双频高强度聚焦超声换能器应用研究进展

高强度聚焦超声(High Intensity Focused Ultrasound,HIFU)消融实体肿瘤已在临床治疗中展示出良好的应用前景。HIFU消融肿瘤技术由于其使靶区肿瘤组织瞬时升温至60℃以上,产生不可逆性凝固性坏死,同时不影响靶区外正常组织而被广泛应用。目前治疗用超声主要使用单频率高强度聚焦超声,但其临床应用的主要限制是靶区组织消融时间较长,靶区外正常组织损伤风险较大。缩短靶区组织消融时间,对于提高HIFU治疗效率,更好地应用于临床较为关键。在总结HIFU换能器的特性和影响HIFU治疗因素的基础上,综述了应用不同类型的双频HIFU换能器强空化和缩短靶区组织消融时间等方面的研究进展。     

基于双产品回收的C02驱采伴生气低温分馏工艺

针对某油田CO2驱采伴生气气质特性以及双产品回收指标的要求,运用HYSYS软件数值研究基于CO2-天然气双产品回收的三塔、四塔低温分馏工艺,分析乙烷回收塔塔底温度和原料气中CO2含量对两工艺CO2产品量、添加剂用量、工艺能耗的影响规律,并进行三塔/四塔工艺以及四塔工艺改进前后的对比分析.结果表明:三塔/四塔工艺的C02产量、添加剂用量以及比热耗均随乙烷回收塔塔底温度的升高而增大,比冷耗呈先减后增变化;随着原料气CO2浓度的增大,三塔/四塔工艺的CO2产品量增加,而添加剂用量/比冷耗/比热耗降低;四塔工艺改进后CO2产品量稍有降低,添加剂用量稍有增加,但比冷耗/比热耗平均降低14.4％/30.9％.结论认为,四塔工艺在总能耗、冷/热能耗及添加剂用量上都远低于三塔工艺,且CO2回收率高,改进后的四塔工艺则简化了工艺流程且节能效果更为显著.     

Recovering local equilibrium from three-dimensional compatible finite element solutions

We study the application to compressible and incompressible three-dimensional elasticity problems of the technique that we proposed in 2009 for the recovery of equilibrated stresses from compatible finite element solutions. The case of finite elements with linear displacement approximations, for which the partitioned systems of loads are not initially balanced in terms of rotational equilibrium, addressed in 2012, is also considered. The article includes a presentation of the implementation details, a study of the convergence in terms of the energy of the error, and a characterization of the solutions obtained.     

Two-Dimensional Superstructures of Silica Cages

Despite extensive studies on mesoporous silica since the early 1990s, the synthesis of two-dimensional (2D) silica nanostructures remains challenging. Here, mesoporous silica is synthesized at an interface between two immiscible solvents under conditions leading to the formation of 2D superstructures of silica cages, the thinnest mesoporous silica films synthesized to date. Orientational correlations between cage units increase with increasing layer number controlled via pH, while swelling with oil and mixed surfactants increase micelle size dispersity, leading to complex clathrate type structures in multilayer superstructures. The results suggest that a three-dimensional (3D) crystallographic registry within cage-like superstructures emerges as a result of the concerted 3D co-assembly of the organic and inorganic components. Mesoporous 2D superstructures can be fabricated over macroscopic film dimensions and stacked on top of each other. The realization of previously inaccessible mesoporous silica heterostructures with separation or catalytic properties unachievable via conventional bulk syntheses is envisioned.     

Cooperative Catalysis toward Oxygen Reduction Reaction under Dual Coordination Environments on Intrinsic AMnO3-Type Perovskites via Regulating Stacking Configurations of Coordination Units

It remains challenging for pure-phase catalysts to achieve high performance during the electrochemical oxygen reduction reaction to overcome the sluggish kinetics without the assistance of extrinsic conditions. Herein, a series of pristine perovskites, i.e., AMnO₃ (A = Ca, Sr, and Ba), are proposed with various octahedron stacking configurations to demonstrate the cooperative catalysis over SrMnO₃ jointly explored by experiments and first-principles calculations. Comparing with the unitary stacking of coordination units in CaMnO₃ or BaMnO₃, the intrinsic SrMnO₃ with a mixture of corner-sharing and face-sharing octahedron stacking configurations demonstrates superior activity (E_half-wave = 0.81 V), and charge–discharge stability over 400 h without the voltage gap (≈0.8 V) increasing in zinc–air batteries. The theoretical study reveals that, on the SrMnO₃(110) surface, the active sites switch from coordinatively unsaturated atop Mn (*OO, *OOH) to Mn–Mn bridge (*O, *OH). Therefore, the intrinsic dual coordination environments of Mn–O_corner and Mn–O_face enable cooperative modulation of the interaction strength of the oxygen intermediates with the surface, inducing the decrease of the *OH desorption energy (rate-limiting step) unrestricted by scaling relationships with the overpotential of ≈0.28 V. This finding provides insights into catalyst design through screening intrinsic structures with multiple coordination unit stacking configurations.     

High Security for De-Duplicated Big Data Using Optimal SIMON Cipher

Cloud computing offers internet location-based affordable, scalable, and independent services. Cloud computing is a promising and a cost-effective approach that supports big data analytics and advanced applications in the event of forced business continuity events, for instance, pandemic situations. To handle massive information, clusters of servers are required to assist the equipment which enables streamlining the widespread quantity of data, with elevated velocity and modified configurations. Data deduplication model enables cloud users to efficiently manage their cloud storage space by getting rid of redundant data stored in the server. Data deduplication also saves network bandwidth. In this paper, a new cloud-based big data security technique utilizing dual encryption is proposed. The clustering model is utilized to analyze the Deduplication process hash function. Multi kernel Fuzzy C means (MKFCM) was used which helps cluster the data stored in cloud, on the basis of confidence data encryption procedure. The confidence finest data is implemented in homomorphic encryption data wherein the Optimal SIMON Cipher (OSC) technique is used. This security process involving dual encryption with the optimization model develops the productivity mechanism. In this paper, the excellence of the technique was confirmed by comparing the proposed technique with other encryption and clustering techniques. The results proved that the proposed technique achieved maximum accuracy and minimum encryption time.     

HARQ Optimization for PDCP Duplication-Based 5G URLLC Dual Connectivity

Packet duplication (PD) with dual connectivity (DC) was newly introduced in the 5G New Radio (NR) specifications to meet the stringent ultra reliable low latency communication (URLLC) requirements. PD technology uses duplicated packets in the packet data convergence protocol (PDCP) layer that are transmitted via two different access nodes (ANs) to the user equipment (UE) in order to enhance the reliability performance. However, PD can result in unnecessary retransmissions in the lower layers since the hybrid automatic retransmission request (HARQ) operation is unaware of the transmission success achieved through the alternate DC link to the UE. To overcome this issue, in this paper, a novel duplication-aware retransmission optimization (DRO) scheme is proposed to reduce the resource usage induced by unnecessary HARQ retransmissions. The proposed DRO scheme can minimize the average channel use while satisfying the URLLC requirements. The proposed DRO scheme derives the optimal HARQ retransmission attempts for different ANs by solving a nonlinear integer programming (NLIP) problem. The performance of the proposed DRO scheme was evaluated using MATLAB simulation and is compared to the existing 5G HARQ support schemes. The simulations results show that the proposed DRO scheme can provide a 14.71% and 15.11% reduced average channel use gain compared to the selective data duplication upon failure (SDUF) scheme and latency-aware dynamic multi-connectivity algorithm (LADMA) scheme, respectively, which are the existing 5G PD schemes that use HARQ.     

双重干预及产能约束下的闭环供应链决策研究

为了研究制造商产能约束下政府的环境税和回收补贴双重干预对制造商和零售商决策的影响,并为政府的干预政策提供建议,构建了由一个制造商和零售商组成的闭环供应链模型,并运用Stakelberg博弈和逆向归纳法对模型进行求解分析。结果发现,当政府向制造商征收的环境税达到特定水平时,能够使制造商充分履行环境责任,但会对制造商和供应链整体经济效益和回收量造成损失,而政府的回收补贴能够弥补这些损失;回收补贴的增加对新产品的生产和销售造成冲击;再制造产能系数的增加会对新产品的生产和销售产生有利影响,对再制品的生产和销售产生不利影响。     

Atomically Dispersed Fe/N4 and Ni/N4 Sites on Separate-Sides of Porous Carbon Nanosheets with Janus Structure for Selective Oxygen Electrocatalysis

Dual single atoms catalysts have promising application in bifunctional electrocatalysis due to their synergistic effect. However, how to balance the competition between rate-limiting steps (RDSs) of reversible oxygen reduction and oxygen evolution reaction (OER) and fully expose the active centers by reasonable structure design remain enormous challenges. Herein, Fe/N₄ and Ni/N₄ sites separated on different sides of the carbon nanosheets with Janus structure (FeNi_jns/NC) is synthesized by layer-by-layer assembly method. Experiments and calculations reveal that the side of Fe/N₄ is beneficial to oxygen reduction reaction (ORR) and the Ni/N₄ side is preferred to OER. Such Janus structure can take full advantage of two separate-sides of carbon nanosheets and balance the competition of RDSs during ORR and OER. FeNi_jns/NC possesses superior ORR and OER activity with ORR half-wave potential of 0.92 V and OER overpotential of 440 mV at J = 10 mA cm⁻². Benefiting from the excellent bifunctional activities, FeNi_jns/NC assembled aqueous Zn–air battery (ZAB) demonstrates better maximum power density, and long-term stability (140 h) than Pt/C+RuO₂ catalyst. It also reveals superior flexibility and stability in solid-state ZAB. This work brings a novel perspective for rational design and understanding of the catalytic mechanisms of dual single atom catalysts.     

A Full‐Spectrum Metal‐Free Porphyrin Supramolecular Photocatalyst for Dual Functions of Highly Efficient Hydrogen and Oxygen Evolution

A full‐spectrum (300–700 nm) responsive porphyrin supramolecular photocatalyst with a theoretical solar spectrum efficiency of 44.4% is successfully constructed. For the first time, hydrogen and oxygen evolution (40.8 and 36.1 µmol g^?1 h^?1) is demonstrated by a porphyrin photocatalyst without the addition of any cocatalysts. The strong oxidizing performance also presents an efficient photodegradation activity that is more than ten times higher than that of g‐C₃N₄ for the photodegradation of phenol. The high photocatalytic reduction and oxidation activity arises from a strong built‐in electric field due to molecular dipoles of electron‐trapping groups and the nanocrystalline structure of the supramolecular photocatalyst. The appropriate band structure of the supramolecular photocatalyst adjusted via the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of the porphyrin gives rise to thermodynamic driving potential for H₂ and O₂ evolution under visible light irradiation. Controlling the energy band structure of photocatalysts via the ordered assembly of structure‐designed organic molecules could provide a novel approach for the design of organic photocatalysts in energy and environmental applications.