Suppression of low-frequency ultrasound broadband vibration using star-shaped single-phase metamaterials

In order to suppress the low-frequency ultrasound vibration in the broadband range of 20 k Hz—100 k Hz,this paper proposes and discusses an acoustic metamaterial with low-frequency ultrasound vibration attenuation properties,which is configured by hybrid arc and sharp-angle convergent star-shaped lattices.The effect of the dispersion relation and the bandgap characteristic for the scatterers in star-shaped are simulated and analyzed.The target bandgap width is extended by optimizing the geometry parameters of arc and sharp-angle convergent lattices.The proposed metamaterial configured by optimized hybrid lattices exhibits remarkable broad bandgap characteristics by bandgap complementarity,and the simulation results verify a 99%vibration attenuation amplitude can be obtained in the frequency of20 k Hz—100 k Hz.After the fabrication of the proposed hybrid configurational star-shaped metamaterial by 3D printing technique,the transmission loss experiments are performed,and the experimental results indicate that the fabricated metamaterial has the characteristics of broadband vibration attenuation and an amplitude greater than 85%attenuation for the target frequency.These results demonstrate that the hybrid configurational star-shaped metamaterials can effectively widen the bandgap and realize high efficiency attenuation,which has capability for the vibration attenuation in the application of highprecise equipment.

Theoretical Study on Optical Properties of Oligofluorenes

We present theoretical investigations on structure-property correlations in fluorenone （FLO） and benzothiadiazole （BT） substituted oligofluorenes （OFLs） derived mainly from the chain morphology, thermal vibration and conjugated extent. Both the vertical absorptions and the vibrationally-resolved absorption and fluorescence spectra have been calculated by the com- bination of ab initio and time-dependent density functional theory. By properly taking into account of the anharmonic torsion potentials in the OFLs, we have reasonably reproduced the experimentally observed spectroscopic features. Both FLO and BT on-chain chemical defects acting as charge-trapping sites for singlet excitations, are responsible for long wave absorption and emission species, and thus alter the blue light-emitting properties of OFLs. As temperature decreases, the electronic spectral lineshapes of FLO-substituted oligomers become more structured. The lineshapes of BT-substituted oligomers are always smooth and featureless because of less low collective modes resonance. A more gentle excited poten-tial energy surface of BT-mixed molecules can enhance electronic delocalization and achieve bigger red shifts.

Synthesis and characterization of novel star-shaped pyridine cored compounds with alternating carbazole and triphenylamine moieties

Amorphous 2,4,6-trissubstituted pyridines containing three peripheral carbazole or two triphenylamine and one carbazole moieties, respectively, have been synthesized and characterized. The properties of the compounds are investigated by UV-vis absorption, photoluminescence spectroscopy, thermal analysis as well as cyclic voltammetry. The results show that the compounds have high thermal stability, emit blue light. Also, the compounds possess the HOMO and LUMO energy levels comparable to those of NPB. The effects of different substituents on the electronic properties of the materials have been discussed.

SYNTHESIS OF HETEROARM STAR-SHAPED POLYMER BY THE USE OF POLYFUNCTIONAL CHAIN-TRANSFER AGENT via CONVENTIONAL FREE RADICAL POLYMERIZATION

Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent,pentaerythritol tetrakis(3-mercaptopropinate).At appropriate monomer conversions,two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were o...

Fiber-based joint time and frequency dissemination via star-shaped commercial telecommunication network

A fiber-based, star-shaped joint time and frequency dissemination scheme is demonstrated. By working in cooperation with the existing commercial telecommunication network. Our scheme enables the frequency, time, and digital data networks to be integrated together and could represent an ideal option of interconnection among scientific institutions.The compensation functions of the time and frequency transfer scheme are set at the client nodes. The complexity of the central node is thus reduced, and future expansion by the addition of further branches will be accomplished more easily.During a performance test in which the ambient temperature fluctuation is 30℃/day, timing signal dissemination stability is achieved to be approximately ±50 ps along 25-km-long fiber spools. After calibration, a timing signal synchronization accuracy of 100 ps is also realized. The proposed scheme offers an option of the construction of large-scale fiber-based frequency and time transfer networks.

SYNTHESIS,CHARACTERIZATION AND NANOPARTICLE FORMATION OF STAR-SHAPED POLY(L-LACTIDE)WITH SIX ARMS

Well-defined star-shaped poly(L-lactide)with six arms(sPLLA)was synthesized via the ring-opening polymerization of L-lactide using dipentaerythritol as initiator and stannous octoate as catalyst in bulk at 125~C.The effects of molar ratios of both monomer to initiator and monomer to catalyst on the molecular weights of as-synthesized sPLLA polymers were in detail investigated.The molecular weights of sPLLA polymers linearly increased with the molar ratio of monomer to initiator,and the molecular weight dist...

pH-sensitive micelles self-assembled from star-shaped TPGS copolymers with ortho ester linkages for enhanced MDR reversal and chemotherapy

TPGS approved by FDA can be used as a P-gp inhibitor to effectively reverse multi-drug resistance(MDR)and as an anticancer agent for synergistic antitumor effects.However,the comparatively high critical micelle concentration(CMC),low drug loading(DL)and poor tumor target limit its further clinical application.To overcome these drawbacks,the pH-sensitive star-shaped TPGS copolymers were successfully constructed via using pentaerythritol as the initial materials,ortho esters as the pH-triggered linkages and TPGS active-ester as the terminated MDR material.The amphiphilic star-shaped TPGS copolymers could self-assemble into free and doxorubicin(DOX)-loaded micelles at neutral aqueous solutions.The micelles exhibited the lower CMC(8.2×10^(−5) mg/ml),higher DL(10.8%)and long-term storage and circulation stability,and showed enhanced cellular uptake,apoptosis,cytotoxicity,and growth inhibition for in vitro MCF-7/ADR and/or MCF-7/ADR multicellular spheroids and in vivo MCF-7/ADR tumors via efficiently targeted drug release at tumoral intracellular pH(5.0),MDR reversal of TPGS,and synergistic effect of DOX and TPGS.Therefore,the pH-sensitive micelles self-assembled from star-shaped TPGS copolymers with ortho ester linkages are potentially useful to clinically transform for enhanced MDR cancer treatment.

PREPARATION AND CHARACTERIZATION OF INCLUSION COMPLEXES OF TWO-ARM LINEAR AND FOUR-ARM STAR-SHAPED POLY(ε-CAPROLACTONE)S WITHα-CYCLODEXTRIN

Both four-ann star-shaped poly（ε-caprolactone） （4sPCL） and two-ann linear PCL （2LPCL） were synthesized and their inclusion complexation with α-cyclodextrin （α-CD） were studied. The inclusion complexes （ICs） formed between the PCL polymers and α-CD were characterized by ^1H-NMR, DSC, TGA, WAXD, and FT-1R, respectively. Both branch ann number and molecular weight of the PCL polymers have apparent effect on the stoichiometry （CL：CD, mol：mol） of these ICs. All these analytical results indicate that the branch arms of the PCL polymers are incorporated into the hydrophobic α-CD cavities and their original crystalline properties are completely suppressed. Moreover, the inclusion complexation between two-ann linear or four-ann star-shaped PCL polymers and α-CD not only enhances the thermal stability of the guest PCL polymers but also improves that of α-CD.

FIXED POINTS OF NONEXPANSIVE MAPPINGS ON STAR-SHAPED SUBSETS OF A CONVEX METRIC SPACE

In this paper, we give some characteristic properties of star-shaped sets which include a subset of a convex metric space. Using the characteristic properties, we discuss the existence problems of fixed points of nonexpansive type mappings on star-shaped subsets of convex metric spaces, which generalize the recent results obtained by Ding Xie-ping, Beg and Azam. Finally, we give an example which shows that our generalizations are essential.

Star-shaped Differentiable Functions and Star-shaped Differentials

Based on the isomorphism between the space of star-shaped sets and the space of continuous positively homogeneous real-valued functions, the star-shaped differential of a directionally differentiable function is defined. Formulas for star-shaped differential of a pointwise maximum and a pointwise minimum of a finite number of directionally differentiable functions, and a composite of two directionaUy differentiable functions are derived. Furthermore, the mean-value theorem for a directionaUy differentiable function is demonstrated.

Synthesis and Physicochemical Characterization of Biodegradable Star-Shaped Poly Lactide-Co-Glycolide-<i>β</i>-Cyclodextrin Copolymer Nanoparticles Containing Albumin

The purposes of this research were to synthesize and characterize star-shaped poly lactide-co-glycolide-β-cyclo-dextrin (PLGA-β-CD) copolymer by reacting L-lactide, glycolide and β-cyclodextrin in the presence of stannous octoate as a catalyst. The structure of PLGA-β-CD copolymer was confirmed with 1H-NMR, 13C-NMR and FT-IR spectra. Albumin as a model peptide drug was encapsulated within nanoparticles made of PLGA-β-CD with a modified double emulsion method. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) photomicrographs showed that the nanoparticles have the mean diameter within the range of 80 - 210 nm. Also they were almost spherical in shape. Effects of the experimental parameters, such as copolymer composition, copolymer concentration, and reaction temperature, on particular size and encapsulation efficiency were investigated.

Nondoped-type White Organic Light-Emitting Diode Using Star-Shaped Hexafluorenylbenzene as an Energy Transfer Layer

White organic light-emitting diodes （WOLEDs） with a structure of indium-tin-oxide （ITO）/N,N＇-bis- （1-naphthyl）-N,N＇-diphenyl- （1, 1＇-biphenyl）-4,4＇-diamine （NPB）/1,2,3,4,5,6-hexakis（9,9-diethyl-9H-fluoren-2- yl）benzene （HKEthFLYPh）/5,6,11,12-tetraphenylnaphtacene （rubrene）/tris（8-hydroxyquinoline） aluminum （Alq3）/Mg：Ag were fabricated by vacuum deposition method, in which a novel star-shaped hexafluorenyl- benzene HKEthFLYPh was used as an energy transfer layer, and an ultrathin layer of rubrene was inserted between HKEthFLYPh and Alq3 layers as a yellow light-emitting layer instead of using a time-consuming doping process. A fairly pure WOLED with Commissions Internationale De L＇Eclairage （CIE） coordinates of （0.32, 0.33） was obtained when the thickness of rubrene was 0.3 nm, and the spectrum was insensitive to the applied voltage. The device yielded a maximum luminance of 4816 cd/m2 at 18 V.

Distributed Region Tracking and Perimeter Surveillance for Second-Order Multi-Agent Systems in Star-Shaped Sets

This paper investigates region tracking and perimeter surveillance of second-order multiagent systems,where all agents move within a star-shaped set.First,by coordination transformations,the region tracking problem is converted from the star-shaped sets to a circular region.The authors employ communication and collaboration to complete region tracking and perimeter surveillance tasks,and then revert back to the star-shaped set by using inverse transformations.Second,the authors propose a distributed control strategy based on attractive and interaction potential functions,under which all agents can quickly track a given circular region and move around the perimeter.Finally,the authors validate the effectiveness and performance advantages of the proposed method through simulation experiments.

Synergistic Effect of Multi-Arm Architecture and Molecular Weight on Crystallization and Degradation Behavior of Star-Shaped Poly(Lactic Acid)

Star-shaped poly(lactic acid)s(PLAs)with two to five arms were synthesized by ring opening polymerization using tin(II)2-ethylhexanoate as catalyst and polyols as initiators.The effects of molecular weight together with multi-arm architecture on crystallization behavior,spherulite morphology and alkaline degradation behavior of star-shaped PLAs have been investigated.The results indicate that the multi-arm architecture interfered with spherulite growth,but promoted nucleation and alkaline degradation of star-shaped PLAs.Interestingly,with the increase of molecular weight(M_(n)),the crystallization rate first increased and then decreased,while the alkaline degradation rate was the opposite.The characteristic crystallization and alkaline degradation behavior of star-shaped PLAs were discussed based on the competition between segmental mobility and central core confinement.

Synthesis and optical properties research of gold nanoparticles with different morphologies

This paper presents an approach to synthesis of gold nanoparticles with different morphologies and investigation of the relationship between morphologies and their optical properties.Spherical gold nanoparticles with different sizes are synthesized via reduction method.Using seed-mediated solution growth method,gold nanoparticles with shuttle,star and stick shapes can be obtained.The sizes and morphologies of the gold nanoparticles are characterized by transmission electron microscopy （TEM）.The characterization results illustrate the growth process of the gold nanoparticles with different morphologies.Absorption spectroscopy and Raman spectroscopy measurements are performed to demonstrate the relationship between the morphologies and optical properties.The results of Raman characterization show that the gold nanoparticles with different morphologies can be used to probe molecules with different concentrations.

齐聚芴的合成、表征与发光性能研究

为寻求高效的蓝光材料,用改进的Sonogashira法合成了一系列含三键齐聚芴,所得产物均经过核磁、质谱及元素分析等方法鉴定.这些化合物室温下在溶液中及薄膜状态均发射蓝色荧光,其发射峰随聚合度增大依次红移,并以OF3R4为发光材料制作了电致发光器件,器件最大发光亮度达到5 812 cd/m2.

含长共轭取代基的丙烯酸酯的合成

文章通过在具有一定共轭链长的芴寡聚物的分子末段引入醇羟基,把长共轭结构的芴寡聚物作为取代基引入丙烯酸酯类单体。利用核磁共振确定了目标产物的分子结构,合成的单体具有强烈的紫外吸收和光致发光性质,而且由于在丙烯酸酯引入了芴寡聚物,产物可以用旋涂的方法在石英玻璃表面成膜,其在溶液中和固体薄膜最大发光位置分别是412 nm和442 nm。

单分散齐聚芴电致发光材料的合成及器件化

用Sonogash ira法合成了一系列含三键的齐聚芴,所有产物经核磁共振谱、质谱及元素分析表征确认.此类物质在溶液中及薄膜状态均发射出蓝紫或深蓝色荧光,荧光发射峰随聚合度增大依次红移.以这些物质为发光材料制作了相应的有机电致发光二极管(OLED),对器件的测试结果表明,所合成的齐聚芴具有优良的蓝色电致发光特性,其中OF3R4的最大发光亮度达到5 795 cd/m2,而OF3R6的最大外量子效率达到1.0%,其最大发光亮度为2 690 cd/m2.

用于氢键组装的星形光电材料的合成与表征

合成了一系列具有光电活性的星状共轭分子,并在端基上引入了不同个数或不同类型的氢键基团.包括端基上分别带有1,2和3个羧酸基团的星状芴分子,以及结构更为刚性的3个端基均为2,4-二胺基三嗪环的三聚茚分子,以此形成一个系列的分子结构,便于进行系统性研究.同时我们对这些星状分子进行了紫外和荧光光谱的表征,发现星状核和长烷基侧链能有效地阻止分子间π-π堆积和增大固态薄膜的无定形态.最终这些功能性分子将有望由氢键诱导在石墨或者金属表面形成有序的自组装结构.

SYNTHESIS AND CHARACTERIZATION OF BLUE LIGHT-EMITTING POLY(ARYL ETHER)S CONTAINING PYRIMIDINE-INCORPORATED OLIGOFLUORENE PENDANTS WITH BIPOLAR FEATURE

Novel blue light-emitting poly（aryl ether）s comprising of bipolar oligofluorene pendants as chromophores have been designed and synthesized, in which pyrimidine and arylamine moieties are utilized as the electron acceptor and electron donor, respectively. Through varying n bridge length from monofluorene to bifluorene and end-cappers from hydrogen to carbazole and diphenylamine, the emission color of the resulting polymers covers from deep blue to greenish blue, and their HOMO and LUMO levels can be modulated to facilitate charge injection to improve the device performance. Polymer light- emitting diodes （PLEDs） are fabricated with the device structure of ITO/poly（3,4-ethylenedioxythiophene）：poly（styrene sulfonic acid） （PEDOT：PSS） （50 nm）/polymer （80 nm）/Ca （10 nm）/Al （200 nm）. Among these polymers, P2Cz5F-Py with bifluorene bridge and carbazole end-capper shows excellent trade-off between the efficiency and emission wavelength, having a peak luminous efficiency as high as 1.26 cd/A and Commission Internationale de L＇Eclairage （CIE） coordinates of （0.17,0.17）.