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The ascent trajectory design of a rocket-based combined cycle (RBCC) hypersonic vehicle has many typical characteristics, including the complex working mode of the RBCC power system, strong coupling between thrust and flight state, strong nonlinear model and many complex constraints etc. This paper proposes a rapid trajectory optimization method based on sequential convex optimization to optimize the complex ascent trajectory with the RBCC power system. Firstly, a mathematical model for optimizing the ascent trajectory of the RBCC hypersonic vehicle is established to describe the angle of attack control system with and without the second-order lag. Then, the optimization model is made convex and discretized based on the convex optimization theory, and a trajectory optimization strategy is improved. Finally, taking the maximum terminal mechanical energy as optimization objective, the ascent trajectory optimization is simulated in cases with and without the second-order lag in the angle of attack control system. The simulation results show that the proposed mathematical model and the ascent trajectory optimization method are rapid and reliable and that the optimization results meet the characteristics of the RBCC power system and provide reference for the application of a RBCC power system and the design of an angle of attack control system.

Aiming at the reentry glide trajectory design of hypersonic vehicles with uncertain parameters, a robust trajectory optimization method is proposed to enhance the anti-interference ability and process reliability. Firstly, a robust trajectory optimization model for re-entry gliding under uncertain conditions is constructed, which is transformed into a deterministic trajectory optimization problem with dimension expansion by using an uncertainty propagation algorithm based on the Gaussian quadrature and non-intrusive polynomial chaos. Then, the convex optimization technology is used to convexity and discretize the problem, and a deterministic trajectory optimization strategy based on the sequential convex optimization algorithm is designed to achieve a fast solution for the high-dimensional deterministic problem. Finally, the hypersonic glide reentry of the American X-33 is chosen as an example for the numerical simulation. The results show that comparing with the traditional deterministic trajectory optimization algorithm, the present method can effectively reduce the impact of random interference on the reentry glide trajectory and improve the reliability and robustness of the trajectory.

According to the d-band center theory of transition-metals, s-block main group metals with fewer valence electrons and delocalized s/p-orbitals are considered to exhibit poor electrocatalytic activity. Therefore, single-atom catalysts (SACs) for CO2 electroreduction to CO primarily focus on transition metal and p-block main group metal atoms as active centers. Herein, we prepared a porous carbon material doped with N/O coordinated K atoms using a simple high-temperature solid-phase synthesis method. The synthesized K–N, O/C catalyst demonstrates remarkable CO selectivity with Faraday efficiency (FE) exceeding 90% over a wide potential window between −0.5 V and −0.9 V versus the reversible hydrogen electrode (vs. RHE). Moreover, the catalyst exhibits a maximum FE of 97.8% towards CO at −0.6 V vs. RHE. In situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) confirms the formation of *COOH on the K–N, O/C catalysts. Through Density Functional Theory (DFT) calculations, we screen out the most possible coordination structures. The K–O2 and K-pyrrolic-N2 models show significantly high CO2 reduction activity. Heteroatom doping induces partial overlap of the electronic states of the s and p orbitals of the K atom with the p orbitals of the coordinated O atom or N atom, thus modulating the electronic structure of the K atom into the catalytically active center for the conversion of CO2 to CO. [ABSTRACT FROM AUTHOR]

A rapid trajectory-planning method based on an analytical predictor–corrector design of drag acceleration profile and a bank-reversal logic based on double-stage adaptive adjustment is proposed to solve the entry issue under time and full-state constraints. First, an analytical predictor–corrector algorithm is used to design the profile parameters to satisfy the terminal of altitude, velocity, range, time, and flight-path angle constraints. Subsequently, an adaptive lateral planning algorithm based on heading adjustment and maintenance is proposed to achieve the flight stage adaptive division and determination of the bank-reversal point, thereby satisfying the terminal position and heading angle constraints. Concurrently, a rapid quantification method is proposed for the adjustable capacity boundary of the terminal heading angle. On this basis, a range-and-time correction strategy is designed to achieve high precision and the rapid generation of a three-degree-of-freedom entry trajectory under large-scale lateral maneuvering. The simulation results demonstrated that compared with the existing methods, the proposed method can adaptively divide flight stages, ensuring better multitask applicability and higher computational efficiency. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO2 to HCOOH is considered one of the most appealing routes to alleviate the energy crisis and close the anthropogenic CO2 cycle. However, it remains challenging to develop electrocatalysts with high activity and selectivity towards HCOOH in a wide potential window. In this regard, Ag/Bi2O2CO3 was prepared by an in situ electrochemical transformation from Ag/Bi2O3. The Ag/Bi2O2CO3 catalyst achieves a faradaic efficiency (FE) of over 90% for HCOOH in a wide potential window between −0.8 V and −1.3 V versus the reversible hydrogen electrode (RHE). Moreover, a maximum FE of 95.8% and a current density of 15.3 mA cm−2 were achieved at a low applied potential of −1.1 V. Density functional theory (DFT) calculations prove that the high catalytic activity of Ag/Bi2O2CO3 is ascribed to the fact that Ag can regulate the electronic structure of Bi, thus facilitating the adsorption of *OCHO and hindering the adsorption of *COOH. This work expands the in situ electrochemical derivatization strategy for the preparation of electrocatalysts. [ABSTRACT FROM AUTHOR]

A highly active, stable and low-cost platinum-free anode catalyst based on Ru for hydroxide exchange membrane fuel cells (HEMFCs) is hindered by the strong oxophilicity of Ru, which makes it easy to oxidize during the test. Herein, we found that Ru/CeO2(v)/C (oxygen-vacancy-rich CeO2/Ru nanoparticles supported on carbon) exhibit excellent catalytic activity with a mass activity of 8.06 A mgNM−1 and a specific activity of 2.85 mA cmNM−2, which are 19.6/20.1 and 2.3/8.4 times higher than those of Pt/C and PtRu/C, respectively. Moreover, Ru/CeO2(v)/C also exhibits excellent stability and CO tolerance in alkaline media. Experimental and theoretical studies reveal that the improved charge transfer from Ru to CeO2(v) significantly tunes the electronic structure of Ru sites and optimizes the hydrogen binding energy (HBE) of Ru, while CeO2(v) provides abundant hydroxyl adsorption sites. We attribute this enhancement to the interfacial effect, which can realize the equilibrium adsorption of hydrogen and hydroxyl groups on the interface and synergistically promote the Volmer reaction, thereby enhancing the activity and stability of the catalyst. [ABSTRACT FROM AUTHOR]

To improve the generality and computational efficiency of robust trajectory optimization technology under multi parameter uncertainty, a robust trajectory optimization method based on stochastic response surface method and polynomial chaos is designed. Firstly, non-intrusive polynomial chaos is combined with stochastic response surface, and a Latin hypercube sampling strategy is introduced to establish a multi-dimensional uncertainty quantification model, which realizes the effective and accurate transformation of the uncertain optimization problem. Secondly, combining the model with the convex optimization method, a trajectory optimization solution strategy based on the sequential convex optimization algorithm is designed to realize the rapid solution of the high-dimensional deterministic optimization problem. Finally, a hypersonic glide trajectory optimization problem considering multi parameter uncertainty such as initial state and process parameters is simulated and compared with the existing methods. The results show that compared with the traditional deterministic trajectory optimization algorithm, the proposed method can obtain the hypersonic glide trajectory with both reliability and robustness. Compared with the existing robust trajectory optimization methods, the proposed method has considerable accuracy and significant computational efficiency, which can ensure the efficiency and reliability of the robust trajectory optimization trajectory generation when the dimension of random variables increases. [ABSTRACT FROM AUTHOR]

As an external field, a magnetic field can change the electrocatalytic activity of catalysts through various effects. Among them, electron spin polarization on the catalyst surface has attracted much attention. Herein, we investigate the sensitive response behavior of a Cu2O nanocubes to an in situ magnetic field. Under a 3 T strong magnetic field, the total transferred electron quantity in IT test (−1.1 VRHE) and the current density in the polarization curve increase by 28.7% and 54.7%, respectively, while the onset potential decreases significantly by 114 mV. Moreover, it was found that product selectivity was also altered by the magnetic field. The Faraday efficiency of C1 increases substantially, along with the inhibition of C2+ reaction paths and the HER. Our experimental results and DFT calculation demonstrate that a hybrid magnetic effect accelerates the CO2RR kinetic and generates spin polarization of the catalyst surface. The polarized surface changes the binding energy of *OCHO/*COOH and inhibits singlet C–C coupling, which restrains the C2+ reduction path and thus more CO2 is reduced to HCOOH. [ABSTRACT FROM AUTHOR]

Ruthenium dioxide-based electrocatalysts show the most potential in the acidic oxygen evolution reaction (OER). However, most of them show low current density, low mass activity and unsatisfactory stability under strong acidic and oxidative conditions. Herein, an indium-induced-synthesis InxRuyO2 nanoribbon electrocatalyst (named In0.17Ru0.83O2-350) was prepared, which achieves an overpotential of 177 mV at a current density of 10 mA cm−2 in 0.5 mol L−1 sulfuric acid. The mass activity is up to 1094.90 A gRu−1 at an overpotential of 300 mV, which is among the highest for ruthenium dioxide-based catalysts. Moreover, the catalyst displays a current density up to 400 mA cm−2, which is the highest current density in a small electrode system reported so far. It is found that indium doping can shift down the d-band center of Ru and reduce its work function, which can boost the electron transfer capacity between the catalyst surface and the reactants. Finite-element method simulations further demonstrate that the nanoribbon structure can not only expose more active sites to improve the mass activity of ruthenium and reaction current density, but also enhance the surface electric field intensity to boost the adsorption capacity of water molecules and the capacity of electron transfer, thereby accelerating the dynamics of OER. [ABSTRACT FROM AUTHOR]

BackgroundAlthough there are more than 60 smartphone apps for smoking cessation in China, many of them do not include the content and features that health care professionals and smokers prefer—which may make them impractical, unengaging, and ineffective. Therefore, we investigated both health care providers’ and smokers’ preferences for features of future smoking cessation apps. ObjectiveThis study aimed to investigate Chinese health care providers’ and smokers’ desired features of a smoking cessation app, with the goal of providing design recommendations for app designers and researchers. MethodsBoth Chinese smokers who own smartphones (n=357) and Chinese health care providers (n=224) responded to a survey collecting data on their sociodemographic characteristics and opinions on the importance of 20 smoking cessation app design features studied in previous US research. ResultsChinese health care providers expressed strong support of smoking cessation apps on a number of attitude indicators (range 153/224, 68.3% to 204/224, 91.1%). They rated nearly all (18/20) features as very or extremely important (range 52.2%-83.4%) and rated nearly all features (17/20) as more important than the smokers did. More than 60% of smokers rated the following 4 features as very or extremely important: allow sharing the process of smoking cessation with family members and friends (216/319, 67.7%), helping smokers track their progress (such as the amount of smoking per day; 213/319, 66.8%), helping with the side effects of medications and nicotine withdrawal symptoms (201/319, 63.0%), and adapting to ongoing needs and interests of smokers (194/319, 60.8%). Contrary to a similar study of US smokers and health care providers, Chinese smokers and providers rated reputation and ability to communicate with family members and friends as important features, whereas Chinese smokers rated privacy and security as less important. ConclusionsThe design of future smoking cessation and health behavior change apps should consider perspectives of both providers and smokers as well as the role of culture.

Designing robust catalysts for increasing the sluggish kinetics of the urea oxidation reaction (UOR) is challenging. Herein, the regulation of spin states for metal active sites by photoexcitation to facilitate the adsorption of urea and intermediates is demonstrated. Mo-doped nickel sulfide nanoribbon arrays (Mo-Ni 3 S 2 @NMF) with excellent light-trapping capacity are successfully prepared. Under AM 1.5G illumination, the activity of the Mo-Ni 3 S 2 @NMF exhibits a 50% improvement in the UOR current. Compared with those under dark conditions, Mo-Ni 3 S 2 @NMF achieve 10 mA cm -2 at 1.315 V RHE for UOR and 1.32 V cell for urea electrolysis, which are decreases of 15 and 80 mV, respectively. The electron spin resonance, in situ Fourier transform infrared spectroscopy analysis and density functional theory calculations reveal that illumination led to the formation of Ni 3+ active sites in a high-spin state, which strengthens the d-p orbital hybridization of Ni-N, hence facilitating the adsorption of urea. C─N cleavage of the * CONN intermediate is further inhibited, which promotes the oxidation of urea molecules via the active N 2 pathway, thereby accelerating the UOR rate., (© 2024 Wiley‐VCH GmbH.)

The electrocatalytic urea oxidation reaction (UOR) provides a promising alternative to the oxygen evolution reaction (OER) for various renewable energy-related systems owing to its lower thermodynamic barriers. However, its optimization and commercial utilization were hampered due to a lack of mechanistic understanding. Here, we demonstrate a Ce-doped Ni 3 S 2 catalyst supported on Ni foam (Ce-Ni 3 S 2 /NF) with superior activity toward UOR. The resultant Ce-Ni 3 S 2 /NF catalyst exhibits a lower Tafel slope of 20.3 mV dec -1 , a higher current density of 100 mA cm -2 at 1.39 V versus RHE, and better durability than those for Ni 3 S 2 /NF. Based on in situ synchrotron radiation X-ray absorption spectroscopy, in situ Fourier transform infrared (FTIR), and in situ Raman spectroscopy, we observe the structural reconstruction of sulfide and identify the adsorbed intermediates during UOR. Density functional theory (DFT) calculations reveal that Ce can regulate the electronic structure of Ni through Ce(4f)-O(2p)-Ni(3d) orbital electronic coupling. The modulated Ni sites have weaker adsorption of carbonaceous intermediates, thus accelerating the UOR. This work provides a promising route for the design of high-activity UOR catalysts.

The development of high-performance, stable and platinum-free electrocatalysts for the hydrogen oxidation reaction (HOR) in alkaline media is crucial for the commercial application of anion exchange membrane fuel cells (AEMFCs). Ruthenium, as an emerging HOR electrocatalyst with a price advantage over platinum, still needs to solve the problems of low intrinsic activity and easy oxidation. Herein, Ru nanoparticles are anchored on the oxygen-vacancy-rich metalloid WO 2.9 by interfacial engineering to create abundant and efficient Ru and WO 2.9 interfacial active sites for accelerated HOR in alkaline media. Ru/WO 2.9 /C displays excellent catalytic activity with mass activity (8.29 A mg NM -1 ) and specific activity (1.32 mA cm NM -2 ), which are 2.5/3.3 and 21.8/8.3 times that of PtRu/C and Pt/C, respectively. Moreover, Ru/WO 2.9 /C exhibits excellent CO tolerance and operational stability. Experimental and theoretical studies reveal that the improved charge transfer from Ru to WO 2.9 in the metal/metalloid heterostructure significantly tune the electronic structure of Ru sites and optimize the hydrogen binding energy (HBE) of Ru. While, WO 2.9 provides abundant hydroxyl adsorption sites. Therefore, the equilibrium adsorption of hydrogen and hydroxyl at the interface of Ru/WO 2.9 will be realized, and the oxidation of metal Ru would be avoided, thereby achieving excellent HOR activity and durability., (© 2024 Wiley‐VCH GmbH.)

The electrochemical reduction of CO 2 to HCOOH is considered one of the most appealing routes to alleviate the energy crisis and close the anthropogenic CO 2 cycle. However, it remains challenging to develop electrocatalysts with high activity and selectivity towards HCOOH in a wide potential window. In this regard, Ag/Bi 2 O 2 CO 3 was prepared by an in situ electrochemical transformation from Ag/Bi 2 O 3 . The Ag/Bi 2 O 2 CO 3 catalyst achieves a faradaic efficiency (FE) of over 90% for HCOOH in a wide potential window between -0.8 V and -1.3 V versus the reversible hydrogen electrode (RHE). Moreover, a maximum FE of 95.8% and a current density of 15.3 mA cm -2 were achieved at a low applied potential of -1.1 V. Density functional theory (DFT) calculations prove that the high catalytic activity of Ag/Bi 2 O 2 CO 3 is ascribed to the fact that Ag can regulate the electronic structure of Bi, thus facilitating the adsorption of *OCHO and hindering the adsorption of *COOH. This work expands the in situ electrochemical derivatization strategy for the preparation of electrocatalysts.

This article briefly describes the imaging performance standards of the kilovolt X-ray image guidance system used in radiotherapy, analyzes the main aspects that should be considered in the image quality of X-IGRT system, and focuses on parameters that should be considered in the imaging performance evaluation criteria of the CBCT X-IGRT. The purpose is to sort out the imaging performance evaluation standards of kilovolt X-IGRT system, clarify the image quality requirements of X-IGRT equipment, and reach a consensus when evaluating the imaging performance of X-IGRT system.