The potential energy in materials is well approximated by pair functional which is composed of pair potentials and embedding energy. During calculating material potential energy, the orientational component and the vo...The potential energy in materials is well approximated by pair functional which is composed of pair potentials and embedding energy. During calculating material potential energy, the orientational component and the volumetric component are derived respectively from pair potentials and embedding energy. The sum of energy of all these two kinds of components is the material potential. No matter how microstructures change, damage or fracture, at the most level, they are all the changing and breaking atomic bonds. As an abstract of atomic bonds, these components change their stiffness during damaging. Material constitutive equations have been formulated by means of assembling all components' response functions. This material model is called the component assembling model. Theoretical analysis and numerical computing indicate that the proposed model has the capacity of reproducing some results satisfactorily, with the advantages of great conceptual simplicity, physical explicitness, and intrinsic induced anisotropy, etc.展开更多
Re-innervation of sensory and motor neurons on a defined area of the body wall was studied in two species of leeches, Whitmania pigra and Hirudo medicinalis, as a model of segmental animals. Following isolation and ro...Re-innervation of sensory and motor neurons on a defined area of the body wall was studied in two species of leeches, Whitmania pigra and Hirudo medicinalis, as a model of segmental animals. Following isolation and rotation of a tube of body wall, the mechanical sensory and annular erection (AE) motor neurons re-innervated the body wall, at a rate of approximately 3. 8 -8. 4 μm/h. The patterns of re-innerva-tion by pairs of neurons on each side of a ganglion were bilaterally symmetric. The repairs are synchronous for the sensory and motor neurons which are of different functions but in a same ganglion. The gap junctions are widely spread in leech between neurons and glia cells, as well as among the neurons and glia cells themselves. Therefore, it is proposed that the nervous system repair is regulated by a low-resistance pathway. In the xenotransplantation experiments, neurons recognized target tissues before the immuno-recognition and rejection.展开更多
Research advances of un-symmetric constitutive equation of anisotropic fluid,influence of un-symmetric stress tensor on material functions,vibrational shear flow of the fluid with small amplitudes and rheology of anis...Research advances of un-symmetric constitutive equation of anisotropic fluid,influence of un-symmetric stress tensor on material functions,vibrational shear flow of the fluid with small amplitudes and rheology of anisotropic suspension were reported.A new concept of simple anisotropic fluid was introduced.On the basis of anisotropic principle,the simple fluid stress behaviour was described by velocity gradient tensor F and spin tensor W instead of velocity gradient tensor D in the classic Leslie-Ericksen continuum theory.Two relaxation times analyzing rheological nature of the fluid and using tensor analysis a general form of the constitutive equation of co-rotational type was introduced.More general model LCP-H for the fluid was developed.The unsymmetry of the shear stress was predicted by the present continuum theory for anisotropic viscoelastic fluid-LC polymer liquids.The influence of the relaxation times on material functions was specially studied.It is important to study the unsteady vibrational rotating flow with small amplitudes,as it is a best way to obtain knowledge of elasticity of the LC polymer,i.e.dynamic viscoelasticity.For the shear-unsymmetric stresses,two shear stresses were obtained thus two complex viscosities and two complex shear modulus(i.e.first and second one) were introduced by the constitutive equation which was defined by rotating shear rate introduced by author.For the two stability problems of fluid,such as stability of hydrodynamic flow and orientational motion,were discussed.The results show that the polymer suspension systems exhibit anisotropic character.The PNC systems can exhibit significant shear-thinning effects.For more concentrated polymer nano-suspensions,the first normal stress difference change from positive to negative,which is similar to LC polymer behavior.展开更多
In this study, liquid crystal（LC） was used to study the interactions of alkyl polyglycosides（APG） with gelatin and bovine serum albumin（BSA） at the LC-aqueous interface. The LC easily undergo an orientational tr...In this study, liquid crystal（LC） was used to study the interactions of alkyl polyglycosides（APG） with gelatin and bovine serum albumin（BSA） at the LC-aqueous interface. The LC easily undergo an orientational transition from a homeotropic to a planar state after proteins were in contact to the LCaqueous interface decorated with APG, thus inducing an optical change from dark to bright. The optical image analysis reveals that the rearrangement rate of APG monolayer is tightly dependent on the concentration and chemical structure of the protein of interest. For example, the rearrangement rate of APG monolayer increases with an increasing gelatin concentration. We also find that the chemical structure of the proteins has a significant impact on the difference in the growth behavior of bright domains in LC.展开更多
The orientational order of two liquid crystals , namely, 6 [4 (4 nitrophenylazo)phenyloxy] hexyl diethanolamines(C6) and 10 1 bromo[4 (nitrophenylazo)phenyloxy] alkane(B10) was studied by means of 2H...The orientational order of two liquid crystals , namely, 6 [4 (4 nitrophenylazo)phenyloxy] hexyl diethanolamines(C6) and 10 1 bromo[4 (nitrophenylazo)phenyloxy] alkane(B10) was studied by means of 2H NMR spectroscopy with hexamethylbenzene d 18 as the probe molecule. The results show that the directors in the smectic A phase of C6 and the nematic phase of B10 could be aligned, which was parallel to the magnetic field. The orientational order parameter of the solute molecules in C6 was about 0.2, while it is only 0.1 in B10, which is expected because the more ordered smectic phase tends to align solute molecules to a high level. Compared to the orientational order parameter of the solute in the SmC phase of 4[3,4,5 tris(4 dodecyloxybenzyloxy) benzoyloxy] 4 (4′ dodecyloxybenzoyloxy)biphenyl (Ⅰ) ( P 2=0.14 ), it is larger in SmA phase of C6. The relatively higher orientational order parameter of the solute in C6 is attributed to the formation of intermolecular H bonds in the SmA phase of C6.展开更多
The epitaxial relationships of lattices and crystalline qualities of LSMO/ZnO/sapphire double-hetero systems were thoroughly analyzed using X-ray diffraction techniques with a modern high resolution XRD system. It was...The epitaxial relationships of lattices and crystalline qualities of LSMO/ZnO/sapphire double-hetero systems were thoroughly analyzed using X-ray diffraction techniques with a modern high resolution XRD system. It was revealed that the epitaxial growth of the LSMO (110) phase was promoted under higher temperature accompanying the suppression of other competitive growth of the LSMO (001) and (111) phases. Supplying the plasma oxygen accelerated the suppression of the LSMO (111) phase. The complex epitaxial orientational relationships in these three growth modes were revealed from the precise analyses with the high resolution out-of-plane XRD and the in-plane XRD measurements, pole figure measurements, and reciprocal space mappings measurements, as [112ˉ](111)LSMO//[11ˉ00](0001)ZnO//[112ˉ0](0001)Sap, [110ˉ](111LSMO)//[11ˉ00](0001)Zno//[112ˉ0](0001)Sap, and [110](001)LSMO//[11ˉ00](0001)Zno//[112ˉ0](0001)Sap. The validity of this model for the epitaxial orientational relationships in LSMO/ZnO/sapphire double heteroepitaxial layers was confirmed identically with the data ana- lyses of the out-of-plane wide-range Reciprocal Space Mapping using the 2-dimensional X-ray detector.展开更多
The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method...The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method of bond order parameters. The result shows that both Ca++ and F- sublattices can be described with the bond-orientation normal distribution model. In the superionic phase the Ca++ cations keep their original stable fcc frame, but in the F- case random distortion generates from their original simple cubic (sc) structure. The simulation on the molten phase gives three radial distribution functions that are difficult to separate from the experimental X-ray diffraction data. The simulation of quenched-amorphous state shows that a dense random packing of equivalent spheres centered by Ca++ cations occurs in the system simulated. However, the system quenched is not stable enough because the Ca++ cation and F- anions around it do not form themselves into a certain configuration.展开更多
As a part of our systematic study of the physical properties of the compounds of symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4’-oxy) alkanes (m.OnO.m), we report here an ...As a part of our systematic study of the physical properties of the compounds of symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4’-oxy) alkanes (m.OnO.m), we report here an optical study of two nematogenic compounds of this series viz., 6.O12O.6 and 7.O12O.7 by carrying out the measurement of extraordinary and ordinary refractive indices using modified spectrometer. The molecular polarizability anisotropies are evaluated using Lippincott δ-function model, the molecular vibration method, Haller’s extrapolation method and scaling factor method. The molecular polrizabilities, αe and αo are calculated using Vuks’ isotropic field model and Neugebauer’s anisotropic field model. The orientational order parameter, S, is estimated by using the molecular polarizability values calculated from refractive index and denstity data as well as polarizability anisotropy values calculated as a function of temperature in the nematic phase of both of the dimers. These values are discussed with reference to the order parameter values obtained directly from the optical birefringence, Δn, data without assuming any internal field. A comparison of the order parameter values from all of these methods was carried out in the light of available literature data.展开更多
The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting...The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting on the swelling, elongation and crosslinking density was observed. The orientational order arising from the correlation between chain segments decreases with the increase of the numbers of both links between junctions and solvent molecules around segments.展开更多
MgO nanosheets with exposed（111） facets were obtained through the preparation of Mg（OH）2 precursor by a hydrothermal method in the presence of oleylamine and subsequent calcination in air. The different preferred ...MgO nanosheets with exposed（111） facets were obtained through the preparation of Mg（OH）2 precursor by a hydrothermal method in the presence of oleylamine and subsequent calcination in air. The different preferred orientational assemblies of Mg O nanosheets, achieved by adjusting the polarity of dispersing solvents（ethanol and cyclohexane） during the sample preparation, show different structural and spectral features.展开更多
We have analyzed the photorefractive（PR） effect of a polymer composite was reported which combines a novel bi-functional poly（N-vinyl）-3-[p-nitrophenylazo]carbazolyl（PVNPAK） and 2,4,7-trinitro-9-fluorenone（TNF...We have analyzed the photorefractive（PR） effect of a polymer composite was reported which combines a novel bi-functional poly（N-vinyl）-3-[p-nitrophenylazo]carbazolyl（PVNPAK） and 2,4,7-trinitro-9-fluorenone（TNF）. PVNPAK was synthesized by a post-azo-coupling reaction, with an azo derivative as the electrooptic chromophore and carbazolyl as photoconductive moiety. The asymmetric two-beam coupling gain of 13.9 cm-1 and diffraction efficiency of 1.2% for poled polymer film fabricated using a corona poling are obtained at the wavelength of 647.1 nm, confirming photorefractivity. We interpreted this result as the orientational enhancement, in which the spatial charge field may enhance the modulated orientation of the azobenzen chromophore. It is unexpected that the photorefractive gain of 9.5 cm-1 for the unpoled polymer film also was observed without external field in two-beam coupling（TBC） experiment. This phenomenon is attributed to a light-induced orientational grating when the azobenzene groups are illuminated by polarized light.展开更多
The accurate estimation of the end-effector’s pose in large operating spaces is the key for the mobile manipulator to realize efficient manufacturing of large and complex components.We propose a novel pose tracking m...The accurate estimation of the end-effector’s pose in large operating spaces is the key for the mobile manipulator to realize efficient manufacturing of large and complex components.We propose a novel pose tracking method in large-range using visual fiducial markers,and further propose the layout optimization method for the encoded fiducial markers.A metric named orientational dilution of precision(ODOP)is proposed to evaluate the magnification of the pose estimation error compared with the measurement error of the coded fiducial markers.The distribution pattern of the coded markers is analyzed based on ODOP,and the square-shaped layout is determined to be a satisfactory distribution pattern for the minimum positioning unit of markers,and the side length of the square-shaped layout is further selected.The simulations and experiments prove the effectiveness of the ODOP index.Finally,the square-shaped layout and the designed distribution density for positioning coded markers are adopted to realize the high-precision measurement of large components by the mobile manipulator.展开更多
Dielectric polymers are the materials of choice for high energy density film capacitors.The increasing demand for advanced electrical systems requires dielectric polymers to operate efficiently under extreme condition...Dielectric polymers are the materials of choice for high energy density film capacitors.The increasing demand for advanced electrical systems requires dielectric polymers to operate efficiently under extreme conditions,especially at elevated temperatures.However,the low permittivity and relatively low operating temperature of dielectric polymers limit the high-temperature capacitive energy storage applications.Fortunately,dipolar glass polymers are demonstrated as the preferred materials to achieve high dielectric constant,low dielectric loss and high energy density at elevated temperatures.In this review,we critically elaborate on the recent progress of dipolar glass polymers based on orientational polarization from molecular engineering.In addition,the general design considerations and various dipole moment entities of dipolar glass polymers are described in detail.High dipolar moment,high dipole density and rotation freedom of dipoles are essential for dipolar glass polymers to gain superior dielectric and energy storage properties.Challenges and future opportunities for dipolar glass polymers towards high-temperature energy storage applications are also provided.展开更多
Single nanoparticle tracking(SPT)is a unique and powerful tool to investigate the interaction between nanoparticles and cells,which is of considerable importance for nanotechnology applications in biomedical fields an...Single nanoparticle tracking(SPT)is a unique and powerful tool to investigate the interaction between nanoparticles and cells,which is of considerable importance for nanotechnology applications in biomedical fields and in-depth understanding of biological activities.However,previous work typically focused on translations of single nanoparticles while they undergo both translational and rotational motions.In this study,we obtained both the translational and rotational dynamics of single gold nanorods during their cellular internalization process using dual-channel polarization microscopy.In particular,the azimuth and polar angles were integrated into a polar coordinate systemto obtain three general orientation distribution patterns,found to have a close relationship with the nanoparticle cellular internalization process and time-dependent alterations.Moreover,the patterns accompanied by trajectories,translational and rotational coefficients,the azimuth and polar angles,and other parameters provided a wealth of knowledge on the nanoparticle cellular internalization dynamics with unprecedented details.We observed that the gold nanorods could initially assume a tip-first quick rotation state with partially restricted orientations,then change to a strongly confined near-vertical insertion state with slight angular fluctuations,and eventually transform into a random and fast rotation state.Our methodology opens up a new avenue for a detailed understanding of biological processes.展开更多
Here, we report on hierarchical mechanical behavior of 500-nm-thick Conanocrystal 3D superlattices （supracrystals） induced by either the crystalline structure （nanocrystallinity） or the length of the coating agent...Here, we report on hierarchical mechanical behavior of 500-nm-thick Conanocrystal 3D superlattices （supracrystals） induced by either the crystalline structure （nanocrystallinity） or the length of the coating agent of Co nanocrystals. Increasing the nanocrystal shape anisotropy of Co nanocrystals through the control of their nanocrystallinities induces a higher level of ordering with both translational and orientational alignment of nanocrystals within the supracrystals. The hierarchy in ordering at various scales, i.e., from the atomic lattice within the nanocrystals to the nanocrystal superlattices within supracrystals, is correlated with marked changes in the Young＇s modulus of supracrystals： From 0.7 ±0.4 to 1.7 ±0.5 and to 6.6 ±1.5 GPa as the crystalline structure of Co nanoparticles changes from amorphous-Co to ε-Co and to hexagonal compact packing （hcp）-Co, respectively. Moreover, for supracrystals of 7 nm amorphous Co nanoparticles, the Young＇s modulus decreases by one order of magnitude from 0.7 ±0.4 to 0.08 ±0.03 GPa upon reducing the alkyl chain length of the ligands coating the Co nanoparticles from C18 （oleic acid） to C12 （lauric acid）. The hierarchical mechanical behavior is rationalized using a dimensional model of the stress-strain relationship in supracrystals.展开更多
This paper identifies metaphors in newspaper English, specifically the articles in China Daily, as the research object. Many linguists have studies metaphors in newspaper English, but research perspective is only limi...This paper identifies metaphors in newspaper English, specifically the articles in China Daily, as the research object. Many linguists have studies metaphors in newspaper English, but research perspective is only limited to the classification of metaphor, and not analyses the trends for each type of metaphor from the diachronic approach, therefore, this paper aims to make up for this deficiency. Thirty-six articles are randomly sampled from China Daily in the year of 2010, to make up a small corpus. Then the occurrence frequency of every kind of metaphor of recent years in this corpus is analyzed. Finally, it is found that the occurrence frequency of orientational metaphors shows a decreasing tendency, while those of the ontological and structural metaphors are relatively stable. We have found two reasons for this trend appears. Firstly, orientational metaphors are used less frequently, because they often appear when it comes to the description of numbers, and digital change itself has a lot of direct expression Secondly, structural metaphor and ontological metaphor are relatively stable, because the former helps the readers to understand the new things; the latter can expressed lively展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos.10572140 and 10232050)the Ministry of Science and Technology Foundation (Grant No.2002CB412706) are short of physical basics, and which is particularly evident in anisotropic damage theories.
文摘The potential energy in materials is well approximated by pair functional which is composed of pair potentials and embedding energy. During calculating material potential energy, the orientational component and the volumetric component are derived respectively from pair potentials and embedding energy. The sum of energy of all these two kinds of components is the material potential. No matter how microstructures change, damage or fracture, at the most level, they are all the changing and breaking atomic bonds. As an abstract of atomic bonds, these components change their stiffness during damaging. Material constitutive equations have been formulated by means of assembling all components' response functions. This material model is called the component assembling model. Theoretical analysis and numerical computing indicate that the proposed model has the capacity of reproducing some results satisfactorily, with the advantages of great conceptual simplicity, physical explicitness, and intrinsic induced anisotropy, etc.
基金supported by the National Key R&D Program of China(2020YFB1505802)the Ministry of Science and Technology(2017YFA0208200)+2 种基金the National Natural Science Foundation of China(22025108,U21A20327,and 22121001)Guangdong Provincial Natural Science Fund for Distinguished Young Scholars(2021B1515020081)the start-up support from Xiamen University and Guangzhou Key Laboratory of Low-Dimensional Materials and Energy Storage Devices(20195010002)。
基金Supported by the State Commission of Science and Technology, the National Natural Science Foundation and the State Education Commission of China.
文摘Re-innervation of sensory and motor neurons on a defined area of the body wall was studied in two species of leeches, Whitmania pigra and Hirudo medicinalis, as a model of segmental animals. Following isolation and rotation of a tube of body wall, the mechanical sensory and annular erection (AE) motor neurons re-innervated the body wall, at a rate of approximately 3. 8 -8. 4 μm/h. The patterns of re-innerva-tion by pairs of neurons on each side of a ganglion were bilaterally symmetric. The repairs are synchronous for the sensory and motor neurons which are of different functions but in a same ganglion. The gap junctions are widely spread in leech between neurons and glia cells, as well as among the neurons and glia cells themselves. Therefore, it is proposed that the nervous system repair is regulated by a low-resistance pathway. In the xenotransplantation experiments, neurons recognized target tissues before the immuno-recognition and rejection.
基金Project(10772177) supported by the National Natural Science Foundation of China
文摘Research advances of un-symmetric constitutive equation of anisotropic fluid,influence of un-symmetric stress tensor on material functions,vibrational shear flow of the fluid with small amplitudes and rheology of anisotropic suspension were reported.A new concept of simple anisotropic fluid was introduced.On the basis of anisotropic principle,the simple fluid stress behaviour was described by velocity gradient tensor F and spin tensor W instead of velocity gradient tensor D in the classic Leslie-Ericksen continuum theory.Two relaxation times analyzing rheological nature of the fluid and using tensor analysis a general form of the constitutive equation of co-rotational type was introduced.More general model LCP-H for the fluid was developed.The unsymmetry of the shear stress was predicted by the present continuum theory for anisotropic viscoelastic fluid-LC polymer liquids.The influence of the relaxation times on material functions was specially studied.It is important to study the unsteady vibrational rotating flow with small amplitudes,as it is a best way to obtain knowledge of elasticity of the LC polymer,i.e.dynamic viscoelasticity.For the shear-unsymmetric stresses,two shear stresses were obtained thus two complex viscosities and two complex shear modulus(i.e.first and second one) were introduced by the constitutive equation which was defined by rotating shear rate introduced by author.For the two stability problems of fluid,such as stability of hydrodynamic flow and orientational motion,were discussed.The results show that the polymer suspension systems exhibit anisotropic character.The PNC systems can exhibit significant shear-thinning effects.For more concentrated polymer nano-suspensions,the first normal stress difference change from positive to negative,which is similar to LC polymer behavior.
基金supported by the National Natural Science Foundation of China (Nos. 51273220, 50903011)the Project of Postgraduate Degree Construction, Southwest University for Nationalities (No. 2015XWD-S0703)
文摘In this study, liquid crystal（LC） was used to study the interactions of alkyl polyglycosides（APG） with gelatin and bovine serum albumin（BSA） at the LC-aqueous interface. The LC easily undergo an orientational transition from a homeotropic to a planar state after proteins were in contact to the LCaqueous interface decorated with APG, thus inducing an optical change from dark to bright. The optical image analysis reveals that the rearrangement rate of APG monolayer is tightly dependent on the concentration and chemical structure of the protein of interest. For example, the rearrangement rate of APG monolayer increases with an increasing gelatin concentration. We also find that the chemical structure of the proteins has a significant impact on the difference in the growth behavior of bright domains in LC.
文摘The orientational order of two liquid crystals , namely, 6 [4 (4 nitrophenylazo)phenyloxy] hexyl diethanolamines(C6) and 10 1 bromo[4 (nitrophenylazo)phenyloxy] alkane(B10) was studied by means of 2H NMR spectroscopy with hexamethylbenzene d 18 as the probe molecule. The results show that the directors in the smectic A phase of C6 and the nematic phase of B10 could be aligned, which was parallel to the magnetic field. The orientational order parameter of the solute molecules in C6 was about 0.2, while it is only 0.1 in B10, which is expected because the more ordered smectic phase tends to align solute molecules to a high level. Compared to the orientational order parameter of the solute in the SmC phase of 4[3,4,5 tris(4 dodecyloxybenzyloxy) benzoyloxy] 4 (4′ dodecyloxybenzoyloxy)biphenyl (Ⅰ) ( P 2=0.14 ), it is larger in SmA phase of C6. The relatively higher orientational order parameter of the solute in C6 is attributed to the formation of intermolecular H bonds in the SmA phase of C6.
文摘The epitaxial relationships of lattices and crystalline qualities of LSMO/ZnO/sapphire double-hetero systems were thoroughly analyzed using X-ray diffraction techniques with a modern high resolution XRD system. It was revealed that the epitaxial growth of the LSMO (110) phase was promoted under higher temperature accompanying the suppression of other competitive growth of the LSMO (001) and (111) phases. Supplying the plasma oxygen accelerated the suppression of the LSMO (111) phase. The complex epitaxial orientational relationships in these three growth modes were revealed from the precise analyses with the high resolution out-of-plane XRD and the in-plane XRD measurements, pole figure measurements, and reciprocal space mappings measurements, as [112ˉ](111)LSMO//[11ˉ00](0001)ZnO//[112ˉ0](0001)Sap, [110ˉ](111LSMO)//[11ˉ00](0001)Zno//[112ˉ0](0001)Sap, and [110](001)LSMO//[11ˉ00](0001)Zno//[112ˉ0](0001)Sap. The validity of this model for the epitaxial orientational relationships in LSMO/ZnO/sapphire double heteroepitaxial layers was confirmed identically with the data ana- lyses of the out-of-plane wide-range Reciprocal Space Mapping using the 2-dimensional X-ray detector.
基金Project supported by the National Natural Science Foundation of China.
文摘The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method of bond order parameters. The result shows that both Ca++ and F- sublattices can be described with the bond-orientation normal distribution model. In the superionic phase the Ca++ cations keep their original stable fcc frame, but in the F- case random distortion generates from their original simple cubic (sc) structure. The simulation on the molten phase gives three radial distribution functions that are difficult to separate from the experimental X-ray diffraction data. The simulation of quenched-amorphous state shows that a dense random packing of equivalent spheres centered by Ca++ cations occurs in the system simulated. However, the system quenched is not stable enough because the Ca++ cation and F- anions around it do not form themselves into a certain configuration.
文摘As a part of our systematic study of the physical properties of the compounds of symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4’-oxy) alkanes (m.OnO.m), we report here an optical study of two nematogenic compounds of this series viz., 6.O12O.6 and 7.O12O.7 by carrying out the measurement of extraordinary and ordinary refractive indices using modified spectrometer. The molecular polarizability anisotropies are evaluated using Lippincott δ-function model, the molecular vibration method, Haller’s extrapolation method and scaling factor method. The molecular polrizabilities, αe and αo are calculated using Vuks’ isotropic field model and Neugebauer’s anisotropic field model. The orientational order parameter, S, is estimated by using the molecular polarizability values calculated from refractive index and denstity data as well as polarizability anisotropy values calculated as a function of temperature in the nematic phase of both of the dimers. These values are discussed with reference to the order parameter values obtained directly from the optical birefringence, Δn, data without assuming any internal field. A comparison of the order parameter values from all of these methods was carried out in the light of available literature data.
基金Supported by the National Natural Science Foundation of China
文摘The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting on the swelling, elongation and crosslinking density was observed. The orientational order arising from the correlation between chain segments decreases with the increase of the numbers of both links between junctions and solvent molecules around segments.
基金supported by the National Natural Science Foundation of China (Nos. 21673046, 21473036, 21371035, 91645201)
文摘MgO nanosheets with exposed（111） facets were obtained through the preparation of Mg（OH）2 precursor by a hydrothermal method in the presence of oleylamine and subsequent calcination in air. The different preferred orientational assemblies of Mg O nanosheets, achieved by adjusting the polarity of dispersing solvents（ethanol and cyclohexane） during the sample preparation, show different structural and spectral features.
基金Funded by the National Natural Science Foundation of China(No.51303115)
文摘We have analyzed the photorefractive（PR） effect of a polymer composite was reported which combines a novel bi-functional poly（N-vinyl）-3-[p-nitrophenylazo]carbazolyl（PVNPAK） and 2,4,7-trinitro-9-fluorenone（TNF）. PVNPAK was synthesized by a post-azo-coupling reaction, with an azo derivative as the electrooptic chromophore and carbazolyl as photoconductive moiety. The asymmetric two-beam coupling gain of 13.9 cm-1 and diffraction efficiency of 1.2% for poled polymer film fabricated using a corona poling are obtained at the wavelength of 647.1 nm, confirming photorefractivity. We interpreted this result as the orientational enhancement, in which the spatial charge field may enhance the modulated orientation of the azobenzen chromophore. It is unexpected that the photorefractive gain of 9.5 cm-1 for the unpoled polymer film also was observed without external field in two-beam coupling（TBC） experiment. This phenomenon is attributed to a light-induced orientational grating when the azobenzene groups are illuminated by polarized light.
基金supported in part by the National Key Research and Development Program of China(Grant No.2017YFB1301504)the National Natural Science Foundation of China(Grant Nos.91748204,91948301 and 51905183)the China Postdoctoral Science Foundation(Grant No.2018M642820).
文摘The accurate estimation of the end-effector’s pose in large operating spaces is the key for the mobile manipulator to realize efficient manufacturing of large and complex components.We propose a novel pose tracking method in large-range using visual fiducial markers,and further propose the layout optimization method for the encoded fiducial markers.A metric named orientational dilution of precision(ODOP)is proposed to evaluate the magnification of the pose estimation error compared with the measurement error of the coded fiducial markers.The distribution pattern of the coded markers is analyzed based on ODOP,and the square-shaped layout is determined to be a satisfactory distribution pattern for the minimum positioning unit of markers,and the side length of the square-shaped layout is further selected.The simulations and experiments prove the effectiveness of the ODOP index.Finally,the square-shaped layout and the designed distribution density for positioning coded markers are adopted to realize the high-precision measurement of large components by the mobile manipulator.
基金financially supported by the National Natural Science Foundation of China(Nos.51973080,92066104 and 51903100)。
文摘Dielectric polymers are the materials of choice for high energy density film capacitors.The increasing demand for advanced electrical systems requires dielectric polymers to operate efficiently under extreme conditions,especially at elevated temperatures.However,the low permittivity and relatively low operating temperature of dielectric polymers limit the high-temperature capacitive energy storage applications.Fortunately,dipolar glass polymers are demonstrated as the preferred materials to achieve high dielectric constant,low dielectric loss and high energy density at elevated temperatures.In this review,we critically elaborate on the recent progress of dipolar glass polymers based on orientational polarization from molecular engineering.In addition,the general design considerations and various dipole moment entities of dipolar glass polymers are described in detail.High dipolar moment,high dipole density and rotation freedom of dipoles are essential for dipolar glass polymers to gain superior dielectric and energy storage properties.Challenges and future opportunities for dipolar glass polymers towards high-temperature energy storage applications are also provided.
基金supported by the National Natural Science Foundation of China(grant nos.21127009,21221003,and 21425519)the Training Program for Excellent Young Innovators of Changsha(grant no.kq1905061)the Natural Science Foundation of Hunan Province,China(grant no.020RC3042).
文摘Single nanoparticle tracking(SPT)is a unique and powerful tool to investigate the interaction between nanoparticles and cells,which is of considerable importance for nanotechnology applications in biomedical fields and in-depth understanding of biological activities.However,previous work typically focused on translations of single nanoparticles while they undergo both translational and rotational motions.In this study,we obtained both the translational and rotational dynamics of single gold nanorods during their cellular internalization process using dual-channel polarization microscopy.In particular,the azimuth and polar angles were integrated into a polar coordinate systemto obtain three general orientation distribution patterns,found to have a close relationship with the nanoparticle cellular internalization process and time-dependent alterations.Moreover,the patterns accompanied by trajectories,translational and rotational coefficients,the azimuth and polar angles,and other parameters provided a wealth of knowledge on the nanoparticle cellular internalization dynamics with unprecedented details.We observed that the gold nanorods could initially assume a tip-first quick rotation state with partially restricted orientations,then change to a strongly confined near-vertical insertion state with slight angular fluctuations,and eventually transform into a random and fast rotation state.Our methodology opens up a new avenue for a detailed understanding of biological processes.
文摘Here, we report on hierarchical mechanical behavior of 500-nm-thick Conanocrystal 3D superlattices （supracrystals） induced by either the crystalline structure （nanocrystallinity） or the length of the coating agent of Co nanocrystals. Increasing the nanocrystal shape anisotropy of Co nanocrystals through the control of their nanocrystallinities induces a higher level of ordering with both translational and orientational alignment of nanocrystals within the supracrystals. The hierarchy in ordering at various scales, i.e., from the atomic lattice within the nanocrystals to the nanocrystal superlattices within supracrystals, is correlated with marked changes in the Young＇s modulus of supracrystals： From 0.7 ±0.4 to 1.7 ±0.5 and to 6.6 ±1.5 GPa as the crystalline structure of Co nanoparticles changes from amorphous-Co to ε-Co and to hexagonal compact packing （hcp）-Co, respectively. Moreover, for supracrystals of 7 nm amorphous Co nanoparticles, the Young＇s modulus decreases by one order of magnitude from 0.7 ±0.4 to 0.08 ±0.03 GPa upon reducing the alkyl chain length of the ligands coating the Co nanoparticles from C18 （oleic acid） to C12 （lauric acid）. The hierarchical mechanical behavior is rationalized using a dimensional model of the stress-strain relationship in supracrystals.
文摘This paper identifies metaphors in newspaper English, specifically the articles in China Daily, as the research object. Many linguists have studies metaphors in newspaper English, but research perspective is only limited to the classification of metaphor, and not analyses the trends for each type of metaphor from the diachronic approach, therefore, this paper aims to make up for this deficiency. Thirty-six articles are randomly sampled from China Daily in the year of 2010, to make up a small corpus. Then the occurrence frequency of every kind of metaphor of recent years in this corpus is analyzed. Finally, it is found that the occurrence frequency of orientational metaphors shows a decreasing tendency, while those of the ontological and structural metaphors are relatively stable. We have found two reasons for this trend appears. Firstly, orientational metaphors are used less frequently, because they often appear when it comes to the description of numbers, and digital change itself has a lot of direct expression Secondly, structural metaphor and ontological metaphor are relatively stable, because the former helps the readers to understand the new things; the latter can expressed lively
