Oblique Cutting Based Mechanical Model for Insertion Torque of Dental Implant

The insertion torque of a dental implant is an important indicator for the primary stability of dental implants.Thus,the preoperative prediction for the insertion torque is crucial to improve the success rate of implantation surgery.In this present research,an alternative method for prediction of implant torque was proposed.First,the mechanical model for the insertion torque was established based on an oblique cutting process.In the proposed mechanical model,three factors,including bone quality,implant geometry and surgical methods were considered in terms of bone-quality coefficients,chip load and insertion speeds,respectively.Then,the defined bone-quality coefficients for cancellous bone with the computed tomography(CT)value of 235–245,345–355 and 415–425 Hu were obtained by a series of insertion experiments of IS and ITI implants.Finally,the insertion experiments of DIO implants were carried out to verify the accuracy of developed model.The predicted insertion torques calculated by the mechanical model were compared with those acquired by insertion experiments,with good agreement,the relative error being less than 15%.This method allows the insertion torque for different implant types to be quickly established and enhances prediction accuracy by considering the effects of implants’geometries and surgical methods.

Prediction of Dynamic Cutting Force and Regenerative Chatter Stability in Inserted Cutters Milling

Currently, the modeling of cutting process mainly focuses on two aspects: one is the setup of the universal cutting force model that can be adapted to a broader cutting condition; the other is the setup of the exact cutting force model that can accurately reflect a true cutting process. However, there is little research on the prediction of chatter stablity in milling. Based on the generalized mathematical model of inserted cutters introduced by ENGIN, an improved geometrical, mechanical and dynamic model for the vast variety of inserted cutters widely used in engineering applications is presented, in which the average directional cutting force coefficients are obtained by means of a numerical approach, thus leading to an analytical determination of stability lobes diagram (SLD) on the axial depth of cut. A new kind of SLD on the radial depth of cut is also created to satisfy the special requirement of inserted cutter milling. The corresponding algorithms used for predicting cutting forces, vibrations, dimensional surface finish and stability lobes in inserted cutter milling under different cutting conditions are put forward. Thereafter, a dynamic simulation module of inserted cutter milling is implemented by using hybrid program of Matlab with Visual Basic. Verification tests are conducted on a vertical machine center for Aluminum alloy LC4 by using two different types of inserted cutters, and the effectiveness of the model and the algorithm is verified by the good agreement of simulation result with that of cutting tests under different cutting conditions. The proposed model can predict the cutting process accurately under a variety of cutting conditions, and a high efficient and chatter-free milling operation can be achieved by a cutting condition optimization in industry applications.

Analysis of Friction and Heat Transfer Characteristics of Tubes with Trapezoidal Cut Twisted Tape Inserts

The thermo-hydraulic properties of circular tubes with a twisted tape inside(used accordingly to induce turbulence and enhance heat transfer through the tube wall)are described for Reynolds Numbers ranging from 830 to 1990.Tapes twisted with the three distinct twist ratios are considered,namely,6,4.4 and 3.Air is used as the working fluid in several tests.For the sake of comparison,the standard tube with no insert is also examined.It is shown that in the presence of the twisted tape,the‘frictional factor’,‘Nusselt Number’and the‘thermal performance factor’are much higher than those obtained for the plain tube.Moreover,the tapes having the lowest twist ratio,i.e.,3,are more effective than the others in terms of heat transfer augmentation.The‘thermal performance factor’is greater than one for all the twisted tapes used in the experiments,which confirms the enhanced performances of the heat exchanger and the related savings in terms of total energy.

Comparing the Effectiveness of Coatings on Carbide andCermet Cutting Tool Inserts

A series of metal cutting experiments was performed on a CNC lathe to evaluate the performance of various coatings on different tool substrates. The workpiece material was plain medium carbon steel and the cutting tool materials were carbide and cermet inserts coated with various single as well as multilayer coatings. Machining was done under various cutting conditions of speed and feed-rate, and for various durations of Cutting. The output parameters studied were the cutting forces (axial, radial and tangential), the surface roughness of the workpiece, as well as the tool wear (crater and flank wear). From these results, the performances of the various cutting inserts are evaluated and compared. Results show that cutting forces are significantly lower when using coated cermets than when using coated carbides although different coatings on the same substrate also result in different cutting forces. However, there is less difference in the surface roughness of the finished workpiece for the various coatings and substrates.

Machinability of Hastelloy C-276 Using Hot-pressed Sintered Ti(C_7N_3)-based Cermet Cutting Tools

C-276 nickel-based alloy is a difficult-to-cut material. In high-speed machining of Hastelloy C-276, notching is a prominent failure mode due to high mechanical properties of work piece, which results in the short tool life and low productivity. In this paper, a newly developed Ti（C7N3）-based cermet insert manufactured by a hot-pressing method is used to machine the C-276 nickel-based alloy, and its cutting performances are studied. Based on orthogonal experiment method, the influence of cutting parameters on tool life, material removal rates and surface roughness are investigated. Experimental research results indicate that the optimal cutting condition is a cutting speed of 50 m/min, depth of cut of 0.4 mm and feed rate of 0.15 mm/r if the tool life and material removal rates are considered comprehensively. In this case, the tool life is 32 min and material removal rates are 3000 mm^3/min, which is appropriate to the rough machining. If the tool life and surface roughness are considered, the better cutting condition is a cutting speed of 75 m/min, depth of cut of 0.6 mm and feed rate of 0.1 mm/r. In this case, the surface roughness is 0.59μm. Notch wear, flank wear, chipping at the tool nose, built-up edge（BUE） and micro-cracks are found when Ti（C7N3）-based cermet insert turned Hastelloy C-276. Oxidation, adhesive, abrasive and diffusion are the wear mechanisms, which can be investigated by the observations of scanning electron microscope and energy-dispersive spectroscopy. This research will help to guide studies on the evaluation of machining parameters to further advance the productivity of nickel based alloy Hastelloy C-276 machining.

Simulation of the continuous casting process in a mold of free-cutting steel 38MnVS based on a MiLE method

A new method called mixed Lagrangian and Eulerian （MiLE） method was used to simulate the continuous casting process in a mold of free-cutting steel 38MnVS.The simulation results are basically in agreement with experimental data in the literature,achieving the three-dimensional visualization of temperature distribution,melt flow,shell thickness,and stress distribution of blooms in a mold.It is shown that the flow velocity of steel melt becomes smaller gradually as the casting proceeds.When the flow reaches a certain depth,two types of flow patterns can be observed in the upper zone of the mold.The first flow pattern is to flow downwards,and the second one is to flow upwards to the meniscus.The corner temperature is higher,and the thickness is thinner than those in the mid-face.The effective stress in the corner area is much bigger than that in the mid-face,indicating that the corner area is the dangerous zone of cracking.

Minimizing of the only-insertion insdel systems

A more recent branch of natural computing is DNA computing. At the theoretical level, DNA computing is powerful. This is due to the fact that DNA structure and processing suggest a series of new data structures and operations, and to the fact of the massive parallelism. The insertion-deletion system （insdel system） is a DNA computing model based on two genetic operations： insertion and deletion which, working together, are very powerful, leading to characterizations of recursively enumerable lan- guages. When designing an insdel computer, it is natural to try to keep the underlying model as simple as possible. One idea is to use either only insertion operations or only deletion operations. By helping with a weak coding and a morphism, the family INS4^7DEL0^0 is equal to the family of recursively enumerable languages. It is an open problem proposed by Martin-Vide et al. on whether or not the parameters 4 and 7 appearing here can be replaced by smaller numbers. In this paper, our positive answer to this question is that INS2^4DEL0^0 can also play the same role as insertion and deletion. We suppose that the INS2^4DEL0^0 may be the least only-insertion insdel system in this situation. We will give some reasons supporting this conjecture in our paper.

Computer Aided Design Technology for Convex Faceted Gem Cuts Based on the Half-Edge Data Structure

Aiming to increase the efficiency of gem design and manufacturing, a new method in computer-aided-design (CAD) of convex faceted gem cuts (CFGC) based on Half-edge data structure (HDS), including the algorithms for the implementation is presented in this work. By using object-oriented methods, geometrical elements of CFGC are classified and responding geometrical feature classes are established. Each class is implemented and embedded based on the gem process. Matrix arithmetic and analytical geometry are used to derive the affine transformation and the cutting algorithm. Based on the demand for a diversity of gem cuts, CAD functions both for free-style faceted cuts and parametric designs of typical cuts and visualization and human-computer interactions of the CAD system including two-dimensional and three-dimensional interactions have been realized which enhances the flexibility and universality of the CAD system. Furthermore, data in this CAD system can also be used directly by the gem CAM module, which will promote the gem CAD/CAM integration.

Numerical Simulation and Measurement of Air Temperature and Relative Humidity in an Olive Cuttings Tunnel Greenhouse

Understanding the environment of olive tree cuttings is a key factor in improving these plants’ rooting rate and survival. This study aims to develop a three-dimensional (3-D) Computational Fluid Dynamics (CFD) model for numerically assessing air temperature and relative humidity in an olive cuttings greenhouse under Mediterranean climatic conditions. The results are deduced from a steady-state simulation performed with recorded boundary conditions at 10:00 am, 12:00 pm, 02:00 pm, 04:00 pm, and 06:00 pm at different observation points. The calculations were validated using experimental data. The simulation errors of the air temperature were -0.8°C to 4.55°C, and errors of the leaf temperature were 0.07°C to 2.42°C, for the air relative humidity was -33.84% to -1.64%, and -10.1% to -13.54% for the relative humidity of the leaf air. Contour maps were obtained from the 3-D CFD simulations to evaluate the distribution of humidity and air temperature inside the greenhouse and the vicinity of the plant canopy. This study suggests that the developed 3-D CFD model can be a helpful tool to understand and optimize greenhouse operation for better crop quality.

Numerical study on the hydrodynamics behavior of a central insert microchannel

In this work, the computational fluid dynamics method is used to study the liquid hydrodynamics behavior in the microchannel without central insert(MC1) and the central insert microchannel(MC2), respectively. The maximum deviation between simulation and experiment is 24%. The formations of flow patterns are explained based on contours and force analysis where the flow pattern maps are established by two-phase flow rate. The effects of aqueous phase viscosity and two-phase flow rate on the characteristic sizes of each flow pattern are also explored. Specifically, four unconventional flow patterns are found in MC2, namely the unique droplet flow, the unique slug flow, the unique coarse annular flow and the unique film annular flow. Though the insert occupies part of the channel, the pressure difference in the channel is significantly reduced compared with MC1. Moreover, the insert significantly changes the formation velocity range of each flow pattern, greatly broadens the formation range of annular flow and also has an important influence on the characteristic size of the flow pattern. The organic-phase dimensionless axial size(Lo/W) and the dimensionless radial size(Do/W) of the droplet(slug) are negatively related to the aqueous-phase viscosity(μa) and flow rate(ua). The Do/W of the annular is negatively correlated with μaand positively correlated with organic-phase flow rate(uo). This study provides direct numerical evidence that the insert is key to the formation of bicontinuous phase flow pattern, as well as further strengthens our understanding of the flow characteristics and optimization design of insert microchannels.

基于VMD-SSA-LSTM考虑刀具磨损的数控铣床切削功率预测模型研究

传统的切削过程功率获取需要基于复杂的切削功率模型且很少考虑刀具磨损的影响,针对此设计了一种基于变分模态分解(VMD)、麻雀搜索算法(SSA)、长短时记忆(LSTM)神经网络的考虑刀具磨损的数控铣床切削功率预测模型,该模型无需解构数控铣床运行过程的能耗机理,基于一次性的历史实验数据即可实现数控铣床切削过程功率的高精度预测。首先,采用人工智能机器视觉技术对刀具磨损图片进行分析处理,获取刀具磨损图像的数字化特征,从而得到刀具最大磨损量;然后,建立基于VMD-SSA-LSTM考虑刀具磨损的数控铣床切削功率预测模型,利用VMD对数控铣床运行数据进行分解,采用SSA算法对LSTM神经网络超参数进行寻优,并将分解出的铣床运行数据分量输入到LSTM神经网络中,接着将每个分量的预测值相加,得到切削功率预测值;最后以面铣加工为例,将所提出的预测模型与BP神经网络、LSTM神经网络和传统模型进行对比分析,验证了所提模型的有效性和优越性。

铜凿剪纸风格化方法研究

铜凿剪纸是一种在铜箔上凿点并使用矿物质颜料上色的传统艺术形式,其成品光彩夺目。铜凿剪纸工艺复杂、制作时间长,对手工艺人的技术水平有很高的要求。为此,提出了一种铜凿剪纸风格化的方法,并设计、实现了一种计算机辅助铜凿剪纸设计工具,通过生成图像线稿、凿点图以及铜凿剪纸效果图,帮助手工艺人快速完成铜凿剪纸的创作和制作。将输入图像进行区域分割以提取图像的线条,生成图像线稿;定义了一种颜色损失函数,结合贪心算法和梯度下降法求解函数最小值得到最佳颜色映射方案;基于VGG-19网络对图像线条进行风格迁移,生成凿点图;将线条风格迁移图像与颜色迁移图像进行融合,生成铜凿剪纸效果图;基于PyQt5框架开发铜凿剪纸设计工具,设计了交互平台。实验结果表明,该方法能够实现图像的铜凿剪纸风格化,且效果接近真实的铜凿剪纸,支持手工艺人快速生成工艺流程中需要的图像线稿、凿点图以及效果图等相关材料,提高铜凿剪纸的制作效率,具有较高的应用价值。

非黏性堤防溃口发展过程计算模型

堤防是防洪工程体系的重要组成部分,一旦发生溃决将可能带来严重灾害损失,明确堤防溃口发展速率与水力要素之间的关系对于预测堤防溃决过程和洪水演进具有重要意义。通过对系列非黏性沙质堤防溃决试验结果进行整理分析,得到溃口垂向下切速率、横向展宽速率与溃口流量、溃口单宽流量之间的关系。结果表明:堤防溃口发展主要存在垂向冲刷、横向扩展2种形式;溃口发展速率与溃口流量呈正相关,但受入流流量影响,没有适用于所有工况的关系表达式;溃口发展速率与溃口单宽流量间的关系基本不受入流流量影响,下切和展宽速率与溃口单宽流量呈现指数关系;基于此关系,构建了以溃口单宽流量为参数的溃口发展过程计算模型,并对溃口垂向下切、横向展宽发展过程进行了模拟计算与对比分析,结果显示模拟情况与真实的溃口发展过程吻合较好,说明所提出的计算模型科学合理,且计算过程简洁。

分布式量子计算研究进展

量子比特的高效拓展是量子计算获取量子加速优势需要解决的基本问题,分布式量子计算(DQC)因其高度可行性和灵活性,成为解决量子比特拓展问题的关键技术之一。根据芯片间通信方式的不同,分布式量子计算可以分为基于量子隐形传态和基于量子线路拆分的分布式量子计算两种类型,前者主要面向容错量子计算,而后者被认为可在中等规模含噪声量子(NISQ)时代有效提升量子计算机算力。从长远角度来看,作为量子网络的主要应用之一,分布式量子计算可以更好地整合接入量子网络的海量量子计算机以解决高难度问题。首先介绍了分布式量子计算的来源和类型,在此基础上,给出了两类分布式量子计算的基本原理和发展状况,以及关注度较高的应用算法和编译优化方法。

新能源电力系统细粒度并行与多速率电磁暂态仿真

随着可再生能源的快速发展,电力系统设备类型越来越多,系统振荡特征越来越复杂,对电磁暂态仿真的精度和效率提出了更高要求。基于大规模集成电路设计中所使用的延迟插入法(LIM),提出了新能源电力系统的细粒度建模方法,并结合图形处理器(GPU)的资源优势,实现了算法的并行求解。所提方法将传统交流电网与电力电子设备进行解耦,并基于混合数值稳定性判据和局部截断误差的方法确定了各子系统的步长。然后,通过插值实现了新能源电力系统的多速率仿真。最后,基于GPU硬件平台,以含新能源接入的改进39节点系统为例验证了所提方法的精度,并以不同规模的新能源接入、不同仿真步长的组合验证了所提方法在仿真效率方面的优势。

基于Ncut分割和SVM分类器的医学图像分类算法

为解决医疗诊断中由于疲劳和主观因素影响导致的诊断错误,本文提出了基于Ncut分割方法的医学CT图像的分割、特征提取和诊断的新方案。将Ncut分割方法应用于脑CT图像。先进行图像分割,提取感兴趣区域,再从边缘、灰度,纹理三方面提取特征,最后利用支持向量机(SVM)对图像进行分类,为医生的诊断提供参考。从表格化的分类结果看,所提方案有较大的应用价值。

高温超导磁悬浮引纬结构悬浮稳定性分析

针对现有电磁投梭技术能量利用率低、引纬幅宽提升有限等问题,提出了一种基于超导磁悬浮的引纬方式,基于高温超导体的迈斯纳效应高温超导片梭能实现其自稳定悬浮,再通过设计的电磁线圈轨道产生行波磁场驱动片梭,从而实现增加片梭织机引纬幅度。由于引纬结构中永磁轨道间磁场存在相互干扰使轨道产生的磁场非对称分布,导致超导片梭两侧超导体悬浮力不相同,超导片梭不能稳定悬浮在轨道上方,后续引纬过程不能进行。为了保证引纬前片梭悬浮稳定性,通过有限元仿真软件分析超导片梭受到的悬浮力,并通过数值计算对永磁轨道磁场进行求解,从而研究磁场分布与超导片梭悬浮稳定性之间的影响。研究表明,轨道上方磁场分布对称性越高,超导片梭悬浮稳定性越高。通过数值计算方法确定了永磁轨道之间的距离为30-40 mm,即永磁轨道之间磁场发生干扰的临界距离,磁场分布具有很强对称性,超导片梭能够稳定悬浮于永磁轨道上方,并且能使超导片梭尺寸最小。

恶意模型下集合交集问题的保密计算

研究集合问题是安全多方问题的基础,当前已有的协议在处理集合问题时,不能保证集合运算的隐私性和正确性,且都是在全集范围下取值,导致应用范围受限,容易受到恶意敌手的攻击,安全性较低。因此,将集合是否存在交集问题转化为集合元素相减问题,并且基于高效的椭圆曲线加密方案,设计了一种半诚实模型下无全集限制求集合交集的保密计算协议。然后借助密码学工具设计了恶意模型下无全集限制求集合交集的保密计算协议。协议可以更好地抵御恶意攻击,且参与方无法通过观察结果推断出其他参与方的信息。这有助于提高整个协议的安全性。此外,该协议的计算复杂度和通信复杂度也低于其它现有同类型协议。

鱼肉切割技术的发展现状与展望

切割在鱼类产品初加工中占据着至关重要的地位。人工使用金属刀具由于效率低、精度不高、易滋生细菌等缺点,难以满足市场对鱼肉切割制品高精度、高质量的要求。因此,使用新型切割技术代替金属刀具,加入智能化控制代替一部分人力是必然趋势。综述了绿色新型切割技术中水刀和超声刀的研究进展及其在鱼肉和食品切割中的应用现状,横向对比了两种技术目前的优缺点以及适用场景和适用对象;概述了智能化技术在鱼肉切割中代替人工的可能性,如机器视觉代替人眼规划切割路径,质构和仿真技术代替人手调整切割工艺参数,多传感器数据融合代替人脑做出切割决策,并归纳了3种技术目前面临的挑战和优化方向;总结了新型切割技术和智能化系统的未来发展方向,通过技术的更新和升级,提高智能化技术的稳定性和鲁棒性,推动鱼肉切割的智能化和数字化发展。研究成果可为相关研究人员和企业提供参考,以促进新型切割方式在鱼肉产品加工行业中的发展,提高鱼肉切割的自动化和智能化水平,实现鱼类产品的高效、多样化、优质生产,以满足不断增长的市场需求。

基于LT码的分布式矩阵计算研究

在如今大数据和机器学习应用范围不断扩大的背景下,分布式计算系统成为处理庞大数据的必要工具。对于具有一定规模的计算集群,其性能会不可避免地受到系统噪声的影响,应考虑在分布式计算系统中借助编码技术来增强系统的鲁棒性。现有应用于分布式矩阵计算的编码方案多为固定速率编码,无法适应节点数量动态变化的实际情况。同时,由于部分任务有截止期限制,应在保证任务顺利完成的前提下尽可能地减少平均开销从而降低时延。针对上述问题,提出将LT码应用于雾计算场景下的分布式矩阵计算,设计Remo2算法。依托LT码的无速率特性自适应信道状态变化,通过合适的度分布函数设计以及双向切割、因子化度数的方法达到降低时延、增强分布式计算系统鲁棒性的预期效果。令k_(1)为A矩阵被切分后的子矩阵行值,k_(2)为B矩阵被切分后的子矩阵列值,实验结果表明,在k_(1)值固定的前置条件下,与FLT码及BDC-LT算法相比,Remo2算法的平均开销相对于前者稳定降低了33.3%,相对于后者减少了7.7%的冗余。此外,当k_(1)k_(2)大小的码长固定时,k_(1)、k_(2)的离散化程度越低,即limk_(1)-k_(2)→0,会带来更小的平均开销。