Constraints on heterotic M-theory from s-cobordism

We interpret heterotic M-theory in terms of h-cobordism, that is the eleven-manifold is a product of the ten-manifold times an interval is translated into a statement that the former is a cobordism of the latter which is a homotopy equivalence. In the non-simply connected case, which is important for model building, the interpretation is then in terms of s-cobordism, so that the cobordism is a simple-homotopy equivalence. This gives constraints on the possible cobordisms depending on the fundamental groups and hence provides a characterization of possible compactification manifolds using the Whitehead group - a quotient of algebraic K-theory of the integral group ring of the fundamental group - and a distinguished element, the Whitehead torsion. We also consider the effect on the dynamics via diffeomorphisms and general dimensional reduction, and comment on the effect on F-theory compactifications.     

CPT-Frames for Non-Hermitian Hamiltonians

Based on the P T-symmetric quantum theory,the concepts of P T-frame,P T-symmetric operator and CPT-frame on a Hilbert space K and for an operator on K are proposed.It is proved that the spectrum and point spectrum of a P T-symmetric linear operator are both symmetric with respect to the real axis and the eigenvalues of an unbroken P T-symmetric operator are real.For a linear operator H on Cd,it is proved that H has unbroken P Tsymmetry if and only if it has d diferent eigenvalues and the corresponding eigenstates are eigenstates of P T.Given a C P T-frame on K,a new positive inner product on K is induced and called C P T-inner product.Te relationship between the CP T-adjoint and the Dirac adjoint of a densely defined linear operator is derived,and it is proved that an operator which has a bounded CP T-frame is CP T-Hermitian if and only if it is T-symmetric,in that case,it is similar to a Hermitian operator.The existence of an operator C consisting of a CP T-frame is discussed.These concepts and results will serve a mathematical discussion about P T-symmetric quantum mechanics.     

CPT-Frames for Non-Hermitian Hamiltonians

Based on the PT-symmetric quantum theory, the concepts of PT-frame, PT-symmetric operator and CPT-frame on a Hilbert space K and for an operator on K are proposed. It is proved that the spectrum and point spectrum of a PT-symmetric linear operator are both symmetric with respect to the real axis and the eigenvalues of an unbroken PT-symmetric operator are real. For a linear operator H on C^d, it is proved that H has unbroken PT- symmetry if and only if it has d different eigenvalues and the corresponding eigenstates are eigenstates of PT. Given a CPT-frame on K, a new positive inner product on K is induced and called CPT-inner product. Te relationship between the CPT-adjoint and the Dirac adjoint of a densely defined linear operator is derived, and it is proved that an operator which has a bounded CPT-frame is CPT-Hermitian if and only if it is T-symmetric, in that case, it is similar to a Hermitian operator. The existence of an operator C consisting of a CPT-frame is discussed. These concepts and results will serve a mathematical discussion about PT-symmetric quantum mechanics.     

Broadband planar nearfield acoustic holography based on one-third-octave band analysis

Planar nearfield acoustic holography (PNAH) is usually based on narrow-band, single frequency analysis, which is time consuming when the source behavior over a broad frequency range is of interest, as is the case with many industrial sources. In this paper a method, broadband planar nearfield acoustic holography based on one-third-octave band analysis (BPNAH), is described. Data relating to the complex band pressure on the hologram is obtained by combining the root-mean-square pressure corresponding to a one-third-octave band with the phase of the pressure corresponding to a single frequency line. Numerical simulations and measurements show that the BPNAH method allows a significant reduction in processing time, while keeping a similar accuracy to the conventional reconstruction, which is based on the summation of frequency by frequency in the corresponding band. As a simple, time-saving and robust technique, the BPNAH method is particularly well adapted to industrial studies.     

32 × 32 SOI CMOS image sensor with pinned photodiode on handle wafer

We have fabricated a 32 × 32 silicon on insulator (SOI) complementary metal oxide semiconductor (CMOS) active pixel image sensor with a pinned photodiode on a handle wafer. The structure of one pixel is a four-transistor type active pixel sensor (APS) which consists of a reset and a source follower transistor on a seed wafer, and is comprised of a photodiode, a transfer gate, and a floating diffusion on the handle wafer. The photodiode could be optimized for better quantum efficiency and low dark currents because its process on the handle wafer is independent of that of transistors on a seed wafer. Most of the wavelengths are absorbed within the visible range, because the optimized photodiode is located on the handle wafer. The image has been captured by the fabricated 32 × 32 SOI CMOS image sensor with array pixels, vertical scanner, horizontal scanner, and delta-difference sampling circuit.     

Discrete dislocation simulation of nanoindentation: the influence of obstacles and a limited number of dislocation sources

Nanoindentation is simulated on the computer by means of a 2D discrete dislocation model under the conditions of a constrained geometry. First, an indentation test near a grain boundary is investigated by the arrangement of only one boundary and second, an indentation test into the center of the surface of a small grain (lamella) is mimicked by the arrangement of two boundaries. The effect of a limited number of dislocation sources is studied by the simulations of an indentation test in a plastically deformable film on an ideal elastic substrate and by such tests on an ideal elastic film on a plastically deformable substrate. The discrete nature of plasticity is shown to have a significant influence on the mechanical material behavior in all our investigations.     

Laser decoration of precious metals

A technique for the laser coloration of precious metals is described that is based on the oxidation of a titanium film deposited on the surface of a metal. When laser radiation acts on the film, it is heated and oxidizes. Depending on the radiation parameters, the resulting oxide films have different thicknesses and, due to light interference, they acquire different colors. The visible color of the surface depends on the angle of viewing after imaging. The aim of this work is to identify the color palette of a gold plate’s surface with a thin film of titanium deposited on it. The titanium film is oxidized via fiber laser irradiation with a wavelength of 1.064 μm. Samples of color palettes are examined spectrophotometrically, and the chemical and mechanical stability of the resulting oxide coatings are tested.     

Drop impact on substrates with heterogeneous stiffness

Previous studies of drop impact mainly focus on homogeneous substrates while heterogeneous substrates remain largely unexplored. A convenient preparation strategy of stiff heterogeneous substrates is presented in this work, and the drop impact on such a stiffness-patterned substrate consisting of soft spirals surrounded by a rigid region is systematically investigated. The results show that the splash behavior of a drop on a stiffness-patterned substrate exhibits distinct characteristics from those on a homogeneous substrate. Prompt splash is more likely to occur on the substrate with the greater heterogeneity of stiffness, which is reflected in the lower critical impact velocity. Moreover, the splash velocity of emitted droplet is significantly larger on the heterogeneous substrate than that on a corresponding homogeneous substrate, especially at a higher impact velocity of the drop, indicating a stronger splash intensity on the heterogeneous substrate. The difference in drop splashing between homogeneous substrate and heterogeneous substrate is largely due to the stiffness heterogeneity, rather than the variation of overall stiffness of the substrate. The use of spiral shape provides a feasible solution for introducing stiffness heterogeneity of substrate. This study is conducive to the understanding of drop impact research beyond uniform substrates, reveals the potential of using stiffness-patterned substrates to control splash, and may find useful applications in industries related to drop impact and splash.     

Expectation and transition probability

It is shown that a separating or order-determining set of states on a quantum logic need not determine the expectations of observables. A formula is derived for the transition probability between states. Using this formula, it is shown that the propositions do not determine the transition probability in a certain sense. The form of the transition probability is derived for pure states on Hilbert space, dominated normal states on a von Neumann algebra, and absolutely continuous states on a measurable space. A metric is defined in terms of the transition probability.     

Strain induced epitaxial relationships of Cr on Co/Pd(111)

The growth and structure of Co ultra-thin films on Pd(111) and Cr on Co/Pd(111) have been analyzed by grazing incidence X-ray diffraction and low energy electron diffraction. It is shown that the in-plane lattice constant of the epitaxial Co film depends on the growth temperature. Although the strain decreases as a function of the Co film thickness, it persists for 20 monolayer (ML) films or even thicker. When Cr is deposited at room temperature on a strained Co film (10 to 20 ML thick) a Kurdjumov–Sachs epitaxial relationship is observed, whereas when Cr is deposited on a Co(0001) single-crystal or on a very thick Co film on Pd(111), a Nishyama–Wassermann orientation is obtained.     

Hamiltonian cycles on random lattices of arbitrary genus

A Hamiltonian cycle of a graph is a closed path that visits every vertex once and only once. It has been difficult to count the number of Hamiltonian cycles on regular lattices with periodic boundary conditions, e.g. lattices on a torus, due to the presence of winding modes. In this paper, the exact number of Hamiltonian cycles on a random trivalent fat graph drawn faithfully on a torus is obtained. This result is further extended to the case of random graphs drawn on surfaces of an arbitrary genus. The conformational exponent y is found to depend on the genus linearly.     

利用QuickBird数据进行热红外遥感成像模拟的研究

针对基于机载热像仪图像或随机产生仿真场景的早期热红外成像模拟系统,提出了对高分辨率QuickBird图像进行星载热红外成像模拟的方法。基于高分辨率QuickBird图像,采用ISODATA法进行非监督分类,得到土地分类专题图,通过地物光谱数据库获得场景地物温度及发射率,从而可获得地面辐亮度图像;利用大气辐射传输软件MODTRAN对其进行大气修正,结合卫星遥感器辐射定标系数,最终可得到卫星遥感器输出图像。仿真结果表明,利用QuickBird进行热红外遥感成像模拟是一种全新而有益的尝试,对伪装效果检验等具有一定的参考价值。     

The mechanics of a compliant motion suppression system for semisubmersibles

This paper describes experimental and theoretical work on a passive motion suppression system for semisubmersible vessels. The system incorporates a pneumatic compliancy which is designed to enhance the wave induced motion characteristics of such a vessel for offshore drilling and production service. The pneumatic compliancy is achieved through the use of open bottom tanks mounted on the vessel. The tanks pierce the water surface and trap a volume of air above their internal water level. During operation wave action on the tanks imparts an oscillating vertical force on the vessel which is 180 degrees out-of-phase with the inertia dominated wave induced heave force. As a result, vessel heave, roll and pitch motions are substantially reduced. Regular and irregular wave tests have been performed on a scale model enabling the motion reduction capabilities of such a system of be evaluated. Test data is compared with a multi-degree of freedom dynamic response calculation in the frequency domain in which the Morison equation is used for calculating wave induced drag and inertia loads on the semisubmersible. The paper is concluded with a discussion on the relative merits and drawbacks of incorporating a pneumatic compliancy into hitherto hydrodynamically rigid semisubmersible designs.     

Plasticity localization ahead of a crack tip modeled by 2D discrete dislocation dynamics

The formation of a plastic zone in the presence of a crack, in a bicrystal, is modeled by two-dimensional discrete dislocation dynamics. The influence of a large number of parameters is studied: the misorientation, the emission from the crack tip and the obstacle density which modifies the internal stress (hardening) and degree of localization of mobile dislocations (slip bands). Emphasis is put on obtaining the best ductility, since the focus is on face centered cubic materials. Finally, a strong effect of the plastic model on the dynamics and on the secondary slip (intensity and localization), beyond the influence of the initial distribution of sources and obstacles, is reported.     

Balls-in-boxes condensation on networks

We discuss two different regimes of condensate formation in zero-range processes on networks: on a q-regular network, where the condensate is formed as a result of a spontaneous symmetry breaking, and on an irregular network, where the symmetry of the partition function is explicitly broken. In the latter case we consider a minimal irregularity of the q-regular network introduced by a single Q node with degree Q>q. The statics and dynamics of the condensation depend on the parameter alpha=ln Q/q, which controls the exponential falloff of the distribution of particles on regular nodes and the typical time scale for melting of the condensate on the Q node, which increases exponentially with the system size N. This behavior is different than that on a q-regular network, where alpha=0 and where the condensation results from the spontaneous symmetry breaking of the partition function, which is invariant under a permutation of particle occupation numbers on the q nodes of the network. In this case the typical time scale for condensate melting is known to increase typically as a power of the system size.     

Force acting on a cylinder under ultrasonically induced cavitation

To elucidate mechanisms of cavitation action on a surface with microcapillary discontinuity and refine the model of the sonocapillary effect, the force acting on a cylinder is correlated with the height of a liquid in the capillary under cavitation, both quantities being measured at the same point of the ultrasonic field. It is found that the force acting on the cylinder is directed toward a cavitation cluster stabilized at the end face of the cylinder. This force can be enhanced with another cylinder placed on the side of the cluster coaxially with the first one. The dynamics of the cavitation cluster depending on the cylinder spacing is investigated in the case when one of the cylinders is on a pendulum suspension. The conditions for self-sustained oscillations of the pendulum are found. The dependence of the attracting force between the cylinders on the ultrasonic frequency and cylinder spacing is derived. The end-face-averaged pressure exerted on a cylinder of diameter 1.2 mm may reach 0.16 kPa, and the intracapillary pressure attains 0.89 kPa. Thus, the sonocapillary effect may be explained, at least partially, by a counterpressure arising from cluster-capillary interaction. This effect can be used in designing cavitation sensors and ultrasonic sources.     

Über die Gültigkeit der Fowler-Nordheim-Gleichung bei der Feldemission von Mikrospitzen auf ausgedehnten Metalloberflächen

The validity of the Fowler-Nordheim equation is discussed for field emission from protrusions on extended metal surfaces. With the model of a semi-spheroid on a plane the permeability of the potential barrier is calculated. It is found that the field enhancement factor calculated from the slope of the Fowler-Nordheim plots is then less than its value on the tip of the protrusion. Furthermore, this slope depends on the field, and it is nearly constant only if the height of the protrusion is above a certain limit. For a multitude of emitters the resulting slope of the Fowler-Nordheim plots is calculated. It is found that this slope is determined practically by the site with the highest field enhancement factor. Finally the influence of gas adsorption is discussed. Patch fields caused by inhomogeneous adsorption, and variation of the adsorption state by secondary processes may have a strong influence on the emission. In this case it is impossible to obtain the values of the field enhancement factor and of the emitting surface from the Fowler-Nordheim plots in a simple way.     

基于Stiefel流形的粒子滤波器研究

为了解决粒子滤波的粒子退化和粒子多样性丧失问题,提出了一种基于Stiefel流形的粒子滤波算法.该算法将系统模型置于Stiefel流形上,用朗之万分布描述过程转移概率分布,用矩阵正态分布表示似然函数分布,在流形分布上进行粒子采样.在计算加权粒子的均值时,将流形嵌入到欧氏空间中,先计算欧氏空间中的粒子均值,再将计算结果投影到嵌套流形上,这就排除了噪声统计特性对粒子权重方差的影响,得到了一种受系统状态模型限制较少的重要性概率密度函数通用选择方案.仿真时选取单变量非静态增长模型,仿真结果验证了该算法的实时性、鲁棒性,滤波精度和滤波效率均比无味粒子滤波算法更好.     

Spectral interferometric technique to measure the relative phase change on reflection from a thin-film structure

A two-step white-light spectral interferometric technique to measure the relative phase change on reflection from a thin-film structure is presented. The technique is based on recording of the channeled spectra at the output of a Michelson interferometer and their processing by using a windowed Fourier transform to retrieve the phase functions. In the first step, the phase difference between the beams of the interferometer with a thin-film structure is retrieved. In the second step, the structure is replaced by a reference sample of known phase change on reflection and the corresponding phase difference is retrieved. From the two phase differences, the relative phase change on reflection from the thin-film structure is obtained. The feasibility of the simple method is confirmed in processing the experimental data for a SiO₂ thin film on a Si wafer of known optical constants. Four samples of the thin film are used and their thicknesses are determined. The thicknesses obtained are compared with those resulting from reflectometric measurements, and good agreement is confirmed.