Analytical characterization of detection SNR for PR target design in Viterbi-based receivers

In this paper, we address the problem of designing the optimum partial-response (PR) target that results in the best bit-error-rate (BER) performance in Viterbi-like detectors when applied for signal detection in digital magnetic recording systems. We present a detailed analysis of the effective detection signal-to-noise ratio (SNR_eff), which is closely related to the BER performance of a Viterbi detector. We show that SNR_eff is a concave function with a unique global maximum corresponding to the magnitude frequency response of the optimum targets. Thus, any simple search approach is guaranteed to reach the optimum target. We consider the cases of single dominant error event and multiple dominant error events. Numerical and simulation results are presented to corroborate our analytical results for perpendicular magnetic recording channels.     

Molecular dynamics simulation of liquid tetrahydrofuran: on the uniqueness of force fields

Molecular dynamics simulations of liquid tetrahydrofuran have been performed with different force fields to illustrate that there is no unique way to model a given system of molecules. Parameters for the force fields have been taken from existing force fields and have been used as starting guesses for a simplex optimization. In spite of the very different final parameter values, all optimized force fields reproduce properly the physical properties for which they have been optimized, but not necessarily other ones.     

Many body perturbation methods in a discrete orbital basis: Application to CH4 and Ne

Discrete basis many body perturbation calculations have been performed on Ne and CH₄ in a basis which mimics Boys' oscillator orbitals. The L-shell correlation energy obtained for Ne was –0.347 which is to be compared with the best numerical basis many body perturbation result of –0.336 ± 0.01 obtained by Lee, Dutta and Das and the best variational result of –0.322 obtained by Sasaki and Yoshimine. An analysis of 3- and 4-body corrections (pair-pair repulsions) and the effects of many body EPV renormalization for both localized and canonical SCF orbitals is presented.     

Quasi-SU(3) truncation scheme for even–even sd-shell nuclei

The quasi-SU(3) symmetry was uncovered in full pf and sdg shell-model calculations for both even–even and odd–even nuclei. It manifests itself through a dominance of single-particle and quadrupole–quadrupole terms in a Hamiltonian used to describe well-deformed nuclei. A practical consequence of the quasi-SU(3) symmetry is an efficient basis truncation scheme. In [C.E. Vargas et al., Phys. Rev. C 58 (1998) 1488] it is shown that when this type of Hamiltonian is diagonalized in an SU(3) basis, only a few irreducible representations (irreps) of SU(3) are needed to describe the yrast band, the leading S=0 irrep augmented with the leading S=1 irreps in the proton and neutron subspaces. In the present article the quasi-SU(3) truncation scheme is used, in conjunction with a “realistic but schematic” Hamiltonian that includes the most important multipole terms, to describe the energy spectra and B(E2) transition strengths of ^20,22Ne, ²⁴Mg and ²⁸Si. The effect of the size of the Hilbert space on both sets of observables is discussed, as well as the structure of the yrast band and the importance of the various terms in the Hamiltonian. The limitations of the model are explicitly discussed.     

Spin‐orbit ZORA and four‐component Dirac–Coulomb estimation of relativistic corrections to isotropic nuclear shieldings and chemical shifts of noble gas dimers

Hartree–Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange‐correlation functionals were used for nonrelativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton, and xenon dimers and free atoms. Relativistic corrections were calculated with the scalar and spin‐orbit zeroth‐order regular approximation Hamiltonian in combination with the large Slater‐type basis set QZ4P as well as with the four‐component Dirac–Coulomb Hamiltonian using Dyall's acv4z basis sets. The relativistic corrections to the nuclear magnetic shieldings and chemical shifts are combined with nonrelativistic coupled cluster singles and doubles with noniterative triple excitations [CCSD(T)] calculations using the very large polarization‐consistent basis sets aug‐pcSseg‐4 for He, Ne and Ar, aug‐pcSseg‐3 for Kr, and the AQZP basis set for Xe. For the dimers also, zero‐point vibrational (ZPV) corrections are obtained at the CCSD(T) level with the same basis sets were added. Best estimates of the dimer chemical shifts are generated from these nuclear magnetic shieldings and the relative importance of electron correlation, ZPV, and relativistic corrections for the shieldings and chemical shifts is analyzed. © 2015 Wiley Periodicals, Inc.     

Matlab编程法在测量氦氖激光波长实验数据处理中的应用探索

使用新型的WSM-T-Ⅱ型台式迈克尔逊干涉仪可以测量氦氖激光波长,传统的数据处理方法是逐差法,计算量大,既繁琐又容易出错。用Matlab软件的编程法处理实验测得的数据,程序运行后可以直接得到氦氖激光波长及相应的误差分析,无需进行运算,准确而快捷,是大学物理实验教学中实验数据处理的一种新方法。     

The influence of isotope substitution of neon atom on the integral cross sections of rotational excitation in Ne-Na2 collisions

This paper applies the multiple ellipsoid model to the 16 Ne (20 Ne,28 Ne,34 Ne)-Na 2 collision systems,and calculates integral cross sections for rotational excitation at the incident energy of 190 meV.It can be seen that the accuracy of the integral cross sections can be improved by increasing the number of equipotential ellipsoid surfaces.Moreover,by analysing the differences of these integral cross sections,it obtains the change rules of the integral cross sections with the increase of rotational angular quantum number J,and with the change of the mass of isotope substitution neon atom.Finally,the contribution of different regions of the potential to inelastic cross sections for 20 Ne-Na 2 collision system is investigated at relative incident energy of 190 meV.     

He-Ne激光对小麦幼苗增强UV-B辐射损伤修复的影响

采用He-Ne激光(5mW/mm²)来辐照处理经增强UV-B(10.8kJ·m^-2·d^-1)辐射损伤的小麦幼苗,通过荧光光谱测定其中双链DNA(dsDNA)的含量,分析研究了He-Ne激光对小麦DNAUV-B损伤的切除修复的影响和机制,以探明激光对UV-B损伤的修复途径及机制.结果表明:He-Ne激光能明显增强UV-B辐射处理后小麦种子的萌发力;小麦对UV-B辐射损伤具有一定的切除修复能力,切除修复的高峰期发生在UV-B辐射后4～6h内;He-Ne激光主要通过促进小麦的切除修复途径影响小麦对UV-B损伤的修复,而且能增强小麦的切除修复能力,其促进作用在修复高峰期(5h)表现尤为明显.     

Local Magnetic Nanoparticle Delivery in Microvasculature

The transport and capture of therapeutic magnetic nanoparticles in human microvasculature is studied numerically. The nanoparticles are injected into a vascular system upstream from malignant tissue, and are captured at the tumour site with the aid of a local applied magnetic field positioned outside the body. Taking into account the dominant magnetic and fluidic forces on the particles, our study shows that the nanoparticles can be directed to and concentrated at the desired zone that is within a few centimetres from the surface of the body. In addition, influence of the particles size, average blood flow velocity and the diameter of the blood vessel on the captured efficiency are parametrically analysed.