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地下工程爆破对危岩稳定性的影响 总被引:1,自引:0,他引:1
根据爆破峰值速度衰减规律及危岩体主控结构面的假定,通过欧拉方程确定作用于危岩体峰值爆破荷载,并对峰值荷载进行修正得到时程爆破惯性力,建立了3类危岩体动力物理模型及计算模型,结合极限平衡方法得到3类危岩体动力稳定系数计算方法,选取最小的稳定性系数作为整个危岩体的动力稳定性系数,最终给出了3类危岩动力稳定性评价方法。以重庆市万州区太白危岩体为例,选取5个代表性危岩体进行动力稳定性计算,结果表明,3类危岩体动力稳定系数计算方法能较好地评价和反映危岩体的动力性态。 相似文献
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本文在无金标准情况下探讨皮肤毛孔标准照片制定的合理性和可行性,对医师诊断正确性进行评价。按照毛孔粗大程度制定分类为5水平的毛孔标准照片。对128名女性志愿者制作鼻翼毛孔照片,5位年资相近的皮肤科医师按照诊断标准和标准照片对128例自愿者照片进行独立的等级评分。诊断结果数据采用潜在分类变量模型(Latent Class Model,LCM)进行分析,分别拟合5位医师诊断条件概率一致的模型和诊断条件概率不一致的模型。计算医师诊断的条件概率和后验概率。潜变量分析结果提示诊断标准过于细化且分类模糊,依据条件概率将原始分类重新划分为3类的模型较好地拟合了诊断数据。运用客观和准确的能够真实反应和区分个体情况的诊断标准是诊断试验评价的基础和前提。潜在分类模型能够有效地处理无金标准的诊断重复性或一致性研究数据。 相似文献
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采用火焰原子吸收光谱法测定了煤矸石中Cu的含量.研究了实验预处理技术、消解体系的控制选择及仪器条件的优化,建立了相应的原子吸收光谱测定方法.方法的RSD在1%~3%之间,加标回收率达到96.5%~104%. 相似文献
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Classification noise is a common byproduct of traditional data mining approaches, and no specialized approach for detecting classification noise is currently available. Methods for outlier detection are well-developed, but outliers and classification noise have characteristics different enough to make outlier detection algorithms unsuitable for classification noise detection. In this paper, a new, specialized approach to detect classification noise is proposed, named relative density based classification noise detection (RDBCND). Computational experiments in artificial data sets described herein show that RDBCND has time complexity of O(n log n), indicating greater efficiency than traditional approaches, which exhibit time complexity of at least O(n2). The use of classification noise detection to improve the generalization ability of common classifier algorithms is also described. In particular, a new unified approach based on RDBCND is compared to a cross validation approach applied to a BP neural network. Trials in both artificial and real-life datasets show that the RDBCND-based approach can greatly accelerate the process of identifying the best decision function. The novel method can also eliminate underfitting, as the algorithm simply searches for the highest training accuracy. The experiments also show that the RDBCND-based method has greater accuracy and lower cpu time in reaching global solutions than the cross-validation method. Since the relative density is a local concept, our new approach can be directly used in nonlinear datasets without data transformation. It is a great advantage compared to some linear classifier algorithms. As in current linear classifiers, the kernel functions or other transformations need to be used to make them suitable for non-linear datasets, and that will increase their complexity. 相似文献
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提出了气相色谱法测定食品塑料包装材料中三甲基氯化锡含量的方法。样品经乙酸乙酯萃取,采用J&W DB-17毛细管色谱柱(30 m×0.25 mm,0.25μm)分离,用电子捕获检测器测定。三甲基氯化锡的质量浓度在0.334~26.76 mg·L-1范围内与其峰面积呈线性关系,检出限(3s)为0.000 6 mg·L-1。方法的回收率在77.6%~83.3%之间,测定结果的相对标准偏差(n=6)在2.5%~4.6%之间。 相似文献
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利用积分球绝对测量法,对在20 Pa真空缺氧、1 000 Pa空气,105 Pa空气及1 000 Pa氧气环境下,1 064 nm波长连续激光辐照30CrMnSiA碳钢材料过程中的反射光信号进行了测量,得到了30CrMnSiA碳钢在4种辐照环境下的反射率和温度变化曲线。结果表明:在空气组分辐照环境的低压到105 Pa范围内,材料初始反射率随压力增大而增大;在缺氧和富氧环境的激光辐照过程中,缺氧环境下材料反射率变化缓慢,且变化拐点温度高于富氧环境,富氧环境下材料被加热后的快速氧化反应有利于材料对激光能量的吸收;不同辐照环境(缺氧和富氧)相同材料温度条件下,材料反射率并不相同。 相似文献
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Using the technique of block-operators, in this note, we prove that if P and Q are idempotents and (P - Q)^2n+1 is in the trace class, then (P - Q)^2m+1 is also in the trace class and tr(P - Q)^2m+1 = dim(k(P) ∩ k(Q)^⊥) -dim(k(P)^⊥ N k(Q)), for all m ≥ n. Moreover, we prove that dim(k(P)∩ k(Q)^⊥) = dim(k(P)^⊥ ∩k(Q)) if and only if there exists a unitary U such that UP = QU and PU = UQ, where k(T) denotes the range of T. Keywords Fredholm, orthogonal projection, positive operator 相似文献