Development of pressure control system in counter gravity casting for large thin-walled A357 aluminum alloy components

Counter gravity casting equipments(CGCE) were widely used to produce large thin-walled A357 aluminum alloy components. To improve the pressure control precision of CGCE to get high quality castings, a pressure control system based on fuzzy-PID hybrid control technology and the digital assembled valve was developed. The actual pressure tracking experiment results show that the special system by applying PID controller and fuzzy controller to varied phases, is not only able to inherit the small error and good static stability of classical PID control, but also has fuzzy control’s advantage of fully adapting itself to the object. The pressure control error is less than 0.3 kPa. By using this pressure control system, large complex thin-walled A357 aluminum alloy castings with high quality was successfully produced.

Topological Optimization Method for Aeronautical Thin-Walled Component Fixture Locating Layout

Fixture locating layout has a direct and influential impact on aeronautical thin-walled component(ATWC)manufacturing quality.The purpose is to develop a topological optimization method for ATWC fixture locating layout to minimize the manufacturing deformation.Firstly,a topological optimization model that takes the stiffness of ATWC as the objective function and the volume of the locating structure as the constraint is established.Secondly,ATWC and the locating structure are regarded as an integrated entity,and the variable-density method based topological optimization approach is adopted for the optimization of the locating structure using ABAQUS topology optimization module(ATOM).Thirdly,through a subsequent model reconstruction referring to the obtained topological structure,the optimal fixture locating layout is achieved.Finally,a case study is conducted to verify the proposed method and the comparison results with firefly algorithm(FA)coupled with finite element analysis(FEA)indicate that the number and positions of the locators for ATWC can be optimized simultaneously and successfully by the proposed topological optimization model.

Vibrations in High Speed Milling of Thin-walled Components

Thin-walled structures have been widely used in the aerospace industry.The dynamic interaction between the milling cutter and thin-walled workpiece can easily lead to vibration.This paper investigates the vibration caused during milling the thin-walled workpiece on the NC machining center,presents a theoretical milling vibration model of thin-walled beam.The model was verified by using milling experiments and numerical simulations.Some valuable conclusions are derived,this will be references to scientific research and guides to the vibration-free milling of thin-walled structures at different cutting speeds.

Preparation and modulation of a novel thin-walled carbon foam

By foaming and carbonization processes under atmospheric pressure, a novel thin-walled carbon foam with developed foam structure was successfully prepared from loose medium component(LMC) separated from raw coal by extraction and back-extraction method. The influences of foaming time, carbonization time, and micromolecule content on foam structure were investigated by scanning electron microscope and mercury injection data. Moreover, foaming mechanism of LMC was analyzed and expounded. The results showed that spherical pores and uniform ultrathin pore walls constitute threedimensional foam structure of carbon foam and foam structure is developed with well connectivity.The effects of foaming time, carbonization time, and micromolecule content on foam structure are significant. Especially, average pore diameters of carbon foams prepared from the extracts of LMC are much smaller. With the rise of extraction rate, average pore diameter decreases and pore size distribution is more concentrated on the aperture section of 0–10 μm.

QTL analysis of the developmental changes in cell wall components and forage digestibility in maize(Zea mays L.)

Cell wall architecture plays a key role in stalk strength and forage digestibility.Lignin,cellulose,and hemicellulose are the three main components of plant cell walls,and they can impact stalk quality by affecting the structure and strength of the cell wall.To explore cell wall development during secondary cell wall lignification in maize stalks,conventional and conditional genetic mapping were used to identify the dynamic quantitative trait loci(QTLs)of the cell wall components and digestibility traits during five growth stages after silking.Acid detergent lignin(ADL),cellulose(CEL),acid detergent fiber(ADF),neutral detergent fiber(NDF),and in vitro dry matter digestibility(IVDMD)were evaluated in a maize recombinant inbred line(RIL)population.ADL,CEL,ADF,and NDF gradually increased from 10 to 40 days after silking(DAS),and then they decreased.IVDMD initially decreased until 40 DAS,and then it increased slightly.Seventytwo QTLs were identified for the five traits,and each accounted for 3.48–24.04%of the phenotypic variation.Six QTL hotspots were found,and they were localized in the 1.08,2.04,2.07,7.03,8.05,and 9.03 bins of the maize genome.Within the interval of the pleiotropic QTL identified in bin 1.08 of the maize genome,six genes associated with cell wall component biosynthesis were identified as potential candidate genes for stalk strength as well as cell wall-related traits.In addition,26 conditional QTLs were detected in the five stages for all of the investigated traits.Twenty-two of the 26 conditional QTLs were found at 30 DAS conditioned using the values of 20 DAS,and at 50 DAS conditioned using the values of 40 DAS.These results indicated that cell wall-related traits are regulated by many genes,which are specifically expressed at different stages after silking.Simultaneous improvements in both forage digestibility and lodging resistance could be achieved by pyramiding multiple beneficial QTL alleles identified in this study.

Performance index limits of high reinforced concrete shear wall components

The deformation performance index limits of high reinforced concrete （RC） shear wall components based on Chinese codes were discussed by the nonlinear finite element method. Two typical RC shear wall specimens in the previous work were first used to verify the correctness of the nonlinear finite element method. Then, the nonlinear finite element method was applied to study the deformability of a set of high RC shear wall components designed according to current Chinese codes and with shear span ratio λ≥2.0. Parametric studies were made on the influence of shear span ratio, axial compression ratio, ratio of flexural capacity to shear capacity and main flexural reinforcement ratio of confined botmdary members. Finally, the deformation performance index and its limits of high RC shear wall components under severe earthquakes were proposed by the finite element model results, which offers a reference in determining the performance status of RC shear wall components designed based on Chinese codes.

The Effect of Clove Essential Oil Treatment on the Cell Wall Components of Wheat Straw

The aim of this study was to determine the effects of additions of different doses of clove oil （Syzygium aromaticum L.） on cell wall component of wheat straw. For this purpose, wheat straw was treated with 100 ppm and 200 ppm clove oil and applied at two different time period （1 h and 5 h）. The microscopic analysis was made on cell wall components of untreated and treated of the straw. According to the research findings, with increasing doses and time of clove oil treatment, particularly, neutral detergent fiber （NDF） and acid detergent fiber （ADF） content of straw significantly （P 〈 0.05） reduced, approximately at the level of 15% for NDF and 13% for ADF, respectively. The lowest NDF, ADF, acid detergent lignin （ADL） and cellulose contents were found in 200 ppm dose and 5 h period. However, the lowest stem section thickness likewise was determined in 5 h period （P 〈 0.05）, but there was no significant difference between the dose. Consequently, it could be said that the addition of clove oil have a positive influence on cell wall components and stem section thickness of wheat straw.

Domain walls and their interactions in a two-component Bose–Einstein condensate

We investigate domain wall excitations in a two-component Bose–Einstein condensate with two-body interactions and pair-transition effects. It is shown that domain wall excitations can be described exactly by kink and anti-kink excitations in each component. The domain wall solutions are given analytically, which exist with different conditions compared with the domain wall reported before. Bubble-droplet structure can be also obtained from the fundamental domain wall, and their interactions are investigated analytically. Especially, domain wall interactions demonstrate some striking particle transition dynamics. These striking transition effects make the domain wall admit quite different collision behavior, in contrast to the collision between solitons or other nonlinear waves. The collisions between kinks induce some phase shift, which makes the domain wall change greatly. Their collisions can be elastic or inelastic with proper combination of fundamental domain walls. These characters can be used to manipulate one domain wall by interacting with other ones.

钛合金薄壁构件快速加热冷模热冲压成形技术进展

为了解决钛合金薄壁构件热成形效率低、成本高、组织性能控制难度大等问题,近年来钛合金冷模热冲压成形技术受到关注。在该新技术中利用室温模具对加热后的钛合金板材进行快速冲压成形和模内快速冷却,由于取消了模具加热,可以变革性地提高钛合金薄壁构件成形效率、降低成本。然而,与传统等温成形不同,在冷模热冲压成形过程中,钛合金板材温度不断下降,这对钛合金成形极限、回弹及组织性能等的控制提出了全新的挑战。分析了钛合金薄壁构件冷模热冲压成形技术特点及存在的问题,归纳了快速加热对钛合金组织性能的影响规律,综述了钛合金薄壁构件快速加热冷模热冲压成形工艺进展,最后对该技术未来的发展方向进行了展望。

基于拉曼技术的高地钩叶藤导管壁化学成分微区分布研究

为探寻棕榈藤材具有优良韧性的机理和棕榈藤材高值化利用,选择高地钩叶藤为研究对象,利用显微共聚焦拉曼技术,对导管壁化学成分的微区分布进行测试分析。结果表明,高地钩叶藤导管壁纤维素分子浓度为次生壁>复合胞间层>细胞角隅,而木质素分子浓度分布恰好相反。次生壁内、外层纤维素、木质素及半纤维素分子浓度差异较小。在藤茎径向上,藤芯处导管次生壁中层和细胞角隅处木质素的分子浓度最高,藤皮处导管的半纤维素分子浓度最高。藤皮处导管次生壁中层纤维素的分子浓度最低而细胞角隅处却最高,而藤中与藤芯处导管细胞角隅中半纤维的分子浓度均很小。在藤茎轴向上,随着高度增加藤皮导管次生壁中层木质素和半纤维素分子浓度变化趋势相同,而纤维素分子浓度在藤皮与藤芯间变化趋势完全相反。除导管各壁层的三大素分布呈一定规律性外,在藤茎径向和轴向上规律不明显。

Ni/Al叠层薄壁筒形构件热态气压成形工艺

NiAl基合金性能优异,具有成为下一代高温结构材料的潜力。然而,难变形NiAl基合金薄壁筒形构件的成形是阻碍其应用的主要难题。本文基于叠层材料的成形-反应制备工艺,以Ni、Al箔材为原料,首先制备了Ni/Al叠层圆柱筒坯,而后完成了Ni/Al叠层圆柱筒坯两端扩口密封,获得了质量良好、微观组织优异的扩口叠层圆柱筒坯。最终采用热态气压成形方法,制备了Ni/Al叠层圆-方变截面薄壁构件,为Ni/Al叠层薄壁复杂异形构件的成形提供了参考。

苦瓜果实不同发育时期细胞壁组分及相关酶活性的差异分析

为了解苦瓜(Momordica charantia)果实品质差异的原因,以厚肉型种质‘LX1-3’和薄肉型种质‘ZK54’为材料,对果实发育过程中细胞壁组分含量及相关酶活性进行了分析。结果表明,花后17d,‘LX1-3’果实的横径(FD)、腔径(FLD)、果肉厚度(PT)、单瓜鲜质量(FFW)和干质量(FDW)均超过‘ZK54’。细胞壁组分和酶活性表现品种间差异,水溶性果胶含量整体水平表现为厚肉型高于薄肉型,且与PT、FFW和FDW呈显著正相关;花后17~23 d‘LX1-3’的半纤维素(HCE)和纤维素(CE)含量均高于‘ZK54’;花后3 d,两种质的β-半乳糖苷酶(β-Gal)和β-木糖苷酶(β-Xyl)活性显著高于其他3个时期,多聚半乳糖醛酸酶(PG)、β-Gal和果胶酶变化趋势与离子型果胶和共价型果胶含量的变化一致。β-Gal、β-Xyl和纤维素酶活性与5个生长性状间呈极显著/显著负相关,PG与FD、FLD和PT呈极显著/显著负相关。因此,细胞壁组分和酶活性与果实发育密切相关,β-Xyl和β-Gal在苦瓜早期发育中发挥主要效应,而HCE和CE对果实中后期发育影响较大。

灰枣和冬枣果实质地差异的解剖学观察及相关酶活性研究

【目的】以果实质地差异明显的两个枣品种为试验材料,观察其发育过程中果肉细胞的显微结构,测定果实的含水量、硬度及细胞壁相关代谢酶的活性,并进行相关性分析,探究影响两种质地形成的关键因素。【方法】分别以灰枣(制干枣)和冬枣(鲜食枣)花后31(S1)、63(S2)、78(S3)、98(S4)和108 d(S5)的果实为试验材料,对果实发育过程中含水率、硬度,果肉细胞形态、细胞壁组分及代谢酶活性进行动态分析。【结果】(1)随着果实发育,灰枣和冬枣的含水率均呈先升高后下降的趋势,硬度均呈下降趋势,且灰枣硬度持续高于冬枣。(2)两个品种果肉细胞的变化均呈现先迅速增大后缓慢增大的趋势,但冬枣果肉薄壁细胞面积大于灰枣。(3)果肉细胞超显微结构观测显示,在S5时期,两个品种果肉细胞壁、中胶层已经明显降解,但冬枣相较灰枣其中胶层、内含物降解较慢。(4)两个品种总果胶以及纤维素含量整体呈逐渐降低趋势,且冬枣一直低于灰枣。(5)果实硬度与总果胶和纤维素含量呈显著正相关,与β-半乳糖苷酶(β-Gal)、α-L-阿拉伯呋喃糖苷酶(α-Af)、果胶裂解酶(PL)活性呈极显著负相关,多聚半乳糖醛酸酶(PG)活性与冬枣果实硬度、水分含量的相关性均极显著,但与灰枣相关性不显著。【结论】灰枣和冬枣质地品质的差异与细胞壁组分总果胶及纤维素含量、果肉细胞显微结构的差异相关,还与细胞壁代谢相关酶β-Gal、α-Af、PL有关,此外,PG在冬枣质地变化中也发挥关键作用。

红卡壁骨架化学成分分析与结构表征

通过发酵酶解制备了红卡壁骨架(N-CWS),采用化学鉴别、比色法、高效液相色谱法(HPLC)对其化学成分进行了分析,并通过扫描电镜(SEM)、透射电镜(TEM)、傅立叶变换红外光谱(FTIR)、差示扫描量热法(DSC)、热重-差热分析(TG-DTA)等对其微观结构和热分解性能进行了表征。结果表明,N-CWS主要含有多糖、类脂化合物、氨基酸等成分,其中多糖主要由阿拉伯糖、半乳糖、甘露糖、葡萄糖醛酸等单糖组成;N-CWS粉末易聚集、黏连,单个骨架尺寸为500 nm×300 nm;N-CWS为无定形粉末,其TG曲线只有1个失重台阶,热分解温度在285℃附近,具有较好的热稳定性。

硅对锰-铅复合胁迫下水稻幼苗叶片细胞壁多糖组分中锰和铅含量的影响

【目的】探究不同浓度SiO_(2)对锰-铅(Mn-Pb)复合胁迫下水稻幼苗叶片细胞壁多糖组分中Mn和Pb含量的影响,为利用农艺措施治理矿区农田重金属复合污染提供理论依据。【方法】在模拟矿区重金属污染前提下,先用水培法将水稻种子培养至5叶1心期,然后用2 mmol/L Mn^(2+)+2 mmol/L Pb2+溶液复合胁迫水稻幼苗。设6个不同的SiO_(2)处理浓度:0(对照,CK)、70、90、110、130和150 mg/L。处理后提取水稻幼苗叶片细胞壁多糖组分,测定和分析其中Mn和Pb含量。【结果】施加SiO_(2)增加细胞壁多糖组分(果胶质、半纤维素和纤维素)中Mn和Pb含量。与CK相比,当SiO_(2)浓度为70~110 mg/L时,细胞壁果胶质中Mn和Pb含量较高;SiO_(2)处理下果胶质中Pb含量大于Mn含量,当SiO_(2)浓度小于90 mg/L时,水稻幼苗叶片细胞壁中Pb含量小于Mn含量。SiO_(2)浓度为110 mg/L时,在半纤维素和纤维素中Mn和Pb含量均较高;水稻幼苗叶片细胞壁半纤维素中Pb含量大于Mn含量,SiO_(2)浓度小于90 mg/L时,纤维素中Pb含量为负值。未施加SiO_(2)时,Mn和Pb的主要结合位点分别为纤维素和果胶质,施加SiO_(2)使Pb的主要结合位点转移为半纤维素。【结论】SiO_(2)能增加重金属Mn和Pb在细胞壁多糖组分中的含量。Mn-Pb复合胁迫下,SiO_(2)浓度为110 mg/L时,Mn和Pb的含量在细胞壁、果胶质、半纤维素和纤维素中均较多。

Ni 3Al/NiAl/Ni复合板组织性能及其薄壁构件反应成形一体化工艺研究

针对Ni-Al金属间化合物材料成形困难问题,对Ni 3Al/NiAl/Ni复合板进行了组织性能与反应成形一体化工艺的研究。以Ni/Al箔材为试验材料,对1200℃,热压时长0.5、1、2和4 h条件下热压复合法得到的Ni 3Al/NiAl/Ni板进行微观组织表征与室温及高温(1000℃)条件下的单向拉伸试验。根据试验结果确定了在1200℃、1 h条件下热压反应的复合板具有较佳综合力学性能,室温条件下抗拉强度与伸长率分别为527.6 MPa和4.4%,1000℃高温条件下抗拉强度与伸长率分别为165.7 MPa、21.2%。进一步在该参数下进行反应成形一体化工艺的研究,制备得到了具有良好表面质量与尺寸精度的薄壁锥筒壳件。在薄壁锥筒壳件上取样进行微观组织与力学性能表征,发现其组织和力学性能与相同工艺条件下制备的复合板相近。

一种融合KPCA、FastICA及SVD的腹壁源胎儿心电 信号提取算法研究

目的:为实现从母体腹壁混合信号中提取高信噪比和波形清晰的胎儿心电信号,提出一种融合核主成分分析(kernel principal component analysis,KPCA)、快速独立成分分析(fast independent component analysis,FastICA)及奇异值分解(singular value decomposition,SVD)的胎儿心电信号提取算法。方法:首先,采用KPCA对母体心电信号进行降维,再利用改进的基于负熵的FastICA处理降维后的数据,得到独立成分。随后,引入样本熵进行信号通道选择,挑选出包含最多母体信息的信号通道。在选中的母体通道上进行SVD,得到母体心电信号的近似估计,再用腹壁源信号减去该信号得到胎儿心电的初步估计。最后,采用改进的基于负熵的FastICA成功分离出纯净的胎儿心电信号。在腹部和直接胎儿心电图数据库(Abdominal and Direct Fetal Electrocardiogram Database,ADFECGDB)和PhysioNet 2013挑战赛数据库中对提出的算法进行验证。结果:提出的算法在主观视觉效果和客观评价指标上都表现出优越的性能。在ADFECGDB数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.74%、98.85%和99.30%;在PhysioNet 2013挑战赛数据库中,胎儿QRS复合波检测的敏感度、阳性预测值和F1值分别为99.10%、97.87%和98.48%。结论:融合KPCA、FastICA及SVD的胎儿心电信号提取算法在提取胎儿心电信号的同时有效处理了附加噪声,为胎儿疾病的早期诊断提供了有力支持。

从BIPV(光伏建筑一体化)到BIPVES(光伏储能建筑一体化)

[目的]随着光伏、储能、新型建材及装配式建筑产业的发展,将光伏组件与屋面、墙体、遮阳等构件进行一体化设计与制造的光伏建筑一体化(Building Integrated Photovoltaic,BIPV)技术开始延伸为光伏储能建筑一体化(Building Integrated Photovoltaic and Energy Storge,BIPVES)技术。[方法]文章提出世界首个可充电水泥电池,将建筑墙体与光伏发电装置、储放电装置相融合;对设备和材料进行跨界创新,在玻璃表面打印高清晰度、高透光率花纹图案,制造高效光伏建材;研发预制式储能墙体,与各类钢结构装配式建筑体系进行结合,实现订制式生产、装配式施工,形成建筑构件与光伏、储能一体化的变革趋势。[结果]水泥基电池实现了建筑墙体具有光伏发电、储电以及供电等多种功能;新一代光伏建材可节省建筑外立面装饰材料的成本,降低建筑物碳排放;光伏和储能等可再生能源技术在建筑中的一体化集成,可取得最大化收益。[结论]新型光伏建材技术和水泥电池等新型储能技术具有发展前景,将可充电电池构件、光伏外墙板与装配式建筑墙体及预埋件进行组合集成并推广应用具有可行性。

不同铝浓度处理下马尾松体内铝的分配特征

有毒金属离子在植物组织中的分布和亚细胞水平的定位与植物对金属离子的耐受性密切相关。为探究铝进入马尾松体内后在亚细胞水平下的分布情况,该研究分别设置0、0.5、1.0、2.0 mmol·L^(-1)4个铝浓度,通过盆栽试验研究不同铝浓度下马尾松的生长状况及亚细胞水平下铝的分配特征。结果表明:(1)低浓度铝(0.5 mmol·L^(-1))显著促进马尾松的生长(P<0.05),随铝浓度的升高(≥1.0 mmol·L^(-1)),马尾松根系生长和根尖细胞活力均受到抑制。(2)相较于茎叶,进入马尾松体内的铝主要沉积在根系中(P<0.05),但随着铝浓度的增加,茎叶中的铝含量也开始增加。(3)亚细胞水平下,不同铝浓度影响了铝在细胞壁和液泡中的分配比例。当铝浓度为1.0 mmol·L^(-1)及以下时,铝在根系和茎叶的细胞壁和液泡中的比例均较高,两者间铝含量差异不显著;而高铝浓度下(2.0 mmol·L^(-1)),铝则主要沉积在细胞壁上,根系、茎叶的细胞壁铝含量分别占比55%和70%。相较而言,各铝浓度处理下细胞器和细胞质中的铝含量均维持在较低水平,这降低了铝对细胞功能的影响。综上认为,马尾松可以通过调整体内铝的分配来适应铝胁迫,这为后续从细胞及分子层面进一步阐明马尾松对铝环境的适应机制奠定了理论基础。

700℃实炉验证试验平台过热试件热流密度测量及壁温分布研究

随着锅炉主蒸汽参数的提高,炉内受热面壁温的监测对于安全运行日益重要,并且有利于根据壁温分布进行选材,降低造价。南京电厂700℃验证试验平台炉内过热试件分布着12个牌号的材料,掌握锅炉管壁温分布及其随负荷变化的规律,是准确分析材料验证情况的基础。采用火焰强度热流计对炉内热流密度的空间分布进行实际测量,结合受热面进出口蒸汽参数的实际测量结果,对炉内壁温分布进行计算,结果表明:过热试件不同方向的热流密度在15~180kW/m^(2)范围内,并呈现明显的规律性,其中收到来自前方的热流密度最大、下方的热流密度其次,并且屏底热流密度最高、炉顶位置热流密度最低,屏底水平管平均热流密度约为垂直管的1.3倍。根据热流密度空间分布测量结果计算的过热试件壁温沿着蒸汽流程方向快速增加,在屏底位置出现一个小的峰值,然后增速放缓、最后在靠近管屏出口处略有下降;而管壁和蒸汽温差呈现先增加后减少、并在屏底出现明显峰值的现象,最外侧管屏底最大温差达到约88℃,屏顶温差则降低到约25℃。锅炉负荷越高,热流密度越大,同时壁温沿程增长速率越高。炉内壁温测量元件与壁温计算结果的最大温度偏差小于2%,两者具有良好的一致性。根据壁温计算结果对过热试件进行选材,约有51.2%的锅炉管须采用镍基合金材料,相比全部采用镍基合金材料可大幅降低成本。