Frontogenesis and Frontolysis of a Cold Filament Driven by the Cross-Filament Wind and Wave Fields Simulated by a Large Eddy Simulation

The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are studied.The results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow fields.The lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.

Simple procedure for assessing diffuse subarachnoid hemorrhage successfully created using filament perforation method in mice

The murine model of subarachnoid hemorrhage(SAH)is a valuable experimental tool for investigating molecular and cellular mechanisms,and the endovascular filament perforation technique can be used to simulate prominent pathophysiological features observed after human SAH;however,current validation methods for assessing an appropriate SAH model are limited.Here,we introduce a simple procedure for se-lecting a mouse model of diffuse SAH.SAH was induced in 24 mice using a standard filament perforation method.After confirming survival at 24 h,SAH was scored 0-1 based on T2*-weighted images on whole-brain magnetic resonance imaging(MRI)and visual surveillance of the cisterna magna(CM)through the dura mater.The CM-based SAH grading correlated well with a reference parameter defined by extracted brain(r^(2)=0.53,p<0.0001).The receiver operating characteristic curve revealed a sensi-tivity of 85%and a specificity of 91%for detecting diffuse SAH,with a similar area under the curve(0.89±0.06[standard error of the mean])as the MRI-based grading(0.72±0.10,p=0.12).Our data suggest that confirming an SAH clot in the CM is a valuable way to select a clinically relevant diffuse SAH model that can be used in future experimental studies.

Strain-Rate Dependency of a Unidirectional Filament Wound Composite under Compression

This article presents the results of experimental studies concerning the dynamic deformation and failure of a unidirectional carbon fiber reinforced plastic(T700/LY113)under compression.The test samples were manufactured through the filament winding of flat plates.To establish the strain rate dependencies of the strength and elastic modulus of the material,dynamic tests were carried out using a drop tower,the Split Hopkinson Pressure Bar method,and standard static tests.The samples were loaded both along and perpendicular to the direction of the reinforcing fiber.The applicability of the obtained samples for static and dynamic tests was confirmed through finite elementmodeling and the high-speed imaging of the deformation and failure of samples during testing.As a result of the conducted experimental studies,static and dynamic stress-strain curves,time dependencies of deformation and the stress and strain rates of the samples during compression were obtained.Based on these results,the strain rate dependencies of the strength and elasticity modulus in the strain rate range of 0.001-6001/s are constructed.It is shown that the strain rate significantly affects the strength and deformation characteristics of the unidirectional carbon fiber composites under compression.An increase in the strain rate by 5 orders of magnitude increased the strength and elastic modulus along the fiber direction by 42%and 50%,respectively.Perpendicular loading resulted in a strength and elastic modulus increase by 58%and 50%,respectively.The average strength along the fibers at the largest studied strain rate was about 1000MPa.The obtained results can be used to design structural elements made of polymer composite materials operating under dynamic shock loads,as well as to build models of mechanical behavior and failure criteria of such materials,taking into account the strain rate effects.

Rapid Preparation of Filamentous Fungal DNA for PCR Analysis by Ultrasonic Treatment

A simple method to prepare of DNA template suitable for PCR amplification from filamentous fungi will be valuable for improving experimental efficiency.Here,a method was developed which just needed ultrasonic treatment of the mycelium at usual condition,and the produced solution could directly be used as DNA template for internal transcribed spacer(ITS)amplification successfully.The PCR could be improved by additional treatment of 60℃water baths,but was not centrifugation.When the template amount was 0.5-2μL and the ultrasonic time was 7-11 min,there was no distinctly influences on PCR.The method was commonly used for M.purpureus,I.cicadae,Lentinula sp.,Flammul sp.and Dictyophora sp.etc.to detect target sequences of ITS,hygromycin resistance gene(Hyg),CRISPR-associated protein 9(Cas9),Citrinin gene C(CtnC),Citrinin gene D(CtnD),large subunit rRNA gene(NL),and so on.The method could provide a simple,rapid,safe and economic approach to prepare the DNA template for large-scale PCR of the special filamentous fungi materials.

Development and Evaluation of Recycled Polypropylene and Bean Pod Powder Composite Biomaterial for Fused Filament Fabrication

Approximately 450 million tons of plastic and agricultural waste are produced each year in the world. Only a small portion of this plastic waste is recycled, and a small portion of this agricultural waste is used as fuel or fertilizer, and the rest of this waste is left in the environment or is burned, resulting in environmental and air pollution. For proper disposal, plastic and agricultural waste can be used in the manufacture of composites as raw materials. In this study, we had evaluated the use of bean pod powder (BPp) was used as natural reinforcing filler in recycled polypropylene (rPP) based composites. BPp/rPP composite filaments were developed using the extrusion method and the samples were printed by Fused Filament Fabrication (FFF). Composites with rPP matrix containing different weight fractions of BPp (5%, 10% and 15%) were fabricated to observe and compare the mechanical properties (tensile, flexural, and compressive strength) of the filament composites. In addition, the filament surface was analyzed for roughness and particle size of bean pod powder. The results established that BPp/rPP composites exhibited better tensile, flexural, and compressive strength than rPP and pure PP. By adding 5 wt% BPp, the tensile strength of rPP increased from 20.4 MPa to 22.8 MPa. The highest flexural strength (15.05 MPa) was obtained at 5 wt% BPp among all composites and the highest compressive strength (24.5 MPa), was obtained at 10 wt% BPp. Therefore, it can be concluded that by carefully selecting the ratio of BPp to bean pod powder, it is therefore possible to positively influence the mechanical properties of the resulting composite.

Study on the Presence of Filament Yarn in Jamdani Saree in Bangladesh

Jamdani weaving is one of the oldest heredities of Bangladesh. From the beginning 100% cotton yarn was used to produce high quality jamdani saree. The weavers were the finest with weaving skills. Higher yarn count yarns were used to weave the jamdani saree. In course of time at present manmade fibres are also used to produce jamdani saree. The use of filament yarn may have eased the manufacturing difficulties, but the jamdani saree is missing its originality without 100% cotton. In this project, random jamdani saree sample was collected to identify the fibre composition. Samples of filament were also collected from the manufacturer and tested. It was evident that instead of cotton yarn in warp and weft silk and polyester filament yarn were used.

The Kinematics Performance of Self-Propelled Full Freedom Filament in Wakes of Flow around Cylinder

In vortex streets, the kinematics performance of self-propelled full freedom filament is closely related to the length and the position of filaments in the flow field. In this paper, the changes of passive propulsion velocity and pressure of full-degree-of-freedom filaments after cylindrical wake were analyzed by 15 sets of experiments when the length and position of filaments were changed. The results show that the propulsive velocity of the filament, it approximately increases first and then decreases with the filament length increasing, and the further away from the center of the cylinder, the smaller the propulsive velocity of the filament. In addition, the longer the filament length and the further it is from the center of the cylinder, the lower the pressure around the filament. Experiments show that filaments without energy input can obtain energy from the surrounding flow field to maintain self-propelled motion. Studying the influence of length and position on the kinematics of filaments is helpful to provide a reference for revealing the hydrodynamic mechanism on passive propulsion process and developing low resistance energy harvesting device in swimming fish movement.

Recycled, Bio-Based, and Blended Composite Materials for 3D Printing Filament: Pros and Cons—A Review

In recent years, additive manufacturing (AM), known as “3D printing”, has experienced exceptional growth thanks to the development of mechatronics and materials science. Fused filament deposition (FDM) manufacturing is the most widely used technique in the field of AM, due to low operating and material costs. However, the materials commonly used for this technology are virgin thermoplastics. It is worth noting a considerable amount of waste exists due to failed print and disposable prototypes. In this regard, using green and sustainable materials is essential to limit the impact on the environment. The recycled, bio-based, and blended recycled materials are therefore a potential approach for 3D printing. In contrast, the lack of understanding of the mechanism of interlayer adhesion and the degradation of materials for FDM printing has posed a major challenge for these green materials. This paper provides an overview of the FDM technique and material requirements for 3D printing filaments. The main objective is to highlight the advantages and disadvantages of using recycled, bio-based, and blended materials based on thermoplastics for 3D printing filaments. In this work, solutions to improve the mechanical properties of 3D printing parts before, during, and after the printing process are pointed out. This paper provides an overview on choosing which materials and solutions depend on the specific application purposes. Moreover, research gaps and opportunities are mentioned in the discussion and conclusions sections of this study.

Equilibrium Energy and Entropy of Vortex Filaments in the Context of Tornadogenesis and Tornadic Flows

In this work, we study approximations of supercritical or suction vortices in tornadic flows and their contribution to tornadogenesis and tornado maintenance using self-avoiding walks on a cubic lattice. We extend the previous work on turbulence by A. Chorin and collaborators to approximate the statistical equilibrium quantities of vortex filaments on a cubic lattice when both an energy and a statistical temperature are involved. Our results confirm that supercritical (smooth, “straight”) vortices have the highest average energy and correspond to negative temperatures in this model. The lowest-energy configurations are folded up and “balled up” to a great extent. The results support A. Chorin’s findings that, in the context of supercritical vortices in a tornadic flow, when such high-energy vortices stretch, they need to fold and transfer energy to the surrounding flow, contributing to tornado maintenance or leading to its genesis. The computations are performed using a Markov Chain Monte Carlo approach with a simple sampling algorithm using local transformations that allow the results to be reliable over a wide range of statistical temperatures, unlike the originally used pivot algorithm that only performs well near infinite temperatures. Efficient ways to compute entropy are discussed and show that a system with supercritical vortices will increase entropy by having these vortices fold and transfer their energy to the surrounding flow.

Optimization of Extrusion Process Parameters of Recycled High-Density Polyethylene-Thermoplastic Starch Composite for Fused Filament Fabrication

High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.

Si3N4工程陶瓷基底金刚石涂层生长规律及性能

为了避免氮化硅材料因产生裂纹或延伸破裂等造成的失效,利用热丝化学气相沉积法(Hot filament chemical vapor deposition,HFCVD)在氮化硅基底上沉积具有高硬度的金刚石涂层,采用单因素影响试验,分别探究碳源浓度、腔室压力、基底温度对金刚石成膜过程的影响机制,探究微米和纳米金刚石涂层的最优生长工艺参数。利用拉曼光谱仪(Raman)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)和原子力显微镜(AFM)对不同参数制备出的金刚石的形核、表面形貌、薄膜质量、表面粗糙度等进行表征,利用洛氏硬度计分析膜基结合力。结果表明,腔室压力越大,活性物质到达基底的动能越小,不利于金刚石的成核和生长。生长速率和表面粗糙度主要受甲烷浓度的影响:甲烷浓度从1%到7%,生长速率从0.84μm/h上升到1.32μm/h;表面粗糙度Ra从53.4 nm降低到23.5 nm;甲烷浓度过高导致涂层脱落严重,膜基结合力变差;晶面形貌和金刚石含量受到基底温度的影响较为明显,随着温度升高,金刚石质量提高。综合基底温度、腔室压力对金刚石涂层的影响,确定最佳生长温度为900℃,气压为1 kPa。调节甲烷浓度1%为微米金刚石;甲烷浓度5%为纳米金刚石。研究方法可以优化在陶瓷基底上制备具有优异性能的金刚石薄膜的制备参数。

利用纤维素工业废丝/胶高效制备再生纤维素纳米晶

为解决再生纤维素工业丝的废丝以及生产过程中的废丝/胶的再利用问题,设计了以再生纤维素工业废丝或废丝/胶为原料高效制备再生纤维素纳米晶(RCNC)的方法,并通过傅里叶变换红外光谱、马尔文激光粒度仪、扫描电子显微镜、X射线衍射和原子力显微镜等方法,对比了利用新溶剂法再生纤维素工业废丝/胶、粘胶再生纤维素工业废丝和浆粕制得的RCNC、CNC的结构性能上的区别。结果表明:新溶剂法再生纤维素工业丝废丝/胶高取向度、高结晶度和结构简单的特性使其可以在更温和的条件下酸解,制备的RCNC得率高达到65.09%,远大于以浆粕为原料制备CNC的得率,且具有更高的结晶度。与粘胶纤维素工业废丝制得的RCNC相比,两者具有相似的尺寸与形貌,都为纳米级的棒状结构,长度和长径比分别为93 nm±26 nm和35±20,表明此方法对于不同来源的纤维素工业丝废丝具有一定的普适性。

血清长链非编码RNA肌动蛋白纤维相关蛋白1-反义RNA1水平与钙化性主动脉瓣狭窄病人左心室功能的相关性研究

目的 分析血清长链非编码RNA(lncRNA)肌动蛋白纤维相关蛋白1-反义RNA1(AFAP1-AS1)表达水平与钙化性主动脉瓣狭窄(CAS)病人左心室收缩及舒张功能的相关性。方法 于2020年1月至2021年12月,选取中国中医科学院广安门医院就诊的CAS病人129例作为CAS组[左心室射血分数(LVEF)≥50%],同期该院健康志愿者130例作为对照组。收集病人人口学资料、超声及实验室生化指标,检测血清lncRNA AFAP1-AS1表达。受试者操作特征曲线(ROC曲线)分析血清lncRNA AFAP1-AS1诊断CAS效能。结果 对照组血清lncRNA AFAP1-AS1表达水平(1.15±0.18)低于CAS组(1.58±0.30)(P<0.001)。轻度狭窄者血清lncRNA AFAP1-AS1表达水平(1.37±0.26)低于中、重度狭窄者,而中度狭窄者lncRNA AFAP1-AS1表达水平(1.59±0.30)低于重度狭窄者(1.79±0.34)(P<0.001)。ROC结果显示,血清lncRNA AFAP1-AS1诊断CAS、重度狭窄的曲线下面积分别为0.86[95%CI:(0.82,0.91)]、0.88[95%CI:(0.82,0.94)]。CAS组AVA水平低于对照组(P<0.001),左室舒张末期内径(LVEDD)、左室舒张末期容积(LVEDV)、室间隔厚度(IVST)、左室后壁厚度(LVPWT)、左房前后径(LAD)、主动脉瓣平均压差(PGmean)、主动脉瓣峰值流速(Vmax)水平高于对照组(均P<0.001)。相关性分析显示,血清lncRNA AFAP1-AS1与LVEDD、Vmax、二尖瓣口舒张早期血流速度峰值(E峰)、二尖瓣口舒张晚期血流速度峰值(A峰)、LVEDV、PGmean、LVESD呈正相关(r=0.60、0.66、0.72、0.68、0.56、0.57、0.50,均P<0.001),与LVEF、AVA呈负相关(r=-0.78、-0.62,均P<0.001)。结论 CAS病人血清lncRNA AFAP1-AS1表达水平升高,与CAS病情严重程度以及左心室舒张、收缩功能有关,并可作为无创血清标志物辅助临床诊断CAS。

养殖池塘丝状藻发生关键因子调查

以水绵和刚毛藻为代表的丝状藻广泛存在于各种自然水体和养殖水体,其过度生长对水体环境和养殖动物构成威胁。为探究丝状藻发生的关键因子,实验通过走访调查,筛选了5组环境相同且隶属同一家养殖户的有丝状藻池塘和无丝状藻池塘,重点对水质、底泥生物可利用性氮磷含量及丝状藻繁殖体进行了检测分析。结果显示,5组有丝状藻塘、无丝状藻塘整体水体氮磷水平无显著差异,而有4组无丝状藻塘叶绿素a含量显著高于有丝状藻塘。5组有丝状藻塘底泥平均生物可利用性氮含量为(15.72±3.60)mg/kg,而无丝状藻塘底泥平均生物可利用性氮为(13.22±1.97)mg/kg,较前者低2.50 mg/kg。5组有丝状藻塘底泥平均生物可利用性磷含量为(72.26±10.57)mg/kg,无丝状藻塘底泥平均生物可利用性磷含量为(50.33±12.62)mg/kg,较前者低21.93 mg/kg。底泥生物可利用性氮磷比在5组中均小于0.5,而无丝状藻塘平均较有丝状藻塘高26.32%。低氮磷比会抑制浮游藻类的繁殖,而丝状藻则对低氮及低氮磷比环境具有较强的适应能力。因此,在养殖开始时,底泥低氮及低氮磷比的条件使得浮游藻类在与丝状藻的初期生态位竞争中处于劣势,即使检测到的浮游藻类OTUs数量高于丝状藻繁殖体,也不能使其在上述条件下成为优势种。另外,对丝状藻繁殖体的检测发现,其广泛存在于有丝状藻塘、无丝状藻塘及水源的水体和底泥中,即使清塘、晒塘依然检测到繁殖体的存在,但清塘、晒塘能够减少丝状藻繁殖体的数量。研究表明,单独依靠生石灰或漂白粉清塘并不能完全杜绝丝状藻的发生,但可以作为一个辅助防控措施,而通过调控养殖系统的生物可利用氮含量及氮磷比左右种间生态位竞争则是一个值得深入研究的、有前景的丝状藻防控方向。本实验结果对养殖池塘的丝状藻防控研究和生产实践具有重要的参考价值。

纬编电热针织物设计和性能评价

为了探究金属长丝作为电加热元件在纬编电热针织物中的应用,通过赛络菲尔纺工艺开发了棉/铜镁合金和棉/不锈钢复合导电纱,并与碳纤维进行比较,采用罗纹空气层加衬纬组织制作了电加热元件并联的3种电热织物,并对导电纱和纬编织物电热性能进行实测及数据拟合。结果显示:复合导电纱达到导电纱A类产品要求;在12 V电压时,棉/铜镁合金导电纱表面温度最高可达40.9℃;金属复合导电纱电热织物升温和时间、电压有关,电热织物的表面平衡温度与输入功率呈线性关系,温度达45℃以上时,电热织物电阻变化率低于2%,热稳定性好;相同条件下,棉/铜镁合金织物升温速度最快,输入功率最大,在4 V电压下最高温度达49.8℃;采用赛络菲尔复合导电纱开发罗纹空气层加衬纬的纬编电加热织物具有一定的可行性。

热丝化学气相沉积法制备单晶金刚石的试验研究

热丝化学气相沉积法沉积区域可达12英寸(30.48 cm),其具备大批量生产单晶金刚石的潜力。采用尺寸为3 mm×3 mm×1 mm,(100)取向的单晶金刚石为基体,利用热丝化学气相沉积法以甲烷和氢气为前驱体,同时通入少量氮气进行同质外延生长。结果表明,在热丝温度为2200℃、碳源浓度为4%、腔体气压为4 kPa的条件下,单晶金刚石以3.41μm/h的速度生长,表面无多晶、破口、孔洞等缺陷;外延层X射线衍射光谱在(400)面处峰值的半高宽为0.11°,低于基体的半高宽0.16°,证明外延层具有较高的晶体质量;氮气的引入可以提升单晶金刚石的生长速度,同时降低外延层的晶体质量,较高的氮气浓度还会使得单晶金刚石的生长模式转为岛状生长。

熔丝制造3D打印CFRP层内损伤破坏机理与模型研究

为将3D打印技术应用到桥梁工程中,以熔丝制造3D打印碳纤维复合材料锚环为研究对象,开展了材料层内损伤失效机理的基础性研究工作.首先,对锚环进行了张拉锚固破坏试验,明晰材料的损伤失效模式.其次,测试分析了材料的弹性参数及强度参数值,供后续仿真分析使用.最后,通过VUMAT子程序构建了材料的损伤失效本构关系,利用ABAQUS仿真分析软件模拟熔丝制造3D打印碳纤维复合材料锚环的渐进损伤失效全过程,分析其层内损伤失效机理.结果表明:熔丝制造3D打印碳纤维复合材料具有显著的层内损伤现象;选用Hashin损伤起始判据与刚度瞬间退化模型作为熔丝制造3D打印碳纤维复合材料损伤力学模型偏于安全,具有一定的可行性;锚环在高度方向产生纵向裂纹是由纤维拉伸失效导致的.

棉和羽毛蛋白丝交织物的性能测试

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