Oscillation Method Research Articles

Dual-Algorithm Hybrid Method for Riser Structural Health Monitoring Using the Fewest Sensors

This study suggests a novel riser structural health monitoring methodology based on a dual algorithm (DA). In this method, the displacement tracing algorithm first traces the node displacement and tension up to the last sensor position called the target point. Then, the movement and tension at the target point are used for boundary conditions of the finite element (FE) simulator to obtain displacements and stresses below the target point. The developed method is validated through numerical simulations by comparing riser behaviors/stresses from the fully coupled model with those from the proposed method with numerical sensors. For that, a moored FPSO (floating production storage offloading) system with SCR (steel catenary riser) or SLWR (steel lazy-wave riser) is employed. Only three angle sensors are used at the top portion to monitor the entire length of riser. Much simpler forced top oscillation method is also investigated, which only uses riser top movement for running FE simulator, which cannot accurately reproduce the dynamics of the upper portion of riser since real-time wave action is ignored. The developed DA riser monitoring methodology can reproduce the movements and stresses along the entire length within around 5% error regardless of riser shapes and materials.

Experimental investigation on the hydrodynamic effects of heave plates used in floating offshore wind turbines

Due to the abundant wind energy in deep water, floating offshore wind turbines (FWTs), especially for the semisubmersible FWTs, have attracted more attention these years. To reduce the heave motion of FWTs, heave plates are often attached at the bottom of the column. In this paper, experimental investigations of the hydrodynamic performance of the heave plates via the forced oscillation method are conducted. The impacts of the KC number (KC = 0.1–1.1), oscillation frequency (f = 0.4–1.43 Hz), diameter ratio-Dd/Dc (Dd and Dc are the diameter of the heave plate and column), thickness ratio-td/Dd (td is the thickness of the heave plate), shapes of the heave plates, on the added mass, and damping coefficients are investigated. The results show that the added mass and damping coefficients are independent of oscillation frequencies, while the KC number influences significantly the hydrodynamic coefficients. Increase in the diameter ratios will decrease the added mass and damping coefficients. The thinner heave plates obtain larger damping coefficients. Comparison between the different shapes of the heave plates shows that the octagonal heave plate displays similar added mass and damping coefficients to the circular heave plate. However, square one obtains lower added mass coefficients compared to the other three shapes. And the hexagonal plate seems to have the highest damping force for different KC numbers.

Research on the Commissioning Method of a Current-controlled Oscillator

In this paper, the commissioning method of the current-controlled oscillator (ICO) is researched, making the ICO work under the required amplitude and frequency and exploring the best phase noise performance of ICO under the constraints of power dissipation and area. Through the theoretical analysis and simulation experiments, the commissioning process of ICO is clarified, which can meet the basic indexes of ICO, especially the amplitude and frequency, and optimize the phase noise performance of ICO.

Kendali Tegangan Konverter Boost Berbasis Proposional Integral (PI)

Technological developments, electronic components and circuits have resulted in a direct voltage supply system that is produced by converting the input DC voltage to another form of DC voltage with a higher output utilizing a boost converter circuit, using a low source voltage where the output voltage can be changed according to user requirements. To anticipate the voltage drop on the output side which is affected by changes in the resistance value of the load and changes in the value of the source voltage, a voltage control is needed that can regulate the output stability of the boost converter. One of the voltage control techniques used is integral proportional controller (PI). This study uses the Ziggler – Nichols oscillation method which is applied to the integral proportional controller (PI) in the boost converter circuit by using the Arduino Mega2650 as a controller circuit which is programmed with Matlab Simulink and a voltage sensor that functions to detect output on the boost converter as well as feedback from the Proportional Integral (PI) controller which will later be compared with the desired setpoint to produce the appropriate Pulse width Modulation (PWM) signal. The test results show that the PI controller works well in accordance with the purpose of adjusting the output voltage on the boost converter. This can be seen in the output of the boost converter which is in accordance with the reference voltage of 15 volts, 20 volts, and 24 volts with an output voltage of 15.36 volts, 20.52 volts, 24.82 volts

Extolling thermoelectric properties of incommensurate (IC) TlBiSe2 polycrystals prepared by melt temperature oscillation method

The high-ordered crystal structure of a thermoelectric material does not delimit the phonon conductivity but shows improved electrical properties. Disordered crystal structures act as scattering centers for phonon, but at the expense of the electrical properties of the material. Hence, a diminished thermal (phonon) conductivity and improved electronic conductivity can be obtained from an incommensurate (IC) phase structure. This paper reports that TlBiSe2 polycrystal material exhibits incommensurate (IC) phase (disordered structure). The ‘Tl+’ connecting chains and the disordered structure inherent in the IC phase enhance the TE properties in TlBiSe2. The crystalline phase was confirmed for TlBiSe2 by X-ray diffraction (XRD). These polycrystals have shown their characteristic Raman modes and micro flake-like morphology, as observed by Raman spectroscopy and field emission scanning electron microscopy (FESEM). X-ray photoelectron spectroscopy confirmed the IC phase formation by observing the characteristic binding energy shift of ‘Tl’ and ‘Se’ states. The parallel plane symmetry break in the IC phase has resulted in a hall carrier concentration (n) of 3.49 × 1020 cm−3 and mobility (μ) of 8.27 m2V−1s−1. Further, Seebeck coefficient showed 80 μV/K; the Wiedemann Franz law calculation reserved a lower electronic thermal conductivity of 0.003381 Wm−1K−1 and a power factor of 2.956 μW/m K2 has been attained.

Mechanical and microstructural properties of dissimilar copper and stainless-steel butt welds prepared using zigzag and circular fiber laser oscillation methods

Dissimilar copper and stainless-steel butt welds are prepared using zigzag and circular laser beam oscillation welding methods. The tensile strengths, microhardness values, and weld bead morphologies of the joints are evaluated and compared for various values of the oscillation amplitude and frequency. The optimal laser oscillation parameters are found to be a laser power of 1550 W, an oscillation frequency of 15 Hz, and an oscillation amplitude of 1 mm. Under these optimal processing conditions, the tensile strengths of the joints produced using the zigzag and circular oscillation welding modes are 232.6 MPa and 235.7 MPa, respectively. The superior strength of the weld produced using the circular oscillation method is attributed to a more uniform mixing of the alloying elements in the weld zone and a greater penetration depth. The addition of a thin Ni interlayer to the joint is found to improve the tensile strength to 240 MPa for the zigzag oscillation mode and 242 MPa for the circular oscillation mode. By contrast, the addition of a Ti interlayer reduces the tensile strengths of the joints to around 163 MPa and 198 MPa, respectively. The reduction in the tensile strength is the result mainly of a more brittle fracture mode within the heat affected zone (HAZ). Nonetheless, the circular oscillation welding mode results in a higher tensile strength than the zigzag mode due to a greater suppression of intermetallic compound (IMC) phase in the weld area and a reduction in the number of pores and cracks. Compared to conventional straight-line welding, the zigzag and circular oscillation modes reduce the grain size by around 32% and 52%, respectively, and enhance the mechanical properties accordingly.

RANCANG BANGUN PENGENDALIAN TEGANGAN MENGGUNAKAN KONTROL PID-ARDUINO PADA PROTOTIPE MINI PLANT MIKROHIDRO

Microhydro power plant is an alternative for producing small-scale electrical energy uses hydropower. Microhydro has three main components, water, turbine and generator. In the environment , it can also be used as a microhydro power plant on a home scale. The components needed to make microhydro prototype are water reservoirs, valves, MOV,generators, flowmeters, voltage sensors,LED . The water reservoir is installed as high as 4 meters. MOV is used as an actuator to control the flow of water to adjust the degree of valve opening automatically. Generator is connected to convert mechanical energy into electrical energy, flowmeter to determine the debit value and a voltage sensor is connected. The system will be connected to the load of an LED light. When the lamp load changes, it is expected that the voltage generated by the generator remains stable. To regulate the voltage to remain stable, voltage control is carried out by adjusting the degree of valve opening using a PID control system. Voltage control with PID control based on Ziegler Nichols theory with oscillation method. Through experimentation, it was obtained that the KP = 0.9, Ki = 0.45 and Kd = 0.45 constants were the most optimal because the response of the oscillating system was 1.15 seconds shorter. The time required for the voltage to stabilize to the setpoint from the start of the system being turned on is 46.20 seconds. The greater the degree of valve opening, the greater the voltage generated, because the debit produced is greater.

Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument

The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z > 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector; a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface; 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs; and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O ii] doublet at 8 × 10−17 erg s−1 cm−2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.

A Multi-Constrained Optimization Method for THz Backward Wave Oscillators

The current design period for various backward wave oscillators (BWOs) is still at least several months. How to find the best structure parameters with an efficient and stable optimization method is a problem facing researchers in both scientific research and engineering work. In this paper, a non-randomized iterative optimization method is proposed. It applies orthogonal design methods to find local solutions that can provide optimal ‘gradient direction’ for several successive next iteration steps. An evaluation function is designed to distinguish the better ones from the local solutions in the multi-constrained optimization of such BWOs. Optimizations from different starting points are performed separately for a global optimal solution. Two BWOs at different frequency ranges are optimized using the proposed method. The validity and stability of the method are verified. It is believed that the method can provide the global optimum and shorten the design period of THz BWOs.

The beating effect in uniaxial oriented polymer materials

Elastic-relaxation properties of uniaxial oriented polymer materials under dynamic deformation mode are investigated. A theoretical explanation of the phenomenon of the occurrence of beats is proposed. Experimental confirmation of the obtained theoretical results is given. Using the barrier theory and applying the balance equation of the number of cluster transitions through the energy barrier, taking into account the transition time, a refined constitutive equation of the viscoelasticity of the polymer materials is obtained. Experimental studies in the dynamic mode were carried out by the method of the longitudinal low-amplitude oscillations. For a polymer material, taking into account the time of transition of the cluster through the energy barrier, a refined constitutive equation is obtained. The resulting equation is a second-order differential equation and admits a periodic solution. The application of the obtained equation to the study of free longitudinal low-amplitude oscillations in uniaxial oriented polymer materials is considered. It is shown that the solution of the equation admits two close complex roots, the existence of which leads to the effect of the observed beats. The relations between the parameters of the oscillatory process and viscoelastic characteristics are obtained. The experiment showed that the polymer materials under study have a complex form of the oscillatory process, similar to the phenomenon of beats, in a certain range of load. The dependence of the tangent of the mechanical losses angle calculated from the main frequency on the stress has an acute maximum in the stress range where beats are observed. According to the obtained theoretical ratios and experimentally determined attenuation coefficient and main frequency, the time of transition of the cluster through the energy barrier or the lifetime of the cluster in this energy state is determined. The use of additional information obtained during experiments in static modes made it possible to determine the relaxation time for this material. The calculation on the example of polyethyleneterephthalate (PET) filament showed that the theory is consistent with the experiment. Based on the experimental data obtained during the study of free longitudinal oscillations and the solution of the refined constitutive equation, it is possible to determine the necessary viscoelastic characteristics which makes it possible to predict dynamic deformation processes in polymer materials.

STUDY OF FACTORS INFLUENCING VIBROISOLATING PROPERTIES OF MATERIALS FOR PASSIVE ELASTIC BEARING OF MACHINES

Machinery or instruments are subjected to external forces from a base in many cases. It can have a negative influence on manufacturing accuracy, tightness, wear of machine parts, work safety etc. Therefore, it is necessary to perform suitable passive elastic bearings of machinery to eliminate external vibration from the base. An application of suitable vibroisolating materials is one way of the vibration elimination. The aim of the paper is to study vibration damping properties of different materials by means of a non-destructive method of forced mechanical oscillations. Different factors influencing transfer damping of mechanical vibration were investigated in this work, e.g., material type and its thickness, excitation frequency of mechanical oscillations, size of mass load and effect of material composition. These factors were subsequently evaluated. Finally, suitable recommendations for passive damping of mechanical vibration were described.

Evaluation of the effectiveness of using an electromechanical shock absorber in a subway car

The paper evaluates the effectiveness of the electromechanical shock absorber for a subway car based on dynamic quality indicators. To determine them, a method of synthesis of random forced vertical oscillations of a dynamic model of a subway car was developed, which is based on the method of sliding summation taking into account the spectral density obtained when processing the test results of a subway car. Also in the work the technique on definition of indicators of dynamic quality of the metrocar with electromechanical shockabsorbers which is based on modeling of processes of movement of the subway car on a site of a way with casual roughness and definition, by results of modeling, indicators of dynamic quality is created. The study of forced random oscillations of the dynamic model of a subway car showed that the spring suspension based on electromechanical shock absorbers has a significant advantage over the central spring suspension for all quality indicators in the entire range of speeds. The dependence of the average power generated by the shock absorber is established.

Modeling of cable-stayed bridge and modal analysis

Problem. The considered Characteristics of the own forms of a cable-stayed bridge according to several of its schemes. The analysis of the influence of the type of resistance on the characteristics of the own forms of resistance for different sets was carried out. Among the types of resistance, full rigidity, hinge and no resistance were taken. Goal. The purpose of the study is to determine the causes of registered traffic accidents and emergencies associated with them. To do this, it is proposed to analyze the own forms of the cable-stayed bridge for various types of its contact (resistance) with the columns. The object of the study is a cable-stayed bridge with a service life of about 50 years. The bridge is a system of three types of elements: pylon, span and columns. The subject of the study is the forms of natural oscillations of the bridge according to its various models. Methodology. The study was carried out by using oscillation and finite element methods. It should also be noted that the original methods for constructing models of complex machine-building systems were used, which were developed directly by the author. Results. Based on the results of the research, three-dimensional finite element models of parts and the entire bridge as a single system for various types of resistance were built, and their own forms were obtained for each model of the system. The study allows us to draw conclusions on specifying the causes of road traffic accidents and ways to prevent them. Originality. Regarding the methods of constructing models of a cable-stayed bridge, we note their uniqueness. Taking into account the features of modeling, it became possible to create several states of interaction between the parts of the system. To conduct reliable research for a real model of a structure, it is necessary to have reliable data about the real state of the connections of its elements. This state can range from absolutely rigid to free. Accounting for these features is possible with the help of a unique author's methodology for building models using the universal capabilities of the finite element method. Previous studies of the bridge by other methods did not allow us to solve the tasks set for the occurrence of traffic accidents. Practical value. The results of the work have direct practical application. Based on the results of the work, conclusions were drawn about ways to improve the reliability of the system and the measures to prevent traffic accidents.

Structural and Dynamical Studies of a Lipid-Nanoclay Composite Layer at the Air-Water Interface.

We modulate the adsorption affinities of nanoclay particles for the air-water interface by changing the cationic surface charge composition of the lipid monolayer and thereby tune the attractive electrostatic interaction between the positively charged lipid layer and the zwitterionic nanoclay particles in the water subphase. Our findings emphasize the significance of electrostatic interaction between lipids and the nanoclay, as well as its impact on the structural and viscoelastic features of the composite layer. We use surface pressure (Π)-mean molecular area (A) isotherms, atomic force microscope (AFM), Brewster angle microscopy (BAM), and energy dispersive X-ray spectrsocopy (EDXS) measurements to analyze the structure phases of lipid and lipid-nanoclay composite interfacial layer. The Π-A isotherm curve shows that the lipid-nanoclay composite layer has a larger lift-off area than the neat lipid layer, indicating that nanoparticles adsorb at the lipid layer via electrostatic interaction between lipid and nanoclay molecules. The surface density of the adsorbed nanoclay particles increases with an increase in the composition of the cationic lipid molecules. The stress relaxation response of the composite layer, measured using step compression measurements, exhibits exponential decay and ubiquitous dependence on the cationic dimyristoy-trimethylammonium propane (DMTAP) composition in the lipid layer with crossover to faster relaxation dynamics at DMTAP > 0.75. The power-law study of the frequency-dependent dynamic viscoelastic responses of the interfacial layer, measured using the barrier oscillation method, reveals a transition from glass-like response from neat lipid layer to gel-like dynamic response for the lipid-nanoclay composite layer. A solid-like behavior is evident for all the interface layers with dilation elastic modulus (E') > dilational viscous modulus (E″); however, the dynamic response of the neat layer is largely frequency-independent, whereas lipid-nanoclay composite layers with DMTAP > 0.75 reveal a frequency-dependent dynamic responses. The frequency-dependent power-law exponent of E', E″ increases on increasing the fractional composition of cationic DMTAP from 0.1 to 1.0, which forms a saturated interface of laponite particles and behaves as a viscoelastic gel in 2D.

Feasibility of soil erosion measurement using time domain reflectometry

Scientific research and control technology of soil erosion both rely on accurate and efficient soil erosion measurements. Based on the principles of locating interfaces in layered media and measuring dielectric properties by time domain reflectometry (TDR), we developed TDR-based measurement of changes in the air–soil interface along the TDR probe for soil erosion measurement, and simultaneously measuring volumetric soil moisture content (θv). Part of a three-rod TDR probe was inserted in the soil and the rest exposed to air, so changes in the air–soil interface could be denoted by changes in the length of exposed probe (Lair). TDR waveforms were analyzed using a combination of tangent line method and second-order bounded mean oscillation methods to identify time points at positions of impedance discontinuity in electromagnetic propagation, then converting these data to Lair and θv by calibrated equations. According to the laboratory experiment using sandy loam and silt loam, Lair could be effectively measured within a wide soil moisture range by the calibrated equation and the thickness of the eroded soil layer could thus be determined. The RMSE of θv measurement ranged between 0.003 and 0.025 cm3 cm−3, which enabled the identification of the appropriate soil moisture range for measuring Lair, and achieve reliable simultaneous measurement of soil erosion and soil moisture content. The simulated rainfall experiment using sandy loam and silt loam and field scouring experiment conducted in loam also indicated that the proposed method could achieve high measurement accuracy in erosion environments, for which Lair with the RMSE from 1.8 to 2.1 mm and θv with the RMSE from 0.007 to 0.024 cm3 cm−3. The proposed method has various advantages, including versatility, minimal disturbance, easy automation of measurement at multiple positions, etc., could serve as a new technical option for soil erosion measurement, and extend the utilization of TDR.

Three-dimensional Langevin dynamics of N atom scattering from N-covered Ag(1 1 1)

We analyzed the dynamics of N atom scattering from N -covered Ag(1 1 1), using the generalized Langevin oscillator (GLO) method and a three-dimensional neural network potential energy surface. Two values for the mass of the surface oscillator were considered in the GLO model to account for the energy exchange with the surface, i.e., that of Ag and that of N. For these mass values different trends were found for the dependence of the ratio of the average final divided by the average initial translational energy on the scattering angle. Using the nitrogen mass gives a trend closer to the experimental results for the dependence of the energy of the in-plane scattered atoms on the scattering angle, but worse agreement with experiment for the angular distribution of the in-plane scattered atoms. Two different algorithms are applied to integrate the stochastic equations of motion in the presence of energy dissipation. Our calculations show that a trivially extended Bulirsch-Stoer algorithm is more efficient than an algorithm based on a Langevin Liouville operator splitting technique, in that it yields the same results with a much larger time step.

Modeling for extracavity-pumped terahertz parametric oscillators.

This paper presents a modeling method for extracavity-pumped terahertz parametric oscillators (TPO) based on stimulated polariton scattering, in which the pumping beam is from a different laser, and the Stokes beam oscillates in its cavity. After suitable approximations and assumptions, the average THz wave amplitude in the nonlinear crystal is expressed as a function of the fundamental and Stokes wave amplitudes. Then the rate equation for the Stokes wave is obtained based on the Stokes wave increment within a cavity roundtrip timescale. After solving the Stokes wave rate equation, the Stokes wave temporal evolution is considered as a known parameter, and the properties of the residual fundamental and terahertz waves are obtained by numerically solving the coupled wave equations. This modeling method is applied to an extracavity-pumped TPO based on MgO:LiNbO3 crystal. The simulation results are basically consistent with the experimental results. The main reasons causing the deviations of the simulation results from the experimental results are analyzed. To the best of our knowledge, this is the first time to perform the modeling for extracavity-pumped Q-switched TPOs.

Thermophysical properties of molten Ga2O3 by using the electrostatic levitation furnace in the International Space Station

We measured the thermophysical properties of molten gallium oxide (Ga2O3) in a contamination-free and microgravity environment by using the electrostatic levitation furnace in the International Space Station. The density of molten Ga2O3 was obtained over a wide temperature range of 2001–2174 K including the undercooled state and found to be expressed as 5004.8–0.4478(T − T m) (kg m−3), where T m, the melting point, is 2066 K. Measurements of its viscosity and surface tension were also performed by using the drop oscillation method and these values were found to be 337.0 (10−3 N m−1) and 13.6 (10−3 Pa·s) at 2228 K, respectively.

Study of Change in Stainless Steel Plate Thickness using S-Domain Parameters Derived from Transient Eddy Current Oscillations Method

Failures in the industrial components are unavoidable due to material degradation from various sources, thus continuous monitoring and timely inspection is mandatory for structural safety. In the present study, the recently developed Transient Eddy Current Oscillations (TECO) method is used to detect wall-thinning in a stainless-steel plate. Unlike the conventional Eddy Current Testing impedance plane data a new interpretation method has been implemented to identify a thickness variation using the S-domain parameters. Furthermore, time and frequency spectral features are analysed to get more insight into the results. The decay time and the resonant frequency are the basis for the discussion to assess the wall thickness.

Study on stability and microstructure properties of oscillating laser welded 5A06 alloy with narrow gap

In order to reduce porosity and improve welding quality during laser welding with narrow gap of 5A06 aluminum alloy, a laser oscillation method was applied in this study. By comparing the welds with different scan paths, it was found that the laser oscillation with cycloid path could restrain the formation of pore defects, improve the surface appearance, and enhance the stability of the molten pool. EBSD results under different scanning paths described the effect of laser oscillation on the microstructure of the weld. The influence of oscillation amplitude and frequency on welding quality was studied as well. The pore defect could be eliminated when the amplitude was greater than 2 mm and the frequency was greater than 150 Hz. Dynamic information of the molten pool and plasma was obtained through a high-speed camera system. It was found that the oscillating laser could partly avoid the influence of the plasma on laser energy attenuation. Finally, a multi-layer welding experiment was carried out using the optimized oscillated laser parameters.