Influence of reaction temperature on the formation process of ZnO quantum dots and the optical properties

ZnO quantum dots (QDs)with the sizes of 3.0-5.6 nm are synthesized by solution-phase method at different temperatures. We find that temperature has great influence on the size of ZnO QDs. The growth process is the most sensitive to temperature, and the process is well explained by Lifshitz-Slyozov-Wagner (LSW) model. By photoluminescence (PL) spectra of the quantum dots at different temperatures and reactive time, we come to a conclusion that ultraviolet emission is mainly due to surface defects, and the or...     

High-power superfluorescent source of Yb^3＋ -doped double-cladding photonic crystal fiber

A new type of high-power broadband superfluorescent source of Yb^3＋ -doped double-cladding photonic crystal fiber is reported experimentally, which is pumped at 976 nm by a high-power laser diode with the end-coupling method. We have obtained a smooth broadband output of superfluorescence The maximum output power is 1.649 W with a slope efficiency of 56.7%. The 3 dB bandwidth is 22.4 nm To the best of our knowledge, this is the first report about SFS with such high output power of 1.649 W.     

High stable power control of a laser diode

For a high precise sensing and measuring system,theerror of measurement resulting fromthe fluctuation ofthe light source must be considered[1-3].The main noisesources include fluctuation of current source,self-heat ,aging and theintrinsic noises of a lase…     

Design of a multi-channel free space optical interconnection component

A multi-channel free space optical interconnection component, fiber optic rotary joint, was designed using a Dove prism. When the Dove prism is rotated an angle of at around the longitudinal axis, the image rotates an angle of 2 at. The optical interconnection component consists of the signal transmission system, Dove prim and driving mechanism. The planetary gears are used to achieve the speed ratio of 2：l between the total optical interconnection component and the Dove prism. The Clenses are employed to couple different optical signals in the signal transmission system. The coupling loss between the receiving fiber of stationary part and the transmitting fiber of rotary part is measured.     

Detection of Cardiac Signal Characteristic Point Using Log-Domain Wavelet Transform Circuits

To meet the requirement of low power consumption in biomedical implantable pacemaker applications, a novel method based on balanced log-domain wavelet transform (WT) circuits has been developed for detecting QRS complexes of cardiac signals. By using a hybrid particle swarm optimization algorithm (PSO) combined with sequential quadratic programming, an excellent approximation of the first derivative of a Gaussian wavelet is achieved. The WT circuits are composed of filters whose impulse response is the approximation of the Gaussian wavelet. The WT filter design is based on a time inverse follow-the-leader feedback structure with class-AB balanced log-domain integrators as the main building blocks. HSPICE simulation shows that the power consumption is only 62 nW per scale for a 1.2 V supply, and the dynamic range is 86 dB for 2% total harmonic distortion. The high accuracy of the QRS complex detection method has been validated using the MIT-BIH database. This work was supported by the National Natural Science Foundation of China under Grant No. 50677014, Doctoral Special Fund of Ministry of Education under Grant No. 20060532002, High-Tech Research and Development Program of China (No. 2006AA04A104), the Program for New Century Excellent Talents in University of China (NCET-04-0767), and the Foundation of Hunan Provincial Science and Technology (06JJ2024).     

P-μc-Si1-xGex ：H thin film by VHF-PECVD

In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium （p-μc-Si1-xGex：H） was deposited by very high frequency plasma-enhanced chemical vapor deposition （VHF-PECVD） from SiH4 and GeF4 mixtures. The effect of GeF4 concentration on films＇ composition, structure and electrical properties was studied. The results show that with the increase of GeF4 concentration, the Ge fraction x increases. The dark conductivity and crystalline volume fraction increase first, and then decrease. When the GC is 4%, p-μc-Si1-xGex：H material with high conductivity, low activation energy （σ= 1.68 S/cm, E8=0.047 eV）, high crystalline volume fraction （60%） and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 nm was achieved. The experimental results were discussed in detail.     

A Generalized Parameter-Dependent Approach to Robust H ∞ Filtering of Stochastic Systems

This paper is concerned with the problem of robust H _∞ filtering for discrete-time stochastic systems with state-dependent stochastic noises and deterministic polytopic parameter uncertainties. We utilize the polynomial parameter-dependent approach to solve the robust H _∞ filtering problem, and the proposed approach includes results in the quadratic framework that entail fixed matrices for the entire uncertain domain and results in the linearly parameter-dependent framework that use linear convex combinations of matrices as special cases. New linear matrix inequality (LMI) conditions obtained for the existence of admissible filters are developed based on homogeneous polynomial parameter-dependent matrices of arbitrary degree. As the degree grows, a test of increasing precision is obtained, providing less conservative filter designs. A numerical example is provided to illustrate the effectiveness and advantages of the filter design methods proposed in this paper. This work was supported by HKU CRCG 200611159157, the National Nature Science Foundation of China (60504008), The Research Fund for the Doctoral Programme of Higher Education of China (20070213084), the Fok Ying Tung Education Foundation (111064), and the Key Laboratory of Integrated Automation for the Process Industry (Northeastern University), Ministry of Education of China.     

Research on fuzzy neural network algorithms for nonlinear network traffic predicting

Neural networks provide massive parallelism,robust-ness ,and approxi mate reasoning,which are i mportantfor dealing with uncertain,inexact ,and ambiguous data,withill-defined problems and sparse data sets[1].It hasbeen proved that a neural network system …     

Diode-pumped actively Q-switched Nd： YAG laser at 946 nm

A diode-pumped Nd： YAG acousto-optically（A-O） Q-switched laser at wavelength 946 nm formed with a simple plane-plane cavity has been demonstrated. The maximum average output power was 850 mW. The highest peak power was 531 W with the pulse repetition rate of 20 kHz and pulse width of 80 ns at the incident pump power of 19.5 W.     

COMBINATORIAL DESIGN APPROACHES FOR AUTOMATIC TEST GENERATION

The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n ≥ 2) parameters be covered by at least one test. This letter proposed two different test generation algorithms based on combinatorial design for the n-way coverage criterion. The automatic test generators are implemented and some valuable empirical results are obtained.     

Delay-Dependent Robust H ∞ Filtering for Uncertain Neutral Stochastic Time-Delay Systems

This paper is concerned with the problem of robust H _∞ filtering for neutral stochastic time-delay systems with norm-bounded parameter uncertainties. By introducing appropriate slack matrix variables, both a delay-dependent stochastic stability condition and a delay-dependent bounded real lemma are obtained in terms of linear matrix inequalities. A delay-dependent condition for the solvability of the robust H _∞ filtering problem is also proposed. Desired H _∞ filters are designed that guarantee the filtering error system to be robustly stochastically stable and satisfy a prescribed H _∞ performance level for all admissible uncertainties. A numerical example is provided to demonstrate the effectiveness of the proposed approach. This work is supported by the National Science Foundation for Distinguished Young Scholars of People’s Republic of China under Grant 60625303, the Specialized Research Fund for the Doctoral Program of Higher Education under Grant 20060288021, and the Natural Science Foundation of Jiangsu Province under Grant BK2008047.     

Delay-Dependent Robust H ∞ Admissibility and Stabilization for Uncertain Singular System with Markovian Jumping Parameters

This paper investigates the problem of delay-dependent robust H _∞ admissibility and stabilization for uncertain singular time delay systems with Markovian jumping parameters. The considered systems are not necessarily assumed to be regular and impulse-free. In terms of the linear matrix inequality (LMI) approach, a delay-dependent stochastic admissibility criterion is given to ensure that the nominal system is regular, impulse-free and stochastically stable. Based on this criterion, the problem is solved. A numerical example is provided to demonstrate the efficiency of the proposed methods in this paper. This work is supported by the National “863” Key Program of China (2008AA042902), the National Natural Science Foundation of China (60874113), the Doctor Base Foundation of Colleges and Universities by the Ministry of Education of China (200802550007) and the Key Scientific Research and Innovation Program of Shanghai Education Committee (09zz66).     

Crystallization of μc-Si on plastic substrate by using a pulsed double-frequency YAG laser

Thin film transistors （TFTs） of microcrystalline silicon （μc-Si） can provide higher mobility and stability than that of a-Si and better uniformity than that of poly-Si TFTs, and it would be more suitable to be applied to larger-area AMOLEDs. By using 2coYAG laser ann. ealing, crystalline μc-Si thin film on plastic substrate has been investigated and the proper laser energy needed for crystallization has been indicated. It has been found that the dehydrogenation process at 300-450℃ for a few of hours could be omitted by decreasing the H content in the crystallization precursor, which is suitable for laser crystallization on plastic substrates. The crystalline volume fraction （Xc） and the grain size of the resulted μc-Si could be adjusted by controlling the laser energy. By this method, the μc-Si on plastic substrate with Xc and grain size is respectively 85% （at the maximum） and 50 nm.     

A novel highly negative dispersion photonic crystal fiber

Based on the full-vector finite element method,a novel structure of highly negative dispersion photonic crystal fiber with the central index dip in the low germanium doped core is proposed.The highly negative dispersion can be obtained at the wavelength of 1.55 μm by adjusting the pitch,the air-hole diameter in the third ring,the germanium doped concentration and the influence of central index dip.     

The nonlinear optical properties of P3HT under picosecond laser irradiation

The nonlinear optical properties of P3HT in orthodichlorobenzene were investigated by Z-scan technique using second harmonic generation(532 nm) of mode-locked Nd:YAG laser in the picosecond domain. The experimental results show the magnitude of their nonlinear refraction indices was up to the order of 10^-11 esu. The reverse saturable absorption of P3HT solution was observed and their nonlinear absorption coefficients reach up to 3.4 cm/GW. The strong optical nonlinearity of P3HT may find its new application in the photoclectric field.     

A method of simulating intensity modulation-direct detection WDM systems

In the simulation of Intensity Modulation-Direct Detection WDM Systems,when the dispersion and nonlinear effects play equally important roles,the intensity fluctuation caused by cross-phase modulation may be overestimated as a result of the improper step size. Therefore,the step size in numerical simulation should be selected to suppress false XPM intensity modulation （keep it much less than signal power）. According to this criterion, the step size is variable along the fiber. For a WDM system,the step size depends on the channel separation. Different type of transmission fiber has different step size. In the split-step Fourier method,this criterion can reduce simulation time,and when the step size is bigger than 100 meters,the simulation accuracy can also be improved.     

Robust H ∞ Filtering for 2-D Systems with Intermittent Measurements

This paper is concerned with the problem of robust H _∞ filtering for uncertain two-dimensional (2-D) systems with intermittent measurements. The parameter uncertainty is assumed to be of polytopic type, and the measurements transmission is assumed to be imperfect, which is modeled by a stochastic variable satisfying the Bernoulli random binary distribution. Our attention is focused on the design of an H _∞ filter such that the filtering error system is stochastically stable and preserves a guaranteed H _∞ performance. This problem is solved in the parameter-dependent framework, which is much less conservative than the quadratic approach. By introducing some slack matrix variables, the coupling between the positive definite matrices and the system matrices is eliminated, which greatly facilitates the filter design procedure. The corresponding results are established in terms of linear matrix inequalities, which can be easily tested by using standard numerical software. An example is provided to show the effectiveness of the proposed approach. This work was partially supported by the National Natural Science Fundation of China under Grant 60504008 and 60825303, by the Research Fund for the Doctoral Program of Higher Education of China under Grant 20070213084, and by the Fok Ying Tung Education Foundation (111064).     

A neural-based nonlinear L 1-norm optimization algorithm for diagnosis of networks

Based on exact penalty function, a new neural network for solving the L ₁-norm optimization problem is proposed. In comparison with Kennedy and Chua’s network(1988), it has better properties.Based on Bandler’s fault location method(1982), a new nonlinearly constrained L ₁-norm problem is developed. It can be solved with less computing time through only one optimization processing. The proposed neural network can be used to solve the analog diagnosis L ₁ problem. The validity of the proposed neural networks and the fault location L ₁ method are illustrated by extensive computer simulations. Supported by Doctoral Special Fund of State Education Commission and the National Natural Science Foundation of China, Grant No.59477001 and No.59707002     

Analysis of electro-optic switches with series-coupled multiple microring resonators

In terms of the coupled mode theory, microring resonance and electro-optic modulation princeple, a reasonable project is proposed for designing an electro-optic switch with the series-coupled multiple microring resonators. The simulation and optimization are performed at the resonant wavelength of 1550 nm. The results are as follows: the core size of the microring is 1.6 μm×1.6 μm, the confined layer between the core and the electrode is 1.6 μm, the thickness of the electrode is 0.15 μm, the radius of the m...     

Fluorescence enhancement of single-phase red-blue emitting Ba3MgSi2O8:Eu2+,Mn2+ phosphors via Dy3+ addition for plant cultivation

Fluorescence enhancement of red and blue concurrently emitting Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺ phosphors for plant cultivation has been investigated by Dy³⁺ addition. The Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺,Dy³⁺(BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm. The two emission bands are coincident with the absorption spectrum for photosynthesis of plants. An obvious enhancement effect has been observed upon addition of Dy³⁺ with amount of 0.03 mol%, in which the intensities of both blue and red bands reach a maximum. The origin of red and blue emission bands is analysed. The photochromic parameters of the samples at the nearly UV excitation are tested. This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation. This work has been supported by National Natural Science Foundation of China (Grant No 50872091) and the Natural Science Foundation of Tianjin, China (06YFJMJC02300, 06TXTJJC14602).