Buckling Properties of Water-Drop-Shaped Pressure Hulls with Various Shape Indices Under Hydrostatic External Pressure

The water-drop-shaped pressure hull has a good streamline,which has good application prospect in the underwater observatory.Therefore,this study conducted analytical,experimental and numerical investigation of the buckling properties of water-drop-shaped pressure hulls under hydrostatic pressure.A water-drop experiment was conducted to design water-drop-shaped pressure hulls with various shape indices.The critical loads for the water-drop-shaped pressure hulls were resolved by using Mushtari’s formula.Several numerical simulations including linear buckling analysis and nonlinear buckling analysis including eigenmode imperfections were performed.The results indicated that the critical loads resolved by Mushtari's formula were in good agreement with the linear buckling loads from the numerical simulations.This formula can be extended to estimate the buckling capacity of water-drop-shaped pressure hulls.In addition,three groups of pressure hulls were fabricated by using stereolithography,a rapid prototyping technique.Subsequently,three groups of the pressure hulls were subjected to ultrasonic measurements,optical scanning,hydrostatic testing and numerical analysis.The experimental results were consistent with the numerical results.The results indicate that the sharp end of the water-drop-shaped pressure hulls exhibited instability compared with the blunt end.This paper provides a new solution to the limitations of experimental studies on the water-drop-shaped pressure hulls as well as a new configuration and evaluation method for underwater observatories.

Improved spatio-temporal alignment measurement method for hull deformation

In this paper,an improved spatio-temporal alignment measurement method is presented to address the inertial matching measurement of hull deformation under the coexistence of time delay and large misalignment angle.Large misalignment angle and time delay often occur simultaneously and bring great challenges to the accurate measurement of hull deformation in space and time.The proposed method utilizes coarse alignment with large misalignment angle and time delay estimation of inertial measurement unit modeling to establish a brand-new spatiotemporal aligned hull deformation measurement model.In addition,two-step loop control is designed to ensure the accurate description of dynamic deformation angle and static deformation angle by the time-space alignment method of hull deformation.The experiments illustrate that the proposed method can effectively measure the hull deformation angle when time delay and large misalignment angle coexist.

Optimized Adsorption of Small and Medium Molecules by a Biosorbent Based on Hevea Hulls

In the context of the recovery of agricultural waste, many researches have focused on the preparation of adsorbents from natural waste from fruit trees, egg shells, palm waste or sawdust. This work aims to optimize the preparation of a biosorbent from rubber hulls by studying its ability to adsorb small and medium molecules. The influence of parameters such as drying temperature (X1), particle size (X2), stirring time (X3) and sodium hypochloride mass (X4) was studied. The results indicate that the model used for biosorbent optimization on methylene blue and iodine index is significant. In addition, this model has greater adsorption capabilities on small molecules than with large molecules. Statistical analysis of the data shows that temperature is the most influential factor in the adsorption of small molecules. On the other hand, particle size has a significant influence on the adsorption of large molecules. The optimum biosorbent preparation values are 1.0 for drying temperature (X1), −1.0 for biosorbent grain size (X2), 1.0 for stirring time (X3) and 1.0 for sodium hypochloride mass (X4).

Experimental and numerical analysis on suitability of S-Glass-Carbon fiber reinforced polymer composites for submarine hull

Suitability of S-Glass/carbon fiber reinforced polymer composite for submarine hull subjected to hydrostatic pressure has been investigated in the present study.Metallic materials have raised concerns owing to their decomposition due to low resistance towards salinity and hence polymer composites have been explored to showcase their mechanical stability to withstand transverse and impact loads.To this end,the mechanical properties of S-Glass/carbon fiber reinforced polymer composite were experimentally investigated and higher specific strength and stiffness of the composite in comparison to many metallic materials used for submarine hull were reported.The obtained experimental values were used for the static and dynamic crash analysis of the bow,stern and foil through Finite Element Analysis(FEA);where depth of travel was varied from sea surface level of 0-7000 m.Submarine assembly was later developed with the optimum shape and thickness of each part.We also report the nonlinear crash analysis upon impact at velocity ranging from 3 to 21 m/s.Besides,kinetic energy,acceleration peak and internal energy in struck submarine revealed that travel depth 1750 m and 3500 m is recommendable,more particularly,crash safety factor of the submarine is found to be within limit when submarine encounters crash at 1750 m.

Novel Gluten-Free Amaranth and Oat Flour Cookies Fortified with Soybean Hulls

Soybean hulls, an abundant byproduct of soybean processing, contain rich phytochemicals, fibers, proteins, and minerals. Currently soybean hulls are primarily used as animal feeds. For value-added soybean hull utilization, 25% soybean hulls were substituted for amaranth or whole oat flour (WOF) in novel gluten-free cookies. Composition, nutritional values, water-holding capacities, correlation between properties, and pasting and rheological properties of soybean hulls, amaranth, and WOF were appraised in comparison to wheat flour. Water loss, cookie texture, and geometrical properties of the cookies were examined. The results disclosed that soybean hulls, amaranth and WOF contain higher protein content, minerals, fiber, special amino acids, and critical vitamins (C and K) than wheat flour. Considerably higher total amino acid content was found in soybean hulls (18.33%) than wheat flour (12.77%). Water-holding capacities increased by replacing amaranth and WOF with soybean hulls. Soybean hulls exhibited higher rheological elastic properties than amaranth, WOF and wheat flours. The soybean hulls utilized in amaranth or WOF cookies greatly improved their nutritional value, the water retention and moisture content along with acceptable physical properties when compared to wheat flour cookies. This study explored the feasibility and potential of utilizing soybean hulls with amaranth and WOF in gluten-free bakery products and other food applications.

Evaluation of Physicochemical Parameters of Biosorbents Produced from Groundnut Hull Using Microwave Assisted Irradiation Method

Samples of ground nut hull were converted to biosorbents using microwave assisted method [groundnut hull treated with hydrogen peroxide (HP-GH), groundnut hull treated with distilled water (W-GH) and raw groundnut hull (R-GH)]. The biosorbents were further characterized using physicochemical procedures (pH dependence, bulk density, surface area, ash content, and volatile matter, moisture content). The results show that HP-GH has pH = 8.9, W-GH pH = 8.4 and R-GH pH = 8.5 which is an indication that all the biosorbents have the appropriate pH values for the uptake of cationic species within aqueous systems. Surface area analysis revealed that HP-GH has the largest surface area (74.20 m2·g-1) while W-GH and R-GH have surface area values of 29.40 m2·g-1 and 21.40 m2·g-1 respectively. This suggests that modification of raw groundnut hull biomass with hydrogen peroxide possibly instigated delignification of the biomass which resulted in increased surface area for HP-GH. Results from Bulk density analysis also confirm the data obtained from surface area analysis. Accordingly, R-GH displayed the highest bulk density followed by W-GH with HP-GH showing the least bulk density. The variation in pH values among the biomass used in this study may be explained by the variation in their ash content as well because pH and ash content are positively correlated. Hence, HP-GH with a pH = 8.9 has high ash content (117.31%), W-GH with pH = 8.4 has 97.93% ash content and R-GH with pH = 8.5 has 94.26% ash content. Results from moisture content analysis show that HP-GH (99.95%), W-GH (99.97%) and R-GH (99.89%) may necessitate exposure of the biosorbents to moderate heat before use. The results obtained from this study suggest that modification of ground nut hull with either distilled water or Hydrogen peroxide by means of microwave irradiation improves physicochemical properties which may perhaps increase the adsorption capacity of the biomass.

一种基于流形的机械臂动作构型知识压缩表达方法

针对在机械臂分拣任务中,存在物体形状各异、大小不一、训练神经网络成本过高的问题,提出一种基于流形空间的机械臂快速分拣方法。通过自主设计的一款简易实验装置模拟代替机械臂进行实验。对高维数据进行压缩,结合三维快速凸包求解算法,对体积大小不同的同类物体的流形空间进行分割,以凸包形式将稳定性较高的点集包裹起来。实验结果表明,体积大小不同的同类物体的高稳定流形子空间是一致的。该方法可以通过对一种物体的流形子结构进行尺度放缩,得到不同大小的同类物体的高稳定分拣区域,用于生成高效、可靠的机械臂分拣任务中的6D位姿构型,以提高分拣作业的工作效率。

基于机器视觉的芯片字符区域分割和定位算法

芯片表面的字符对分选具有重要意义,对字符的定位是分选工作的关键步骤。为了提高分选工作定位效率和定位精度,提出了一种基于改进的区域生长算法和凸包检测算法分割和定位芯片表面字符区域方法。首先,对采集图像进行预处理操作,利用改进的Canny算法获取无干扰图像边缘,将图像边缘作为区域生长法的种子点并以图像自适应阈值作为生长准则分割图像,使用最大内接矩形算法粗定位字符区域;其次,采用Harris角点检测算法获取字符角点分布位置;最后,筛选角点并提取关键点,利用一种改进的凸包检测算法定位字符区域。经过实验验证,所设计的算法能够完整的分割和定位芯片表面字符区域,定位精度和效率较原有方法提升5.3%和15.4%,满足实际工业生产的要求。

破冰冲击载荷下船体振动响应分析

为考察破冰船船体在破冰冲击载荷下的振动响应特征,利用环向裂纹法对“雪龙2”号破冰船在典型破冰工况下的破冰冲击载荷进行预报,并通过傅里叶变换把破冰冲击载荷转换为频域载荷,进一步建立了“雪龙2”号破冰船全船有限元模型,进行破冰冲击载荷下全船振动响应计算分析。结果表明,破冰工况下,破冰冲击载荷对船体结构低频振动响应(5 Hz以下)贡献很大,容易引起船体梁振动、雷达桅结构振动等,对船体板格、加强筋、板架等船体结构的局部振动水平贡献相对较小。

基于连续介质损伤力学的钛合金耐压球壳极限强度分析

本文在连续介质损伤力学理论框架下,以深海载人装备耐压球壳结构为研究对象,开展Bonora损伤模型适用性研究。首先,设计TA31钛合金加载卸载试验,依据试验结果,分析Bonora模型参数对材料应力应变响应的影响规律;随后,提出一种模型参数校准方法,依据试验数据确定TA31钛合金的模型参数;最后,将Bonora模型通过VUMAT子程序的形式嵌入到有限元软件中,开展钛合金球壳结构的极限强度分析,并与传统方法进行对比。研究结果表明,在耐压球壳极限强度分析中,引入Bonora模型可以准确模拟耐压球壳结构的失效模式和破坏压力。该模型在材料本构关系中考虑了屈服强度、抗拉强度以及最大塑性应变的影响,结构失效的物理意义更加明确,对材料性能的优化与提升具有指导意义。

基于准静态法的船体梁极限强度试验设计方法

为了应对采用传统试验法求解船体梁极限强度问题时存在的成本较高的情况,有必要在开展试验之前进行预设计。针对船体梁极限强度试验预设计问题,采用四点弯曲理论对船体梁极限强度开展试验设计,给出具体的试验工装设计方案和加载方案,并采用准静态法分析该方案在中拱状态下的极限强度。将采用该方法所得计算结果与理想状态下的数值计算结果相对比对比,结果发现误差仅为0.08%,表明该试验设计方案可靠、可行。研究结果可为船体梁极限强度试验的开展提供参考。

基于DeepLabv3+的船体结构腐蚀检测方法

利用图像识别方法对无人机、机器人所采集的实时图像开展船体结构腐蚀检测,可有效提高检验检测效率和数字化、智能化水平,具有极大的应用价值和潜力,将改变传统的船体结构检验检测方式。提出一种基于DeepLabv3+的船体结构腐蚀检测模型,通过收集图像样本并进行三种腐蚀类别的分割标注,基于DeepLabv3+语义分割模型进行网络的训练,预测图片中腐蚀的像素点类别和区域,模型在测试集的精准率达到52.92%,证明了使用DeepLabv3+检测船体腐蚀缺陷的可行性。

基于可视化技术的船体制造数据管控方法

为解决传统船体建造过程中存在生产数据记录与管理混乱、生产数据分析不深入,工作人员缺乏现场有效的决策支持与生产指导等问题,通过以制造阶段为导向对船体制造数据流的分析,构建相关工序的指标关系模型与船体制造数据库;基于Echarts、three.js等可视化技术与B/S架构将船体产品模型及指标模型集成到船体制造管控系统,实现产品模型信息与数据模型信息的统一呈现,以及船体制造数据的查询、修改、录入等功能,达到辅助管理人员现场生产决策的效果。

一种自升式风电安装船的主船体结构总强度设计

本文借助三维有限元直接计算设计技术,结合依托自升自航式一体化海上风电安装平台自身特有的结构布置、任务使命,从船体梁剖面特性、船体梁剖面载荷出发,详细阐述四桩腿式风电安装平台的开孔群式主船体结构总强度设计流程和方法,为海上风电安装平台的大型化、平台主体结构的规范化和轻量化设计研发提供基础。

潜艇舷侧阀与管路阀件的不同技术特征辨析

潜艇舷侧阀为潜艇的关键件。与管路阀件服务于管路系统功能不同,潜艇舷侧阀用于保障潜艇生命力和潜艇安全性。本文对潜艇舷侧阀与管路阀件的传统结构样式进行对比,分析潜艇舷侧阀与管路阀件的技术要点差异,阐述潜艇通海通舷外系统舷侧阀的基本指标体系和核心要点,提出一体化舷侧阀(通海阀与二道闭锁阀的组合)是潜艇舷侧阀的进化结构型式,最后对特殊型式的潜艇舷侧阀的设计注意事项进行总结。本文通过研究、对比、分析,形成了系统性的潜艇舷侧阀的技术要素,对于开展新型舷侧阀特别是大潜深潜艇舷侧阀的研发具有重要指导意义。

基于空程和方向的船体装配线划线路径优化

为解决复杂船体装配线划线路径优化时精度低和收敛速度慢的问题,进而提高数控划线枪的作业效率,提出了基于空程和方向的船体装配线划线路径的调参免疫优化。首先以装配线的划线顺序和划线方向建立目标函数;然后借鉴凸透镜虚实成像原理设计了新免疫优化算法,基于进化代数和种群浓度自适应调节交叉和变异概率,并引入疫苗操作实现了船体装配线划线路径求解;最后基于马尔科夫链理论证明了免疫优化算法的收敛性。六组高维函数测试结果表明,与遗传算法、免疫遗传算法和自适应改进遗传算法相比,所提算法实现了100%寻优,且最小收敛代数、平均收敛代数、迭代代数标准差分别平均减少了29.63%、28.96%和18.33%。四种船体结构的装配线划线路径优化测试结果表明,相比起其他三种算法,所提算法的路径规划性能最佳,其最小值和平均值分别平均减少了1.38%和2.39%,平均收敛代数和迭代代数标准差分别平均减少了17.19%和13.08%,从而进一步验证了船体装配线划线路径调参免疫优化的有效性和优越性。

碳含量对船体钢耐蚀性的影响

通过干湿循环腐蚀试验模拟热带海洋大气环境,采用光学显微镜、扫描电子显微镜、X射线衍射、动电位极化曲线、阻抗谱测试等表征手段,研究了不同碳含量对船体钢耐蚀性的影响。结果表明,降碳会减少钢中珠光体含量,使腐蚀产物中具有稳定结构的α-FeOOH的比例增加,从而提高基体的电位,并使得腐蚀产物膜层电阻和电荷转移电阻增大,形成粘附性好、稳定、致密的锈层,表现出良好的耐蚀性。

侧体尺度对小水线面三体船纵向运动影响研究

小水线面三体船主、侧体尺度相差较大,因此,理论上侧体尺度具有无数种方案。目前,多数学者侧重于对侧体位置的研究,而对小水线面三体船侧体尺度对其水动力性能影响的研究还不够广泛。采用基于势流理论的AQWA软件进行数值模拟计算。首先,为确保计算过程中参数设置的准确性,对AQWA软件计算船舶耐波性的可靠性进行验证;然后,研究系列傅汝德数Fr下侧体尺度变化对小水线面三体船的耐波性响应。结果显示,在波长船长比变化时,垂荡纵摇RAO随侧体尺度改变产生了非单调的变化。不同航速下,垂荡和纵摇性能最优的侧体尺度不一致。综合所有航速考虑,L_(c)/L为0.3和0.35的侧体方案耐波性能较好。研究结果可为小水线面三体船的设计提供借鉴。

基于凸包算法的极端运行方式提取方法

在电力系统规划与运行的安全稳定计算中,一般选择对安全稳定最不利的运行方式进行校验,但随着新能源渗透率的增加,电网越发复杂多变,人工选择场景主观性较强,针对此问题,提出了一种基于快速凸包算法的极端运行方式提取,从而满足场景选取进行安全校核需求。从电源规划、发输电协调规划两个角度,考虑发电充裕性、火电爬坡需求、网络传输安全3个方面,分析影响规划的极端运行方式;基于凸包算法分别从上述3个方面构建坐标系进行极端运行方式提取;采用中国西北地区电网为算例进行极端运行方式提取,并与基于K-means算法的极端场景提取做对比,结果表明:所提方法能为场景选取提供有效数据支撑,满足电网规划要求。

循环半群与一些特殊半群直积的平移壳

研究了循环半群和矩形带以及一种特殊的毕竟正则半群直积的平移壳;证明了循环半群与矩形带的直积的平移壳和这两个半群的平移壳的直积是同构的;同时,证明了循环半群与特殊的毕竟正则半群的直积的平移壳和这两个半群的平移壳的直积也是同构的.