一个考虑扩散的Holling-Tanner捕食-食饵模型研究

研究了一个在齐次Neumann边界条件下考虑扩散的Holling-Tanner捕食-食饵模型.首先,得到了系统的全局吸引子和持久性;然后,讨论了系统正常数平衡解的全局渐进稳定性;最后,研究了系统的Turning失稳性质.

曲轴车-车梳加工工艺分析及切削模拟实验研究

车-车梳工艺是现今汽车发动机曲轴主轴颈的粗、半精加工中广泛应用的切削工艺。以车-车梳工艺为研究对象,分析了车梳复合切削特性以及车-车梳加工工艺流程。并以一套自主改造的车-车梳数控机床和配套的刀具系统为实验平台,进行了车-车梳切削模拟实验,从轴颈圆度、表面粗糙度及轴颈侧壁表面粗糙度三个方面对加工质量进行了评估。实验数据及研究结果对国内曲轴加工工艺的改进和应用有一定的参考价值。

曲轴轴颈车-车梳刀具工作原理及结构设计

通过对汽车发动机曲轴轴颈车-车梳加工工艺的研究,以及对其刀具系统工作原理的分析,提出了车-车梳刀具系统的设计要求。以一套典型的车-车梳工艺过程为例,利用Solidworks三维建模软件,完成了对车-车梳刀具系统的结构设计与建模,并运用有限元分析软件验证了刀具系统的刚度和可靠性,实现了车-车梳刀具系统的完整设计。

曲轴车-车梳(拉)加工实验刀盘模块化设计原理及应用

通过对汽车发动机曲轴某一段主轴颈的加工工艺研究,以及对曲轴加工刀盘工作原理的分析,提出了刀盘结构的设计要求,并对刀盘单元切削模块进行了分类,实现了刀盘结构的模块化设计。针对车梳拉刀盘模块中的刀夹-刀盘组合进行尺寸链的优化设计,刀盘的尺寸公差值从原来的12μm放宽到25μm,制造的经济性和合理性得到了提高。根据曲轴加工工艺要求,完成了车-车梳(拉)实验刀盘驱动装置的设计和切削力校核。曲轴加工实验刀盘已成功应用于车-车梳(拉)切削实验。

曲轴车-车梳加工稳定性分析及实验研究

对车梳加工过程中引起颤振的原因进行了分析,并通过自主搭建的颤振测量系统实现了对车-车梳加工过程切削颤振的实时测量,研究了各工序切削过程的颤振规律及最大振幅。实验结果表明:开槽刀片切削过程颤振最明显,最大振幅为233.6μm;C刀和V刀切削过程颤振相对较小,最大振幅分别为132.4μm和130.4μm;梳刀切削过程颤振最小,最大振幅81.6μm,其加工稳定性可以满足曲轴制造的高精度要求。

Modeling and multi-response optimization of machining performance while turning hardened steel with self-propelled rotary tool

There are many advanced tooling approaches in metal cutting to enhance the cutting tool performance for machining hard-to-cut materials. The self propelled rotary tool （SPRT） is one of the novel approaches to improve the cutting tool performance by providing cutting edge in the form of a disk, which rotates about its principal axis and provides a rest period for the cutting edge to cool and allow engaging a fresh cutting edge with the work piece. This paper aimed to present the cutting performance of SPRT while turning hardened EN24 steel and optimize the machining conditions. Surface roughness （Ra） and metal removal rate （rMMR） are considered as machining perfor- mance parameters to evaluate, while the horizontal incli- nation angle of the SPRT, depth of cut, feed rate and spindle speed are considered as process variables. Initially, design of experiments （DOEs） is employed to minimize the number of experiments. For each set of chosen process variables, the machining experiments are conducted on computer numerical control （CNC） lathe to measure the machining responses. Then, the response surface method- ology （RSM） is used to establish quantitative relationships for the output responses in terms of the input variables. Analysis of variance （ANOVA） is used to check the adequacy of the model. The influence of input variables on the output responses is also determined. Consequently, these models are formulated as a multi-response optimi- zation problem to minimize the Ra and maximize the rMMR simultaneously. Non-dominated sorting genetic algorithm-II （NSGA-II） is used to derive the set of Pareto-optimal solutions. The optimal results obtained through the pro- posed methodology are also compared with the results of validation experimental runs and good correlation is found between them.

A Novel Tetraphenylethylene-Based“Turn On”Fluorescent Sensor with Highly Sensitive Response to Mercury Ions

A novel 4-tert-butyl-N’-(4-(1,2,2-triphenylvinyl)benzylidene)benzohydrazide(TBB)was successfully synthesized in simple one-step process.It was characterized by FT-IR,1H NMR,13C NMR and HRMS.Its fluorescence sensing ability to 15 metal ions was investigated.Weak emission from TBB could be efficiently increased by trace Hg^2+,through coordination reaction between TBB and Hg^2+ with"turn on"character.The fluorescence intensity of TBB/Hg^2+([TBB]=3.0×10^–6 mol/L,[Hg2+]=1.3×10^–4 mol/L)was 7.5 times higher than that of TBB.This TBB sensor exhibited high selectivity for Hg^2+ and other metal ions did not interfere in this determination.The limit of detection was 0.566μmol/L(S/N=3).The experimental results showed that this TBB sensor could sensitively respond to Hg^2+ within concentration range(from 5×10–6 mol/L to 1.3×10^–4 mol/L).

Epigenetic Enabled Normal Human Cells, Lead to <i>First Cell</i>’s Unique Division System, Driving Tumorigenesis Evolution

Normal cells must become cancer-enabling before anything else occurs, according to latest literature. The goal in this mini-review is to demonstrate special tetraploidy in the enabling process. This we have shown from genomic damage, DDR (DNA Damage Response) activity with skip of mitosis leading to diploid G2 cells at the G1 border in need of chromatin repair for continued cell cycling to the special tetraploid division system. In several studies specific methylation transferase genes were activated in normal human cells in tissue fields, containing different cell growth stages of the cancerous process. Histology studies, in addition to molecular chemistry for identification of oncogenic mutational change, were a welcome change (see below). In a study on melanoma origin, DDR also showed arrested diploid cells regaining cycling from methylation transferase activity with causation of 2n melanocytes transforming to 4n melanoblasts, giving rise to epigenetic tumorigenesis enabled First Cells. Such First Cells were from Barrett’s esophagus shown to have inherited the unique division system from 4n diplochromosomal cells, first described in mouse ascites cancer cells (below). We discovered that the large nucleus prior to chromosomal division turned 90° relative to the cytoskeleton axis, and divided genome reductive to diploid, First Cells, in a perpendicular orientation to the surrounding normal cells they had originated from. This unique division system was herein shown to occur at metastasis stage, implying activity throughout the cancerous evolution. Another study showed 4-chromatid tetraploidy in development to B-cell lymphoma, and that such cancer cells also proliferated with participation of this unusual division system. Such participation has long been known from Bloom’s inherited syndrome with repair chiasmas between the four chromatids, also an in vitro observation by us. Our cytogenetic approach also revealed that they believed mitotic division in cancer cells is wrong because such cell divisions were found to be from an adaptation between amitosis and mitosis, called amitotic-mitosis. Amitosis means division without centrosomes, which has long been known from oral cancer cells, in that MOTCs (microtubule organizing center) were lacking centrioles. This observation calls for re-introduction of karyotype and cell division studies in cancer cell proliferation. It has high probability of contributing novel approaches to cancer control from screening of drugs against the amitotic-mitotic division apparatus.

曲轴车-车拉与车-车梳加工工艺实验对比研究

本文以一套自主研制的车-车拉(梳)数控机床和配套刀具系统为实验平台,对车-车拉和车-车梳这两种曲轴的粗加工及半精加工工艺进行切削实验。基于何云、倪昊等学者对车拉和车梳切削机理的研究,确定了最后一步车拉和车梳主轴颈的切削参数,并在此基础上完善并确定了其他车削步骤的切削方案。完成实验后在圆度和表面粗糙度两个方面对两种工艺的加工质量进行评估分析。实验结果表明,在相同的设备条件和工件加工余量分布条件下,车-车拉加工工艺得到的曲轴主轴颈圆度公差值比车-车梳加工工艺大,而车-车拉加工工艺得到的曲轴主轴颈粗糙度值比车-车梳加工工艺小。研究结果对国内曲轴加工工艺的改进和应用有一定的参考价值。

曲轴车-车梳加工用硬质合金刀片切削性能实验研究

本文以硬质合金刀片为研究对象,设计了一套完整的车-车梳模拟切削工艺,在该工艺中确定了每一个工序的工件状态、对应使用的刀片型号及其走刀路线。经过一定的分析,确定了每种刀片所侧重的切削性能,以此为优化标准来安排切削实验。分别对R型刀片和C型刀片进行了断屑实验,通过收集切屑分析两种刀片的断屑效果;对V型刀片和梳型刀片进行了粗糙度实验,采用RA-200型号的电感式粗糙度仪进行粗糙度测量。实验切削参数的选择由企业推荐参数为中心向前后扩展。实验后以每种刀片所侧重的优化性能为参考选出了最佳的切削参数组合,各刀片对应的最优切削参数分别为:R型刀片Vc=120 m/min,f=0.35 mm/r;C型刀片Vc=180 m/min,f=0.35 mm/r;V型刀片Vc=180 m/min,f=0.3 mm/r;梳型刀片Vc=260 m/min,f=0.15 mm/r。

车梳复合切削特性试验研究

本文围绕车梳复合切削的轴向切削过程中的切削性能问题和切削效率问题,分别在相同的切削参数和材料去除率的条件下,对三种不同齿数车梳刀片的切削力和切削温度进行对比试验。探索了切削刃数目的变化对切削性能及切削效率的影响关系。切削试验包括梳切42CrMo的切削温度及切削力的测量。通过研究结果表明:不同齿数的车梳刀片在不同切削参数下切削温度和切削力有较大差异。在相同的切削参数条件下,多齿刀片的切削力与刀齿数量正相关,分配到每齿上的切削力值小于单刃切削时的数值。且三齿刀具与单齿刀具的切削力值相近;对切削温度而言,各刃口处测量值之间相差不大,单齿切削的切削温度比多齿刀片小。在相同材料去除率的条件下,单齿刀片的切削力数值较高,而三齿刀片和五齿刀片的该值相差不大,且单齿刀片加工后的表面粗糙度较其它两种刀片大。

硬质合金车梳加工中切削颤振的研究

车梳加工是现今汽车发动机曲轴主轴颈粗、半精加工时广泛应用的切削工艺。本文介绍了车梳加工的切削机理及其应用。通过车梳拉专用机床以及自行搭建的颤振实验平台来检测工件每时每刻的振动位置,以此来比较梳型刀片与普通车刀片的切削颤振情况和加工表面质量以及针对精加工的各切削参数对车梳加工切削颤振的影响。实验结果表明:在相同切削参数和切削余量下,梳型刀片的切削颤振大于C型刀片,加工表面粗糙度略低于C型刀片,切削效率则远远高于C型刀片;背吃刀量和进给速度增大时梳型刀片切削颤振增大,主轴转速增大时切削颤振减小。