The hot-drawing process of polyacrylonitrile (PAN) fibers is an important step during the production of PAN-based carbon fibers. In this study, supercritical carbon dioxide (Sc-CO₂) was used as one ...kind of media for thermal stretching of PAN fibers to study the effect of different pressures of Sc-CO₂ on crystallinity, degree of orientation and mechanical property of PAN fibers during the hot-drawing process. The changes of microstructure and mechanical properties in the PAN fibers were investigated by wide-angle X-ray diffraction, small angle X-ray scattering and monofilament strength analysis. The results showed that as the pressure increased, the crystallinity and degree of orientation of PAN fibers increased. Furthermore, when the pressure was 10 MPa, the crystallinity increased from 69.78% to 79.99%, which was the maximum crystallinity among the different pressures. However, when the pressure was further increased, the crystallinity and degree of orientation of the fibers were reduced. The test results of the mechanical properties were consistent with the trends of crystallinity and degree of orientation, showing that when the pressure was 10 MPa, the tensile strength of the fibers increased from 4.59 cN·dtex
to 7.06 cN·dtex
and the modulus increased from 101.54 cN·dtex
to 129.55 cN·dtex
.
DC transformer is the key equipment to interconnect the high voltage dc systems with different voltage levels and build dc grid. Compared with the dc/ac/dc converter based on modular multilevel ...converter, the non-isolated modular dc/dc converter (MDCC) offers lower cost and higher efficiency, due to the elimination of the ac transformer and reduced submodules (SMs). However, the MDCC based on the half bridge SM (HBSM) can not block the dc short fault. Therefore, the MDCC with the hybrid configuration of the unipolar full-bridge SM (UFBSM) and HBSM, which achieves the dc fault blocking capability, is analysed in this paper, and a damping resistor is introduced in the UFBSM to reduce the ascending voltage of the SM capacitor under dc fault. The fault blocking mechanism of the converter is described, and the fast recovery strategy is presented to ride through the temporary fault. In addition, the design principle of the converter is discussed through a study case. Finally, the simulation performed in Matlab/Simulink verifies the theoretical analysis.
Water evaporation is a ubiquitous natural process that harvests thermal energy from the ambient environment. It has previously been utilized in a number of applications including the synthesis of ...nanostructures and the creation of energy-harvesting devices. Here, we show that water evaporation from the surface of a variety of nanostructured carbon materials can be used to generate electricity. We find that evaporation from centimetre-sized carbon black sheets can reliably generate sustained voltages of up to 1 V under ambient conditions. The interaction between the water molecules and the carbon layers and moreover evaporation-induced water flow within the porous carbon sheets are thought to be key to the voltage generation. This approach to electricity generation is related to the traditional streaming potential, which relies on driving ionic solutions through narrow gaps, and the recently reported method of moving ionic solutions across graphene surfaces, but as it exploits the natural process of evaporation and uses cheap carbon black it could offer advantages in the development of practical devices.
To construct a soluble prokaryotic expression vector of the CXCR7-specific antagonist SDF-1/54R and evaluate its activity.
SDF-1/54r gene amplified by PCR was inserted into the soluble expression ...vector pET-41a+ engineered with GST fusion tag, and the recombinant vector was transformed into E. coli strain BL21 (DE3). After IPTG induction of E. coli, the expressed recombinant protein was purified with GST affinity chromatography purification system and confirmed by SDS-PAGE and Western blotting assay. The target protein SDF-1/54R was obtained after digestion of the purified product with enterokinase. Breast cancer MCF-7 cells with high expression of CXCR7 was treated with SDF-1/54R and the cell proliferation and metastasis was evaluated with MTT and chemotaxis assays.
The target protein SDF-1/54R obtained showed an obvious inhibitory effect on the proliferation and metastasis of MCF-7 cells as confirmed by MTT and chemotaxis assays.
SDF-1/54R is a good antagonist of CXCR7 and shows a potential value as an effe
Based on gray error GM (1,1) model, the paper proposed an improved error GM (1,1) model, and used this model to predict cultivated land in Yiyang. The results show that the improved error GM (1,1) ...model has high prediction accuracy, and better simulation results. And the results conform to the cultivated quantity change rule of Yiyang City, that is, the land area of Yiyang City, will appear in the next few years, modest growth trend, but the per capita arable land is still in the alert level of the United Nations. Therefore, protection of cultivated resources, rational utilization and protection of arable land are urgent tasks.
Solar cells based on inorganic absorbers, such as Si, GaAs, CdTe and Cu(In,Ga)Se2 , permit a high device efficiency and stability. The crystals' three-dimensional structure means that dangling bonds ...inevitably exist at the grain boundaries (GBs), which significantly degrades the device performance via recombination losses. Thus, the growth of single-crystalline materials or the passivation of defects at the GBs is required to address this problem, which introduces an added processing complexity and cost. Here we report that antimony selenide (Sb2 Se3 )--a simple, non-toxic and low-cost material with an optimal solar bandgap of ∼1.1 eV--exhibits intrinsically benign GBs because of its one-dimensional crystal structure. Using a simple and fast (∼1 μm min-1 ) rapid thermal evaporation process, we oriented crystal growth perpendicular to the substrate, and produced Sb2 Se3 thin-film solar cells with a certified device efficiency of 5.6%. Our results suggest that the family of one-dimensional crystals, including Sb2 Se3 , SbSeI and Bi2 S3 , show promise in photovoltaic applications.
Tactile detection is a crucial technology in many fields, such as electronic skin, touch screen control, human prostheses, and screen fingerprint identification. Tribotronics has demonstrated active ...mechanosensation from external mechanical stimuli, which greatly enriches the sensing mechanisms of tactile detection. In this work, a monolithic integrated indium‐gallium‐zinc‐oxide (InGaZnO or IGZO) thin‐film transistor (TFT) array is developed for high‐resolution tactile detection. By using the conventional semiconductor fabrication processes, each IGZO TFT cell in the array shows uniform electrical performance. In addition, the drain–source current can be individually tuned by the electrostatic potential generated by the contact electrification between a movable gate and the gate dielectric. The monolithic integrated array displays a relatively high resolution of 12 pixels per inch and can realize a millimeter‐level tactile perception and motion tracking. This work presents a facile and viable strategy toward micro/nano‐scale tribotronics, which can realize high‐resolution and large‐scale tactile detection.
A monolithic integrated tribotronic thin‐film transistor array is demonstrated for high‐resolution tactile detection by the combination of an indium‐gallium‐zinc‐oxide transistor array and a triboelectric nanogenerator. The proposed monolithic integrated array presents a facile and viable strategy toward micro/nano‐scale tribotronics and is promising for the next‐generation electronics including electronic skin, human prostheses, human–machine interfaces, healthcare monitoring, and wearable electronics.
This paper proposes a novel dc power-flow controller for a multiterminal HVDC system, which can be inserted in series on transmission lines to manage the dc power flow. Its key features include: 1) ...simpler circuit topology; 2) fewer components; and 3) the elimination of an external power supply and low-frequency high-voltage-insulation isolated transformer. A three-terminal HVDC system, including the dc power-flow controller, is studied and its operation principle and characteristics are analyzed. A simulation mode is built to test the feasibility and effectiveness of the proposed dc power-flow controller with cases of power injection step down, power loss of one terminal, and power-flow reversal. A three-terminal dc system is built in the lab to validate the dc power-flow controller. The results show that the proposed dc power-flow controller can enhance the performance and controllability of a multiterminal HVDC system.
Recognition of human behavior plays an important role in context-aware applications. However, it is still a challenge for end-users to build personalized applications that accurately recognize their ...own activities. Therefore, we present CAPturAR, an in-situ programming tool that supports users to rapidly author context-aware applications by referring to their previous activities. We customize an AR head-mounted device with multiple camera systems that allow for non-intrusive capturing of user's daily activities. During authoring, we reconstruct the captured data in AR with an animated avatar and use virtual icons to represent the surrounding environment. With our visual programming interface, users create human-centered rules for the applications and experience them instantly in AR. We further demonstrate four use cases enabled by CAPturAR. Also, we verify the effectiveness of the AR-HMD and the authoring workflow with a system evaluation using our prototype. Moreover, we conduct a remote user study in an AR simulator to evaluate the usability.
The growth of single-crystalline porous ZnO nanosheet frameworks (ZnO NSFs) was performed with a simple hydrothermal approach. The highly transparent poly(3,4-ethylenedioxythiophene) (PEDOT) film was ...prepared by an in-situ electrodeposition method on flexible ITO-PET substrate. Moreover, ZnO NSFs and PEDOT were made as photoanodes and counter electrodes (CE) for assembling fully flexible dye-sensitized solar cells (DSSCs), respectively. The interconnected nanostructures of ZnO NSF can deliver direct electron transport paths resulting in reduced recombination rate and accelerated electron transport. The PEDOT/ITO-PET exhibits outstanding catalytic ability in the reaction of I‾/I3‾ redox couple. A power conversion efficiency of 2.97% obtained from the fully flexible DSSCs, showed a comparable photovoltaic performance to the device with Pt CE. The highly photovoltaic performance can be mainly ascribed to the unique structure of porous ZnO NSFs and the outstanding catalytic properties of PEDOT CE.
Novel porous ZnO nanosheet frameworks (ZnO NSFs) on Ti-foil substrates consisting of innumerable single crystalline interconnected short nanorods and highly transparent poly(3,4-ethylenedioxythiophene) film on flexible ITO-PET substrates were employed for assembling fully flexible devices. The electrochemical impedance spectroscopy, IMPS and IMVS indicated that the ZnO NSFs/Ti based DSSCs exhibit lower recombination rate and longer electron lifetime than those based on commercial ZnO nanoparticles/Ti. The power conversion efficiency of the fully flexible DSSCs was 2.97%, showing a comparable photovoltaic performance to the rigid cell with Pt counter electrode. Display omitted
•Porous ZnO nanosheet frameworks were prepared by simple procedure.•Reduced recombination rate have been demonstrated.•A flexible DSSCs device based on PEDOT/ITO-PET counter electrode was assembled.•The ZnO photoanode based flexible DSSCs achieved a high efficiency of 2.97%.
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