Continuous Rotation Mode Research Articles

A multi-stable rotational energy harvester for arbitrary bi-directional horizontal excitation at ultra-low frequencies for self-powered sensing

A rotational multi-stable energy harvester has been presented in this paper for harnessing broadband ultra-low frequency vibrations. The novel design adopts a toroidal-shaped housing to contain a rolling sphere magnet which absorbs mechanical energy from bidirectional base excitations and performs continuous rotational movement to transfer the energy using electromagnetic transduction. Eight alternating tethering magnets are placed underneath its rolling path to induce multi-stable nonlinearity in the system, to capture low-frequency broadband vibrations. Electromagnetic transduction mechanism has been employed by mounting eight series connected coils aligned with the stable regions in the rolling path of the sphere magnet, aiming to achieve greater power generation due to optimized rate of change of magnetic flux. A theoretical model has been established to explore the multi-stable dynamics under varying low-frequency excitation up to 5 Hz and 3 g acceleration amplitudes. An experimental prototype has been fabricated and tested under low frequency excitation conditions. The harvester is capable of operating in intra-well, cross-well, and continuous rotation mode depending on the input excitation, and the validated physical device can generate a peak power of 5.78 mW with 1.4 Hz and 0.8 g sinusoidal base excitation when connected to a 405 Ω external load. The physical prototype is also employed as a part of a self-powered sensing node and it can power a temperature sensor to get readings every 13 s on average from human motion, successfully demonstrating its effectiveness in practical wireless sensing applications.

Crystal structure of 9,10-bis-((perchloro-phenyl)-ethynyl)anthracene determined from three-dimensional electron diffraction data

Abstract The crystal structure of the title compound was determined using electron diffraction data collected in continuous rotation mode. The structure was successfully solved and refined kinematically in the monoclinic space group P21/c, with a Z value of 2 and Z′ value of 0.5. Within the crystal structure, the entire molecule is predominantly flat. The molecular packing exhibits a herringbone pattern, distinct from that of the unchlorinated analogue molecule. The largest facet of the crystals, which faces the supporting carbon film, is designated as (0 1 ‾ 1 ‾ $\bar{1}\bar{1}$ ).

Electron crystallography and dedicated electron-diffraction instrumentation.

Electron diffraction (known also as ED, 3D ED or microED) is gaining momentum in science and industry. The application of electron diffraction in performing nano-crystallography on crystals smaller than 1 µm is a disruptive technology that is opening up fascinating new perspectives for a wide variety of compounds required in the fields of chemical, pharmaceutical and advanced materials research. Electron diffraction enables the characterization of solid compounds complementary to neutron, powder X-ray and single-crystal X-ray diffraction, as it has the unique capability to measure nanometre-sized crystals. The recent introduction of dedicated instrumentation to perform ED experiments is a key aspect of the continued growth and success of this technology. In addition to the ultra-high-speed hybrid-pixel detectors enabling ED data collection in continuous rotation mode, a high-precision goniometer and horizontal layout have been determined as essential features of an electron diffractometer, both of which are embodied in the Eldico ED-1. Four examples of data collected on an Eldico ED-1 are showcased to demonstrate the potential and advantages of a dedicated electron diffractometer, covering selected applications and challenges of electron diffraction: (i) multiple reciprocal lattices, (ii) absolute structure of a chiral compound, and (iii) R-values achieved by kinematic refinement comparable to X-ray data.

Reduced volume of diabetic pancreatic islets in rodents detected by synchrotron X-ray phase-contrast microtomography and deep learning network

The pancreatic islet is a highly structured micro-organ that produces insulin in response to rising blood glucose. Here we develop a label-free and automatic imaging approach to visualize the islets in situ in diabetic rodents by the synchrotron radiation X-ray phase-contrast microtomography (SRμCT) at the ID17 station of the European Synchrotron Radiation Facility. The large-size images (3.2mm×15.97mm) were acquired in the pancreas in STZ-treated mice and diabetic GK rats. Each pancreas was dissected by 3000 reconstructed images. The image datasets were further analysed by a self-developed deep learning method, AA-Net. All islets in the pancreas were segmented and visualized by the three-dimension (3D) reconstruction. After quantifying the volumes of the islets, we found that the number of larger islets (=>1500 μm3) was reduced by 2-fold (wt 1004±94 vs GK 419±122, P<0.001) in chronically developed diabetic GK rat, while in STZ-treated diabetic mouse the large islets were decreased by half (189±33 vs 90±29, P<0.001) compared to the untreated mice. Our study provides a label-free tool for detecting and quantifying pancreatic islets in situ. It implies the possibility of monitoring the state of pancreatic islets in vivo diabetes without labelling.

Broadband and Output‐Controllable Triboelectric Nanogenerator Enabled by Coupling Swing‐Rotation Switching Mechanism with Potential Energy Storage/Release Strategy for Low‐Frequency Mechanical Energy Harvesting

AbstractIrregular and low‐frequency mechanical energy, including ocean energy, is widely distributed but mostly wasted. Triboelectric nanogenerator (TENG) has been proved as a very promising ocean energy harvesting technology. However, the traditional cylindrical pendulum TENG (CP‐TENG) can only work effectively in a narrow frequency bandwidth. In this work, a triboelectric nanogenerator enabled by coupling the swing‐rotation switching mechanism with a potential energy storage/release strategy (SR‐TENG) is presented. It can convert various swing/vibration mechanical energies into electric energy, and it has a controllable output performance whether it works under intermittent rotation mode or continuous rotation mode. This coupling results enable SR‐TENG to efficiently harvest low‐frequency mechanical energy from 0.3 to 5 Hz. Therefore, its bandwidth is about four times larger than that of CP‐TENG. The peak power density of SR‐TENG can reach 10.1 W m−3 at 1.8 Hz and 15.4 W m−3 at 5 Hz, respectively. Moreover, its durability is improved greatly due to its non‐contact working mode. Based on this SR‐TENG, several applications toward smart ocean, including a self‐powered and wireless hydrological information monitoring system, are demonstrated successfully. These strategies are very helpful to improve the bandwidth, the output performance, and the durability of TENGs.

Power Efficient Active Vibration Control Via Twin Rotor Damper in the Presence of Gravity

Abstract The twin rotor damper (TRD) is a device which primarily utilizes centrifugal forces for active vibration control. In its basic form, the TRD consists of two eccentric control masses rotating about two parallel axes. In a preferred mode of operation, the continuous rotation mode (CRM), the control masses rotate in opposite directions with a constant and equal angular velocity. This rotational motion results in a harmonic control force. In previous research, it has been shown that, in the CRM, the TRD can effectively damp vibrations while requiring little to no power from its actuators. However, this holds only for lateral vibrations, vibration perpendicular to gravitational forces, ergo gravity has no influence on the motion of the control masses. In this paper, the influence of gravity on the CRM is investigated analytically for the first time. It is shown that the TRD requires substantially greater power in the CRM to periodically lift the control masses against gravity. Subsequently, the CRM is augmented with an auxiliary function in the form of a Fourier series. This function is optimized such that the increase in power due to gravity is minimized while maintaining the damping performance of the TRD. The effects of augmenting the CRM are investigated, and a control algorithm is developed for the operation in the augmented CRM. In a numerical design example, it is shown that, with the augmented CRM, the power efficiency of the TRD can be regained at the cost of moderately reducing its damping performance.

Crystal structure of copper perchlorophthalocyanine analysed by 3D electron diffraction

Copper perchlorophthalocyanine (CuPcCl16, CuC32N8Cl16, Pigment Green 7) is one of the commercially most important green pigments. The compound is a nanocrystalline fully insoluble powder. Its crystal structure was first addressed by electron diffraction in 1972 [Uyeda et al. (1972). J. Appl. Phys. 43, 5181–5189]. Despite the commercial importance of the compound, the crystal structure remained undetermined until now. Using a special vacuum sublimation technique, micron-sized crystals could be obtained. Three-dimensional electron diffraction (3D ED) data were collected in two ways: (i) in static geometry using a combined stage-tilt/beam-tilt collection scheme and (ii) in continuous rotation mode. Both types of data allowed the crystal structure to be solved by direct methods. The structure was refined kinematically with anisotropic displacement parameters for all atoms. Due to the pronounced crystal mosaicity, a dynamic refinement was not feasible. The unit-cell parameters were verified by Rietveld refinement from powder X-ray diffraction data. The crystal structure was validated by many-body dispersion density functional theory (DFT) calculations. CuPcCl16 crystallizes in the space group C2/m (Z = 2), with the molecules arranged in layers. The structure agrees with that proposed in 1972.

Active Vibration Control of a Multi-Degree-of-Freedom System via Twin Rotor Damper

Abstract The twin rotor damper (TRD), an active mass damping device, is used for the vibration control of a multi-degree-of-freedom (MDOF) system of oscillators. A single TRD unit consists of two eccentric control masses rotating about two parallel axes. In its principle mode of operation, the continuous rotation mode (CRM), the control masses rotate with a constant angular velocity in opposite directions; producing a monofrequent harmonic control force in an energy and power efficient manner. Extensive research has shown the effectiveness of the TRD in the CRM for systems with a single dominate mode of vibration. In this paper, the application of a single and multiple TRD units operating in the CRM is investigated for the control of a MDOF system of oscillators. The influence of the monofrequent control force produced by the TRD on the MDOF system of oscillators is investigated analytically. Subsequently, the analysis is inverted and the influence of the MDOF system of oscillators on the TRD is studied, in particular its power efficiency and damping performance. Finally, the power efficiency and damping performance of the TRD for the control of a system with two modes of vibration is analytically compared with that of a conventional active mass damping (CAMD) device. It is shown that in most cases, the TRD achieves greater damping performance in a more power efficient manner than a conventional active mass damper of similar size and mass.

A compact rotary motor actuated by shape memory alloy mini springs

Shape memory alloys have recently gained attention for applications in motor driving components. The most expressive advantage of shape memory alloy components in that type of application is the high torque to motor weight ratio. Considering the importance of these studies, this article presents the design, manufacture, and theoretical and experimental analyses of a rotary motor driven by Ni–Ti shape memory alloy mini springs. The adopted motion mechanism allows the motor to run in continuous and bidirectional rotation mode, where speed and torque are determined by a drive sequence. A simplified analytical model was implemented, considering the thermomechanical characteristics of the shape memory alloy springs. Experimental tests with and without electrical drives were performed using properly designed electronic measurement instrumentation. The principal scientific contribution of this work is the demonstration of the motor’s functionality and torque generation. An energy density index of 1.41 × 10−3 Nmm/mm3 was attained, which is higher to those of other similarly constructed motors in the literature.

Aeroelastic flutter control of a bridge using rotating mass dampers and winglets

Flutter control of a bridge deck section using a combination of aerodynamic and mechanical measures, that is controllable winglets and rotating mass dampers, is considered. Deck and winglets are considered as flat plates for their aerodynamics. Self-excited wind forces are represented in the time domain using the Scanlan–Tomko model with Roger’s rational function approximation for flutter derivatives. Winglet rotation relative to the deck is the control input generated by the variable-gain output feedback controller that uses vertical and torsional displacements of the deck as measured outputs. Control using winglets enhances the critical speed to twice the uncontrolled flutter speed. Further attenuation of vertical response is obtained by using rotating mass dampers configured to provide only a resultant vertical force due to counter-rotating unbalanced masses. The rotors are driven at a constant angular speed, and start–stop criteria are applied. This generates additional vertical force on the deck that is mostly out of phase with its vertical velocity. It yields better control than the damper operated in a continuous rotation mode for a fixed number of cycles. A maximum reduction of 15% in root mean square vertical response is obtained when compared with control using winglets only.

Shaping Ability of Reciproc R25 File and Mtwo System Used in Continuous and Reciprocating Motion

Nickel-titanium (NiTi) instruments were designed to be used in continuous rotation mode with controlled speed and torque and a sequence of different sizes. The reciprocating motion was purposed to improve cyclic fatigue of rotary instruments if compared to the conventional rotation. The purpose of this work was to compare the shaping ability of Reciproc R25, Mtwo #25/0.06 used as a single file, and Mtwo sequence used in reciprocating motion and in continuous rotation. Forty-eight endodontic training resin blocks ISO 15, 2% taper, 7 mm radius, and a 60° angle of curvature were shaped with four different protocols. Group I (Rrsf) was shaped with Reciproc R25 used as a single file in a reciprocating motion. Group II (Mrsf) was shaped with Mtwo #25/0.06 used as a single file in a reciprocating motion. Group III (MSrec) was shaped with Mtwo sequence in reciprocating motion, and finally, group IV (MSrot) was shaped with the Mtwo sequence used in continuous rotation. Preoperative and postoperative images of the simulated canals were taken under standardized conditions and combined exactly. The amount of resin removed was determined at both the inner and outer sides of the canal curvature. The ability of the instruments to remain centered in the canal was determined by calculating a centering ratio. These data were analyzed statistically using two factors analysis of variance (ANOVA) with Bonferroni correction (Bonferroni post-hoc test). Group Rrsf produced a greater enlargement of the canal, especially on the outer side, in the apical and middle third (p < 0.05). Group MSrot produced a lower enlargement in the middle third (p < 0.05). Group Rrsf displayed a lower centering ratio in the apical third (p < 0.05). Group MSrot displayed a lower centering ratio in the coronal third (p < 0.05). The shaping of simulated canals using a sequence of instruments in continuous rotation resulted in a more centered preparation of the apical third. The reciprocating motion for all tested instruments produced a bigger enlargement of the canals. Reciprocating movement results in a more pronounced canal enlargement but appears to be less respectful of the original canal curvature and produces more apical transportation than a sequence of rotary NiTi files with the same ending apical size.

Twin rotor damper for the damping of stochastically forced vibrations using a power-efficient control algorithm

The twin rotor damper (TRD), an active mass damper, uses the centrifugal forces of two eccentrically rotating control masses. In the continuous rotation mode, the preferred mode of operation, the two eccentric control masses rotate with a constant angular velocity about two parallel axes, creating, under further operational constraints, a harmonic control force in a single direction. In previous theoretical work, it was shown that this mode of operation is effective for the damping of large, harmonic vibrations of a single degree of freedom (SDOF) oscillator. In this paper, the SDOF oscillator is assumed to be affected by a stochastic excitation force and consequently responds with several frequencies. Therefore, the TRD must deviate from the continuous rotation mode to ensure the anti-phasing between the harmonic control force of the TRD and the velocity of the SDOF oscillator. It is found that the required deviation from the continuous rotation mode increases with lower vibration amplitude. Therefore, an operation of the TRD in the continuous rotation mode is no longer efficient below a specific vibration-amplitude threshold. To additionally dampen vibrations below this threshold, the TRD can switch to another, more energy-consuming mode of operation, the swinging mode in which both control masses oscillate about certain angular positions. A power-efficient control algorithm is presented which uses the continuous rotation mode for large vibrations and the swinging mode for small vibrations. To validate the control algorithm, numerical and experimental investigations are performed for a single degree of freedom oscillator under stochastic excitation. Using both modes of operation, it is shown that the control algorithm is effective for the cases of free and stochastically forced vibrations of arbitrary amplitude.

Closed-Form Steady-State Response Solution of the Twin Rotor Damper and Experimental Validation

In previous research, the twin rotor damper (TRD), an active mass damper, was presented including control algorithms for monofrequent vibrations. In a preferred mode of operation, the continuous rotation mode, two eccentric masses rotate in opposite directions about two parallel axes with a mostly constant angular velocity. The resulting control force is harmonic. Within this paper, the steady-state response of a single-degree-of-freedom (SDOF) oscillator subjected to a harmonic excitation force with and without the TRD is studied. A closed-form solution is presented and validated experimentally. It is shown that the TRD provides damping to the SDOF oscillator until a certain frequency ratio is reached. The provided damping is not only dependent on the design parameters of the TRD but also depends on the steady-state vibration amplitude. The solution serves as a powerful design tool for dimensioning the TRD. The analytical closed-form solution is applicable for other active mass dampers.

Alternating the twin rotor damper between two modes of operation to eliminate small vibrations

In previous research, the twin rotor damper (TRD), an active mass damper, was presented. In a preferred, energy-efficient mode of operation, the continuous rotation mode, two eccentric control masses rotate with constant angular velocities about two parallel axes in opposite directions. The resulting centrifugal forces combine into a directed harmonic control force that can be used for the control of structural vibrations. In another, more power-demanding mode of operation, the swinging mode, both control masses oscillate about certain angular positions. For both modes of operation, corresponding control algorithms have been developed. Furthermore, it has been found that the continuous rotation mode is not efficient for the damping of small vibrations, whereas the swinging mode can bring small vibrations to rest. In this paper, a control algorithm is presented, which uses the continuous rotation mode for large vibrations and the swinging mode for small vibrations. To validate the control algorithm, the TRD is numerically and experimentally applied on a single degree of freedom oscillator. The efficiency of the algorithm is studied for free vibrations.

Switch Control of Twin Rotor Damper for Bridge Vibration Mitigation under Different Excitations

The twin rotor damper is one kind of novel active mass damper developed in recent years. Dynamic control force generated by the two eccentric masses of this device rotating with same angular velocity about parallel axes, can be used for controlling structural vibration. The main advantage of the twin rotor damper is its low energy consumption when operated in continuous rotation mode. A switch control scheme between two control modes using twin rotor damper is proposed in this paper to suppress bridge vibration under different excitations. The two control modes of the twin rotor damper, the rotational mode and the swinging mode, are adopted for wind excitation and earthquake excitation respectively. The control mode switch occurs if external excitation changes. Therefore, the functionality of this new AMD device is beneficial for its application in practical engineering. Numerical simulations are conducted to prove the validity of the twin rotor damper.

Active Vibration Control Using Centrifugal Forces Created by Eccentrically Rotating Masses

The twin rotor damper (TRD) is a newly developed active mass damper. It is presented here along with respective closed-loop control algorithms. The greatest advantage of the device is its low power demand when operated in a preferred mode of operation, the continuous rotation mode. In this mode, two eccentric masses rotate in opposite directions about two parallel axes with a mostly constant angular velocity. The resultant force is harmonic and can be used for the control of structural vibrations. To study the effect of the TRD on a single degree-of-freedom (SDOF) oscillator, various state variables are introduced and a feedback control algorithm is developed for the continuous rotation mode of operation. For reaching and leaving the continuous rotation mode, ramp-up and ramp-down trajectories are developed. These trajectories are designed such that the power and energy demand as well as the mechanical wear on the device are minimized. The feedback control algorithm is validated on a test setup. The damping effectiveness and the low power and energy demands encourage further investigation of the device under stochastic loading and comparisons with other active mass dampers.

Resistance to torsional failure and cyclic fatigue resistance of ProTaper Next, WaveOne, and Mtwo files in continuous and reciprocating motion: An in vitro study.

Aims:The purpose of this study was to evaluate the resistance to torsional failure and cyclic fatigue resistance of ProTaper Next (PTN), WaveOne, and Mtwo files in continuous and reciprocating motion.Settings and Design:Randomized control trial in a tertiary care setting.Subjects and Methods:A total of 10 new size 25.06 taper PTN X2, 25.06 taper Mtwo files, and 25.08 taper WaveOne primary files each was selected. A custom fabricated cyclic fatigue testing device with a 70° angle of curvature and 3 mm width; curvature starting at 6 mm from the tip was used. All instruments were rotated and reciprocated till fracture occurred and time till fracture of each instrument was recorded in seconds. For torsional failure testing 5 mm tip of each file was embedded in composite resin block and uniform torsional stresses (300 rpm, 2.0 Ncm) were applied repetitively by an endodontic motor with auto stop mode until file succumbed to torsional failure. Number of load applications leading to failure was recorded.Statistical Analysis Used:Data were analyzed using t-test for equality of means, Pearson correlation, and ANOVA test.Results:All the files showed superior resistance to cyclic fatigue in reciprocating motion when compared with continuous rotation mode. WaveOne primary files displayed maximum resistance to cyclic fatigue both in continuous and reciprocating motion. WaveOne primary files also demonstrated maximum resistance to torsional failure followed by PTN with Mtwo files exhibiting least resistance.Conclusions:Operating files in reciprocating motion enhances their cyclic fatigue resistance. WaveOne files showed maximum resistance to cyclic fatigue and torsional failure due to their cross-sectional diameter coupled M-Wire technology.

Geometric analysis of root canals prepared by single twisted file in three different operation modes.

Objective:The aim of this study was to evaluate and compare the effects of a single twisted file (TF) instrument in three different operation modes on the preparation of curved root canals in human molars and to explore a new possible method in canal shaping in the clinic setting.Materials and Methods:A total of 105 selected root canals with an angle of curvature ranging from 20° to 35° were divided into the following three groups with 35 samples each according to the different operation mode in canal preparation: “continuous rotation-500” (CR, 500 rpm), reciprocating movement-300 (RM-300 rpm) and CR-300 rpm. Root canals were prepared by single file (a size 25/0.06 TF). The pre- and post-instrumented images of the sections were scanned using a cone-beam computed tomography scanner to measure the root transportation and centering ratio. The data were evaluated at 1.5 mm, 3.0 mm and 6.0 mm positions from the apex. The significance level was set at P < 0.05.Results:The results showed a statistically significant difference in root transportation that was only found in cross-sections 3.0 mm from the anatomic apex between group “CR-500” and group “CR-300.” In addition, a significant difference in centering ratio was found between group “RM-300” and group “CR-300.” There was no significant difference in the two indices among the three groups at cross-sections 1.5 mm and 6 mm from the apex.Conclusions:Under the three conditions of this study, the continuous rotation mode has better shaping ability in root canal preparation than the RM mode when used with a TF single file (size 25/0.06).

Radiation damage in room-temperature data acquisition with the PILATUS 6M pixel detector

The first study of room-temperature macromolecular crystallography data acquisition with a silicon pixel detector is presented, where the data are collected in continuous sample rotation mode, with millisecond read-out time and no read-out noise. Several successive datasets were collected sequentially from single test crystals of thaumatin and insulin. The dose rate ranged between ∼ 1320 Gy s(-1) and ∼ 8420 Gy s(-1) with corresponding frame rates between 1.565 Hz and 12.5 Hz. The data were analysed for global radiation damage. A previously unreported negative dose-rate effect is observed in the indicators of global radiation damage, which showed an approximately 75% decrease in D(1/2) at sixfold higher dose rate. The integrated intensity decreases in an exponential manner. Sample heating that could give rise to the enhanced radiation sensitivity at higher dose rate is investigated by collecting data between crystal temperatures of 298 K and 353 K. UV-Vis spectroscopy is used to demonstrate that disulfide radicals and trapped electrons do not accumulate at high dose rates in continuous data collection.

HEROShapers®: the adapted pitch concept

The adapted pitch concept involves varying the pitch and the length of the cutting portion as a function of the taper of the instruments. By modifying these parameters, it is possible to select the instrument with the strength, efficacy, flexibility, and taper best suited for the root canal being prepared.In the HEROShaper® sequence, instruments with a 0.06 taper are used to prepare and enlarge the coronal and middle thirds of the canal. These instruments have a longer pitch for enhanced flexibility and dentine cutting efficacy. The removal of dentinal chips is facilitated and the tendency to screw in is reduced. Instruments with a 0.04 taper are used to prepare the apical portion because they have a shorter pitch and cutting portion (12 mm), which makes them stronger and more flexible. They can thus negotiate apical curvatures without deviating from the initial canal axis.The files are used in a continuous rotation mode (450–600 r.p.m.) to progressively prepare the root canal (crown‐down). The sequences are selected based on the difficulty of the original canal shape.