bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity Analysis of Transient Forced Response of Mistuned Bladed Disks Under Complex Excitation and Varying Rotation Speed
Authors: Jing Tong , Zang Chaoping , Petrov Evgeny
Published: September 2023

During accelerations and decelerations of gas-turbine engines, the transient vibration effects in bladed disk vibration become significant and the transient response needs to be efficiently and accurately assessed. This paper develops an effective method for efficient calculations of the sensitivity of the transient vibration response for a mistuned-bladed disk under varying rotation speeds. The sensitivities are calculated concerning two major factors: (i) the blade mistuning and (ii) the rotor acceleration/deceleration rates. The method uses the large-scale finite element modeling of the bladed disk to accurately describe the dynamic properties of the mistuned bladed disk. The method can be applied for a case when the loading is the transient load, with the amplitude and frequency spectrum changing with rotation speed. The dependency of the modal characteristics on the rotation speed is included in the formulation of the sensitivity analysis method. Efficient reduced order models are used to reduce the computational cost, which can adapt to the effects of the varying rotation speed on the natural frequencies and mode shapes of the mistuned bladed disk under transient conditions. The expressions for the sensitivities are derived analytically which provides high accuracy and speed of the calculations. The method has been implemented in a computer code and thoroughly verified using a set of test cases. The studies of transient forced response sensitivity have been performed for realistic bladed disk models.
Preliminary Wear Investigations With Pressure Actuated Leaf Seals for Superheated Steam Turbine Application
Authors: Wittenberg Andreas , Rühle Tobias , Greving Johannes , Wichern Florian , Friedrichs Jens
Published: September 2023

Pressure actuated leaf seals (PALS) are a promising technology for the modern load-follow operation of power plants and turbines. Their strength lies in their radial adaptivity, which enables a significantly smaller radial gap height than conventional labyrinth seals. In this paper, which is a continuation of ISUAAAT16-022 from 2022, the operating behavior with compressed air and shaft rotation up to 3000 rpm is investigated, including an analysis of the wear caused by frictional contact between the shaft and the seal leaves. This includes both concentric and eccentric contact behavior. The test seal with a nominal diameter of 300 mm is designed in such a way that it can be used in a similar design in subsequent industry-related superheated steam tests. In addition to the seal performance before, during, and after the wear-in process, the frictional torques, temperatures in the flow and on the shaft-contacting leaves as well as the material removal on leaves and shaft running surface are analyzed. The results show a basically robust operating behavior of the seal with moderate performance deterioration, which can be directly attributed to the increase in the clear gap. However, the shaft wear is higher than for other contact seals, so further investigations are necessary before use in practice is feasible.
Investigating the Mixture Quality in Multi-Injector Burner Systems, Part II: Model Application
Authors: Macias Fabian Marquez , Hirsch Christoph , Sattelmayer Thomas , Huth Michael , Meisl Jürgen
Published: September 2023

Multi-injector burner systems offer a high spatial-temporal mixture homogeneity due to their small size and thus have a high NOx emission reduction potential at increasing flame temperatures. This potential is reduced due to the sensitivity of the mixing quality to inflow distortions caused by the flow path in the burner head. A deep understanding of the link between the inflow conditions and the mixture quality helps to optimize the flow field upstream of the injectors within the spatial and pressure loss constraints of gas turbine combustors to obtain minimal NOx emissions. This paper presents a new model approach for determining the mixture quality in multi-injector burners with output-based proper orthogonal decomposition (O-POD). The sensitivity to the inflow distortion is considered with the so-called observable vector, which describes the injector inflow conditions and is given as model input. The target quantity is the probability mass function (PMF) of the equivalence ratio at the injector outlet. This model allows a fast estimation of the mixing PMF for arbitrary inflow conditions, which is otherwise only accessible with complex time-resolved experimental or numerical approaches. The performance of the model was demonstrated with 21 reference datasets, for which a good agreement between the experimental results and the model output was obtained.
Comparison of the Flame Dynamics of a Liquid-Fueled Swirl-Stabilized Combustor for Different Degrees of Fuel-Air Premixing
Authors: Kaufmann Jan , Vogel Manuel , Sattelmayer Thomas
Published: September 2023

This study investigates the flame dynamics of lean premixed kerosene combustion for two different degrees of fuel–air premixing using a swirl stabilized burner with an axially movable twin fluid fuel injection nozzle. Thermal power, equivalence ratio, and atomizing air mass flow are varied systematically for both nozzle positions investigated. Measurements of the droplet size distribution at the nozzle exit are provided for all operation points. NOx emission measurements and OH*-chemiluminescence flame images show that stationary combustion characteristics significantly change with the nozzle position. Flame Transfer Functions (FTFs) are presented and interpreted for all operation points. The FTFs for the two configurations differ most in the low frequency range where the influence of the droplet dynamics is expected to be highest. For both configurations, a change in thermal power does not affect droplet size, flame shape, NOx emissions, and FTF. The observed trends in response to changes in equivalence ratio and atomizing air mass flow are opposite for both configurations. NOx emissions and flame shape are independent of the atomization air mass flow in the highly premixed configuration but not in the partially premixed configuration. In contrast to this, the FTF is affected by changes of the atomization air mass flow in both configurations, but again the trends are opposite. The observed trends for the highly premixed configuration are modeled and reproduced by a change in the phase relation between the equivalence ratio fluctuations and other instability driving mechanisms.
The Gold Mining Industry of Magadan Oblast under Sanctions: Risks for the Region
Authors: Galtseva N. V.
Published: September 2023

Abstract—

The introduction of a new package of sanctions in connection with the start of a military operation in Ukraine in 2022 is particularly changing the conditions for functioning of Russia’s gold mining industry, which uses high-performance foreign equipment for mining and sells its output on the global market. The article considers the factors complicating the industry and which have triggered an increase in production costs and decrease in the sale price of gold: a ban on foreign trade operations for the largest partner banks of subsoil users, an embargo by foreign countries on the purchase of Russian gold and import of foreign equipment and spare parts, and the Russian Central Bank’s decrease in the dollar/ruble exchange rate from May 2022 to January 2023. The case of a specific enterprise in Magadan oblast was used to assess the efficiency of placer gold mining under the changed conditions as of July 2022 and the forecast for 2023. Federal and regional measures were proposed to help smooth the severity of emerging problems in the industry and consequences for the economy of this single-resource northern region.
Impact of Digital Transformation on the Spatial Organization of Nonfood Retail in a Russian City
Authors: Aksenov K. E.
Published: September 2023

Abstract—

The objective of this study is to reveal what has changed under the influence of digital transformation in the “physical” spatial structure of the retail/purchase process in connection with the emergence of a choice between online and offline “spaces,” or environments, as well as how e-commerce has changed the “physical” spatial principles of organizing nonfood retail in a Russian city with a case study of St. Petersburg. The principles of placement of new e-commerce facilities were analyzed by comparing various shopping models and spatiotemporal systems formed by them, including specific objects (warehouses-stores, warehouses-distributors, order pickup points and parcel terminals), features of interaction between retail actors and transport and logistics flows in the city. Two opposing trends in the placement of new types of retail facilities are described: towards the transfer of the trading function to non-trading premises and the transfer of the non-trading retail function to retail premises. They create spatial competition with traditional retail as well as a new hierarchical competition with office and warehouse business types. The trend towards retail infrastructure for durable goods to be within walking distance means the rollout of a new type of competition for locations: with FMCG sellers. The fact that in delivery the logistics of the “last mile” passes from consumer to seller/logistician means a fundamental shift in the economic geography of goods flows. Instead of private spontaneous pedestrian flows, it forms new regulated small-tonnage types of “last mile” commercial cargo transportation using both alternative transport modes (personal transporter) and transport routes (sidewalks, pedestrian walkways, etc.). All these require the development of a new urban regulation policy.
Endovascular treatment of dural arteriovenous fistulas involving the vein of Galen: a single-center cohort and meta-analysis
Authors: Lauzier David C , Ullman Henrik , Hardi Angela , Derdeyn Colin , Cross Dewitte T , Moran Christopher J
Published: September 2023

Background

Dural arteriovenous fistulas (dAVFs) draining into the vein of Galen (VoG) are complex lesions that often necessitate treatment to minimize the risk of rupture and relieve symptoms. These lesions can be treated with open surgical resection, radiosurgery, or endovascular embolization. Unfortunately, endovascular treatment of dAVFs involving the VoG has not been robustly assessed across large patient cohorts. To meet this need, we performed a retrospective review of dAVFs involving the VoG at our center, and included these in a meta-analysis to identify the safety and efficacy of endovascular embolization, as well as describing current treatment trends for this disease.

Methods

Consecutive patients with dAVFs involving the VoG treated at a single center were identified from a prospective database and retrospectively reviewed. A literature search was conducted with defined search criteria, and eligible studies were included alongside our cohort in a meta-analysis. Rates of complete dAVF treatment and clinical complications were pooled across studies with a random effects model and reported with a 95% CI.

Results

Five dAVFs involving the VoG were treated endovascularly at our center during the study period. In this series, 80% of treatments led to complete occlusion of the fistula while no patients had clinical complications. Onyx was used for all treatments. In our meta-analysis, the overall rate of complete occlusion was 72.0% (95% CI 59.8% to 84.1%) and the overall rate of clinical complications was 10.0% (95% CI 4.7% to 15.3%).

Conclusions

Endovascular approaches for dAVFs involving the VoG are technically feasible, but carry a risk of clinical complications. Future work should identify optimal endovascular embolic agents.
Universality in low-dimensional BCS theory
Authors: Henheik Joscha , Lauritsen Asbjørn Bækgaard , Roos Barbara
Published: September 2023

It is a remarkable property of BCS theory that the ratio of the energy gap at zero temperature [Formula: see text] and the critical temperature [Formula: see text] is (approximately) given by a universal constant, independent of the microscopic details of the fermionic interaction. This universality has rigorously been proven quite recently in three spatial dimensions and three different limiting regimes: weak coupling, low density and high density. The goal of this short note is to extend the universal behavior to lower dimensions [Formula: see text] and give an exemplary proof in the weak coupling limit.
Diameter estimates under integral radial m-Bakry–Émery Ricci curvature bounds
Authors: Tadano Homare
Published: September 2023

By using some line integrals in terms of the radial [Formula: see text]-Bakry–Émery and radial [Formula: see text]-modified Bakry–Émery Ricci curvatures, we give various compactness criteria for complete Riemannian manifolds when [Formula: see text] is a positive constant, a negative constant, or infinity. Our results not only guarantee the compactness of complete Riemannian manifolds allowing the presence of negative amounts of the radial [Formula: see text]-Bakry–Émery and radial [Formula: see text]-modified Bakry–Émery Ricci curvatures, but also give new Myers-type theorems via [Formula: see text]-Bakry–Émery and [Formula: see text]-modified Bakry–Émery Ricci curvatures even the line integrals are reduced to pointwise positive lower bounds on the [Formula: see text]-Bakry–Émery and [Formula: see text]-modified Bakry–Émery Ricci curvatures. The key ingredients in proving our results are Riccati inequalities obtained from Bochner–Weitzenböck formulas via [Formula: see text]-Bakry–Émery and [Formula: see text]-modified Bakry–Émery Ricci curvatures.
MHD flow of a rotating micropolar fluid between two plates by using DTM
Authors: Gupta Reshu
Published: September 2023

The primary purpose of this work is to investigate the influence of a magnetic field on a micropolar fluid, which is rotating between two horizontally arranged parallel plates. A uniform magnetic field acts perpendicularly to the porous plate, which consumes fluid with a steady suction velocity. The obtained higher-order nonlinear partial differential equations (PDEs) are converted into nonlinear ordinary differential equations (ODEs) by using similarity transformation. A semi-analytical methodology has been applied to obtain the result to the problem. The influence of various flow parameters of the flow field like coupling parameter, viscosity parameter, Reynolds number, porosity parameter, rotation parameter and magnetic field parameter has been examined and explained by graphs. A resemblance between the results obtained by solving by the differential transform method (DTM) and the outcomes of the former research works has also been displayed which shows the correctness and efficiency of the used analytical method. The numerical values of the coefficient of skin friction at the lower plate are also displayed in tabular form and compared with the literature.
PRICING THE NATURAL CAPITAL SCARCITY UNDER CARBON NEUTRALITY IN CHINA
Authors: ZHAO YU , ZHANG NING
Published: September 2023

Pricing the natural capital is very critical for the achievement of carbon neutrality. This paper uses the Shephard input distance function to derive the shadow price of natural capital under regulatory constraints, which corrects the biased estimates without these constraints of previous studies. We relax the assumption of cost-minimizing behavior at market price and incorporate the price inefficiency in our model. This model is applied to the Chinese provincial dataset from 2004 to 2017. We observe that the average shadow prices of mineral, water, woodland and forest are 391[Formula: see text]CNY/metric tons of coal equivalent (tce), 0.13[Formula: see text]CNY/m3, 772[Formula: see text]CNY/hm2and 344[Formula: see text]CNY/hm2, respectively. For the dynamic effect, the shadow prices of natural capital rise sharply between 2004 and 2014. By testing the price efficiency, we demonstrate that regulatory constraints have an impact on shadow prices of natural capital in practice.
Separating notions in effective topology
Authors: Melnikov Alexander G. , Ng Keng Meng
Published: September 2023

We compare several natural notions of effective presentability of a topological space up to homeomorphism. We note that every left-c.e. (lower-semicomputable) Stone space is homeomorphic to a computable one. In contrast, we produce an example of a locally compact, left-c.e. space that is not homeomorphic to any computable Polish space. We apply a similar technique to produce examples of computable topological spaces not homeomorphic to any right-c.e. (upper-semicomputable) Polish space, and indeed to any arithmetical or even analytical Polish space. We then apply our techniques to totally disconnected locally compact (tdlc) groups. We prove that every computably locally compact tdlc group is topologically isomorphic to a computable tdlc group.
Confronting the Chaplygin gas with data: Background and perturbed cosmic dynamics
Authors: Sahlu Shambel , Sami Heba , Hough Renier , Elmardi Maye , Swart Anna-Mia , Abebe Amare
Published: September 2023

In this paper, we undertake a unified study of background dynamics and cosmological perturbations in the presence of the Chaplygin gas (CG). This is done by first constraining the background cosmological parameters of different Chaplygin gas models with SNeIa and [Formula: see text] data for detailed statistical analysis of the CG models. Based on the statistical criteria we followed, none of the models has substantial observational support, but we show that the so-called “original” and “extended/generalised” Chaplygin gas models have some observational support and less observational support, respectively, whereas the “modified” and “modified generalised” Chaplygin gas models miss out on the category less observational support, but cannot be ruled out. The so-called “generalised” cosmic Chaplygin gas model, on the other hand, falls under the no observational support category of the statistical criterion and can be ruled out. The models which are statistically accepted are considered for perturbation level in both theoretical and observational aspects. We also apply the [Formula: see text] covariant formalism of perturbation theory and derive the evolution equations of the fluctuations in the matter density contrast of the matter–Chaplygin gas system for the models with some or less statistical support. The solutions to these coupled systems of equations are then computed in both short-wavelength and long-wavelength modes. Then we feed these observationally restricted parameters into the analysis of cosmological perturbations to address the growth of density contrast through redshift. Using the most recent linear growth of the data [Formula: see text], CG models are considered to study the linear growth of the structure.
Analogy of spacetime as an elastic medium—Can we establish a thermal expansion coefficient of space from the cosmological constant Λ?
Authors: David Izabel
Published: September 2023

This paper advances the state-of-the-art by extending the study of the analogy between the fabric of spacetime and elasticity. As no prior work exists about a potential spacetime thermal expansion coefficient [Formula: see text], we explore the analogy of general relativity with the theory of elasticity by considering the cosmological constant [Formula: see text] as an additional space curvature of the structure of space due to a thermal gradient coming from the cosmic web and the cold vacuum and we propose [Formula: see text] with [Formula: see text] being the curvature radius of the space fabric. It follows from this analogy and from the supposed space model consisting of thin sheets of Planck thickness [Formula: see text] curved by this thermal gradient [Formula: see text]T a possible thermal expansion coefficient of the equivalent elastic medium modeling the space [Formula: see text] of the order of [Formula: see text][Formula: see text]K[Formula: see text]. As spacetime and not only space must be considered in general relativity, this paper also proposes an innovative approach which consists in introducing into the interval ds2 of special relativity a temperature effect [Formula: see text] (entropy variations correlated with time laps, based on temperature variations affecting always physically the clocks) based on different thermal expansion coefficients for space and time with for the flow of time [Formula: see text]. With [Formula: see text] 106[Formula: see text]K, [Formula: see text], the associate time interval is [Formula: see text][Formula: see text]s and [Formula: see text]. The consequence of this hypothesis is that dark energy potentially becomes a thermal spacetime curvature [Formula: see text] with [Formula: see text] equal to [Formula: see text] or [Formula: see text] depending of the temperature, the thermal entropy variation of the universe, the Planck thickness and time, that increases since the Big bang, depending on thermal expansion coefficients for spacetime [Formula: see text] and [Formula: see text] as a function, respectively, of [Formula: see text], [Formula: see text], in opposition to spacetime curvature gravity due to mass/energy density as described in general relativity.
Quintessential inflation and curvaton reheating
Authors: Agarwal Abhineet , Bekov Sabit , Myrzakulov Kairat
Published: September 2023

In this paper, we consider a model of quintessential inflation based upon inverse hyperbolic potential. We employ curvaton mechanism for reheating which is more efficient than gravitational particle production; the mechanism complies with nucleosynthesis constraint due to relic gravity waves. We obtain a lower bound on the coupling constant [Formula: see text] that governs the interaction of curvaton with matter fields. We study curvaton decay before domination and decay after domination and plot the allowed region in the parameter space in both cases.
A Study on the Prediction of COVID-19 Confirmed Cases Using Deep Learning and AdaBoost-Bi-LSTM Model
Authors: Shin Dong-Ryeol , Chae Gayoung , Park Minjae
Published: September 2023

In this study, AdaBoost-Bi-LSTM ensemble models are developed to predict the number of COVID-19 confirmed cases by effectively learning volatile and unstable data using a nonparametric method. The performance of the developed models in terms of prediction accuracy is compared with those of existing deep learning models such as GRU, LSTM, and Bi-LSTM. The COVID-19 outbreak in 2019 has resulted in a global pandemic with a significant number of deaths worldwide. There have long been ongoing efforts to prevent the spread of infectious diseases, and a number of prediction models have been developed for the number of confirmed cases. However, there are many variables that continuously mutate the virus and therefore affect the number of confirmed cases, which makes it difficult to accurately predict the number of COVID-19 confirmed cases. The goal of this study is to develop a model with a lower error rate and higher predictive accuracy than existing models to more effectively monitor and handle endemic diseases. To this end, this study predicts COVID-19 confirmed cases from April to October 2022 based on the analysis of COVID-19 confirmed cases data from 16 December 2020 to 27 September 2022 using the developed models. As a result, the AdaBoost-Bi-LSTM model shows the best performance, even though the data from the period of high variability in the number of confirmed cases was used for model training. The AdaBoost-Bi-LSTM model achieved improved predictive power and shows an increased performance of 17.41% over the simple GRU/LSTM model and of 15.62% over the Bi-LSTM model.
VIX MODELING FOR A MARKET INSIDER
Authors: HESS MARKUS
Published: September 2023

In this paper, we extend the popular Barndorff–Nielsen–Shephard stochastic volatility model to the case of a pure-jump Ornstein–Uhlenbeck equation with non-vanishing stochastic mean-reversion level. Based on this setup, we derive representations for the squared VIX process and related VIX futures prices. Having these results at hand, we introduce an initially enlarged filtration which models the view of a VIX market insider who has knowledge about the future behavior of the stochastic mean-reversion level of the squared volatility process available. In this enlarged filtration framework, we infer an explicit representation for the anticipative VIX process and obtain the associated time dynamics. We finally investigate the pricing of variance swaps under both backward- and forward-looking information.
Pattern, Source, Destination of Volatilities in Financial Market and Policy Lessons
Authors: Rath Prabhas Kumar
Published: September 2023

This paper studies patterns of volatilities and their spillovers across six major segments of Indian financial market applying univariate GARCH model and estimating the Diebold and Yilmaz (DY) volatility spillover index. The study found increasing integration of financial market segments over time and that equity, bank index and corporate bond segments are net contributors while money, gsec and forex segments are net receivers of volatility. The study highlights the need for a healthy banking sector and the increasing significance of corporate bond market volatility and suggests segment specific policy responses to tackle financial market volatilities.
Safety Criterion for Hollow Pipe Piles Under Blasting Vibration Based on Wave Function Expansion Method
Authors: Wei Haixia , Li Dongbing , Zhu Jie , Chu Huaibao , Cui Youquan
Published: September 2023

When the drilling and blasting method is used to excavate urban subway tunnels, the blasting seismic waves will inevitably produce vibration effects on the pile foundations under the surface buildings, which will seriously threaten the safety of surrounding buildings and the environment. Based on the transmission and reflection laws of stress waves at the interface between soil medium and pile medium and the displacement–stress continuous assumption, the wave function expansion method is used to analyze the whole process mechanism of vibration effect of hollow pipe piles under the action of incident [Formula: see text] waves. In addition, the theoretical model of safety criterion for hollow pipe piles under blasting vibration is proposed and the reliability of the model is verified. Furthermore, the impacts of the elastic modulus, density, and pile section parameters of soil and piles on the safety criterion for the blasting vibration effect of hollow pipe piles are analyzed. The results show that as the elastic modulus and density of the soil increase, the critical peak particle velocity (PPV) curves of hollow pipe piles move to the high-frequency and low-frequency bands, respectively, resulting in a decrease in the overall safety of piles. This indicates that hollow pipe piles should not be buried in soil layers with high elastic modulus and density. It is also shown that the larger the hollow area of hollow pipe piles, the lower their safety. Compared to solid circular piles, hollow pipe piles have a higher overall seismic safety reserve. The study results have guidance and reference value for effectively evaluating and controlling the harm of blasting vibration effects of hollow pipe piles.
Identification of Moving Vehicle Loads Using Instantaneous Vision-Based Vehicle Spatiotemporal Information and Improved Time Domain Method
Authors: Xu Bohao , Chen Yuhan , Yu Ling
Published: September 2023

Accurate identification of moving vehicle loads on bridges is one of the challenging tasks in bridge structural health monitoring, but lacks of intensive investigations to merge the heterogeneous data of vision-based vehicle spatiotemporal information (VVSI) and vehicle-induced bridge responses for moving force identification (MFI) in the existing time domain methods (TDM). In this study, a novel MFI method is proposed by integrating instantaneous VVSI and an improved TDM (iTDM). At first, a novel VVSI method combining background subtraction with template matching is presented to accurately track moving vehicles on bridges. With the calibration technique and camera perspective transformation model, the distribution of vehicles (DOV) on bridges is obtained and used as a priori information in the subsequent MFI. Then, the iTDM is developed based on the MFI equation re-formed in the form of instantaneous VVSI instead of the constant speed vehicle crossing bridges assumed in the traditional TDM. Finally, based on the redundant dictionary matrix composed of Haar functions for a moving load, the MFI problem is converted to explore a solution to the atom vectors and then solved by the Tikhonov regularization method. Experimental verifications in laboratory and a comparative study with the existing three methods are conducted to assess the feasibility of the proposed method. The results show that the proposed MFI method outperforms the existing methods and can effectively identify the moving vehicle loads with a higher and acceptable accuracy. It is successful for the proposed method to replace the assumption of constant speed vehicle crossing bridge in the traditional TDM with the instantaneous VVSI in the MFI problem.
Stationary Stochastic Response Behaviors of FG Plate–Shell Combined Structure in Aero-Thermal Environment
Authors: Gao Xiansong , Zhong Rui , Liu Xinxiang , Wang Qingshan , Xu Hailiang
Published: September 2023

A meshless model is proposed to carry out the free and stationary stochastic vibration analysis of the functionally graded combined rectangular and cylindrical shells (FG-CRCS) structure under the aerodynamic and thermal environment. The FG-CRCS structure contains three combined structure types including rectangular–cylindrical shell (RC-type), cylindrical–rectangular–cylindrical shell (CRC-type), and closed rectangular–semicylindrical shell (CRS-type). The effects of aerodynamic and thermal loads on the dynamic behaviors of the FG-CRCS structure with temperature-dependency of material properties are investigated by introducing the supersonic piston theory and thermo-elastic theory. Furthermore, the pseudo-excitation method (PEM) is adopted to simulate the random loads applied to the FG-CRCS structure. The dynamic equations of the FG-CRCS structure are established in the theoretical frame of the first-order shear deformation theory (FSDT), whose general boundary conditions and coupling relationship are regulated by the artificial springs. Then, the reasonableness of this meshless model to predict free and random vibrations in aerodynamic and thermal environments is verified by comparing it with published literature and FEM results. On this basis, the contribution of essential parameters (including the aerodynamic load, thermal load, and boundary condition) on the free and random vibration behaviors of the FG-CRCS structure is presented, which may serve as guidance for the design of the plate–shell coupled structures in aerospace.
Offshore Triceratops With Elliptical Legs Under Postulated Failure of Tethers
Authors: Srinivasan Chandrasekaran , Shanmukha Rao Ganta
Published: September 2023

Offshore Triceratops are classified as form-dominant structures possessing the novelty of counteracting the lateral loads with material strength and geometric form. The deck is supported by the buoyant legs, which are positioned on the seabed using taut-moored tethers. Ball joints connect the legs with the deck and help partially isolate the deck to remain horizontal under waves and wind. While offshore structures commonly have tubular legs, the current study investigates Triceratops with elliptical legs under the postulated failure of tethers. Detailed dynamic analysis under postulated failure conditions is carried out using ANSYS AQWA, while the LIBRIUM analysis is used to obtain the equilibrium position of the platform under intact and postulated failure conditions. Results show that under postulated failure conditions, the peaks of the power spectral density function of the pitch response are seen closer to its natural frequency and the input wave frequency. Ball joints restrain this rotation from transferring to the deck, conforming to one of the advantages of its existence. The fatigue life of tethers calculated for different load cases under intact and postulated failure conditions helps understand the stability conditions of the platform.
INFLUENCE OF FEMUR LENGTH ON ASYMMETRY OF PROSTHETIC GAIT BIOMECHANICS IN TRANSFEMORAL AMPUTATION
Authors: EZHUMALAI K. , PADHI ARPITA , MOHANTY RAJESH KUMAR , PRADHAN ROJALEEN , MOHANTY PATITAPABAN
Published: September 2023

This study compares the prosthetic gait asymmetry in transfemoral amputees with varied femoral lengths to able-bodied participants in terms of temporal-spatial parameters and joint kinematics. Sixteen young and active transfemoral amputees with short and long residual limbs were divided into two groups and subjected to three-dimensional quantitative motion analysis through high definition optoelectronic cameras and force platform. The prosthetic gait of amputees was compared with those of 15 participants with normal gait to analyze the asymmetry. There was a significant difference in temporal-spatial gait parameters between the amputee groups in terms of intact limb stride length and swing time ([Formula: see text]). The gait of amputees with long femoral lengths was with comparatively higher mean step length (0.31 versus 0.35[Formula: see text]m), velocity (0.48 versus 0.44[Formula: see text]m/s), and cadence (73.58 versus 66.62 steps/min) compared to short residual limbs, however these results are nonsignificant ([Formula: see text]). Amputees and able-bodied participants differed significantly for all measured parameters ([Formula: see text]). The amputees with short residual limbs had more variation in sagittal plane hip flexion at initial contact than long amputees and able-bodied subjects. Amputees with longer residual limbs demonstrated peak swing prosthetic hip flexion closer to able-bodied individuals. The frontal pelvic obliquity and sagittal pelvic tilt revealed more variance among amputees with shorter residual limbs than longer ones. This study will aid in identifying the underlying mechanism of gait asymmetry in transfemoral amputees in relation to residual femoral length and hence will pave a path for improving the knee and foot prosthetic components.
Convergence analysis of deep residual networks
Authors: Huang Wentao , Zhang Haizhang
Published: September 2023

Various powerful deep neural network architectures have made great contributions to the exciting successes of deep learning in the past two decades. Among them, deep Residual Networks (ResNets) are of particular importance because they demonstrated great usefulness in computer vision by winning the first place in many deep learning competitions. Also, ResNets are the first class of neural networks in the development history of deep learning that are really deep. It is of mathematical interest and practical meaning to understand the convergence of deep ResNets. We aim at studying the convergence of deep ResNets as the depth tends to infinity in terms of the parameters of the networks. Toward this purpose, we first give a matrix–vector description of general deep neural networks with shortcut connections and formulate an explicit expression for the networks by using the notion of activation matrices. The convergence is then reduced to the convergence of two series involving infinite products of non-square matrices. By studying the two series, we establish a sufficient condition for pointwise convergence of ResNets. We also conduct experiments on benchmark machine learning data to illustrate the potential usefulness of the results.
Fractional Fourier transform associated with polar coordinates
Authors: Sun Yan-Nan , Gao Wen-Biao
Published: September 2023

The fractional Fourier transform (FRFT) is a generalized form of the Fourier transform (FT), it is another important class of time–frequency analysis tool in signal processing. In this paper, we study the two-dimensional (2D) FRFT in the polar coordinates setting. First, Parseval theorem of the 2D FRFT in the polar coordinates is obtained. Then, according to the relationship between 2D FRFT and fractional Hankel transform (FRHT), the convolution theorem for the 2D FRFT in polar coordinates is obtained. It shows that the FRFT of the convolution of two functions is the product of their respective FRFTs. Moreover, the fast algorithm for the convolution theorem of the 2D FRFT is discussed. Finally, the sampling theorem for signal is explored.
AAindex-PPII: Predicting polyproline type II helix structure based on amino acid indexes with an improved BiGRU-TextCNN model
Authors: He Jiasheng , Zhang Shun , Fang Chun
Published: September 2023

The polyproline-II (PPII) structure domain is crucial in organisms’ signal transduction, transcription, cell metabolism, and immune response. It is also a critical structural domain for specific vital disease-associated proteins. Recognizing PPII is essential for understanding protein structure and function. To accurately predict PPII in proteins, we propose a novel method, AAindex-PPII, which only adopts amino acid index to characterize protein sequences and uses a Bidirectional Gated Recurrent Unit (BiGRU)-Improved TextCNN composite deep learning model to predict PPII in proteins. Experimental results show that, when tested on the same datasets, our method outperforms the state-of-the-art BERT-PPII method, achieving an AUC value of 0.845 on the strict data and an AUC value of 0.813 on the non-strict data, which is 0.024 and 0.03 higher than that of the BERT-PPII method. This study demonstrates that our proposed method is simple and efficient for PPII prediction without using pre-trained large models or complex features such as position-specific scoring matrices.
Application and Improvement of MFCC in Gesture Recognition with Surface Electromyography
Authors: Zhu Shiwei , Wang Daomiao , Hu Qihan , Wu Hong , Fang Fanfu , Wang Yixi , Yang Cuiwei
Published: September 2023

As a physiological signal reflecting the state of muscle activation, surface electromyography (sEMG) plays a vital role in the assessment of neuromuscular health, human–computer interaction, and gait analysis. Inspired by the audio signal analysis outcome that features extracted with Mel Frequency Cepstral Coefficient (MFCC) empower better representation, this paper proposes a comparative study of a gesture recognition method by using and improving with the MFCC features of sEMG. Comparing and combining with the conventional time-domain and frequency-domain features, different learning-based techniques are deployed to evaluate the performance of the proposed approach on the NinaPro datasets. The proposed approach was evaluated on the NinaPro-DB1 and NinaPro-DB2 datasets, achieving the improvements of 3.42% and 3.67%, respectively, in terms of the highest accuracy using the standard MFCC method. Correspondingly, when combined with the improved MFCC, the accuracy was further increased, reaching the maximum values of 89.82% and 87.82%, respectively, on the two datasets. The impact on the performance reveals the effectiveness of MFCC, and the results show that the proposed method has the potential to realize high-precision gesture recognition.
Accurate Perception and Association of Objects for Humanoid Robots Under Dynamic Visual SLAM
Authors: Chen Kaiqi , Liu Jialing , Tong Qiyi , Cheng Xu , Zhang Jianhua
Published: September 2023

Humanoid robots still have a low-level perception of their surroundings, which is a formidable obstacle to performing complex tasks. To improve their perceptual capabilities, high-level semantic information can be incorporated into their perceptual framework so that they can gain the ability to infer and understand their environment accurately. Among the various techniques available, semantic Simultaneous Localization and Mapping (SLAM) becomes a promising avenue for achieving this perception enhancement. While semantic SLAM can enhance a robot’s ability to perform tasks, the accurate perception, and association of semantic objects in complex and dynamic environments remain challenging. Hence, the need arises for a solution that swiftly and precisely associates object measurements with landmarks, considering their motion properties, and promptly rectifies erroneous associations in real time. To this end, we propose a semantic perception approach designed explicitly for dynamic environments, adept at distinguishing between dynamic and static objects. Furthermore, we propose two association strategies: dynamic object association based on semantic map points and static object association based on object pose information. And as the number of object measurements associated with the landmarks increases, we perform the association validation algorithm to verify the association for the landmark to improve the accuracy of the association. The proposed method is extensively evaluated on both simulated indoor sequences obtained from humanoid robot viewpoints and the KITTI dataset. Experimental results show that our approach significantly improves the robustness and accuracy of object association and trajectory estimation.
Observational constraints on parameterized deceleration parameter with f(Q,T) gravity
Authors: Shekh S. H. , Caliskan Aylin , Mustafa G. , Maurya S. K. , Pradhan Anirudh , Güdekli Ertan
Published: September 2023

In the current analysis, we considered a spatially flat FRW universe with [Formula: see text] gravity. To understand the dark energy via the equation of state, we start with the phenomenological parametrization of the deceleration parameter [Formula: see text]. One of the most preferred parametrizations of the dark energy equation of state served as the idea for the deceleration parameter. The best-fit value of [Formula: see text] (the redshift at which the universe transitions from before decelerating to the present accelerating phase) and the current value of the deceleration parameter are explored. The negative behavior indicates that the universe is accelerating, which can be verified from the combined datasets (CC + SC + unCor BAO). Additionally, we examine the current scenario of the well-reconstructed [Formula: see text] and [Formula: see text] fitting behavior via [Formula: see text]CDM. As we are working within [Formula: see text] gravity, so, two specific models like [Formula: see text] and [Formula: see text] with [Formula: see text], [Formula: see text], [Formula: see text] model parameters are considered to complete the current analysis. Last, we have concluding remarks regarding the current analysis.
Lie symmetry analysis and optimal system for shock wave in a self-gravitating rotating ideal gas under the effect of magnetic field and monochromatic radiation
Authors: Nath G. , Kadam V. S.
Published: September 2023

The lie group invariance method is used to study a cylindrical shock wave in a self-gravitating, rotating perfect gas in the presence of monochromatic radiation and an azimuthal or axial magnetic field. The density of the ambient medium is taken as variable according as the law of shock path. For the system of equations of motion, the one-dimensional optimal system of subalgebra is determined by using Lie group analysis. We have utilized optimal classes of infinitesimal generators to acquire the flow variable transformation and the similarity variable, which are important prerequisites for obtaining the system of ordinary differential equations from the system of partial differential equations. In detail, we have numerically solved and discussed the results in two cases: with power and exponential laws shock path. The effects of variation of the rotational parameter, gravitational parameter, Alfvén Mach number, adiabatic exponent, and dimensionless parameter that characterize the interaction between incident radiation flux and gas are studied in depth. A comparative study is done between power law and exponential law in respect of the strength of shock wave and the flow variables distribution in the flow-field region behind the shock front. The shock is stronger with an axial magnetic field in a power law case; whereas shock is stronger with an azimuthal magnetic field in an exponential law case. The shock strength is observed to decline when the adiabatic index of the gas or the Alfvén Mach number increases. The shock decay with rotational parameter in case of exponential law, but it strength enhanced in case of power law. Also, the rotational parameter and gravitational parameter have an exact opposite impact on the strength of shock in power law and exponential law cases.
Anomaly cancellation in string theory
Authors: Davis Simon
Published: September 2023

The anomaly cancellation in superstring theory is known to hold at leading order in the curvature for the gauge groups [Formula: see text] and [Formula: see text]. The coefficients of the next-to-leading order terms may be evaluated, and a mechanism for cancellation is described, which would remain valid at higher genus when there exists a global splitting of the coordinates of supermoduli space. Since the spin-[Formula: see text] fields transform under the adjoint representation in these models, compactification of the heterotic string over [Formula: see text] or a fundamental 12-dimensional theory, from which superstrings are produced through an elliptic fibration, over [Formula: see text], provides another phenomenologically viable theory at lower energies compatible with the standard description of the elementary particle interactions. The 96 spin-[Formula: see text] fields now would transform under the fundamental representation of [Formula: see text] and the spin-one gauge fields would belong to the adjoint representation. The sum of the anomaly polynomials for the particle content of the [Formula: see text] model vanishes at [Formula: see text]. The contributions to the gravitational anomaly from the particles and antiparticles cancel by the CPT theorem and the duality transformations of polynomials of degree 6 in the curvature and the field strength. The existence of the interaction of a spin-2 charge, which is conserved only over a finite time interval, can be traced to nonlocal terms in the reduction of the string field theory to the gravitational sector. The source of the global gravitational anomaly cancellation in the modular form equations derived from an elliptic fibration of a 12-dimensional theory would restrict the compactifications and provide a method for preserving the absence of anomalies in four dimensions.
A Note on Callability of Convertible Bonds
Authors: Zhu Song-Ping , Ai Lin
Published: September 2023

The Convertible Bonds (CBs) market has witnessed an unprecedented level of activity over the last few years not only in developed countries such as the United States but also in BRICK countries such as China. Exploring new properties of CBs or CBs with clauses becomes important for academia communities in financial mathematics. In this paper, we build two coupled partial differential equations (PDEs) for pricing a callable CB, and find a newly identified inherent property of this bond. The new property is that the conversion ratio will not affect the critical recall time indicating the time beyond the callability. Besides this property, we also find that solving the critical recall time separately and superimposing later using a non-callable CB is the same as the method of a hybrid free boundary (the critical recall time) and a moving boundary (the optimal conversion price) though the callability and the American-style conversion are nonlinearly coupled.