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Seed cotton compression molding solves the inconvenience of seed cotton transportation and storage after mechanical harvesting. Stress relaxation is closely related to the performance of the compressed seed cotton. In this study, an electronic universal testing machine with a homemade compression device was used to study the stress relaxation characteristics of machine-harvested seed cotton. The stress relaxation model of machine-harvested seed cotton was established, the influence of test factors on the response indexes was analyzed and, finally, stress relaxation characteristics of machine-harvested seed cotton were simulated. Results show that machine-harvested seed cotton stress relaxation characteristics can be described by the five-element Maxwell model. The equilibrium elastic modulus is negatively correlated with moisture content and cross-section dimensions, and the equilibrium elastic modulus is positively correlated with trash content and compression density. The rapid decay time and the residual stress ratio are negatively correlated with moisture content and compression density, but the influence of trash content and cross-section dimensions are limited. The stress relaxation process of machine-harvested seed cotton was simulated using virtual prototype technology, and the maximum error between the experimental and simulated values was obtained as 4.96%. The feasibility of the virtual prototype technique for the viscoelastic simulation of biomaterials was demonstrated.

A new piezoelectric cantilever energy harvester based on vortex-induced vibration was proposed. The influence of some parameters was by mathematical modeling, numerical simulation and experimental testing. The results showed that the voltage value increased with the increase of wind speed within the test range. When the bluff body was a cylinder with a diameter of 0.02 m, a height of 0.05 m, and the ratio of the distance between bluff body and harvester and bluff body diameter was 2, the maximum voltage of the T-type piezoelectric cantilever beam energy harvester was 1.02 V. It provided theoretical and experimental references for energy harvesting in the wind. [ABSTRACT FROM AUTHOR]

In this research article, a new mathematical model for the transmission dynamics of vector-borne diseases with vertical transmission and cure is developed. The non-negative solutions of the model are shown. To understand the dynamical behavior of the epidemic model, the theory of basic reproduction number is used. As this number increases, the disease invades the population and vice versa. The effect of vertical transmission and cure rate on the basic reproduction number is shown. The disease-free and endemic equilibria of the model are found and both their local and global stabilities are presented. Finally, numerical simulations are carried out graphically to show the dynamical behaviors. These results show that vertical transmission and cure have a valuable effect on the transmission dynamics of the disease. [ABSTRACT FROM AUTHOR]

This study examined the contributions of the tongue tip (TT), tongue body (TB), and tongue lateral (TL) sensors in the electromagnetic articulography (EMA) measurement of American English alveolar consonants. Thirteen adults produced /ɹ/, /l/, /z/, and /d/ in /ɑCɑ/ syllables while being recorded with an EMA system. According to statistical analysis of sensor movement and the results of a machine classification experiment, the TT sensor contributed most to consonant differences, followed by TB. The TL sensor played a complementary role, particularly for distinguishing /z/. [ABSTRACT FROM AUTHOR]

The spatial distribution of automatic weather stations in regions of western China (e.g., Tibet and southern Xingjiang) is relatively sparse. Due to the considerable spatial variability of precipitation, estimations of rainfall that are interpolated in these areas exhibit considerable uncertainty based on the current observational networks. In this paper, a new statistical method for estimating precipitation is introduced that integrates satellite products and in situ observation data. This method calculates the differences between raster data and point data based on the theory of data assimilation. In regions in which the spatial distribution of automatic weather stations is sparse, a nonparametric kernel-smoothing method is adopted to process the discontinuous data through correction and spatial interpolation. A comparative analysis of the fusion method based on the double-smoothing algorithm proposed here indicated that the method performed better than those used in previous studies based on the average deviation, root mean square error, and correlation coefficient values. Our results indicate that the proposed method is more rational and effective in terms of both the efficiency coefficient and the spatial distribution of the deviations. [ABSTRACT FROM AUTHOR]

In this work, we study the lift force on spherical nanoparticles suspended in a shear flow of rarefied binary gas mixtures. Analytical formulae are developed using the gas kinetic theory by considering non-rigid-body intermolecular interactions between the particle and gas molecules. It has been shown that the lift force formulae can be reduced to those in pure gases. It is also found that the direction of the lift force on nanoparticles in binary gas mixtures can be changed by varying the temperature, gas-particle interaction and/or gas concentrations. [ABSTRACT FROM AUTHOR]

An approximate algorithm combining P systems and active evolutionary algorithms (AEAPS) to solve traveling salesman problems (TSPs) is proposed in this paper. The novel algorithm uses the same membrane structure, subalgorithms and transporting mechanisms as Nishida's algorithm, but adopts two classes of active evolution operators and a good initial solution generating method. Computer experiments show that the AEAPS produces better solutions than Nishida's shrink membrane algorithm and similar solutions with an approximate optimization algorithm integrating P systems and ant colony optimization techniques (ACOPS) in solving TSPs. But the necessary number of iterations using AEAPS is less than both of them. [ABSTRACT FROM AUTHOR]

Meridian theory is one of the core components of the theory of traditional Chinese medicine (TCM). It gives an integral explanation for how human life works, how a disease forms, and how a therapy acts to treat a disease. If we do not understand the meridians, it is hard to understand the TCM. People in China and abroad had been working hard for 50 years, trying to understand the meridians; then 15 years ago a breakthrough idea appeared when we realized that they are low resistance fluid channels where various chemical and physical transports take place. The channel is called low hydraulic resistance channel (LHRC) and the chemical transport is named volume transmission (VT). This review aims to give a full understanding of the essence of meridian and its works on the therapies of TCM. [ABSTRACT FROM AUTHOR]

To meet the domestic demand of software autonomous scheduling, Xi'an Jiaotong University had developed MIDAC (a Module In-vessel degraded severe accident Analysis Code) which can not only analyze the processes of in-vessel severe accident, but also provide the related results of each one. This code was composed of five modules: the early behavior module, the core degradation module, the debris bed module, the melting materials IVR module and the connecting module. In this paper, the basic mathematic-physical models of those modules were briefly introduced. Then, the CPR1000 station blackout scenario severe accident was set as an example to calculate the primary system thermal-hydraulic transient, the core degradation and the debris behavior, as well as the creep rupture of heat structures in primary loop pressure boundary. At last, the accuracy of MIDAC was verified in partial comparison with SCDAP/RELAP5 in primary system thermal-hydraulic transient analyzing part. [ABSTRACT FROM AUTHOR]

We investigate the interacting new holographic dark energy (HDE) with viscosity. Specifically we not only study the dynamical evolutions of the new HDE with viscosity and the influences of viscosity as well as the coupling constant on the equation of state for the new HDE, but also establish the correspondence between the new HDE with viscosity and variable generalized Chaplygin gas (VGCG) models in the flat Friedmann—Robertson—Walker universe. Furthermore, we also reconstruct the potential and the dynamics of VGCG as the scalar field. By analysis we show that for the new holographic Chaplygin gas model, if the related parameters to the potential satisfy some constraints, the accelerated expansion can be achieved. These research results can reduce to the ones without viscosity. [ABSTRACT FROM AUTHOR]

In this paper we consider a subclass of strongly spirallike functions on the unit disk D in the complex plane C, namely, strongly almost spirallike functions of type β and order α.We obtain the growth results for strongly almost spirallike functions of type β and order α on the unit disk D in C by using subordination principles and the geometric properties of analytic mappings. Furthermore we get the growth theorems for strongly almost starlike functions of order α and strongly starlike functions on the unit disk D of C. These growth results follow the deviation results of these functions. [ABSTRACT FROM AUTHOR]

This paper presents the system modeling, control strategy design, and hardware-in-the-loop test for a series-parallel hybrid electric bus. First, the powertrain mathematical models and the system architecture were proposed. Then an adaptive ECMS is developed for the real-time control of a hybrid electric bus, which is investigated and verified in a hardware-in-the-loop simulation system. The ECMS through driving cycle recognition results in updating the equivalent charge and discharge coefficients and extracting optimized rules for real-time control. This method not only solves the problems of mode transition frequently and improves the fuel economy, but also simplifies the complexity of control strategy design and provides new design ideas for the energy management strategy and gear-shifting rules designed. Finally, the simulation results show that the proposed real-time A-ECMS can coordinate the overall hybrid electric powertrain to optimize fuel economy and sustain the battery SOC level. [ABSTRACT FROM AUTHOR]

We develop a random financial time series model of stock market by one of statistical physics systems, the stochastic contact interacting system. Contact process is a continuous time Markov process; one interpretation of this model is as a model for the spread of an infection, where the epidemic spreading mimics the interplay of local infections and recovery of individuals. From this financial model, we study the statistical behaviors of return time series, and the corresponding behaviors of returns for Shanghai Stock Exchange Composite Index (SSECI) and Hang Seng Index (HSI) are also comparatively studied. Further, we investigate the Zipf distribution and multifractal phenomenon of returns and price changes. Zipf analysis and MF-DFA analysis are applied to investigate the natures of fluctuations for the stock market. [ABSTRACT FROM AUTHOR]

Genetic regulatory networks are dynamic systems which describe the interactions among gene products (mRNAs and proteins). The internal states of a genetic regulatory network consist of the concentrations of mRNA and proteins involved in it, which are very helpful in understanding its dynamic behaviors. However, because of some limitations such as experiment techniques, not all internal states of genetic regulatory network can be effectively measured. Therefore it becomes an important issue to estimate the unmeasured states via the available measurements. In this study, we design a state observer to estimate the states of genetic regulatory networks with time delays from available measurements. Furthermore, based on linear matrix inequality (LMI) approach, a criterion is established to guarantee that the dynamic of estimation error is globally asymptotically stable. A gene repressillatory network is employed to illustrate the effectiveness of our design approach. [ABSTRACT FROM AUTHOR]

The hydraulic rolling shear whose hydraulic system is researched in this article is designed based on the theory of rolling shear. This article builds the transfer function of the unsymmetrical valve controlling unsymmetrical cylinder system and gets the expressions of the flow gain and the flow pressure coefficients and then compares them with the system controlled by symmetric valve. After the theoretical analysis, this article compares the control effects between the unsymmetrical valve and symmetric valve with the simulation software HYVOS. The simulation declares that when the unsymmetrical cylinder is controlled by the unsymmetrical valve, its control voltage is one-third of that controlled by the symmetric valve. Using unsymmetrical valve to control the unsymmetrical cylinder is perfect and meets the demands of the rolling shears as shown by the data collected from the field. [ABSTRACT FROM AUTHOR]

In view of the applications of artificial neural networks in economic and financial forecasting, a stochastic time strength function is introduced in the backpropagation neural networkmodel to predict the fluctuations of stock price changes. In thismodel, stochastic time strength function gives a weight for each historical datum and makes the model have the effect of random movement, and then we investigate and forecast the behavior of volatility degrees of returns for the Chinese stock market indexes and some global market indexes. The empirical research is performed in testing the prediction effect of SSE, SZSE, HSI, DJIA, IXIC, and S&P 500 with different selected volatility degrees in the established model. [ABSTRACT FROM AUTHOR]

Reconnection of the self-generated magnetic fields in laser-plasma interaction was first investigated experimentally by Nilson et al. [Phys. Rev. Lett. 97, 255001 (2006)] by shining two laser pulses a distance apart on a solid target layer. An elongated current sheet (CS) was observed in the plasma between the two laser spots. In order to more closely model magnetotail reconnection, here two side-by-side thin target layers, instead of a single one, are used. It is found that at one end of the elongated CS a fanlike electron outflow region including three well-collimated electron jets appears. The (> 1 MeV) tail of the jet energy distribution exhibits a power-law scaling. The enhanced electron acceleration is attributed to the intense inductive electric field in the narrow electron dominated reconnection region, as well as additional acceleration as they are trapped inside the rapidly moving plasmoid formed in and ejected from the CS. The ejection also induces a secondary CS. [ABSTRACT FROM AUTHOR]

The interacting impact between the crude oil prices and the stock market indices in China is investigated in the present paper, and the corresponding statistical behaviors are also analyzed. The database is based on the crude oil prices of Daqing and Shengli in the 7-year period from January 2003 to December 2009 and also on the indices of SHCI, SZCI, SZPI, and SINOPEC with the same time period. A jump stochastic time effective neural network model is introduced and applied to forecast the fluctuations of the time series for the crude oil prices and the stock indices, and we study the corresponding statistical properties by comparison. The experiment analysis shows that when the price fluctuation is small, the predictive values are close to the actual values, andwhen the price fluctuation is large, the predictive values deviate from the actual values to some degree. Moreover, the correlation properties are studied by the detrended fluctuation analysis, and the results illustrate that there are positive correlations both in the absolute returns of actual data and predictive data. [ABSTRACT FROM AUTHOR]

Abstract: Failure of transformer is very complex, dissolved Gas in Oil Analysis (DGA) is presently the easier and simpler way for fault diagnosis of oil-immersed transformers.The correct selection of features of dissolved gas data can improve efficiency of transformer fault diagnosis. SVM is more effective than traditional methematic model to discribe the type of fault of transformer.As for the problem of difficulty of determining parameters in SVM applications, genetic algorithm (GA) was used to select SVM parameters. The test results show that this GA-SVM model is effective to detect failure of transformer. [Copyright &y& Elsevier]

An inverse substructure method is developed for the analysis of the dynamical characteristics of a three-substructures coupled system based on the inverse substructure method of a two-substructures coupled system. The unknown substructure-level frequency response functions (FRFs) and coupling stiffness can be predicted, and the system-level response of key components can be obtained by using the method when the system-level FRFs needed are all measured. To verify the validity of the inverse substructure method of a three-substructures coupled system, a lumped mass-spring-damper model with three substructures coupled is taken as an example for numerical validation. The prediction is exactly the same as the ‘‘Given’’. To further check out the accuracy of the method, the experiment of a physical prototype is carried out, and the predicted substructure-level FRFs are in good agreement with those that are measured. The method is applied to the analysis of a product-transport-system, which is treated as a coupled system composed of a key component, a product and a vehicle. The effect of the coupling stiffness on the dynamic response of key components is investigated. The result indicates that reducing the coupling stiffness of the product-vehicle interface can largely lower the response of key components. [ABSTRACT FROM PUBLISHER]

A nonlinear time-varying (NLTV) dynamic model of a hypoid gear pair system with time-dependent mesh point, line-of-action vector, mesh stiffness, mesh damping, and backlash nonlinearity is formulated to analyze the transitional phase between nonlinear jump phenomenon and linear response. It is found that the classical jump discontinuity will occur if the dynamic mesh force exceeds the mean value of tooth mesh force. On the other hand, the propensity for the gear response to jump disappears when the dynamic mesh force is lower than the mean mesh force. Furthermore, the dynamic analysis is able to distinguish the specific tooth impact types from analyzing the behaviors of the dynamic mesh force. The proposed theory is general and also applicable to high-speed spur, helical and spiral bevel gears even though those types of gears are not the primary focus of this paper. [ABSTRACT FROM AUTHOR]

The statistical behaviors of two-layered random-phase interfaces in two-dimensional Widom-Rowlinson's model are investigated. The phase interfaces separate two coexisting phases of the lattice Widom- Rowlinson model; when the chemical potential µ of the model is large enough, the convergence of the probability distributions which describe the fluctuations of the phase interfaces is studied. In this paper, the backbones of interfaces are introduced in the model, and the corresponding polymer chains and cluster expansions are developed and analyzed for the polymer weights. And the existence of the free energy for two-layered random-phase interfaces of the two-dimensional Widom- Rowlinson model is given. [ABSTRACT FROM AUTHOR]

In this paper, we develop a new mathematical model for the mammalian circadian clock, which incorporates both transcriptional/translational feedback loops (TTFLs) and a cAMP-mediated feedback loop. The model shows that TTFLs and cAMP signalling cooperatively drive the circadian rhythms. It reproduces typical experimental observations with qualitative similarities, e.g. circadian oscillations in constant darkness and entrainment to light-dark cycles. In addition, it can explain the phenotypes of cAMP-mutant and Rev-erba[?]/[?]-mutant mice, and help us make an experimentally-testable prediction: oscillations may be rescued when arrhythmic mice with constitutively low concentrations of cAMP are crossed with Rev-erba[?]/[?] mutant mice. The model enhances our understanding of the mammalian circadian clockwork from the viewpoint of the entire cell. [ABSTRACT FROM AUTHOR]

Abstract: A coalmining city is a unique city economic type that relies on the exploitation and utilization of coalmine resources for its economic and social development. Under the restraint of coalmining resource reserve and the influence of exploitation of the resources, the development of a coalmining city generally undergoes four stages: the starting period, the growth period, the maturity period and the decline period. The development of coalmining resources, on the one hand, supports a coalmining city''s economic development and on the other hand, has some severe negative impact on its ecological environment, having great influences on the coalmining city''s sustainable development. By building up a Logistic dynamics model based on coalmining city growth and development track, this article simulates the different development periods of the cities. This indicates that when the development element base reaches zero, the contribution of coalmining to the city''s economic development reaches the threshold value of sustainable development. Furthermore, before the coalmining city enters into the decline period, it could actually establish a diversified industrial structure to avoid its dependence on one single industry so as to realize sustainable development. [Copyright &y& Elsevier]

This paper presents a novel recurrent neural network for solving a class of convex quadratic programming (QP) problems, in which the quadratic term in the objective function is the square of the Euclidean norm of the variable. This special structure leads to a set of simple optimality conditions for the problem, based on which the neural network model is formulated. Compared with existing neural networks for general convex QP, the new model is simpler in structure and easier to implement. The new model can be regarded as an improved version of the dual neural network in the literature. Based on the new model, a simple neural network capable of solving the κ-winners-take-all (κ-WTA) problem is formulated. The stability and global convergence of the proposed neural network is proved rigorously and substantiated by simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a robust modelling and control method for an active vehicle suspension fitted with a magneto-rheological (MR) damper, and evaluates the performance of the active suspension (AS) in a hardware-in-the-loop (HiL) platform. Firstly, mathematical models for a quarter vehicle including a nonlinear MR damper are given, and a linear piecewise function describing an inverse MR damper model is derived for an easy hardware implementation. Secondly, the uncertainty associated with the nonlinear MR damper and the HiL platform is recast into an input-type unstructured uncertainty, and the AS control problem is transformed into and solved by the H-infinity control method. Thirdly, the HiL platform is setup, where the vehicle is modelled in software, and the controller is implemented in a digital signal processor (DSP). Finally, the AS is assessed by MATLAB-based software simulations and DSP-based HiL ones. [ABSTRACT FROM AUTHOR]

This paper presents a novel idea on how to design an active suspension system to improve vehicle ride comfort and to actively tilt the vehicle inwards when it is subject to steering manoeuvres. Firstly, the motivations for active vehicle tilting via active suspensions are identified. Secondly, the mathematical models for the vehicle with active suspensions are built up and the link between active suspensions and vehicle roll characteristics is analysed. Thirdly, the control objectives of vehicle ride comfort and active tilting are incorporated into a standard robust-control framework and an H-infinity controller satisfying both objectives is designed. Finally, the integrated suspension control system is evaluated by computer simulations, in comparison to a passive suspension system and a traditional active one. The integrated control strategy not only improve vehicle ride comfort, but also actively tilt the vehicle inwards to act against vehicle steering manoeuvres. The active tilting reduces lateral acceleration experienced by passengers and reduces the possibility of vehicle rollover. [ABSTRACT FROM AUTHOR]

High-voltage p-channel 4H-SiC insulated gate bipolar transistors (IGBTs) have been fabricated and characterized. The devices have a forward voltage drop of 7.2 V at 100 A/cm² and a -16 V gate bias at 25 °C, corresponding to a specific on-resistance of 72 mΩ · cm² and a differential on-resistance of 26 mΩ · cm². Hole mobility of 12 cm² /V · sin the inversion channel with a threshold voltage of -6 V was achieved by optimizing the n+ well doping profile and gate oxidation process. A novel current enhancement layer was adopted to reduce the JFET resistance and enhance conductivity modulation by improving hole current spreading and suppressing the electron current conduction through the top n-p-n transistor. Inductive switching results have shown that the p-IGBT exhibited a turn-off time of ∼.1 μs and a turn-off energy loss of 12 mJ at 4-ky dc-link voltage and 6-A load current at 25 °C. The turn-off trajectory from the measured inductive load switching waveforms and numerical simulations shows that the p-IGBT had a near-square reverse bias safe operating area. Numerical simulations have been conducted to achieve an improved tradeoff between forward voltage drop and switching off energy by investigating the effects of drift layer lifetime and p-buffer layer parameters. The advantages of SiC p-IGBTs, such as the potential of very low ON-state resistance, slightly positive temperature coefficient, high switching speed, small switching losses, and large safe operating area, make them suitable and attractive for high-power high-frequency applications. [ABSTRACT FROM AUTHOR]

Abstract  Codon Adaptation Index (CAI), Effective Number of Codons $$(\hat{N_{c}})$$ as well as its modifications $$\hat{N_{c}}^*$$ , $$\hat{N_{c}}^{**}$$ can be used to measure gene codon bias. In this article, we prove $$\hat{N_{c}}^{**}$$ is more efficient and unbiased than $$\hat{N_{c}}^*$$ and $$\hat{N_{c}}$$ by revisiting correlations of them with CAI in the level of individual amino acid’s codon bias. Correlations are studied by mathematical expressions rather than statistic methods, because the latter unavoidably depend on the data set used. Additionally, the immediate cause of correlations of $$\hat{N_{i}}$$ with CAI (as well as those of RSCU with CAI) are also described in mathematical language. Perhaps, mathematics provides us a new way to study correlations between biological indexes. [ABSTRACT FROM AUTHOR]

In this paper, we postulate an algebraic model to explain how the symmetry of three lepton species plays its role in the Lorentz extension. Inspired by the two-to-one mapping between the SL(2,C) group and the Lorentz group, we design a mapping between the SL(3,C) group, which displays the family symmetry, and a generalized Lorentz group. Following the conventional method, we apply the mapping results to the Dirac equation to discuss its transformation invariance, and it turns out that only when the vertex matrix γμ is extended to the combination c1γμ+c2γ5γμ can the Dirac-equation form be reserved. At the same time, we find that the Lorentz group has to be extended with an additional generator γ5. The generalized vertex matrix is helpful in understanding the axial-like form of weak interaction and the neutrino oscillations. [ABSTRACT FROM AUTHOR]

This brief paper presents an M-matrix-based algebraic criterion for the global exponential stability of a class of recurrent neural networks with decreasing time-varying delays. The criterion improves some previous criteria based on M-matrix and is easy to be verified with the connection weights of the recurrent neural networks with decreasing time-varying delays. In addition, the rate of exponential convergence can be estimated via a simple computation based on the criterion herein. [ABSTRACT FROM AUTHOR]

Struvite precipitation has the potential for removing and recovering phosphorus from agricultural wastewater streams, such as concentrated animal feeding operations wastewater. However, impacts of anticipated component-ion molar ratios and potentially interfering ions are unknown as are the compounding pH relationship with respect to all potential complexes. This research experimentally investigates and mathematically models these factors. Emphasis is placed upon the composition of formed deposits and model validation with experimental data. Results show that calcium is a major interfering ion affecting the deposit composition, decreasing struvite purity. X-ray diffraction (XRD) and scanning electron microscopy + energy dispersive spectrometry were used to study the deposit structure and elemental composition. Results revealed that the precipitates formed at a pH of 8.7 have regular crystal shape, and XRD analysis confirmed that the precipitates are high-purity struvite. Higher pH (>10) leads to the formation of amorphous precipitate and decreases the struvite purity in the deposits. To maximize struvite purity, the ratio of Ca to P should be less than 0.5 and the pH near 8.7. [ABSTRACT FROM AUTHOR]

In this paper, we study a kind of 2–dimensional axi–symmetrical piston problem in compressible flow. The corresponding mathematical model is the well–known Euler system. With the Newton iteration procedure and energy estimate, we give the local existence of the shock front solution to this problem. [ABSTRACT FROM AUTHOR]

Focuses on an improved neural computation scheme for kinematic control of redundant manipulators based on infinity-norm joint velocity minimization. Problem formulation; Stability analysis; Simulation results.

Based on the modified Rytov theory and the international telecommunication union-radio (ITU-R) slant atmospheric structure constant model, the uniform scintillation index of partially coherent Gaussian—Schell model (GSM) beam propagation in the slant path is derived from weak- to strong-turbulence regions considering inner- and outer-scale effects. The effects of wavelength of beams and inner- and outer-scale of turbulence on scintillation are analyzed numerically. Comparison between the scintillation of GSM beams under the von Karman spectrum and that of beams under the modified Hill spectrum is made. The results obtained show that the scintillation index obtained under the von Karman spectrum is smaller than that under the modified Hill spectrum. This study can find theory bases for the experiments of the partially coherent GSM beam propagation through atmospheric turbulence. [ABSTRACT FROM AUTHOR]

A low-temperature GaN (LT-GaN) nucleation layer is grown on a patterned sapphire substrate (PSS) using metal-organic chemical vapor deposition (MOCVD). The surface morphology of the LT-GaN is investigated and the selective nucleation phenomenon in the growth process of the LT-GaN nucleation layer is discovered. Meanwhile, effects of thickness of the LT-GaN and the annealing process on the phenomenon are also discussed. A pattern model is also proposed to analyze the possible mechanisms in atomic scale. [ABSTRACT FROM AUTHOR]

The electronic band structures of periodic models for Si-H compounds are investigated by the density functional theory. Our results show that the Si-H compound changes from indirect-gap semiconductor to direct-gap semiconductor with the increase of H content. The density of states, the partial density of states and the atomic charge population are examined in detail to explore the origin of this phenomenon. It is found that the Si-Si bonds are affected by H atoms, which results in the electronic band transformation from indirect gap to direct gap. This is confirmed by the nearest neighbour semi-empirical tight-binding (TB) theory. [ABSTRACT FROM AUTHOR]

Abstract: In the design of a wind farm, the placement of turbines is an important factor that affects the efficiency and profit, but automatic placement of turbines is still a challenging problem. This study reveals the “submodular” property of the wind turbine positioning problem based on Jensen wake model. Based on this property, a “lazy greedy” algorithm is used to optimize the placement. This method can obtain solutions with theoretical guarantee of quality. It can also estimate the lower bound of the optimal value of the objective function. This method is tested on three types of wind scenarios. Compared to previous research, this algorithm takes much less time, and always gains a better solution. To enlarge the application scope, the wake model is extended to the large scale complex terrain in this study. The present algorithm and some other algorithms are tested in the simulation of the complex terrain. The experimental results demonstrate the present method’s superior performance. [Copyright &y& Elsevier]

The present study is focused on the construction of a well-performing pilot controlled proportional flow valve with internal displacement-flow feedback. A novel control strategy for the valve is proposed in which the flow rate through the valve is directly controlled. The linear mathematical model for the valve is established and a fuzzy proportional-integral-derivative (PID) controller is designed for the flow control. In order to obtain the flow rate used as feedback rapidly and accurately in real-time, back propagation neural network (BPNN) is employed to predict the flow rate through the valve with the pressure drop through the main orifice and main valve opening, and the predicted value is used as the feedback. Both simulation and experimental results show that the predicted value obtained by BPNN is reliable and available for the feedback. The proposed control strategy is effective with which the flow rate through the valve remains almost constant when the pressure drop through the main orifice increases and the valve can be applied to the conditions where the independence of flow rate and load is required. For the valve with the proposed control strategy, the nonlinearity is less than 5.3%, the hysteresis is less than 4.2%, and the bandwidth is about 16 Hz. The static and dynamic characteristics are reasonable and acceptable. [ABSTRACT FROM AUTHOR]

In rotor-bearing system, the misalignment can lead to secondary faults, such as the rub-impact fault. How the development of misalignment could affect the rub-impact force and other dynamic responses is important for the vibration control and fault diagnosis of rotor system. In this paper, a mathematical model of a two-shaft rotor-bearing- gear coupling system is established. The model is validated through the misaligned force of gear coupling, the supporting force of the lubricated ball bearing and the whole rotor response. To overcome the limit of traditional approaches and further dig out fault characteristics, the time-frequency method is introduced to analyze the dynamic response from both the time and frequency domains points of view. It is found the misalignment effect on rotor dynamic responses is mainly focused in high rotating speed range. The development of misalignment has an obvious adverse effect on the rotor stability. Some intermittent components in low frequency range due to the occurrence and development of misalignment can be found affecting the rotor stability at low speed range, and the high frequency rub-impact components can be found responsible for the unstable state of rotor. [ABSTRACT FROM AUTHOR]