Simple Loop Research Articles

Singularity-free theory and adaptive finite element computations of arbitrarily-shaped dislocation loop dynamics in 3D heterogeneous material structures

The long-standing problem of arbitrarily-shaped discrete dislocation loops in three-dimensional heterogeneous material structures is addressed by introducing novel singularity-free elastic field solutions as well as developing adaptive finite element computations for dislocation dynamics simulations. The first framework uses the Stroh formalism in combination with the biperiodic Fourier-transform and dual variable and position techniques to determine the finite-valued Peach–Koehler force acting on curved dislocation loops. On the other hand, the second versatile mixed-element method proposes to capture the driving forces through dissipative energy considerations with domain integrals by means of the virtual extension principle of the surfacial discontinuities. Excellent agreement between theoretical and numerical analyses is illustrated from simple circular shear dislocation loops to prismatic dislocations with complicated simply-connected contours in linear homogeneous isotropic solids and anisotropic elastic multimaterials, which also serves as improved benchmarks for dealing with more realistic boundary-value problems with evolving dislocations. Examples of sophisticated dislocation applications include the short-range core reaction between intersecting dislocation loops in interaction with a spherical cavity, as well as the Orowan dislocation-precipitate bypass mechanism in a compressed micropillar of polycrystalline copper. The latter multiscale investigation spans three orders of magnitude in size scale, and is thus enabled by computationally efficient and robust adaptive mesh generation procedures for explicit dislocation propagation, interaction, and coalescence in three-dimensional materials and material structures.

The charm-quark contribution to light-by-light scattering in the muon (g-2) from lattice QCD

We compute the hadronic light-by-light scattering contribution to the muon g-2 from the charm quark using lattice QCD. The calculation is performed on ensembles generated with dynamical (u, d, s) quarks at the SU(3)_mathrm{f} symmetric point with degenerate pion and kaon masses of around 415 MeV. It includes the connected charm contribution, as well as the leading disconnected Wick contraction, involving the correlation between a charm and a light-quark loop. Cutoff effects turn out to be sizeable, which leads us to use lighter-than-physical charm masses, to employ a broad range of lattice spacings reaching down to 0.039 fm and to perform a combined charm-mass and continuum extrapolation. We use the eta _c meson to define the physical charm-mass point and obtain a final value of a_mu ^mathrm{HLbL,c}= (2.8pm 0.5) times 10^{-11}, whose uncertainty is dominated by the systematics of the extrapolation. Our result is consistent with the estimate based on a simple charm-quark loop, whilst being free of any perturbative scheme dependence on the charm mass. The mixed charm–light disconnected contraction contributes a small negative amount to the final value.

Comparison of the mechanical properties and mechanical damages to tendon tissue in three suspensory fixation techniques

BackgroundAnterior cruciate ligament (ACL) injury is the most common traumatic injury to the knee joint. Suspensory fixation has become popular in ACL reconstruction because of its high primary stability, less invasiveness, and surgical convenience. There are two common types of suspensory fixation devices: those with fixed-length and those with adjustable-length loops. Owing to structural differences and differences in initial tensioning techniques, it is expected that mechanical property and damage to the tendons will vary from device to device; however, no literature has examined this so far. The main purpose of this study was to evaluate the damage caused to the tendon by three different suspensory fixation devices. An effective mechanical test was carried out as a prerequisite. MethodsFirst, the mechanical properties of simple loop device (SLD) as fixed-length loop device, first-generation, and second-generation adjustable devices (AD1 and AD2) as adjustable-length loop devices were tested (isolated device testing). Second, each device was tested using bovine extensor tendons (specimen testing). Cyclic testing included 2000 cycles; the devices were subsequently displaced until failure, and the ultimate tensile strength was determined using isolated device testing. Six samples of 3 devices were used in each testing experiment. After specimen testing, the surface structure of the tendon was evaluated quantitatively using optical coherence tomography (OCT) and our original histological scoring system. ResultsDuring isolated device testing, SLD demonstrated the least cyclic displacement, followed by AD1 and AD2. The highest ultimate tensile strength was observed in AD2, followed by SLD and AD1. In specimen testing, the least cyclic displacement was observed in SLD, followed by AD1 and AD2. Histologically, AD1 demonstrated a significantly lower score, with damaged surface morphology, than SLD and AD2. OCT values were significantly higher, with a more disturbing tendon surface structure, in AD1 than in SLD and AD2. ConclusionsThe first-generation adjustable loop device exhibited greatest graft tissue damage at the suspensory site in a clinically relevant setting. The thinner adjustable loop mechanism may have elevated graft damage by frictional stresses during loop adjustment or by repetitive tensioning stresses.

A geometrically inspired quantification approach for valve stiction using Riemannian logarithmic map

Valve stiction is one of the most important failure modes of valve, which may make the control loops suffered from severe performance degradation. Therefore, valve failure detection and diagnosis have been received widely attention from researchers and industrial personals in last two decades. Up to now, flourish results on valve stiction detection and diagnosis were reported. However, to our best knowledge, how to quantify more features of the valve stiction is still remained open. Most of the reported methods on the valve stiction quantification may not be suitable to deal with slipjump of the stiction, as well as the case where the valve with stiction is used in the cascade control loops. Noticing the fact that the relationship between sampled data behaves specific shape like limit cycle with the presence of stiction, a brand new general quantification method for valve stiction based on Riemannian logarithmic map is put forward in this paper. The proposed method from the perspective of geometry expounds how to deal with the features deadband plus stickband (S-zone) and slipjump (J-zone) for single control loop, and even simple cascade loop. The experiments well demonstrated that the proposed method is feasible to accurately quantify the valve stiction using the new indicator for the deadband plus stickband, and slipjump of valve stiction.

Homotopy Motions of Surfaces in 3-Manifolds

Abstract We introduce the concept of a homotopy motion of a subset in a manifold and give a systematic study of homotopy motions of surfaces in closed orientable 3-manifolds. This notion arises from various natural problems in 3-manifold theory such as domination of manifold pairs, homotopical behavior of simple loops on a Heegaard surface and monodromies of virtual branched covering surface bundles associated with a Heegaard splitting.

Design of Neural Network Model for Cross-Media Audio and Video Score Recognition Based on Convolutional Neural Network Model.

In this paper, the residual convolutional neural network is used to extract the note features in the music score image to solve the problem of model degradation; then, multiscale feature fusion is used to fuse the feature information of different levels in the same feature map to enhance the feature representation ability of the model. A network composed of a bidirectional simple loop unit and a chained time series classification function is used to identify notes, parallelizing a large number of calculations, thereby speeding up the convergence speed of training, which also makes the data in the dataset no longer need to be strict with labels. Alignment also reduces the requirements on the dataset. Aiming at the problem that the existing cross-modal retrieval methods based on common subspace are insufficient for mining local consistency within modalities, a cross-modal retrieval method fused with graph convolution is proposed. The K-nearest neighbor algorithm is used to construct modal graphs for samples of different modalities, and the original features of samples from different modalities are encoded through a symmetric graph convolutional coding network and a symmetric multilayer fully connected coding network, and the encoded features are fused and input. We jointly optimize the intramodal semantic constraints and intermodal modality-invariant constraints in the common subspace to learn highly locally consistent and semantically consistent common representations for samples from different modalities. The error value of the experimental results is used to illustrate the effect of parameters such as the number of iterations and the number of neurons on the network. In order to more accurately illustrate that the generated music sequence is very similar to the original music sequence, the generated music sequence is also framed, and finally the music sequence spectrogram and spectrogram are generated. The accuracy of the experiment is illustrated by comparing the spectrogram and the spectrogram, and genre classification predictions are also performed on the generated music to show that the network can generate music of different genres.

Principles of Endocrine Regulation: Reconciling Tensions Between Robustness in Performance and Adaptation to Change.

Endocrine regulation in the hypothalamic-pituitary-thyroid (HPT) axis is orchestrated by physiological circuits which integrate multiple internal and external influences. Essentially, it provides either of the two responses to overt biological challenges: to defend the homeostatic range of a target hormone or adapt it to changing environmental conditions. Under certain conditions, such flexibility may exceed the capability of a simple feedback control loop, rather requiring more intricate networks of communication between the system’s components. A new minimal mathematical model, in the form of a parametrized nonlinear dynamical system, is here formulated as a proof-of-concept to elucidate the principles of the HPT axis regulation. In particular, it allows uncovering mechanisms for the homeostasis of the key biologically active hormone free triiodothyronine (FT3). One mechanism supports the preservation of FT3 homeostasis, whilst the other is responsible for the adaptation of the homeostatic state to a new level. Together these allow optimum resilience in stressful situations. Preservation of FT3 homeostasis, despite changes in FT4 and TSH levels, is found to be an achievable system goal by joining elements of top-down and bottom-up regulation in a cascade of targeted feedforward and feedback loops. Simultaneously, the model accounts for the combination of properties regarded as essential to endocrine regulation, namely sensitivity, the anticipation of an adverse event, robustness, and adaptation. The model therefore offers fundamental theoretical insights into the effective system control of the HPT axis.

Characterization of the complete mitochondrial genome of Loxocephala perpunctata (Hemiptera: Eurybrachidae)

In this study, we sequenced and annotated the complete mitochondrial genome of Loxocephala perpunctata (Jacobi, 1944) (Hemiptera: Eurybrachidae). The mitogenome of L. perpunctata is 15,017 bp long and includes 37 genes and a large control region. Consisting of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and a D-loop. All protein-coding genes have the usual ATN start codons, except for ND5, which uses the noncanonical codon GTG. 22 tRNAs, the length ranging from 59 to 69 bp, having the clover-leaf structure except for the dihydrouridine (DHU) arm of trnS2 forming a simple loop.

Esoteric Pull and Esoteric Push: Two Simple In-Place Streaming Schemes for the Lattice Boltzmann Method on GPUs

I present two novel thread-safe in-place streaming schemes for the lattice Boltzmann method (LBM) on graphics processing units (GPUs), termed Esoteric Pull and Esoteric Push, that result in the LBM only requiring one copy of the density distribution functions (DDFs) instead of two, greatly reducing memory demand. These build upon the idea of the existing Esoteric Twist scheme, to stream half of the DDFs at the end of one stream-collide kernel and the remaining half at the beginning of the next, and offer the same beneficial properties over the AA-Pattern scheme—reduced memory bandwidth due to implicit bounce-back boundaries and the possibility of swapping pointers between even and odd time steps. However, the streaming directions are chosen in a way that allows the algorithm to be implemented in about one tenth the amount of code, as two simple loops, and is compatible with all velocity sets and suitable for automatic code-generation. The performance of the new streaming schemes is slightly increased over Esoteric Twist due to better memory coalescence. Benchmarks across a large variety of GPUs and CPUs show that for most dedicated GPUs, performance differs only insignificantly from the One-Step Pull scheme; however, for integrated GPUs and CPUs, performance is significantly improved. The two proposed algorithms greatly facilitate modifying existing code to in-place streaming, even with extensions already in place, such as demonstrated here for the Free Surface LBM implementation FluidX3D. Their simplicity, together with their ideal performance characteristics, may enable more widespread adoption of in-place streaming across LBM GPU codes.

Not Just Another Assessment Method: Reimagining Environmental Flows Assessments in the Face of Uncertainty

The numerous environmental flows assessment methods that exist typically assume a stationary climate. Adaptive management is commonly put forward as the preferred approach for managing uncertainty and change in environmental flows. However, we contend that a simple adaptive management loop falls short of meeting the challenges posed by climate change. Rather, a fundamental rethink is required to ensure both the structure of environmental flows assessments, along with each individual technical element, actively acknowledges the multiple dimensions of change, variability and complexity in socio-ecological systems. This paper outlines how environmental flow assessments can explicitly address the uncertainty and change inherent in adaptively managing multiple values for management of environmental flows. While non-stationarity and uncertainty are well recognised in the climate literature, these have not been addressed within the structure of environmental flows methodologies. Here, we present an environmental flow assessment that is structured to explicitly consider future change and uncertainty in climate and socio-ecological values, by examining scenarios using ecological models. The environmental flow assessment methodology further supports adaptive management through the intentional integration of participatory approaches and the inclusion of diverse stakeholders. We present a case study to demonstrate the feasibility of this approach, highlighting how this methodology facilitates adaptive management. Rethinking our approach to environmental flows assessments is an important step in ensuring that environmental flows continue to work effectively as a management tool under climate change.

Diagnostic utility and validation of a newly developed real time loop mediated isothermal amplification method for the detection of SARS CoV-2 infection

BackgroundDetecting SARS-CoV-2 using a simple real time molecular assay will be helpful for the mitigation efforts in low / middle income countries during the pandemic. We have developed and validated a rapid and simple real time loop mediated isothermal amplification assay (LAMP) for screening of SARS-CoV-2 infection in known infected and non-infected individuals. MethodsSix sets of primers were designed targeting the N-gene of the SARS-CoV-2 (Accession ID MN994468). LAMP reactions were performed using Warm Start 2X Master Mix and real-time PCR machine at 65 °C for 60 cycles with 15 s for each cycle. Results were read by visualizing turbidity under ultraviolet light and real time fluorescence detection through FAM channel of the real time PCR machine. We tested a total of 320 including 240 SARS CoV-2 positive (Ct values <40) and 80 SARS CoV-2 negative samples as tested by a real time RT-PCR using the newly developed LAMP assay. ResultsA total of 206 out of 240 SARS CoV-2 positive samples were tested positive by the newly developed LAMP assay with a sensitivity of 86%. All 80 SARS CoV-2 negative samples were tested negative by the newly developed LAMP assay with a specificity of 100%. ConclusionThe newly developed real time LAMP assay has a sensitivity of 86% and specificity of 100% compared to the real time RT-PCR for the detection of SARS CoV-2. The new assay will be useful to screen large number of samples if adopted to minimize the time and cost.

HYBRID MECHANICAL CIRCULATORY LOOPS – AN EMERGING NEED FOR TOTAL ARTIFICIAL HEARTS WITH NOVEL TECHNOLOGIES.

Circulatory assist devices need to be tested at various levels prior to human implantation. These include numerical simulations, lab and animal testing, tissue computability prior to human trials that would scale in terms of complexity of indications and participant load. Mock circulatory loops though not ideal offer the best current equivalents of gold standard for such purposes in the in vitro domain. These could be very simple hydraulic loops to complex hydraulic loop interface with computers. These need to replicate both right and left circulatory systems coupled with vascular compliances and resistances. It should recreate the perfusion rates and pressures that exist in normal systemic and pulmonary vasculature for both normal and heart failure models. These rigs greatly reduce the device evaluation costs by mimicking nature though vasomotor responses in the normal human body may require complicated evaluation models to be deciphered in future by use of evolving technologies. Following mechanical evaluation on the mock circulatory loop actual animal testing would give the experimental proof of concept. The basic requirements are that of a pump, ow channels, compliance chambers with monitoring of pressure and resistance changes using pressure and ow sensors. It serves as a safe low cost training and evaluating platform. Virtual mock loop simulation tool can simulate the hemodynamics using a lumped-parameter model for systemic/pulmonary circulation characteristic inputs values for impedance, systolic and diastolic ventricular compliance, beat rate, and blood volume and characteristics of the cardiac chambers and valves. VML contains several different lumped parameter models for selection and evaluation. It also stores and organizes data from different origins that makes comparison easier. For new total articial heart models the advantage of a dual approach emerges with use of hybrid mechanical circulatory loop.

Simple conformal loop ensembles on Liouville quantum gravity

We show that, when one draws a simple conformal loop ensemble (CLEκ for κ∈(8/3,4)) on an independent κ-Liouville quantum gravity (LQG) surface and explores the CLE in a natural Markovian way, the quantum surfaces (e.g., corresponding to the interior of the CLE loops) that are cut out form a Poisson point process of quantum disks. This construction allows us to make direct links between CLE on LQG, (4/κ)-stable processes, and labeled branching trees. The ratio between positive and negative jump intensities of these processes turns out to be −cos(4π/κ) which can be interpreted as a “density” of CLE loops in the CLE on LQG setting. Positive jumps correspond to the discovery of a CLE loop (where the LQG length of the loop is given by the jump size) and negative jumps correspond to the moments where the discovery process splits the remaining to be discovered domain into two pieces. Some consequences of this result are the following: (i) It provides a construction of a CLE on LQG as a patchwork/welding of quantum disks. (ii) It allows us to construct the “natural quantum measure” that lives in a CLE carpet. (iii) It enables us to derive some new properties and formulas for SLE processes and CLE themselves (without LQG) such as the exact distribution of the trunk of the general SLEκ(κ−6) processes. The present work deals directly with structures in the continuum and makes no reference to discrete models, but our calculations match those for scaling limits of O(N) models on planar maps with large faces and CLE on LQG. Indeed, our Lévy-tree descriptions are exactly the ones that appear in the study of the large-scale limit of peeling of discrete decorated planar maps, such as in recent work of Bertoin, Budd, Curien and Kortchemski. The case of nonsimple CLEs on LQG is studied in another paper.

Outcomes at 3 Months of a Place and Active Hold Method of Flexor Tendon Rehabilitation Following Zone II Injury.

Background: Previous studies have shown that outcomes following a place and active hold (PAH) are better than a passive flexion protocol after a two-strand core-suture repair of flexor tendons injuries in zone II. This study aims to determine the outcomes of a PAH protocol of flexor tendon rehabilitation following a four-strand core-suture plus an epitendinous suture repair of the flexor digitorum profundus (FDP) combined with a simple horizontal loop repair of the flexor digitorum superficialis (FDS). Methods: This is a prospective study of patients with complete injury to both flexor tendons in zone II. All tendons were repaired with a simple horizontal loop for FDS and four-strand core-suture plus epitendinous suture for FDP. The PAH protocol was used postoperatively for 6 weeks. The outcome was evaluated using flexion contracture and total active motion (TAM), interpreted using Strickland criteria and categorised as excellent, good, fair and poor at 6 weeks and 3 months. The linear regression model was used to determine predictors of outcomes. Results: The study included 32 patients with flexor tendon injury in 46 fingers. No repairs ruptured, and 24 (52%) digits achieved good or excellent motion 6 weeks after surgery using the Strickland criteria. According to the Strickland criteria, 41 (89%) digits ranked as excellent and good with no poor result at a 3-month follow-up. Four patients had 5-10° of flexion contracture. Age was the predictor of TAM at 6 weeks and accounted for 13% of its variation. Improvement of TAM from 6 weeks to 3 months was related to age and flexion contracture at 6 weeks. Conclusions: The PAH protocol can be considered a safe technique for flexor rehabilitation after four-strand core-suture repair of FDP in zone II. Level of Evidence: Level IV (Therapeutic).

Systematic Approach for Finite Element Analysis of Thermoplastic Impregnated 3D Filament Winding Structures—Advancements and Validation

This work aims to enhance and validate a systematic approach for the structural finite element (FE) analysis of thermoplastic impregnated 3D filament winding structures (fiber skeletons). The idealized modeling of geometrically complex fiber skeletons used in previous publications is refined by considering additional characteristic dimensions and investigating their mechanical influence. Moreover, the modeling approach is transferred from the meso- to the macro-level in order to reduce modeling and computational effort. The properties of meso- and macro-level FE models are compared using the example of simple loop specimens. Based on the results, respective application fields are defined. In the next step, the same modeling approach is applied to a more complex, three-dimensional specimen—the inclined loop. For its macro-level FE model, additional material characterization and modeling, as well as enhancements in the modeling of the geometry, are proposed. Together with previously determined effective composite properties of fiber skeletons, these results are validated in experimental tensile tests on inclined loop specimens.

A note on Loewner energy, conformal restriction and Werner’s measure on self-avoiding loops

We establish an expression of the Loewner energy of a Jordan curve in terms of Werner’s measure on simple loops of SLE 8/3 type. The proof is based on a formula for the change of the Loewner energy under a conformal map that is reminiscent of SLE processes’ conformal restriction property.

An industrial control loop decoupler for process control applications

The paper describes a simple and efficient control loop decoupler for TITO (two inputs, two outputs) control systems. The inverted decoupling approach is used, and the feedforward filters are just static gains. The feedforward gains are determined in two ways, from a static analysis and from optimization. By investigating several cases found in literature, it is found that the two sets of feedforward gains are very close. The control loop decoupler is implemented in an industrial DCS system and simulation experiments as well as laboratory tests show that a significant reduction of the coupling is accomplished. Automatic tuning of the feedforward gains is derived and implemented in the system as well.

Benefits of Fuzzy Logic on MPPT and PI Controllers in the Chain of Photovoltaic Control Systems

This paper presents a comparative study between two maximum power point tracking (MPPT) algorithms, the incremental conductance algorithm (InC) and the fuzzy logic controller (FLC). The two algorithms were applied to a low photovoltaic power conversion system, and they both use different PI controllers and grid synchronization techniques. Moreover, both InC and FLC methods have Clarke and Park Transformation. To some extent, the incremental conductance and fuzzy logic controller approaches are similar, but their control loops are different. Therefore, the InC has classic Proportional Integrative (PI) controllers with simple phase-locked loops (PLL). At the same time, the FLC works with fuzzy logic PI controllers linked with the Second Order Generalized Integrator (SOGI). The proposed techniques examine the solar energy conversion performance of the photovoltaic (PV) system under possible irradiance changes and constant temperature conditions. Finally, a performance comparison has been made between InC and FLC, which demonstrates the effectiveness of the fuzzy controller over the incremental conductance algorithm. FLC turns to convert photovoltaic power easily, decreasing fluctuations, and it offers a quick response to the variation of solar irradiance (shading effect). The simulation results show a superior performance of the controller with fuzzy logic, which helps the inverter convert over 99% of the power generated by the photovoltaic panels. In comparison, the incremental conductance algorithm converts around 80%.

Avoiding obstacles while intercepting a moving target: a miniature fly's solution.

ABSTRACTThe miniature robber fly Holcocephala fusca intercepts its targets with behaviour that is approximated by the proportional navigation guidance law. During predatory trials, we challenged the interception of H. fusca performance by placing a large object in its potential flight path. In response, H. fusca deviated from the path predicted by pure proportional navigation, but in many cases still eventually contacted the target. We show that such flight deviations can be explained as the output of two competing navigational systems: pure-proportional navigation and a simple obstacle avoidance algorithm. Obstacle avoidance by H. fusca is here described by a simple feedback loop that uses the visual expansion of the approaching obstacle to mediate the magnitude of the turning-away response. We name the integration of this steering law with proportional navigation ‘combined guidance’. The results demonstrate that predatory intent does not operate a monopoly on the fly's steering when attacking a target, and that simple guidance combinations can explain obstacle avoidance during interceptive tasks.

A Wideband Pattern-Reconfigurable Loop Antenna Designed by Using Characteristic Mode Analysis

In this letter, a pattern-reconfigurable antenna for indoor communication is proposed, which can provide stable conical and broadside beams. Although this type of pattern-reconfigurable antenna can provide large radiation coverage, it usually suffers complex structure, narrow bandwidth, and distorted pattern. In order to get rid of the complex radiators, a simple loop patch is introduced to generate the conical and broadside beams. Through slotting the loop patch with the aid of characteristic mode analysis, the two desired radiation modes can be well excited in the same band. Meanwhile, the modified loop patch can provide stable radiation patterns by suppressing unwanted higher order modes. For achieving the reconfigurable beams, a reconfigurable feeding network is designed to switch two working modes. Finally, the proposed pattern-reconfigurable antenna is fabricated, and the measured overlapped 10 dB operating bandwidth is about 27.3% ranging from 3.61 to 4.75 GHz. The results show that the proposed pattern-reconfigurable antenna has a wide bandwidth and stable radiation patterns, which exhibits attractive potentials for fifth-generation (5G) indoor communication in sub-6 GHz.