Rotational Characteristics Research Articles

Infrared attitude measurement method for spinning projectile under snow background

In order to obtain the attitude of spinning projectile over snow surface, an infrared attitude measurement method for spinning projectile under snow background is proposed. First of all, combining the radiation characteristics of the snow surface and the propagation law of the atmospheric infrared radiation, the relationship between the infrared radiation over snow and the inclination angle to the ground is deduced. Secondly, the infrared attitude measurement model is built on the basis of the rotation characteristics of the projectile. At last, the attitude solution algorithm of spinning projectile is designed. On the basis of the error transfer coefficient, the effects of direct solution algorithm and indirect solution algorithm are analyzed, and the feasibility of the designed solution method is verified by experiment. The results indicate that the pitch angle solution error is within ±1.5° and the roll angle solution error is within −1.5° to 1°, which can provide a good angles estimation for projectile guidance over snow.

Analysis and modeling of workpieces’ kinematic in the process of two-sided face grinding

The systematization of kinematic characteristics of rotation of workpieces during two-sided face-grinding processing is carried out. It is established that the dependence of the workpiece rotation frequency on its current coordinate in the grinding zone can be attributed to six types. The equivalent rotation characteristics used in modeling of the grinding process are proposed and their mathematical description is given. The impact of the workpiece rotation characteristics on the forming process, and processing accuracy is considered. Recommendations for implementing rational rotation of workpieces are given.

Mechanofluorochromism of Triphenylamine-BODIPY: Effect of twisted intramolecular charge transfer and restriction in rotation on fluorescence

The majority of the studies in the field of mechanofluorochromism (MFC), based on donor (D)-acceptor (A) complexes, have reported that MFC was strongly associated with the intramolecular charge transfer (ICT) character and aggregation-induced emission (AIE). However, the mechanism of MFC has been inconclusively demonstrated. In this study, a triphenylamine (TPA) introduced BODIPY complex was designed and synthesized to demonstrate the mechanism of MFC based on the D-A complex. We identified the effect of an external stimuli on the molecular geometry by employing solid state NMR, UV–vis spectroscopy, and density functional theory (DFT) calculations; this was because geometry, depending on the stimuli, has been established as a key for determining emission properties. The relationship between the identified geometry and the emission properties was experimentally investigated with regard to the ICT and restriction in rotation (RIR) characteristics. Under external stress, fluorescence quenching was suppressed by RIR, and the molecular planarization-induced weak ICT character hypsochromically shifted the emission spectrum. However, as the external stimuli were not applied, fluorescence quenching occurred due to the freely rotating molecules; further, the emission spectrum was bathochromically shifted due to the strong ICT character that was induced by the high torsional angle between D and A.

Analysis of the characteristics of English part of speech based on unsupervised machine learning and image recognition model

If there are more external interference factors in the process of intelligent recognition in English, the recognition accuracy will be greatly reduced. It is of great academic value and application significance to deeply study feature recognition of English part-of-speech and realize automatic image processing of English recognition. Based on unsupervised machine learning and image recognition technology, this study combines the actual factors of English recognition to set the corresponding influencing factors and proposes a reliable method to identify multi-body rotating characters. This method utilizes the principle of the periodic characteristics of the trajectory rotation on the feature space. Moreover, this study conducts a comparative analysis of recognition accuracy by comparative experiments. In addition, this paper analyzes the recognition principles of 4 fonts in detail. The research results show that the proposed method has certain effects and can provide theoretical reference for subsequent related research.

Numerical simulation of water entry of an inclined cylinder

Water entry of cylindrical structures is a complex multiphase flow problem involving a three-phase medium interaction that occurs instantaneously. It is a nonlinear and unsteady process, which the physical understanding of mechanism in the aspect of evolution of cavity dynamics and multiphase flow field is yet to be fully understood. In the present work, a three-dimensional numerical model of six degrees of freedom (DOF) based on the shear stress transport (SST) k−ω eddy viscosity model was established to capture the complicated characteristics of the vertical water entry of an inclined cylinder at various entry velocities. A volume of fluid method for tracking air-water interface and a combined dynamic fluid body interaction and overlapping grid technology were used to simulate the complex motion. The numerical model with laminar and turbulent model was verified against the published experimental data of cavity evolution and motion characteristics. A parametric study was conducted to study the translational and rotational characteristics of the structure due to the effect of water entry velocity. The investigation revealed the secondary closure phenomenon during the water entry. The asymmetrical multiphase flow field showed that its dynamic characteristics change with space and time under the effect of cavity evolution.

Mesocyclonic and non-mesocyclonic convective storms in Germany: Storm characteristics and life-cycle

A multi-year analysis of mesocyclonic (approximately 4300) and non-mesocyclonic convective storms (more than 100,000) is presented. A comprehensive data set is generated which includes measurements from a lightning location system, a precipitation radar network, as well as information from automated cell detection algorithms based on radar reflectivity and radial winds. Storms' rotation, reflectivity, lightning and motion characteristics are analysed for storms with different lifetimes. Furthermore, the temporal evolution of the storms' attributes is analysed in order to study the convective life-cycle. For this purpose, the storms are grouped according to their lifetime. The temporal evolution of storm attributes varies from one storm to the other, however, typical storm developments are revealed. The average temporal evolution of the storm size is symmetric, the maximum is reached at the half of the lifetime. In contrast, the maximum lightning rate is reached later. Comparing the attributes of non-mesocyclonic and mesocyclonic storms, varies differences are identified. Mesocyclonic storms are shown to be typically longer-living (the median is approximately 30 min longer), larger, faster moving (on average approximately 15 km/h faster) and electrically more active compared to non-mesocyclonic storms. These characteristics are more pronounced for stronger mesocyclonic storms.

Research on plantar pressure dynamic distribution characteristics of samba step movements based on biomechanics

Samba dance is a factional part of sports dance. It forms a sports dance system with modern dance. According to the method of sports biomechanics experiment, the dynamic parameters and changing rules of fork foot pressure dynamic distribution characteristics are summarised, which can provide theoretical reference for further study of the basic law of samba dance. From the point of view of sports biomechanics, this paper analyses the rotation of athletes, and combines the knowledge of biomechanics with the rotation characteristics of samba dance. Studies have shown that in the comparison of general parameters, the different indicators of the foot pressure have a certain regularity in different action stages. There were no significant differences between the test group and the control group in terms of walking speed, relative speed, step size, relative step size, foot contact area time, and duration.

Cold formed steel storage racks subjected to axial, shear and bending interactions

This research article aims to study the behaviour of expansion bolts under axial, shear and bending interaction of base plate connected cold form steel storage racks. The bilinear moment rotation relationship was adopted to identify the ultimate moment of resistance and stiffness of the base plate connected to a concrete block using M10 grade anchor bolt at different range of axial loads ranging from 25% to 100% there by the design strength of upright profile was studied. The dimension of the upright and the base plate thickness has to be changed so that the extreme stability under various ranges of axial and transverse loads had been studied. Using finite element analysis software (Abaqus), a model has been created and designed to observe moment rotation characteristics, behaviour of base plate under simultaneous axial, shear and bending interactions and compared with experimental analysis. Comparative studies reveal that there was no failure in the concrete block and when the upright thickness increases, the stiffness and moment of the base plate increases despite having a similar cross section. An interaction equation was developed to find the stiffness and ultimate moment of resistance of the base plate connection.

A vortex-type solar updraft power-desalination integrated system

In this paper, the convection vortex theory is combined with the existing solar chimney power plant combined with desalination (SCPPCSD), and a solar vortex power desalination system (SVPDS) is proposed. In SVPDS, the strong cyclone column generated by the convection vortex is used to replace the solid chimney. The physical model and three-dimensional numerical model of SVPDS are built. The flow field distributions in the solar vortex power plant (SVPP) and SVPDS under no-load condition are compared and analyzed, and the distribution rules of each parameter along the radial and axial direction and output performance are obtained. The results show that the simulation field has strong rotation characteristics, and there is obviously a low pressure area in the center of SVPDS, which enables the system to continuously draw in surrounding air, thus forming a stable vortex flow field. The maximum negative pressure of vortex center in SVPDS is −126.98 Pa, and the hourly freshwater output is about 7.92136 ton/h. Due to the sucking effect of vortex, the radial distributions of temperature and negative pressure at different heights both decrease from the center to the surrounding. With the increase of height, the temperature of central airflow, the pressure difference between the vortex center and the external environment are both decreasing, and finally close to the external environment. The vortex core structure can be obviously seen in the center, and the tangential velocity distribution is more consistent with the distribution of the Rankine combined vortex. The tangential velocity slowly decreases with the increase of height and then transforms into axial velocity. The temperature, vortex center negative pressure and tangential velocity in SVPDS are all slightly smaller than those of SVPP. With the increase of solar irradiance, the freshwater output and the vortex center maximum negative pressure both increase significantly.

A multi-scale MCCPFEM framework: Modeling of thermal interface grooving and deformation anisotropy of titanium alloy with lamellar colony

Micro-scale thermal interface grooving (TIG), as an important breakdown mechanism of single lamella and the key to spheroidization of lamellar colony, does significant influence on the mechanical response and microstructural evolution of titanium alloy with lamellar colony during hot working. This influence may become remarkable by coupling with meso-scale deformation anisotropy of the colony. The coupled effect across different scales is crucial to the spheroidization of lamellar colony, while rare related research is reported due to the difficulty in experiment. In this work, a multi-scale MCCPFEM framework was proposed to model on the micro-scale TIG and meso-scale deformation anisotropy through the fully coupling of lattice kinetic Monte Carlo (MC) model and crystal plasticity finite element model (CPFEM). During the modeling, the modified MC algorithm was established based on the multiple-integral method (MIM) solution with Mullin's theory, which accounts for the TIG's microstructural evolution. In addition, the deformation anisotropy at different length scales including strain localization at lamella, and strain partitioning at colony was characterized by an explicit CPFEM which includes resistance anisotropy of slip systems, evolution of dislocations and high-fidelity representative lamellar colony. At the same time, geometrically necessary dislocation (GND) was also considered in the CPFEM by developing a new algorithm with mesh-free methodology and re-construct radial basic shape functions. The fully coupling of the multi-scale MCCPFEM was realized through the microstructure-based 2D grids acting as both finite elements and lattice sites. Moreover, re-set ‘zero’ of the deformation gradient of the TIG mesh was proposed to characterize the strain-free state of new TIG nucleation. Then, the TIG-induced changes in the dislocation density, lattice rotation, strain-free state and morphological characteristics were returned to MCCPFEM to determine the heterogeneous deformation and anisotropic mechanical response of the lamellar colony. With this multi-scale model, the coupled effect of the deformation anisotropy (strain localization in beta phase, stress relief in TIG and local internal stress concentration in alpha lamella) and TIG-induced microstructural evolution during the isothermal compression of the IMI834 alloy with lamellar colony is well captured and analyzed.

Conserved buried water molecules enable the β-trefoil architecture.

Available high-resolution crystal structures for the family of β-trefoil proteins in the structural databank were queried for buried waters. Such waters were classified as either: (a) unique to a particular domain, family, or superfamily or (b) conserved among all β-trefoil folds. Three buried waters conserved among all β-trefoil folds were identified. These waters are related by the threefold rotational pseudosymmetry characteristic of this protein architecture (representing three instances of an identical structural environment within each repeating trefoil-fold motif). The structural properties of this buried water are remarkable and include: residing in a cavity space no larger than a single water molecule, exhibiting a positional uncertainty (i.e., normalized B-factor) substantially lower than the average Cα atom, providing essentially ideal H-bonding geometry with three solvent-inaccessible main chain groups, simultaneously serving as a bridging H-bond for three different β-strands at a point of secondary structure divergence, and orienting conserved hydrophobic side chains to form a nascent core-packing group. Other published work supports an interpretation that these interactions are key to the formation of an efficient folding nucleus and folded thermostability. The fundamental threefold symmetric structural element of the β-trefoil fold is therefore, surprisingly, a buried water molecule.

Identification of Short-Rotation Eucalyptus Plantation at Large Scale Using Multi-Satellite Imageries and Cloud Computing Platform

A new method to identify short-rotation eucalyptus plantations by exploring both the changing pattern of vegetation indices due to tree crop rotation and spectral characteristics of eucalyptus in the red-edge region is presented. It can be adopted to produce eucalyptus maps of high spatial resolution (30 m) at large scales, with the use of open remote sensing images from Landsat 8 Operational Land Imager (OLI), MODerate resolution Imaging Spectroradiometer (MODIS), and Sentinel-2 MultiSpectral Instrument (MSI), as well as a free cloud computing platform, Google Earth Engine (GEE). The method is composed of three main steps. First, a time series of Enhanced Vegetation Index (EVI) is constructed from Landsat data for each pixel, and a statistical hypothesis testing is followed to determine whether the pixel belongs to a tree plantation or not based on the idea that tree crops should be harvested in a specific period. Then, a broadleaf/needleleaf classification is applied to distinguish eucalyptus from coniferous trees such as pine and fir using the red-edge bands of Sentinel-2 data. Refinements based on superpixel are performed at last to remove the salt-and-pepper effects resulted from per-pixel detection. The proposed method allows gaps in the time series that are very common in tropical and subtropical regions by employing time series segmentation and statistical hypothesis testing, and could capture forest disturbances such as conversion of natural forest or agricultural lands to eucalyptus plantations emerged in recent years by using a short observing time. The experiment in Guangxi province of China demonstrated that the method had an overall accuracy of 87.97%, with producer’s accuracy of 63.85% and user’s accuracy of 66.89% for eucalyptus plantations.

Investigation of Mixed Symmetry States in 170-178Yb isotopes

low-lying positive parity states, dynamic symmetries, mixed symmetry states (MSS), reducing electric quadrupole transition probabilities B(E2), branching ratio, reducing magnetic dipole transition probabilities B(M1), and mixing ratios δ(E2/M1) for 170-178Yb have been investigated by applied IBM-1 and IBM-2 program package. The software package IBM-1 and IBMT computer code for IBM-1 and Neutron Proton Boson NPBOS and Neutron Proton Boson Electromagnetic NPBEM software package have been used. The Ytterbium nuclei with the (170 − 178) mass number considered as rotational nuclei after applying the first and second interacting boson model with studying dynamic symmetry and energy ratios , and that approximated to (3.33,7 and 12). The reducing transition probability for electric quadruple B(E2) and branching ratios that state the small values of the ratios R′ and R″ as having rotational characteristics. A study of the mixed symmetry state of these nuclei shows that the lower energy mixing level is the first 1+ level, which distinguishes the rotational determination nuclei. The energy levels values for the states have a clear mixed symmetry state (MSS) directly proportional with Majorana parameters ζ2, while , and , tend to be approximately more conservative.

МОДЕЛИРОВАНИЕ КИНЕМАТИЧЕСКИХ ХАРАКТЕРИСТИК ПРОЦЕССА ДВУСТОРОННЕЙ ТОРЦЕШЛИФОВАЛЬНОЙ ОБРАБОТКИ

The paper is dedicated to the bilateral end-finishing improvement at the expense of efficient kinematic characteristics realization in parts machined ensuring limiting errors minimization in end surfaces. 
 A systematization of parts rotation experimental characteristics is carried out. It is shown that they may be referred to six basic kinds. There are offered equivalent characteristics of rotation used while grinding modeling and their mathematical description is given. The dependences obtained determine a kinematic parameter of a shaping form in the equation of the surface worked. 
 There is considered an influence of billet rotation characteristics upon shaping and accuracy of frictionless bearing cylindrical roller machining under virtual technological conditions equivalent to industrial. As a result of computer experiments carried out it is defined that dynamics and balance of shape errors and a relative position of end surfaces of the roller to a considerable extent are defined with the kind of realized rotation characteristics. 
 The error sensitivity of a shape and end beating to kinematic characteristics realized and technological parameters must be taken into account during bilateral end-finishing control.

Rotatability of the Floating Link on Multi-Loop Planar Linkages

Abstract This paper proposes a method to deal with the orientation uncertainty problem affected by joint clearances. To solve this problem, it is necessary to establish the theory of mobility of the floating link of multi-loop linkages. Since the theory of the mobility of floating link is yet complete, this paper provides a simple treatment to determine the rotatability between any two links, adjoined or not, in planar multi-loop linkages. The rotation angle of the floating link with respect to the reference link is defined so that there is no ambiguity in analyzing the rotation range of the floating link. Based on the joint rotation space (JRS) method, one may identify not only the branch formation but also the rotatability between any two links on each of the branches. It is a visualized method that reveals the rotation characteristic of multi-loop linkages. This paper demonstrates the rotation range of the floating link with respect to the reference link on six-bar Stephenson linkages, 2-degree-of-freedom (DOF). 7-bar linkages, and 3-DOF. Eight-bar parallel manipulators. This might be the first paper to deal with the rotatability of 3-DOF planar multi-loop linkages. This paper uses the method to predict the clearance-induced angle uncertainty of the 8-bar parallel manipulators, which determines the worst orientation error of the end-effector and fills up the void of the joint clearance uncertainty model proposed by Ting et al. (2017, “Clearance-Induced Position Uncertainty of Planar Linkages and Parallel Manipulators,” J. Mech. Rob., 9, p. 061001).

Uncovering rotational multifunctionalities of coupled Kresling modular structures

Origami-inspired designs for structural and material systems have received significant attention due to their attractive kinematic and mechanical properties, design flexibility, reconfigurability, and multifunctionality. While promising, almost all studies have been focusing on the translational motion/deformation of structures and materials. Little attention has been given to origami-based designs in rotational elements, such as joints, shafts, and motors, despite the ubiquity of such functions in engineering. This research advances the state of the art through introducing a new coupled Kresling modular structure (CKMS) concept to achieve pure rotational motions created by integrating two Kresling origami tube modules with opposite chirality. A model with nondimensionalized parameters is first developed to investigate the various kinematic and mechanical properties of CKMS. Results show that several key CKMS rotational characteristics, such as multistability, energy absorption, and tunable stiffness can be programmed by varying key geometric design parameters. We find that interactions between modules may give rise to an asymmetric bistable property that enhances energy absorption. The CKMS enables tunable stiffness and quasi-zero stiffness (QZS) in rotation, which can be harnessed for vibration isolation. Furthermore, the proposed CKMS exhibits self-locking, a feature of certain origami patterns that arises from panel contact and offers a means to change stiffness significantly. Design guidelines to synthesize the multiple functionalities and mechanical properties explored in this research are discussed. The outcomes lay the foundation for origami-inspired structures that can transmit torque, isolate torsional vibrations, and absorb energies in rotational systems.

0184 Predicting Strategic Napping in Surgical Residents by Individual and Rotation Characteristics

Abstract Introduction Strategic napping, or napping on-shift, is recommended to reduce fatigue in medical residents. The actual prevalence of strategic napping in relation to residents’ workload, schedule, or demographics is largely unquantified. This study objectively measured sleep patterns and work schedules in surgical residents working a variety of service lines over a two-month period in order to identify which resident and service line attributes predict on-shift napping. Methods Surgical residents from an academic surgery program in the Washington, DC area provided schedule information, completed the Epworth Sleepiness Scale (ESS), and wore sleep-tracking devices (Zulu Watch) continuously for 8 weeks. Multiple linear regression was performed to predict percent days with on-shift napping from resident demographics (age, gender, post graduate year (PGY), sleep characteristics (ESS, total sleep time (TST), sleep efficiency (SE)), schedule characteristics (shift start time, shift length, rotation length, percent days on-shift, percent night shifts), and service line characteristics (service line category, number of service lines worked). Results Twenty-two (n=22) residents completed the study, rotating through at least 1 of 5 different service line categories (Acute Non-Elective Surgery, Elective Surgery, Night Float, Surgical Intensive Care Unit, and Other). Residents slept an average of 6 hours within a 24-hour period (370±129 minutes) with normal SE (87.13%±7.55%). ESS scores indicated excessive daytime sleepiness (11.64±4.03). Ninety-five percent (n=21) of residents napped at least once while on shift. Residents napped on-shift approximately 32% of their working days and were most likely to nap when working between 2300-0500 hours. Earlier shift start times predicted less on-shift napping (B=-0.08,SE=0.04,β=-2.40,t=-2.09,p=0.05) while working more night shifts (B=1.55,SE=0.44,β=4.12,t=3.52,p=0.003) and shifts over 24 hours. Conclusion Residents take advantage of opportunities to nap on-shift, particularly when working at night. Despite naps, however, residents exhibit insufficient sleep with excessive daytime sleepiness, representing a safety risk to themselves and their patients. Support NA

Morphodynamic Modelling of Flash Rip Current Driven Coastal Sediment Transport

Park, S.; Kim, D.-H., Yoo, H., 2020. Morphodynamic modelling of flash rip current driven coastal sediment transport. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1229–1234. Coconut Creek (Florida), ISSN 0749-0208.The characteristics of the sediment transport driven by flash rip currents at nearshore areas was investigated using a morphodynamic model coupled with a fully nonlinear Boussinesq-type model and a sediment transport model. Wave transform processes in surfzone such as shoaling, refraction, breaking, runup, and rundown processes were included in the numerical model. The vorticity and turbulent eddy viscosity were considered to account for rotational and turbulent flow characteristics. In addition, the horizontal density variation and bottom evolution caused by sediment transport were integrated into the fully nonlinear Boussinesq-type model. A fourth-order finite volume method, based on the MUSCL scheme with an approximate Riemann solver, was used to solve the governing equations. Uniform and parallel wave fields were simulated on a plain beach with a uniform sandbar with very small disturbance on the bathymetry. Because the wave generator was parallel to the beach, no significant longshore current and longshore sediment transport were generated. From the tested case, transient offshore-directed strong rip currents (the wave-averaged flow velocity 0.5 m/s) appeared in various locations. Turbid suspended sediment currents were also randomly generated by the waves and currents. The modelling results and analysis showed that the offshore direction sediment transport was strongly associated with the flash rip current generated within the surfzone.

Experimental Investigation on Dust Vertical Coagulation Process in an Ethylene RF Discharge Plasma

The characteristics of dust coagulation process in gravitational direction are investigated in an ethylene RF (radio frequency) discharge plasma system. The experiment shows that dust particles can aggregate into the huge fractal structure (centimeter scale). The coagulation process is mainly characterized by the scattering laser intensity, the distribution of dust clouds, and the fractal dimension. In this experiment, the rotational characteristics of the huge fractal structure can be observed and investigated by the oscillation of the scattering spectrum. These results provide an experimental basis for the investigation of dust coagulations.

Spot and Adjust Filter: a New Image Filter for Image Enhancement and Noise Reduction

Wind and earthquake disasters in the world often cause billions of dollars of damage to buildings, most of which is to non-engineered buildings-especially homes. Wood-frame homes use connectors which exhibit partial rotational rigidity at the member ends, making analytical solutions difficult. This is due to the lack of information about the complex behavior of the connections used in this type of buildings, and the lack of a methodology to analyze light-timber frame buildings with flexible joints. In order to address the problem, tests were carried out to determine the moment rotation characteristics of wood joints made of conventional and mechanical fasteners. During testing, it was discovered that rotational stiffness of timber connections is a function of the axial load as well as the shear load. Comparison of ordinary timber connections with metal connectors were made. Resisting moment capacity of joints with different connectors were also determined. This paper presents a new method of testing for joint stiffness and the experimental results obtained during testing for stud-to-bottom-plate, rafter-to-ridge-board, and top-plate-to-rafter connections using different connectors.