Classical Joint Research Articles

Preparing Ground and Excited States Using Adiabatic CoVaR

Abstract CoVarince Root finding with classical shadows (CoVaR) was recently introduced as a new paradigm for training variational quantum circuits. Common approaches, such as variants of the Variational Quantum Eigensolver, aim to optimise a non-linear classical cost function and thus suffer from, e.g., poor local minima, high shot requirements and barren plateaus. In contrast, CoVaR fully exploits powerful classical shadows and finds joint roots of a very large number of covariances using only a logarithmic number of shots and linearly scaling classical \BLUE{computing} resources. As a result, CoVaR has been demonstrated to be particularly robust against local traps, however, its main limitation has been that it requires a sufficiently good initial state. We address this limitation by introducing an adiabatic morphing of the target Hamiltonian and demonstrate in a broad range of application examples that CoVaR can successfully prepare eigenstates of the target Hamiltonian when no initial warm start is known. CoVaR succeeds even when Hamiltonian energy gaps are very small -- this is in stark contrast to adiabatic evolution and phase estimation algorithms where circuit depths scale inversely with the Hamiltonian energy gaps. On the other hand, when the energy gaps are relatively small then adiabatic CoVaR may converge to higher excited states as opposed to a targeted specific low-lying state. Nevertheless, we exploit this feature of adiabatic CoVaR and demonstrate that it can be used to map out the low lying spectrum of a Hamiltonian which can be useful in practical applications, such as estimating thermal properties or in high-energy physics.

Estimation of the graft failure by current value joint model, and extension to alternative parameterization structures: Cohort study.

In clinical practice, individuals are followed up to predict the outcome event of interest, and their longitudinal measurements are collected on a regular or irregular basis. We aimed to examine the classical approach, joint model (JM), and alternative parameterization structures using data on the effect of time-varying longitudinal measurements on survival. The motivating cohort dataset included 158 consecutive kidney transplant recipients who had baseline and follow-up data. Although the longitudinal log-transformed estimated glomerular filtration rate (log[eGFR]) measurements and graft failure have an association clinically, the 2 processes are analyzed separately in the classical approach. In addition to the extended Cox model, the current value JM, the weighted cumulative effect JM, and dynamic predictions were performed in the study, by taking advantage of R codes. Of the 158 patients, 34.8% were males. The mean age was 29.8 ± 10.9 years, and the median age was 26 years at the time of transplantation. The hazard ratio for graft failure was 8.80 for a 1-unit decrease in log(eGFR) in the extended Cox model, 10.58 in the current value JM, and 3.65 in the weighted cumulative effect JM. The presence of coronary heart disease was also found to be associated with log(eGFR): 0.199 (P = .03) for the current value JM and 0.197 (P = .03) for the weighted cumulative effect JM. The current value JM was identified as a better model than the extended Cox model and the weighted cumulative effect JM based on parameter and standard error comparison and goodness of fit criteria. JMs should be preferred, as they facilitate better clinical decisions by accounting for the varying slopes and longitudinal variation of estimated glomerular filtration rate among patients. Suitable types of models should be practiced depending on baseline biomarker levels, their trends over time, the distribution of the biomarkers, and the number of longitudinal biomarkers.

A novel Osteoarthritis scoring system to separate typical OA joint degeneration from non-typical lesions in male Sprague Dawley rats

ObjectiveTo develop a novel scoring system to characterize osteoarthritis-related degeneration distinct from spontaneous subchondral bone lesions observed in the tibia and femur of male Sprague Dawley rats. MethodKnee joints from male rats following 12 weeks of a diet-induced obesity model of osteoarthritis (OA) were assessed. OA histopathological changes (OAHC) were assessed in the knee joints. All scores were evaluated using a modified Mankin score and a modified Osteoarthritis Research Society International histological score. OAHC were divided into 3 categories: (I) Typical OA score evaluating the changes in cartilage structure, cellularity, proteoglycan depletion, and tidemark integrity, (II) A novel Non-typical OA score evaluating cartilage integrity, and the size of local thickening, fragmentation and degeneration along the tidemark and the size and severity of the subchondral bone lesion, and (III) Total OA score comprised of both, the Typical and the Non-typical scores. ResultsRats exposed to a high fat/high sucrose diet had higher Typical OA score compared to a control group (Chow). Non-typical and Total OA scores revealed no differences in the severity of the lesions between the HFS and the Chow group animals. All scoring systems had excellent intra- and inter-examiner reliability. ConclusionThe spontaneous bone lesions observed in male Sprague Dawley rats can obscure the effect of the diet-induced obesity if the classical scoring system is used to assess joint degeneration. The newly proposed scoring method provides a reliable method to distinguish classical OA joint degeneration from spontaneous Non-typical lesions occurring in these rats.

Characterizing the geometry of the Kirkwood–Dirac-positive states

The Kirkwood–Dirac (KD) quasiprobability distribution can describe any quantum state with respect to the eigenbases of two observables A and B. KD distributions behave similarly to classical joint probability distributions but can assume negative and nonreal values. In recent years, KD distributions have proven instrumental in mapping out nonclassical phenomena and quantum advantages. These quantum features have been connected to nonpositive entries of KD distributions. Consequently, it is important to understand the geometry of the KD-positive and -nonpositive states. Until now, there has been no thorough analysis of the KD positivity of mixed states. Here, we investigate the dependence of the full convex set of states with positive KD distributions on the eigenbases of A and B and on the dimension d of the Hilbert space. In particular, we identify three regimes where convex combinations of the eigenprojectors of A and B constitute the only KD-positive states: (i) any system in dimension 2; (ii) an open and dense probability one set of bases in dimension d = 3; and (iii) the discrete-Fourier-transform bases in prime dimension. Finally, we show that, if for example d = 2m, there exist, for suitable choices of A and B, mixed KD-positive states that cannot be written as convex combinations of pure KD-positive states. We further explicitly construct such states for a spin-1 system.

Role of Autologous Micro-Fragmented Adipose Tissue in Osteoarthritis Treatment.

Osteoarthritis (OA) is the most common complex musculoskeletal disorder, resulting from the degeneration of the articular cartilage and characterized by joint pain and dysfunction that culminate in progressive articular cartilage loss. We present our experience in the management of hip and knee OA by means of the intra-articular injection of fat micrograft, describing our approach, which was developed from the belief in the powerful reparative effect of autologous fat graft on damaged tissue, as well as its natural lubricating effect on the joints. Inclusion criteria were as follows: men and women, aged 20 to 80 years, that referred articular pain of the hips and/or knees, showing initial-stage degenerative OA. From October 2018 to July 2023, a total of 250 patients underwent treatment with the Sefficare® device (SEFFILINE srl, Bologna, Italy). The Superficial Enhanced Fluid Fat Injection device was used to perform autologous regenerative treatments in a safe, standardized, easy, and effective way on 160 women, 64%, and 90 men, 36%. A total of 190 procedures (76%) involved the knees, with 20 patients who were bilaterally treated, while 60 procedures, all unilateral, involved the hips (24%). The mean age at treatment was 52.4 years. Before treatment, each patient had undergone X-rays and Magnetic Resonance Imaging (MRI) of the painful hip/knee to evaluate and grade the articular OA. Postoperatively, each patient was assessed after one, three, six, and twelve months. The donor site postoperative course was uneventful other than minimal discomfort. Clinically, the ROM (range of motion) of the treated knee/hip increased an average of 10 degrees 3 months after treatment, but the stiffness was reduced, as reported by the patients. The VAS (Visual Analog Scale) was submitted at 3, 6, and 12 months, demonstrating a progressive reduction of pain, with the best score obtained at six months postoperatively. In total, 85% of patients were satisfied one year after treatment, with a considerable improvement in pain and quality of life. The satisfactory outcome of this minimally invasive procedure indicates that the intra-articular injection of fat micrograft can replace or considerably delay the need for the classical major joint replacement surgery, thanks to its impact on the quality of life of patients and financial cost.

Bio-inspired Generative Design for Contact Interfaces

Synovial joints are known by their resistance to wear as they can withstand millions of load cycles. Such performance is attributed to the development process where joints are adapted to the loading environment. In engineering applications, wear is frequently a cause of failure. Classical joint design usually leads to uneven pressure distribution, accelerating wear in concentrated regions. In this work, we use a bio-inspired design methodology to generate contact interfaces. The key point of this methodology is the use of the growth rules of synovial joint during development. Specifically, hydrostatic stress promotes growth and high shear stress inhibits it. We apply these rules in an iterative algorithm to generate contact interfaces adapted to the loading environment. We present a case study to generate the shape of body in frictionless contact with an elastic half space using the bio-inspired approach. We compare the pressure and wear distribution between the bio-inspired and classical designs. The results highlight that the bio-inspired methodology produces almost uniform contact pressure and wear distribution, in contrast to the concentration inherent in classical designs. Thus, this study accentuates the potential advantages of this bio-inspired methodology, offering a compelling avenue for achieving high-performance contact interfaces.

Efficient Formulation for Vendor–Buyer System Considering Optimal Allocation Fraction of Green Production

The classical joint economic lot-sizing (JELS) policy in a single-vendor single-buyer system generates an equal production quantity in all cycles, where the input parameters remain static indefinitely. In this paper, a new two-echelon supply chain inventory model is developed involving a hybrid production system. The proposed model simultaneously focuses on green and regular production methods with an optimal allocation fraction of green and regular productions. Unlike the classical mathematical formulation, cycles do not depend on each other, and consequently, each model parameter can be adjusted to be responsive to the dynamic nature of demand rate and/or price fluctuation. A rigorous heuristic approach is used to derive a global optimal solution for a joint hybrid production system. This paper accounts for carbon emissions from production and storage activities related to green and regular produced items along with transportation activity under a multi-level emission-taxing scheme. The results emphasize the significant impact of green production on emissions. That is, the higher the allocation fraction of green production, the lower the total amount of emissions generated by the system, i.e., the system becomes more sustainable. Adopting a hybrid production method not only decreases the greenhouse gas (GHG) emissions dramatically, but also reduces the minimum total cost per unit time when compared with regular production. One of the main findings is that the total system cost generated by the base closed-form formula of the proposed model is considerably lower in the first cycle (subsequent cycles) than that of the existing literature, i.e., 33.59% (16.13%) when the regular production method is assumed. Moreover, the optimal production rate generated by the proposed model is the one that minimizes the emissions production function. In addition, the system earns further revenue by utilizing a mixed transportation policy that combines the Truck Load (TL) and Less than Truck Load (LTL) services. Illustrative examples and special cases that reflect different realistic situations are compared to outline managerial insights.

A new skeletal model for the ankle joint complex

AbstractThe talocrural and the talocalcaneal articulations collectively form the ankle joint complex of the human foot and are the focus of investigation of this work. The talocrural articulation enables plantarflexion and dorsiflexion, while the talocalcaneal articulation allows inversion and eversion of the foot. A comprehensive analysis of the literature suggests that the ankle joint complex is modeled in different manners considering approaches with varying complexity levels, which more or less accurately mimic its intrinsic anatomical features. Several studies assume that the foot articulates with the leg via the talocrural articulation only, which is modeled as a revolute joint. Other studies consider the movements allowed by both articulations and model the ankle joint complex as spherical, revolute, or classical universal joints. Most existing approaches do not consider sufficiently accurate anatomical modeling of this joint complex. Thus, this work presents a new skeletal model for the ankle joint complex of the human foot that considers the actual anatomy and movements of the talocrural and the talocalcaneal articulations. The proposed approach uses a modified universal joint, which incorporates a massless link to mimic the actual function of the talus bone. The developed formulation is compared with a model available in the literature, which uses a classical universal joint. The outcomes show that modeling the ankle joint complex as a modified universal joint allows a more realistic representation of the anatomy of the human foot. The main differences between the two joint models are observed in the mediolateral direction.

Probabilistic deconstruction of a theory of gravity, part I: Flat space

We define and analyze a stochastic process in anti-de Sitter Jackiw-Teitelboim gravity, induced by the quantum dynamics of the boundary and whose random variable takes values in AdS_2AdS2. With the boundary in a thermal state and for appropriate parameters, we take the asymptotic limit of the quantum process at short time scales and flat space, and show associated classical joint distributions have the Markov property. We find that Einstein’s equations of the theory, sans the cosmological constant term, arise in the semi-classical limit of the quantum evolution of probability under the asymptotic process. In particular, in flat Jackiw-Teitelboim gravity, the area of compactified space solved for by Einstein’s equations can be identified as a probability density evolving under the Markovian process.

The Performance Investigation of Smart Diagnosis for Bearings Using Mixed Chaotic Features with Fractional Order.

This article presents a performance investigation of a fault detection approach for bearings using different chaotic features with fractional order, where the five different chaotic features and three combinations are clearly described, and the detection achievement is organized. In the architecture of the method, a fractional order chaotic system is first applied to produce a chaotic map of the original vibration signal in the chaotic domain, where small changes in the signal with different bearing statuses might be present; then, a 3D feature map can be obtained. Second, five different features, combination methods, and corresponding extraction functions are introduced. In the third action, the correlation functions of extension theory used to construct the classical domain and joint fields are applied to further define the ranges belonging to different bearing statuses. Finally, testing data are fed into the detection system to verify the performance. The experimental results show that the proposed different chaotic features perform well in the detection of bearings with 7 and 21 mil diameters, and an average accuracy rate of 94.4% was achieved in all cases.

Mean-Field-Aided Multiagent Reinforcement Learning for Resource Allocation in Vehicular Networks

As one technique for autonomous driving, vehicular networks can achieve high efficiency with vehicle-and-infrastructure cooperation, bringing high safety and many value-added services. To achieve higher communication efficiency, much effort has been done to cope with the resource allocation issues for vehicular networks. Nevertheless, due to the strong nonconvexity and nonlinearity, the classical joint resource allocation problem in vehicular networks is typically NP-hard. The multiagent reinforcement learning (MARL) has emerged as a promising solution to tackle this challenge but its stability and scalability are not satisfactory when the amount of vehicles gets increased. In this article, we mainly investigate the issue of joint spectrum and power allocation in vehicular communication networks, and carefully consider the interactions between the vehicles and environment by incorporating the cooperative stochastic game theory with MARL, named complete-game MARL (CG-MARL), to achieve a better convergence and stability with the theoretical computational complexity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {O}(n^{N})$ </tex-math></inline-formula> with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> denoting the dimension of action space and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> denoting the number of V2X Vehicular. Furthermore, the mean-field game (MFG) theory is employed to further enhance the MARL for decreasing the horrible computing resource consumption caused by the CG-MARL to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {O}(n^{2})$ </tex-math></inline-formula> while maintaining an approximate performance. The simulation results demonstrate that the proposed mean-field-aided MARL (MF-MARL) for vehicular network resource allocation can achieve 95% near-optimal performance with much lower complexity, which indicates its significant potentials in the scenarios with massive and dense vehicles.

Experimental Counterexample to Bell's Locality Criterion.

The EPR paradox was caused by the provision that quantum variables must have pre-existing values. This type of "hidden property realism" was later falsified by Bell's Theorem. Accordingly, the physical basis for action-at-a-distance between entangled quanta was removed. Yet, modern interpretations present Bell's inequality as a Locality Criterion, as if Bell violations can only happen at the quantum level, and only with remote interactions. This is a questionable practice, considering that classical joint measurements also violate such inequalities for mutually exclusive wave properties. In particular, consecutive measurements of polarization produce the same coefficients of correlation as parallel measurements with entangled quanta, yet they are explicitly local. Furthermore, it is possible to combine parallel and consecutive measurements of Type I polarization-entangled photons in a single experiment, conclusively showing that quantum Bell violations can be local. Surprisingly, classical phenomena also require nonlocal interpretations if pre-existing properties are taken for granted. Hence, the solution is to reject the models with pre-existing properties for both classical and quantum wave-like phenomena.

Stability of shuffled switched linear systems: A joint spectral radius approach

A switching signal for a switched system is said to be shuffled if all modes of the system are activated infinitely often. In this paper, we develop tools to analyze stability properties of discrete-time switched linear systems driven by shuffled switching signals. We introduce the new notion of shuffled joint spectral radius (SJSR), which intuitively measures how much the state of the system contracts each time the signal shuffles (i.e. each time all modes have been activated). We show how this notion relates to stability properties of the associated switched systems. In particular, we show that some switched systems that are unstable for arbitrary switching signals can be stabilized by using switching signals that shuffle sufficiently fast and that the SJSR allows us to derive an expression of the minimal shuffling rate required to stabilize the system. We then present several approaches to compute lower and upper bounds of the SJSR using tools such as the classical joint spectral radius, Lyapunov functions and finite state automata. Several tightness results of the bounds are established. Finally, numerical experiments are presented to illustrate the main results of the paper.

Numerical method to assess the stress state and gradients induced by thermo-oxidation in adhesively bonded joints for aircraft engine applications

This paper presents a finite element numerical method to assess the stress state and gradients induced by thermo-oxidative ageing in Ti/epoxy/Ti adhesively bonded joints for aircraft engine applications. The method is dealing with couplings between thermal, chemistry and mechanics occurring during high-temperature ageing of the joint, taking into account post-curing stresses, and under mechanical loading. Calculations are carried out on a classical single lap joint configuration. An assessment of the stress state and the thermo-oxidation induced gradients at each step of the ageing process is carried out. It is shown that the stress state within the adhesive results from the superposition of several physical fields and is strongly affected by the thermo-oxidation gradients. Moreover, post-curing stresses cannot be neglected when compared to the adhesive yield stress. Numerical analyses are of paramount importance to assess the complex stress fields related to multiphysics couplings and for joint design.

A practical approach for sampling the Longuet–Higgins distribution for engineering applications

The Longuet–Higgins distribution is a classical joint probability distribution of wave periods and amplitudes still being used for comparison against current approaches in coastal engineering and other applications. However, comparisons are carried out against the theoretical distribution rather than against jointly simulated values. Some formulae to implement the generation of jointly distributed wave amplitudes and periods is unavailable. A practical approach is proposed in this study to cope with this issue. Expressions for the marginal and conditional cumulative distribution functions of the Longuet–Higgins​ distribution based on the error function, not reported in the literature, are provided. Resulting simulations are in good agreement with the theoretical distributions. It is concluded that the developed equations are formal distributions based on probability theory, that the proposed method leads to adequate simulated values of jointly distributed wave heights and periods and that it is easy to implement in current software and suitable for engineering applications.

FE analysis of single-lap adhesive joints with tapered adherends

Adhesive joints are becoming increasingly popular in various industrial sectors. However, in spite of numerous recent studies in literature, the design phase of the adhesive joint is still challenging. The main issue in the design phase is the determination of the stress distribution in the adhesive layer under external mechanical loads. In the present study, a classical adhesive joint is analysed in comparison to its modified geometric configuration (i.e. tapered) aimed at reducing the magnitude of stress peaks. In particular, a single-lap joint with steel adherends bonded with a commercial epoxy adhesive is analysed. A 3D FE analysis is conducted to determine the distribution of normal and shear stresses in the mid-plane of the adhesive layer. The results obtained from the present study show that the inclusion of a small taper angle (i.e. 5°) leads to a remarkable reduction of normal stresses (up to 30%) compared to the classical configuration. It is observed that the further increase of the taper angle (up to 15°) does not lead to significant reductions of the stress peaks. The trend in shear stresses, on the other hand, is in contrast: an increase in the taper angle leads to an increase in the shear peaks. The method of tapering the adherends is effective in reducing the normal stresses, which are responsible for triggering the failure in the adhesive joint.

Weak measurements, non-classicality and negative probability

This paper establishes a direct, robust and intimate connection between (i) non classicality tests for various quantum features, e.g., non-Boolean logic, quantum coherence, nonlocality, quantum entanglement, quantum discord; (ii) negative probability, and (iii) anomalous weak values. It has been shown [Adhikary et al. Eur. Phys. J. D, 74(68):68, 2020] that nonexistence of a classical joint probability scheme gives rise to sufficiency conditions for nonlocality, a nonclassical feature not restricted to quantum mechanics. The conditions for nonclassical features of quantum mechanics are obtained by employing pseudo probabilities, which are expectation values of the parent pseudo projections. The crux of the paper is that the pseudo-probabilities, which can take negative values, can be directly measured as anomalous weak values. We expect that this opens up new avenues for testing nonclassicality via weak measurements, and also gives deeper insight into negative pseudo probabilities which become measurable. A quantum game, based on violation of classical probability rule is also proposed that can be played by employing weak measurements.

Normal and tangential behaviour of dry joints in refractory masonry

Industrial vessels used in high temperature processes of steel and cement production are protected by refractory linings built with mortarless joints. These dry joints, formed by stacked bricks have a crucial importance on the mechanical behaviour of the lining. The stiffness and consequently the stresses generated by the thermal elongation are reduced due to the joints. The present article presents the results of experimental and numerical tests on the thermomechanical behaviour of these joints. The compressive strength of the brick was assessed at ambient and high temperatures and a statistical analysis of the distribution of the bricks’ shape imperfections was carried out. Several studies have been carried out on the normal behaviour of the joints, such as: classical joint closure test; bed joint closing action in a masonry wallet measured with a DIC; effects of brick’s height imperfections on its loadbearing capacity; effects of brick’s height imperfections on the wall’s behaviour at ambient and high temperatures and a comparison between the bed and head joints behaviour. To characterize the joint’s tangential behaviour at high temperatures a novel device was developed and presented.

Controlling Interfacial Exchanges in Liquid Phase Bonding Enables Formation of Strong and Reliable Cu–Sn Soldering for High-Power and Temperature Applications

Developing solder joints capable of withstanding high power density, high temperature, and significant thermomechanical stress is essential to further develop electronic device performances. This study demonstrates an effective route of producing dense, robust, and reliable high-temperature Cu–Sn soldering by modifying the interfacial exchange during a transient liquid phase bonding (TLP) process. Our approach thus relies on altering internal phenomena (diffusion and transport of reactive species) rather than classical external TLP bonding parameters (e.g., time, temperature, and pressure). By adding a Cu3Sn-coated layer between Cu and Sn before the TLP process, fast dissolution of Cu in liquid Sn is achieved, altering undesired Cu6Sn5 scallop grain impingement and promoting their uniform growth within the liquid. A bonding and pore formation mechanism of the solder with or without the Cu3Sn-coated layer is proposed based on experimental and theoretical analysis. The developed TLP joint possesses a shear stress resistance of more than 80 MPa with a thermal cycle endurance superior to 1200 (−45–180 °C), making it highly reliable compared to a classical solder joint with shear and thermal cycling resistances of 45 and 500 MPa, respectively. The developed approaches thus provide an easy, affordable, and scalable method of producing a high-temperature and durable Cu–Sn joint for high-power module applications.

The Design of a Real-Scale Steel Moment-Resisting Frame for Pseudo-Dynamic Earthquake Testing

Background: Forthe reliable prediction of the non-linear response of structures, severe seismic events have proven to be a challenging task. Although much non-linear analysis software exists, the accuracy of the results depends on the assumptions made in the characterization of the members. Typically, the analytical models are calibrated using experimental observations. With this scope, experimental research remains the most reliable mean for the assessment of the seismic performance of structures, and it is crucial to target the development of new analytical models and design methods. Objective: Quasi-static tests can provide information on the non-linear behaviour of subassemblies, but it is often difficult to relate the imposed force or displacement histories to those that might occur during an earthquake. The pseudo-dynamic method combines an on-line computer simulation with experimental information about the tested structure, providing the application of realistic dynamic response histories. In this paper, the preliminary analysis and the design of a pseudo-dynamic testing facility for the experimental study of a real scale two storeys-two bays steel MRF, with classical and innovative joint details, are shown. Methods: Pushover and Incremental Dynamic Analyses carried out with Seismostruct software estimate the forces and displacements expected at each storey for the selected ground motions. These analyses have been performed by varying the structural detail of the beam-to-column connections. Results / Conclusion: In this paper, the analytical prediction of the performance of two bays-two storeys steel frames equipped with different solutions of beam-to-column joints is focused. Based on the performed analyses, it has been recognized that steel frames with partial strength joints can provide satisfactory performance under severe seismic actions provided that the joints are adequately designed.