Search

Finding hot carrier cooling suppression in new material structures is fundamentally important for developing promising technological applications. These phenomenona have not been reported for crystalline silicon phononic crystals. Herein, we experimentally design two-dimensional (2D) silicon samples consisting of airy hole arrays in a crystalline silicon matrix. For reference, the determined hot carrier cooling times were 0.45 ps and 0.37 ps, respectively, at probe wavelengths of 1080 nm and 1100 nm. Surprisingly, when the 2D structured silicon possessed the properties of a phononic crystal, significant suppression of hot carrier cooling was observed. In these cases, the observed hot carrier cooling times were as long as 15.9 ps and 10.7 ps at probe wavelengths of 1080 nm and 1100 nm, respectively, indicating prolongation by orders of magnitude. This remarkable enhancement was also observed with other probe wavelengths. The present work presents experimental evidence for hot carrier cooling suppression in 2D silicon phononic crystals and opens opportunities for promising applications.

In wireless sensor networks (WSNs), the efficiency of data transmission within a limited time is critical, especially for sensors designed with small batteries. In this paper, we design a cooperative transmission scheme with an energy-charging function in a WSN where an unmanned aerial vehicle (UAV) is considered for sensory data collection and energy charging. Specially, the sensor nodes are powered by the UAV for their data transmission. In the first phase, the UAV transmits the energy signal to the sensor nodes distributed on the ground. All the energy received by the sensor nodes is used to collect and transmit the sensory data to the UAV. In the second phase, local data transmissions are conducted among the collaborating sensor nodes in one cluster. In the third phase, the cooperative nodes send the collected sensory data to the UAV in the form of cooperative transmission. In the proposed scheme, we discovered that the size of the modulation constellation and the assigned time ratio of each phase were the key factors affecting the data transmission efficiency. In order to achieve the maximum data transmission, the optimal modulation constellation size and the optimal time ratio of each phase were found using the Lagrange multiplier method. Numerical results show that the proposed scheme with the optimal constellation size and the optimal time ratio can outperform the existing scheme in terms of the data transmission efficiency.

A graphene aerogel-coated molybdenum trioxide/polypyrrole (MoO3/GA@PPy) composite was synthesized via hydrothermal and in site polymerization reactions. The character of PPy, MoO3/GA, and MoO3/GA@PPy were investigated by X-ray diffraction, Fourier transform spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results of the morphological and structural analysis clearly revealed the formation of ternary nanocomposites. The electrochemical properties, such as capacitance, specific capacitance retention at different current loads, cycling stability, and impedance, were discussed as well. Improvement of electrochemical performances of the ternary nanocomposites was observed. The MoO3/GA@PPy showed a maximum specific capacitance of 1788 F/g at current density of 1 A/g.

To ensure the safety of operations with a fast-tumbling target, a detumbling strategy implemented by a dual-arm space robot with finger-type end effectors is proposed to attenuate the target rotation. A detumbling system that consists of the robot and the target is established. Through the contact effects between the two parts, the energy of the target is gradually dissipated. Evaluated by the detumbling duration, energy consumed, and the target movement, the contact strategy is developed. Through numerical simulations, the multipoint contact detumbling is verified feasible to detumble a fast-tumbling target. With suitable parameters, the kinematic response of the detumbling system could be bounded and steady, which makes further operation for the target easier.

Ultrathin metal film (UTMF) with a ZnO/Ag/ZnO hybrid structure was used as transparent electrode in a high-efficiency bulk heterojunction system for the fabrication of ITO-free polymer solar cells. The performance of the devices was carefully tuned through optical simulation using transfer matrix method by varying the thickness of ZnO seed layer and thin absorber layer. By employing appropriate device architecture, polymer solar cells fabricated using this UTMF-based electrode show efficiency as high as 9.49%, which is slightly higher compared to that of ITO-based device. From good agreement between the external quantum efficiency and optical modeling, it was found that the optimized microcavity configuration formed in UTMF-based device can greatly enhance the absorbance of the BHJ layer at longer wavelength as well as the favored exciton distribution for better charge transport and collection.

Although high efficiencies have been demonstrated in organic solar cells (OSCs), the development of semitransparent devices is still lagging behind due to the difficulty in making a balance between the active layer absorption and device transmittance. To address this challenge, a detailed study of semitransparent OSCs (ST-OSCs) based on the blends of the low bandgap polymer PTB7-Th and ultra-narrow bandgap nonfullerene acceptor IEICO-4F is carried out. Comprehensive optical modeling using the transfer matrix method (TMM) has been performed to assist the design of ST-OSCs and understand the effect of active layer composition and distributed Bragg reflectors (DBRs) on the device performance. By varying the PTB7-Th/IEICO-4F blending ratio from 1:1.5 to 1:3 and incorporating of DBRs, the average visible transmittance (AVT) of the ST-OSCs was dramatically increased by over 26% with a slight decrease in photocurrent (Jmax) less than 5%. This significant improved light utilization can be attributed to the enhanced photon harvesting of NIR range and decreased visible light absorption by increasing the IEICO-4F content, as well as the optimal optical properties in the ST-OSCs with the use of DBRs. Our results can provide a feasible way to optimize the light harvesting and transmittance of the device for achieving high-performance ST-OSCs.

In order to evaluate the influence of antibiotics on the respiration of subpopulations in biofilms, dissolved oxygen microelectrodes were used to determine the oxygen concentration inside E. Coli biofilms. Based on the results, the oxygen consumption rate varying with depth in the biofilms was calculated before and after the treatment with antibiotics. For both ceftriaxone sodium and chloramphenicol, significant attenuation of oxygen consumption was identified when the system reached steady state. However, by monitoring the oxygen concentration change induced by ceftriaxone sodium, an increased oxygen consumption rate and a shortened oxygen penetration depth were identified in the first few hours, which indicated the accelerated respiration of the subpopulation. Followed by cellular death, the induced respiration acceleration seems to be part of the action mechanism of ceftriaxone sodium. Compared to the planktonic cells, the biofilms showed much higher tolerance to ceftriaxone sodium, which may be attributed to the extended hypoxic zone induced by the accelerated respiration.

The linear guide rail has high accuracy requirement for straightness in some mechanical equipment. In order to meet the straightness accuracy of the linear guide rail, straightening machine can be used to straighten the linear guide rail in the industrial manufacturing process. Deformation and bending often occur in different planes, which is a challenge to the traditional straightening control systems. This paper proposes a control system to straighten the linear guide rail precisely. The function of the control system is modularized, which is divided into four main functional modules. Based on the analysis of functional modules of the control system, the straightening control flow is designed, and the workpiece rotation operation is added based on the previous straightening control process, which allows the straightening press head to straighten the linear guide rail at the optimal angle. This also provides a new idea for optimizing the structure of the straightening machine. The hardware and software of the control system are also designed, motion control card is the key part of the hardware, and the function of the software is divided into different functional modules. The control system is used in the straightening machine to straighten the linear guide rail. The experimental data shows that the straightened linear guide rail has a high straightness accuracy, the efficiency of the straightening process has also been improved.

Highlights • The recombinant L. acidophilus expressing S1 and S2 domains of PEDV were generated. • The oral vaccines for PED were based on a swine-origin L. acidophilus. • The oral L. acidophilus vaccines induced humoral and mucosal immunity in mice. • The L. acidophilus-S1 vaccine induced humoral and mucosal immunity in sows., Porcine epidemic diarrhea (PED) is a highly contagious intestinal infectious disease caused by porcine epidemic diarrhea virus (PEDV), which is characterized by a high mortality rate in piglets. Since 2012, a remarkable growth in PED outbreaks occurred in many pig farms in China, landing a heavy blow on the pig industry. In order to develop a new effective vaccine for the current PEDV, oral vaccines were generated by transferring eukaryotic expression recombinant plasmids carrying the S1 and S2 (antigenic sites of the S protein) epitopes of PEDV into a swine-origin Lactobacillus acidophilus (L. acidophilus). After oral immunization of the BALB/c mice, higher levels of anti-PEDV specific IgG and SIgA antibodies and cellular immune responses were detected in mice orally administered with the recombinant L. acidophilus-S1 compared to the L. acidophilus-S2. Furthermore, L. acidophilus-S1 was used to inoculate the pregnant sows orally and the results showed that the recombinant L. acidophilus-S1 could elicit a specific systemic and mucosal immune response. In summary, our study demonstrated that oral immunization with L. acidophilus-S1 could improve the humoral and mucosal immune levels in sows and would be a promising candidate vaccine against PEDV infection in piglets.

Parallel-connected tandem cells adopting a highly efficient donor polymer, PTB7-Th, combined with acceptor fullerene PC71BM as the back sub-cell was introduced to further improve the performance of polymer solar cells. Design of the device architecture was investigated using modeling and simulation methods based on the transfer matrix formalism. To optimize the device structure, detailed analysis of the effect of active layer thickness, different device structure, and transparent Ag intermediated electrode on the short-circuit current density has been studied. It was found the long-wavelength absorption in the top-illuminated ITO-free back cell was significantly enhanced due to the resonant microcavity effect, leading to an efficient utilization of the incident light and increased photocurrent. Giving these advantages, the power conversion efficiency of the parallel homo-tandem cell was estimated to be ~ 11%, which was ~ 15% higher than that of a single cell of PTB7-Th. Moreover, the maximum achievable current density and the corresponding optimum active layer thickness of the sub-cells varied a little as the thickness of ultrathin Ag layer was changed, indicating that parallel connection architecture provided more freedom in the design and optimization for high-performance tandem solar cells.

Motor shaft is widely used in many industrial fields. As a crucial factor, the motor shaft straightness has significant impact on its working performance, thus the straightening process becomes an essential step in shaft manufacturing. In order to achieve automatic straightening of the motor shaft, a motor shaft straightness control system is designed in this paper. A motor shaft straightening process is developed for this system. The factors affecting the straightness of the motor shaft are analyzed. Three deformation patterns are proposed based on the analysis of motor shaft deformation. A structure of the modular straightness control system is designed based on the motor shaft straightening process. A motor shaft straightening stroke prediction algorithm is developed based on the three-point bending process by FEM and elastic-plastic deformation theory. The validity of the system and the correctness of the straightening stroke prediction algorithm are verified by experiments.

Power conversion efficiency (PCE) and device stability are the two most important concerns for next generation perovskite solar cells (PSCs). Herein, we report an investigation for long-term stable perovskite Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 solar cells toward high efficiency via the light management strategy. To that end, we first experimentally determine complex optical constants of this kind of perovskite thin film by using variable angle spectroscopic ellipsometry measurements. By constructing the proper model, the calculated photocurrent density (Jsc) of 23.2 mA/cm2 of the planar PSC model is only slightly higher than the measured 23.0 mA/cm2 of our champion planar cell with excellent consistency, where the PCE is up to 20.5% with active area of 0.16 cm2, demonstrating a long-term stability capable of retaining 91% of initial PEC for 40 days. It is further found that when the front texture of nanocone array design is applied to the planar cell as a surface antireflection, the Jsc value of 24.8 mA/cm2 with the resulting PCE of 22.1% is projected from the present real planar PSC device with active area of 0.16 cm2.

The saying "An apple a day keeps the doctor away" has been known for over 150 years, and numerous studies have shown that apple consumption is closely associated with reduced risks of chronic diseases. It has been well accepted that dysbiosis is the reflection of various chronic diseases. Therefore, this study investigates the effects of apple polysaccharides (AP) on gut dysbiosis. High-fat diet (HFD) fed rats were treated for 14 weeks with AP. The microbiota composition, microbiota-generated short chain fatty acids (SCFAs), gut permeability and chronic inflammation were analyzed. AP treatment showed higher abundance of Bacteroidetes and Lactobacillus while lower Firmicutes and Fusobacteium. AP significantly increased total SCFAs level that contributed by acetic acid and isobutyric acid. Moreover, AP dramatically alleviated dysbiosis-associated gut permeability and chronic inflammation with decreased plasma LBP, up-regulation of Occludin, down-regulation of tumor necrosis factor a (TNF-a), monocyte chemotactic protein 1 (MCP-1), chemokine ligand 1 (CXCL-1) and interleukin 1 beta (IL-1β). The potential mechanism is due to the fact that AP reduces gut permeability, which involves the induction of autophagy in goblet cells. Therefore, AP exerts health benefits through inhibiting gut dysbiosis and chronic inflammation and modulating gut permeability in HFD-induced dysbiosis rats.

The strategy of active-passive integrated vibration control on the truss enveloping control moment gyroscopes (CMGs) is presented and its characteristics of time domain and frequency domain are analyzed. Truss enveloping CMGs contains pyramid-type CMGs, which are enveloped by multiple struts. These struts can be employed to realize the active-passive integrated vibration control. In addition, the struts of the trusses can maintain the working space of CMGs. Firstly, the disturbance characteristics of CMGs are analyzed considering static and dynamic imbalances of the CMG's rotor; then, an active-passive integrated vibration isolation truss structure is developed based on its characteristics. This structure can restrain the CMG vibration as much as possible and reduce its influence on the photographic quality of optical payloads. Next, the dynamic model of the active-passive vibration isolation truss structure is established. The frequency domain analysis of this model shows that the active-passive integrated vibration control method can restrain the high-frequency vibration and also improve the characteristics of low-frequency vibration. Finally, the dynamic model for the whole satellite is built with this type of CMGs. The time domain simulations of satellite attitude control verify the attitude control improvements resulting from the CMGs vibration control strategy.

Infrared and visible image fusion has been an important and popular topic in imaging science. Dual-band image fusion aims to extract both target regions in infrared image and abundant detail information in visible image into fused result, preserving even enhancing the information that inherits from source images. In our study, we propose an optimization-based fusion method by combining global entropy and gradient constrained regularization. We design a cost function by taking the advantages of global maximum entropy as the first term, together with gradient constraint as the regularized term. In this cost function, global maximum entropy could make the fused result inherit as more information as possible from sources. And using gradient constraint, the fused result would have clear details and edges with noise suppression. The fusion is achieved based on the minimization of the cost function by adding weight value matrix. Experimental results indicate that the proposed method performs well and has obvious superiorities over other typical algorithms in both subjective visual performance and objective criteria.

The degradation of optical microscopic imaging is space-variant, and how to fast restore optical degraded image remains a special problem. Based on point spread function (PSF) estimation under each field of view (FOV), a L0 gradient-constrained image restoration method is proposed to solve optical degradation in microscopic imaging. Firstly, the whole scene is segmented into several different regions according to different FOV. The PSFs for each region are estimated from modulation transfer function (MTF) measured in advance. Secondly, a penalty function is designed using L0 gradient constraint to deblur the degraded images of each sub-FOV. Finally, a weighted stitching approach is used to stitch the restored images of multiple FOV (m-FOV). Experimental results indicate that the m-FOV analysis could well solve the problem of space-variant degradation. Compared with the other methods, both subjective and objective evaluation results prove that the L0 norm idea could rapidly and effectively restore the degraded image. The approach could be well applied to a real product.

By creating an effective π-orbital hybridization between the fullerene cage and the aromatic anchor (addend), the azafulleroid interfacial modifiers exhibit enhanced electronic coupling to the underneath metal oxides. High power conversion efficiency of 10.3% can be achieved in organic solar cells using open-cage phenyl C61 butyric acid methyl ester (PCBM)-modified zinc oxide layer.