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Distributed power networks have a large number of photovoltaic power sources. The bidirection of power flow, different transient control strategies, and installation locations make the transient characteristics highly complex and unpredictable. The vast network of the distribution system makes it almost impossible to predict the electrical quantities of each branch. Reasonable aggregation modeling of the distribution network can greatly simplify the network topology, facilitating transient control and the setting of relay protection settings. An aggregated equivalent modeling method based on the LSTM neural network for distributed PV fault external characteristics is proposed. This method equates the complex distribution network to a highly nonlinear but controllable current source. The method can output the I–V curves of equivalent PV system parallel points under any output power and is able to predict the fault characteristics of the equivalent system after a voltage drop at the parallel point. Compared to traditional mechanistic modeling, this method does not require specific modeling of complex physical systems and is able to accurately map the strong nonlinear inputs and outputs of distribution networks. The established LSTM model first uses a one-dimensional convolutional layer for feature extraction of the PV power coefficients (input), and then two hidden layers are utilized to process the sequence data; the vectors are mapped into a sequence of external characteristic curves (output) in a fully connected layer. A typical distribution network is built based on the traditional PV power model, and a large number of different output combinations are selected for simulation to provide an effective training set and validation set data for LSTM model training. By using the training set data, the weights and offset coefficients of each layer of the LSTM are continuously optimized until the model with the smallest overall error is obtained, which is the optimal model. Finally, the optimal model is utilized to establish an equivalent distribution network system, different degrees of voltage drops are set up at the grid-connected points, the fault characteristics are compared with those of the complete model, and the simulation results can prove the reliability and practicality of the proposed method. [ABSTRACT FROM AUTHOR]

The dual drive sliding feed system can obtain a uniform and stable resolution at extremely low speeds and significantly reduce the system's nonlinear friction. However, the numerous thermal sources within the system and the multipoint sliding contact during transmission result in a significant temperature rise, leading to considerable thermal deformation and errors. Moreover, the responsive mechanism of the thermal characteristics needs to be clarified. Therefore, firstly, a frictional torque model of the engagement of the screw and nut is established, and the heat generation, heat transfer, and thermal contact resistance (TCR) are solved. Then, based on the solution, a finite element thermal simulation model of the dual drive sliding feed system is established, and experiments are performed for validation. The results show that the error in temperature at the measuring point is less than 2.1 °C, and the axial thermal elongation of the screw is less than 6.2 µm. Finally, the thermal characteristics of the feeding system under various operating conditions are analyzed. The results show that the established thermal simulated model can effectively describe the dynamic thermal characteristics of the dual drive sliding feed system during operation. The effects of the rotational speed and ambient temperature on the dynamic thermal characteristics of the dual drive sliding feed system are investigated separately. The temperature increase in each part of the screw during the operation is characterized. [ABSTRACT FROM AUTHOR]

In order to research the effect of the steel fiber volume and the rubber powder diameter on the mechanics performance of the layer steel fiber reinforced rubber concrete, the cube compression tests, splitting tensile tests and four-point bending tests are performed on steel fiber reinforced rubber concrete with steel fiber content of 0.5%, 1%, 1.5%, 2%, 2.5% and rubber powder mesh 20, 40, 60. When 40 mesh rubber powder is added and the volume ratio of steel fiber is 1.5%, the compressive strength of laminated steel fiber rubber concrete reaches the peak value. The splitting tensile strength of laminated steel fiber rubber concrete mixed with2.0% steel fiber and mesh 40 rubber powder is the best. The flexural strength of laminated steel fiber rubber concrete mixed with 2.5% steel fiber and mesh 40 rubber powder is highest in this paper.

The task personalized recommendation problems in software crowdsourcing systems have unique characteristics, i.e., large task flow, high task complexity, long development cycle, winning task competitions, professional ability requirements, etc. However, existing software crowdsourcing recommendation mechanisms do not consider the contextual information of crowdsourcing tasks. In particular, the effects of crowdsourcing workers' interest changes and capability constraints on task selection are usually ignored. Therefore, this study proposes a new worker capability-correction long- and short-term attention network (CLSAN) recommendation framework. Firstly, explicit and implicit features are obtained from the feature data of crowdsourcing workers and historical crowdsourcing tasks. The long-term and short-term feature layers are extracted by adding LSTM to the historical tasks; the attention weight of user preference is calculated by integrating the attention mechanism to obtain each user's personalized preference. Secondly, this study considers that the capabilities of the worker need to be matched with the skills required for the software task. We design a worker capability correction model that uses Word2Vec software to obtain competency similarities between crowdsourcing workers and tasks, thereby determining the priority of tasks that satisfy the worker's capability. The experimental results show that CLSAN can accurately evaluate the changes of interest preferences of crowdsourcing workers, and effectively improve the quality and efficiency of crowdsourcing recommendations. [ABSTRACT FROM AUTHOR]

Ultra-precise actuation at extremely low speeds over a broad range is a major challenge for advanced manufacturing. A novel two-axis differential micro-feed system (TDMS) has been proposed recently to overcome the low-speed crawling of the worktable. However, due to the diversity of the force states of the TDMS, the methods for identification identifyingof friction parameters traditionally (like the all -components identification method, ACIM) didn't did not perform well. And many studies on the performance of the pre-sliding phase of the TDMS are missing. Therefore, a novel whole-system identification method (WSIM) based on the TDMS was proposed in this paper to precisely identify the friction parameters under different states of motion. The generalized Maxwell sliding (GMS) friction model was also applied to improve the accurate description of the pre-sliding. A novel corrected Stribeck curve based on the TDMS (TDMSSC) was proposed under the uniqueness of the TDMS structure. Control experiments showedn that the WSIM has higher precision and stability rather thancompared torather than the ACIM, and the correction of the Stribeck curve for the TDMS makes a contribution to the performance. This method significantly improves the accuracy and stability of the machine tool drive system. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are 20- to 24-nucleotide small RNAs, and whenever a pri-miRNA precursor includes another miRNA precursor, and both of these precursors may generate independent non overlapping mature miRNAs, we called them nested miRNAs. However, the functional and regulatory roles of nested miRNA structures in plants are still unknown. In this study, the Arabidopsis nested miR159a structure, which consists of two nested miRNAs, miR159a.1, and miR159a.2, was used as a model to determine miRNA-mediated gene silencing in plants. Complementation analysis of nested miR159a structures revealed that the miR159a structure can differentially complement the mir159ab phenotype, and a duplex nested structure in the tail end region of the pre-miR159a fold back may have a possible dominant function, indicating the importance of the flanking sequence of the stem in the cleavage of the mature miRNA. Furthermore, continuously higher expression of the miR159a.2 duplex in the severe leaf curl phenotype indicates that miR159a.2 is functional in Arabidopsis and suggests that in plants, a miRNA precursor may encode multiple regulatory small RNAs. Taken together, our study demonstrates that the nested miR159a structure regulated by duplex mutations of miR159a has a unique pattern and provides novel insight into silencing efficacy of Arabidopsis miR159a. [ABSTRACT FROM AUTHOR]

The conventional drive feed system inevitably enters the nonlinear creep region at very low speed. This seriously affects its low-speed performance and tracking accuracy. The new two-axis differential microfeed system (TDMS) can overcome the low-speed crawling and creep phenomenon caused by the inherent characteristics of the traditional electromechanical servo system structure. In this study, the dynamic model of TDMS is first established, and the LuGre friction model is improved according to its motion characteristics. The friction model of the screw nut whole assembly of TDMS is established. On this basis, two nonlinear observers are designed to estimate the internal state of the friction model, and the TDMS adaptive friction compensation controller is designed to estimate the uncertain parameters in TDMS through the parameter adaptive law. The global asymptotic stability of the TDMS controller is proved by Lyapunov theorem. Finally, the experimental verification is carried out by using dSPACE system. The results showed that the proposed TDMS adaptive friction compensation controller has good control accuracy. And it can effectively compensate the friction torque of lead screw nut differential drive. Compared with the application of traditional PID controller in TDMS, the tracking accuracy is improved by an order of magnitude. [ABSTRACT FROM AUTHOR]

Forum comments are valuable information for enterprises to discover public preferences and market trends. However, extensive marketing and malicious attack behaviors in forums are always an obstacle for enterprises to make effective use of this information. And these forum spammers are constantly updating technology to prevent detection. Therefore, how to accurately recognize forum spammers has become an important issue. Aiming to accurately recognize forum spammers, this paper changes the research target from understanding abnormal reviews and the suspicious relationship among forum spammers to discover how they must behave (follow or be followed) to achieve their monetary goals. First, we classify forum spammers into automated forum spammers and marketing forum spammers based on different behavioral features. Then, we propose a support vector machine-based automated spammer recognition (ASR) model and a k-means clustering-based marketing spammer recognition (MSR) model. The experimental results on the real-world labelled dataset illustrate the effectiveness of our methods on classification spammer from common users. To the best of our knowledge, this work is among the first to construct behavior-driven recognition models according to the different behavioral patterns of forum spammers. [ABSTRACT FROM AUTHOR]

Charge welds occur in profiles during billet-to-billet extrusion of hollow aluminum profiles. To investigate the effects of charge welds on the tensile property of the profile, a tensile test and a fracture scanning test using the scanning electron microscope (SEM) are conducted. The results showed that charge weld plays bad roles in the tensile property of the profile. The tensile samples derived from the charge weld distribution zone are always fractured near the charge welds. In addition, the tensile strengths of the early-stage charge welds are the poorest. To validate the property variations in the charge weld zone along the extrusion directions in a microscale, the evolution of microstructure characteristics and texture in the charge weld distribution zone are discussed with the help of the electron back scattering diffraction (EBSD). The grain morphologies, misorientation, and micro-textures are not uniform along the charge weld in the extrusion direction or on different sides of itself. Incomplete dynamic recrystallization with lower distortion energy and dislocation density due to lack of frictions with dies at the beginning and middle stages of the charge weld results in strip-shaped coarse grains and lower-angle grain boundaries, further revealing the essence of the low tensile strength at the beginning and in the middle of the charge weld. The intensity of shear texture {111}<112> on the charge weld is the largest compared with those on both sides of it, verifying the large plane strain status on the charge weld plane. [ABSTRACT FROM AUTHOR]

Preeclampsia (PE) is one of the leading causes of maternal and perinatal mortality and morbidity. One of the main hallmarks observed in PE is impaired inflammation state. In the current study, we found that miR-125b was deregulated in placental tissues and plasma derived from PE patients, which suggest a potential association between this miRNA and the pathogenesis of PE. Overexpression of miR-125b significantly reduced SGPL1 expression, and luciferase assays confirmed that SGPL1 is a direct target of miR-125b. We also found that miR-125b enhanced IL-8 production by directly targeting sphingosine-1-phosphate lyase 1 (SGPL1), and this effect could be reversed by SGPL1 overexpression. In placentas derived from PE patients, a negative correlation of miR-125b and SGPL1 was observed, and IL-8 was validated to be increased in the circulation of PE patients. Our data demonstrated a critical role of miR-125b in IL-8 production and the development of PE. [ABSTRACT FROM AUTHOR]

Hollow microcapsules, composed of pH responsive polyelectrolytes via a layer-by-layer (LBL) adsorption technique, were prepared. Linear or star-shaped poly(glycerol metha crylate)s (PGOHMAs) modified with 1,4-butanediamine and 1,2-ethanediamine (EDA) were synthesized and used as polycations. Poly(acrylic acid) was employed as polyanion and SiO2 (about 170 nm) as template. After LBL absorption, SiO2 cores were removed by HF treatment. The particle size and zeta potential were measured by dynamic light scattering, showing that the diameter of star-shaped amino-PGOHMA was larger than linear counterpart. The LBL assembly and core-etching process were evidenced by scanning electron microscope, transmission electron microscope, and energy dispersive spectrometer. The cytotoxicity experiments on human umbilical vein endothelial cells were carried out to evaluate the toxicity of LBL assembly. The star-shaped and EDA-modified PGOHMA exhibited better cell viability. The microcapsules were then used to load an anticancer drug, doxorubicin hydrochloride. High loading capacity (about 42%) and entrapment efficiency (84%) were obtained for star-shaped polymer-based microcapsules. The cumulative release rate was evaluated in vitro, showing faster release at an acidic condition compared to neutral pH. Confocal laser scanning microscopy evidenced the successful cellular uptake of DOX-loaded microparticles. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. [ABSTRACT FROM AUTHOR]

Abstract: (Ti,Nb)2AlC/Al2O3 in-situ solid solution composites were successfully synthesized from the elemental powder mixtures of Nb2O5, Ti, Al and carbon black using hot-press-aided reaction synthesis. The reaction path was investigated by differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), and a possible reaction mechanism was proposed to explain the formation of (Ti,Nb)2AlC/Al2O3 composites in which the thermite reaction between Al and Nb2O5 formed Al2O3 and Nb, and the latter together with TiAl and TiC reacted to form (Ti,Nb)2AlC. The synthesized composites show plate-like grains packed in a laminated structure typical of Ti2AlC, and the fine Al2O3 particles formed in-situ tend to disperse on the matrix grain boundaries. Compared with the monolithic Ti2AlC synthesized using an identical process, the Vickers hardness, maximum compressive stress, flexural strength and fracture toughness of (Ti0.96,Nb0.04)2AlC/5wt% Al2O3 were enhanced by 33.8%, 12.1%, 118.4% and 111.8%, respectively. The mechanisms by which Al2O3 increases the strength and toughness of the material were also discussed. [Copyright &y& Elsevier]

Abstract The driving patterns of the electric vehicles describe how users use their vehicles, reflecting the users' habits. These patterns have a positive effect on vehicle energy consumption. In this paper, a two-level clustering model is proposed to determine the driving patterns of electric vehicles. Firstly, the driving pattern characteristics are extracted from the data set of the electric vehicles. Then, the driving patterns including daily driving patterns and multifaceted driving patterns are obtained by a two-level clustering model. The data of 1463 electric vehicles in China were collected from September 1, 2015, to September 1, 2016. Using the proposed model, we obtain five types of daily driving patterns and four types of multifaceted driving patterns. Then, the features of clusters are extracted, and the geographical distribution analysis of the multifaceted driving patterns is conducted. The experimental results reveal that there are many driving patterns of the electric vehicles. Moreover, the effectiveness of the clustering models is verified by the experiments. The customer segmentation based on the driving patterns of electric vehicles is of a great significance for the development of personalized and targeted marketing strategies of vehicle manufacturers and energy efficiency improvement. [ABSTRACT FROM AUTHOR]

Abstract: Conjugated polymers (P1, P1L and P2–P5) constructed by alkynyl-substituted aniline and substituted arene analogs could be synthesized through Pd-catalyzed Sonogashira coupling. The responsive optical properties of poly(2-ethynyl aniline) (P1 and P1L for different molecular weights, P1L with longer chains on average) toward various metal ions (including Ni2+, Ag+, Cu2+, Zn2+, Fe3+, Fe2+, Mn2+, Na+, Ca2+, Pb2+, K+, Cr3+, Al3+, Cd2+, Pt2+, Au3+ and Tl3+) were investigated. Hg2+ exhibited the most pronounced fluorescence response of both P1 and P1L without interference from those coexistent ions due to aniline in the polymer backbone as the metal binding ligand, while other metal ions does not cause obvious change of fluorescence. Compared with P1, P1L exhibits better sensitivity toward Hg2+. Introducing pyridyl, thienyl or phenyl groups into the polymer backbone would weaken the quenching responses to Hg2+ compared with P1. The results indicated P1 and P1L could be used as a selective fluorescence sensor toward Hg2+. [Copyright &y& Elsevier]

Environmental friendly materials, K 6 SiW 11 O 39 Sn (SiWSn), was synthesized. SiWSn photocatalytic decomposition of C. I. Reactive Red 24 (RR24) with the UV-lamp (253.7 nm, 20 W), Xenon lamp filtered less than 390 nm light (500 W) and sun light was investigated. The results showed that RR24 solution could be effectively decolorized with the SiWSn photocatalyst. The photocatalytic degradation efficiency of RR24 with SiWSn was affected by the initial concentration of RR2 solution, the amount of SiWSn and the photolysis time. It is demonstrated that the process of photodegradation of RR24 with SiWSn is a pesudo first-order reaction, which can be described by Langmuir-Hinshelwood equation. Hydroxyl radicals and holes are both the main oxidants in the photocatalytic reaction of RR24 with SiWSn. [ABSTRACT FROM AUTHOR]