Characteristics of the Function of Ice Force on Vertical Cylindrical Piles

A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A function of ice forces is simplified on basis of test data, and the characteristics of the ice forces including the amplitude of the force and the breaking frequency of the ice sheet is detailed by use of the Fast-Fourier-Transform method, The results show that the ice breaking frequency presents a linear relationship with the ratio of ice moving velocity to ice thickness at low velocities. At high velocities, the frequency remains constant with the increase of the ratio of ice moving velocity to ice thickness. These conclusions are compared those published in literature.

Study on the 3D Green＇s functions of the fluid and piezoelectric bimaterials

Because most piezoelectric devices have interfaces with fluid in engineering, it is valuable to study the coupled field between fluid and piezoelectric media. As the fundamental problem, the 3D Green＇s functions for point forces and point charge loaded in the fluid and piezoelectric bimaterials are studied in this paper. Based on the 3D general solutions expressed by harmonic functions, we constructed the suitable harmonic functions with undetermined constants at first. Then, the couple field in the fluid and piezoelectric bimaterials can be derived by substitution of harmonic functions into general solutions. These constants can be obtained by virtue of the compatibility, boundary, and equilibrium conditions. At last, the characteristics of the electromechanical coupled fields are shown by numerical results.

Analysis of a kind of Duffing oscillator system used to detect weak signals

The stability of the periodic solution of the Duffing oscillator system in the periodic phase state is proved by using the Yoshizaw theorem, which establishes a theoretical basis for using this kind of chaotic oscillator system to detect weak signals. The restoring force term of the system affects the weak-signal detection ability of the system directly, the quantitative relationship between the coefficients of the linear and nonlinear items of the restoring force of the Duffing oscillator system and the SNR in the detection of weak signals is obtained through a large number of simulation experiments, then a new restoring force function with better detection results is established.

Molecular Dynamic Simulation of Melting Points of Trans-1,4,5,8- tetranitro-1,4,5,8-tetraazadacalin （TNAD） with Some Propellants

Molecular dynamic simulation was employed to predict the melting points Tm of TNAD/HMX, TNAD/RDX, TNAD/DINA, and TNAD/DNP systems （tans-1,4,5,8- tetranitro-1,4,5,8-tetraazadacalin （TNAD）, dinitropiperazine （DNP）, cyclotetramethylenetetranitroamine （HMX）, cyclotrimethylenetrinitramine （RDX）, and N-nitrodihydroxyethylaminedinitrate （DINA））. Tm was determined from the inflexion point on the curve of mean specific volume vs. temperature. The result shows that the Tm values of TNAD/HMX, TNAD/RDX, and TNAD/DINA systems are 500, 536, and 488 K, respectively. The TNAD/DNP system has no obvious Tm value, which shows the system is insoluble. Using Tm, the solubility of the four systems was analyzed. The radial distribution functions of the four systems were analyzed and the main intermolecular forces between TNAD and other energetic components are short-range interactions. The better the solubility is, the stronger the intermoleenlar interaction is. In addition, the force field energy at different temperature was also analyzed to predict Tm of the four systems.

ANALYSIS OF DYNAMIC RESPONSE OF AN IMPACTED ELASTIC PLATE

In [1], the dynamic response of an impacted elastic plate is analysed. Using the method in [1] is on condition that impacting body is rigid and the relation between impact reacting .force and partial deformation is known In this paper. Simulate formula of impact reacting force. function is presented. Without assumption of impacting body, dynamic response in impact procedure is considered avoiding the problem of partial deformation. Because of analysis by law of momentum conservation. impulse theorem, dynamic differential equation and numerical method the method in this paper is more suitable for application. Examples of the application are given. In precision, solution in this paper is identical with known correct solution

Global Convergence of a New Restarting Conjugate Gradient Method for Nonlinear Optimizations

Conjugate gradient optimization algorithms depend on the search directions with different choices for the parameters in the search directions. In this note, by combining the nice numerical performance of PR and HS methods with the global convergence property of the class of conjugate gradient methods presented by HU and STOREY(1991), a class of new restarting conjugate gradient methods is presented. Global convergences of the new method with two kinds of common line searches, are proved. Firstly, it is shown that, using reverse modulus of continuity function and forcing function, the new method for solving unconstrained optimization can work for a continously dif ferentiable function with Curry-Altman's step size rule and a bounded level set. Secondly, by using comparing technique, some general convergence properties of the new method with other kind of step size rule are established. Numerical experiments show that the new method is efficient by comparing with FR conjugate gradient method.

Global Convergence of a New Restarting Three Terms Conjugate Gradient Method for Non-linear Optimizations

In this note,by combining the nice numerical performance of PR and HS methods with the global convergence property of FR method,a class of new restarting three terms conjugate gradient methods is presented.Global convergence properties of the new method with two kinds of common line searches are proved.

Global Convergence of a New Conjugate Gradient Methods with a Modification of the Curry-Altman Step-size Rule

Conjugate gradient optimization algorithms depend on the search directions with different choices for the parameter in the search directions. In this note, conditions are given on the parameter in the conjugate gradient directions to ensure the descent property of the search directions. Global convergence of such a class of methods is discussed. It is shown that, using reverse modulus of continuity function and forcing function, the new method for solving unconstrained optimization can work for a continuously differentiable function with a modification of the Curry-Altman's step-size rule and a bounded level set. Combining PR method with our new method, PR method is modified to have global convergence property.Numerical experiments show that the new methods are efficient by comparing with FR conjugate gradient method.

Switched forced SEIRDV compartmental models to monitor COVID-19 spread and immunization in Italy

This paper presents a new hybrid compartmental model for studying the COVID-19 epidemic evolution in Italy since the beginning of the vaccination campaign started on 2020/12/27 and shows forecasts of the epidemic evolution in Italy in the first six months.The proposed compartmental model subdivides the population into six compartments and extends the SEIRD model proposed in[E.L.Piccolomini and F.Zama,PLOS ONE,15(8):1e17,082020]by adding the vaccinated population and framing the global model as a hybridswitched dynamical system.Aiming to represent the quantities that characterize the epidemic behaviour from an accurate fit to the observed data,we partition the observation time interval into sub-intervals.The model parameters change according to a switching rule depending on the data behaviour and the infection rate continuity condition.In particular,we study the representation of the infection rate both as linear and exponential piecewise continuous functions.We choose the length of sub-intervals balancing the data fit with the model complexity through the Bayesian Information Criterion.We tested the model on italian data and on local data from Emilia-Romagna region.The calibration of the model shows an excellent representation of the epidemic behaviour in both cases.Thirty days forecasts have proven to well reproduce the infection spread,better for regional than for national data.Both models produce accurate predictions of infected,but the exponential-based one perform better in most of the cases.Finally,we discuss different possible forecast scenarios obtained by simulating an increased vaccination rate.

Adsorption and desorption of SO_2, NO and chlorobenzene on activated carbon

Activated carbon（AC） is very effective for multi-pollutant removal; however, the complicated components in flue gas can influence each other＇s adsorption. A series of adsorption experiments for multicomponents, including SO_2, NO, chlorobenzene and H2 O,on AC were performed in a fixed-bed reactor. For single-component adsorption, the adsorption amount for chlorobenzene was larger than for SO_2 and NO on the AC. In the multi-component atmosphere, the adsorption amount decreased by 27.6% for chlorobenzene and decreased by 95.6% for NO, whereas it increased by a factor of two for SO_2,demonstrating that a complex atmosphere is unfavorable for chlorobenzene adsorption and inhibits NO adsorption. In contrast, it is very beneficial for SO_2 adsorption. The temperature-programmed desorption（TPD） results indicated that the binding strength between the gas adsorbates and the AC follows the order of SO_2〉 chlorobenzene 〉 NO. The adsorption amount is independent of the binding strength. The presence of H2 O enhanced the component effects, while it weakened the binding force between the gas adsorbates and the AC. AC oxygen functional groups were analyzed using TPD and X-ray photoelectron spectroscopy（XPS） measurements. The results reveal the reason why the chlorobenzene adsorption is less affected by the presence of other components. Lactone groups partly transform into carbonyl and quinone groups after chlorobenzene desorption. The chlorobenzene adsorption increases the number of C = O groups, which explains the positive effect of chlorobenzene on SO_2 adsorption and the strong NO adsorption.

Atomic and electronic structure of Si dangling bonds in quasi-free-standing monolayer graphene

Si dangling bonds at the interface of quasi-free-standing monolayer graphene （QFMLG） are known to act as scattering centers that can severely affect carrier mobility Herein, we investigate the atomic and electronic structure of Si dangling bonds in QFMLG using low-temperature scanning tunneling microscopy/ spectroscopy （STM/STS）, atomic force microscopy （AFM）, and density functional theory （DFT） calculations. Two types of defects with different contrast were observed on a flat graphene terrace by STM and AFM; in particular, their STM contrast varied with the bias voltage. Moreover, these defects showed characteristic STS peaks at different energies, 1.1 and 1.4 eV. The comparison of the experimental data with the DFT calculations indicates that the defects with STS peak energies of 1.1 and 1.4 eV consist of clusters of three and four Si dangling bonds, respectively. The relevance of the present results for the optimization of graphene synthesis is discussed.