken side of the phase transition, for general dimension and number of Dirac fermions. In particular, we investigate the emergence of the fermion-induced quantum critical point for space-time dimensions $2<d<4$. We determine the integrated RG flow from the Dirac semi-metal to the symmetry-broken regime and analyze the underlying fixed point structure. We show that the fermion-induced criticality leads to a scaling form with two divergent length scales, due to the breaking of the discrete $\mathbb{Z}_3$ symmetry. This provides another source of scaling corrections, besides the one stemming from being in the proximity to the first order transition.

Theoretical investigation of phase-mismatched second-harmonic conversion efficiency in BBO crystal

We report a modified general relation of nanosecond second harmonic conversion efficiency relation to determine efficiency at any value of power density, laser wavelength, crystal length and beam divergence when transmission value are relative high >90%, which make it a reference for practical study comparison. We apply this study on BBO crystal and study the efficiency as function of both crystal length (0–0.7 cm) and laser wavelength (460–1400 nm), (527–1400 nm) in 3-D plot for phase matching types I and II respectively. Finally, we study the effect of crystal length and power density at generated deep-ultraviolet cut-off type I wavelength 205 nm.

Experimental and Computational Exploration of Underexpanded Jets from Conical, Bell and Double Parabolic Nozzles

The flow structure of the jet emanating from supersonic nozzle with different profiles at underexpanded condition were investigated systematically. Experiments were carried out on conical, bell and double parabolic nozzle at Nozzle Pressure Ratios (NPR) of 4.5, 5 and 5.5. For the sake of comparison, the divergent length was the same for all the nozzles. Numerical simulations were also conducted in a two dimensional computational domain taking a density-based solver with RANS equations and SST k-ω turbulence model. The experimental and numerical results matched well all NPRs. The shock cell length, potential core length and supersonic core length at different NPRs were determined from experiments and compared to numerical predictions. These values are also compared to the predicted values based on the equations previously developed by researchers. It is observed that there is not much influence in nozzle profiles in the shock cell length, potential core length and supersonic core length.

Design of a double parabolic supersonic nozzle and performance evaluation by experimental and numerical methods

Purpose The purpose of this paper is to design a double parabolic nozzle and to compare the performance with conventional nozzle designs. Design/methodology/approach The throat diameter and divergent length for Conical, Bell and Double Parabolic nozzles were kept same for the sake of comparison. The double parabolic nozzle has been designed in such a way that the maximum slope of the divergent curve is taken as one-third of the Prandtl Meyer (PM) angle. The studies were carried out at Nozzle Pressure Ratio (NPR) of 5 and also at design conditions (NPR = 3.7). Experimental measurements were carried out for all the three nozzle configurations and the performance parameters compared. Numerical simulations were also carried out in a two-dimensional computational domain incorporating density-based solver with RANS equations and SST k-ω turbulence model. Findings The numerical predictions were found to be in reasonable agreement with the measured experimental values. An enhancement in thrust was observed for double parabolic nozzle when compared with that of conical and bell nozzles. Research limitations/implications Even though the present numerical simulations were capable of predicting shock cell parameters reasonably well, shock oscillations were not captured. Practical implications The double parabolic nozzle design has enormous practical importance as a small increase in thrust can result in a significant gain in pay load. Social implications The thrust developed by the double parabolic nozzle is seen to be on the higher side than that of conventional nozzles with better fuel economy. Originality/value The overall performance of the double parabolic nozzle is better than conical and bell nozzles for the same throat diameter and length.

Fiber networks below the isostatic point: Fracture without stress concentration

Crack nucleation is a ubiquitous phenomena during materials failure, because stress focuses on crack tips. It is known that exceptions to this general rule arise in the limit of strong disorder or vanishing mechanical stability, where stress distributes over a divergent length scale and the material displays diffusive damage. Here we show, using simulations, that a class of diluted lattices displays a new critical phase when they are below isostaticity, where stress never concentrates, damage always occurs over a divergent length scale, and catastrophic failure is avoided.

Study of intake manifold for Universiti Malaysia Perlis automotive racing team formula student race car

This paper describes the design differences between the intake manifold and restrictor used in racing cars that participate in the Formula Student (FSAE) competition. To fulfil the criteria of rules and regulation of the race, each race car must have a restriction device that has a maximum diameter of 20 mm installed between the throttle body and intake manifold. To overcome these problems, a restrictor has been designed and analysed using the steady state analysis, to reduce the loss of pressure in the restrictor. Design of the restrictor has a fixed parameter of the maximum diameter of 20mm. There are some differences that have been taken to make the comparison between the design of the restrictor, the diameter of the inlet and outlet, the curvature of the surface, convergence and divergence angle and length of the restrictor. Intake manifold was designed based on the design of the chassis, which shall not exceed the envelope defined by the FSAE competition. A good intake manifold design will affect the performance of the engine. Each design have made an analysis designed to ensure that each cylinder engine gets its air evenly. To verify the design, steady state analysis was made for a total mass flow rate and the velocity of air leaving a runner in each engine. Data such as the engine MAP reading was recorded by using Haltech ECU Management Software as reference purposes.

Differential sperm storage by female zebra finches Taeniopygia guttata.

When females mate promiscuously, female sperm storage provides scope to bias the fertilization success towards particular males via the non-random acceptance and utilization of sperm. The difficulties observing post-copulatory processes within the female reproductive tract mean that the mechanisms underlying cryptic female choice remain poorly understood. Here, we use zebra finches Taeniopygia guttata, selected for divergent sperm lengths, combined with a novel technique for isolating and extracting sperm from avian sperm storage tubules (SSTs), to test the hypothesis that sperm from separate ejaculates are stored differentially by female birds. We show that sperm from different inseminations enter different SSTs in the female reproductive tract, resulting in almost complete segregation of the sperm of competing males. We propose that non-random acceptance of sperm into SSTs, reflected in this case by sperm phenotype, provides a mechanism by which long sperm enjoy enhanced fertilization success in zebra finches.

Detecting exact breakpoints of deletions with diversity in hepatitis B viral genomic DNA from next-generation sequencing data.

Many studies have suggested that deletions of Hepatitis B Viral (HBV) are associated with the development of progressive liver diseases, even ultimately resulting in hepatocellular carcinoma (HCC). Among the methods for detecting deletions from next-generation sequencing (NGS) data, few methods considered the characteristics of virus, such as high evolution rates and high divergence among the different HBV genomes. Sequencing high divergence HBV genome sequences using the NGS technology outputs millions of reads. Thus, detecting exact breakpoints of deletions from these big and complex data incurs very high computational cost. We proposed a novel analytical method named VirDelect (Virus Deletion Detect), which uses split read alignment base to detect exact breakpoint and diversity variable to consider high divergence in single-end reads data, such that the computational cost can be reduced without losing accuracy. We use four simulated reads datasets and two real pair-end reads datasets of HBV genome sequence to verify VirDelect accuracy by score functions. The experimental results show that VirDelect outperforms the state-of-the-art method Pindel in terms of accuracy score for all simulated datasets and VirDelect had only two base errors even in real datasets. VirDelect is also shown to deliver high accuracy in analyzing the single-end read data as well as pair-end data. VirDelect can serve as an effective and efficient bioinformatics tool for physiologists with high accuracy and efficient performance and applicable to further analysis with characteristics similar to HBV on genome length and high divergence. The software program of VirDelect can be downloaded at https://sourceforge.net/projects/virdelect/.

Drag reduction of supersonic blunt bodies using opposing jet and nozzle geometric variations

Passive and active flow control methods are used to manipulate flow fields to reduce acoustic signature, aerodynamic drag and heating experienced by blunt bodies flying at supersonic and hypersonic speeds. This paper investigate the use of active opposing jet concept in combination with geometric variations of the opposing jet nozzle to alleviate high wave drag formation. A numerical study is conducted to observe the effects of simple jet as well as jet emanating from a divergent nozzle located at the nose of a blunt hemispherical body. An initial discussion is presented of the complex shock wave pattern flow physics occurring when opposing jet ejected from a nozzle under various operating conditions interacts with the free stream flow. The complex flow physics that include long penetration and short penetration mode is studied in conjunction with effect on drag. The numerical setup consists of supersonic free stream flow interacting with an opposing sonic jet under varying pressure ratios. Initial computational results are validated by identifying prominent flow features as well as comparing available experimental data of surface pressure distributions. Preliminary validation is followed by the introduction of a divergent nozzle in the blunt body nose region. A series of numerical iterations are performed by varying nozzle geometric parameters that include nozzle divergent angle and nozzle length for a certain jet pressure ratio. Long penetration mode, short penetration mode as well as flow separations are captured accurately during the analysis. The results show a considerable reduction in drag by the use of a divergent nozzle. Specifically, 46% and 56% reduction in drag coefficient is achieved at pressure ratio of 0.6 and 0.8 respectively in the divergent nozzle cases as compared to the simple blunt body without any nozzle.

The Intracellular Domain of Pentameric Ligand-Gated Ion Channels and its Effect on Receptor Conductance in GLIC Chimeras

The pentameric ligand-gated ion channel (pLGIC) superfamily includes the nicotinic acetylcholine (nACh), 5-HT3, ɣ-aminobutyric acid type A (GABAA), and glycine receptor. These channels are made up of five homologous subunits surrounding a central ion channel pore and can be divided into three pentameric domains. The extracellular domain (ECD) and transmembrane domain (TMD) of the channels show high levels of homology and have been well studied and structures have been published. In contrast, the intracellular domain (ICD) shows sequence and length divergence in the different receptors. Mutations in the ICD have been shown to alter receptor conductance. Gloeobacter violaceus LGIC (GLIC) is a prokaryotic pLGIC without a native ICD, which can be expressed and studied in Xenopus oocytes. To elucidate the mechanisms by which the ICD affects the channel pathway and conductance we have created chimeras of GLIC ECD and TMD with ICDs of both anion- and cation-conducting pLGICs (GABAρ1, Glyα1, nAChRα7, 5-HT3A). Functional expression of chimeras was first confirmed by applying low pH (pH 5) pulses to oocytes under two-electrode voltage clamp. We have begun to study the single channel conductance and gating kinetics of chimeric channels and confirmed that the GLIC wildtype has a single-channel conductance of 10pS. For the GLIC-5-HT3A-ICD chimera, we expect to see a decrease in conductance as we observed an increase in a construct of 5-HT3A upon removing the ICD. Amino acid engineering in both the chimeras and eukaryotic parent channels will then be used to further understanding of how the ICDs contribute to ion conducting properties.

Many-body localization in Ising models with random long-range interactions

We theoretically investigate the many-body localization phase transition in a one-dimensional Ising spin chain with random long-range spin-spin interactions, $V_{ij}\propto\left|i-j\right|^{-\alpha}$, where the exponent of the interaction range $\alpha$ can be tuned from zero to infinitely large. By using exact diagonalization, we calculate the half-chain entanglement entropy and the energy spectral statistics and use them to characterize the phase transition towards the many-body localization phase at infinite temperature and at sufficiently large disorder strength. We perform finite-size scaling to extract the critical disorder strength and the critical exponent of the divergent localization length. With increasing $\alpha$, the critical exponent experiences a sharp increase at about $\alpha=1$ and then gradually decreases to a value found earlier in a disordered short-ranged interacting spin chain. For $\alpha<1$, we find that the system is mostly localized and the increase in the disorder strength may drive a transition between two many-body localized phases. In contrast, for $\alpha>1$, the transition is from a thermalized phase to the many-body localization phase. Our predictions could be experimentally tested with ion-trap quantum emulator with programmable random long-range interactions, or with randomly distributed Rydberg atoms or polar molecules in lattices.

Generalized Dyson model: Nature of the zero mode and its implication in dynamics

We study the role of the anomalous $E=0$ state in dynamical properties of non-interacting fermionic chains with chiral symmetry and correlated bond disorder in one dimension. These models posses a diverging density of states at zero energy leading to a divergent localization length at the band center. By analytically calculating the localization length for a finite system, we show that correlations in the disorder modify the spatial decay of the $E = 0$ state from being quasilocalized to extended. We numerically simulate charge and entanglement propagation and provide evidence that states close to $E=0$ dominate the dynamical properties. Remarkably, we find that correlations lead to subdiffusive charge propagation, whereas the growth of entanglement is logarithmically slow. A logarithmic scaling of entanglement saturation with system size is also observed, which indicates a behavior akin to quantum critical glasses.

Horizon as critical phenomenon

We show that renormalization group(RG) flow can be viewed as a gradual wave function collapse, where a quantum state associated with the action of field theory evolves toward a final state that describes an IR fixed point. The process of collapse is described by the radial evolution in the dual holographic theory. If the theory is in the same phase as the assumed IR fixed point, the initial state is smoothly projected to the final state. If in a different phase, the initial state undergoes a phase transition which in turn gives rise to a horizon in the bulk geometry. We demonstrate the connection between critical behavior and horizon in an example, by deriving the bulk metrics that emerge in various phases of the U(N) vector model in the large N limit based on the holographic dual constructed from quantum RG. The gapped phase exhibits a geometry that smoothly ends at a finite proper distance in the radial direction. The geometric distance in the radial direction measures a complexity : the depth of RG transformation that is needed to project the generally entangled UV state to a direct product state in the IR. For gapless states, entanglement persistently spreads out to larger length scales, and the initial state can not be projected to the direct product state. The obstruction to smooth projection at charge neutral point manifests itself as the long throat in the anti-de Sitter space. The Poincare horizon at infinity marks the critical point which exhibits a divergent length scale in the spread of entanglement. For the gapless states with non-zero chemical potential, the bulk space becomes the Lifshitz geometry with the dynamical critical exponent two. The identification of horizon as critical point may provide an explanation for the universality of horizon. We also discuss the structure of the bulk tensor network that emerges from the quantum RG.