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梯形螺纹的加工经常采用的是车削加工,而对位于非回转中心的梯形螺纹加工就比较困难,需要改用四爪卡盘装夹或其他较复杂的装夹方法,然而对于较大型工件且螺纹需求位于边缘或者侧面的螺纹则无法采用车削加工,市场上很难买到梯形螺纹丝锥,特别是非标的梯形螺纹丝锥,常常需要定做,且成本很高。而采用铣削的方法便可以很容易的解决这类问题。本文全面叙述了内梯形螺纹的铣削方法。 相似文献
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随着时代的进步和技术的发展,自动化和智能化生产逐渐取代了传统加工。数控机床作为自动控制设备中的重要组成,在批量和复杂零件生产中的应用广泛。本文在归纳梯形螺纹主要加工方法的基础上,以典型梯形螺纹件的加工为例,提出数控车削梯形螺纹提高加工精度的工艺措施。 相似文献
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如何利用数控车床加工梯形螺纹,是近年来很多技术人员研究的对象.本文通过对梯形螺纹加工的工艺分析和加工方法的研讨,结合 SINUMERIK 802c 系统子程序嵌套技术的应用,探索出一套加工合格梯形螺纹的方法. 相似文献
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论述了目前在高钢级无缝管材、螺纹副及接头硬化处理、摩擦焊接工艺、非对称梯形螺纹及负角防脱扣螺纹优化设计、螺纹精密仿形梳刀加工等方面开展的研究工作,取得了重要进展。 相似文献
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韦筱斌 《中国高新技术企业评价》2011,(16):51-53
文章论述了一种可以解决变速车削梯形螺纹时产生乱牙问题的简单实用的数控车削加工方法,即车削螺纹时可以先用较高转速粗加工车削,再用低速来精车及修光,从而达到既提高了生产效率,又能很好地保证了螺纹的尺寸精度和表面粗糙度有效的数控车削梯形螺纹方法。 相似文献
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主要讲述技工学校梯形螺纹之车削方法直进法、左右切削法、车直槽法、车阶梯槽法等方法的缺点、难点,重点讲述了分层切削法的方法、步骤、图形演示等。 相似文献
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This paper proposes a novel procedure to estimate linear models when the number of instruments is large. At the heart of such models is the need to balance the trade off between attaining asymptotic efficiency, which requires more instruments, and minimizing bias, which is adversely affected by the addition of instruments. Two questions are of central concern: (1) What is the optimal number of instruments to use? (2) Should the instruments receive different weights? This paper contains the following contributions toward resolving these issues. First, I propose a kernel weighted generalized method of moments (GMM) estimator that uses a trapezoidal kernel. This kernel turns out to be attractive to select and weight the number of moments. Second, I derive the higher order mean squared error of the kernel weighted GMM estimator and show that the trapezoidal kernel generates a lower asymptotic variance than regular kernels. Finally, Monte Carlo simulations show that in finite samples the kernel weighted GMM estimator performs on par with other estimators that choose optimal instruments and improves upon a GMM estimator that uses all instruments. 相似文献
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从顾客需求不确定性出发,在考虑批量折扣的情况下,构建了一个基于成本、延迟交货数量、质量和交货提前期的具有模糊权重的多目标订单分配模型。在求解过程中,用隶属度函数表示决策者对各目标值的满意程度,用梯形模糊数来表示各指标的权重,然后将多目标规划问题转化为求全局满意度最优的单目标规划问题。最后通过一个数值算例说明了模型的求解过程。 相似文献
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巷道断面形状是影响围岩稳定性的关键因素。为研究断面形状对巷道稳定性的影响,对矩形、梯形和直墙圆拱形三种巷道断面形状进行了数值模拟研究,并分析了不同断面形状巷道围岩的应力特征、变形特征和塑性区域。结果表明:直墙圆拱形巷道围岩稳定性最好,梯形巷道次之,矩形巷道稳定性最差。 相似文献
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考虑到回收量的不确定性将影响回收网络的稳健性,建立了基于第三方企业的再制造逆向物流网络模糊规划模型,将废旧品的回收量和丢弃率用梯形模糊数表示,然后利用模糊机会约束规划方法将模型转化为清晰等价形式。通过示例数值仿真,表明了该模型的可行性,同时分析了不同置信水平下,最优选址策略和目标函数值的变化情况。 相似文献
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Multivariate continuous time models are now widely used in economics and finance. Empirical applications typically rely on some process of discretization so that the system may be estimated with discrete data. This paper introduces a framework for discretizing linear multivariate continuous time systems that includes the commonly used Euler and trapezoidal approximations as special cases and leads to a general class of estimators for the mean reversion matrix. Asymptotic distributions and bias formulae are obtained for estimates of the mean reversion parameter. Explicit expressions are given for the discretization bias and its relationship to estimation bias in both multivariate and in univariate settings. In the univariate context, we compare the performance of the two approximation methods relative to exact maximum likelihood (ML) in terms of bias and variance for the Vasicek process. The bias and the variance of the Euler method are found to be smaller than the trapezoidal method, which are in turn smaller than those of exact ML. Simulations suggest that when the mean reversion is slow, the approximation methods work better than ML, the bias formulae are accurate, and for scalar models the estimates obtained from the two approximate methods have smaller bias and variance than exact ML. For the square root process, the Euler method outperforms the Nowman method in terms of both bias and variance. Simulation evidence indicates that the Euler method has smaller bias and variance than exact ML, Nowman’s method and the Milstein method. 相似文献
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当前,河道综合治理断面形式主要有梯形、矩形、复合式这三种断面,护坡方式主要是混凝土、砌石、石笼、土工植生袋、草皮这五种护坡方式。论文以某河道治理工程项目为例,对比矩形断面重力式挡墙防洪堤与复合式断面宾格石笼+草皮护坡工程的应用。研究表明:采用复合式断面宾格石笼+草皮护坡更适合本工程,有利于降低工程造价、实现绿色生态、结构合理。采用瑞典条分法对其三种工况进行稳定性计算,表明设计中选定的防洪堤断面形式合理。 相似文献
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The main purpose of this paper is to propose a data mining algorithm for finding interesting association rules from given sets of fuzzy transaction data. To efficiently resolve the ambiguity frequently arising in available information and do more justice to the essential fuzziness in human judgment and preference, the trapezoidal fuzzy numbers are used to describe the fuzzy assessments of transaction data. Then, combining the concepts of fuzzy set theory and the priori algorithms, the interesting item sets are found to construct the association rules. Finally, a numerical example is used to demonstrate the computational process of proposed data mining algorithm. By utilizing this data mining algorithm, the decision-makers’ fuzzy assessments with various rating attitudes can be taken into account in the data mining process to assure more convincing and accurate knowledge discovery. 相似文献