Classical Tunneling Research Articles

Graft Reorientation and Lateral Extra-articular Tenodesis in Revision Surgery for Persistent Rotational Instability of a Verticalized Anterior Cruciate Ligament Graft

Persistent rotational instability after anterior cruciate ligament reconstruction is a relatively common postoperative complication, typically associated with graft verticalization due to improper femoral tunnel placement, especially with classic transtibial femoral tunnel techniques. This article describes a technique designed to reorient a verticalized anterior cruciate ligament graft at its femoral insertion to a more anatomic position in the coronal and sagittal planes, aiming to restore knee stability without the need for a complete revision operation. Additionally, a lateral extra-articular tenodesis with fascia lata is added to reinforce rotational stability.

A numerical method to mimic an experimental wind gust generator: The immersed boundary gust generator

To generate horizontal wind gusts in a classical wind tunnel, Wood, Breuer, and Neumann [A novel approach for artificially generating horizontal wind gusts based on a movable plate: The paddle,” J. Wind Eng. Ind. Aerodyn. 230, 105170 (2022)] developed a new wind gust generator denoted the “paddle.” The working principle relies on the partial blocking of the outlet of the wind tunnel nozzle by a plate that vertically moves into the free-stream. Based on laser-Doppler anemometer measurements of the velocity at only a few locations, the basic functionality of the device was proven. The objective of the present contribution is to numerically mimic the gust generator and the flow field induced by the paddle in the test section. Contrary to the single-point measurements, the three-dimensional time-resolved simulation delivers the entire flow field and thus allows to investigate all details of the generated gust. To describe the paddle motion, the immersed boundary method with a continuous and direct forcing approach is implemented into a finite-volume flow solver for large-eddy simulations. A uniform and a non-uniform distribution of the Lagrangian markers are investigated where the latter ensures that an excessive increase in the computational resources required can be avoided. The predictions allow to characterize the resulting flow features induced by the paddle in great detail. Furthermore, a comparison of the numerical and experimental results is carried out based on the time histories of the streamwise and vertical velocity components at certain positions showing a close agreement. Finally, the forces acting on the fluid by the moving paddle are evaluated.

Particle dynamics in dusty plasma: Classical tunneling

A Hamiltonian formalism for studying the dynamics of a dust particle with variable electric charge in dusty plasma is proposed. The Hamiltonian and the equations of motion are presented, and the dynamics is shown to be conservative. The problem is cast in terms of the motion of a particle with a constant fictitious charge QA moving in a suitably defined potential, while the actual particle charge is spatially distributed. With this formalism, the problem of trapping of dust particles in potential wells and barriers is studied. The results show that because of the spatial “delocalization”/distribution of the particle charge, a particle with insufficient energy to cross the potential barrier can penetrate it to tunnel out, i.e., “classical tunneling,” similar to a high jumper clearing the bar by the Fosbury flop technique or the usual quantum tunneling. For energies greater than a critical value, the charged particle is shown to tunnel out of even an infinitely deep potential well. A modified criterion for trapping in potential wells is given.

Students' alternative conceptions in quantum mechanics: The case of one-dimensional potential quantum tunneling

Quantum mechanics is generally an abstract theory that challenges intuition since it cannot be understood using ordinary experiences. Quantum tunneling is one of the topics which is more counterintuitive and challenges students' conceptual understanding. The study was aimed at investigating if final year undergraduate quantum mechanics students have alternative conceptions regarding quantum tunneling phenomena after a full course of instruction. In this study, students’ alternative conceptions are referred to as any student ideas related to the incorrect belief of scientific principles. Using the deep structured interviews involving 36 students who were registered in a quantum physics course from the University of Malawi, we found that some students hold on to the idea that the energy of a quantum tunneling electron is lost, the wave function graph depicts the physical wave, and the “potential step,” and “barrier” means a physical object/barrier. The study further established that the possible sources of these alternative conceptions emanated from students’ experience with classical tunneling / classical mechanics, quantum mechanics lecturer notes, and previous quantum mechanics lessons. The findings of this study further portray that traditional pedagogy has its limitation in facilitating students' comprehension of quantum tunneling. We recommend that further research into the design of instructional technology for quantum physics should consider these students' alternative conceptions when designing visual, interactive, and mental models, which may help establish students' conceptual understanding of quantum mechanics.

Hand Allodynia, Lack of Finger Flexion, and the Need for Carpal Tunnel Release

The clinical features of classic carpal tunnel syndrome are well known. However, some patients who may respond equally well to carpal tunnel release (CTR) display atypical signs and symptoms. The chief differential features are allodynia (painful dysesthesias), lack of finger flexion, and, on examination, pain on passive finger flexion. The goal of the study was to present the clinical features, increase awareness, facilitate accurate diagnosis, and report the outcomes after surgery. Thirty-five hands, from 22 patients with the main features of allodynia and lack of full finger flexion, were gathered in the period 2014-2021. The other common complaints included sleeping disturbances (20 patients), hand swelling (31 hands), and shoulder pain on the same side as the hand problem with limited range of motion (30 sides). The Tinel or Phalen signs were obscured by the pain. However, pain with passive flexion of the fingers was universally present. All the patients were treated with carpal tunnel release through a mini-incision approach: four patients had a trigger finger, which was treated concomitantly in six hands, and one patient underwent contralateral CTR for carpal tunnel syndrome with a more standard presentation. At a minimum of 6 months of follow-up (mean, 22 months; range, 6-60 months), the pain decreased by 7.5 ± 1.9 points on the Numerical Rating Scale, which ranges from 0 to 10. The pulp-to-palm distance improved from 3.7 to 0.3 cm. The mean Disabilities of the Arm, Shoulder, and Hand score decreased from 67 to 20. The mean Single-Assessment Numeric Evaluation score for the whole group was 9.7 ± 0.6. Hand allodynia and lack of finger flexion may be indications of median neuropathy in the carpal canal, which responds to CTR. Awareness of this condition is important because the uncharacteristic clinical presentation may not be considered an indication for surgery that can be beneficial. Therapeutic IV.

Early stages wind load assessment using Computational Fluid Dynamics: The new Bologna Stadium roof

The use of Computational Fluid Dynamics (CFD) is rapidly expanding, allowing to complement traditional wind tunnel tests even in the case of extremely complex geometries at reasonable computational costs. In this contribution, we report the experience gained in the preliminary study of the new roof over the Bologna Stadium. The study, performed prior to wind tunnel tests, is meant to provide the designer a first evaluation of wind loads in early design stages, with classical wind tunnel tests planned at the final design stage. The most critical loading conditions are identified and the structural response evaluated. Finally, the structural response sensitivity to damping, which is difficult to be accurately evaluated a priori, is assessed. The study shows how early CFD simulations can effectively complement traditional wind tunnel tests in the project development.

Comprehensive CFD Aerodynamic Simulation of a Sport Motorcycle

Nowadays, aerodynamics is a key focal point in the vehicle design process. Beyond its direct impact on the performance of a vehicle, it also has significant effects on economics and safety. In the last decade numerical methods, mainly Computational Fluid Dynamics (CFD), have established themselves as a reliable tool that assists in the design process and complements classical tunnel tests. However, questions remain about the possible obtained accuracy, best practices and applied turbulence models. In this paper, we present a comprehensive study of motorcycle aerodynamics using CFD methods which, compared to the most common car aerodynamics analysis, has many specific features. The motorcycle, along with its rider, constitutes a shape with very complex aerodynamic properties. A detailed insight into the flow features is presented with detailed commentary. The front fairing, the front wheel and its suspension were identified as the main contributors to the aerodynamic drag of the motorcycle and its rider. The influence of rider position was also studied and identified as one of the most important elements when considering motorcycle aerodynamics. An extensive turbulence models study was performed to evaluate the accuracy of the most common Reynolds-averaged Navier–Stokes models and novel hybrid models, such as the Scale Adaptive Simulation and the Delayed Detached Eddy Simulation. Similar values of drag coefficients were obtained for different turbulence models with noticeable differences found for k−ϵ models. It was also observed that near-wall treatment affects the flow behaviour near the wheels and windshield but has no impact on the global aerodynamic parameters. In the summary, a discussion about the obtained results was set forth and a number of questions related to specifics of motorcycle CFD simulations were addressed.

Some Misconceptions in the Treatment of Cubital Tunnel Syndrome, Radial Tunnel Syndrome, and Median Nerve Compression in the Forearm.

This article discusses ulnar, median, and radial nerve compression in the proximal forearm and elbow and some possible common misconceptions. In particular, the ligament of Struthers extremely rarely causes ulnar neuropathy. Lacertus syndrome and flexor superficialis-pronator syndrome can be diagnosed separately. Surgical release can be through a small incision. Acronyms for compression to radial nerve in proximal forearm can be simplified to radial tunnel syndrome, which includes a mild type (classical radial tunnel syndrome) and a severe type (posterior interosseous nerve (PIN) compression).

Outcomes of Carpal Tunnel Release in Complex Regional Pain Syndrome/Reflex Sympathetic Dystrophy/Sudeck Disease Patients.

The clinical features of classic carpal tunnel syndrome are well known. However, some patients who display atypical symptoms and signs of pain and dysesthesias in the hand, worsening of symptoms at night, and above all, inability to make a full fist, respond equally well to carpal tunnel release. This same clinical picture was shared by some patients labeled as having complex regional pain syndrome. Because of the poor outcome of complex regional pain syndrome patients with current regimens, the authors tested the hypothesis that carpal tunnel release could be effective on them. The purpose of this article is to report the outcome of carpal tunnel release in complex regional pain syndrome patients who presented the above signs and symptoms. Fifty-three patients with an average age of 55 years presenting the above cluster of symptoms were operated on. All were unilateral cases, had sustained trauma, and were treated for complex regional pain syndrome before referral for an average of 16 months. All patients underwent carpal tunnel release. At a minimum of 6 months' follow-up, pain dropped 7.5 points on a numerical rating scale of 0 to 10 ( p < 0.001). Disabilities of the Arm, Shoulder and Hand scoring fell from 82 to 17 ( p < 0.001). Six patients had an unsatisfactory result. Some patients with complex regional pain syndrome may respond successfully to a carpal tunnel release operation. Recognition of this possibility is crucial, as the symptoms and signs might lead the clinician away from the proper diagnosis and treatment. Therapeutic, IV.

Switching plasmonic nanogaps between classical and quantum regimes with supramolecular interactions.

In the realm of extreme nanophotonics, nanogap plasmons support reliable field enhancements up to 1000, which provide unique opportunities to access a single molecule for strong coupling and a single atom for quantum catalysis. The quantum plasmonics are intriguing but difficult to modulate largely because of the lack of proper spacers that can reversibly actuate the sub–1-nm gaps. Here, we demonstrate that supramolecular systems made of oligoamide sequences can reversibly switch the gap plasmons of Au nanoparticles on mirror between classical and quantum tunneling regimes via supramolecular interactions. The results reveal detailed plasmon shift near the quantum tunneling limit, which fits well with both classical- and quantum-corrected models. In the quantum tunneling regime, we demonstrate that plasmonic hot electron tunneling can further blue shift the quantum plasmons because of the increased conductance in the nanogaps, making it a promising prototype of optical tunable quantum plasmonic devices.

Interpreting attoclock experiments from the perspective of Bohmian trajectories

We theoretically study the attoclock using the Bohmian trajectory. The Bohmian trajectory includes a nonlocal quantum potential and the Coulomb potential, allowing us to separately study their effects on the attoclock. We show that the quantum potential has a significant effect on the photoelectron momentum spread while it only slightly affects the offset angle in the attoclock. We further show how the Coulomb potential affects the offset angle, revealing that the Coulomb force before the electron reaches the position of the classical tunnel exit has a significant contribution to the offset angle. Thus taking the full Coulomb effect into account during the tunneling ionization is a prerequisite for our understanding of the origin of the offset angle in the attoclock experiment. Our study also implies that there might be an inertia time for the initial wave function in response to the change of the laser electric field.

Global minimization via classical tunneling assisted by collective force field formation.

Simple elements interacting in networks can give rise to intricate emergent behaviors. Examples such as synchronization and phase transitions often apply in many contexts, as many different systems may reduce to the same effective model. Here, we demonstrate such a behavior in a model inspired by memristors. When weakly driven, the system is described by movement in an effective potential, but when strongly driven, instabilities cause escapes from local minima, which can be interpreted as an unstable tunneling mechanism. We dub this collective and nonperturbative effect a “Lyapunov force,” which steers the system toward the global minimum of the potential function, even if the full system has a constellation of equilibrium points growing exponentially with the system size. This mechanism is appealing for its physical relevance in nanoscale physics and for its possible applications in optimization, Monte Carlo schemes, and machine learning.

COMPARATIVE ANALYSIS OF EXCAVATION AND TUNNEL SOLUTIONS FOR THE ROAD DRENOVO - RAEC

&amp;lt;jats:p&amp;gt;When withdrawing the route of the expressway Drenovo - Raec, the axis of the road is forced to stretch near or through the mountain massifs. This created a general dilemma, whether to make classical excavations or tunnel constructions in certain locations. Considerations were also made for the decision on high embankments or viaducts. The characteristic location presented in this paper is located between the existing national road and the river Raec. For this location, a comparative analysis of the variant solutions for excavation and tunnel was made and the main parameters that affect the final solution were indicated.&amp;lt;/jats:p&amp;gt;

Histological and radiographic evaluation of three common tendon transfer techniques in an un-ossified bone porcine model: implications for early anterior tibialis tendon transfers in children with clubfeet.

PurposeTo compare the histological healing and radiographic effects of tendons transferred to ossified or unossified bone using different tendon fixation techniquesMethodsNine new-born piglets underwent bilateral tendon transfers to either the ossified boney calcaneal body or unossified apophysis. The tendons were fixed using metallic suture anchors, sutures alone or a bone tunnel. At six weeks of age, calcanei were harvested, radiologically imaged and then prepared for histology. A semi-quantitative aggregated scoring system with values ranging from 0 (poor) to 15 (excellent), was used to grade healing at the surgical enthesis and the apophyseal ossification was graded by five independent reviewers in triplicate using a modified (1 to 4) validated scoring system.ResultsHistologically, the cartilaginous transfers utilizing the tunnel and suture techniques also demonstrated the best average aggregated scores of entheses healing rivalling that measured in transfers using the classic bone tunnel technique (clinical benchmark), whereas suture anchor fixation demonstrated the worst healing in both the ossified and unossified samples. All three transfer techniques caused at least minor alterations in apophyseal ossification, with the most significant changes observed in the metallic suture anchor cohort. The tunnel and suture techniques demonstrated similar and more mild abnormalities in ossification.ConclusionTendon transfers to unossified bone heal histologically as well as transfers classically performed through tunnels in bone. Suture fixation or tunnel techniques appear radiographically and histologically superior to suture anchors in our newborn porcine model.Level of evidence

Wind Tunnel Wind Speed Control System Based on PLC Fuzzy Algorithm

With the deterioration of wind erosion, wind tunnel test has become an important method to study wind erosion. Wind speed control and data collection and processing are essential links in wind tunnel testing. The performance of wind speed control system directly affects the efficiency of wind tunnel test and the accuracy of test data. An incremental PLC fuzzy algorithm is used to realize the stable control of wind speed and improve the accuracy and reliability of the test, thus providing accurate and reliable experimental data for the study of wind speed control system in wind tunnel. And under the condition of large delay and instability, the PLC fuzzy algorithm can control the wind speed of wind tunnel more obviously. This paper takes the PLC fuzzy algorithm as the theoretical basis of the research, uses the fuzzy algorithm as the main research algorithm, integrates its important content to carry on the analysis research to the PLC fuzzy algorithm realization PID control to optimize the wind speed control system of the wind tunnel. Based on the classical wind tunnel wind speed control system, the PID control system is optimized and improved. PLC fuzzy algorithm can be regarded as a node sorting algorithm, so it can be used to construct wind tunnel wind speed control system. The experimental results show that this study has a better effect on the optimization design of wind speed control system by using PLC fuzzy algorithm to realize PID control.

A mini-incision carpal tunnel release technique to prevent pillar pain: A technical note.

Pillar pain represents one of the most common complications of classic open carpal tunnel release (CTR). This complication causes a sense of discomfort worse than the compression syndrome itself. We, herein, introduce a new treatment method for CTR through a mini-incision, which allows subcutaneously cutting the transverse carpal ligament (TCL) and releasing the median nerve without neurovascular complications. This mini-incision approach can allow the direct visualization and preservation of the thenar motor branch in those rare cases where it has an aberrant origin. For the past 10 years, we have consecutively performed this technique in the surgical treatment of 318 patients with the diagnosis of primary CTS, without developing any neurovascular and tendon injuries as well as pillar pain.

Air flow quality analysis of an open-circuit boundary layer wind tunnel and comparison with a closed-circuit wind tunnel

The wide use of wind tunnels, as a tool to measure the flow properties and the flow effects on different structures/ecosystems, makes it necessary to guarantee the correct functioning of the facility and to carry out a continuous monitoring. The aim of this work is (i) to check the homogeneity and quality of the air flow in an open-circuit boundary layer wind tunnel, (ii) to provide data and ideas that could help other researchers to improve similar tunnels, and (iii) to compare some of the results with the behavior of a classic closed-circuit wind tunnel. Experiments are carried out working with a constant reference velocity, using a hot cross wire anemometry system to obtain high resolution measurements, in the entrance and test sections for different longitudinal and cross planes. The results concern the characteristics of the mean and turbulent flow. In this manuscript, we report the analysis of the turbulence production, the Reynolds stresses, the vertical velocity skewness, the vorticity, and the spectral properties, and a quadrant decomposition is also performed. Finally, comparing the results with respect to a closed-circuit wind tunnel, it is shown that the turbulence intensity is generally higher and the mean flow is more homogeneous in the present open-circuit wind tunnel. Moreover, the Reynolds number is similar in both tunnels, which indicates that both tunnels are mechanically similar.

A Priori Validation of Subgrid-scale Models for Astrophysical Turbulence

Abstract We perform a priori validation tests of subgrid-scale (SGS) models for the turbulent transport of momentum, energy, and passive scalars. To this end, we conduct two sets of high-resolution hydrodynamical simulations with a Lagrangian code: an isothermal turbulent box with rms Mach numbers of 0.3, 2, and 8, and the classical wind tunnel where a cold cloud traveling through a hot medium gradually dissolves due to fluid instabilities. Two SGS models are examined: the eddy diffusivity (ED) model widely adopted in astrophysical simulations and the “gradient model” due to Clark et al. We find that both models predict the magnitude of the SGS terms equally well (correlation coefficient &gt;0.8). However, the gradient model provides excellent predictions for the orientation and shape of the SGS terms while the ED model predicts both poorly, indicating that isotropic diffusion is a poor approximation to the instantaneous turbulent transport. The best-fit coefficient of the gradient model is in the range of [0.16, 0.21] for the momentum transport, and the turbulent Schmidt number and Prandtl number are both close to unity, in the range of [0.92, 1.15].

Correlation between Kink effect and trapping mechanism through H1 hole trap in Al0.22Ga0.78N/GaN/SiC HEMTs by current DLTS: field effect enhancement

A cryogenic investigation of the Kink effect with drain-source bias sweeping process during output characteristics is suggested. An exhaustive study of the field effect dependence on the emission rate from hole traps in AlGaN/GaN HEMT transistors has been realized by means of current DLTS spectroscopy (I-DLTS). We have found that the Kink effect was induced by impact ionization of electron trapped in acceptor-like deep levels with activation energies at about 0.85 eV overhead the valence band of the GaN buffer layer. Using I-DLTS method, three holes traps, labeled A, H1, and H5, have been distinguished. The H1 deep level might correspond to the carbon substituting the N site (CN) which is supposed to be the main cause of the Kink effect. The major H5 trap seems to be gallium vacancy complex (VGa–ON). For the hole trap H1, the phonon-assisted tunneling emission is the dominant mechanism for holes to escape from the trapping centers while for the H5 trap their field dependence shows a classical pure tunneling effect.

Ionization and acceleration of multiply charged gold ions in solid film irradiated by high intensity laser

In this paper, we present the mechanisms of ionization of a thin gold film irradiated by a high-intensity, short-pulse laser in the range of I=1020−22 W/cm2 and the associated acceleration of multiply charged gold ions. A numerical one-dimensional simulation using an extended particle-in-cell code, which includes atomic and collisional relaxation processes, indicates that two types of acceleration, hole-boring radiation pressure acceleration (RPA) and target normal sheath acceleration (TNSA), contribute to the generation of highly charged ions with kinetic energies on the order of 10 MeV/u. In each acceleration, a longitudinal electrostatic field excited by different mechanisms dominantly ionizes atoms to higher charge states and accelerates them to the vacuum region from the rear surface, which is opposite the front surface irradiated by the laser field. The field ionization process dominantly ionizes high energy ions to the high charge state, while a large number of ions with energy &amp;lt;1 MeV/u are ionized by an electron impact ionization process. In TNSA, a multiply charged ion generated at the rear surface is accelerated to the maximum energy although the ion with the highest charge state is generated at the front surface in RPA. However, the existence of contamination, such as water vapor, suppresses the ion energy of TNSA to less than that of RPA since the sheath field readily accelerates the protons and oxygen prior to the acceleration of the gold ions. Our derived theoretical scaling describes the maximum ion energy for each charge state in the cases with and without contamination using the relationship between the longitudinal electrostatic field profile near the rear surface and the classical tunnel field ionization model.