Kinematic Research Articles

Effect of the connection structure of zirconia dental implants on biomechanical properties

The connection structure of zirconia dental implants significantly influences their biomechanical behavior and plays a crucial role in the overall service performance of the implant system. This study aims to compare the stress distribution of zirconia implants featuring various internal connection structures under different working conditions. Four distinct types of connection structures were designed for zirconia dental implants: triangular, quadrilateral, hexagonal, and hexalobular plus connections. Additionally, the finite element method was employed to analyze these structures under three working conditions: a static load test model, a bone level model, and a torsion model. Results indicated that in the static load test model, the hexagonal structure experienced the highest stress value at 1284.9 MPa due to its thin neck wall, whereas the hexalobular plus connected implant exhibited the lowest stress value at 1252.9 MPa. In the bone level model, the triangular connection structure demonstrated poor stress distribution for cortical bone and cancellous bone at 69.606 MPa and 7.8191 MPa, respectively. Conversely, the hexalobular plus connection yielded superior stress results for cortical bone and cancellous bone, with values of 66.24 MPa and 5.1327 MPa, respectively. In the torsion model, the hexalobular plus-connected implant exhibits the highest stress value at 237.6 MPa, while maintaining the smallest force transmission angle. Therefore, given that the abutment necessitates a greater range of installation angles and improved torque transmission, the hexalobular plus connection structure may represent the optimal choice.

Utilizing an aspheric lens and compound ellipsoidal cavity for a laser uniform illumination system

To achieve uniform laser illumination of an active imaging system with a small aperture diameter and large field angle, we have developed what we believe to be a novel structure for achieving uniform beam shaping that integrates a laser source, an aspheric lens, and a composite ellipsoidal cavity to enable active laser illumination. Through an aspheric lens, the fundamental mode Gaussian beam is transformed into double Gaussian and flat-top radiation at the target plane. The double Gaussian radiation is further reflected by a complex ellipsoidal cavity, where it is evenly distributed into equal radiation flux. This flux combines with the flat-top radiation, resulting in a uniform distribution at the target plane. The parameters of the complex ellipsoidal cavity are determined using an equalization algorithm. After combining the transmission for flat-top shaping by the aspheric lens and secondary reflection shaping by the composite ellipsoidal cavity, we achieved an aperture measuring 29.7 mm with an aperture angle of 84.0°, at a distance of 2 m from the target plane, with a diameter of 3.6 m, resulting in uniformity reaching 92.7%. RMS and MT/R determine the effectiveness of the compound ellipsoidal cavity design, depending on the maximum reflection angle and transmission angle. MT/R is inversely proportional to the maximum reflection angle, while RMS is directly proportional to the transmission angle. By setting the maximum reflection angle to 32.0° and the transmission angle to 8.0°, we were able to achieve a minimum root-mean-square focusing radius of 108.6 µm along with a minimum effective MT/R ratio of 1.07. The overlap degree between transmission and reflection directly impacts the target plane’s uniformity, adjusted through a defined adjustment factor. Optimizing this factor to 0.9 maximizes the uniformity of the target plane.

Small grazing angle reflection and the sound siphon effect over a low velocity layer of sediments.

The low-order normal modes with small grazing angles (SGA) often control long-range sound field characteristics in shallow water. The SGA reflection loss from a half-space low-velocity bottom (LVB) is independent of the sound attenuation, except around the angle of complete transmission; the SGA bottom reflection loss (BRL) from a seafloor with a top low-velocity layer is very insensitive to the LVB attenuation also, except around a few selected frequencies. Thus, the "seafloor velocity-attenuation coupling" problem will be more fatal for LVB geo-acoustic inversions. The dispersion equation of the normal modes in the LVB layer is coincidentally the same as the singularity expression of the SGA reflection coefficient in the water column, resulting in a sound siphon effect that causes the abnormally high SGA BRL and transmission loss in the water at the siphon frequencies. The siphon effect is very sensitive to seafloor acoustic parameters, might offer a physical base for geo-acoustic inversion, and show a dim light in a "gray area" for inverting the LVB sound attenuation at low to mid frequencies. As an example, the acoustic siphon effect and related seafloor geophysical parameters forming it in the Yellow Sea are reported in this paper.

Bi-level game theoretic approach for robust design: A case study of path-generating four-bar

This study addresses the bi-level multi-objective optimization problems (MOP) that raise in robust design and optimization of engineering systems through establishing a state-of-the-art game theoretic scenario. A novel leader-follower decentralized decision-making scenario is proposed, leveraging the synergy of game theory, Robust Design Optimization (RDO), Monte Carlo Simulation (MCS), and Artificial Intelligence (AI). The proposed algorithm can be employed for optimum robust Pareto design of a wide range of dynamical systems. In order to achieve a robust design, both the mean and variance of each objective function are considered as players in a multi-agent game setting. In this approach, both Stackelberg and cooperative games are utilized to model the behaviors of the players. Genetic Programming (GP) meta-models are employed to capture the Stackelberg protocol between two levels specifically for constructing the follower's rational reaction set (RRS). Additionally, the Nash bargaining function is -utilize to model the cooperative behaviors among players in each level. The proposed approach is applied and demonstrated through a case study involving multi-objective robust design of planar four-bar linkages. In this manner, four objective functions are assigned to four players within the system. Each player is responsible for optimizing a specific objective criterion, namely the mean of tracking error (TE), variance of tracking error, mean of transmission angle and variance of transmission angle (TA) of the linkage. As a result, the four-objective optimization problem of mechanism is transformed into a single-objective robust synthesis problem. The comparisons of the results show a significant enhancement in the robust behavior of the linkage, while ensuring that deterministic criteria such as quality of motion and precision are preserved.

Optimum Parameters in Ultrasound Coherent Plane Wave Compounding for High LPWV Estimation: Validation on Phantom and Feasibility in 10 Subjects.

The aim of this study is to determine the optimum and fine values of the number and transmission angles of tilted plane waves for coherent plane-wave compounding (CPWC)-based high local pulse wave velocity (LPWV) estimation. A Verasonics system incorporating a linear array probe L14-5/38 with 128 elements and a pulsatile pump, CompuFlow1000, were used to acquire radio frequency data of 3, 5, 7, and 9 tilted plane wave sequences with angle intervals from 0° to 12° with a coarse interval increment step of 1°, and the angle intervals from 0° to 2° with a fine interval increment step of 0.25° from a carotid vessel phantom with the LPWV of 13.42 ± 0.90 m/s. The mean value, standard deviation, and coefficients of variation (CV) of the estimated LPWVs were calculated to quantitatively assess the performance of different configurations for CPWC-based LPWV estimation. Ten healthy human subjects of two age groups were recruited to assess the in vivo feasibility of the optimum parameter values. The CPWC technique with three plane waves (PRF of 12 kHz corresponding to a frame rate of 4000 Hz) with an interval of 0.75° had LPWVs of 13.52 ± 0.08 m/s with the lowest CV of 1.84% on the phantom, and 5.49 ± 1.46 m/s with the lowest CV of 12.35% on 10 subjects. The optimum parameters determined in this study show the best repeatability of the LPWV measurements with a vessel phantom and 10 healthy subjects, which support further studies on larger datasets for potential applications.

Atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction

In high-altitude nuclear detonations, the proportion of pulsed X-ray energy can exceed 70%, making it a specific monitoring signal for such events. These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission. To quantitatively analyze the effects of different satellite detection altitudes, burst heights, and transmission angles on the physical processes of X-ray transport and energy fluence, we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction. The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays. The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method. Our improved method reduces this error to within 10% under the same conditions, even reaching 1% in certain scenarios. Moreover, its computation time is 48,000 times faster than that of the Monte Carlo method. These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors, inverting nuclear detonation source terms, and assessing ionospheric effects.

Research on Passive Location Strategy of UAV

Aiming at the problem of how to reasonably correct the position of UAV formation, we take the circular formation composed of 10 UAVs and the conical formation composed of 15 UAVs in the same plane as examples to study how to adjust the number and angle of UAV signal transmission so that the UAVs in the entire formation are in the designated position. This paper uses geometric model, greedy strategy and other methods, uses python, matlab and other software to obtain a reasonable and effective mathematical model, and makes a test and evaluation. The research results show that no matter circular, conical or other graphics, we can construct a triangle by connecting the transmitting signal and the receiving signal UAV, and solve the problem to obtain the best transmitting signal angle and the minimum number of sorties required; If there is no triangle between the UAV transmitting the signal and each UAV receiving the signal, the UAV receiving the signal will not reach the designated position. Nowadays, the use of UAVs is more and more extensive. The cooperation of multiple UAVs can complete many functions such as detection and performance, which is also the significance of our research on how UAVs can better receive signals.

Wavelength division multiplexing visible light communication with wide incident angle enabled by perovskite quantum dots

In this paper, a wavelength division multiplexing (WDM) visible light communication (VLC) system based on the perovskite quantum dots (QDs) with two different fluorescence wavelengths is demonstrated. This system consists of a transmitter, free space channel and a receiver. The NRZ-OOK (non-return-zero on-off-keying) signals are transmitted in this channel to achieve WDM visible light communication at a transmission distance of 60 cm, with a maximum transmission capacity of 100 Mbps in the field of view of 80°. In addition, computational temporal ghost imaging (CTGI) algorithm is used to reduce the bit error rate (BER) of the received signals and improve maximum transmission angle to 120°. The proposed WDM system paves the way for visible light communication in free space.

Slime mold algorithm for topology optimization: metagratings inverse design

In this paper we discuss the use of a metaheuristic (MH) gradient-free optimization method, specifically the slime mold algorithm (SMA), combined with the topology optimization (TO) method to design metasurfaces using a spectral modal method. The motivation behind using a MH approach comes from the drawbacks associated with traditional gradient-based methods. Normally, gradient-based methods require the calculation of the electromagnetic (EM) field at certain nodes within the computation domain. However, in spectral modal methods, this is unnecessary since these methods can compute the EM response without the need for field component values. Second, optimizing metagratings often involves a multimodal objective function with multiple local minimums and gradient-based methods might struggle with finding the global optimum. So to overcome these drawbacks, we propose using a MH approach, specifically the slime mold algorithm (SMA). We apply SMA to a metasurface design, especially in the context of TO and spectral methods, which is relatively unexplored. By coupling both TO with SMA, we successfully design metagratings capable of deflecting incident waves into a desired transmission angle.

Optimal power flow and computer‐based analysis of a simultaneous AC–DC power transmission system

AbstractElectricity demand is constantly increasing with the growing population, and the process of establishing new transmission lines has become complicated due to the rise in industrialization and urbanization. One solution to meeting this increased demand is to improve the power transfer capability by increasing the transmission voltage. However, the existing transmission lines may not be able to handle the increased load if they are pushed to their thermal limit. This paper presents a mathematical analysis of a simultaneous AC–DC transmission system transmitting power at different values of parameters. The computational analysis is carried out using MATLAB, and the circuit model simulation is validated by using power systems computer aided design (PSCAD/EMTDC). The transmitted power is evaluated by varying the transmission angle and transmission length for a fixed voltage, and then by varying the transmission angle and voltage for a fixed transmission length. Both these cases are analyzed using approximate and actual formulas. The results of the computation and simulation show close conformity.

Привод подачи режущего инструмента фрезерного станка для обработки вафельного фона

The paper describes the process of designing the cutting tool feed drive of a special metalworking machine, which due to the circuit solution and automatic control system will increase the productivity of processing one cell of wafer background on sheet material up to 10–15 seconds. On the basis of the analysis of the technology of milling of a given regular pattern of wafer background and peculiarities of the equipment operation it proposed to replace the traditional ball bearing gear in the cutting tool feed drive with a flat combined crank-slide mechanism. Geometrical parameters of the lever transmission mechanism calculated in accordance with the known dimensions of the regular cell pattern and the recommended value of the angle of motion transmission. The analysis of kinematic and power characteristics of the lever mechanism allowed to justify the technical characteristics of the electric motor. In order to realize the required trapezoidal law of the output link speed change, the inverse problem of kinematics solved, numerical values of the instantaneous angular velocity of the input crank and pulse control signals to the servomotor obtained.

Reconfigurable Wide‐Angle Beam‐Steering Terahertz Metasurfaces Based on Vanadium Dioxide

AbstractThe sixth generation (6G) wireless network is envisioned to provide faster and more reliable communication by utilizing electromagnetic waves in the terahertz spectrum. However, terahertz waves suffer from high propagation loss and, hence, wavefront manipulation solutions to focus and redirect terahertz waves are of paramount importance. Reconfigurable intelligent surface (RIS) is one such promising dynamic wavefront engineering solution proposed for 6G networks, but the technological realization of 6G (>100 GHz) RIS is still largely lacking. Here, spatially‐selective vanadium dioxide (VO2) patches incorporating coding metasurfaces for dynamic beam steering of terahertz waves are presented. The reversible and abrupt insulator‐to‐metal phase transition property of VO2 is exploited to achieve a reconfigurable transmission angle for the normal incident terahertz wave. By designing metasurfaces with specific linear phase gradients and designer phase sequencing, electrically switchable beam steering is achieved from co‐polarized 0° (normal transmission) in the OFF state to cross‐polarized 0° (control), 11°, 23°, 36°, and 52° in the ON state at 0.6 THz. Scaling up the proposed concept to achieve individual control of each active element (VO2) within the metasurface will enable a complete 6G RIS solution for full 3D terahertz beam manipulation to support the future THz wireless communication networks.

Investigation of a method to estimate the average speed of sound using phase variances of element signals for ultrasound compound imaging

PurposeIn the receive beamforming of an ultrasonography system, a B-mode image is reconstructed by assuming an average speed of sound (SoS) as a constant value. In our previous studies, we proposed a method for estimating the average SoS based on the coherence factor (CF) and the reciprocal of phase variances of element signals in delay-and-sum (DAS) beamforming. In this paper, we investigate the accuracy of estimation of the average SoS for compound imaging.MethodsFor this purpose, two numerical simulations were performed with k-Wave software. Also, the estimation methods based on the CF and the reciprocal were applied to in vivo data from the common carotid artery, and B-mode images were reconstructed using the estimated average SoS.ResultsIn the first numerical simulation using an inhomogeneous phantom, the relationship between the accuracy and the transmission angles for the estimation was investigated, and the root mean squared errors (RMSEs) of estimates obtained based on the CF and the reciprocal of the phase variance were 1.25 ± 0.09, and 0.765 ± 0.17% at the transmission sequence of steering angles of (− 10°, − 5°, 0°, 5°, 10°), respectively. In the second numerical simulation using a cyst phantom, lateral resolutions were improved by reconstructing the image using the estimates obtained using the proposed strategy (reciprocal). By the proposed strategy, improvement of the continuity of the lumen–intima interface in the lateral direction was observed in the in vivo experiment.ConclusionConsequently, the results indicated that the proposed strategy was beneficial for estimation of the average SoS and image reconstruction.

Independent-regulated double-edge Janus angular absorber for terahertz waves based on photonic edge band gaps and graphene wide-angle absorption

In this paper, three categories of Janus angle absorption structures for terahertz (THz) waves are realized by operating the edge hopping property of the photonic band gaps (PBGs) and the wide-angle absorption of graphene heterostructure. The left and right edges of the angle window are determined by the PBGs generated by photonic crystals 1 (PC1) and photonic crystals 2 (PC2), respectively. The appropriate combination of the two can obtain a transmission angle window (TAW), and the edges can be independently manipulated, which makes it possible to construct arbitrary angle filtering structures, making up for the shortage of rigid angle windows in traditional research. Graphene material has absorption potential, and when it is introduced into ternary photonic crystals 3 (PC3), high absorption at large angles will occur. The combination of PC3 and TAW will produce an absorption angle window (AAW) by using the energy cascade transmission features of photonic crystals (PCs). Contributing to the strong absorption properties, the energy transfer on both sides of PC3 is isolated. Consequently, the Janus angle absorption phenomenon will be remarkable by mirroring the PCs structures with different TAWs on both sides of PC3. Through the unique parameter design, the three relationships between the forward AAW and the backward one are investigated, that is inclusion, partial coincidence, and incoherence.

Retail investor attention and stock market behavior in Russia-Ukraine conflict based on Chinese practices: Evidence from transfer entropy causal network

From the non-linear information transmission angle, we look into the interactions between retail investor attention and the stock market before and during the Russia-Ukraine conflict. We construct transfer entropy causal networks between retail investor attention and stock market behavior on three counts: return, trading volume and volatility. We discover that bi-directional causal relations exist between investor attention and the stock market. We also find that after the conflict outbreak, retail investor attention becomes more influential on return, trading volume and volatility. The stock market return and volatility have more impact on investor attention. Information transfer efficiency increases after the outbreak.

Etalon-Assisted Study of the Strong CO Ligand Vibrations of the fac-[Re(CO)3(bpy)(CH3CN)]+ Octahedral Complex.

The strong CO ligand vibrations of an octahedral complex, fac-[Re (CO)3(bpy)(CH3CN)]+, in acetonitrile are observed at 2040 and 1932 cm-1. Facial rhenium tricarbonyl systems offer very strong and isolated CO vibrations with the potential for interactions between these vibrations. This work first identifies the dominant ion-pair species using attenuated total reflection infrared (ATR-IR) absorption spectra on a dilution series and then determines the strength of these CO ligand vibrations (as isolated vibrations) with a combination of ATR-IR and etalon-based measurements that determine the absolute complex index of refraction of the solution. Finally, the etalon experiments are modeled to study the interaction between vibrations, which is a property not embedded in the solution's complex index of refraction. The ATR-IR spectra are accomplished on a dilution series as well as a larger set of spectra as these solutions evaporated. The A'(1) CO ligand band at 2040 cm-1 is fit with a sum of three Lorentzian functions characterizing the distribution of free, solvent-separated, and contact ion pairs of this octahedral complex vs concentration. The other CO ligand band at 1932 cm-1 is broader and complicated by the dynamics of vibrational interactions, the unresolved splitting of the A'(2) and A″ CO vibrations, and ion-pair speciation. The etalon transmission measurements vs angle were on a 0.029 M solution, and Rabi splittings of 19 and 38 cm-1 were observed for the A'(1) CO vibration and the unresolved A'(2) + A″ CO vibrations, respectively. The great strength of the CO ligand vibrations is evident despite the use of a dilute solution. Integrated band intensities are reported in comparison to hybrid density functional calculations for isolated vibrations. Then, the observed Rabi splittings are modeled to obtain the coupling strength of the CO ligand vibration with etalon cavity modes and with each other. In summary, this work develops a method to determine the concentration of these solutions from the ATR-IR spectrum, characterizes the ion-pairing, shows that the index of refraction is not constant in the IR spectral region of interest, and develops an interaction Hamiltonian that characterizes cavity-vibration and vibration-vibration coupling.

Low-Complexity Pareto-Optimal 3D Beamforming for the Full-Dimensional Multi-User Massive MIMO Downlink

Full-dimensional (FD) multi-user massive multiple-input multiple output (m-MIMO) systems employ large two-dimensional (2D) rectangular antenna arrays to control both the azimuth and elevation angles of signal transmission. We introduce the sum of two outer products of the azimuth and elevation beamforming vectors having moderate dimensions as a new class of FD beamforming. We show that this low-complexity class is capable of outperforming 2D beamforming relying on the single outer product of the azimuth and elevation beamforming vectors. It is also capable of performing close to its FD counterpart of massive dimensions in terms of either the users' minimum rate or their geometric mean rate (GM-rate), or sum rate (SR). Furthermore, we also show that even FD beamforming may be outperformed by our outer product-based improper Gaussian signaling solution. Explicitly, our design is based on low-complexity algorithms relying on convex problems of moderate dimensions for max-min rate optimization or on closed-form expressions for GM-rate and SR maximization.

Flexibly control of vortex beams based on all-dielectric Pancharatnam-Berry phase transmission encoding metamaterials

Because the ohmic loss of metal materials affects the transmission efficiency of metasurface, we design a transmission-type all-dielectric coded metasurface element structure based on the principle of Pancharatnam-Berry geometric phase. We digitally encode these cell structures to construct a coded metasurface. In order to flexibly regulate the transmission angle of vortex beam encoded metassurface, we introduce the Fourier convolution principle in digital signal processing to perform the Fourier convolution addition operation for two different coding sequences. A new coding sequence is constructed by Fourier convolution operation of digital coding unit. Through this operation, the number of elements on the coded metasurface is constant, and the scattering angle of the vortex beam is flexibly controlled. In order to realize the multifunctional integration of phase vortex beams, we introduce the principle of digital coding addition in the complex domain to add two digitally coded metasurface sequences with different functions to realize the multifunctional superposition.

Multi-link mechanism-inspired palletizing manipulator: Design, optimization and experimental results

The precision of trajectory tracking and stable operation with sorting merchandise are the main challenges for palletizing manipulators in different working conditions, especially in sorting glass-substrate. To ensure the adaptability of the manipulator under different working conditions, including operational efficiency, motion space, and control accuracy, the structural optimization and the motion control methods of the manipulator should be considered. In this paper, the structure optimization and tracking control of the manipulator for sorting glass substrates are studied. Firstly, considering the optimization factors including stroke speed ratio k, transmission angle [Formula: see text] and the sum of link-rod lengths l of the crank rocker mechanism, a structural optimization method based on genetic algorithm is applied to enhance the flexible maneuverability. Furthermore, a feedforward-feedback iterative learning control (ILC) algorithm is adopted to the high accuracy of position tracking. Finally, experimental results verify the feasibility of structural optimization and tracking control, which can be effective applied in practical engineering.

Study on transmission angle and singularity in 5R planar mechanism

Transmission angle is one of the important design criteria to be considered for the effective force and motion transmission of a mechanism. Poor transmission angles are detrimental to the performance of a mechanism as they exaggerate the effect of friction and clearances. In addition, the torque required to overcome external load tends to increase and the required torque capacity of the drive increases unnecessarily. The singularity positions in a workspace are closely related to the transmission angle of the manipulator configuration. For achieving a large singularity-free area, the configuration dimension needs to be increased. Even though the objective is to design a compact five-bar planar mechanism, the link dimensions are likely to increase to some extent while achieving the desired transmission angles. This paper deals with estimating the singularity-free area of a five-bar mechanism by considering variations in transmission angles for different link lengths. The generalized methodology presented in this work demonstrates the estimation of singularity-free largest reachable area and link proportions at which intra-link transmission angles are confined. A dimensionless singularity-free workspace index is proposed to quantify performance at various transmission angles.