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Real-time condition monitoring of various types of machinery using sensor technology has gained significant importance in recent years. However, relying on batteries to power these sensors proves to be sub-optimal, as it necessitates regular charging or replacement. To address this, harvesting waste energy from ambient sources emerges as a more efficient alternative. Everyday applications like vehicle wheels, fans, and turbines present ambient sources of waste rotational energy. In this study, we propose a novel rotational energy harvester design that converts rotational energy into linear energy. This linear energy impacts a piezoelectric disk, generating an electric potential. Through simulations, the expected electric potential at varying frequencies was evaluated. Subsequently, experimental tests were conducted by connecting the harvester to a rectifier for AC-to-DC signal conversion and an oscilloscope for voltage measurement. A DC motor replicated the rotational motion at the frequencies from the simulation, and the power output was measured. Using the power transfer theorem, simulation and experimental power outputs were calculated, resulting in values of 188, 513, and 1293 μW and 88.89, 336, and 923 μW, respectively. These results reveal that the designed harvester is competitive with those of existing rotational energy harvester designs, demonstrating the promising potential of this novel harvester. [ABSTRACT FROM AUTHOR]

We evaluate the surface energy ( E s ± ), rotational energy ( E r ± ) and electromagnetic energy ( E em ± ) for a Kerr-Sen black hole (BH) having the event horizon ( H + ) and the Cauchy horizon ( H - ). Interestingly, we find that the sum of these three energies is equal to the mass parameter i.e. E s ± + E r ± + E em ± = M . Moreover in terms of the scale parameter (ζ ±) , the distortion parameter ( ξ ± ) and a new parameter (σ ±) which corresponds to the area ( A ± ), the angular momentum (J) and the charge parameter (Q), we find that the mass parameter in a compact form E s ± + E r ± + E em ± = M = ζ ± 2 1 + 2 σ ± 2 1 - ξ ± 2 which is valid through all the horizons ( H ± ). We also compute the equatorial circumference and polar circumference which is a gross measure of the BH surface deformation. It is shown that when the spinning rate of the BH increases, the equatorial circumference increases while the polar circumference decreases. We show that there exist two classes of geometry separated by ξ ± = 1 2 in Kerr-Sen BH. In the regime 1 2 < ξ ± ≤ 1 2 , the Gaussian curvature is negative and there exist two polar caps on the surface. While for ξ ± < 1 2 , the Gaussian curvature is positive and the surface will be an oblate deformed sphere. Furthermore, we compute the exact expression of rotational energy that should be extracted from the BH via Penrose process. The maximum value of rotational energy which is extractable should occur for extremal Kerr-Sen BH i.e. E r + = 2 - 1 J 2 . [ABSTRACT FROM AUTHOR]

We investigated classical and quantum rotational partition functions, rotational energies and rotational entropies for asymmetric-top molecules in a canonical system within a wide range of temperatures under the rigid rotor approximation. We then derived the temperature, T limit , below which classical approach is not valid, and the complex quantum approach is strongly recommended. This temperature certainly increases with the inertia moment of the molecule and follows a power function when rotational partition functions are considered. As for linear-, spherical- and symmetric-top molecules, quantum approach is not needed at all for energetic rotational parameters, whatever the temperature for asymmetric-top molecules. Therefore, there is no real frontier between the classical and quantum approaches when energetic rotational parameters are concerned, though the frontier is naturally a bounded decreasing sequence converging to zero when rotational partition functions are rather concerned. Particularly, classical approach fails describing rotational partition functions for light molecules or molecules at low temperatures. Moreover, all the closed-form expressions proposed in the whole literature fail drastically approaching quantum and exact results for light molecules or molecules at low temperatures. In regard to the importance of partition functions in the evaluation of rate constants for chemical reactions and accurate intensities lines in spectroscopy, we proposed new accurate and simple analytic expression of the rotational partition functions of asymmetric-top molecules, valid at all temperatures. [ABSTRACT FROM AUTHOR]

We compute the surface energy ( E s ± ), the rotational energy ( E r ± ) and the electromagnetic energy ( E em ± ) for Newman-Unti-Tamburino (NUT) class of black hole having the event horizon ( H + ) and the Cauchy horizon ( H - ). Remarkably, we find that the mass parameter can be expressed as sum of three energies i.e. M = E s ± + E r ± + E em ± . It has been tested for Taub-NUT black hole, Reissner-Nordström-Taub-NUT black hole, Kerr-Taub-NUT black hole and Kerr-Newman-Taub-NUT black hole. In each case of black hole, we find that the sum of these energies is equal to the Komar mass. It is plausible only due to the introduction of new conserved charges i. e. J N = M N (where M = m is the Komar mass and N = n is the gravitomagnetic charge), which is closely analogue to the Kerr-like angular momentum parameter J = a M . [ABSTRACT FROM AUTHOR]

[Display omitted] • The TENG expands rotational energy harvesting for the downhole environment. • R-TENG's flexible contact construction reduces damage to the TENG over long periods. • R-TENG can be used for speed monitoring with an error of less than 2%. • The hybrid nanogenerator can continuously power tiny electronic devices. Due to the complex working environment of the downhole, it is cumbersome and economically costly to power the sensing system using traditional methods. It is also crucial to monitor the speed of downhole motors. In this paper, a flexible-contact hybrid nanogenerator is proposed. It mainly collects the rotational energy of motors to provide power for other sensors and senses the speed of downhole motors. Firstly, the overall structural design of the hybrid nanogenerator is carried out. The hybrid nanogenerator consisting of an electromagnetic generator (EMG) and a rotating triboelectric nanogenerator (R-TENG) to complement each other's strengths are structurally optimized and performance tested separately. The maximal voltages of the EMG and R-TENG are 14.8 V and 230 V, and the maximal currents are 11 mA and 28 μA, respectively. Meanwhile, R-TENG errors are within 2 % when used for rotational speed sensing. The hybrid nanogenerator can charge a 100 μF capacitor to 6 V in 2 s, which has good charging performance and can power electronic devices such as Bluetooth thermo-hygrometer. The experiment findings indicate that the hybrid nanogenerator can not only complete the rotational speed sensing of the motors without an external power supply but also act as an energy harvester to collect the rotational energy of the motors and supply power to other tiny electronic devices downhole. It is a new type of power supply more suitable for downhole working conditions and provides a new idea of power supply and sensing downhole. [ABSTRACT FROM AUTHOR]

We investigated classical and quantum rotational partition functions, rotational energies and rotational entropies for linear-, spherical- and symmetric-top molecules in a canonical system within a wide range of temperatures under the rigid rotor approximation. We then derived the temperature, T limit , below which classical approach is not valid and the complex quantum approach is strongly recommended. This temperature certainly increases with the inertia moment of the molecule and follows an exact combination of three decreasing exponential functions for linear- and spherical-top molecules when rotational partition functions are considered. However, another good news is that contrary to what is being commonly known, quantum approach is not needed at all for energetic rotational parameters, whatever the temperature. Therefore, there is no real frontier between the classical and quantum approaches when energetic rotational parameters are concerned, though the frontier is naturally a bounded decreasing sequence converging to zero when rotational partition functions are rather concerned. Particularly, classical approach (as implemented in several quantum chemistry computational codes) fails describing rotational partition functions for light molecules or molecules at low temperatures. As a matter of fact, we noted that as far as the partition function is concerned, T limit = 100 3 θ for linear-top molecules and T limit = 25 θ for spherical-top molecules, with θ the characteristic rotational temperature. Moreover, all the closed-forms expressions proposed in the whole literature fail drastically approaching quantum and exact results for light molecules or molecules at low temperatures. In regard of the importance of partition functions in the evaluation of rate constants for chemical reactions and accurate intensities lines in spectroscopy, we proposed two new accurate and simple analytic expressions of the rotational partition functions of linear-top and spherical-top molecules, valid for light molecules or at low temperatures. These new closed-forms reproduce excellently the exact values and are exceptionally better than previous proposed closed-forms in the literature, and they are therefore strongly recommended for light molecules or at low temperatures. [ABSTRACT FROM AUTHOR]

• A novel m-shaped variable reluctance energy harvesting structure is proposed. • Output power is optimized under size constraints through a numerical method. • Good agreements between numerical simulations and experiments are demonstrated. • Sufficient output power can be harvested even under low rotating speeds. The variable reluctance principle can be used to convert rotational kinetic energy into electrical energy, creating a Variable Reluctance Energy Harvester (VREH) based on electromagnetic induction. This can be used to implement self-sustaining wireless sensors in rotating applications. In this paper, we present and investigate a novel design of a VREH with high volumetric power density that targets low-speed rotating applications. The design uses an m-shaped pole-piece and two opposing magnets. We theoretically analyze key design parameters that influence the VREH's output power, and relate these parameters to geometrical design factors of the proposed structure. Key design factors include the coil height, the permanent magnet height and the tooth height. A method based on numerical simulations is introduced, enabling to determine the optimal geometrical dimensions of the proposed structure under given size-constraints. The results demonstrate that the method leads to optimal structure configurations, which has been evaluated for different cases and is verified experimentally. Good agreement between numerical simulations and experiments are reported with deviations in output power estimation below 3%. The optimized m-shaped VREH, moreover, provides output power levels sufficient for wireless sensor operation, even in low-speed rotating applications. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are harmful and persistent organic pollutants. The influence of chiral PCBs acts mainly on the different enantiomer fraction, bioaccumulation and even degradation in environmental media. Solvents and temperatures existed almost everywhere during the analysis of extraction, purification, concentration and detection, which was often underestimated in previous studies. In our study, the configuration stability of the chiral PCBs was examined from solvent and temperature aspects. Transformation phenomena for the analytic stereoisomer monomers of PCB45, PCB95, and PCB149 affected by temperature were observed. We demonstrated that higher inlet temperatures could increase the sensibility for the low-concentration environmental samples, resulting in isomerization of chiral PCBs. Real rice samples were used to verify our analysis method. Combined with density functional theory, we verified the mechanism of isomer conversion with various numbers and sites of the -Cl substituent. PCBs with tetra- ortho substituents (2, 2′, 6, 6′) were relatively stable and showed the highest rotational barriers (E a) at approximate 240 kJ mol−1. Others with trio- ortho substituents (2, 2′, 6/6′) showed E a from 170 to 190 kJ mol−1, whose enantiomeric fractions would be affected by temperature during the analysis process for environmental detection. The method we developed was a promising means to understand the mechanism of isomerization and to predict stabilities of chiral PCBs. • The effects of solvents on PCBs were very small. • The loss of isomer conversion on GC was underestimated. • How to detect low concentration environmental samples. • With Arrhenius equation, we could obtain the precise revised EF s. • The mechanism of enantiomer conversion with substituent effects. [ABSTRACT FROM AUTHOR]

The rotational and vibrational energies and the electric transition probability B (E2) of the even–even 228–232Th isotopes are studied empirically in framework of a nuclear phenomenological approach by using the SU(3) dynamical symmetries of the Interacting Boson Model-1 (IBM-1). Furthermore, the potential energy surfaces for these isotopes are plotted as functions of the deformation parameters β and γ. Moreover, we introduce empirical fit formulas for rotational and vibrational energies, which used to calculate these energies for the thorium isotopes. The obtained results by applying the IBM-1 and the authors’ formulas are in good agreement with the corresponding experimental data for most of the nuclear states. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for power generation from rotating machines in textile mills using externally coupled repulsive magnets and a new stepped DC coupled Quasi Z-inverter. Power is obtained as a byproduct of the effective harnessing of rotational energy with the use of repulsive magnets. This derived power is stored in a battery arrangement and is retrieved, buck/boosted, and converted to multilevel AC voltage with the new stepped DC coupled quasi Z-inverter. The proposed inverter is powered by isolated voltage sources, uses fewer switches, and produces less distortion in the resulting multilevel voltage compared to its counterpart, and thus reduces the fiter requirements. The derived AC power from the system can be used for light-load applications in textile mills, thus compensating for the energy demands. Simulation of the entire proposed setup is performed in MATLAB/Simulink and the results are presented. The repulsive force produced by the magnets is assessed with K & J Magnet software. To validate the simulation, experimentation is done using rotating machines available in the laboratory. The prototype model of the stepped DC coupled quasi Z-inverter is used to study the performance of the system and the results are evaluated. The optimum modulation index is identified for different numbers of sources at the input. [ABSTRACT FROM AUTHOR]

Core formation by gravitational segregation allegedly released sufficient interior heat to melt the Earth. Analysis of the energetics, which compare gravitational potential energy ( U) of a fictitious, homogeneous reference state to Earth's current layered configuration, needs updating to correct errors and omissions, and to accommodate recent findings: (1) An erroneous positive sign was used for U while maintaining the reference value of 0 at infinity, which results in an incorrect sign for Δ U, which is crucial in determining whether a process is endothermic or exothermic. (2) The value of U for Earth's initial state is uncertain. (3) Recent meteorite evidence indicates that core formation began before the Earth was full-sized, which severely limits Δ U. (4) Inhomogeneous accretion additionally reduced Δ U. (5) The potentially large effect of differential rotation between the core and the mantle was not accounted for. (6) Entropy changes associated with creating order were neglected. Accordingly, we revise values of U, evaluate uncertainties, and show that Δ U was converted substantially to configurational energy ( TΔ S). These considerations limit the large sources of primordial heat to impacts and radioactivity. Although these processes may play a role in core formation, their energies are independent of gravitational segregation, which produces order and rotational energy, not internal heat. Instead, gravitational segregation promotes planetary cooling mainly because it segregates lithophilic radioactive elements upward, increasing surface heat flux while shortening the distance over which radiogenic heat diffuses outwards. [ABSTRACT FROM AUTHOR]

Within the framework of photon emission from electronic transitions, electric quadrupole emission in diatomic molecules is a relevant issue. In this respect, we present a matrix formalism to treat electric quadrupole emission in oxygen. As a matter of fact, within the above context, we derive an analytical approach by expressing the quantized rotational energy of an involved oxygen molecule as a dyadic-tensor product of two relevant matrices. Furthermore, in connection with the formalism in question, we discuss aspects associated with the matrix elements relative to the emission intensity and line strength. [ABSTRACT FROM AUTHOR]

Kinetic energy spectra from the mesoscale numerical weather prediction (NWP) model ALADIN with horizontal resolution 4.4 km are split into divergent and rotational components which are then compared at horizontal scales below 300 km and various vertical levels. It is shown that about 50% of kinetic energy in the free troposphere in ALADIN is divergent energy. The percentage increases towards 70% near the surface and in the upper troposphere towards 100 hPa. The maximal percentage of divergent energy is found at stratospheric levels around 100 hPa and at scales below 100 km which are not represented by the global models. At all levels, the divergent energy spectra are characterised by shallower slopes than the rotational energy spectra, and the difference increases as horizontal scales become larger. A very similar vertical distribution of divergent energy is obtained by using the standard ALADIN approach for the computation of spectra based on the extension zone and by applying detrending approach commonly used in mesoscale NWP community. [ABSTRACT FROM AUTHOR]

Abstract: Stochastic classical trajectory simulations were used to study the efficiency of the energy exchange at the gas–liquid interface. Self-assembled monolayers (SAM) of long-chain functionalized molecules were used to mimic the liquid surface. Since the molecules in the monolayers are anchored by only one end, they retain some of the mobility that they have in the liquid but lose all their fluidity. The corrugation of the surface and the stiffness of the interface were tuned by varying the length of the molecules in the monolayers. The use of longer molecules leads to increased corrugation of the surface and provides additional dissipation channels that promote more efficient momentum and energy accommodation, increase the translational–rotational energy interconversion and enhance trapping. However, this “length effect” appears to saturate, as no further significant changes are observed in those properties when the monolayer''s molecules''s length is elongated from six to nine carbons. This saturation effect suggests that, even though monolayers can provide some of the mobility observed in liquid surfaces, they lack the energy dissipation channel provided by the fluidity of the liquid. [Copyright &y& Elsevier]

The supersonic free-jet expansion technique is being used in different fields of research in physics, and physical chemistry to study vibrational and rotational molecular structures in ground and excited electronic energy states. The supersonic beam technique exploits a source of monokinetic, rotationally and vibrationally cold van der Waals (vdW) molecules that are very weakly bound in their ground electronic states. In this article we review experiments at the Jagiellonian University in Kraków (Poland) in which the supersonic free-jet beam serves as a source of ground-state vdW molecules in studies of neutral--neutral interactions between 12-group metal (Me = Zn, Cd, Hg) and 18-group noble gas (Ng = He, Ne, Ar, Kr, Xe) atoms. The experiments lead to determination of spectroscopical characteristics and interatomic potentials of MeNg and Me2 molecules, allowing determination of distinct trends in the Me--Ng and Me--Me interactions in different regions of internuclear separation. The determined interatomic potentials are also used in designing mechanisms of internal vibrational cooling of molecules photoassociated in magneto-optical traps. Recently, versatility of supersonic beams is confirmed in quantum information where the technique is planned to be used to create pairs of entangled atoms in experiments dedicated for testing of Bell's inequality for atoms. A purpose of the experiment -- which is in a preparational stage in our laboratory -- is to create pairs of entangled cadmium atoms with regard to their nuclear spin orientations. It is planned to be achieved in supersonic molecular beams of cadmium dimers using two dye-laser pulses and stimulated Raman process leading to a controlled photodissociation of the molecule. [ABSTRACT FROM AUTHOR]

Restitution coefficients are used to quantify the energy dissipation upon impact when predicting rock fall events. These coefficients can be determined in situ or in the laboratory. In any case, the usual values for the normal restitution coefficient k are below unity. Values greater than one are quite rare, seen as unusual and barely explained. Previous experimental research conducted in Australia has shown consistent and systematic values of the normal restitution coefficient greater than one. This was tentatively explained by a combination of parameters such as low impacting angle, rotational energy and block angularity. The study presented in this paper aims at (1) identifying the critical parameters conducting to high k values and (2) at explaining the associated motion mechanisms. The objective was reached with values of k up to almost 2. In addition, the study has confirmed the significance of low impacting angle, rotational energy and block shape in this context. [ABSTRACT FROM AUTHOR]

Abstract: In the present work we have investigated the gas phase reactivity of protonated urea after collision with the diatomic inert gas N2, by studying the energy transfer and fragmentation induced by collisions. We first developed an analytical pair potential to describe the interaction between the projectile and the ion, and then performed QM/MM direct chemical dynamics simulations of the collision between the projectile and protonated urea in its two most stable isomers. In particular, the effect of the diatomic projectile, and the role of its initial rotational state, were compared with the fragmentation and energy transfer obtained previously (J. Phys. Chem. A 2009, 113, 13853) for the monoatomic projectile Ar. The diatomic projectile was found to be less efficient in energy transfer compared to the monoatomic projectile. In addition, rotational activation of UreaH+ is dependent on the initial rotational quantum number of N2. Finally, we investigated the UreaH+ gas phase reactivity as a function of its rovibrational activation by means of chemical dynamics simulations where the initial structure for the simulations is the transition state (TS) that the system can reach after collisional activation of the most stable isomer. The simulation time-length is not able to directly access this TS from the most stable isomer since its lifetime is notably longer, of about two order of magnitude in time. [Copyright &y& Elsevier]

Abstract: We investigated the heat-induced cis/trans isomerization of double bonds in monounsaturated lipids. When triolein (9-cis, 18:1) was heated around 180°C, small amounts of isomerization products were obtained depending on the heating period. The heat-induced isomerization of triolein was considerably suppressed by the addition of different antioxidants or under nitrogen stream, and these additives simultaneously inhibited the thermal oxidation of double bonds in triolein. Therefore, an intermediate of the thermal oxidation reaction might be responsible for the heat-induced isomerization of the double bonds in triolein. The thermodynamics of the heat-induced isomerization of triolein (9-cis, 18:1) and trielaidin (9-trans, 18:1) were investigated using Arrhenius plot. The Arrhenius activation energies of cis double bonds in triolein and trans double bonds in trielaidin were 106kJ/mol and 137kJ/mol, respectively. The calculated internal rotational barrier heights of these double bonds were similar to those of the double bond of 2-butene radical and significantly lower than those of non-radicalized double bonds in 2-butene. These results suggest that heat-induced cis/trans isomerization of triolein and trielaidin occurs mainly through the formation of radical species, which are the intermediates produced during thermal oxidation. The activation energy difference between the two forms suggests that trans trielaidin radicals are more stable than cis triolein radicals. The high thermodynamic stability of the trans double bonds in lipid radicals would influence the population of cis and trans isomers in edible oils and contribute to slight accumulation of trans-18:1 isomers during heating or industrial processing. [ABSTRACT FROM AUTHOR]

Abstract: The internal energy distribution of NO and N2 scattering from a defective surfaces has been studied using classical molecular dynamics. Stochastic trajectory simulations were used to calculate the final rotational excitation, angular distribution and trapping probabilities of N2 and NO scattering from clean Ag(111) surfaces, with adatoms and with vacancies. Calculations reproduce well the experimental results for NO and N2 scattering from clean surfaces. NO undergoes more extensive rotational excitation than N2 on clean and defective surfaces. Scattering is more inelastic on defective surfaces and adatoms defects appear to promote rotational excitation more efficiently than vacancies. Trapping exhibits a complex behavior. Dynamical corrugation causes trapping of NO on clean Ag(111) to exhibit a “crossover” behavior. That is, the value of n in the standard functional dependence of trapping on the incident energy, E i cos n θ i , switches sign as the incident energy increases. This behavior is also observed in the case of N2 scattering from a surface with adatoms, but in this case is caused by the static corrugation. It appears that the breaking of the 2-D symmetry of the surface (i.e. static corrugation) compensates for the lack of anisotropy in the interaction potential (i.e. dynamical corrugation) for N2/Ag(111). Adatom defects increase trapping for NO molecules impinging on the surface with glancing trajectories while vacancies have the opposite effect. [Copyright &y& Elsevier]

This paper quantifies the capability of providing a short-term excess active power support of a commercial multi-megawatt variable speed wind turbine (VSWT) and generalizes the findings by considering different wind turbine (WT) physical parameters in a wider range from the example case. The paper also identifies some possible applications of it, in particular, in a hydro dominated system. To be able to quantify the system characteristic, a delay model of the studied hydro system is developed. Due to the fact that the initial power surge of a hydro turbine is opposite to that desired, the short-term extra active power support from a wind farm (WF) could be beneficial for a hydro dominated system in arresting the initial frequency fall, which corresponds to an improvement in the system temporary minimum frequency (TMF). The improvements in the TMF are calculated by using both the developed delay model and a detailed model, and the results show good agreement. It is shown that the WT under consideration can provide a 0.1 pu extra active power support for 10 s quite easily which is twice the Hydro-Québec requirement. [ABSTRACT FROM AUTHOR]

Abstract: Addition of organometallic reagents to optically active methyl 1-(2-methoxycarbonyl-6-trifluoromethylphenyl)pyrrole-2-carboxylate provided the corresponding tetrasubstituted diols and/or pyrrolo[1,2-a]benzoxazepines as pure enantiomers or racemates depending on the organometallic reagents used. Rotational energy barriers around the interconnecting C–N bonds were estimated by molecular modeling calculations and NMR measurements with the aim of clarifying the stereochemical stability order of the new atropisomeric compounds. NMR methods for the determination of the enantiomeric purity of the new compounds are proposed. [Copyright &y& Elsevier]

The 1:1 intermediates generated by the addition of triphenylphosphine to dialkyl acetylenedicarboxylates were trapped by an NH-acidic compound such as phenothiazine to give dialkyl-2-(phenothiazino)-3-(triphenylphosphoranylidene)-butanedioates in high yields. The ylide moiety of these compounds was strongly conjugated with the adjacent carbonyl group, and rotation around the partial double bond in the (E) and (Z) geometrical isomers was slow on the NMR time scale. The dynamic effects in the ylide moiety were investigated by 1H NMR. They are attributed to a restricted rotation around the carbon–carbon double bond. [ABSTRACT FROM AUTHOR]

Abstract: Previous theoretical work on energy cluster formation at high rotational excitation in the vibrational ground state of PH3 [S.N. Yurchenko, W. Thiel, S. Patchkovskii, P. Jensen, Phys. Chem. Chem. Phys. 7 (2005) 573] is extended to BiH3 and SbH3. By means of variational calculations of the rotation–vibration energies based on ab initio potential energy surfaces, we analyze the rotational energy clustering of BiH3 and SbH3 at J ⩽70 for a number of vibrational states. We show that BiH3 and SbH3, with their pronounced local mode behaviour, exhibit cluster formation already at moderate rotational excitation. In addition, owing to its quasi-spherical-top character, BiH3 undergoes an imperfect bifurcation at high J. This gives rise to an energy cluster type not present in PH3 and SbH3. We present a semi-classical approach to the construction of the rotational energy surfaces for vibrationally excited states. [Copyright &y& Elsevier]

A rotary type frequency converter using two sets of adjustable speed generators/motors is expected to be applied at the interconnections between 50 Hz and 60 Hz power systems in Japan. The rotary type frequency converter can work not only as a power interchanger, but also as a power system stabilizer by effectively utilizing energy stored in rotors. In this paper, we investigate how the rotary type frequency converter affects power system dynamics. Since shaft torsional oscillation and slow response due to mechanical connections are inevitable and may lead to instability in power systems, we also present some countermeasures and control schemes to handle such inherent problems, and to improve the performance of power system dynamics. Control performance and effectiveness is examined for a test model system by digital transient simulation. [ABSTRACT FROM AUTHOR]

While sliding-mode triboelectric nanogenerators (S-TENGs) have been considered as one of the most promising devices for rotational energy harvesting, their inherently poor durability has been a serious bottleneck for applications. Herein, we report a three-dimensional kirigami TENG as a highly efficient and durable rotational energy harvesting device. The kirigami TENG consisted of cube-shaped paper, aluminum (Al) foil electrode and polytetrafluoroethylene (PTFE) polymer film, and converted rotational motion into multiple folding-unfolding vibrations. The rotation-folding (R-F) kirigami TENG generated an open-circuit voltage of 31 V, a short-circuit current of 0.67 μA and an instantaneous power (power density) of 1.2 μW (0.13 μW/cm2) at 200 rpm, which was sufficient to turn on 25 light-emitting diodes and a thermo-hygrometer. The triboelectric outputs of the R-F kirigami TENG were only slightly decreased even after 288,000 continuous rotations, i.e., the output remained at 86% of its initial value. This work demonstrates that an R-F kirigami TENG could be a plausible candidate to efficiently harvest various forms of rotational energy with a long-term durability. [ABSTRACT FROM AUTHOR]

Abnormal falls in public places have significant safety hazards and can easily lead to serious consequences, such as trampling by people. Vision-driven fall event detection has the huge advantage of being non-invasive. However, in actual scenes, the fall behavior is rich in diversity, resulting in strong instability in detection. Based on the study of the stability of human body dynamics, the article proposes a new model of human posture representation of fall behavior, called the "five-point inverted pendulum model", and uses an improved two-branch multi-stage convolutional neural network (M-CNN) to extract and construct the inverted pendulum structure of human posture in real-world complex scenes. Furthermore, we consider the continuity of the fall event in time series, use multimedia analytics to observe the time series changes of human inverted pendulum structure, and construct a spatio-temporal evolution map of human posture movement. Finally, based on the integrated results of computer vision and multimedia analytics, we reveal the visual characteristics of the spatio-temporal evolution of human posture under the potentially unstable state, and explore two key features of human fall behavior: motion rotational energy and generalized force of motion. The experimental results in actual scenes show that the method has strong robustness, wide universality, and high detection accuracy. [ABSTRACT FROM AUTHOR]

High-resolution coherent multidimensional spectroscopy is a technique that automatically sorts rotationally resolved peaks by quantum number in 2D or 3D space. The resulting ability to obtain a set of peaks whose J values are sequentially ordered but not known raises the question of whether a method can be developed that yields a single unique solution that is correct. This paper includes a proof based upon the method of combined differences that shows that the solution would be unique because of the special form of the rotational energy function. Several simulated tests using a least squares analysis of simulated data were carried out, and the results indicate that this method is able to accurately determine the rotational quantum number, as well as the corresponding Dunham coefficients. Tests that include simulated random error were also carried out to illustrate how error can affect the accuracy of higher-order Dunham coefficients, and how increasing the number of points in the set can be used to help address that. [ABSTRACT FROM AUTHOR]