Supervised adaptive clustering: A hybrid neural network clustering algorithm

A neural network architecture is introduced which implements a supervised clustering algorithm for the classification of feature vectors. The network is selforganising, and is able to adapt to the shape of the underlying pattern distribution as well as detect novel input vectors during training. It is also capable of determining the relative importance of the feature components for classification. The architecture is a hybrid of supervised and unsupervised networks, and combines the strengths of three wellknown architectures: learning vector quantisation, backpro-pagation and adaptive resonance theory. Network performance is compared to that of learning vector quantisation, back-propagation and cascade-correlation. It is found that performance is generally as good as or better than the performance of these other architectures, while training time is considerably shorter. However, the main advantage of the hybrid architecture is its ability to gain insight into the feature pattern space.Nomenclature O _j The output value of thejth unit - I _i Theith component of the input pattern - W _ij The weight of the cluster connection between theith input and thejth unit - B _ij The weight of the shape connection between theith input and thejth unit - N The dimension of the input patterns - v _j The vigilance parameter of thejth unit - v _init The initial vigilance parameter value - v _rate The change in the vigilance parameter value - X _i Theith direction in anN-dimensional coordinate system - T _k The classification tag of thekth unit - C The classification tag of the current input vector - (p) The learning rate at thepth epoch for the cluster weights - p The current epoch - P The total number of epochs - E _k The error associated with thekth unit - The constant learning rate for the shape weights - a _j The age in epochs of thejth unit     

The photoionization of excited hydrogen atom in plasmas

The photoionization processes of excited hydrogen atoms in plasma environments are investigated using the method of complex coordinate rotation. The standard Debye–Hückel model and modified Debye–Hückel model are adopted to describe the plasma screening effects. The photoionization cross sections of plasma-embedded excited hydrogen atoms varied with different screening lengths are displayed to illustrate the influence of plasma screening. The results of the Debye–Hückel model compared with the modified Debye–Hückel are presented. The shape resonances and Cooper minima due to the plasma screening are observed and discussed.     

Correlations of the impedance parameters and conductivity and permittivity of liquid and gel phases in a series piezoelectric quartz crystal sensor

The impedance characteristics of a series piezoelectric quartz crystal (SPQC) sensor were investigated using a network/impedance analyzer. The correlations between the impedance parameters, including the magnitude and phase of the impedance and the resonant frequencies, and the conductivity and/or the permittivity of the test solutions were derived theoretically and in good agreement with the experimental results. It was shown that the value of the series frequency (f_s) decreases with increasing conductivity and permittivity of the liquid. The parallel frequency (f_p) is the constant. The values of the maximum impedance (|Z|_max) and corresponding frequency (f_max,), are not related to the conductivity and permittivity of the liquid. The value of the minimum impedance (|Z|_min) decreases with increasing permittivity and has a maximum in a solution of middle conductivity. The corresponding frequency (f_min) has the same value as the f_s. The maximum phase of the impedance (θ_max) increases slightly with increasing permittivity and has a minimum in electrolyte solution of middle conductivity. In the impedance–frequency curves, there is an iso-impedance point for the SPQC in electrolyte solutions. The SPQC method was applied to monitor the process of hydrogel formation.     

Simultaneous kinetic spectrophotometric determination of sulfide and sulfite ions by using an optode and the partial least squares (PLS) regression

The characterization of an optical sensor membrane is described for simultaneous determination of sulfite and sulfide ions based on the immobilization of crystal violet on a triacetylcellulose membrane. The absorbance of the membranes decreased by increasing sulfite and sulfide concentration. The partial least squares (PLS-1) calibration model based on spectrophotometric measurement for simultaneous determination of sulfite and sulfide ions was applied. This method is based on the difference between the rate of the reaction of sulfide and sulfite with membranes in pH 7.0 buffer solution and at 25 °C. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 18 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range of 200–2000 μg mL⁻¹ (2.5–25 mmol L⁻¹) and 80–900 μg mL⁻¹ (2.5–28.125 mmol L⁻¹) for sulfite and sulfide, respectively. The sensor can readily be regenerated with water and the color is fully reversible. The sensor was successfully applied to the simultaneous determination of sulfide and sulfite in water samples.     

Wideband bandpass filtering branch‐line balun with high‐isolation

The wideband bandpass filtering branch‐line balun with high isolation is presented in this paper. The proposed balun can be designed for wideband performances by choosing a proper characteristics impedance of input vertical transmission line and odd‐mode impedance of parallel‐coupled lines. The proposed balun was designed at a center frequency (f₀) of 3.5 GHz for validation. The measured results are in good agreement with the simulations. The measured power divisions are ?3.31 dB and ?3.24 dB at f₀ and ?3 ± 0.17 dB within the bandwidth of 0.95 GHz (3 GHz to 3.95 GHz). The input return loss of 24.09 is measured at f₀ and higher than 20 dB over the same bandwidth. Moreover, the measured output losses are better than 11 dB within a wide bandwidth. The isolation between output ports is 20.32 dB at f₀ and higher than 13.2 dB for a broad bandwidth from 1 GHz to 10 GHz. The phase difference and magnitude imbalance between two output ports are 180° ± 4.5° and ± 0.95 dB, respectively, for the bandwidth of 0.95 GHz.     

On a high-order compact scheme and its utilization in parallel solution of a time-dependent system on a distributed memory processor

The focus of this study is the design of a parallel solution method that utilizes a fourth-order compact scheme. The applicability of the method is demonstrated on a time-dependent parabolic system with Neumann boundaries. The core of the parallel computing facilities used in the study is a 2-head-node, 224-compute-node Apple Xserve G5 multiprocessor. The system is first discretized in both time and space such that it remains in its stability regimes, before being solved with the method. The solution requires time marching in which every time step, h _t , calls for a single parallel solve of the intermediary subsystems generated. The solution uses p processors ranging in numbers from 3 to 63. The speedups, s _p , approach their limiting value of p only when p is small. The solution produces good computational results at large p, but poor results as p becomes progressively small. Also, the parallel solution produces accurate results yielding good speedups and efficiencies only when p is within some reasonable range of values. The intermediary systems generated by this method are linear and fine-grained, therefore, they are best suited for solution on massively-parallel processors. The solution method proposed in this study is, therefore, expected to yield more impressive results if applied in a massively-parallel computing environment.     

A 5 GHz LC-VCO frequency synthesizer for unlicensed band of WiMAX

This paper presents a low power and low phase noise CMOS integer-N frequency synthesizer based on the charge-pump Phase Locked Loop (PLL) topology. The frequency synthesizer can be used for IEEE 802.16 unlicensed band of WiMAX (World Interoperability for Microwave Access). The operation frequency of the proposed design is ranged from 5.13 to 5.22 GHz. The proposed Voltage-Controlled Oscillator (VCO) achieves low power consumption and low phase noise. The high speed divider is implemented by an optimal extended true single phase clock (E-TSPC) prescaler. It can achieve higher operating frequency and lower power consumption. A new frequency divider is also proposed to eliminate the hardware overhead of the S counter in the conventional programmable divider. The proposed frequency synthesizer consists of a phase-frequency detector (PFD), a charge pump, a low-pass loop filter, a VCO, and a frequency divider. The simulated phase noise of the proposed VCO is −121.6 dBc/Hz at 1 MHz offset from the carrier frequency. The proposed frequency synthesizer consumes 13.1 mW. The chip with an area of 1.048 × 1.076 mm² is fabricated in a TSMC 0.18 μm CMOS 1P6M technology process.     

WO3 nanocrystals: Synthesis and application in highly sensitive detection of acetone

WO₃ nanocrystals have been prepared by a sol-gel route and characterized by X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. The experimental results show that WO₃ nanocrystals have a high crystallographic quality and a good dispersivity. The particles’ sizes are in the range of 25-100 nm. The fabricated WO₃ nanocrystal-based sensors have an excellent sensitivity and selectivity to acetone, and display a rapid response and recovery characteristics. The developed sensors exhibit a detection limit down to 0.05 ppm at 300 °C, rendering a promising application in noninvasive diagnosis of diabetes. The response mechanism of the WO₃ nanocrystal sensor to low concentration of acetone has been discussed based on the depletion layer model.     

SBGBBG, a program to evaluate the macroscopic strain/stress tensor of a polycrystalline sample from X-ray reflection positions

The evaluation of the strain/stress tensor from strain measured by X-ray diffraction requires a transformation from the sample system S to the laboratory system L. The transformation matrix A depends on the diffractometer geometry and the sample tilting. The conversion from strain to stress relies on poly-crystal elastic compliances S′_mnop. The averaging is done about the orientation of the diffracting crystallites. The orientation distribution function (ODF) serves as weighting function. The computer program SBGBBG carries out these calculations.     

Amperometric biosensor for catechol using electrochemical template process

A novel amperometric biosensor for the determination of catechol was developed accordingly to the electrochemical template procedure. The optimum fabricating conditions of the biosensor were studied. The resulting biosensor with the limit of less than 0.05 μM can be used for detection of catechol in the linear range of 2.5-140 μM. The maximum response current (I_max) and the Michaelis-Menten constant (k′_m) are 3.08 μA and 77.52 μM, respectively. The activation energy (E_a) of the polyphenol oxidase (PPO) catalytic reaction is 25.56 kJ mol⁻¹ in the B-R buffer. The stability of the PANI-CA biosensor fabricated with the electrochemical template process (retains 86% of the original activity after four months) is much higher than that fabricated with one-step and two-step processes (retains 75% of the original activity after four months). The effects of potential and pH on the response current of the biosensor are also described.     

Modeling of thermodynamic properties of ABr-PrBr3 (A=Li-Cs ) systems

The thermodynamic properties of ABr-PrBr₃(A=Li-Cs) systems were assessed by the CALPHAD method. The liquid phase in the systems was described by the non-stoichiometric associate model. The entropies of mixing in the liquid were evaluated from experimental liquidus and enthalpy of mixing data. For the pseudobinary compounds A₃PrBr₆,APr₂Br₇, and A₂PrBr₅ (A=K,Rb) and Cs₃PrBr₆ and CsPr₂Br₇, the dependences of Gibbs energies of formation on temperature were calculated. The anomalies of sequences of thermodynamic properties in RbBr-PrBr₃ were observed and discussed. The nature of the liquid phase and precision of calculations of the Rb₂PrBr₅(s) compound were discussed.     

Highly sensitive NO2 sensor based on square-like tungsten oxide prepared with hydrothermal treatment

The square-like WO₃ nanosheets were synthesized by hydrothermal treatment of irregular WO₃ nanosheets prepared through acidification of Na₂WO₄·2H₂O. The obtained square-like and irregular WO₃ nanosheets were characterized with field emission scanning electron microscopy, X-ray powder diffraction and transmission electron microscopy. The gas sensing properties of sensors based on as-prepared samples were investigated. The results indicated that both samples exhibited high response to NO₂. The sensor based on square-like WO₃ nanosheets exhibited remarkably enhanced response and faster response/recovery time for NO₂ compared with that based on irregular nanosheets. Especially, the sensor based on square-like WO₃ nanosheets could detect NO₂ down to 40 ppb, which covered environmental standard. A possible reason for the influence of unique structure on the sensing properties of sensors based on square-like WO₃ was proposed.     

声色季

先赌为快：《满城尽带黄金甲》；《皮囊》；《辛普森一家》；《无间行者》[编者按]     

Modelling of the thermodynamic properties of the ABr–CeBr3 (A=Li–Cs ) systems

The thermodynamic properties of the ABr–CeBr₃ (A=Li–Cs) systems were assessed by the CALPHAD method. The liquid phase in the systems was described by the non-stoichiometric associate model. The entropies of mixing in the liquid ABr–CeBr₃ (A=Li,Na) systems are evaluated from experimental data. The entropies of mixing in the liquid ABr–CeBr₃ (A=K,Rb,Cs) systems, and the Gibbs energies of formation of pseudobinary compounds: A₃CeBr₆(s), A₂CeCl₅(s), ACe₂Cl₇(s) (A=K,Rb,Cs) were estimated due to the lack of experimental data. The presence of solid solution near NaBr was predicted from calculations. The nature of the liquid phase and precision of calculations were discussed.     

Massively parallel processing in coastal ocean circulation model

Massively parallel computers are becoming quite common in their use in computational fluid dynamics. In this study, a parallel algorithm of a 3-D primitive-equation coastal ocean circulation model is designed on the hypercube MIMD computer architecture. The grid is partitioned using one-dimensional domain decomposition. The code is tested in a uniform rectangular grid problem for which the model domain in each node is a cube. For the problem where the grain size (n _y ) is fixed, the speedup is linear and is close to ideal forP 8 processors. The overhead (F _C ) increases as the number of processors increases. The background overhead is inversely proportional to the size of the grain. The slopeF _C vs.P is a measure of the fraction of non-parallel code. For the problem where the domain is fixed, the speedup is 7.8 using 8-processors and 29.6 using 32-processors. The overhead increases linearly withP. The slopeF _C is a measure of the communication cost. The load balancing problem is examined for a model of the Gulf of California whose computational domain is irregular.     

Experimental investigation and first-principle calculations coupled with thermodynamic modeling of the Mn–Nd phase diagram

The complete Mn–Nd phase diagram was established experimentally by means of key samples and diffusion couple techniques. The phase transformation temperatures, crystal structures and phase equilibria were studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and scanning electron microscope (SEM) techniques. Three compounds in the Mn-rich side and two terminal solid solutions in the Nd-rich side were observed. The compounds Mn₂Nd, Mn₂₃Nd₆, and Mn₁₇Nd₂ form peritectically at 850, 940, and 1025 °C, respectively. The eutectoidal decompositions of the compounds, Mn₂Nd, and Mn₂₃Nd₆, were confirmed in the temperature ranges of 650–550 and 550–400 °C, respectively, using EPMA. The maximum solubility of Mn in DHCP-Nd was found to be 2.3 at% Mn at the 685 °C eutectic temperature. The solvus line of DHCP-Nd was determined using EPMA. The solubility of Mn in BCC-Nd was extrapolated from DSC data to be 5.0 at% Mn at 728 °C. The existence of a Mn₁₇Nd₂ phase of the Th₂Ni₁₇ type structure was confirmed using EPMA and XRD. The system was modelled using CALPHAD methodology. The quasi-chemical model (QCM) was used to describe the liquid phase, the terminal solution phases were modeled as substitutional solutions using the random mixing model, and the intermetallic compounds were treated as stoichiometric phases. The enthalpies of formation of the system compounds were calculated using the electronic density functional method. The resulting enthalpy of mixing was in good agreement with the literature.     

Design and optimization of a lactate amperometric biosensor based on lactate oxidase cross-linked with polymeric matrixes

The design and characterization of a lactate biosensor is described. The biosensor is developed through the immobilization of lactate oxidase (LOD) in an albumin and mucin composed hydrogel. The enzyme is then cross-linked with glutaraldehyde to the polymeric matrix and entrapped between two polycarbonate membranes. The hydrogen peroxide produced by the reaction of lactate and LOD is detected on a Pt electrode operated at 0.65 V versus Ag|AgCl. The performance of the biosensor was evaluated in matrixes with different amounts of albumin, mucin and glutaraldehyde. The response time of the sensor to 10 μM lactate required 90 s to give a 100% steady-state response of 0.079 μA. Linear behavior was obtained for 0.7 μM < c_Lac < 1.5 mM. The detection limit calculated from the signal to noise ratio was 0.7 μM. Only 0.1 U of enzyme was necessary to get a biosensor with a relatively high current flow and an excellent stability over a storage period of 30 days. High reproducibility in the response was obtained when several biosensors were prepared with the same composition.     

洪河湿地植被地上生物量遥感反演研究

在对洪河湿地植被地上生物量实地采样调查的基础上,利用准同步的TM数据建立了洪河湿地地上生物量遥感反演模型。主要研究了洪河湿地植被地上生物量的空间分布情况,并结合研究区的DEM分析生物量空间分布特征和高程的相关关系。并分析了不同生物量范围内,生物量与高程之间相关性存在差异的原因。研究表明:多元回归模型与其他模型相比拟合精度最高,决定系数为0.813,是洪河湿地地上生物量估算的精度最优模型;经估算得到2007年洪河湿地地上生物量主要集中分布于600~1 200 g/m²之间,总生物量为2.4856×10⁸g,平均生物量为934.7105 g/m²。通过生物量与DEM的相关分析得到,在生物量值为0~600 g/m²的低生物量分布区域,生物量与高程之间存在较好的相关性,相关系数为0.79839;在生物量为600~1 200 g/m²和1 200 g/m²以上范围内,生物量与高程值之间相关性较弱。     

Compact searchable static binary trees

A compact searchable representation of static binary trees is presented that can be traversed in O(h) time where h is the height of the tree. The space requirement for a tree with n nodes is less than 2.5n+(h−1)(2+log₂((n−1)/(h−1))) bits. The access time per node is in O(1). The scheme uses a cumulative-count technique to map the nodes at each level in the tree into sequential memory locations. The mapping requires the nodes to be of uniform size.     

Thermodynamic description of the Cr–Ge system

The Cr–Ge binary system was thermodynamically optimized using the CALPHAD method. The liquid phase was described by means of an associate solution model. The BCC terminal solid solution was described by the substitutional solution model. The two-sublattice model was used to describe the non-stoichiometric compounds Cr₃Ge, αCr₅Ge₃ and βCr₅Ge₃. The Cr₁₁Ge₈, CrGe and Cr₁₁Ge₁₉ phases were modeled as stoichiometric compounds. A set of thermodynamic parameters for the Cr–Ge system was obtained via thermodynamic optimization using assessed experimental data. The calculated phase diagram and thermodynamic properties agree well with most of the experimental data.