Topology Optimization of Compliant Mechanisms with Geometrical Nonlinearities Using the Ground Structure Approach

The majority of topology optimization of compliant mechanisms uses linear finite element models to find the structure responses.Because the displacements of compliant mechanisms are intrinsically large,the topological design can not provide quantitatively accurate result.Thus,topological design of these mechanisms considering geometrical nonlinearities is essential.A new methodology for geometrical nonlinear topology optimization of compliant mechanisms under displacement loading is presented.Frame elements are chosen to represent the design domain because they are capable of capturing the bending modes.Geometrically nonlinear structural response is obtained by using the co-rotational total Lagrange finite element formulation,and the equilibrium is solved by using the incremental scheme combined with Newton-Raphson iteration.The multi-objective function is developed by the minimum strain energy and maximum geometric advantage to design the mechanism which meets both stiffness and flexibility requirements, respectively.The adjoint method and the direct differentiation method are applied to obtain the sensitivities of the objective functions. The method of moving asymptotes（MMA） is employed as optimizer.The numerical example is simulated to show that the optimal mechanism based on geometrically nonlinear formulation not only has more flexibility and stiffness than that based on linear formulation,but also has better stress distribution than the one.It is necessary to design compliant mechanisms using geometrically nonlinear topology optimization.Compared with linear formulation,the formulation for geometrically nonlinear topology optimization of compliant mechanisms can give the compliant mechanism that has better mechanical performance.A new method is provided for topological design of large displacement compliant mechanisms.

Nucleation in Metallic Melt on the Ground and under Elevated Gravity

The expressions for nucleation rate in metallic melt on the ground and under elevated gravity have been derived theoretically and the effects of gravity and elevated gravity on nucleation rate have been discussed. A comparison of nucleation rate under microgravity with those on the ground and under elevated gravity has also been made

CAS-MCSCF Study on the Ground State of the Ditungsten Molecule(W_2)

Complete active space multiconfiguration self-consisten-field (CAS-MCSCF)calculations are carried out on the ground stae() of W_2. The spectroscopic properties(Re=2.078A. De=4.224eV and ωe=304.3cm-1) and the poential energy curve of the state are reported. The calculations predict the W-W bond order of 5.02.

An approach to estimate tree height using PolInSAR data constructed by the Sentinel-1 dual-pol SAR data and RVoG model

We estimate tree heights using polarimetric interferometric synthetic aperture radar(PolInSAR)data constructed by the dual-polarization(dual-pol)SAR data and random volume over the ground(RVoG)model.Considering the Sentinel-1 SAR dual-pol(SVV,vertically transmitted and vertically received and SVH,vertically transmitted and horizontally received)configuration,one notes that S_(HH),the horizontally transmitted and horizontally received scattering element,is unavailable.The S_(HH)data were constructed using the SVH data,and polarimetric SAR(PolSAR)data were obtained.The proposed approach was first verified in simulation with satisfactory results.It was next applied to construct PolInSAR data by a pair of dual-pol Sentinel-1A data at Duke Forest,North Carolina,USA.According to local observations and forest descriptions,the range of estimated tree heights was overall reasonable.Comparing the heights with the ICESat-2 tree heights at 23 sampling locations,relative errors of 5 points were within±30%.Errors of 8 points ranged from 30%to 40%,but errors of the remaining 10 points were>40%.The results should be encouraged as error reduction is possible.For instance,the construction of PolSAR data should not be limited to using SVH,and a combination of SVH and SVV should be explored.Also,an ensemble of tree heights derived from multiple PolInSAR data can be considered since tree heights do not vary much with time frame in months or one season.

Roaming About the Ground Stalls ——A Special Scene in Beijing

NOT quite as overwhelming as the GreatWall, Forbidden City or Chinese Opera,roaming amongst the stalls scattered on theground at markets like Beijing’s Panjiayuanis nevertheless a cultural experience uniqueto China.

Probing Structure, Thermochemistry, Electron Affinity and Magnetic Moment of Dysprosium-doped Silicon Clusters DySi_n(n = 3～10) and Their Anions with Double-hybrid Density Functional Theory

The equilibrium geometries, electronic structures and electronic properties including adiabatic electron affinity（AEA）, vertical detachment energy（VDE）, simulated photoelectron spectroscopy, HOMO-LUMO gap, charge transfer, and magnetic moment for DySi_n（n = 3~10） clusters and their anions were systematically investigated by using the ABCluster global search technique combined with the B3 LYP and B2 PLYP density functional methods. The results showed that the lowest energy structure of neutral DySi_n（n = 3~10） can be regarded as substituting a Si atom of the ground state structure of Si_（n＋1） with a Dy atom. For anions, the extra electron effect on the structure is significant. Starting from n = 6, the lowest energy structures of DySi_n~？（n = 3~10） differ from those of neutral. The ground state is quintuplet electronic state for DySi_n（n = 3~10） excluding DySi_4 and DySi_9, which is a septet electronic state. For anions, the ground state is a sextuplet electronic state. The reliable AEA and VDE of DySi_n（n = 3~10） are reported. Analyses of HOMO-LUMO gaps indicated that doping Dy atom to silicon clusters can improve significantly their photochemical reactivity, especially for DySi_9. Analyses of NPA revealed that the 4 f electrons of Dy in DySi_4, DySi_9, and DySi_n~？ with n = 4 and 6~10 participate in bonding. That is, DySi_nbelongs to the AB type. The 4 f electrons of Dy atom provide substantially the total magnetic moments for DySi_n and their anions. The dissociation energies of Ln（Ln = Pr, Sm, Eu, Gd, Ho, and Dy） fromLn Sin and their anions were evaluated to examine the relative stabilities.

Simulation of the water level influence on the difference within the water-tube tiltmeter in Shuangyang Lake

This article analyzes the relationship between the water level and the water-tube tilting in Shuangyang lake,based on the differential deformation features reflected by the NS and EW components of the water-tube tiltmeter.The results show a good spatiotemporal consistency between the variation of water level and the NS tilt component,which is considered to be affected by the magnitude and duration of the water level variation in Shuangyang Lake.The article uses Landsat remote sensing image data to extract the water boundary of Shuan-gyang Lake,and takes advantage of the finite element numerical simulation method to build three-dimensional models for different geological structural conditions of the Shuangyang seismostation.The simulation results show that when the underground medium is granite,the effect of water level variation on the vertical displacement of the surface is non-directional.With a 50-m soil layer in Model 2,the simulated NS tilt variation is equivalent to the actual observed water-tube tiltmeter NS component when the water level variation is 0.44 m and 0.8m.When the variation of water level reaches 2.0m,the simulation result of the NS component is 79.6 ms,which is slightly larger than the observed result of 60.32 ms.However,the simulation results show that the variation of the EW component is significantly smaller than that of the NS one.Due to the fact that the Shuan-gyang lake is long in the NS direction and short in the EW direction,the existence of the soil layer tends to generate ground deformation along the NS direction in the vicinity of the lake after the increase of water level,thereby resulting in the difference of the ground deformation in the two directions.

Sudden birth and sudden death of thermal fidelity in a two-qubit system

We study the energy level crossing and the thermal fidelity in a two-qubit system with the presence of a transverse inhomogeneous magnetic field.With the help of contour plots,we clearly identify the ground states of the system in different regions of parameter space,and discuss the corresponding energy level crossing.The fidelity between the ground state of the system and the state of the system at temperature T is calculated.The result shows that the fidelity is very sensitive to the magnetic field anisotropic factor,indicating that this factor may be used as a controller of the fidelity.The influence of the Yangian transition operators on the fidelity of the system is discussed.We find that the Yangian operators can change the fidelity dramatically and give rise to sudden birth and sudden death phenomena of the thermal fidelity.This makes the corresponding Yangian operators possible candidates for switchers to turn the fidelity on and off.

Ground and Shallow Ground Temperature Changes Trends in Sanhe City in 40 Years

[ Objective] The aim was to analyze the ground and shallow ground temperature trend in Sanhe in recent 40 years. [ Method] According to the annual and seasonal average ground temperature in 2010, by dint of line charts and trend diagram, the ground temperature in Sanhe City in recent 40 years was discussed. [ Result] The annual ground temperature, annual ground highest and lowest temperature in Sanhe City in recent 40 years was increasing. The lowest temperature in annual and seasonal surface temperature increased at fastest speed. The annual changes of the 5, 10, 15 and 20 cm ground temperature was decreasing and the 20 cm ground temperature decreased most significantly. In spring, the 5 -15 cm ground temperature increased and the 20 cm reduced. In summer, the 20 cm temperature decreased significantly. In autumn, the 10 cm ground temperature enhanced fastest. In winter, the 10 cm and 15 cm temperature increase rate was large and the 15 cm temperature increased fastest. [ Conclusion] The study provided reference for the influence of global warming on the ground and shallow ground temperature.

Vertical Observations and Analysis of PM_(2.5),O_3,and NO_x at Beijing and Tianjin from Towers during Summer and Autumn 2006

During the period between 18 August and 22 September 2006, an ultraviolet photometric O3 analyzer, a NO-NO2-NOx chemiluminescence analyzer, and a quartz micro-oscillating-scale particle concentration analyzer were simultaneously used for monitoring at three different heights each at Beijing （325-m tower） and Tianjin （255-m tower）. These towers belong to the Institute of Atmospheric Physics （IAP） of the Chinese Academy of Sciences （CAS） and to the Tianjin Municipal Meteorological Bureau, respectively. These measurements were used to continuously measure the atmospheric O3 and NOx volume-by-volume concentrations and the PM2.5 mass concentration within a vertical gradient. When combined with meteorological data and information on the variation of vertical characteristics of the various atmospheric pollutants in the two cities, analysis shows that these two cities were seriously polluted by both PM2.5 and O3 during summer and autumn. The highest daily-average concentrations of PM2.5 near the ground in Beijing and Tianjin reached 183 μgm a and 165 μg m^-3, respectively, while the 03 concentrations reached 52 ppb and 77 ppb, and NOx concentrations reached 48 ppb and 62 ppb for these two cities, respectively. The variations in the daily-average concentrations of PM2.5 between Beijing and Tianjin were demonstrated to be consistent over time. The concentrations of PM2.5 measured in Beijing were found to be higher than those in Tianjin. However, the overall O3 concentrations near the ground in Tianjin were higher than in Beijing. NOx concentrations in Tianjin were consistently lower than in Beijing. It was also found that PMz5 pollution in Beijing＇s atmosphere may also be affected by the pollutants originating in and delivered from Tianjin, and that Tianjin was impacted by Beijing＇s pollutants at a significantly reduced level.

Patterns of tree buttressing at Lawachara National Park, Bangladesh

We describe patterns of buttress formation and development in eleven tree species at Lawachara National Park, Bangladesh. Forty-five percent of trees of these 11 species had buttresses. Artocarpus chaplasha Roxb. showed maximum （87%） buttress formation, whereas Alstonia scholaris （L.） R. Br. did not show any buttress. Buttresses were recorded in 20%-40% of trees of six species and 40%-60% of trees in three species. Mean length and height of buttress varied among the species and ranged from 0.37-4.37 m and 0.71-2.13 m, respectively. Buttress height, mean buttress length, total buttress length, and total length plus length of secondaries increased with DBH （diameter at breast height） and tree height. Buttress number did not increase with DBH or tree height. Under-storey and mid-canopy trees produced less developed buttresses than did emergent trees （p〈0.01）. Wood density showed moderate effects on buttress characters （p〈0.05）, while the slope of the land did not. Canopy category was a primary regulating factor for tree buttressing, suggesting that buttresses are mechanical adaptations of trees to counter physical stresses.

Simulation and analysis for anthropogenic heat release

Heat balance of urban ecosystem is a key point for the study of urban climate and micro-climate pattern and its change mechanism. Urban heat island effect is becoming increasingly serious,which is mainly caused by the change of the earth's surface cover and the anthropogenic heat release. In this study,the simulation experiment for the anthropogenic heat release was designed according to the heat balance principle. A set of buildings of miniature city were used to constitute the residential area,U grooves were applied to simulate the single building,and the fluorescent lamps in the U groove were regarded as the heat sources of the anthropogenic heat release. The simulation experiment was launched with long-short wave sun photometer,sonic anemothermometer and heat flow gauge in the experiment site. Then the net solar radiation,sensible heat flux and heat flux into the ground were determined. The quantities of the anthropogenic heat release were calculated based on the heat balance principle,and were compared with the theoretical power consumption of the fluorescent lamps. The root mean square error( RMSE) of the simulation for the anthropogenic heat release reaches0. 078 W·m- 2,a comparatively high precision,which showes that the anthropogenic heat release can be accurately determined through the simulation experiments. This study provided a scientific method for the purpose of monitoring the anthropogenic heat release.

Properties of polaron in a triangular quantum well induced by the Rashba effect

The properties of the weakly-coupling bound polaron, considering an influence of Rashba effect, which is brought about by the spin-orbit （SO） interaction, in an semiconductor triangular quantum well （TQW）, have been studied by using the linear combination operator and the unitary transformation methods. We obtain an expression for the ground state energy of the weak-coupling and bound polaron in a TQW as a function of the coupling constant, Coulomb bound potential, and the electron areal density. Our numerical resuks show that the ground state energy of the polaron is composed of four parts, one part is caused by the electrons＇ own energy, the second part is caused by the Rashba effect, the third part occurs because of the Coulomb bound potential, and the last term is induced by the interaction between the electrons and LO phonons. The interactions between the orbit and the spin with different directions have different effects on the ground state energy of the polaron.

Structural and Electronic Properties of Lutetium Doped Germanium Clusters LuGen^((+/0/-))(n=6~19):A Density Functional Theory Investigation

Structural growth mechanism,energetics,and electronic properties of cationic,neutral,and anionic lutetium doped germanium cluster LuGen^((+/0/-))(n=6~19)were comprehensively studied by the ABCluster unbiased global search technique with a hybrid density functional theory approach.Compared to the experimental PES,the anion evolution of structure can be clearly defined as four-phase:from the adsorbed to the link structure,then to the half cage motif,and finally to the endohedral structure.The results revealed that the LuGe16-as Frank-Kasper structure with high symmetry of Td can greatly enhance the stabilities.Doped structures have shown thermodynamic stability and appropriate energy gap.These materials are suitable semiconductors.Various approaches,including quasi-spherical geometry with closed-shell model,aromaticity,UV-Vis spectra,density of states(DOS)and partial density of states(PDOS)were applied to further support the results.