Mode Structure Research Articles

Конвективные режимы псевдопластической жидкости в квадратной полости при воздействии высокочастотных вибраций в условиях пониженной гравитации

In this paper, we investigate convective modes of pseudoplastic fluid in a square cavity with solid perfectly heat-conducting boundaries under reduced gravity. The cavity performs vertical linearly polarized high-frequency vibrations. Between the vertical walls of the cavity a temperature drop is prescribed in the direction perpendicular to vibrations and the field of gravity. The fluid rheology is described using the Williamson model. The problem is solved based on the averaged thermovibration convection equations for nonlinear viscous fluids. The vibration intensity is determined by the vibration parameter V, which is proportional to the ratio of the amplitude of the vibration acceleration to the free-fall acceleration and does not depend on the temperature difference. The problem is found to have two types of solutions, which we call Newtonian and non-Newtonian modes. These solutions correspond to different convective structures, for which the dependences of the maximum of the stream function and the Nusselt number on the Grashof number are derived. We use these dependences for determining at different values of rheological parameters the threshold values of the Grasgof numbers, corresponding to the change in the modes of stationary averaged convection and the critical Grasgof numbers, corresponding to the loss of stability of stationary averaged flow and the occurrence of oscillatory modes of averaged convection. The structures of different modes of averaged stationary and oscillatory convection are studied. The results obtained for the Newtonian mode have shown that at small values of the Grasgoff number, a slow one-vortex stationary convective flow is realized in the cavity. With increasing the Grasgoff number it transforms into a three-vortex flow. A further increase in the Grasgoff number results in the appearance of a four-vortex convective flow, which eventually transforms again into a three-vortex motion. At even greater Gr, the stationary averaged motion becomes unstable and the oscillatory modes appear in the cavity. For the non-Newtonian mode, a stationary convective flow is the basic flow pattern detected in the cavity; the oscillatory modes are not observed in the whole investigated range of the Grasgoff numbers.

Cushioning performance of origami negative poisson's ratio honeycomb steel structure

The honeycomb structure with a negative Poisson's ratio, inspired by the Miura origami unit, exhibits three-dimensional negative Poisson's ratio characteristics and effective energy dissipation performance. This unique property provides significant potential in the field of protection applications. This study aims to comprehensively understand the impact of auxetic and origami structures on the cushioning performance of honeycomb structures. For this purpose, 316 L stainless steel specimens were fabricated using 3D printing technology and subjected to drop hammer impact tests, and the results were verified by finite element simulation. This paper focuses on assessing the deformation mode and energy dissipation performance of origami auxetic honeycomb structures with varying width-to-thickness ratios and folding angles under different impact energy levels. The results indicate that the negative Poisson's ratio origami specimens exhibit higher plateau stress and specific energy absorption compared to their positive and zero Poisson's ratio origami counterparts with the same geometry. In addition, a smaller width-to-thickness ratio and higher input impact energy enhance the cushioning performance of honeycomb structures.

Spherical nucleic acids for biomedical applications

Spherical nucleic acids (SNAs) are a 3D spherical nanostructure composed of highly oriented, dense layers of oligonucleotides conjugated to a hollow or solid core. This structure allows SNAs to show resistance to nuclease degradation, enter into nearly all cells without transfection agents and enable precise interactions with target molecules. Based on superior biological properties, SNAs can be tailored for diverse biological applications, rendering them a flexible and biosafe tool for biological applications as well as an enabling platform for therapy. In this review, we mainly discuss the structure and conjugation mode of SNAs and focus on recent advances in their applications, such as biomedical detection, imaging, and drug delivery. Finally, the remaining challenges and future directions of SNAs are also discussed and proposed.

Digital morphology network for effective teaching of cytology, histology and histopathology for medical and biology curriculum. VM3.0 Erasmus+ project.

Digital microscopy transformation, the basis for the virtual microscopy applications, is a challenge but also a requirement in modern Medical Education. This paper presents the scope, background, methods, and results of the project "Digital Transformation of Histology and Histopathology by Virtual Microscopy (VM) for an Innovative Medical School Curriculum", VM3.0, funded by the European Union under the Erasmus+ framework (ref.no.2022-1- RO01-KA220-HED-000089017). The project was initiated at Grigore T. Popa University of Medicine and Pharmacy, Iași, Romania, with the support of Euroed Foundation, Iași, and cooperation of University partners from Gdansk (Poland), Plovdiv (Bulgaria), Alicante (Spain), and Patras (Greece) aimed to implement digital histology and histopathology teaching in a common network. The backbone of the project was the development of a Digital Slide Platform based on the scans of histological slides collected from all the partners of the participating universities and the creation of a simple and fast digital/internet communication tool that could be used to improve histology and histopathology teaching of medical and natural sciences students. The construction of a Virtual Microscopy Library (VML) has been based on the acquisition of whole scans of high-quality histological slides stained by hematoxylin and eosin (H&E) and other classical staining methods and description of various organs' details in English as well as respective languages of the project's partners. The VML can be used for different approches, both for students' instruction in classes as well as for individual students' work and self-testing. Universities from other countries could use the modal structure of the developed VML system on the condition that more slides are provided and the implementation of national language(s) is implemented. The combined efforts of all university partners allowed to establish the dynamic low-cost virtual microscopy educational system. The VM system could help unify the standards of cytology, histology, and histopathology teaching in a quest for the digital transformation of the European educational system.

Verification and validation of electrostatic turbulence simulation for numerical Lie transform code

Abstract This paper reports the verification and validation of a new gyrokinetic (GK) code, numerical Lie transform (NLT), for electrostatic turbulence simulation in tokamak plasmas. Based on the standard cyclone base case (CBC), NLT has been verified against two typical GK codes, GK toroidal code (GTC) and GK numerical experiment of tokamak, by simulating the ion temperature gradient mode and trapped electron mode. The linear dispersion relation and mode structure agree well among all these codes. In nonlinear simulation, the time evolution of ion heat diffusivity obtained from NLT is consistent with the GTC results. Furthermore, utilizing experimental equilibria with obvious turbulence features from HL-2A shot #22388, the validation of NLT for real tokamak simulation has been carried out. The profiles of ion turbulent thermal diffusivity calculated by NLT match well with experimental results.

Post-buckling behavior and DSM design of cold-formed steel lipped channel columns experiencing local-distortional-global interaction

This paper describes experimental research investigating the structural behaviors, failure modes, and ultimate load-carrying capacities of fixed-ended cold-formed steel lipped channel columns eroded by local-distortional-global (L-D-G) buckling interaction under axial compression. Initially, a brief introduction on the selection of column geometry, which was based on the closeness between three elastic critical buckling stresses named elastic local, distortional, and global critical buckling stresses, was reported. In addition, detailed works involving measuring member geometries and initial geometrical imperfections, test set-up, and the arrangements of strain gauges and displacement transducers are described. Moreover, experimental investigation results of 33 cold-formed steel columns are discussed including deformed configurations, applied load vs. strains curves, applied load vs. displacement curves, failure modes, and ultimate load-carrying capacities. The tests demonstrated D-G interaction with no obvious local deformation observed even though the elastic critical loads of L, D, and G for the selected specimens are close. The results clearly demonstrate that the occurrence of D-G buckling interaction eroded the ultimate strengths of columns. Current DSM predictions are evaluated using experimental data of cold-formed steel columns related to the D-G buckling interaction. Furthermore, a design criterion based on DSM is proposed to identify cold-formed steel columns eroded by D-G buckling interaction and predict the ultimate strength, which is evaluated by all available experimental data collected from related literature.

Al nanowire-embedded silicon for broadband optical modulation: Forming mechanism and optical performance

In recent decades, silicon has been widely used in light regulation devices, owing to its wideband high refractive index and low dispersion. To meet the increasing demands for various applications, optical modulation techniques appear of great potential to enhance the optical performance of Si-based devices. However, challenges still remain in achieving precise control over the band structure and resonance modes without introducing complex artificial structures. In this study, a composite film composed of silicon embedded with high fraction aluminum nanowires was developed by magnetron sputtering. It was revealed that the formation of aluminum nanowires was attributed to the spontaneous phase separation between silicon and aluminum, which was strongly dependent on the filling fraction and surface diffusion length of the aluminum during the co-sputtering process. The composite microstructure was precisely regulated by manipulating adatom diffusion and reevaporation through ion bombardment, thereby modifying its broadband optical properties. Moreover, exceptional electromagnetic properties were achieved by incorporating aluminum nanowires into silicon, as evidenced by the metallic behaviors in the short-wavelength regime and dielectric properties in the infrared spectrum range.

Improving Robotic Milling Performance through Active Damping of Low-Frequency Structural Modes

Industrial robots are increasingly prevalent due to their large workspace and cost-effectiveness. However, their limited static and dynamic stiffness can lead to issues like mode coupling chatter and regenerative chatter in robotic milling processes, even at shallow cutting depths. These problems significantly impact performance, product quality, tool longevity, and can damage robot components. An active inertial actuator was deployed at the milling spindle to enhance dynamic stiffness and suppress low-frequency vibrations effectively. It was identified that the characteristics of the actuator change with its mounting orientation, a common scenario in robotic machining processes. This variation has not been reported in the literature. Our study includes the identification of model parameters for the actuator in both horizontal and vertical mountings. Additionally, the novelty of the present work lies in the specific design and implementation of compensation filters tailored for the active inertial actuator in both horizontal and vertical configurations. These filters address the unique challenges posed by low-frequency vibrations in robotic milling, offering significant improvements in dynamic stiffness and vibration suppression. Traditional model-based compensators were effective for vertical mounting, while pole-zero placement techniques with minimum phase systems were optimal for horizontal mounting. These compensators significantly enhanced dynamic stiffness, reducing maximum low-frequency robot structural modes by approximately 100% in horizontal mounting and approximately 214% in the vertical configuration of the actuator. This advancement promises to enhance industrial robot capabilities across diverse machining applications.

The luminescent Nb2C MXene nanosheet-based whispering gallery mode-enhanced ECL strategy for miRNA-214 detection

MiRNA-214 can regulate the expression of their downstream target genes after post-transcriptional and are involved in the biological processes of triple negative breast cancer (TNBC). In this work, the small-sized luminescent Nb2C nanosheet-based whispering gallery mode-enhanced electrochemiluminescence (ECL) strategy was successfully constructed to detect miRNA-214 in TNBC. Firstly, we have synthesized small-sized luminescent Nb2C nanosheets from Nb2AlC MXene. The Nb2C nanosheets not only exhibited more stable chemical properties and reduced the defects of the large sheet structures, but also possessed the quantum confinement effect with the discrete energy level. As a result, the prepared small-sized Nb2C nanosheets had unique luminescent and electrochemical properties. Furthermore, in order to improve the ECL performance of Nb2C nanosheets, SiO2 microspheres were self-assembled on the electrode surface by gas-liquid interface method to form whispering gallery mode structure. Because the light was continuously reflected at the interface of the microcavity in the whispering gallery mode, the ECL signal of Nb2C luminescent nanosheets was amplified largely. Finally, the whispering gallery mode-based ECL sensing platform was established. The results showed that the biosensor had a good linear correlation between the ECL intensity and the logarithm of concentration of miRNA-214 in the range of 10 fM to 100 nM with a limit of detection of 2.5 fM. The actual detection of miRNA-214 content in clinical TNBC tissue samples was realized successfully.

Effect of molecular crowders on ligand binding kinetics with G-quadruplex DNA probed by fluorescence correlation spectroscopy

Guanine-rich single-stranded DNA folds into G-quadruplex DNA (GqDNA) structures, which play crucial roles in various biological processes. These structures are also promising targets for ligands, potentially inducing antitumor effects. While thermodynamic parameters of ligand/DNA interactions are well-studied, the kinetics of ligand interaction with GqDNA, particularly in cell-like crowded environments, remain less explored. In this study, we investigate the impact of molecular crowding agents (glucose, sucrose, and ficoll 70) at physiologically relevant concentrations (20% w/v) on the association and dissociation rates of the benzophenoxazine-core based ligand, cresyl violet (CV), with human telomeric antiparallel-GqDNA. We utilized fluorescence correlation spectroscopy (FCS) along with other techniques. Our findings reveal that crowding agents decrease the binding affinity of CV to GqDNA, with the most significant effect—a nearly three-fold decrease—observed with ficoll 70. FCS measurements indicate that this decrease is primarily due to a viscosity-induced slowdown of ligand association in the crowded environment. Interestingly, dissociation rates remain largely unaffected by smaller crowders, with only small effect observed in presence of ficoll 70 due to direct but weak interaction between the ligand and ficoll. These results along with previously reported data provide valuable insights into ligand/GqDNA interactions in cellular contexts, suggesting a conserved mechanism of saccharide crowder influence, regardless of variations in GqDNA structure and ligand binding mode. This underscores the importance of considering crowding effects in the design and development of GqDNA-targeted drugs for potential cancer treatment.

Time-Varying Aeroelastic Modeling and Analysis for a Morphing Wing

The paper presents a novel time-varying aeroelastic modeling approach for the morphing wing with the process of camber changing. The time-varying modeling methodology includes structural dynamics modeling, unsteady aerodynamic modeling, and interpolation for fluid–structure coupling. Firstly, the morphing wing is modularized and divided into fixed and variable parts by the floating frame of reference formulation. It is combined with the Craig–Bampton method to reduce order and eliminate nonindependent degrees of freedom. Then, the unsteady vortex-lattice method is used to calculate the transient, unsteady aerodynamic force for time evolution. Furthermore, the above time-varying structural dynamics modeling and a fluid–structure coupling interpolation are integrated to construct overall aeroelastic modeling, obtaining a set of differential-algebraic equations. Finally, these equations are numerically solved by the generalized-α method. The proposed approach provides an innovative idea to deal with the incredible complexity of the aeroelastic effect as structural characteristics change over time. It can efficiently and accurately analyze the morphing wing’s transient response or flutter property. To verify and utilize the time-varying aeroelastic modeling approach, numerical calculations and comparative studies were carried out regarding the time-varying characteristics of the structural modes, aerodynamic calculations, and flutter prediction of the morphing wing.

Ultra-precise, sub-picometer tunable free spectral range in a parabolic microresonator induced by optical fiber bending.

Surface nanoscale axial photonic (SNAP) microresonators are fabricated on silica optical fibers, leveraging silica's outstanding material and mechanical properties. These properties allow for precise control over the microresonators' dimension, shape, and mode structure, a key feature for reconfigurable photonic circuits. Such circuits find applications in high-speed communications, optical computing, and optical frequency combs (OFCs). However, consistently producing SNAP microresonators with equally spaced eigenmodes has remained challenging. In this study, we introduce a method to induce a SNAP microresonator with a parabolic profile. We accomplish this by bending a silica optical fiber in a controlled manner using two linear stages. This approach achieves a uniform free spectral range (FSR) as narrow as 1 pm across more than 45 modes. We further demonstrate that the FSR of the SNAP microresonator can be continuously adjusted over a range nearly as wide as one FSR itself, specifically from 1.09 to 1.72 pm, with a precision of ±0.01 pm and high repeatability. Given its compact size and tuning capability, this SNAP microresonator is highly promising for various applications, including the generation of tunable low-repetition-rate OFC and delay lines.

Investigation of seismic resistant structures with various moment-resisting frame systems and pushover analysis

Earthquakes are a serious threat in the construction of multi-storey buildings in Indonesia, which are divided into several seismic design categories. The design of seismic-resistant buildings requires the management of plastic hinges to reduce seismic loads. The aspects of seismic-resistant structural design in Indonesia are regulated by SNI 1726:2019, SNI 1727:2020, and SNI 2847:2019. Intermediate Moment Resisting Frame System (IMRFS) and Special Moment Resisting Frame System (SMRFS) are used based on seismic category and earthquake intensity. Pushover analysis is used to analyze the structures behavior when exposed to seismic loads. This research designs seismic resistant structures with IMRFS and SMRFS at different locations with the aim of assessing structural performance and gaining reinforcement to the concrete ratio, which is relevant for the design and construction of multi-storey buildings in Indonesia. The results of this research are the structural performance levels, reinforcement volume, concrete volume, and the reinforcement to concrete volume ratio. Both IMRFS and SMRFS reached Immediate Occupancy to Life Safe performance levels after the earthquake because their monitored displacement was not significantly different. The structural failure modes of both systems meet the Strong Column–Weak Beam requirements. The distribution of plastic hinges also remains in the Immediate Occupancy category.

Assessment of Thermal and Mechanical Indices as Acoustic Output Parameters Used in Obstetric Ultrasound in Saudi Arabia.

Patient safety is paramount in ultrasound procedures, particularly in obstetric ultrasounds involving both the mother and fetus. The thermal and mechanical indices (TI and MI) serve as crucial indicators of the acoustic output during ultrasound. Clinicians and specialists must know these indices and ensure they are within safe ranges. This study aimed to assess the parameters of acoustic output power employed in obstetric ultrasound (thermal and mechanical index). A cross-sectional observational study conducted at Maternity and Children's Hospital in Al-Madina Al-Munawwarah, the data was collected from obstetric scanning of 411 pregnant females using a data collection sheet including gravida and women's age, gestational age, scan mode, scan time, and thermal and mechanical index (TI and MI) values. The study found that there were significant differences in safety indices measurement between different modes; in Pulsed Doppler, mean Thermal Index Bone (TIb) had the highest value (1.60±0.40), and the Mechanical Index (MI) was the lowest (0.68±0.33). There were insignificant differences in safety indices values in different modes in different trimesters. The thermal indices of soft tissue and bony structure (TIs and TIb) of brightness mode (B-mode) were constant in all trimesters, but the MI in the first trimester was lower than in the other trimesters. This study found significant differences in TIs, TIb, and MI in different modes of obstetric ultrasound. Pulsed Doppler ultrasonography had the highest TIb value and a lower MI value. The ultrasound acoustic exposure output parameters were within the standard's recommended limit.

Interdecadal variability of winter and spring Eurasian snow depth and its impact on Eastern China precipitation

Empirical orthogonal function (EOF) and correlation analyses were employed to investigate the winter and spring snow depth in Eurasia and its relationship with Eastern China precipitation based on the observed and reanalyzed data from 1980 to 2016. The results show that the winter and spring snow cover in Eurasia not only highlights a decreasing trend due to global warming (the first EOF mode, its variance accounted for 24.4% and 22.6% of the total variance) but also exhibits notable interdecadal variation (the second EOF mode, its variance accounted for 10.2% and 11.5% of the total variance). The second EOF mode of winter snow depth in Eurasia is characterized by a west-east dipole pattern. It was observed that the spatial correlation pattern between the EOF2 of Eurasian snow depth and summer precipitation in China closely resembles the meridional quadrupole structure of the third EOF mode of summer precipitation in China. This pattern is characterized by excessive rainfall in Northeast China and the lower-middle reaches of the Yangtze River, and less rainfall over the Yellow River basin and southern China. The EOF mode of spring snow depth not only reflects the declining trend but also regulates precipitation in Eastern China. The possible mechanisms by which snow depth causes changes in soil moisture and subsequently affects atmospheric circulation are then explored from the perspective of the hydrological effects of snow cover. Decreased (Increased) snow depth in Eurasia during the winter and spring directly leads to diminished (increased) soil moisture while increasing (decreasing) net radiation and sensible heat flux at the surface. The meridional distribution of surface temperature also exhibits a dipole pattern, leading to enhanced subtropical westerly jet in the upper troposphere. The Eurasian snow cover anomalies pattern triggered an anomalous mid-latitude Eurasian wave train, which strengthened significantly in the Western Siberian Plain. It then splits into two branches, one continuing to propagate eastward at high latitudes and the other shifting towards East Asia, thereby impacting precipitation in Eastern China. This work indicates that the second EOF mode of Eurasian snow cover can impact the precipitation variability in Eastern China during the same period and in summer on an interdecadal scale.

Unveiling Coupled Dark Plasmon Modes in CdO Structures

Unveiling Coupled Dark Plasmon Modes in CdO Structures

Bridge damage identification based on synchronous statistical moment theory of vehicle–bridge interaction

AbstractConsidering the weak noise resistance and low identification efficiency of traditional bridge damage identification methods, a data‐driven approach based on synchronous statistical moment theory and vehicle–bridge interaction vibration theory is proposed. This method involves two main steps. First, a two‐axle test vehicle is used to collect acceleration response signals synchronously from adjacent designated measurement points while stationary. This operation is repeated to calculate the second‐order statistical moment curvature (SOSMC) difference of entire bridge points corresponding signals in different states. By comparing with the reference value, the preliminary damage location of the bridge can be obtained. Second, the first‐order modal shape curve is constructed using the second‐order statistical moment (SOSM). The refined identification of bridge damage is then based on an improved direct stiffness back calculation of the bridge's stiffness. This article proposes the synchronization theory for the first time and combines it with the statistical moment clustering method, forming an innovative approach to obtaining structural vibration modes. The effectiveness of this method has been well validated through numerical simulations with different parameters and on‐site bridge tests. The research results indicate that SOSMC indicators have better noise resistance and higher recognition efficiency in identifying damage locations, compared to modal curvature and flexibility curvature indicators. Additionally, compared to transfer rate and random subspace methods, the SOSM method results in smaller error and higher identification efficiency.

An Investigation of the Energy-Absorption Characteristics of Thin-Walled Polymer Composite C-Channels: Experiment and Stacked Shell Simulation.

Polymer composite materials are increasingly used in civil aircraft structures. The failure mode and energy-absorption characteristics of polymer composite structures have garnered significant attention from academia and industry. For thin-walled polymer composite C-channels with layups of [0/90]3s, [45/-45]3s, and [45/90/-45/0]3, low-speed axial compression tests were performed to investigate the failure modes, failure mechanisms, and energy-absorbing characteristics. After parametric studies using [0] and [90] single-element models, stacked shell models of thin-walled composite C-channels were established using the Lavadèze single-layer damage constitutive model, Puck 2000, and Yamada Sun failure criteria. The results show that these thin-walled composite C-channels exhibit a stable progressive crushing process with a local buckling failure mode, encompassing local buckling, fiber break-age, matrix cracks, delamination, and corner cracking. The stacked shell model demonstrates reasonable agreement with the progressive crushing process of thin-walled composites, accurately capturing interlayer matrix failure and interface delamination cracking behavior. A comparison of the specific energy absorption (SEA) and mean crushing force (Fmean) between the simulation and test results yields a difference of less than 6%, indicating a strong correlation between the simulation results and the experimental energy-absorbing characteristics. It also shows that a deep understanding of the parameters is helpful for accurate numerical modeling.

Orientation-dependent tribological behavior of the graphite–diamond composite

Coherent interfacial graphite–diamond composite (Gradia) is superhard and conductive, promisingly applied as electric contact material. In this work, large-scale atomistic simulations were performed to investigate its tribological behavior. Depending on the orientation between graphite–diamond interface and loading direction, three structural evolution modes were observed under compression, featuring Gradia to diamond, Gradia to graphite, and Gradia to defective carbon. Coefficient of friction and wear rate were found orientation-dependent. Orientations of graphite-, diamond-, and defective-preferred structural evolution showed different performance. A satisfied balance between tribological performance and conductivity (rich of sp2-carbon) is obtained in the defective-preferred orientation. These results demonstrate the great potential for Gradia using in dynamic electrical contact and provide a theoretical basis for further material design.

Securities Quantitative Trading Strategy Based on Deep Learning of Industrial Internet of Things

By combing the shortcomings of the current quantitative securities trading, a new deep reinforcement learning modeling method is proposed to improve the abstraction of state, action and reward function; on the basis of the traditional DQN algorithm, a deep reinforcement learning algorithm model of RB_DRL is proposed. By improving the network structure and connection mode, and redefining the loss function of the network, the improved model performs well in many groups of comparative experiments. A securities quantitative trading system based on deep reinforcement learning is designed, which organically combines models, strategies and data, visually displays the information to users in the form of web pages to facilitate users' use and seeks the trading rules of the financial market to provide investors with a more stable trading strategy. The research results have important practical value and research significance in the field of financial investment.