In order to find problems like leakage and burst which are commonly seen in urban water distribution networks,pressure monitoring points need to be disposed.The pressure monitoring point placement is often based on similar degree of the node pressure data in the current stage.A method of optimal pressure monitoring point location was proposed in this paper because of the above method did not consider spatial properties of network node.The node coordinate,influence and the standard deviation of pressure were selected to establish the node characteristic matrix.The node characteristic matrix was clustered by using DBSCAN (density-based spatial clustering of applications with noise) and the number and location of pressure monitoring point was determined according to clustering result.The experimental results showed that the method ensured that the nodes belonging to the same cluster were connected effectively and the selected pressure monitoring points were uniform in water distribution networks,laying a solid foundation for the pressure monitoring point placement in the actual pipe network.
Remote sensing images obtained by satellite sensors are often covered with noise of clouds which result from the impact of climate.A thin cloud removal algorithm based on dual-tree complex wavelet transform was proposed in this paper.Remote sensing image covered with clouds was decomposed into high and low frequency components by using this transformation firstly.Then the high frequency components were compensated and the low frequency components were suppressed.The thin cloud on remote sensing image was effectively removed and the ground information in the cloud covered areas was recovered.Experiment results showed that,due to the performances of approximate translation invariance and good directional selectivity of dual-tree complex wavelet transform,the algorithm proposed in this paper was superior to the commonly used algorithms for thin cloud removal,and it could effectively restore ground information in the cloud covered areas.
In this paper,mesoporous NiWO_4 nanospheres with chestnut-like shapes were synthesized by hydrothermal method without any additives at a relatively low temperature.The structure was characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and the morphology was detected with scanning electron microscopy(SEM).The possible formation mechanism was discussed on the basis of the morphologies of NiWO_4 at different time intervals.In addition,it has been found that the morphology of NiWO_4 was dependent upon the reaction temperature to some extent.Owing to its unique mesoporous structure and large specific surface area,the NiWO_4 nanospheres exhibit a superior removal rate for anionic dyes compared with activated carbon.Importantly,mesoporous chestnut-like NiWO_4 nanospheres could preserve higher adsorption activity even after being recycled four times,suggesting it is a promising adsorbent in water treatment.
Independent component analysis(ICA)has been applied to the analysis of functional magnetic resonance imaging(fMRI)data.Although it holds the promise of being a data-driven analysis,we should determine the number of independent components prior to performing ICA.Accurate estimation of the number of independent components in fMRI data is critical to reduce overfitting or underfitting.Several approaches based on information theoretic criteria(ITC)have been implemented in widely used ICA,but they often perform overfitting.In this paper,a new method for estimating the number of sources in fMRI data based on the efficient detection criterion(EDC)was presented.Results of the simulated data showed that the EDC had strong robustness to different smoothed data.Moreover,the EDC was applied to the real fMRI data.Results of the real fMRI data showed that the method could alleviate the overestimation in fMRI data with the colored noise,and the EDC performed better in estimating the number of independent components in fMRI data.
Well-dispersed uniform hard magnetic CoFe_2O_4 nanoparticles were synthesized by thermal decomposition of a metal-organic salt.Then they were reduced in H_2 ambient at low temperature to prepare hard CoFe_2O_4/soft CoFe_2 composites in order to weaken as possibly the agglomeration.The improved magnetic performances were obtained in this work:a higher remanence to saturation magnetization ratio Mr/Msvalue of 0.64 was obtained;with increasing the reducing time the Msvalue greatly increases to 124emu·g~(-1) with the smaller loss of coercivity Hc.Through analysis it could be suggested that the Hcand Mr/Msvalues could be effectively improved by decreasing the strength of the dipolar interaction.
For the shortcoming that C-OWGA operator can only assemble single interval data,this paper proposed a new class of continuous interval data assembled operator. We constructed an IGOWC-OWGA operator by introducing IGOWA operator on the basis of the C-OWGA operator,then we selected vectorial angle cosine as a correlation index and built a new type of continuous interval combination forecasting model.Finally,it is shown that the new method had a significant effect in improving forecasting accuracy by an illustrative example.
VO_2(A)nanorods were facilely synthesized by using V_2O_5 and oxalic acid as the starting materials via a hydrothermal method.The initial molar ratio of V_2O_5 to oxalic acid and reaction time were changed to obtain the pure VO_2(A)phase. The elemental composition,microstructures and optical properties of as-obtained VO_2 samples were characterized using X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),scanning electron microscope(SEM),differential scanning calorimetry(DSC)and Fourier transform infrared spectrometer(FT-IR).It was found that the optimal synthesis condition of VO_2(A)is hydrothermal process at 230 ℃ for 24 hwith a 1∶1.5molar ratio of V_2O_5/oxalic acid.Combining the XRD patterns and SEM images,a transformation,assembly,recrystallization process was proposed to explain the formation process of VO_2(A)nanorods.
Interference energy detection is the foundation for the algorithm of interference suppression.General energy detection algorithm is simple and easy to be implemented,but the performance is easily influenced by the uncertainty of the background noise.An adaptive frequency domain energy detection algorithm which was based on frequency domain interference suppression algorithm model was presented in this paper.This algorithm set the threshold of signal through estimating the background noise power,adjusted the reference value adaptively based on the processed signal power.The simulation results showed that this algorithm could effectively eliminate the influence of the uncertain background noise.The performance of detection was much better than general energy detection algorithm extremely under narrowband interference condition.
With the wide application of fractional differential system theory in the field of physics,control,etc.,fractional degenerate differential equations have become an important topic in the field of the fractional differential equation.In this paper,the transformation problem and the explicit representation of solution were considered for fractional degradation delay differential equations with non-square matrix.By using the generalized inverse matrix theory,sufficient and necessary conditions that guarantee the general fractional degenerate differential equation with delay were normalized.By combining the fractional Laplace transform method,the explicit representation of solution was derived for fractional degenerate(delay)differential equations.The results generalized the corresponding results of the relevant literature.
Projector calibration is one of the key technologies in computer vision.This paper presented a calibration method of projector based on the positional relationship between the camera and projector. The method established the relation which was one to one correspondence of pixels between the image of the camera and projector image.The projector calibration was completed when getting homography between the projected image and the camera image by a series of operations to the captured image such as background subtraction,feature points extraction and so on.The method was simple and the experimental results indicated the method was practical,since the back projection error was between 0.3to 1pixel units.
Magnetic mesoporous silica nanoparticles(MMSNs)were prepared via a simple solgel process with tetraethyl orthosilicate as raw material and Fe3O4 nanoparticles as core.Then chitosan was modified to the magnetic mesoporous silica nanoparticles through the interaction between the carboxyl on magnetic mesoporous silica nanoparticles and the amino of chitosan(CS)to get chitosan coated magnetic mesoporous silica nanoparticles(MMSNs/CS).Fourier transform infrared(FT-IR),X-ray diffraction(XRD),transmission electron microscopy(TEM),thermo-gravimetric analysis(TGA)were used to characterize the nanoparticles.The result showed that chitosan was coated on the surface of the magnetic mesoporous silica nanoparticles and the size of mesoporous silica was 20 nm while chitosan's was 10 nm and the obtained MMSN/Cs had well magnetic responsiveness.
According to the change rule of typical daily load curve in distribution network,two operation modes of weighted largest load and weighted least load were selected.Making the minimum of reverse trend number and network loss,the best of improving distribution network voltage is objective function,combining with the type of the distributed generation and operation characteristics,the distributed generation of the optimal access point and optimal capacity were confirmed.Simulation results showed that through the introduction of distributed generation of rationally,the stability of distribution network was improved,the network loss was reduced,and economic efficiency was improved.
The magnetic and pH-responsive hydrogels of poly(hydroxypropylcellulose acrylate-co-crylic acid)composited with Fe_3O_4(P(HPCA-co-AA)@Fe_3O_4)were prepared by precipitation polymerization and in situ coprecipitation.Effects of different mole ratios of hydroxy(—OH)/acryloyl chloride(AC)and reaction time on the degree of acetyl grafted on hydroxypropylcellulose(HPC) were investigated.The structure of the products was confirmed using FT-IR and ~1H-NMR.The release behavior of the hydrogels at different pH values was studied,using sodium salicylate as a model drug.The results revealed that the higher pH value triggered more accumulative drug release,resulting from the swelling of the hydrogels.
The electrochemiluminescence(ECL)behavior of luminol on bare glass carbon electrode was studied by cyclic voltammetry,systematically.The effect factors on the ECL property of luminol were examined and the possible ECL mechanism was explored by a series of experiments.It is found that the intensity and stability of luminol ECL emission could be boosted by regulating potential scan range conveniently.Based on strong and stable ECL emission of luminol on bare glass carbon electrode in optimized potential scan range,a very simple ECL analysis method for copper metal ions and dopamine was developed,and the satisfactory detection results were obtained.
Oscillating chemical reaction,a vivid example of nonlinear equilibrium,supplied us with new analytical method by using analyte perturbation technology.This review covers recent development in utilization of oscillating chemical reaction in analytical chemistry in fourteen yeas.The methods being evaluated focus on the exterminating the metal ions,anions,gas or various organic compounds by using Belousov-Zhabotinsky(B-Z)oscillation system,copper-catalyzed oscillation system and Briggs-Rauscher(B-R)oscillation system.The methods have many advantages,such as low cost,easy operation,simple apparatus,wide linear determination range and lower determination limit.
The nonlinear beam equations represent the viberation of the rode bed in downward direction .Based on the existence of global attractors in other article ,this paper proved that semigroup S(t) generated by a class of nonlinear beam equation was uniformly differentiable on the global attractor Α.The paper also proved that global attractors of this class of equation have limited fractal dimension .Furthermore ,an estimate was given with the application of Sobolev‐Lieb‐Thirring inequality and upper bound of fractal dimension of the global attractor is obtained .
The one‐dimensional LaxY1‐xF3 nanotube and nanowire arrays were synthesized with Ln(NO3 )3 (Ln=La ,Y ,Eu)and NaF solution via anodic aluminum oxide (AAO) template . The structure ,composition and morphology of LaxY1‐xF3 nanotube arrays were characterized using XRD ,EDS ,SEM and TEM ,respectively .The fluorescence properties of Lax Y1‐x F3 :Eu3+ nanotubes were also investigated by fluorescence spectrophotometer ,and the results indicated that there were two typical linear emission peaks near 593 nm (5D0 → 7 F1 ) and 711 nm (5D0 → 7F4 ) ,respectively .The emission intensities of the samples increased with the increase of the mole fraction of Eu3+ ion .When the doping Eu3+ ion was 6% in mole ratio , the luminescence intensity of LaxY1‐xF3 :Eu3+ nanotubes was the maximum .
Using cellular automata model ,the authors here explored the effect of predator pursuit and prey evasion on the coexistence of intraguild predation system . The results showed that predator pursuit could promote the species coexistence ,but prey evasion will enhance coexistence with the condition that the intraguild predator has overall advantage or weak trade‐off between competition and predation .Species coexistence became more difficult by prey evasion w hen prey has overall advantage or strong trade‐off . Furthermore , the predator pursuit was shown to pose a much stronger impact than prey evasion on species coexistence and densities of populations .
Bis [3-(dimethylamino)propyl]isophthalamide was synthesized by using isophthaloyl dichloride and 3-dimethylaminopropylamine. Then,three series of amide cationic Gemini surfactants, namely C12-N-C12,C14-N-C14 and C16-N-C16, were synthesized by reacting bis [3-(dimethylamino)propyl] with 1-bromododecane,1-bromotetradecane and 1-bro mohexadecane,respectively. The chemical structures of products were confirmed by IR,1 H-NMR and elemental analysis.The CMC were 5.96×10-4,1.03×10-4,6.25×10-5 mol·L-1,theγCMCwere 40.83,38.76,38.08 mN·m-1,and the Krafft point were 0, 0,12 ℃,respectively.The forming and emulsifying property of surfactant were also studied.
The proportional-resonant(PR)control strategies of three-phase inverter with LC output filter were analyzed under the grid-connected and off-grid operating mode.In the off-grid operating mode,self-oscillation might occur in the system with inductive load.In view of the problem,a novel PR control strategy combined with inertia compensation was proposed.This method would improve dynamic performance and eliminate self-oscillation of the system by adding a first order inertial unit in the feedback loop.The simulation results showed that the control strategy in the off-grid mode could make inverter with good static and dynamic performance,and realized zero steady-state error control of the Sine AC instruction.
