4th Mode Research Articles

FINITE ELEMENT MODELLING FOR ELECTRIC FIELD DISTRIBUTION AROUND POSITIVE STREAMERS IN OIL

Electric field distribution of positive streamers during propagation was determined with the finite element method by using COMSOL multiphysics. Modelling was performed at 210 kV and 270 kV. The geometrical shape of streamers was modelled with cylinder and sphere for the case of 210 kV while a growing cylinder was used for streamer propagation at 270 kV. In addition, a spherical model was used for determining the correlation between streamer branching and the electric field. It is obtained from the simulation results that the 2nd mode streamers has the electric field at channel tips of about 0.1 MV/cm while 8.3 MV/cm was received for the 4th mode streamers. The simulation results also reveal that the shielding effect resulting from streamer branching significantly reduces the electric field at the channel tips, and the shielding effect disappears with the angle a between channels is about 30o-60o depending on the size of streamer envelope. The hypothesis on correlation among velocity, streamer branching and electric field is suggested.

ГЕНЕЗИС КОНЦЕПЦИИ УПРАВЛЕНИЯ ЧЕЛОВЕЧЕСКИМИ РЕСУРСАМИ

Since there is no unified scientific periodization of the development of the theory of human resource management, the author's version is proposed. As a basis for periodization, we take the stages of development of the society that are technological modes (according to Kondratiev). We highlight the preparatory period (the emergence of positions and job functions), which corresponds to the 1st and 2nd technological modes; the concept of the "use of labor resources", which appeared during the period of the 3rd technological mode; the concept of "personnel management", which is in the 4th technological mode; the concept of "human resource management" existed in the 5th technological mode, and the concept of "human resources" that appeared today in the 6th technological mode. The article compares the implementation of the concepts in the West and in Russia, reveals the reasons for the existing differences. The article gives data that show great differences in attitude towards personnel between Russian enterprises, which indicates the presence of all concepts of human resource management in management practice. Tasks are set for domestic personnel management services to maximize the compression of the “residence” time of the concepts implemented in the West; or the implementation of a revolutionary “leap” that will balance our enterprises with foreign ones.

Characterization of magnetoelastic ribbons as vibration sensors based on the measured natural frequencies of a cantilever beam

In the current work, magnetoelastic ribbons of metallic glass alloy known as Metglas 2826MB are fully characterized as vibration sensors. The characterization involves seven different sensor parameters such as the frequency response, linearity, signal to noise ratio (SNR), quality factor, stability, repeatability and sensitivity. Two experimental setups where used for the characterization process, one for the frequency response parameter (FR setup) and one for the rest of the parameters (NFR setup). The frequency response parameter was examined for two different states of the ribbon, the non-annealed and the annealed states, and better characteristics were revealed for the annealed state. In the NFR setup, a cantilever beam (CB) was used as a vibrating platform, with two annealed Metglas ribbons attached on its free end using a double-sided tape. The 2nd, 4th and 6th bending modes of the CB were used for the characterization process. Concerning linearity, the ribbons showed an extremely linear behavior, with an average value for the adjusted R-square being Ra2=0.99995. The SNR and Quality factor parameters were studied versus the DC magnetization field of the Metglas ribbons (bias field), and the results showed that the implementation of a DC magnetic field increased the strength of the detectable signal without reducing its quality. In particular, the improvement on the detectable signal for the 2nd, 4th and 6th bending modes was 151%, 41% and 27%, respectively. The ribbons stability was examined within a time period of 2 h, with the average percentage deviation from the mean frequency being as small as 0.005% and the average change of the frequency with time as small as Fa = (1.1 ± 0.4) × 10−4 Hz/min. As for the repeatability parameter, the ribbons were subjected to alternating biasing and showed an excellent behavior during repetition cycles, with the average percentage deviation from the reference state being 0.004%, 0.002% and 0.003% for the 1st, 2nd and 3rd cycle, respectively. The last parameter studied was the sensitivity of the ribbons in detecting the shift of the natural frequencies versus CB stiffness, when a crack is introduced. Each bending mode revealed a different value of sensitivity, with the 2nd mode having the lowest and the 6th mode having the highest. The average sensitivity value among the three modes was calculated to be Sa = (38 ± 1) × 10−3 Hz/(N m−1).

Resonance of baroclinic waves in the tropical oceans: The Indian Ocean and the far western Pacific

The Indian Ocean has a particularity, its width is close to half the wavelength of a Rossby wave of biannual frequency, this coincidence having been capitalized on by several authors to give the observations a physical basis. The purpose of this article is to show that this is not the case since the resonance of tropical baroclinic waves occurs in all three oceans. This is because the westward-propagating Rossby wave is retroflexed at the western boundary to form off-equatorial Rossby waves dragged by countercurrents before receding and turning back as a Kelvin wave. Thus a quasi-stationary baroclinic wave is formed, whose mean period is tuned to the forcing period. Two independent basin modes resonantly forced are highlighted – 1) a nearly symmetric zonal 1/2-yr period Quasi-Stationary Wave (QSW) that is resonantly forced by the biannual monsoon. It is formed from first baroclinic mode equatorial-trapped Rossby and Kelvin waves and off-equatorial Rossby waves at the western antinode. This QSW controls the Equatorial Counter Current at the node. The Indian Ocean Dipole (IOD) results from a subharmonic mode locking resulting from the coupling of this QSW and the 2nd, 3rd and 4th baroclinic modes - 2) a 1-yr period QSW formed from an off-equatorial baroclinic Rossby wave, which is induced from the southernmost current of the Indonesian Throughflow through the Timor passage, propagating in the southern and northern hemispheres: the drivers are south-easterlies in the southern hemisphere and monsoon wind in the northern hemisphere.

THz radiation from a high-order mode sheet beam extended interaction oscillator with staggered grating

A circuit design of sheet-beam extended interaction oscillator (SB-EIO) with an overmoded staggered grating array is embodied in theoretical analyses which combined with particle-in-cell (PIC) simulation. Mode and dispersion analyses on the design of the TM41-2π mode EIO demonstrated that the optimized cutoff frequency and the dimensions of the SWS noticeably suppress non-operating lower order modes. The overmoded structure only allowed the desired 4th order mode to propagate in the structure. In addition, this structure benefit from a mm-level transverse size structure, so that it can be a potential solution for the applications (such as communications and spectroscopy) lack in output power. The newly designed EIO is simulated with copper used as the background material, and the ∼0.375 THz radiation power of ∼105W is achieved when an electron beam with 1.3 A and 44.5 kV is injected. The designed circuit structure can be widely applied to sheet beam devices for THz RF generation.

Statistical analysis of wind-induced pressure fields and PIV measurements on two buildings

This study investigated the aerodynamic characteristics of two tall buildings through an independent component analysis (ICA) and principal component analysis (PCA) of wind-induced pressure fields. The pressure patterns identified by ICA and PCA were compared using the wind pressures on two building models measured in a series of wind tunnel tests under five cases consisting of different gaps between two buildings. To further investigate the flow patterns, particle image velocimetry was employed to measure the instantaneous wind flow patterns. The ICA results in the 1st, 2nd, and 4th modes indicated different pressure distributions on the inside building surfaces for different gaps, while the 3rd mode indicated a suction phenomenon on the outside and leeward surfaces; the PCA results indicated that the gap only influenced the pressure on the inside surfaces in the first four modes. Only the first PCA mode had a higher correlation with the original data than the ICA modes, and the ICA modes generally had higher correlations than the other modes. In wind forces, the 1st and 3rd PCA modes provided similar information, whereas all the ICA modes provided different information. Overall, ICA provided more diverse information than PCA, which yielded rather limited and homogenous information.

Surface wave tomography for the Pacific Ocean incorporating seafloor seismic observations and plate thermal evolution

Using broadband seismic waveforms recorded on the seafloor by more than 200 broadband ocean bottom seismometers, as well as those on land, we measured the phase speed dispersions of Love and Rayleigh waves up to the 4th higher mode to determine the three-dimensional radially anisotropic shear-wave speed structure in the upper mantle beneath the Pacific Ocean. The fastest anomalies at depths shallower than 100 km were located beneath southeast of the Shatsky Rise and strong radial anisotropy was located in the central Pacific at depths of 100–200 km. The isotropic shear-wave speed structures showed age dependence. From the age-bin-averaged shear-wave speed profiles and a half-space cooling model, we estimated the thermo-speed relationship for the Pacific Plate to construct a reference age-dependent shear-wave speed model, which was further used as an initial model for tomography iteration. Deviation maps in the Pacific Ocean from the reference model indicated that large negative residuals, which may be due to partial melting, anelasticity, and/or added heat from mantle plumes, were located along the ridges and beneath hotspots, and that large positive residuals were found beneath the northwestern Pacific Ocean. The use of an age-dependent reference model, as well as the incorporation of OBS data, greatly improves the accuracy of local phase speed estimates in tomography, as evident from a direct comparison with in situ array measurements.

Miniaturized High-Order-Mode Dipole Antennas Based on Spoof Surface Plasmon Polaritons

A miniaturization method for antennas is developed based on spoof surface plasmon polaritons (SSPPs). With a large phase constant on the SSPPs transmission line, the guide wavelength can be dramatically reduced, with great potential on the miniaturization application of antennas. By introducing a miniaturization factor M , the relationship between M and the phase constant on the SSPPs dipole is studied, providing guidance to the design of miniaturized SSPPs dipoles. Then, SSPPs dipoles operating at 2.4 GHz are designed, including both the odd- and even-resonance dipoles. Simple feeding structures are developed for the odd- and even-resonance dipoles, respectively, and particularly for the even-resonance mode to realize a transition from 50 Ω to very large input impedance of the dipole. The miniaturized SSPPs dipoles operating at the 1st, 2nd, 3rd, and 4th modes are fabricated. The measured reflection coefficients and radiation patterns show good agreements with the simulated results. It can be concluded that the dipole lengths for these modes are reduced by 8%, 11%, 10%, and 13%, respectively, compared with the conventional printed dipoles on the same substrate.

Numerical investigation on effects of fringing reefs on low-frequency oscillations within a harbor

The low-frequency (LF) oscillations inside an elongated rectangular harbor near the offshore fringing reef excited by bi-chromatic short wave groups are simulated using a fully nonlinear Boussinesq model. Based on a LF wave analysis procedure, effects of reef-face slope and reef ridge on the maximum LF wave amplitude, the free and the bound LF waves and their relative components inside the harbor are investigated systematically under the conditions of the 2nd to the 5th modes and wave breaking occurring over the reef. Results show that the variation trends of the maximum LF wave amplitude and the free LF wave amplitude with respect to the reef-face slope are almost identical with each other for all the four modes studied in this paper, no matter whether the reef ridge exists or not. For the 4th and 5th modes, the reef ridge has obvious influences on the LF waves inside the harbor. Under these two modes, the existence of the reef ridge always decreases the bound LF wave amplitude and its ratio to the free LF wave amplitude inside the harbor, while its influences on the maximum LF wave amplitude and the free LF wave amplitude both depend on the reef-face slope.

Effect of profile parameters on cut-off V values of LP modes in designing intermodal dispersion free few mode fiber

In an earlier work, we have proposed an intermodal dispersion free quadruple mode fiber which has a composite refractive index profile. It is an emerging intermodal dispersion free fiber. An appropriate V parameter is chosen for this fiber at which it is operated and this should be below the cut-off V value of the 5th LP mode. It is observed that the order of appearance of the modes above the 4th mode is extremely sensitive to the profile parameters. A thorough investigation on order of appearance of the modes has been reported in the present work for an optical fiber having composite refractive index profile. Such a study is important to design the intermodal dispersion free quadruple mode fiber for use as a transmission medium and in other optical fiber devices.

Effect of Electro-spark Coating on Wear Loss of Rotavator Blades

Rotavator has been increasingly used in agricultural fields. Under abrasive conditions for ground engaging tools, rotavator blades require frequent replacement resulting to increasing machine downtime and maintenance cost. Electric spark coating (ESC) technique was evaluated on two different commercially available blades with tungsten carbide, Stellite-21 and chromium carbide coating materials to improve their life. Coating materials were applied with three different thicknesses on the blades.Wear loss of the second blade with tungsten carbide 4th mode treatment was about 0.80 % per hour less than the other treatments for both blades. Hardness (58.33 HRA) of the second blade with chromium carbide 4th mode treatment was highest among all treatments and blades. The build-up height with chromium carbide 6th mode treatment was 160.8 µm.

Parametric investigation of combustion instabilities in a single-element lean direct injection combustor

Self-excited combustion dynamics in a liquid-fueled lean direct injection combustor at high pressure (1 MPa) are described. Studied variables include combustor and air plenum length, inlet air temperature, equivalence ratio, fuel nozzle location, and fuel composition. Measured pressure oscillations were dependent on combustor geometry and ranged from about 1% of mean chamber pressure at low equivalence ratio, up to 20% at high equivalence ratio. In the most unstable cases, strong pressure modes were measured throughout the frequency spectrum including a band around 1.2–1.5 kHz representing the 4th longitudinal mode, and another band around 7 kHz. The oscillation amplitudes have a non-monotonic dependency on air temperature, and are affected by the placement of the fuel nozzle relative to the throat of the subsonic swirling air flow. The parametric survey provides a rich dataset suitable for validating high-fidelity simulations and their subsequent use in analyzing and interpreting the complex combustion dynamics.

Effect of Electro-spark Coating on Wear Loss of Rotavator Blades

Rotavator has been increasingly used in agricultural fields. Under abrasive conditions for ground engaging tools, rotavator blades require frequent replacement resulting to increasing machine downtime and maintenance cost. Electric spark coating (ESC) technique was evaluated on two different commercially available blades with tungsten carbide, Stellite-21 and chromium carbide coating materials to improve their life. Coating materials were applied with three different thicknesses on the blades.Wear loss of the second blade with tungsten carbide 4th mode treatment was about 0.80 % per hour less than the other treatments for both blades. Hardness (58.33 HRA) of the second blade with chromium carbide 4th mode treatment was highest among all treatments and blades. The build-up height with chromium carbide 6th mode treatment was 160.8 µm.

진동특성 해석을 위한 착좌자세의 5자유도 인체 모델 개발

In this study, we developed a seated 5-DOF (degree-of-freedom) human model composed of three parts; head, trunk and lower body. The mode shape and undamped natural frequencies were calculated using the derived equations of motion. The spring and damping coefficients of the human model were extracted based on experimental results using the optimization. Also, parametric study of the natural frequencies with respect to the stiffness values of the human model were performed. The veering phenomenon was observed between 4th and 5th modes for variations of the torsional stiffness representing the head-neck joint and the translational stiffness connected between the lower body and the seat floor.

Numerical simulations of vortex-induced vibrations of a flexible riser with different aspect ratiosin uniform and shear currents

This paper aimed at describing numerical simulations of vortex-induced vibrations (VIVs) of a long flexible riser with different length-to-diameter ratio (aspect ratio) in uniform and shear currents. Three aspect ratios were simulated: 500, 750 and 1 000. The simulation was carried out by the in-house computational fluid dynamics (CFD) solver viv-FOAM-SJTU developed by the authors, which was coupled with the strip method and developed on the OpenFOAM platform. Moreover, the radial basis function (RBF) dynamic grid technique is applied to the viv-FOAM-SJTU solver to simulate the VIV in both in-line (IL) and cross-flow (CF) directions of flexible riser with high aspect ratio. The validation of the benchmark case has been completed. With the same parameters, the aspect ratio shows a significant influence on VIV of a long flexible riser. The increase of aspect ratio exerted a strong effect on the IL equilibrium position of the riser while producing little effect on the curvature of riser. With the aspect ratio rose from 500 to 1 000, the maximum IL mean displacement increased from 3 times the diameter to 8 times the diameter. On the other hand, the vibration mode of the riser would increase with the increase of aspect ratio. When the aspect ratio was 500, the CF vibration was shown as a standing wave with a 3rd order single mode. When the aspect ratio was 1 000, the modal weights of the 5th and 6th modes are high, serving as the dominant modes. The effect of the flow profile on the oscillating mode becomes more and more apparent when the aspect ratio is high, and the dominant mode of riser in shear flow is usually higher than that in uniform flow. When the aspect ratio was 750, the CF oscillations in both uniform flow and shear flow showed multi-mode vibration of the 4th and 5th mode. While, the dominant mode in uniform flow is the 4th order, and the dominant mode in shear flow is the 5th order.

Investigation of Kelvin wave periods during Hai-Tang typhoon using Empirical Mode Decomposition

Equatorial Kelvin waves (KWs) are fundamental components of the tropical climate system. In this study, we investigate Kelvin waves (KWs) during the Hai-Tang typhoon of 2005 using Empirical Mode Decomposition (EMD) of regional precipitation, zonal and meridional winds. For the analysis, we use daily precipitation datasets from the Global Precipitation Climatology Project (GPCP) and wind datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-analysis (ERA-Interim). As an additional measurement, we use in-situ precipitation datasets from rain-gauges over the Taiwan region. The maximum accumulated precipitation was approximately 2400 mm during the period July 17–21, 2005 over the southwestern region of Taiwan. The spectral analysis using the wind speed at 950 hPa found in the 2nd, 3rd, and 4th intrinsic mode functions (IMFs) reveals prevailing Kelvin wave periods of ∼3 days, ∼4–6 days, and ∼6–10 days, respectively. From our analysis of precipitation datasets, we found the Kelvin waves oscillated with periods between ∼8 and 20 days.

Modal identification of single layer graphene nano sheets from ambient responses using frequency domain decomposition

Abstract In this paper, a new method has been proposed for determining mechanical properties of single-layer graphene sheets, without applying any external force and simply by measuring natural deformations of these sheets due to their ambient environmental conditions. Furthermore, the merits and potential applications of this method have been investigated by using Non-Equilibrium Molecular Dynamics (NEMD) virtual laboratory. Contrary to the ordinary methods of identifying mechanical systems, which rely on dynamic response of one structure to a predefined excitation, here the output-only frequency domain decomposition method has been employed. After presenting the theory behind the employed approaches, a virtual laboratory called the Laboratory of Nanometric Operational Modal Analysis (LNOMA) was set up and by using this laboratory, mechanical properties of single-layer graphene sheets were determined and compared with those obtained in previous works. Equivalent elastic modulus, Poisson's ratio and thickness of the examined graphene sheet were found to be 1.05 Tpa, 0.17 and 2.885 A, respectively. For the higher order natural frequencies, the equivalent thickness varies as 1.941, 2.00133, 1.4575, 1.307 and 1.3335 A for the 2nd to 6th mode shapes,respectively. An important point is that with the increase of the mode number, the equivalent thickness decreases, and after the 4th mode, the thickness ratio (equivalent thickness/frequency) does not change significantly and could be considered as 0.2 for the higher order modes. All the results obtained by applying random excitations; and this shows the importance of the present work for future experiments.

Schumann Resonance Mode Variation during Seismic Activity: A Review

Seismic activity and thunderstorm centers have strong relation because of which fourth mode (26Hz) of Schumann Resonance (SR) is varying. SR has numbers of resonance frequencies like first mode (8 Hz), second mode (14 Hz), third mode (20 Hz) and fourth mode (26 Hz). The variation of 4th mode of SR is taken into account due to the seismic effect. Characteristics of ionosphere changes on surface during & aftershock the main shock (https://www.britannica.com/science/aftershock-geology). The effective height of the ionosphere lower boundary is reduced to a few tens of kilometer. The lower ionosphere & mesosphere is modified by the seismic source detection of modification in higher frequency band. The Schumann Resonance signal is supported by electromagnetic radiation from the global thunderstorms & the anomaly in SR fourth mode frequency i.e. the shifting of frequency due to lowering of Ionosphere height is accumulated in this paper.

Roof tile-shaped modes in quasi free–free supported piezoelectric microplate resonators in high viscous fluids

This paper reports on higher orders of the roof tile-shaped bending mode in piezoelectrically actuated MEMS plate-type resonators with quasi free–free support, achieving an increased piezoelectric response of ∼25% compared to a one-sided clamped cantilever structure with the same geometry and similar quality factor. Aluminum nitride (AlN) is used for the excitation of the devices offering different anchor designs. These MEMS resonators are characterised by electrical and optical measurements in air and in several liquids (i.e., isopropanol and viscosity standards: D5, N10, N35, N100, D500). Nodal analyses are presented and compared to both Finite Element Methods simulations and Laser Doppler Vibrometer measurements, demonstrating an excellent agreement between the positions of the plate supports with those of the nodal lines of the specific mode, which ensures a quasi free–free vibration. An optimized electrode design (OED) is established and compared to non-optimized actuation, showing superior performance for plates with OED. The evaluation of the quality factor Q and the strain related conductance peak ΔG of the investigated modes results in the highest value for the 4th order mode (Q∼100; ΔG=0.35mS). Finally the piezoelectric response ΔG/Q (∼4μS for 4th order mode) is presented, showing great potential for a large variety of challenging resonator based physical and chemical sensing applications.

A 3D shear-wave velocity model of the upper mantle beneath China and the surrounding areas

We present a three-dimensional model of shear wave velocity for the upper mantle of China and the surrounding region by analyzing 50,338 vertical component multi-mode Rayleigh wave seismograms, recorded at 144 permanent and more than 300 temporary broadband stations in and around China. The procedure involves combination of 1-D path average models obtained by modeling each Rayleigh waveform up to the 4th higher mode in a tomographic inversion scheme. The dense station network and the use of multi-mode analysis help to achieve a lateral resolution of a few hundred kilometers down to 400km depth. The seismic lithosphere, as it is defined by the crust and the high velocity mantle lid, is to the first order thin in east China and thick in the west, with a high velocity lid extending down to about 200km depth beneath much of the Tibet–Pamir plateau. Beneath India, the thickness of the seismic lithosphere gradually increases from ~100km in south India to more than 150km in north India, where it underthrusts the Tibetan plateau to approximately the Jinsha River Suture. High velocity lid extending down to 100–150km depth is also observed in the Tarim basin, Sichuan basin and Ordos block. In the eastern part of the North China craton the seismic lithosphere is probably close to or thinner than 70km. Adjacent to these areas, the high velocity lid in the eastern Yangtze craton and South China fold system extends down to 70–80km depth. A large-scale subhorizontal high velocity body is observed at depths of 150–350km beneath the entire east China cratonic areas. This high velocity body might be the remnant of a delamination process which resulted in the decratonization of the North China and the Yangtze cratons.