基于CFD的具有首翼的新型飞翔形式AUV升力和阻力估计:对阻力极曲线和推力估计的见解

To achieve hydrodynamic design excellence in Autonomous Underwater Vehicles(AUVs)largely depends on the accurate prediction of lift and drag forces.The study presents Computational Fluid Dynamics(CFD)-based lift and drag estimations of a novel torpedo-shaped flight-style AUV with bow-wings.The horizontal bow-wings are provided to accommodate the electromagnetic arrays used to perform the cable detection and tracking operations near the seabed.The hydrodynamic performance of the AUV due to addition of these horizontal bow-wings is required to be investigated,particularly at the initial design stage.Hence,CFD techniques are employed to compute the lift and drag forces observed by the flight-style AUV,maneuvering underwater at different angles of attack and varying speeds.The Reynolds-Averaged Navier-Stokes Equations(RANSE)closure is achieved by employing the modified k-ϵ model and Two-Scale Wall Function(2-SWF)approach is used for boundary layer treatment.Further,the study also highlights the unique mesh refinement and solution-adaptive meshing techniques to perform the CFD simulations in Solidworks Flow Simulation(SWFS)environment.The drag polar curve for flight-style AUV with and without bow-wings is generated using the computed lift and drag coefficients.The curve provided essential insights for achieving hydrodynamically efficient and optimized AUV design.From the drag polar curve,it is revealed that due to horizontal bow-wings,the flight-style AUV is capable to generate higher lift with less drag and thus,it gives better lift-to-drag ratio compared to the AUV without bow-wings.Moreover,simulated results of axial drag observed by the AUV have also been compared with free-running experimental results and are found in good agreement.

单晶金红石型TiO_2纳米棒的湿法合成(英文)

用TiO2粉末、NaOH和蒸馏水为原料合成金红石型TiO2纳米棒。XRD和FESEM分析表明,制备的样品为单晶且无杂质,其平均粒径约为40 nm。当样品于600°C退火2 h后,FESEM观察发现生成了TiO2纳米棒。XRD分析表明纳米棒为单晶。纳米棒表面光滑,其长约为1μm,直径约为80 nm。紫外和拉曼光谱研究表明,所制备样品的能带间隙为3.40 eV。

烧结温度对La_(0.6)Ca_(0.4)MnO_3结构、磁性和磁致热效应的影响(英文)

研究了烧结温度对La0.6Ca0.4MnO3的结构、磁转变和磁熵的影响。观察表明,该化合物属于具有Pnma空间群的斜方晶系结构,不含任何杂质。研究烧结温度对居里温度(TC)的影响,发现提高烧结温度,TC稍有增大。磁致热效应研究显示,随着烧结温度的变化,磁熵会发生显著的变化。在外加磁场为3 T、烧结温度为1300°C时,相对冷却能(RCP)为89 J/kg。因此,该化合物可以考虑作为在室温附近或低于室温的潜在磁制冷材料。

Bioinspired Multi-material Polyjet-printed Frog Robot for Synchronous and Asynchronous Swimming

This paper proposes the bioinspired soft frog robot. All printing technology was used for the fabrication of the robot. Polyjet printing was used to print the front and back limbs, while ultrathin filament was used to print the body of the robot, which makes it a complete soft swimming robot. Dual thrust generation approach has been proposed by embedding the main muscle and antagonistic muscle in all the limbs, which enables it to attain high speed (18 mm/s), significant control to swim in dual mode (synchronous and asynchronous modes). To achieve the swimming motion of frog, four SMA (BMF 300) muscle wires were used. The frog robot is named as (FROBOT). The hind limbs are 60 mm long and 10 mm thick on average, while the front limbs are 35 mm long and 7 mm thick. Model-based design and rigorous analysis of the dynamics of real frogs have allowed FROBOT to be developed to swim at a level that is remarkably consistent with real frogs. Electrical and mechanical characteristics have been performed. In addition, the test data were further processed using TRACKER to analyze angle, displacement and velocity. FROBOT (weighs 65 g) can swim at different controllable frequencies (0.5–2 Hz), can rotate in any direction on command from custom built LabVIEW software allowing it to swim with speed up to 18 mm/s on deep water surface (100 cm) with excellent weight balance.

Multi-material Bio-inspired Soft Octopus Robot for Underwater Synchronous Swimming

Inspired by the simple yet amazing morphology of the Octopus, we propose the design, fabrication, and characterization of multi-material bio-inspired soft Octopus robot (Octobot). 3D printed molds for tentacles and head were used. The tentacles of the Octobot were casted using Ecoflex-0030 while head was fabricated using relatively flexible material, i.e., OOMOO-25. The head is attached to the functionally responsive tentacles (each tentacle is of 79.12 mm length and 7 void space diameter), whereas Shape Memory Alloy (SMA) muscle wires of 0.5 mm thickness are used in Octobot tentacles for dual thrust generation and actuation of Octobot. The tentacles were separated in two groups and were synchronously actuated. Each tentacle of the developed Octobot contains a pair of SMA muscles (SMA-α and SMA-β). SMA-α muscles being the main actuator, was powered by 9 V, 350 mA power supply, whereas SMA-β was used to provide back thrust and thus helps to increase the actuation frequency. Simulation work of the proposed model was performed in the SolidWorks environment to verify the vertical velocity using the octopus tentacle actuation. The design morphology of Octobot was optimized using simulation and TRACKER software by analyzing the experimental data of angle, displacement, and velocity of real octopus. The as-developed Octobot can swim at variable frequencies (0.5–2 Hz) with the average speed of 25 mm/s (0.5 BLS). Therefore, the proposed soft Octopus robot showed an excellent capability of mimicking the gait pattern of its natural counterpart.

Green Synthesis of Silver Nanoparticles and Their Reduced Graphene Oxide Nanocomposites as Antibacterial Agents:A Bio-inspired Approach

In this paper, silver nanoparticles(Ag NPs) and Ag NPs/reduced graphene oxide(RGO) nanocomposites were prepared using lemon juice under microwave irradiation(MWI) and UV light irradiation. Ag NPs with face-centered cubic structure RGO peaks were observed by X-ray diffraction. The UV–Vis spectrum showed modifications in the absorption peaks of the Ag NPs with the concentration of the precursor solution and irradiation time, and the optimized condition was obtained for 20 min MWI and 60 s of UV light. Raman analysis confirmed the presence of RGO as D and G bands in the spectrum. Transmission electron microscopy analyses confirmed that the Ag NPs of size ranging from 3 to 8 nm were anchored onto the RGO sheets. The antibacterial properties of the Ag NPs/RGO nanocomposites were investigated using gram-negative bacteria. The results revealed that Ag NPs/RGO nanocomposites consisting of approximately 5 wt% Ag NPs can achieve antibacterial performance similar to that of neat Ag NPS. This method can be useful for the applications of Ag NPs-based nanocomposites, where minute amount of silver will be utilized.

Critical Success Factors to Improve the Game Development Process from a Developer＇s Perspective

软件比赛发展工业的生长是庞大的并且一天一天地正在获得重要性。这生长在游戏开发社区上强加严重压力和很多个问题和挑战。游戏开发是复杂进程，并且一种重要游戏开发选择是认为开发者观点由改进游戏开发进程生产好的品质软件游戏。这研究的目的是在软件比赛成功作为一个因素提供开发者尺寸的更好的理解。它在产生游戏的质量上主要集中于关键开发者因素的效果的实验调查在软件游戏开发进程上并且最后。量的调查被开发并且进行了为一个提高的比赛发展过程识别关键开发者因素。为这研究，发达调查被用来测试研究模型和假设。结果提供游戏开发组织必须处理多重关键因素仍然保持竞争并且在软件游戏工业处理高压力的证据。这篇论文的主要贡献是以经验为主地在比赛发展过程上调查关键开发者因素的影响。