The information in the three-dimensional transverse injection flow field is very important for the design of a scramjet combustor, and it should be explored by using the data mining and ...multi-objective design optimization methods. In the current study, the three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations coupled with the two equation SST k-ω turbulence model has been utilized to simulation the transverse injection flow field with a freestream Mach number 3.75, and the influence of the turbulence model on the flow field properties has been evaluated as well. At the same time, three grid scales have been employed to perform the grid independency analysis, and the predicted results have been compared with the available experimental data in the open literature in order to carry out the code validation process. Further, the effect of the injector geometric configuration on the mixing efficiency of the transverse injection flow field has been investigated, and four different configurations have been considered in the current study, namely the square port, the diamond port, the equilateral triangular port and the circular port. The obtained results show that the case with the square injection port can obtain the largest mixing efficiency, and it can offer the rapidest near-field mixing between the injectant and the air. At last, the transverse injection flow field with the square injection port has been optimized by the surrogate-based evolutionary algorithm, and the relationships between the design variables and the objective functions have been explored by the variance analysis method. It is shown that the jet-to-crossflow pressure ratio has a high remarkable impact on the total pressure recovery efficiency, as well as the number of the injection ports on the drag force performance. The drag force increases with the increase of the number of the injection ports due to the deeper penetration of the rear jets.
•The information in the three-dimensional transverse injection flow field has been explored.•Effects of turbulence model and geometric configuration on flow field properties have been performed.•Jet-to-crossflow pressure ratio has a high remarkable impact on total pressure recovery efficiency.•Number of injection ports has a high remarkable impact on drag force performance.
The development of an effective one‐photon excitation pathway to improve the charge‐carrier separation and mobility of semiconductors, which have been proven to be favorable for heterogeneous ...catalysis, is highly desirable but remains a great challenge. Herein, a high‐throughput one‐photon excitation pathway is reported by constructing 0D carbon dots/3D porous carbon nitride nanovesicles (denoted as CDs/PCN NVs) heterostructures for photocatalytic hydrogen evolution. In particular, the optimum CDs/PCN NVs heterostructures exhibit an impressive performance of 14.022 mmol h−1 g−1, which is 56.54 times higher than that of pristine CN. Detailed characterization reveals that the improved performance is primarily attributed to the high‐throughput and one‐photon excitation pathway. The former could be attributed to a great deal of CDs with high charge‐carrier mobility coupled to PCN NVs, which enable more electrons to be photoexcited via the broad absorption response, and the multiple reflection of incident light owing to the porous nanovesicle structure with shortened route of carriers migrating toward the surface; the latter would lead to the photoinduced holes and electrons accumulated at the valence band of PCN NVs and surface of CDs, respectively, achieving an effective spatial separation. The high‐throughput one‐photon excitation pathway demonstrated here may provide insights into the development of nanocomposites for various related applications.
A high‐throughput one‐photon excitation pathway is reported by constructing 0D carbon dots/3D porous carbon nitride nanovesicles (CDs/PCN NVs) heterostructures for visible‐light driven hydrogen evolution. In particular, the covalently bonded CDs on PCN NVs enable a high throughput charge migration in the wide spectrum visible light region and promote effective spatial separation via a one‐photon excitation pathway.
• Process and outcome controls positively influence project performance.• Outcome control is more effective than process control.• Vendor and client capability risks differentially moderate control ...effectiveness.
Control over outsourced projects is a significant concern for both clients and vendors. Although the effect of control on performance has been studied previously, vendor and client capability risks have rarely been merged into the control–performance relationship. Using paired quantitative data collected from 234 business process outsourcing projects, we empirically determine that outcome control is more effective than process control, although both positively influence the performance of outsourced projects. Vendor and client capability risks play miscellaneous moderating roles on the effects of process and outcome controls on performance. In the presence of high vendor capability risk, the effect of process control on performance is high, but the effectiveness of outcome control is low. By contrast, high client capability risk results in low effectiveness of process control but high effectiveness of outcome control. Different control modes have various attributes and generate different levels of performance. Either vendor or client capability risk serves as a double-edged sword with regard to control. Therefore, the risky situation of both vendors and clients should be considered in the selection and enforcement of control in managing outsourced projects.
This article presents the 38-GHz phased array 32-element Tx and 16-element Rx with 2-GHz IF and 5-GHz LO for fifth-generation (5G) millimeter-wave (MMW) communications. The Tx and Rx beamformers and ...upconverters/downconverters are fabricated in 65-nm CMOS. The PAs and LNAs near antenna ends are fabricated in 0.15-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> GaAs pHEMT. The eight-element Tx and four-element Rx phased array printed circuit board (PCB) modules integrated with multiple integrated circuits (ICs) and endfire antennas are implemented as unit cells. Four pieces of Tx modules are vertically stacked to construct an <inline-formula> <tex-math notation="LaTeX">8\times {4} </tex-math></inline-formula> brick array (planar array), while four Rx modules are to construct a <inline-formula> <tex-math notation="LaTeX">4\times {4} </tex-math></inline-formula> array. According to 38-GHz over-the-air (OTA) measurements, the 32-element Tx shows 47.5-dBm equivalent isotropic radiated power (EIRP) at OP<inline-formula> <tex-math notation="LaTeX">_{\mathrm {1 ~dB}} </tex-math></inline-formula> with −35.2-dB image rejection ratio (IMRR) and −37.4-dB <inline-formula> <tex-math notation="LaTeX">\times 8 </tex-math></inline-formula> LORR. The 16-element Rx at 38 GHz shows −4-dBm OP<inline-formula> <tex-math notation="LaTeX">_{\mathrm {1~dB}} </tex-math></inline-formula> with −28-dB IMRR and −36.6-dB LORR. The Tx and Rx support the beam scanning around ±60° azimuth and ±30° elevation planes. The Tx-to-Rx wireless data link demonstrates 64 quadrature amplitude modulation (QAM)/400 M-BR, 256 QAM/200 M-BR, and 512 QAM/100 M-BR in 20 m. To the best of our knowledge, this work is the first 5G 37-/39-GHz phased array Tx/Rx using the scalable brick array configuration and demonstrating competitive performances compared with previous works.
2D materials show many particular properties, such as high surface‐to‐volume ratio, high anisotropic degree, and adjustable chemical functionality. These unique properties in 2D materials have ...sparked immense interest due to their applications in photocatalytic systems, resulting in significantly enhanced light capture, charge‐transfer kinetics, and surface reaction. Herein, the research progress in 2D photocatalysts based on varied compositions and functions, followed by specific surface modification strategies, is introduced. Fundamental principles focusing on light harvesting, charge separation, and molecular adsorption/activation in the 2D‐material‐based photocatalytic system are systemically explored. The examples described here detail the use of 2D materials in various photocatalytic energy‐conversion systems, including water splitting, carbon dioxide reduction, nitrogen fixation, hydrogen peroxide production, and organic synthesis. Finally, by elaborating the challenges and possible solutions for developing these 2D materials, the review is expected to provide some inspiration for the future research of 2D materials used on efficient photocatalytic energy conversions.
Although the research of 2D photocatalysts has made great progress in the past decades, there are still many challenges in understanding the deep relationship between the surface state and the reaction mechanism. The surface modification strategies and reaction mechanisms of 2D photocatalysts are reviewed, and some useful views are put forward for future research in this field.
The Reynolds averaged Navier-Stokes (RANS) equations coupled with the renormalization group (RNG)
k-ε
and the single-step chemical reaction mechanism have been used to evaluate the influence of the ...radius of the strut tip, the half-angle of the strut and the strut location relative to the combustor entrance on the combustion performance of the combustor has been discussed. At the same time, the numerical method has been validated by the available experimental shadowgraph, velocity measurements and temperature measurements in the open literature. With the increasing of the radius of the strut tip, the separation region generated due to the strong interaction between the shock wave and the boundary layer becomes broader, and accordingly, a bifurcated shock wave appears at the front of the strut, then a shock wave train. The shock waves generated at the intersectional points between the walls of the strut and the sonic lines play an important role in the generation of the separation zone, and they can improve the combustion efficiency to a certain extent. Further, the mixing process is more intensive than the chemical reaction process in the vicinity of the strut base, and the combustion efficiency increases nearly monotonically with the increasing of the horizontal distance in the range considered in the current study. When the intersectional point between the leading shock wave and the upper wall overlaps with the divergence point, the combustion efficiency at the exit of the combustor becomes the largest, and its value is nearly 96.2%.
There is an urgent need for vaccines against coronavirus disease 2019 (COVID-19) because of the ongoing SARS-CoV-2 pandemic. Among all approaches, a messenger RNA (mRNA)-based vaccine has emerged as ...a rapid and versatile platform to quickly respond to this challenge. Here, we developed a lipid nanoparticle-encapsulated mRNA (mRNA-LNP) encoding the receptor binding domain (RBD) of SARS-CoV-2 as a vaccine candidate (called ARCoV). Intramuscular immunization of ARCoV mRNA-LNP elicited robust neutralizing antibodies against SARS-CoV-2 as well as a Th1-biased cellular response in mice and non-human primates. Two doses of ARCoV immunization in mice conferred complete protection against the challenge of a SARS-CoV-2 mouse-adapted strain. Additionally, ARCoV is manufactured as a liquid formulation and can be stored at room temperature for at least 1 week. ARCoV is currently being evaluated in phase 1 clinical trials.
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•Development of LNP-encapsulated mRNA vaccine (ARCoV) targeting the RBD of SARS-CoV-2•ARCoV induces neutralizing antibodies and T cell immunity in mice and NHPs•ARCoV vaccination confers full protection against SARS-CoV-2 challenge in mice•ARCoV is a thermostable vaccine candidate for phase I studies
ARCoV is an LNP-encapsulated mRNA vaccine platform that is highly immunogenic and safe in mice and non-human primates, conferring protection against challenge with a SARS-CoV-2 mouse-adapted strain.
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