A new analytical–experimental method for the identification of stability lobes in high-speed milling

Increased working speeds and accelerations of high-speed machining produce excitation of oscillations and cause dynamic problems. These problems affect the tool life (tool wear and tool failure), produce shoddy end surface, reduce productivity, produces scrap parts and affect the environment. A chatter’s analytical prediction method was combined with experimental multidegree-of-freedom systems modal analysis to achieve the objective of generating a new method to obtain the stability lobes information. This paper describes the development of this new method which obtains the stability information for some vibration modes that can be used to graph the stability lobes for high-speed milling, and these to help in the selection of parameters for chatter free operations. Some tests were carried out to demonstrate the quality of this method and the accomplishment of the proposed goals.     

Positive mood and executive function: Evidence from Stroop and fluency tasks.

Contrasting predictions have been made about the effects of positive mood states on the performance of frontal lobe tests that tap executive functions such as inhibition, switching, and strategy use. It has been argued that positive mood is likely to improve some cognitive processes, particularly those dependent on the frontal cortex and anterior cingulate of the brain. However, there is some evidence that happy mood may impair executive functioning. The current experiments investigated the effects of positive mood on Stroop and fluency tests, which are frequently used to assess executive function. Positive mood impaired performance on a switching condition of the Stroop test, but improved performance on a creative uses test of fluency. The effect of positive mood on an executive task may therefore depend on whether a task is inherently motivating or is impaired by diffuse semantic activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Midlife aging, open-ended planning, and laboratory measures of executive function.

The frontal lobes show early signs of structural and functional change in the course of adult aging. The 1st study of the current article examined whether midlife aging influences open-ended planning, a skill that is particularly sensitive to frontal lobe damage. There were no midlife declines in the ability to carry out variants of the T. Shallice and P. Burgess (1991) Six Elements and Multiple Errands Tests. Younger adults were more likely to break individual task rules. In a 2nd experiment, middle-aged adults performed worse than young adults did on laboratory executive tests sensitive to frontal lobe damage—Self-Ordered Pointing and the Wisconsin Card Sorting Test (N. M. Fristoe, T. A. Salthouse, & J. L. Woodard, 1997). In spite of changes in novel executive test performance, real-world executive skills appear to be spared in midlife aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CAE技术在某轿车碰撞研究中的应用

使用通用有限元前处理软件HyperMesh建立了国产某轿车的整车正面碰撞模型,在LS-DYNA中求解出碰撞全过程,通过分析碰撞结果研究该车防撞性能,为CAE技术在整车碰撞分析中的应用提供一些借鉴,具有一定的研究和指导意义。     

非闭合电极电容层析成像传感器在冻土测试中的应用

为了实现电容层析成像技术对冻土冻结冰峰面的在线、非侵入测试,研制出了满足冻土测试要求的非闭合电极电容层析成像传感器,并对该种传感器的电容分布特性进行了实测;确定出了适合冻土测试的的高、低介电常数的标定物质;搭建了冻土一维冻结实验系统.对含水量8%的湿土样冻结过程的冰峰面迁移进行了电容层析成像测试,并利用IMNSNOF图像重建算法重建出了冻结过程各时刻的冻结截面物质分布图像,由图像可确定出冻土中已冻土、未冻区以及冰峰面的位置.电容层析成像测试结果与温度测试结果相吻合.     

探索龙门山前缘物探采集技术

四川盆地龙门山前缘地区地震地质条件复杂,资料信噪比低,勘探前景良好。为加快该区勘探进程,西南分公司进行了川西龙门山前缘地震勘探采集技术攻关,初步形成了适合龙门山前缘地区的地震资料采集技术,在龙门山前缘地区的地震勘探中发挥了重要作用,并发现大园包大型构造圈闭,取得了较好的勘探效果。     

高动态条件下伪随机码捕获的旁瓣虚警分析

采用Matlab对扩频码的自相关旁瓣在载波频差条件下的改变情况进行了仿真,可以看出自相关旁瓣峰值和均值随载波频偏的变化发生了较为明显的改变,在0kHz-1kHz范围内变化最为明显,在1kHz～10kHz范围内变化幅度较小,成波浪起伏变化。同时自相关旁瓣的变化,导致系统捕获时的虚警概率也发生了相应变化,进而导致虚假捕获。而在采用白适应门限情况下,虚警概率大大降低,因此在实际情况中,基于高斯分布的固定门限不是最佳选择。     

水平井地质导向技术在冀东油田的应用

水平井地质导向是直接关系到水平井成功与否的关键技术。结合冀东油田地质特点，通过实例,系统介绍了油层着陆和水平段地质导向过程中的地层对比法、“LWD”导向法、井身轨迹跟踪图法等方法在冀东油田的应用情况，并对施工中遇到的问题进行了总结。     

Individual differences in executive functions are almost entirely genetic in origin.

Recent psychological and neuropsychological research suggests that executive functions--the cognitive control processes that regulate thought and action--are multifaceted and that different types of executive functions are correlated but separable. The present multivariate twin study of 3 executive functions (inhibiting dominant responses, updating working memory representations, and shifting between task sets), measured as latent variables, examined why people vary in these executive control abilities and why these abilities are correlated but separable from a behavioral genetic perspective. Results indicated that executive functions are correlated because they are influenced by a highly heritable (99%) common factor that goes beyond general intelligence or perceptual speed, and they are separable because of additional genetic influences unique to particular executive functions. This combination of general and specific genetic influences places executive functions among the most heritable psychological traits. These results highlight the potential of genetic approaches for uncovering the biological underpinnings of executive functions and suggest a need for examining multiple types of executive functions to distinguish different levels of genetic influences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Uncharted islands of chatter instability in milling

This paper provides conclusive evidence that isolated islands of chatter vibration can exist in milling processes. Investigations show these islands are induced by the tool helix angle and act to separate regions of period-doubling and quasi-periodic behavior. Modeling efforts develop an analytical force model with three piecewise continuous regions of cutting that describe helix angle tools. Theoretical results examine the asymptotic stability trends for several different radial immersions and helix angles. In addition, new results are shown through the implementation of a temporal finite element analysis approach for delay equations written in the form of a state space model. Predictions are validated by a series of experimental tests that confirm the isolated island phenomenon.