The semi-analytical modeling and vibration reduction analysis of the cylindrical shell with piezoelectric shunt damping patches

By considering electromechanical coupling, a unified dynamic model of the cylindrical shell with the piezoelectric shunt damping patch(PSDP) is created. The model is universal and can simulate the vibration characteristic of the shell under different states including the states in which PSDP cannot be connected, partially connected, and completely connected to the shunt circuit. The equivalent loss factor and elastic modulus with frequency dependence are proposed to consider the electrical damping effect of resistance shunt circuits. Moreover, the semi-analytical dynamic equation of the cylindrical shell with PSDP is derived by the Lagrange equation. An experimental test is carried out on the cylindrical shell with PSDP to verify the vibration suppression ability of PSDP on the cylindrical shell and the correctness of the proposed model. Furthermore, the parameter analysis shows that determining the appropriate resistance value in the shunt circuit can achieve a good vibration suppression effect.

Thermodynamic analysis of the carbothermic reduction of a high-phosphorus oolitic iron ore by FactSage

A thermodynamic analysis of the carbothermic reduction of high-phosphorus oolitic iron ore（HPOIO） was conducted by the Fact Sage thermochemical software. The effects of temperature, C/O ratio, additive types, and dosages both on the reduction of fluorapatite and the formation of liquid slag were studied. The results show that the minimum thermodynamic reduction temperature of fluorapatite by carbon decreases to about 850°C, which is mainly ascribed to the presence of SiO_2, Al_2O_3, and Fe. The reduction rate of fluorapatite increases and the amount of liquid slag decreases with the rise of C/O ratio. The reduction of fluorapatite is hindered by the addition of CaO and Na_2CO_3, thereby allowing the selective reduction of iron oxides upon controlled C/O ratio. The thermodynamic results obtain in the present work are in good agreement with the experimental results available in the literatures.

STABILITY ANALYSIS OF DATA BUOY AT SEA

A data buoy, when moored at the sea, will be influenced by different environmental factors such as wind and wave current. For this reason, the stability of a data buoy is of great importance. This paper describes the analysis and calculation of the stability of a data buoy which has a weight suspended from its bottom under normal working conditions and the influence of the distance from the weight to the bottom of the buoy on the 'righting' ability of the buoy when it is capsized. The paper also provides the curves which show the influence of the size of the weight and the distance from the weight to the bottom of the buoy on the 'righting' ability of the buoy. All these are of great reference value for the design and use of a data buoy at sea and for the design of similar floating bodies. The results from calculations agree with those from the model experiment.

SIMULATION AND ANALYSIS OF WAVE GROUPS IN A WAVE FLUME

Using the trial-error method, for a given wave spectrum, wave trains with different wave groupness, which is defined by the groupness factor GF have been simulated in a flume. The statistic characteristics are analyzed for some of these wave trains in this paper.

Seismic response reduction analysis of large chassis base-isolated structure under long-period ground motions

Long-period structures(e.g.Isolated structures)tend to produce pseudo-resonance with low frequency compo-nents of long-period ground motions,resulting in the increase in damage.Stiffness mutation occurs due to the set-back in the upper body of the large chassis structure.In the parts with stiffness mutation,the torsion effect caused by the tower is far greater than that of the chassis itself.In this study,a total of 273 ground motions are collected and then filtered into four types,including the near-field ordinary,near-field pulse,far-field ordinary,and far-field harmonic.An 8-degree(0.2 g)fortified large chassis base-isolated structure is established.Furthermore,ETABS program software is used to conduct nonlinear time history analysis on the isolation and seismic model under bi-directional earthquake ground motions.The comparison results show that the seismic isolation effect of the base-isolated structure under long-period ground motions is worse than that associated with ordinary ground motions when the seismic response reduction rate of the large base floor significantly decreases compared with that of the tower.When the inter-story displacement angle and the displacement of isolation layer of the chassis exceeds the limit of Code for Seismic Design of Buildings(GB 50011-2010),it is recommended to adopt composite seismic isolation technology or add limit devices.Under the condition of long-period ground motions,the base-isolated structure reduces the lateral-torsional coupling effect of the large chassis structure,while the torsion response of large chassis’top layer increases.Under long-period ground motions with the same acceleration peak,the response of the base-isolated structure increases much more than that of the seismic structure and the consideration of this impact is suggested to be added to the Code.

SILTATION INVESTIGATION IN LIANYUN HARBOR BY USING γ-RAY DENSITY GAUGE

The principle, method and mersuring equipment in studying siltaton in the Lianyun Harbor by using the γ-ray density gauge are described in this paper. From field observation and analyses, some primary principles concerning the infill rate, the distribution of silt density with depth and the consolidation rate and change of the shear strength of the silt have been found out.

Determination of Shaft Capacity for Pile under Cyclic Axial Loading in Clay

For load-controlled and displacement-controlled test data of piles cyclically axiallly loaded in clay, the displacement conditions are suggested for determining the shaft capacity. According to the suggested displacement conditions, not only the results of shaft capacity from laboratory model piles are close to those from in-situ piles, but also the results of load-controlled tests are in satisfactory agreement with those of displacement-controlled test. Moreover, based on the test data of laboratory model piles in combination with the test data published, the paper suggests the values of the normalized shaft capacity of piles under a variety of static and cyclic loading combinations.

WAVE IMPACT THEORY AND SCALE EFFECT

In this paper the theoretical analysis and calculating method for the maximal impact caused by a jet are presented and the formulas for calculation of the maximal impact of waves acting on the slope are developed. Through the comparison between the results of model tests with a model scale of 1:10 and those of prototype tests conducted in the same way in Big Wave Flume, Hannover, West Germany, the effects of model scale on the measurement of wave impact on slopes are described. In addition, a distribution regularity of the maximal impact pressure is also given.

Wind-Wave Frequency Spectra of New Dalian Port

This paper, based on wave data measured with Type 956 Directional WAVE-TRACK Buoy System at new Dalian Port for a whole year, analyses the properties of the wave frequency spectra, and derives the formula for the frequency spectrum of wind-waves.

The Astrometric Performance Test of 80 cm Telescope at Yaoan Station and Precise CCD Positions of Apophis

The 80 cm azimuthal telescope has newly been mounted at Yaoan Station,Purple Mountain Observatory since2018.The astrometric performance of the telescope is tested in the following three aspects.(a)The geometric distortion of its CCD attached.It is stable in both a single epoch and multi epochs.Eight distortion solutions are derived over about one year.The maximum values range from 0.75 to 0.79 pixel and the median values range from 0.14 to 0.16 pixel.(b)The limit magnitude of stars.About 20.5 mag(Gaia-G)stars can be detected with Johnson-V filter exposured in 300 s.The astrometric error of about 20.5 mag stars is estimated at O".14 using the fitted sigmoidal function.(c)The astrometric accuracy and the precision of stacked fast-moving faint object.24 stacked frames of the potentially hazardous asteroid(99942)Apophis were derived on 2021 April 14 and 15(fainter than18 mag)based on the ephemeris shifts.During data reduction,the newest Gaia EDR3 Catalog and Jet Propulsion Laboratory Horizons ephemeris are referenced as theoretical positions of stars and Apophis,respectively.Our results show that the mean(O-C)s(observed minus computed)of Apophis are-O".018 and O".020 in R.A.and decl.,and the dispersions are estimated at O".094 and O".085,respectively,which show the consistency of the stacked results by Astrometrica.

Noise reduction in LOS wind velocity of Doppler lidar using discrete wavelet analysis

The line of sight (LOS) wind velocity can be determined from the incoherent Doppler lidar backscattering signals. Noise and interference in the measurement greatly degrade the inversion accuracy. In this paper, we apply the discrete wavelet denoising method by using biorthogonal wavelets and adopt a distance-dependent thresholds algorithm to improve the accuracy of wind velocity measurement by incoherent Doppler lidar. The noisy simulation data are processed and compared with the true LOS wind velocity. The results are compared by the evaluation of both the standard deviation and correlation coefficient. The results suggest that wavelet denoising with distance-dependent thresholds can considerably reduce the noise and interfering turbulence for wind lidar measurement.

6T SRAM cell analysis for DRV and read stability

The present paper analyzes the hold and read stability with temperature and aspect ratio variations. To reduce the power dissipation, one of the effective techniques is the supply voltage reduction. At this reduced supply voltage the data must be stable. So, the minimum voltage should be discovered which can also retain the data. This voltage is the data retention voltage（DRV）. The DRV for 6T SRAM cell is estimated and analyzed in this paper.The sensitivity analysis is performed for the DRV variation with the variation in the temperature and aspect ratio of the pull up and pull down transistors. Cadence Virtuoso is used for DRV analysis using 45 nm GPDK technology files. After this, the read stability analysis of 6T SRAM cell in terms of SRRV（supply read retention voltage） and WRRV（wordline read retention voltage） is carried out. Read stability in terms of RSNM can be discovered by accessing the internal storage nodes. But in the case of dense SRAM arrays instead of using internal storage nodes,the stability can be discovered by using direct bit line measurements with the help of SRRV and WRRV. SRRV is used to find the minimum supply voltage for which data can be retained during a read operation. Similarly, WRRV is used to find the boosted value of wordline voltage, for which data can be retained during read operation. The SRRV and WRRV values are then analyzed for different Cell Ratios. The results of SRRV and WRRV are then compared with the reported data for the validation of the accuracy of the results.

Influence of Size of Hematite Powder on Its Reduction Kinetics by H_2 at Low Temperature

The reduction kinetics and mechanisms of hematite ore with various particle sizes with hydrogen at low temperature were studied using the thermogravimetric analysis. At the same temperature, after the particle size of powder decreases from 107. 5μm to 2. 0 μm, the surface area of the powder and the contact area between the powder and gas increase, which makes the reduction process of hematite accelerate by about 8 times, and the apparent activation energy of the reduction reaction drops to 36.9 kJ/mol from 78. 3 kJ/mol because the activity of ore powder is improved by refining gradually. With the same reaction rate, the reaction temperature of 6.5 μm powder decreases by about 80 ℃ compared with that of 107. 5 μm powder. Thinner diffusion layer can also accelerate the reaction owing to powder refining. The higher the temperature, the greater is the peak of the reduction rate; at the same temperature, the greater the particle size, the smaller is the peak value of the reduction rate; both inner diffusion and interface chemical reaction play an important role in the whole reaction process.

CONVERGENCE OF ADAPTIVE EDGE ELEMENT METHODS FOR THE 3D EDDY CURRENTS EQUATIONS

We consider an Adaptive Edge Finite Element Method （AEFEM） for the 3D eddy currents equations with variable coefficients using a residual-type a posteriori error estimator. Both the components of the estimator and certain oscillation terms, due to the occurrence of the variable coefficients, have to be controlled properly within the adaptive loop which is taken care of by appropriate bulk criteria. Convergence of the AEFEM in terms of reductions of the energy norm of the discretization error and of the oscillations is shown. Numerical results are given to illustrate the performance of the AEFEM.