Key Techniques and Applications of Adaptive Growth Method for Stiffener Layout Design of Plates and Shells

The application of the adaptive growth method is limited because several key techniques during the design process need manual intervention of designers. Key techniques of the method including the ground structure construction and seed selection are studied, so as to make it possible to improve the effectiveness and applicability of the adaptive growth method in stiffener layout design optimization of plates and shells. Three schemes of ground structures, which are comprised by different shell elements and beam elements, are proposed. It is found that the main stiffener layouts resulted from different ground structures are almost the same, but the ground structure comprised by 8-nodes shell elements and both 3-nodes and 2-nodes beam elements can result in clearest stiffener layout, and has good adaptability and low computational cost. An automatic seed selection approach is proposed, which is based on such selection rules that the seeds should be positioned on where the structural strain energy is great for the minimum compliance problem, and satisfy the dispersancy requirement. The adaptive growth method with the suggested key techniques is integrated into an ANSYS-based program, which provides a design tool for the stiffener layout design optimization of plates and shells. Typical design examples, including plate and shell structures to achieve minimum compliance and maximum bulking stability are illustrated. In addition, as a practical mechanical structural design example, the stiffener layout of an inlet structure for a large-scale electrostatic precipitator is also demonstrated. The design results show that the adaptive growth method integrated with the suggested key techniques can effectively and flexibly deal with stiffener layout design problem for plates and shells with complex geometrical shape and loading conditions to achieve various design objectives, thus it provides a new solution method for engineering structural topology design optimization.

ASYMPTOTIC ANALYSIS OF PLANE-STRAIN MODE I STEADY-STATE CRACK GROWTH IN TRANSFORMATION TOUGHENINGCERAMICS(Ⅱ)

Based on a constitutive law which includes the shear components oftransformation plasticity. the asymptotic solutions to near-tip fields of plane-strainmode I steadity propagating cracks in rransformed ceramics are obtained for the caseof linear isotropic hardening. The Stress singularity. the distributions of stresses andvelocities at the crack tip are determmed for various material parameters. The factorsinfluencing the near-tip fields are discussed in detail.

Solvent Synthesis,Growth Mechanism and Photocatalytic Properties of AgInS_2 Nanoplate and Nanoparticle

Orthorhombic AgInS2 nanoplate and nanoparticle were synthesized using pyridine and 1-dodecanethiol as the solvent.The obtained products were characterized by X-ray diffraction（XRD）,field-emission scanning electron microscope（FESEM）,field-emission transmission electron microscope（FETEM）,and the possible growth mechanism of AgInS2 was also proposed by the exploration of reaction temperature and time.Meanwhile,the bandgap of AgInS2 was calculated by the UV-Vis diffuse reflectance spectrum,and the photocatalytic activity was also investigated.Those experimental results indicate that the reaction temperature,reaction time and solvent have an influence on phase and morphology of AgInS2,and both AgInS2 nanoplate and nanoparticle have some ability on photocatalytic degradation of organic dyes under UV-Vis light irradiation.

Synthesis of AgCl/Ti_(3)C_(2)@TiO_(2)Ternary Composite Photocatalysts for Photocatalytic Oxidation of 1,4-Dihydropyridine and Tetracycline Hydrochloride

AgCl/Ti_(3)C_(2)@TiO_(2)ternary composites were prepared to form a heterojunction structure between AgCl and TiO_(2)and introduce Ti3C2 as a cocatalyst.The as-prepared AgCl/Ti_(3)C_(2)@TiO_(2)composites showed higher photocatalytic activity than pure AgCl and Ti_(3)C_(2)@TiO_(2)for photooxidation of a 1,4-dihydropyridine derivative(1,4-DHP)and tetracycline hydrochloride(TCH)under visible light irradiation(λ>400 nm).The photocatalytic activity of AgCl/Ti_(3)C_(2)@TiO_(2)composites depended on Ti_(3)C_(2)@TiO_(2)content,and the catalytic activity of the optimized samples were 6.9 times higher than that of pure AgCl for 1,4-DHP photodehydrogenation and 7.3 times higher than that of Ti_(3)C_(2)@TiO_(2)for TCH photooxidation.The increased photocatalytic activity was due to the formation of a heterojunction structure between AgCl and TiO_(2)and the introduction of Ti3C2 as a cocatalyst,which lowered the internal resistance,sped up the charge transfer,and increased the separation efficiency of photogenerated carries.Photogenerated holes and superoxide radical anions were the major active species in the photocatalytic process.

Crystal and electronic structure of a quasi-two-dimensional semiconductor Mg_(3)Si_(2)Te_(6)

We report the synthesis and characterization of a Si-based ternary semiconductor Mg_(3)Si_(2)Te_(6),which exhibits a quasitwo-dimensional structure,where the trigonal Mg_(3)Si_(2)Te_(6)layers are separated by Mg ions.Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure.The experimentally determined direct band gap is 1.39 eV,consistent with the value of the density function theory calculations.Our results reveal that Mg_(3)Si_(2)Te_(6)is a direct gap semiconductor,which is a potential candidate for near-infrared optoelectronic devices.

Controllable growth of two-dimensional quantum materials

Two-dimensional(2D)quantum materials have attracted extensive attention due to their superior properties at the atomic thickness.Numerous novel physical phenomena,including the quantum Hall effect,fractional quantum Hall effect,quantum anomalous Hall effect and topological superconductor phase or topological insulator phase,have been discovered on different2D quantum materials.Over the past decades,various technologies have been developed to prepare the 2D quantum materials and all of them have demonstrated their specific advantages.In this review,we comprehensively summarize the commonly used growth methods for the 2D quantum materials and discuss the corresponding controllable growth strategies.Finally,we provide a summary and a perspective for future studies.

Engineering miniature gold nanorods with tailorable plasmonic wavelength in NIR region via ternary surfactants mediated growth

Plasmonic nanoparticles are endowed profound capability for sensing,biomedicine,and cancer therapy.However,the inaccessibly adjustable wavelength in near infrared(NIR)region window and size limit for the particles penetration in tumor strongly hinder their developments.Miniature gold nanorods(mini-Au NRs)with diameter less than 12 nm can effectively address this challenge due to the tiny size and tailorable NIR absorption.Herein,we adopt ternary surfactants(hexadecyl trimethyl ammonium bromide(CTAB),sodium oleate(NaOL),and sodium salicylate(NaSal))mediated growth strategy to precisely synthesize miniature Au NRs under micelle space-confinement.Importantly,the selectively dense accumulation of ternary surfactants can efficiently improve the micellar stacking parameters(p)and lower micellar free energy(F),further tends to achieve the formation of Au NRs with tiny diameter and high purity.Compared with that of conventional methods,the purity of mini-Au NRs up to 100%can be dramatically improved via varying the relative concentration of ternary surfactants.The diameter of Au NRs can be dynamically controlled to 6,8,and 11 nm through regulating the concentration of silver nitrate and the mole ratio of ternary surfactants.Such ternary surfactants system is favorable for the aging of tiny Au NRs,and further enables the aspect ratio-tunable in the region from 2.70 to 7.32,as well as tailorable plasmonic wavelength in wide NIR window from 700 to 1,147 nm.Therefore,our findings shed a light on the precise preparation of small sized plasmonic nanoparticles and pave the way to applications in biomedicine,imaging,and cancer therapy.

In situ synthesis of a spherical covalent organic framework as a stationary phase for capillary electrochromatography

Covalent organic frameworks(COFs)are a novel type of crystalline porous organic polymer materials recently developed.It has several advantages in chromatographic separation field,such as high thermal stability,porosity,structural regularity,and large specific surface area.Here,a novel spherical COF 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde(BPTA)was developed as an electrochromatographic stationary phase for capillary electrochromatography separation.The COF TAPB-BPTA modified capillary column was fabricated via a facile in situ growth method at room temperature.The characterization results of scanning electron microscopy(SEM),Fourier transform infrared(FT-IR)spectroscopy,and X-ray diffraction(XRD)confirmed that COF TAPB-BPTA were successfully modified onto the capillary inner surface.The electrochromatography separation performance of the COF TAPB-BPTA modified capillary was investigated.The prepared column demonstrated outstanding separation performance toward alkylbenzenes,phenols,and chlorobenzenes compounds.Furthermore,the baseline separations of non-steroidal anti-inflammatory drugs(NSAIDs)and parabens with good efficiency and high resolution were achieved.Also,the prepared column possessed satisfactory precision of the intra-day runs(n=5),inter-day runs(n=3),and parallel columns(n=3),and the relative standard deviations(RSDs)of the retention times of tested alkylbenzenes were all less than 2.58%.Thus,this new COF-based stationary phase shows tremendous application potential in chromatographic separation field.

Preparation of Gold Nanorods of High Quality and High Aspect Ratio

We report the synthesis of gold nanorods （NRs） by seed-mediated growth method. A small amount of different shapes such as triangles, hexagons and a large amount of rods are obtained by varying the proportion of seed to metal salt, adding NaOH to growth solution as well as using the seed solution of CTAB-capped agent. The gold nanorod （NR） formation yield is improved. Meanwhile, the growth mechanism of high yield gold NRs is discussed. The high quality single size NRs can be separated from polydisperse samples using surfactant-assisted nanorod self-assembly. The gold NRs synthesized were characterized by transmission electron microscopy （TEM） and UV-vis spectroscopy.

KLN晶体生长与蓝光SHG特性

In this paper,ferroelectric tetragonal tungsten bronze type potassium lithium niobate(KLN)crystal with a size of 20mm×8mm×43mm was grown from a melt with a composition of 32mol% K 2CO 3,24mol% Li 2CO 3 and 44mol% Nb 2O 5 by the top seeded solution growth (TSSG)method.The KLN crystal as grown along [110]axis has a perfect crystal melt interface dominated by {110} and {210} facets.Lattice constants were measured by X ray diffraction (XRD) analysis performed on {001}and {110}natural faces of single crystal samples.The anisotropic thermal expansion behavior of the crystal was also studied along [001] and [110] axes,respectively by using a Shimadzu TMA 50 thermomechnical analyzer.For the purpose of crystal poling,the dependence of crystal capacitance vs.temperature in both heating and cooling cycles was measured and the ferroelectric Curie temperature was determined to be 514℃.The crystal was poled at 506℃ with a dc field of about 250 V/cm along the c axis of the sample,for a time corresponding to about 1.5 h/cm.The blue second harmonic generation (SHG)characteristics of the KLN crystal were investigated by using a 3900s Ti∶sapphire CW tunable laser.Blue laser light at wavelength 432nm was obtained by the non critical phase matching (NCPM)SHG at room temperature.Based on the wavelength and temperature tuning curves for the NCPM SHG,the wavelength acceptance and temperature acceptance of this KLN crystal were measured.The crystal property homogeneity along the <110>growth axis was also studied by measuring the room temperature NCPM wavelength at different growth positions.

Optical Spectroscopic Properties of Yb^(3+)-Doped MgMoO_4 Crystal Grown by the TSSG Method

This paper reports the growth and spectral assessments of Yb^（3＋） ion doped MgMoO_4（Yb^（3＋）：MgMoO_4） crystal grown by the TSSG method. Polarized spectral properties of Yb^（3＋）：MgMoO_4 crystal, including absorption and emission cross-sections, absorption FWHM and fluorescence lifetime, have been investigated. The laser performance parameters bmin, Isat and Iminhave also been evaluated. All the investigated results show the Yb^（3＋）-doped MgMoO_4 crystal is expected as a promising candidate for ultrashort pulse and tunable lasers.

Optical and scintillation properties of Ce:Y_(3)Al_(5)O_(12) single crystal fibers grown by laser heated pedestal growth method

The single crystal scintillating optical fibers acting as the scintillators and light conductors show potential application in scintillating fiber array detectors with high spatial resolution.In this paper we report the growth of 0.2 at%Ce:Y_(3)Al_(5)O_(12) single crystal fiber.The crystalline phase,surface morphology of the axialsection and cro ss-section,optical and scintillation properties of the as-grown fiber were investigated.The Ce:Y_(3)Al_(5)O_(12) single crystal fiber has a pure YAG phase,a uniform distribution of cerium in the axialsection and cross-section surface.Emission spectrum is composed of broad bands ranging from 440 to700 nm.In addition,the single crystal fiber has a high light yield of 26115±2000 photons/MeV,low energy resolution of 9.44%@662 keV and decay time of a fast component of 78 ns and a slow component of 301 ns.The intensity ratio of fast to slow components is roughly 8:1.

An in situ growth method for property control of LPCVD polysilicon film

Polysilicon films deposited by low-pressure chemical vapor deposition (LPCVD) exhibit large residual stress and stress gradient, depending on the deposition condition. An in situ growth method based on multilayer concept is presented to control the property for as-deposited polysilicon. A 3-μm thick polysilicon film with nine layers structure is demonstrated under the detailed analysis of multi-layer theory and material characteristic of polysilicon. The results show that a 3-μm-thick polysilicon film with 8-MPa overall residual tensile stress and 2.125-MPa/μm stress gradient through the film thickness is fabricated successfully.

GROWTH AND CHARACTERIZATION OF Na_(0.5)Bi_(0.5)TiO_(3)-K_(0.5)Bi_(0.5)TiO_(3)LEAD-FREE PIEZOELECTRIC CRYSTAL BY THE TSSG METHOD

The 0.96Na_(0.5)Bi_(0.5)TiO_(3)-0.04K_(0.5)Bi_(0.5)TiO_(3)(NKBT96/4)lead-free single crystal was successfullygrown by top-seeded solution growth method.The effective segregation coefficient for K was calculated to be 0.20.X-ray powder difraction measurement showed that the as-grown crystalpossesses rhombohedral perovskite structure at room temperature.X-ray rock curve measureindicated that the as-grown single crystal owned relatively higher quality.The NKBT96/4 singlecrystal exhibits apparent diffused dielectric behavior,where the diffusiveness index aαis 1.79 forthe[001]-oriented crystal planes.A notable thermal hysteresis,△T_(h),of 25℃was disclosed for thetetragonal antiferroelectric-tetragonal paraelectric phase transition in the dielectric propertystudies between heating and cooling.The highest remnant polarization,P_(r),16.8μC/cm^(2),wasobtained at 100℃.The electromechanical coupling coefficient k_(t)of the[001]-oriented crystalplanes at room temperat ure was determined to be 38%using resonance-antiresonance technique.The room temperature piezoelectric constant d_(33)reaches 120 pC/N.

Recent advances on two-dimensional metal halide perovskite x-ray detectors

In recent years,two-dimensional metal halide perovskites(MHPs)have attracted increased attention for radiation detection and imaging.Their detection efficiencies are almost comparable to three-dimensional(3D)perovskites.Meanwhile,they demonstrate superior stability to 3D perovskites.The pursuit of high-quality,phase-pure and lead-free two-dimensional MHP materials and large-area fabrication capability for x-ray detectors are among the research hotspots.In this review,we first give a brief introduction of the crystallographic structure,optoelectronic characteristics and preparation methods of high-quality two-dimensional perovskites.In addition,we overview the general working principles of direct and indirect x-ray detection processes and the corresponding performance metrics from the perspective of detection and imaging.Furthermore,we provide a comprehensive discussion on the recent advances in 2D perovskite x-ray detectors and imaging devices.Finally,we pinpoint several major obstacles of 2D x-ray detectors that should be overcome in the near future.

Geometry and size optimization of stiffener layout for three-dimensional box structures with maximization of natural frequencies

Based on the growth mechanism of natural biological branching systems and inspiration from the morphology of plant root tips,a bionic design method called Improved Adaptive Growth Method(IAGM)has been proposed in the authors’previous research and successfully applied to the reinforcement optimization of three-dimensional box structures with respect to natural frequencies.However,as a kind of ground structure methods,the final layout patterns of stiffeners obtained by using the IAGM are highly subjected to their ground structures,which restricts the optimization effect and freedom to further improve the dynamic performance of structures.To solve this problem,a novel post-processing geometry and size optimization approach is proposed in this article.This method takes the former layout optimization result as start,and iteratively finds the optimal layout angles,locations,and lengths of stiffeners with a few design variables by optimizing the positions of some specific node lines called active node lines.At the same time,thick-nesses of stiffeners are also optimized to further improve natural frequencies of three-dimensional box structures.Using this method,stiffeners can be successfully separated from their ground structures and further effectively improve natural frequencies of three-dimensional box structures with less material consumption.Typical numerical examples are illustrated to validate the effectiveness and advantages of the suggested method.

Room temperature in-situ preparation of hydrazine-linked covalent organic frameworks coated capillaries for separation and determination of polycyclic aromatic hydrocarbons

Covalent organic frameworks(COFs)have been increasingly used in capillary electrochromatography due to their excellent characteristics.In this work,hydrazine-linked TFPB-DHzDS(TFPB:1,3,5-tris(4-formylphenyl)benzene;DHzDS:2,5-bis(3-(ethylthio)propoxy)terephthalohydrazide)was first synthesized by a simpler and easier method at room temperature and introduced into capillary electrochromatography as coating material.The TFPB-DHzDS coated capillaries were prepared by an in-situ growth process at room temperature.After optimizing the coating concentration and experimental conditions of capillary electrochromatography,baseline separation of two groups of polycyclic aromatic hydrocarbons was achieved based on the TFPB-DHzDS coated capillary.And the established method was used successfully to determine PAHs in natural water and soil samples.The spiked recoveries of polycyclic aromatic hydrocarbons in these samples ranged from 90.01%to 111.0%,indicating that the method is reliable and could detect polycyclic aromatic hydrocarbons in natural samples.Finally,molecular simulation was applied to study and visualize the interaction between the analytes and coating COF materials to investigate the molecular level separation mechanism further.

金属卤化物钙钛矿材料生长方法研究进展

钙钛矿材料尤其是金属卤化物钙钛矿具有优异的性能,如较大的光系数、较高的载流子迁移率、较长的载流子寿命、可调谐的电阻率、较大的X射线衰减系数和简单的处理工艺等.这些优点使得钙钛矿材料在光电领域,如太阳能电池、发光二极管、光电探测器、X/γ射线探测器和激光等研究领域引起了广泛关注.钙钛矿材料的广泛应用依赖于高质量的钙钛矿晶体或薄膜.截至目前,已经涌现出众多的钙钛矿生长技术和方法.本综述分类总结了近年来用于钙钛矿材料生长的主要方法和手段,包括溶液降温法、逆温结晶法、反溶剂法、旋涂法和化学气相沉积法等.通过总结与分析,发现溶液降温法、逆温结晶法、反溶剂法主要用于生长高质量的钙钛矿单晶,旋涂法在制备钙钛矿薄膜方面具有较大优势,而化学气相沉积法则在制备多种形貌的微纳钙钛矿材料方面占据优势.本综述可为科研人员在钙钛矿材料生长方面提供可参考的依据和具体参数.

Impact of Climate Change on Maize Potential Productivity and the Potential Productivity Gap in Southwest China

The impact of climate change on maize potential productivity and the potential productivity gap in Southwest China（SWC） are investigated in this paper.We analyze the impact of climate change on the photosynthetic,light-temperature,and climatic potential productivity of maize and their gaps in SWC,by using a crop growth dynamics statistical method.During the maize growing season from 1961 to 2010,minimum temperature increased by 0.20℃ per decade（p 〈 0.01） across SWC.The largest increases in average and minimum temperatures were observed mostly in areas of Yunnan Province.Growing season average sunshine hours decreased by 0.2 h day^（-1） per decade（p 〈 0.01） and total precipitation showed an insignificant decreasing trend across SWC.Photosynthetic potential productivity decreased by 298 kg ha^（-1）per decade（p 〈 0.05）.Both light-temperature and climatic potential productivity decreased（p 〈 0.05） in the northeast of SWC,whereas they increased（p 〈 0.05） in the southwest of SWC.The gap between lighttemperature and climatic potential productivity varied from 12 to 2729 kg ha^（-1）,with the high value areas centered in northern and southwestern SWC.Climatic productivity of these areas reached only 10%-24%of the light-temperature potential productivity,suggesting that there is great potential to increase the maize potential yield by improving water management in these areas.In particular,the gap has become larger in the most recent 10 years.Sensitivity analysis shows that the climatic potential productivity of maize is most sensitive to changes in temperature in SWC.The findings of this study are helpful for quantification of irrigation water requirements so as to achieve maximum yield potentials in SWC.

Spectroscopic properties of ytterbium doped KLu(WO_4)_2

Monoclinic Yb3＋-doped KLu（WO4）2 （Yb：KLuW） crystal with large sizes was grown by top-seeded solution growth （TSSG） method. Room-temperature absorption and fluorescence spectra were measured. The ground-state energy-level splitting was 562 cm–1. The absorption cross section, peak emission cross section as well as the minimum inversion fraction ？min and the minimum absorbed pump intensity Imin were calculated. The measured emission lifetime was 0.676 ms and the emission spectral bandwidth （FWHM） was up to 55 nm. In comparison with established laser crystals the results suggested that this crystal has potential application in efficient tunable and femtosecond laser operation.