Simple Detection Based on Soft‐Limiting for Binary Transmission in a Mixture of Generalized Normal‐Laplace Distributed Noise and Gaussian Noise

In this letter, a simplified suboptimum receiver based on soft‐limiting for the detection of binary antipodal signals in non‐Gaussian noise modeled as a generalized normal‐Laplace (GNL) distribution combined with Gaussian noise is presented. The suboptimum receiver has low computational complexity. Furthermore, when the number of diversity branches is small, its performance is very close to that of the Neyman‐Pearson optimum receiver based on the probability density function obtained by the Fourier inversion of the characteristic function of the GNL‐plus‐Gaussian distribution.     

Evaluation of the dynamic performance variation of a serial manipulator after eliminating the self-weight influence

Manipulators used in the industrial field usually have a very stiff structure but without an equivalent payload on their end-effectors. This is because the stiff structure is used to prevent excessive deformation which will negatively impact the positioning accuracy of the manipulator, especially when the manipulator is fully extended. However, the stiff structure increases the weight of the manipulator and consumes much of the output of the constituent joint actuators in order to overcome the gravitational force resulting from the heavy structure. To cope with this problem, the concept of gravity balance was proposed decades ago, and there have been several approaches suggested to eliminate the influence of the self-weight of the structure. With the help of gravity balance, the output of the constituent joint actuators can fully be used to drive the manipulator and save considerable energy when the manipulator is in static or low-speed applications.For decades, many papers have discussed how to make a manipulator in gravity balance or how to design and apply a gravity balance mechanism to satisfy a certain application. However, none of them discuss what the influence on the dynamic performance of a manipulator is after it is equipped with a gravity balance mechanism or how to evaluate that influence. To rectify this insufficiency, this article utilizes acceleration radius to be the index of measuring the dynamic performance before and after a manipulator is equipped with a gravity balance mechanism and proposes a new index, the maneuverability ratio, to provide quantitative information to measure whether the dynamic performance of the manipulator increases or not after the gravity balance mechanism is applied.     

Inter-particle interaction induced by broadband radiation

The recent fabrication of optical traps using super-continuum light impresses the need for a theory of inter-particle interactions under such conditions. Development of the theory provides a basis for calculation of the observations expected under experimental conditions. An expression for the inter-particle potential energy induced by continuum states of light is first derived using quantum electrodynamics. This energy expression is cast as a function of the spectral irradiance of the light, and the electric susceptibility of the interacting particles. Specific results are derived for light with a Lorentzian spectrum. It is shown that by filtering part of the spectrum, it is possible to exert control over the length of linear particle chains organized along the Poynting vector. The results exhibit scope for the optical fabrication of moldable structures using broadband light.     

Comment on the paper: H.-E. Hwang, P. Han, Theoretical analysis for surface tilt and translation detection based on speckle photography in the Fresnel domain, Opt. Commun. 282 (2009) 351-354

In a recent paper [H.-E. Hwang, P. Han, Opt. Commun. 282 (2009) 351] a speckle based metrology system is proposed which it is claimed provides significant advantages over existing systems. In this paper, we show that the discussion presented in [H.-E. Hwang, P. Han, Opt. Commun. 282 (2009) 351] is deficient, and that several of the statements made are incorrect and/or misleading.     

Electronic energy gaps and optical properties of LaMnO3

We investigate electronic structure and optical properties of LaMnO₃ through density-functional-theory calculations with a recent improved exchange potential. Calculated gaps are consistent with recent experimental values, and calculated optical conductivities and dielectric constants as functions of photon energy are in excellent agreement with low-temperature experimental results. These lead to a satisfactory theoretical understanding of the electronic gaps and optical properties of LaMnO₃ without tuning atomic parameters and can help elucidate electronic structures and magnetic properties of other manganite materials.     

Synthesis and microstructure of Ca-doped BaTiO3 ceramics prepared by high-energy ball-milling

The calcium-substituted barium titanate ceramics were prepared by solid state reaction technique. High-energy ball-milling was used for processing the powder. The microstructure of Ba_1−xCa_xTiO₃ ceramics was investigated by SEM techniques. The microstructure of Ba_1−xCa_xTiO₃ ceramics shows dense and uniform micrograph in all samples and the grain size is large. In this study the quantitative analysis of the ceramographs is shown and the variation of the different parameters with various doping concentration is discussed. Compositional analysis is ascribed to the occupancy of some Ca²⁺ to the Ti⁴⁺ sites.     

Synthesis of praseodymium oxide nanofiber by electrospinning

Well-defined and uniform Pr₆O₁₁ nanofibers were synthesized by electrospinning of an aqueous sol-gel consisting of praseodymium nitrate hexa-hydrate and polyvinyl acetate. The synthesized Pr₆O₁₁ nanofibers mat was dried at 80 °C for 24 h under vacuum and finally annealed at 600 °C for 2 h in static air furnace. From crystalline properties, the synthesized Pr₆O₁₁ nanofibers XRD analysis revealed the typical cubic structure. The morphological observation showed that the synthesized Pr₆O₁₁ nanofibers composed of fibers length in several 100 nm and diameter of ∼20 nm. Similarly, transmission electron microscope (TEM) measurement revealed the good crystalline nature of the synthesized Pr₆O₁₁ nanofibers with the average diameter of ∼20 nm. Photoluminescence (PL) demonstrated a strong green-blue emission peak at 521 nm, suggesting that the Pr₆O₁₁ nanofiber exhibited good crystal quality with very less structural defects.     

Waterhammer modelling of viscoelastic pipes with a time-dependent Poisson's ratio

Poisson's ratio in viscoelastic materials is a function of time. However, recently developed waterhammer models of viscoelastic pipes consider it constant. This simplifying assumption avoids cumbersome calculations of double convolution integrals which appear if Poisson's ratio is time-dependent. The present research develops a mathematical model taking the time dependency of Poisson's ratio into account for linear viscoelastic pipes. Poisson's ratio is written in terms of relaxation function and bulk modulus which is assumed to be constant. The relaxation function is obtained from creep function given as the viscoelastic property data of pipe material. The results obtained from the present waterhammer model are compared with the experimental data for two different flow rates. The comparison reveals that with the application of the time-dependent Poisson's ratio and unsteady friction, the viscoelastic data of mechanical tests can directly be used for waterhammer analysis with less need for the calibration of the flow configuration. It was also shown that the creep curve calibrated based on the present model is closer to the actual creep curve than that calibrated based on previous models.     

Optical modes in nanoscale one-dimensional spin chains

The spin chain systems with one-dimensional magnetic ordering are promising candidates for quantum optical devices. This paper shows how the optical excitation can induce various phonon modes in an ideal Cu-O chain at various lengths. The calculation was carried out at different level theories including configuration interaction singles for excited states, density functional theory and second-order Möller-Plesset perturbation. In general, the number of modes increases with chain length due to growing asymmetry of atomic positions when chain exceeds 5 nm. There were, however, only two basic modes: one is associated with the symmetric oscillation of oxygen and another with the asymmetric motion of the same along the chain. At the length below 4.3 nm, the Raman activity of the symmetric mode (440 cm⁻¹) dominates. From analysis of density of states, this mode may be associated with the excitation across the lowest LUMO bands with changing in spin state.