Showing papers by "Sichuan University published in 1989"

An Improved Fourier Transform Profilometry

Abstract: An improved Fourier transform profilometry for the automatic mesurement of 3-D object shapes is presented. Because of using a defocused Rouchi grating to get a qusi-sinusoidal optical field and using grating π-phase shifting technique, the fundarmental spectrum modulated by 3-D object shapes can be extended from 0 to 2f. theorily Cf. is the carrier frequency of the optical field). Consequently,the measurable rate of hight variation can be extended three times more than the unimproved FTP. This article gives the theory and experiment results of the improved FTP.

Processing and Properties of Nanophase Oxides

Abstract: Nanophase oxides (Al2O3, MgO, ZnO and TiO2), with typical grain sizes in the range 2–20 nm, have been synthesized by the condensation of ultrafine particles in a convective inert gas followed by their collection and in-situ consolidation in vacuum at ambient temperature. These new materials, owing to the reduced scale of their grains along with the enhanced cleanliness of their grain boundaries, are found to have significantly improved properties relative to those of their coarser-grained, conventionally-prepared counterparts. Nanophase rutile (TiO2) with an initial mean grain diameter of 12 nm, for example, has been found to sinter at 400 to 600°C lower temperatures than conventional rutile powders, without the need for compacting or sintering aids, while retaining a small grain size. Additionally, the importance of the extremely clean surfaces obtained with the gas condensation method has been demonstrated by comparing the sintering behavior of powders with and without air exposure prior to consolidation. The research completed on the processing and properties of nanophase ceramics is reviewed, and the potential for engineering advanced ceramics using the nanophase processing method is discussed.

Some theorems in affine differential geometry

Abstract: In this paper we prove that an affine hypersphere with scalar curvature zero in a unimodular affine space of dimensionn+1 must be contained either in an elliptic paraboloid or in an affine image of the hypersurfacex1x2...xn+1=const. We prove also that an affine complete, affine maximal surface is an elliptic paraboloid if its affine normals omit 4 or more directions in general position.

Measurement applications based on pyroelectric properties of ferroelectric polymers

Abstract: Ferroelectric polymers such as polyvinylidene fluoride and vinylidene fluoride-based copolymers can be used in place of single crystals and ceramics in many devices. In addition, their availability as large-surface-area, low-cost, thin, flexible sheets creates many new possibilities. A review is presented of some of the applications of pyroelectric polymers in measurement devices. >

Topological degree theory and fixed point theorems in probabilistic metric spaces

Abstract: The Leray-Schauder topological degree theory is established in the probabilistic linear normed spaces. Based on this theory, some fixed point theorems for mappings in the probabilistic linear normed spaces are shown.

Use of caesium-137 measurements to investigate erosion and sediment sources within a small drainage basin in the loess plateau of China

Abstract: The contributions of sediment from different geomorpholigical units within a small basin in the Loess Plateau have been determined using caesium-137 as a tracer. The mean caesium-137 content of sediment originating from the hill area,where sheet and rill erosion are predominant,was 3-37 Bq kg-1,whereas no caesium-137 was detected in the sediment originating from the gully area where gullying and gravitational erosion are predominant. The mean caesium-137 content of sediment from two flood deposits was 0-23 Bq kg-1 and 0-89 Bq kg-1. The relative contribution from the hill area in the two floods was 7 per cent and 26 per cent,whilst that from the gully area was 93 per cent and 74 per cent.

Set-valued caristi’s fixed point theorem and ekelands variational principle

Abstract: This paper proposes a formally stronger set-valued Caristi's fixed point theorem and by using a simple method we give a direct proof for the equivalence between Ekeland's variational principle and this set-valued Caristi's fixed point theorem. The results stated in this paper improve and strengthen the corresponding results in [4].

Erratum: Theoretical calculations of the spin-lattice coupling coefficients G11 and G44 for MgO:Ni2+ crystals

Abstract: Calcul analytique des expressions des coefficients de couplage de reseaux de spins dans la symetrie cubique pour des ions d 8 , a partir d'une methode unifiee adaptee a tous les ions d n et aux formules de perturbations d'ordre eleve des eclatements d'ions d 8 en absence de champ dans les symetries tetragonale et trigonale. Selon ces expressions, les coefficients G 11 et G 44 pour MgO:Ni 2+ sont calcules a partir du modele de charge de point en utilisant seulement un parametre ajustable N(facteur de reduction de covalence moyen) obtenu a partir des spectres d'absorption optique. Les resultats sont en bon accord avec les decouvertes experimentales

Giemsa N-banding pattern in cabbage and Chinese kale

Abstract: In cabbage (Brassica oleracea var. capitata) and Chinese kale (B. oleracea alboglabra) four types of N-bands can be distinguished: pericentromeric, telomeric (terminal), intercalary and satellite bands. Typical NOR bands were not observed. The pericentromeric bands appear at the pericentric regions, possibly even at the centromeres of all chromosomes. Telomeric bands are observed on the short arms of chromosomes 1,5 and 6 in cabbage and chromosomes 1 and 5 in Chinese kale. Intercalary bands stained weakly in the long arms of chromosome 3 in cabbage and chromosome 2 in Chinese kale. Satellite bands cover the entire satellites in both Brassica species. The N-banding pattern is very similar in appearance to the C-banding pattern in both species and much more convenient to apply.

Variational calculations for metastable systems: Thermodynamic properties of glass transitions

Abstract: It is demonstrated, both theoretically and numerically, that the Gibbs–Bogoliubov (GB) thermodynamic variational calculation, developed originally for equilibrium systems, can be applied to a thermodynamic metastable system provided the structure of the reference system, used in this calculation, has the same main features as the metastable system under consideration. Following this, the GB thermodynamic variational calculation, employing the hard‐sphere system as the reference system, is used to quantitatively determine the thermodynamic features of the metallic glass transition. Good agreement with observation is obtained.

Differentiability of the semigroup associated with a structural damping model

Abstract: Let A be a positive definite, self-adjoint operator with the domain D(A) in a Hilbert space H and let B be A/sup alpha / (0 >

A modal theory and recursion RTCM algorithm for gratings of deep grooves and arbitrary profile

Abstract: A modal theory for gratings of deep grooves and arbitrary shape is developed. The theory is implemented with an algorithm of recursion reflection-transmission coefficient matrix (RTCM) . Several cases of plane wave with arbitrary polarization and arbitrary angle of incidence diffracted from gratings of deep grooves and arbitrary profile are calculated . It is found that this method is more accurate, more stable and faster than others.

Theoretical investigation of the spin-lattice coupling-coefficients g11 and g44 for cr3+ in cubic srtio3 crystals

Abstract: Etude theorique de ces coefficients a l'aide d'une methode uniforme convenable pour tous les ions d n et a l'aide de la formule de perturbation d'ordre eleve pour la decomposition des ions d 3 en symetries tetragonales et trigonales

Study on in vitro sperm capacitation and egg-penetration of giant panda.

Abstract: A preliminary report on in vitro sperm capacitation and egg-penetration of giant panda is briefly presented. The panda spermatozoon consists of head, neck and tail, just like the spermatozoa of other animals. Before capacitation sperm heads clustered together and dispersed after capacitation. They were then able to swim straight forward. During the time of in vitro capacitation the plasma membrane of the sperm head was first expanded to various degrees, then disintegrated, and finally became detached. The electro-dense material in the acrosome appeared in small clumps with high density. Extensive vesiculation occurred between the bi-layered acrosome membranes and thus led to disintegration. Vesiculation in panda sperm differs from that reported in hamsters. When the capacitated panda spermatozoa came into contact with the hamster eggs, the region between the acrosome collar and postacrosome cap first fused with the egg membrane followed by the penetration of the nucleus into the cortex of the egg. Some of the penetrating sperm nuclei became decondensed and some did not. The success of in vitro sperm capacitation and egg-penetration of giant panda is of great significance, suggesting that it is possible to carry out in vitro fertilization and embryo transplantation in this endangered species.

A Trial of Variational-Cumulant Expansion on Simple Ising Model With Second Order Phase Transition

Abstract: The standard variational-cumulant expansion (VC) combined with a scheme for the enumeration of connected diagrams is employed to study the simple Ising model with the second-order phase transition. This model is evaluated to the 5th order approximations. A comparison with the 2-dimensional exact results shows that thermodynamic quantities converge rather slowly to the exact values in the intermediate region. A strict analytical calculation of the critical temperature with the 5th order approximation both for and cumulant expansion suggests that VC can achieve rather high standard accuracy if the variational parameters could be determined up to higher degrees of corrections rather than the first one. Anomalies are found for and at extremely low temperature. A detailed study of implies that thermodynamic formulae should be carefully chosen in VC approach so as to avoid these anomalies.

Investigation of the Pressure and Stress Dependence of Low‐Temperature EPR Spectra for ZnSiF6 · 6H2O:V2+ Crystals

Abstract: sichuan univ,dept mat sci,chengdy,peoples r china.;zheng, wc (reprint author), acad sinica,int ctr mat phys,shenyang,peoples r china

On the LaSalle's invariant set for five-dimensional Lotka-Volterra prey-predator chain systems

Abstract: In this paper, we discussn-dimensional Lotka-Volterra prey-predator chain systems and prove that the locally, asymptotically stable equilibrium point of a five-dimensional system is a globally stable one. Namely, we prove that Chen Lansun's conjecture is true for the casen=5.

A Study of the Spin-Hamiltonian Parameters of Isoelectronic Impurity Ions in the Same Host Crystals

Abstract: sichuan univ,dept phys,chengdu,peoples r china.;zheng, wc (reprint author), acad sinica,int ctr mat phys,shenyang,peoples r china

Variational calculations of vibrational and vibration-rotational properties of ozone

Abstract: Vibrational and vibration-rotational energy levels of ozone and its isotopics substitutes have been calculated variationally by the ladder operator method. Thirty vibrational band origins and rotational energies of vibrational ground states for these molecules have been given. The good aggreement between the calculated results and the observed values shows that the calculation method is a promising one for variational studies of vibrational and vibration-rotational properties of nonlinear polyatomic molecules