基于正交试验法的3P3R磨削机器人灵活性优化

针对机器人磨削加工复杂曲面工件时,存在加工路径不连续、需要更换夹具而影响加工精度的问题,提出了一种3P3R磨削机器人.使用D-H法建立了机器人的运动学模型,得到了机器人的正解方程.建立了工件坐标系{W}主动、工具坐标系{T}被动模式的新型机器人系统坐标系,指出了机器人基坐标系{O}与{T}的相对位置是影响磨削机器人的灵活空间的重要因素.采用正交试验法,得到了机器人的第二关节方向的相对位置是影响灵活磨削空间最显著的因素,并且优化了磨削机接触轮相对于机器人摆放的位置,使机器人的灵活磨削空间扩大了1倍,提高了磨削机器人的灵活性.     

钛合金TB6侧铣表面完整性实验

使用表面完整性基本评价方法对TB6钛合金侧铣后试件的表面完整性（表面形貌、表面粗糙度、加工硬化）进行研究.结果表明,对表面形貌影响最明显的因素是每齿进给量f_z,过大的f_z会使已加工表面出现鳞刺现象.f_z是影响已加工表面进给方向粗糙度的最主要因素,随着f_z从0.06 mm/z增大到0.12 mm/z,表面粗糙度R_a会由0.283 μm显著增加到0.964 μm.线速度v_c,f_z和径向切深a_e的变化对刀轴方向粗糙度影响很小.而刀具的后刀面磨损是影响已加工表面刀轴方向粗糙度的主要因素,极轻微的后刀面磨损都会导致刀轴方向粗糙度明显增加,随着后刀面磨损量V_B由0增加到0.025 mm,刀轴方向粗糙度由0.22 μm剧烈增加到0.686 μm.侧铣过程中TB6的加工硬化现象不严重,表层组织没有明显变质层产生,晶粒也没有出现明显的拉伸、扭曲或破裂.      

后向台阶层流分离剪切层特性研究

应用激光测速仪对生向台阶层流边界层分离产生的剪切层在再附前的发展进行了测量，得到了时均速度、湍流强度及剪切层厚度等的分布特性，并研究了来流湍流度对台阶后流场湍强度分布及剪切层发展的影响，实验中发现台阶后有一个流速降低的区域，对此从涡动力学的角度作了解释。     

BBO单晶生长过程中气相包裹体形成的实时观察研究

BBO单晶生长过程中包裹体的出现是影响晶体质量及制约晶体尺寸的一个重要因素.利用高温休伦微分干涉显微技术,实时观察了BBO助溶剂法生长过程中出现的气相包裹体的形成过程.结果表明,包裹体产生于完美晶体内部,并趋向于分布在界面附近,单晶生长过程中台阶的发展将有助于制约气相包裹体的形成和分布.      

旋转对气膜冷却覆盖区域的影响

气膜冷却是应用于航空发动机上的冷却技术,旋转是影响气膜与主流掺混区域的重要因素.在旋转气膜外换热实验台上进行的平板气膜冷却实验对此问题进行了研究.与静止叶片相比,气膜出流在旋转叶片表面会发生展向偏离.在压力面,转速增加,气膜出流先向低旋转半径方向偏转,后向高旋转半径方向偏转;在吸力面,气膜出流向高旋转半径方向偏转.动量流量比固定,当密度比增加时,压力面气膜出流轨迹向低旋转半径方向偏转加剧;吸力面气膜出流轨迹向高旋转半径方向的偏转也增大.      

旋转状态下曲率对气膜与主流掺混区域的影响

气膜冷却是应用于航空燃气轮机上的冷却技术,旋转及表面曲率是影响气膜与 主流掺混区域的重要因素,通过数值计算方法对旋转状态下曲率对气膜与主流掺混区域的影 响进行了研究,湍流模型选取了k-ω模型.增加旋转速度,会引起吸力面气膜的分离; 固定转速,降低表面曲率半径,压力面气膜发生分离,吸力面气膜冷却效果得到改善.当动 量流量比在小于1的范围内变化时,旋转只改变压力面气膜与主流掺混区域的分布,而对吸 力面没有影响.      

金刚石滚轮修整效果与修整机理

磨削钛合金时砂轮粘附严重,砂轮修整对磨削效果的影响尤为显著.采用金刚石滚轮修整新型陶瓷氧化铝SG砂轮并进行钛合金的磨削实验,通过改变修整参数(包括轴向速度、修整深度和修整速比)对磨削力、工件表面粗糙度及表面形貌进行测量,考察不同修整参数对磨削效果的影响.研究结果表明,减小轴向速度和修整深度均使磨削力增加,同时获得较好的工件表面质量.修整速比对工件表面粗糙度的影响比较复杂.研究发现,修整速比为0.4时修整出来的砂轮磨削后工件表面质量较好.在分析实验结果的基础上,深入探讨了砂轮修整机理和工件表面形貌形成机理.实验及分析结果为金刚石滚轮修整SG砂轮磨削钛合金的修整工艺提供了依据.      

CsI(Eu)晶体空间生长地面实验

人工晶体在高技术领域具有十分重要的应用.在多组分晶体生长过程中,由于分凝的存在,会导致成分沿晶体生长方向产生变化,从而影响到晶体性能的均匀性,对应用产生不利影响.为研究微重力对多组分晶体分凝的影响,利用天宫二号卫星进行空间晶体生长实验.结合晶体生长特性和天宫二号综合材料实验装置的技术条件,确定以铕掺杂CsI晶体为研究对象.在地面研制阶段,CsI（Eu）晶体样品顺利通过力学环模试验,并在地面实验中生长出质量较高的CsI晶体,样品中存在明显的组分分凝.      

歼击机座舱空气流动和传热模拟实验

对某型歼击机座舱的空气流动和传热进行了全尺寸地面模拟实验.模拟了气动热载荷和人体热载荷,并使用ATM2400型36通道多点气流和温度测量系统测量了5个测试面的速度场以及其中两个测试面和邻近服装表面的温度场.观察了供气流量和集中喷嘴开关对舱内空气流动状态和温度分布的影响,评价了该座舱的舒适性.结果表明:舱内速度场 并非相对座舱纵向中心面对称分布,而座舱内壁面温度分布亦极不均匀;集中喷嘴全开和全关时,舱内气流速度场和温度场及邻近服装表面空气温度的分布情况差别显著,但对舱内气流平均速度和平均温度的影响不大;舱内气流平均速度随供气量呈线性变化.实验结果可为数值模拟提供验证依据.     

旋转状态下温度比对气膜与主流掺混区域的影响

为了研究在旋转状态下温度比对气膜与主流掺混区域的影响,采用了数值模拟的方法对此进行了分析.结果表明:与静止状态相比,气膜出流在旋转状态下会发生偏转.当温度比固定,随着转速的增加,吸力面上气膜覆盖区域向高旋转半径方向偏转;但在压力面上,覆盖区域向低旋转半径方向偏转.在旋转速度固定时,随着冷却气膜和燃气温度比的增加,气膜覆盖区域向高旋转半径方向偏转.旋转同时会降低气膜冷却效率,而温度比对此的影响却很小.      

车辆与二轮车预碰撞场景分析及其AEB优化

车辆自动紧急制动（AEB）系统的应用存在大量误识别和不合理决策的挑战，在典型场景下开展测试，可以有效提高AEB的适用性。对国内外相关研究进行分析，从12类车辆与二轮车预碰撞场景中提取AEB测试重点关注的2类涉及参与方转向的场景（场景S11和S12），建立2类典型场景下的Pre-scan模型和量化描述二轮车相对于车辆运动轨迹的数学模型，并对AEB的效用及改进方向进行定性和定量分析。结果表明：场景S11和S12中，二轮车在运动坐标系下的运动轨迹仅与车辆和二轮车速度比值相关；场景S11中，仅当车辆和二轮车速度比值取为(0.788 8,+∞)时，二轮车能够进入车辆AEB触发域，将AEB视场角从60°增大到90°，可有效改善AEB触发效果，速度比值范围从(0.788 8,+∞)增加至(0.203 3,+∞)；场景S12中，当二轮车和车辆速度比值取为(0,(?v+2.46)/9.64)时，车辆AEB具有较好的触发效果，将AEB触发宽度从1.5 m扩大至2 m时，对AEB触发效果的改善幅度不大。研究成果可为AEB系统的改进优化提供技术支撑。     

接触角法测玄武岩及玻璃纤维表面能实验

通过Wilhelmy吊片法测试液体与玄武岩、玻璃纤维单丝的前进接触角,应用OWRK理论计算得到纤维表面能及其色散与极性分量.实验研究表明:未经表面处理的玄武岩纤维表面能高于S-2玻璃纤维,去除浸润剂后2种纤维表面能的极性分量均明显降低,并且测试液体的极性分量对纤维表面能的测试结果影响甚大.分析结果为纤维与树脂的表面张力合理匹配、形成良好界面浸润和粘接提供了理论依据.      

Perpendicular transport of charged particles: Results for the unified nonlinear transport theory derived from the Newton–Lorentz equation

The perpendicular diffusion coefficient is calculated by combining a recently developed Unified Nonlinear Transport (UNLT) theory with the Newton–Lorentz equation. The total perpendicular mean free path can be described as a combination of a guiding center contribution and a microscopic contribution. It is shown that the total mean free path depends strongly on the energy range of the turbulence power spectrum and on particle energy. Further, a slab/2D composite model is used to investigate the influence of each contribution to the total mean free path for a quasi-3D turbulence model. For pure 2D turbulence the UNLT reduces to the NLGC-theory. For pure slab turbulence the guiding center contribution is subdiffusive in accordance with simulations and the theorem on reduced dimensionality. Conversely, the microscopic contribution is non-zero, which has to be interpreted as normal diffusion.     

Developing a vitamin greenhouse for the life support system of the International Space Station and for future interplanetary missions.

In order to evaluate the effects of gravity on growing plants, we conducted ground based long-term experiments with dwarf wheat, cultivar Apogee and Chinese cabbage, cultivar Khibinskaya. The test crops had been grown in overhead position with HPS lamp below root module so gravity and light intensity gradients had been in opposite direction. Plants of the control crop grew in normal position under the same lamp. Both crops were grown on porous metallic membranes with stable -1 kPa matric potential on their surface. Results from these and other studies allowed us to examine the differences in growth and development of the plants as well as the root systems in relation to the value of the gravity force influence. Dry weight of the roots from test group was decreased in 2.5 times for wheat and in 6 times - at the Chinese cabbage, but shoot dry biomass was practically same for both test and control versions. A harvest index of the test plants increased substantially. The data shows, that development of the plants was essentially changed in microgravity. The experiments in the space greenhouse Svet aboard the Mir space station proved that it is possible to compensate the effects of weightlessness on higher plants by manipulating gradients of environmental parameters (i.e. photon flux, matric potential in the root zone, etc.). However, the average productivity of Svet concerning salad crops even in ground studies did not provide more than 14 g fresh biomass per day. This does not provide a sufficient level of supplemental nutrients to the crew of the ISS. A cylindrical design of a space plant growth chamber (SPGC) allows for maximal productivity in presence of very tight energy and volume limitations onboard the ISS and provides a number of operational advantages. Productivity from this type of SPGF with a 0.5 kW energy utilization when salad growing would provide approximately 100 g of edible biomass per day, which would almost satisfy requirements for a crew of two in vitamin C and carotene and partly vitamin B group as well as rough fiber.     

微重力下胶原蛋白纤维化及羟基磷灰石结晶的初步研究

在长期空间飞行过程中, 骨质丢失是一个严重问题. 羟基磷灰石(HAP)晶体是骨骼的主要成分, 骨骼中的胶原蛋白纤维在HAP生长结晶过程中起到关键作用. 研究了胶原蛋白纤维化过程在模拟微重力和常重力条件下的变化, 对以胶原 蛋白纤维作为模板生长出的HAP晶体形貌进行了观察. 结果表明, 不同浓度胶原蛋白溶液中形成的胶原蛋白纤维, 其内部孔隙数量和尺寸在模拟微重力条件下要明显大于常重力条件下, 胶原蛋白纤维内部孔隙的分布也不同于常重力条 件下的结果. 以模拟微重力条件下形成的胶原蛋白纤维为模板生长出的HAP 晶体主要为立方体状, 而以常重力条件下形成的胶原蛋白纤维为模板生长出的 HAP晶体形貌主要为板状. 该结果有助于未来进一步阐明空间骨质丢失的机理.      

三维回转器回旋条件下拟南芥种子发育分析

向重力性反应是植物适应地球重力环境的一个重要生理过程, 是植物正常生长发育不可缺少的反应机制, 但是, 微重力是否影响植物种子发育至今尚无一致性结论. 本文研究了三维回转器回旋模拟微重力对拟南芥种子发育(胚胎发育与代谢活动)的影响. 研究结果表明, 三维回转条件下, 拟南芥果荚出现不规则弯曲或扭曲形态, 形成的种子中可溶性糖和淀粉含量明显增加, 盐溶性贮藏蛋白质含量显著降低而碱溶性蛋白质含量显著升高, 球形胚时期的种子对三维回转处理最为敏感. 对球形胚时期的植株进行短期的三维回转处理可抑制胚柄细胞的分裂和伸长, 而胚柄伸长受阻可能会影响到营养物质向胚胎中输送, 进而导致部分胚胎败育. 对种子干燥脱水阶段的植株进行三维回转处理不影响胚胎的发育, 但会导致种子贮藏蛋白质含量下降.      

Influence of altered gravity on the cytochemical localization of cytochrome oxidase activity in central and peripheral gravisensory systems in developing cichlid fish.

Cichlid fish larvae were reared from hatching to active free swimming under different gravity conditions: natural environment, increased acceleration in a centrifuge, simulated weightlessness in a clinostat and near weightlessness during space flight. Cytochrome oxidase activity was analyzed semiquantitatively on the ultrastructural level as a marker of regional neuronal activity in a primary, vestibular brainstem nucleus and in gravity receptive epithelia in the inner ear. Our results show, that gravity seems to be positively correlated with cytochrome oxidase activity in the magnocellular nucleus of developing fish brain. In the inner ear the energy metabolism is decreased under microgravity concerning utricle but not saccule. Hypergravity has no effect on cytochrome oxidase activity in sensory inner ear epithelia.     

The state of gravity sensors and peculiarities of plant growth during different gravitational loads.

In the primary roots of lettuce shoots grown under altered gravitational conditions--180 degrees inversion on the centrifuged clinostat, horizontal clinostat and in dynamic weightlessness--localization of the cellular organelles, cell morphology and peculiarities of growth have been studied. Significant changes took place in the localization of amyloplasts on the horizontal clinostat. The changes of amyloplast position in the cap cells on the horizontal clinostat and under weightlessness are similar. A change of the normal shoot position (180 degrees inversion and horizontal clinostat) causes an inhibition of growth. Weightlessness increases the length of axial organs and cells in the zone of elongation, but decreases the nitotic index in comparison to the centrifuged control. The anlysis of the formation of generative organs has been carried out for Arabidopsis plants grown on board the orbital station Salyut-6. The ability of plants to undergo vegetative growth and to pass through early phases of generative development under weightlessness was confirmed.     

The effects of simulated microgravity on cultured chicken embryonic chondrocytes.

Using the cultured chicken embryonic chondrocytes as a model, the effects of simulated microgravity on the microtubular system of the cellular skeleton, extracellular matrix, alkaline phosphatase activity, intracellular free calcium concentration and mitochondrial ATP synthase activity with its oligomycin inhibition rate were studied with a clinostat. The microtubular content was measured by a flow cytometer. The decrease of microtubular content showed the impairment of the cellular skeleton system. Observation on the extracellular matrix by the scanning electron microscopy showed that it decreased significantly after rotating, and the fibers in the extracellular matrix were more tiny and disorderly than that of the control group. It can be concluded that the simulated microgravity can affect the secreting and assembly of the extracellular matrix. In contrast to the control, there was a time course decrease in alkaline phosphatase activity of chondrocytes, a marker of matrix mineralization. Meanwhile a significant drop in the intracellular calcium concentration happened at the beginning of rotation. These results indicate that simulated microgravity can suppress matrix calcification of cultured chondrocytes, and intracellular free calcium may be involved in the regulation of matrix calcification as the second signal transmitter. No significant changes happened in the mitochondrial ATP synthase activity and its oligomycin inhibition rate. Perhaps the energy metabolism wasn't affected by the simulated microgravity. The possible mechanisms about them were discussed.