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1.
The gas purging states affect electricity output and energy storage capacity of unitized regenerative fuel cells. In this study, a model of unitized regenerative fuel cell is established. Cell voltages and operating temperatures influences on the dynamic distribution of thermal fluid during purging process and the discharge of residual liquid water in electrolytic cell mode are investigated. The motivation of the present study is better understanding the gas purging characteristics and its effect on reaction behaviors of unitized regenerative fuel cells. Simulation results reveal a significant influence of purging gas temperature on the water flooding and a great effect of operating voltage on the water diffusion. The operating temperature of electrolytic cell model almost has little effect on purging results at different cell temperature and the same purging gas temperature. When the purging gas temperature is changed, higher temperatures of cell and purging gas facilitate liquid water discharging out from the cell regions. In cell water flooding situation, when having large liquid content, the purging gas has little effects on the water expelling process.  相似文献   
2.
A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion.  相似文献   
3.
《Ceramics International》2022,48(21):31811-31817
As one of the outstanding piezoelectric materials, relaxor-PbTiO3 single crystal also exhibits promising electro-optic and nonlinear-optic properties. Therefore, it is vital to understand the domain switching kinetics not only for optimizing strain-mediated devices performance but also for fabricating optical waveguides and periodic domain structures in optical applications. In this work, domain switching kinetics in annealed and pre-poled PMN-0.38PT single crystal under different external electric field were studied. Polarization reversal can be accomplished only by c-domain nucleation and growth in the annealed sample where the formation of the ferroelastic domains is hindered. In pre-poled sample, 90° domain switching happened by 90° domain wall reorientation under low electric field while 180° domain switching is accomplished by two-step 90° domain switching and c-domain growth under high electric field. The results are important for modulating domain structure for strain mediated and optical devices.  相似文献   
4.
The regulation of DNAzyme activity is an important problem for its in vivo applications. We achieved photochemical regulation of DNAzyme activity by using reversible DNA photo-crosslinking of 3-cyanovinylcarbazole (CNVK). The ODN containing CNVK photo-crosslinked to a pyrimidine base in the complementary strand after a few seconds of photoirradiation, and its photoadduct was split by photoirradiation of another wavelength. The activity of photo-crosslinked DNAzyme with CNVK was completely inhibited (OFF state). In contrast, after 312 nm irradiation, DNAzyme activity was recovered upon addition of a substrate strand (ON state). In addition, the photo-crosslinked DNAzyme is prone to enzymatic digestion by exonuclease. This photochemical OFF to ON switching with reversible DNA photo-crosslinking was regulated at the desired time and position; therefore, it might be possible to use it for in vivo application.  相似文献   
5.
An analytical model is presented to study the dynamics of wavelength division multiplexing (WDM) networks with waveband switching (WBS). The reduced load approximation method is considered to compute approximated network blocking probabilities in WBS-based WDM networks. The analytical model considers the link blocking probability due to insufficient link capacity and an impact of the waveband granularity (G). The analytical model also considers the node blocking probability due to unavailability of a switch port at the wavelength cross connect (WXC) layer of an Hierarchical cross connect (HXC) switch node. The set of nonlinear equations is obtained with the link independence assumption and solved using repeated substitutions. The accuracy of the analytical model is examined by comparing with simulation results considering the random-fit algorithm for waveband and wavelength assignments in different network scenarios. Lightpaths are routed between source and destination (s-d) HXC switch nodes using shortest path first (SPF) routing. An impact of the switch parameter to limit the input and the output WXC switch ports of an HXC switching node is also being investigated using the analytical model as well as through simulation results.  相似文献   
6.
ABSTRACT

This paper focuses on controllability and observability of multi-agent systems with heterogeneous and switching topologies, where the first- and the second-order information interaction topologies are different and switching. First, based on the controllable state set, a controllability criterion is obtained in terms of the controllability matrix corresponding to the switching sequence. Next, by virtue of the subspace sequence, two necessary and sufficient algebraic conditions are established for controllability in terms of the system matrices corresponding to all the possible topologies. Furthermore, controllability is considered from the graphic perspective. It is proved that the system is controllable if the union graph of all the possible topologies is controllable. With respect to observability, two sufficient and necessary conditions are derived by taking advantage of the system matrices and the corresponding invariant subspace, respectively. Finally, some simulation examples are worked out to illustrate the theoretical results.  相似文献   
7.
Ion cyclotron wave resonance heating system(ICRH) which is one of the most important auxiliary system in EAST provides conditions for heating the plasma. In order to make the whole transmission network of ICRH form the required state, the coaxial switching system was developed, which mainly consists of 11 same coaxial switches. Each coaxial switch has a controller with an RS485 communication interface and is able to switch between two states. All controllers are integrated to an RS485 hub which connects to the computer. A master computer software is developed to control the coaxial switching system so as to achieve the state needs of ICRH. Moreover, several rounds of experiments show that the coaxial switching system operates reliably. The coaxial switching system has already been applied to normal use currently.  相似文献   
8.
Many studies have shown the benefits of augmented reality (AR) to improve manufacturing and control processes in industry. However, the presentation of AR content through optical see-through head-mounted displays may induce unnatural viewing conditions, which consequences on the user’s visual system have not been investigated yet. This study aimed at assessing whether using AR instructions to guide a manual task, i.e., conditions where the user is forced to repeatedly look at and accommodate in different planes to extract information from both real and virtual environments, could potentially impact the visual system of operators. A before/after design study was carried out, asking 26 participants to perform Lego assemblies for 30 min with either paper or AR instructions. The effects of using AR compared to paper instructions were evaluated both on binocular vision, with classical optometric measurements, and on visual fatigue, with the Virtual Reality Symptoms Questionnaire. No clinically significant differences in optometric measurements (far/near visual acuity, stereoacuity, phoria, convergence, fusional amplitude, accommodation amplitude, accommodative convergence) have been found between AR and paper instructions, and only negligible fatigue symptoms have been seen specifically for AR. Results from both objective and subjective measurements suggest that there is no impact of AR on the oculomotor system and that, in this specific case of use, AR can be safely used for production operators.  相似文献   
9.
Large deformations of soft materials can give rise to the development of various elastic instabilities. The phenomenon is associated with a sudden and dramatic change in structure morphologies. The underlying mechanism is crucial for the formation of complex morphologies in biology. Moreover, the concept of instability-induced pattern transformations is promising for designing novel materials with switchable functions and properties. In this paper, we review the state of the art in elastic instability phenomena in soft materials. We start by considering the classical buckling in beam-based structure lattice designs. Then, we discuss the instability-induced microstructure transformations in soft porous materials, and heterogeneous multiphase and fiber composites. Next, the mechanisms – often involving the post-buckling consideration – leading to the wrinkling and folding, creasing, fringe, and fingering are discussed.  相似文献   
10.
Multilayer piezoelectric ceramics must be sintered in a reducing atmosphere, preventing oxidation of the inner base metal. Plate-like textured (Ba, Ca)(Ti, Sn, Hf)O3 ceramics with a <001> preferred orientation were successfully developed at a low oxygen partial pressure (PO2:10?8 atm) using a BaTiO3 (BT) template with sintering temperatures < 1300 °C, which is beneficial for multilayer applications using base metal co-firing with ceramics. When adding the 3 wt% BT template, the proposed samples had a Lottgering factor of 84 %, piezoelectric coefficients d33 = 324 pC/N, -d31 = 122 (pC/N), and Qm = 452, and the strain values increased from 0.07 % for the randomly oriented ceramics to 0.115 % at 20 kV/cm for the textured ceramics, confirming that the texturing behavior assisted the grain growth and improved both the soft and hard behaviors and insulation resistance of the proposed lead-free ceramics. These findings make a significant contribution to the production of high-power piezoelectric components.  相似文献   
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