摘要:船用低速柴油机的吊具受力复杂且不规则,传统设计通过简化模型计算其理论强度,与实际工况误差较大。文中利用有限元软件ANSYS分析,以6S42MC整机吊具为研究对象,采用三维软件PROE建立该吊具模型并对其进行有限元分析,根据分析所得的应力分布和形变情况,判断吊具的可靠性;通过改变吊具的结构尺寸,对减少吊具应力的方法进行探究;对吊具进行拓扑优化。分析结果表明,文中方法可以检验吊具的安全性,提高经济效益,同时为吊具的理论设计提供了依据。%The forces acted on the low-speed marine diesel engines′spreader are complex and irregular .The tra-ditional design calculates the theoretical strength by simplifying the model ,but it has great errors under the actual working conditions .In this paper ,by using finite element software ANSYS analysis ,we make up for the defects of the traditional design .Model and finite element analysis are mode by the three-dimensional software PROE .Ac-cording to analysis from the stress distribution and deformation ,the reliability of the spreader is judged;the reduc-tion of the stress of the spreader is explored by changing the structure size of the spreader ;the topology optimiza-tion is made .The analysis results proved that we can test the safety of the spreader ,improve the econanic benefit , and provide the basis for the theory of the spreader design .
摘要:为了深入研究家蚕滞育的分子机理,从家蚕基因组中扩增了1395 bp和972 bp 2个不同长度的滞育激素受体基因Bmdhr启动子片段,以pGL3.0 Basic为载体,分别构建荧光素酶报告质粒,利用家蚕细胞瞬时表达系统分析其转录活性以及昆虫保幼激素类似物(JHA)、蜕皮激素(20-OH-ecdysone)和滞育激素(DH)对其活性的影响.结果表明:1395 bp的Bmdhr启动子活性显著低于972 bp的Bmdhr启动子,这说明Bmdhr启动子在-941~-1364 nt区间存在负调控元件.JHA浓度为2,4,6μg/mL时,极显著地增强启动子活性;浓度为1μg/mL时活性显著减弱,而为8μg/mL时则活性极显著减弱.20-OH-ecdysone对Bmdhr启动子活性的影响具有剂量效应,低浓度(1,2μg/mL)时显著增强启动子活性;浓度为4μg/mL时,启动子的活性显著减弱;但当浓度继续升高时,启动子活性又极显著增强.DH对Bmdhr启动子活性的影响同样具有剂量效应,其浓度为10~40 nM时,显著增强启动子活性;而当其浓度达到60 nM时,启动子活性变化不显著.%To study the molecular mechanism of silkworm (Bombyx mori) diapause, two heterogeneous promoter fragments,1 395 bp and 972 bp,of diapause hormone receptor gene (Bmdhr) were cloned into pGL3.0 basic vector to construct reporter plasmids , respectively .The effects of foreign insect hormones including juvenile hormone ana -logue ( JHA) , 20-OH-ecdysone and diapause hormone ( DH) on regulation of Bmdhr promoter activities were ana-lyzed in BmN cells .The results showed that the activity of 1 395 bp promoter fragment was significantly lower than that of 972 bp one, implying that there is a negative regulation element between -941 and-1364 nt of Bmdhr pro-moter region.JHA of 2, 4 and 6μg/mL increased the promoter activity by 1.5~2.1 folds, but JHA of 8μg/mL decreased the promoter activity significantly .The effects of ecdysone on the Bmdhr promoter activity revealed a dosage dependent profile , low concentration ecdysone (1, 2μg/mL) increased the promoter activity significantly , ecdysone of 4μg/mL strongly suppressed the promoter activity .When ecdysone concentration increased from 6μg/mL to 8 and 10μg/mL,the promoter activity recovered and increased significantly again .The effects of DH re-vealed a dosage dependent profile too , low concentration DH (10, 20 and 40 nM) significantly enhanced the pro-moter activity , but high concentration DH (60 to 100 nM) showed no significant effect .
摘要:Considering the section area loss and the decrease of bonding strength of steel bars caused by the cor -rosion of chlorides and strength change of concrete by erosion of sulfates , the finite element analysis of the corro-ded reinforced concrete beam is established .To simulate the bearing capacity of the beam , analysis is compared with the results of the experiment .It turns out that it is reliable and accurate to use nonlinear finite element anal-ysis for the corroded reinforced concrete beam .%考虑到氯盐对钢筋锈蚀会引起钢筋横截面损失和粘结强度下降,硫酸盐对混凝土侵蚀会引起混凝土强度改变,因此,建立受腐蚀钢筋混凝土( reinforced concrete ,RC)梁的有限元分析模型,利用大型有限元ANSYS分析软件,对腐蚀梁的受力性能进行模拟分析,模拟结果与实验结果吻合,说明采用非线性有限元方法分析锈蚀梁受力性能正确有效。
摘要:The anomaly in machining process can lead to the production of quality fluctuation .These anomalies are hard to be found .And the secondary processing and scraped products can not be avoided .It is important to analyze the hidden quality trouble and find a solution to optimize the process .At the same time , process quality is under the influence of various factors .These factors influence each other and it is difficult to optimize one fac-tor alone .Therefore , a new process optimization method was proposed .This means used the quality management way to monitor the process all times , and it could find the abnormal process .Then, the orthogonal test was used to make the comprehensive optimization of machine tool , cutting tool and cutting parameters .This new method can improve the technology and avoid the quality accident .%机械加工工艺的异常会导致质量波动的产生,异常很难被发现,容易造成二次加工甚至报废品的出现。因此,查找质量隐患,分析原因,找到解决办法是工艺优化的重要途径。加工工艺的好坏受到多种因素影响,这些因素之间相互影响、相互作用,单独对一种因素进行优化往往难以达到理想目标。针对这一问题,提出了运用质量管理的手段实时监控工序状态、查找异常工序,利用正交试验,综合优化机床、刀具、切削参数等工艺条件的工艺优化方法,达到改进工艺、避免质量事故的目的。
摘要:Programming through a UDF definition of nanofluid phase change source term , the Al2 O3 -H2 O nanofluid boiling process is simulated in the horizontal tube ,and the boiling flow pattern characteristics analyzed in the nanofluid horizontal tube .The results show that for boiling in the horizontal pipe , the gas content increases along the length direction , but in the same interface position , the nanofluid of air content is higher than that of pure water of air content ,helpful to enhance the disturbance of the fluid .For different concentrations of Al 2 O3 -H2 O nanofluid flow pattern , particle concentration has little effect on nanofluid tube boiling process .Nanofluid is then compared with pure water flow pattern , the results show that the Al 2 O3 -H2 O nanofluid makes tube boiling more intense and easier .It will improve the flow characteristic of the horizontal circular tube .%利用UDF编程定义纳米流体相变源项,对Al2O3-H2O纳米流体在水平管内的沸腾过程进行了数值模拟,分析研究了纳米流体在水平管内沸腾的流型特点,结果表明水平管内沸腾蒸发产生的相变含气率沿着管长方向不断增加,但相同截面位置纳米流体的含气量高于纯水的含气量,有助于强化流体的扰动与混合。对于不同浓度的Al2O3-H2O纳米流体的流型研究表明:颗粒浓度对于纳米流体管内沸腾过程的影响不大。随后将纳米流体与纯水的流型进行比较,结果表明Al2O3-H2O纳米流体使得管内沸腾更剧烈,也更容易沸腾,这将改善水平圆管的流动特性。
摘要:对去离子水、不同浓度和不同充液率的TiO2/H2 O纳米流体重力热管进行了测试,给出了这些热管启动过程的温度分布图。结果表明:在恒温水浴加热的试验条件下,与去离子水热管相比,纳米流体热管蒸发段启动温度低并且启动时间短,其蒸发段和冷凝段的最大温差与去离子水热管相比较低;在50%~70%充液率范围内热管蒸发段的启动时间随着充液率的增大而增加;热管启动时间随着加热温度的升高而缩短;热管倾斜角度较小的情况下将使其启动性能变差。%Gravity heat pipes filled with DI water , TiO2/H2 O nanofluilds of different concentration and filling ra-tio were tested ,and the temperature distribution of their start-up processes was given .The result shows that under the test condition of constant temperature water bath , the heat pipes filled with nanofluids have a lower start-up temperature and a shorter start-up time in evaporation section compared with heat pipes filled with DI water , the biggest temperature drop between the evaporation section and the condensation section of heat pipes filled with nanofuilds was lower than that of heat pipes filled with water .The start-up time of heat pipes that have 50%~70%filling ratio in evaporation section increased with the increase of filling ratio , and it also increased by the in-crease of heating temperature .The small inclination angle has a bad influence on the start-up performance of the heat pipes .
摘要:文中在总结运营公路隧道的荷载特点、概括影响隧道荷载效应各种因素及其统计特征的基础之上,运用蒙特卡罗有限元法对厦门海底隧道海域Ⅳ类围岩下左洞某断面二次衬砌的荷载效应和弯矩的统计特征进行了计算和分析。研究结果表明:厦门海底隧道海域Ⅲ级(Ⅳ类)围岩下左洞某断面的二次衬砌结构最大弯矩发生在仰拱处,最大轴力发生在拱脚处;衬砌拱顶、拱腰以及拱脚和仰拱处的弯矩不拒绝服从对数正态分布;衬砌拱顶、拱腰以及拱脚和仰拱处的荷载效应不拒绝服从正态分布。%After summing up the operating tunnels′loading features and the statistical characteristics from all the factors influencing tunnel load effect , this paper applies Monte Carlo finite element method to the analysis and calculation of the load effect and bending moment characteristics of a section′s secondary lining of the left hole , which is in Ⅳsurrounding rocks of sea area of Xiamen subsea tunnel .The conclusions are as follows:The maxi-mum bending moment , which is of a section′s secondary lining structure of the left hole under the Xiamen subsea tunnel grade Ⅲ(Ⅳ class) wall rock,occurs at the invert, and the maximum axial force is at the arch of the foot;the bending moment of lining vault , arch back , arch of the foot and invert do not refuse to obey a lognormal distribution;the load effect of lining vault , arch back , arch of the foot and invert do not refuse to obey the normal distribution .
摘要:In view of the fact that most exisiting micro in-pipe robot have complex structure and narrow application field,by using simple-structure,and convienient-design insititution a in-pipe robot is designed ,which can bring compound movement .Taking advantage of the strong adapbility of the peristalsis in-pipe robot ,the smooth opera-tion of the tensioner type robot and high power ratio miniature motor technology ,the peristalsis-tension-type micro in-pipe robot is designed which is driven by miniature stepping motor .To prove its movement feasibility , the ki-nematics analysis , dynamics analysis and virtual prototype simulation are carried out for the robot .%针对现有微型管道机器人多为结构复杂,应用领域较窄等现状,力求以结构简单、设计方便的机构来实现复杂运动为设计主线,综合蠕动式管道机器人适应性强,张紧式机器人运行平稳等优点,以及目前逐步成熟的功重比高的微型电机技术,设计了一种新型的微型步进电机驱动的蠕动-张紧式微型管道机器人。并对管道机器人进行了运动学和动力学分析以及虚拟样机仿真,验证了其运动可行性。
摘要:采用密度泛函理论中的B3LYP方法,在LANL2DZ基组水平上优化了WmBn(m+n≤7)团簇的几何结构,得到了它们的基态构型,并对其自然键轨道( natural bond orbital ,NBO)以及振动光谱进行了计算研究。结果表明:团簇中NBO电荷分布状况与团簇的对称性相关;W原子比B原子电荷调节能力强,易与其他原子形成化学键;最大频率以及最强峰值对应的振动模式大部分是B原子或W原子的伸缩振动以及摇摆振动。%Geometric structures of WmBn (m+n≤7) clusters are optimized by using the density functional theory at the B3LYP/LANL2DZ level.For the ground state configurations , the polarizability, magnetism,NBO(natural bond orbital ) and vibrational spectrum are analyzed .The calculated results show that the charge distribution of NBO is related to the symmetry of cluster;W charge regulation capability is better than B , which is easy to form chemical bonds;the strongest peak vibration mode corresponds to stretching or wagging vibration of atom B or W .
摘要:讨论了一种高速三体船的快速性综合优化设计问题,在对一型三体船进行系列模型试验的基础上建立了快速性综合优化设计数学模型.采用遗传算法作为优化方法,编制了C++优化计算程序,基于大量的计算,确定了合理的进化代数;得到了快速性指数在傅汝德数Fr为0.32~0.44之间随速度和船长的变化曲线.文中提出的优化方法及计算结果可为高速三体船初步设计提供技术支撑.%This article discusses a high-speed trimaran rapidity integrated optimization design problem .First are a series of trimaran model tests are carried out , then a mathematical optimization model of the high-speed trimaran is established by using the genetic algorithm , and the C++language is used to program the procedure .The opti-mum steady number of generations is determined;the rapidity index as a function of speed and length of the tri-maran is obtained for Fr between 0.32 and 0.44 ,The optimization method and results of calculation presented in this paper provide a technical support for the preliminary design of high-speed trimarans .
摘要:Automatic machine has larger recoil energy in the firing process , and these recoil energy is consumed by the buffer.In order to study of the relationship of buffer main performance parameters-stiffness, damping and pre-pressure changes automata recoil process as well as that of the maximum after sitting speed and friction , kine-matics simulation software is applied to an automatic machine buffer .Studies have shown that increasing the damping coefficient is more than effective reducing the stiffness in easing the impact , and it does not need to ex-tend the recoil stroke;taking into account the adverse effects of the resonance the buffer movement of the piston and cylinder shape accuracy , we use the finite element modal analysis method to study the relationship of strength and structure of dynamic buffer .The results of the analysis of buffer optimization design of parameters provide a reference , and ultimately reduce the recoil impact and improve shooting accuracy and intensity .%自动机在射击过程中具有较大的后坐能量,这些后坐能量通过缓冲器进行消耗。为研究缓冲器主要性能参数---刚度、阻尼、预压力的变化对自动机后坐过程的影响以及最大后坐速度与摩擦力的关系,利用运动学仿真分析软件对某自动机缓冲器后坐过程与刚度、阻尼、预压力的关系进行了研究。研究表明,通过提高阻尼系数比降低刚度更能缓和冲击,且不需要延长后坐行程;考虑到共振对缓冲器活塞运动以及筒体形状精度的不利影响,利用有限元模态分析方法对缓冲器动强度与结构的关系进行了研究。分析结果为缓冲器性能参数优化设计提供参考,最终达到降低后坐冲击,提高射击精度和密集度的目的。
摘要:针对海上环境气候复杂,模拟困难等原因,本系统在基于OSG三维渲染引擎的基础上,借助OsgOcean场景实现了第一视角的海洋场景漫游,包括船舶模型的调换,天气变化,键盘事件响应来控制船舶运动。首先通过将OSG视景窗口嵌入MFC框架下,并在OSG核心类cOSG中响应海洋场景的生成;其次在模型节点中通过添加和移除节点,动态实现船舶模型的加载和转换,然后通过天空盒中阳光在海面产生的不同光照效果,利用着色器,渲染不同气候下海面的颜色;最后通过OSG三维渲染引擎中的粒子效果,将自定义粒子模块实时加载到场景中,用来模拟大自然中的雨、雪效果。%Since the maritime environment is complicated and it is difficult to simulate , an ocean scene ramble system has been designed based on the OSG 3-D rendering engine and osgOcean .The system included the fol-lowing functions:switch of ship models , weather variations and ship movements controlled through keyboard e-vents response .At first, the OSG view window was embedded in the MFC framework , the ocean scene was gen-erated in the core class cOSG , then by adding and removing the model nodes , ship models were loaded and switched dynamically .After this,the color of ocean surface under different climates was rendered by the shader based on the light reflection and refraction of the ocean surface .At last,the rain and snow effects were simulated by adding the particle system of OSG rendering engine to the ocean scene .
摘要:The theory of the entropy on the non-compact spaces and the theory of the local entropy on the com-pact spaces in the topological dynamical system are studied .Combining the variational principle of the two kinds of entropy ,the property of the local topological entropy under the specific mapping and the variational principle of local entropy on the non-compact spaces,hμ(T,U)=htop(T,U),are obtained.%文中主要对拓扑动力系统中关于非紧空间上的熵的理论和紧致空间局部熵的理论进行了分析和研究。结合这两种熵的变分原理,文中得到了关于在特定映射下局部拓扑熵的性质和非紧空间上局部熵的变分原理:hμ( T, U )=htop(T,U)。
摘要:系统观测目标误差渗透着系统误差和随机误差,系统误差和随机误差的分离与溯源理论和应用一直是误差分析的难点和热点。文中基于系统误差和随机误差的互相关系与传递特征,提出了以传递函数为基础的误差传递模型,并基于该模型,将复杂系统划分为若干个子系统,分析了各子系统在观测目标误差中的主次作用( primary and secondary position a-nalysis,PSPA)。算例表明,该理论能够分析得出引起观测误差灵敏度较高的子系统,这对于误差溯源、分析和控制误差,提高观测目标的精度具有一定的指导意义。%System error and random error are usually included in the error of target parameter .The theory and application about the separation and tracing for both are always the hot and difficult topic in research .An error propagating model based on propagating function is proposed .The primary and secondary position analysis ( PS-PA) of the subsystem error propagating in the complex system is based on this model , while the whole complex system can be divided into several subsystems .An example shows that this model can analyze and determine the relative crucial subsystem in error tracing .There may be significant inspiration in how to find the origin of error and how to analyze and control the error .The most important is that the model proposed above provides a path for improving the accuracy of the target parameter .
摘要:On the base of validating the calculation model of a turbocharged diesel on the plain ,three-dimension-al numerical simulation of in-cylinder working process at 2 900 and 4 250 meters above sea-level is carried out . The results show that ,compared with the situation on the plain ,the peak value of heat release rate lowers , but the crank angle of the center of heat release rate curve advances ,combustion temperature increases rapidly , the maxi-mum temperature rises 309 K and 357 K.The maximum combustion pressure is decreased by 4.9 MPa and 5.53 MPa,respectively;NOx appears earlier and NO x emission decreases with an increase in altitude .The research pro-vides reference for optimization of the turbocharged diesel′s performances at a high altitude .%在验证平原下某增压柴油机计算模型基础上,对某增压柴油机在海拔2900 m和海拔4250 m条件下缸内工作过程进行了三维数值计算.计算结果表明:与平原相比,随着海拔的升高,放热率峰值下降但放热率重心前移,缸内温度迅速升高,缸内最高温度分别上升309和357 K;缸内最高燃烧压力分别下降4.9和5.53 MPa;NOx 出现时间随海拔上升而稍微提前,NOx 排放量随海拔的上升而下降.研究结果为优化高原增压柴油机的性能提供了参考.
摘要:KNN算法是比较适合于文本分类的一种分类算法,但由于其计算复杂度会随着训练集规模的增加而线性增加,从而限制了它的实际应用效果。通过改变对近邻点的搜索策略,提出了一种改进型的KNN算法。该算法在对最近邻的选择过程中,放弃传统算法中遍历所有样本的做法,而是通过逐渐逼近的思想来寻找最近邻点。实验证明,该方法在保持和传统的KNN算法几乎一样的精度性能前提下,可以明显降低算法的计算复杂度,降低时间开销,取得了较满意的结果。%KNN algorithm is a classification algorithm suitable for text classification , but because its computa-tional complexity increases linearly with the increase in the size of the training set ,its practical application is lim-ited.In this paper, we propose an improved KNN algorithm by changing the strategy of searching the nearest neighbor points .The algorithm abandons the practice of the traditional algorithm to traverse all samples in the se-lection process nearest neighbor , and utilizes the idea of gradual approximation to find the nearest neighbor .Ex-perimental results show that the proposed algorithm ,under the premise of maintaining almost the same precision performance of traditional KNN algorithm ,can significantly reduce the computational complexity of the algorithm and running time .
摘要:In the paper , the protective equipment of bridges was studied .The new type of protective equipment , which was the double-folding and rectangular column sandwich steel protective devices ,was suggested .The AN-SYS/LS-DYNA, a nonlinear dynamics finite element software , was applied to simulate the crashworthiness per-formance of the rectangular column steel sandwich plate and the double-folding steel sandwich plate , and the crashworthiness performance factors of the two sandwich plates were analyzed for different structure parameters to optimize the overall crashworthiness sandwich plate .The results showed that the rectangular column sandwich plates were better than double-folding sandwich plates in crashworthiness .Then, two sandwich plates were used to replace the outsize steel plates of the traditional box-protective device .We found that the overall crashworthi-ness of two sandwich steel protective devices were better than the traditional box-protective device .The crashwor-thiness performance of the rectangular column sandwich steel protective device is the best .%通过对桥梁防护装置研究,提出四棱柱式与双折叠式夹层板桥梁防护装置,采用ANSYS/LS-DYNA非线性有限元对其耐撞性能进行数值仿真,探讨两种夹层板防护装置的尺寸参数对其性能的影响。研究结果表明:经结构优化后四棱柱式夹层板的耐撞性能优于双折叠式;分别用两种夹层板替换传统钢质箱式防护装置的外围板,两种夹层板式防护装置的耐撞性能均优于传统钢质防护装置,而四棱柱式防护装置的性能最佳。
摘要:Based on saturated-unsaturated seepage theory and the shear strength theory , we study the effect of rainfall intensity and rainfall duration on the soil slope safety , focusing on the comparison and analysis of the short time heavy rainfall and long time weak rainfall .Analysis results show that for a fixed saturated permeability coefficient , safety coefficient decreases as the rainfall intensity and rainfall duration increase , but it increases with time after rain;short time heavy rains make top soil of the down slope more likely to achieve saturation , and long time weak rainfalls have greater influence on the slope soil , the stability are greatly reduced in both cases . Long time weak rainfall increases the chance of landslide .%基于饱和-非饱和渗流理论与非饱和土的抗剪强度理论,研究了降雨强度、降雨历时等降雨要素对土质边坡安全系数的影响规律,并且重点对短时强降雨、长时弱降雨2种降雨形式进行了对比分析。结果表明:在饱和渗透系数一定的情况下,安全系数随着降雨强度、降雨历时的增加而不断减小,但在降雨结束后,安全系数又随时间的增长开始增大;短时强降雨下边坡上部土体更容易达到饱和,而长时弱降雨对边坡土体的影响更大,两者的稳定性都大大降低,但长时弱降雨下的滑坡危害程度更大。
摘要:利用水动力分析软件AQWA研究了内转塔式单点系泊参数对海上浮式生产储油船FPSO( floating production,stor-age and affcoading system )系统动力效应的影响特性,定量分析了内转塔位置、系泊缆材料分布、系泊缆预张力、系泊缆数量、系泊缆布置形式等参数对FPSO系统动力效应的影响,对每个系泊参数采取多个特征量进行比较分析,计算结果表明:转塔位置距船艏柱25%Lpp时风标效应及定位效果最好,多成分系泊缆材料分布采取下端钢链9%、聚酯缆90%、上端钢链1%时,系泊缆数量取9根且为3组×3根/组布置时定位效果最好,缆绳受力最小。以FPSO水平偏移量与系泊缆的安全系数为目标,提出了一套系泊系统的优选方案,计算结果表明系泊性能优良,与初步设计方案相比有了显著地提高。文中的计算及分析结果对内转塔式FPSO系泊系统的设计具有一定指导意义。%In this paper , the influence of BTM ( Buoyant Turret Mooring ) system parameters on dynamic re-sponse of FPSO system was analyzed by software AQWA .The influence of parameters , such as turret location , materials distribution , pre-tension of mooring lines , the number of mooring lines , layout of mooring lines etc ., on dynamic response of FPSO system was analyzed quantitatively .Several characteristics were comparatively ana-lyzed for each mooring parameter .The results showed that when turret was located at 25%Lpp, the system had best weather vane and positioning effect .If 9%chain,90% polyester,1%chain was taken as multi-component mooring line, and mooring lines were arranged as 3groups ×3/group, the system would have positioning effect and the lines would have minimum force .An optimized proposal of mooring system was suggested by comprehen-sively considering the horizontal displacement of FPSO and the safety factor of mooring lines .The result showed that the optimized mooring system would have excellent performance , and it was significantly improved compared with the initial program .The conclusion will be helpful for the design of the BTM .
摘要:On the basis of summarizing the methods of numerical flow noise prediction , a ship′flow noise spectrum and its equivalent acoustic source are determined numerically by combining the large eddy simulation (LES) and boundary element numerical acoustics in the frequency domain .Dynamic Smagorinsky-Lilly Model ( DSM) is ap-plied to subgrid-scale stress tensor in the process of LES simulation .The fluctuation pressure and normal velocity distribution on the hull surface are treated as flow noise source with conservative transformation to the acoustic nodes.It is shown that the total sound source level of flow noise reaches 133dB in 20Hz~2kHz frequency band and 143.3dB within 20kHz broadband at the speed of 14 knots.The main source of flow noise comes from vorticity induced by the ship wave .And it concentrates mainly in 100Hz~10kHz band.Exactly, the vorticity of sonar shell and hull plays an important role in radiated noise .More attention is needed to pay to it in design .A new practical method is presented to measure the surface ship flow noise in the field of naval architecture .%在梳理流噪声数值预报方法的基础上,采用流场大涡模拟( large eddy simulation ,LES)和声学边界元( boundary ele-ment method,BEM)方法在频域内计算预报了船体流噪声谱曲线,求取了其等效声中心.LES计算时选用动力学Smagorin-sky-Lilly( dynamic Smagorinsky-Lilly,DSM)亚格子应力模型,流噪声由船体壁面脉动压力和法向速度特性决定,声源节点和声节点变量传递采用一对一的守恒传递方式.结果表明:某型船在航速14 kn时,裸船体流噪声在20 Hz~2 kHz频段内总声源级为133dB;当计算有效频段扩展到20 kHz时,总声源级达143.3 dB.流噪声主要来源于兴波引起的涡量,且主要集中于100 Hz~10 kHz频段.球首尾流区和船体尾涡区对流噪声辐射量贡献明显,特别是球首尾流区,对全频段都有明显的贡献,为水面舰艇流噪声研究提供了一条新的途径.
摘要:By choosing surfactant polyvinyl butyral (PVB) and polyvinylpyrrolidone (PVP), as well as the cou-pling agent KH550 and KH570 as surface treating agents ,we study the influence of adding surface treating agents on dispersity of copper indium sulfide nanocrystalline , which was synthesized via a solvothermal method .Struc-ture, atomic ratio, morphology and light absorption performance of the nanocrystal were characterized by X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), Scanning Electron Microscope (SEM), and UV-Vis spectrophotometer .Results showed that with the small amount ( 0.1% of total mass ) of coupling agent KH570 and surfactant PVB and PVP , the agglomeration of CuInS 2 nano-crystals could be improved .Among them KH570 and PVP was better .%选用表面活性剂聚乙烯醇缩丁醛( PVB)和聚乙烯吡咯烷酮( PVP),以及偶联剂KH550、KH570等表面处理剂,来研究体系中添加表面处理剂对溶剂热法合成的CuInS2纳米晶体分散性的影响.利用X 射线粉末衍射仪、EDS能谱、扫描电镜( SEM)和紫外可见近红外分光光度计对纳米晶体的结构、原子配比、形貌和光吸收性能等进行表征.结果表明:体系中添加少量(总质量的0.1%)表面处理剂制备的CuInS2纳米晶体团聚现象能得到有效改善,其中偶联剂KH570和表面活性剂PVP改性效果佳.
摘要:In recent years , the master-slave robot system is widely used in many different fields , such as medical treatment and deep-sea field.The control strategy of master-slave robot system is studied on the basis of summari-zing the existing research results .Incremental position control strategy is used to establish the master-slave work-space mapping conveniently , position feedback is adopted to improve control precision of the system , the problem of motion ratio change is solved and the position control strategy is proved through the built system .The results show the accuracy and instantaneity of the position strategy .Position error is introduced into force feedback strat-egy, the stability of the system is analyzed and the effectiveness of the force control strategy is tested through MATLAB/Simulink and experiment .%近年来主从式机器人系统被广泛应用在医疗、深海等非结构性环境。在现有研究成果的基础上,研究了主从式机器人系统的控制策略。采用增量式位置控制,易于建立主端与从端的工作空间映射,并增加位置反馈提高系统的控制精度;解决了主从运动比例变化的问题;并通过搭建的主从机器人系统对位置控制策略进行验证,结果表明了系统位置控制策略的准确性和实时性。将主从位置误差引入系统的力反馈控制策略,分析系统的稳定性,并通过MATLAB/Simulink对力反馈策略进行仿真及实验验证,仿真与实验结果验证了所建立控制策略的有效性。
摘要:预测船体复杂结构的焊接变形对制造工艺设计和精度控制具有重要的工程价值.基于固有应变理论,利用船体结构焊接变形预测专用软件Weld-sta对多用途船双层底结构焊接变形进行了预测,发现船长方向收缩最大变形量为13.2 mm,船宽方向最大变形量14.5 mm.通过数值模拟结果与实验实测值的对比,可以得到软件计算的精度超过80%,验证了固有应变理论及软件用于焊接变形预测的可靠性,并在此基础上针对船体总段船台合拢的焊接变形进行了预测,发现焊接总收缩变形量为50.339 mm,与实际加工经验基本吻合.根据此结论可以针对各船体总段预留合理的焊接变形收缩量,验证了固有应变为基础的弹性板单元有限元预测法在船体总段合拢焊接中应用的可行性.%Prediction of welding deformation of hull complex structure has important engineering value to control the manufacturing process design and precision control .Based on the inherent strain theory , the prediction of welding deformation of Weld -sta software for the welding deformation is applied to multi-purpose ship double bot-tom structure of hull structure .We find that the captain direction shrinkage maximum deformation is 13.2 mm and the maximum deformation of beam direction is 14.5 mm.Through the comparison between numerical simula-tion results and experimental data , the accuracy of calculation is verified to be greater than 80%, and the inher-ent strain theory and the reliability of welding deformation prediction software are tested;the welding deformation of hull sections berth closure are predicted , welding shrinkage deformation is found to be 50.339 mm, in agree-ment with the practical experience in processing .The conclusions can be used to reserve the reasonable welding deformation and shrinkage , verifing the feasibility of the inherent strain based elastic plate finite element method to be used in the welding of ship hull section closure .
摘要:Based on hawse pipe design in ship construction in physical state of tensile anchor under test ,by tak-ing a 49 000 DWT product carrier as the research object , the tensile anchor experiment simulation is carried out , the science and feasibility of the simulation system is verified .The Solid Works software is used in the simulation system to implement the general method from design , modeling to simulation of the ship anchor , anchor chain , and the other standard parts .We established a database model , imported the ship stem model , and then assem-bled, added constraints and force , and simulated the tensile anchor test .%针对船舶建造中的锚链筒设计物理状态下的拉锚试验,以某49000 DWT成品油轮为研究对象,对其进行拉锚试验仿真,验证仿真系统的科学性和可行性。该仿真系统运用Solid Works软件实现从设计、建模到仿真的一般方法,对船舶锚以及锚链等标准件建立数据库模型,导入或者建立船艏模型,然后装配,添加约束力,进行拉锚试验仿真。
摘要:采用5种不同成分的锌铝药芯钎焊丝钎焊铝/铜接头,研究钎料成分对接头剪切强度和耐蚀性的影响。研究结果表明:对于同成分的锌铝药芯钎焊丝,采用火焰钎焊的铝/铜接头抗剪强度比炉中钎焊高,Zn80Al20药芯钎焊丝钎焊的铝/铜接头强度最高;随钎料中Al含量降低,铝/铜接头的耐蚀性变差,Zn72Al28药芯钎焊丝钎焊的铝/铜接头耐腐蚀性最好。相同条件下,火焰钎焊铝/铜接头的耐蚀性明显好于炉中钎焊的接头;Zn80Al20药芯钎焊丝钎焊的铝/铜接头钎缝组织呈块状。锌铝药芯钎焊丝中适中的Zn,Al含量有利于使铝/铜接头铜侧界面得到固溶体组织,并避免铝侧母材的过度熔蚀。%Five kinds of Zn/Al flux cored wires with different compositions were used to braze Al /Cu joints, and the joints′shear strengths and corrosion resistances which were affected by compositions were studied .It is shown that for the Zn/Al flux cored wires with the same compositions ,the shear strength of the joint brazed by flame bra-zing is higher than furnace brazing , and the shear strength of the joint brazed by Zn 80Al20 flux cored wire is the highest.The corrosion resistance of Al/Cu joint gets worse with the decrease of Al in the solder and that of Al /Cu joint brazed by Zn72Al28 flux cored wire is the best .Under the same conditions ,the corrosion resistance of Al/Cu joint brazed by flame brazing is obviously better than furnace brazing and the microstructure of Al /Cu joint brazed by Zn80Al20 flux cored wires is massive .Moderate contents of Zn and Al in the Zn/Al flux cored wire are beneficial to gain solid solution structure in the Cu side of Al /Cu joint and avoid the excessive corrosion of base metal in the side of Al .
摘要:在由15 g/L Na2 SiO3、12 g/L NaAlO2、3 g/L Na2 B4 O7、5 mL/L C3 H8 O3、5 g/L C6 H5 Na3 O7及1~4 g/L NaOH组成的硅铝复合电解液中,利用微弧氧化技术在AZ91D镁合金基体上制备了一系列陶瓷膜层.利用扫描电镜、膜层测厚仪分别研究了陶瓷膜层的微观结构及厚度;采用全浸泡实验和交流阻抗实验测试了膜层在3.5%NaCl溶液中的耐蚀性能.结果表明:随着NaOH含量的增加,微弧氧化过程中的起弧电压和终止电压均呈线性下降;膜层的耐蚀性随着NaOH含量的增加先提高后降低,膜厚的变化趋势与其耐蚀性的变化趋势基本一致;NaOH含量的变化主要影响膜层内部致密层的耐蚀性能;当NaOH含量为2 g/L时,膜层最厚,膜层较致密,因而具有较好的耐蚀性能.%Ceramic coatings were obtained on AZ91D magnesium alloy by microarc oxidation in a silicate-alumi-nate based composite electrolyte containing 15 g/L Na2 SiO3 , 12 g/L NaAlO2 , 3 g/L Na2 B4 O7 , 5 mL/L C3 H8 O3 , 5 g/L C6 H5 Na3 O7 and 1~4 g/L NaOH.The morphology and thickness of ceramic coatings were exam-ined by scanning electron microscopy ( SEM ) and layer thickness meter .The corrosion resistance of ceramic coatings in a 3.5%NaCl neutral solution was evaluated by immersion test and electrochemical impedance spec-troscopy ( EIS) .The results show that striking voltage and final voltage during the MAO process decrease gradu-ally as the concentration of NaOH increases .With the increasing of NaOH concentration in the electrolyte , the corrosion resistance of coating increases first and then decreases gradually .The variation trend of coating thick-ness is the same as that of corrosion resistance .The concentration of NaOH in the electrolyte mainly affects the corrosion resistance of the inner dense layer .The coating obtained in the electrolyte containing 2 g/L NaOH ex-hibits a better corrosion resistance due to the relatively compact microstructure and thick coating .
摘要:The finite element method can accurately simulate the stress distribution and deformation behavior of engineering machinery and equipment , but the premise is to use appropriate elements .More important are the boundary conditions in line with the actual situation .An improved scheme is put forward to solve the existing problems in finite element analysis on the lower structure of the crawler crane .The reasonable selection of the number , shape and arrangement of elements with less number of units , can lead to more accurate results with less calculation time .In order to accurately apply boundary conditions , the gap element is used to simulate the contact between the ground and the track .Beam elements are used to simulate the rotary supporting and the fix-ing bolts, so that the local stiffness is more close to the actual situation and the load on the frame of the distribu-tion is real .The arm operation condition , the load condition , and the turn condition are considered during simu-lation.Max boom raising , max rated load lifting and turning are the critical load case to be considered .The re-sults are compared with the measured ones , and the feasibility of this method is tested .%有限元方法能够较准确模拟工程机械局部受力和变形行为,但前提是采用合适的单元,更重要的是边界条件符合实际工况。针对履带式起重机下车有限元分析中存在的问题,提出了改进的分析方法。通过将单元数量、形状和排列方式进行配合,可以在使用较少单元数量的情况下获得较准确的结果。为了准确施加边界条件,用间隙单元模拟地面和履带的接触;用梁单元模拟回转支撑和固定螺栓,使局部刚度更接近实际情况,并使载荷在车架上的分布更真实。计算时考虑3种工况:起臂、吊载和转弯工况。将应力计算结果与实测值进行对比,大致吻合,证明了方法的可行性。
摘要:Attitude updating algorithm has a profound impact on the navigation accuracy in the strapdown inertial navigation system ( SINS) .Restraining the noncommutativity error and error accumulation is a remarkable effect of the rotation vector algorithm .Taking the real-time and accuracy of attitude update into consideration , this pa-per deduces the details of error compensation term based on the theory of twin-sample rotation vector and the cal-culation results are optimized in the conning motion to improve the dynamic adaptability of the algorithm , forming a new improved twin-sample rotation vector algorithm .The experiment shows that the improved twin-sample rota-tion vector algorithm is much stronger in meeting the real-time and accuracy requirements than the traditional quaternion algorithm in the field of attitude update of SINS .%在捷联惯导系统中,姿态更新算法会对导航精度产生至关重要的影响。旋转矢量法在抑制不可交换性误差及其累积效应方面具有显著的优点。为兼顾姿态解算的实时性与精确性,文中基于旋转矢量双子样算法原理推导其误差补偿项,并进行了圆锥运动环境下的算法优化,以提高算法的动态适应性,从而形成了优化的旋转矢量双子样算法。最后通过与传统四元数法进行对比分析,表明在捷联惯导姿态解算中,采用优化旋转矢量双子样算法不仅可较好满足系统实时性要求,同时还能较明显地提高解算精度。
摘要:基于双分布格子Boltzmann模型,建立了适合于流体流动和换热的热格子Boltzmann模型。温度分布函数中采用D2Q9离散速度模型。以热格子Boltzmann模型,模拟了方腔内自然对流的形成及其演化,通过与相关文献的计算结果对比可以发现,热格子Boltzmann模型在处理流体流动与传热方面存在着独特的优点,文中建立的数值模拟计算方法和程序是切实有效的。%This paper established the thermal Lattice Boltzmann model of fluid flow and heat transfer , which is based on double lattice Boltzmann distribution model [1] .The temperature distribution adopted D 2Q9 velocity model.Based on this thermal lattice Boltzmann model , this paper simulated the formation and evolution of the natural convection of the square cavity .Comparing the simulation results with the traditional calculation results , it can be found that the thermal lattice Boltzmann model on fluid flow and heat transfer has the unique advantage , and the methods and procedures established in this paper are effective .