k -Nearest Neighbors for automated classification of celestial objects

The nearest neighbors (NNs) classifiers, especially the k-Nearest Neighbors (kNNs) algorithm, are among the simplest and yet most efficient classification rules and widely used in practice. It is a nonparametric method of pattern recognition. In this paper, k-Nearest Neighbors, one of the most commonly used machine learning methods, work in automatic classification of multi-wavelength astronomical objects. Through the experiment, we conclude that the running speed of the kNN classier is rather fast and the classification accuracy is up to 97.73%. As a result, it is efficient and applicable to discriminate active objects from stars and normal galaxies with this method. The classifiers trained by the kNN method can be used to solve the automated classification problem faced by astronomy and the virtual observatory (VO). Supported by the National Natural Science Foundation of China (Grant Nos. 10473013, 10778724 and 90412016)     

Permeability Coefficients from NMR q-Space Data: Models with Unevenly Spaced Semi-permeable Parallel Membranes

The NMR "q-space" experiment conducted on water provides information on the sizes of repeated structures on the micrometer-length scale in heterogeneous samples, including cell suspensions or tissues. Under some circumstances these plots display coherence peaks, and it has been implied theoretically that the position of the peaks will vary with the rate of molecular exchange across the membranes. This has been demonstrated (qualitatively) with human erythrocytes in suspension. Thus, in the quest for a quantitative approach to the interpretation of such data, we address here the "inverse problem," namely the estimate of the permeability coefficient of membranes from q-space experiments. The present work describes theoretical predictions of q-space plots from molecules diffusing in a simple system of parallel semi-permeable membranes arranged with separations that alternate between two different values; this was designed to (loosely) mimic the intra- and extracellular compartments in a suspension of cells or a tissue. The development of the theory was facilitated by symbolic computation, and the analysis of synthetic data was shown to be achievable by the use of a three-layer back-propagation artificial neural network.     

应变Ge/Si1-xGex 价带色散模型

基于k·p微扰理论, 通过引入应变哈密顿量作为微扰, 建立了双轴应变Ge/Si_1-xGe_x价带色散关系模型. 模型适于任意晶向弛豫Si_1-xGe_x虚衬底上的应变Ge价带结构, 通过该模型可获得任意k方向应变Ge的价带结构和空穴有效质量. 模型的Matlab模拟结果显示, 应变Ge/Si_1-xGe_x价带带边空穴有效质量随Ge组分的增加而减小, 其各向异性比弛豫Ge更加显著. 本文研究成果对Si基应变Ge MOS器件及集成电路的沟道应力与晶向的设计有参考价值.     

光子湮没算符高次幂本征态的完备性问题

本文对光子湮没算符高次幂本征态的完备性问题进行了详细研究,给出了a^k正交归一本征态的正确的完备性关系.同时,纠正了现有文献报道中所出现的一些错误.     

A novel partial silicon on insulator high voltage LDMOS with low-k dielectric buried layer

A novel partial silicon-on-insulator (PSOI) high voltage device with a low-k (relative permittivity) dielectric buried layer (LK PSOI) and its breakdown mechanism are presented and investigated by MEDICI.At a low k value the electric field strength in the dielectric buried layer (E I) is enhanced and a Si window makes the substrate share the vertical drop,resulting in a high vertical breakdown voltage;in the lateral direction,a high electric field peak is introduced at the Si window,which modulates the electric field distribution in the SOI layer;consequently,a high breakdown voltage (BV) is obtained.The values of EI and BV of LK PSOI with kI=2 on a 2 μm thick SOI layer over 1 μm thick buried layer are enhanced by 74% and 19%,respectively,compared with those of the conventional PSOI.Furthermore,the Si window also alleviates the self-heating effect.     

Collimation of atomic beams by resonant laser radiation pressure

The application of the resonant light pressure created by an axially symmetrical light field for collimating atomic beams has been considered. As an example, consideration is given to the possibility of collimating an atomic beam by the light field produced by the reflection of a plane wave from the internal surface of a metal cone. It has been shown that the radiation pressure can reduce the atomic-beam transverse velocities to the value of the order of 100 cm/s which corresponds to effective temperature of about 10^–3 K. A method for producing collimated beams of cold atoms based on simultaneous deceleration and collimation of atomic beams by resonant laser radiation pressure is proposed.     

The effect of k-cubic Dresselhaus spin–orbit coupling on the decay time of persistent spin helix states in semiconductor two-dimensional electron gases

We study the theoretical effect of k-cubic （i.e, cubic-in-momentum） Dresselhaus spin-orbit coupling on the decay time of persistent spin helix states in semiconductor two-dimensional electron gases. We show that the decay time of persistent spin helix states may be suppressed substantially by k-cubic Dresselhaus spin-orbit coupling, and after taking the effect of k-cubic Dresselhaus spin-orbit interaction into account, the theoretical results obtained accord both qualitatively and quantitatively with other recent experimental results.     

1/L Expansions for a Class of PT-symmetric Potentials

The 1/L perturbative series for a special class of PT-symmetric potentials with centrifugal repulsive core are computed. Reality of obtained spectra is shown.     

Flat-band voltage shift in metal-gate/high-k/Si stacks

In metal-gate/high-k stacks adopted by the 45 nm technology node, the flat-band voltage (V_fb) shift remains one of the most critical challenges, particularly the flat-band voltage roll-off (V_fb roll-off) phenomenon in p-channel metal-oxide-semiconductor (pMOS) devices with an ultrathin oxide layer. In this paper, recent progress on the investigation of the V_fb shift and the origin of the V_fb roll-off in the metal-gate/high-k pMOS stacks are reviewed. Methods that can alleviate the V_fb shift phenomenon are summarized and the future research trend is described.     

A new approach to solve correlated k-distribution function

The resorting profile of absorption coefficient is fitted with Voigt function by employing the similarity between it and a single mixed broadened Voigt line type. In this way, simple mathematical fitting formulae are obtained to solve k-distribution (k-D) function at any pressure and temperature. Thus, a new correlated k-D method is proposed on the basis of it. Finally, taking mid-latitude summer atmosphere as an example, longwave cooling rates are calculated for three major gases by the new method, and then compared with the corresponding results by line-by-line integration.     

A diagrammatic categorification of q-boson and q-fermion algebras

In this paper, we study the diagrammatic categorification of q-boson algebra and also q-fermion algebra. We construct a graphical category corresponding to q-boson algebra. q-Fock states correspond to some kind of 1-morphisms, and the graded dimension of the graded vector space of 2-morphisms is exactly the inner product of the corresponding q-Fock states. We also find that this graphical category can be used to categorify q-fermion algebra.     

Thermal properties of high-k Hf1-xSixO2

Classical atomistic simulations based on the lattice dynalnics theory and the Born core-shell model are performed to systematically study the crystal structure and thermal properties of high-k Hfl-xSixO2. The coefficients of thermal expansion, specific heat, Griineisen parameters, phonon densities of states and Debye temperatures are calculated at different temperatures and for different Si-doping concentrations. With the increase of the Si-doping concentration, the lattice constant decreases. At the same time, both the coefficient of thermal expansion and the specific heat at a constant volume of Hf1-mSixO2 also decreases. The Griineisen parameter is about 0.95 at temperatures less than 100 K. Compared with Si-doped HfO2, pure HfO2 has a higher Debye temperature when the temperature is less than 25 K, while it has lower Debye temperature when the temperature is higher than 50 K. Some simulation results fit well with the experimental data. We expect that our results will be helpful for understanding the local lattice structure and thermal properties of Hf1-mSixO2.     

Analysis ofJCoupling-Induced Fat Suppression in DIET Imaging

The DIET (ordualintervalechotrain) sequence, a modification of thefastspinecho (FSE) sequence that selectively reduces signal from fat in MR images, has been investigated. The DIET sequence uses an initial echo spacing longer than that of a conventional FSE sequence, thus allowingJcoupling-induced dephasing to take effect. The sequence is evaluated theoretically, and its effectiveness on a hydrocarbon (1-pentene) is demonstrated numerically using density matrix calculations. The sequence is also evaluated experimentally usingin vitrosolutions andin vivoimaging. The efficacy of the sequence is compared for different lipid chemical structures, field strengths, and pulse sequence parameters.     

Be-composition effect on structure, electronic and optical properties of BexZn1-xO alloys

This paper carries out first principles calculation of the structure,electronic and optical properties of Be x Zn 1 x O alloys based on the density-functional theory for the compositions x = 0.0,0.25,0.5,0.75,1.0.The lattice constants deviations of alloys obey Vegard’s law well.The Be x Zn 1 x O alloys have the direct band gap(Γ-Γ) character,and the bowing coefficients are less than the available theoretical values.Moreover,it investigates in detail the optical properties(dielectric functions,absorption spectrum and refractive index) of these ternary mixed crystals.The obtained results agree well with the available theoretical and experimental values.     

Solutions of two-mode Jaynes-Cummings models

A simple procedure to solve two fully quantized non-linear Jaynes-Cummings models is presented, one in which an atom interacts with a two-mode radiation field in a Raman-type process and the other involving multiphoton interaction between the two-mode field and the atom. Effect of intensity-dependent coupling between the field and the atom in both the above-mentioned cases has also been investigated. The unitary transformation method presented here not only solves the time-dependent problem but also permits a determination of the eigensolutions of the interacting Hamiltonian at the same time. Graphical features of the time dependence of the population inversion have been analysed when one of the field modes is prepared initially in a coherent state while the other one in a vacuum state.      

Analysis of numerical limits in 2-D simulations of a ferromagnetic/antiferromagnetic interface using the random field Ising model

This paper explains the Random Field Ising Model simulations of a two-dimensional ferromagnetic/antiferromagnetic interface, influenced by the exchange-bias interaction. Exchange-biased shifts, coercivity fields, the number of unreversed spins as well as the numerical errors are provided. These were tested for different structure dimensions and boundary conditions in order to find limitations of the method. The algorithm developed is simple, very effective, and provides deeper insight into the nature of the exchange-bias phenomenon.     

A new k-interval selection technique for fast atmospheric radiance calculation in remote sensing applications

A new technique is proposed to generate the k-interval parameters, including the number of k-intervals, the equivalent absorption coefficients, and the quadrature weights when using the correlated k-distribution method for the computation of spectrally integrated three-dimensional (3D) atmospheric radiance. The main difference between the proposed technique and the traditional exponential sum fitting technique is that only quadrature weights are involved in the optimization process. To avoid the ill-conditioned problem in the proposed technique, the absorption coefficients with high value are dealt with by the delta log(k) (Δlog(k)) technique instead of involving them in the fitting procedure. The performance of the proposed technique is illustrated by radiance calculation results of cloudless and cloudy atmosphere for three different band settings. Results show that there are less relative errors with the proposed optimization technique than with the Δlog(k) technique under the same number of k-intervals. However, as the absorption becomes stronger, the performance of the proposed technique gradually decreases to the Δlog(k) technique. The relative root-mean-square error (RMSE) of radiance for 3D cloudy atmosphere can be controlled in less than 2% when the number of k-intervals is less than 10 particularly for weak absorption band, the RMSEs are less than 1% with only 6 terms.     

A two-dimensional threshold voltage analytical model for metal-gate/high-k/SiO2/Si stacked MOSFETs

In this paper the influences of the metal-gate and high-k/SiO 2 /Si stacked structure on the metal-oxide-semiconductor field-effect transistor（MOSFET） are investigated.The flat-band voltage is revised by considering the influences of stacked structure and metal-semiconductor work function fluctuation.The two-dimensional Poisson＇s equation of potential distribution is presented.A threshold voltage analytical model for metal-gate/high-k/SiO 2 /Si stacked MOSFETs is developed by solving these Poisson＇s equations using the boundary conditions.The model is verified by a two-dimensional device simulator,which provides the basic design guidance for metal-gate/high-k/SiO 2 /Si stacked MOSFETs.     

The effects of the choice of the k-interval number on radiative calculations

The selection of the number of k-interval is a foundation to correlated k-distribution method and the problem of how to do it still remains unsettled. It is pointed out by numerical computation in this work that choosing the number of k-interval is a major factor affecting accuracy and speed in radiative calculation. To increase the number of k-interval is an efficient method to improve the accuracy. However, it is found by this study that there exists a saturation of the accuracy to an increase of the number. The optimal rules on the number of k-interval choosing are proposed in the paper. Then, five versions on atmospheric absorption by gases appropriate for GCMs are given according to them.     

Upconversion of λ=3.39 μm He-Ne laser radiation in two-photon resonantly pumped Na vapor

Upconversion of low-level ir radiation at 3.39 μm to the near ultraviolet at 330.5 nm has been obtained using the resonantly enhanced third-order nonlinearity of Na atoms. This enhancement has been achieved by two-photon resonant pumping of the nonallowed Na 3s–5s transition with a dye-laser radiation at 602.4 nm. Self-phase-matching has been observed.