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61.
Kelson C. Lopes Flvia S. Pereira Regiane C. M. U. Araújo Mozart N. Ramos Roy E. Bruns 《Chemometrics and Intelligent Laboratory Systems》2004,70(2):157-163
Factorial design and principal component models are used to determine how ab initio H-bond stretching frequencies depend on characteristics of the molecular orbital wave functions of acetylene–HX, ethylene–HX and cyclopropane–HX π-type hydrogen complexes with X=F, Cl, CN, NC and CCH. The results obtained for the three sets of complexes show that factorial design and principal component analyses complement each other. Factorial design calculations clearly show that these frequencies are affected mostly by inclusion of electron correlation on the calculation level. On average, their values are increased by about 25 cm−1 due to a change from the Hartree–Fock (HF) to Möller–Plesset 2 (MP2) level. Valence, diffuse and polarization main effects as well as valence–diffuse, diffuse–correlation and polarization–correlation interaction effects are also important to better describe a factorial model to the H-bond stretching frequencies of these hydrogen complexes. This simplified model has been successful in reproducing the complete ab initio results, which correspond to two hundred and forty calculations. Principal component analyses applied only to hydrogen-bonded complexes whose experimental frequencies are known, has revealed that the six-dimensional original space can be accurately represented by a bidimensional space defined by two principal components. Its graphical representation reveals that the experimental intermolecular stretching frequencies are in closest agreement with the MP2/6–31+G and MP2/6–311+G ab initio results. 相似文献
62.
J. Gutirrez J. M. Barandiarn Z. Kaczkowski 《Materials Science and Engineering: A》2004,370(1-2):392-395
The change of magnetoelastic properties after thermal treatments has been investigated for two groups of metallic glasses. (Fe79Co21)75+xSi15−1.4xB10+0.4x (x (at.%)=0, 2, 4, 6, 8, 10) has been studied both in the as-prepared state and after thermal annealing in an applied magnetic field, to achieve a particular domain structure, at temperatures well below the crystallization temperatures. Changes in the ΔE effect, magnetomechanical coupling (k) and internal friction coefficient (Q−1) are reported, reaching values of about 60% of the saturation value ES. Fe64Ni10Nb3Cu1Si13B9 alloys annealed in vacuum for 1 h in the temperature range 350–550 °C showed maximum values of the ΔE effect and k of 61% and 0.85, respectively, accompanied by a minimum value of Q of around 2 for the sample annealed at 460 °C. These variations are related to the progress of nanocrystalization. The properties achieved are among the best reported for magnetomechanical applications. 相似文献
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油田注水系统的耗电量一般占整个油田生产耗电的40%-60%,因此降低注水系统的能耗可显著降低油田的生产成本。常规的通过调节阀门开启度来达到调节注水泵出口压力和流量的作法,会使很大一部分能量造成浪费,要解决这个问题,可以采取对注水泵进行调速的方法。文章论述了通过高压变频技术对注水泵进行调速,从而达到节能效果的基本原理;对一台恒速泵和一台变频调速泵并联运行时的效率进行了分析,并对应用实例进行了计算,注水站的效率比原来提高了9.04%,收到了显著的节能效果。 相似文献
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变速鱼雷推进器动态模型理论研究 总被引:1,自引:1,他引:0
传统鱼雷推进器静态模型已无法满足变速鱼雷的建模需要,为了解决这一问题,在国内外学者研究的基础上,运用流体动力学方法,建立了鱼雷推进器比较精确的动态模型。该模型是以推进器来流速度和螺旋桨转速为状态变量,以电机施加转矩为输入,螺旋桨推力和转矩为输出的。 相似文献
67.
O. A. Lambri J. I. Prez-Landazbal J. A. Cano V. Recarte 《Materials Science and Engineering: A》2004,370(1-2):459-463
Mechanical spectroscopy, neutron diffraction and differential scanning calorimetry (DSC) were performed on commercial Fe–6 wt.% Si alloy after quenching from high temperature. The damping spectrum shows a peak at around 800 K and an associated modulus defect. The modulus shows an increase during the second and subsequent heating runs. In addition, an anomaly in the modulus behavior has been found at around 400 K. Different thermal treatments allows to obtain two different recovery degrees of the quenched-in defects. The influence of the recovery degree on the 800 K internal friction peak and on the anelastic modulus has been evaluated and confirm the validity of the grain boundary mechanism associated to this peak. Experimental results are discussed on the basis of recovery and ordering processes. 相似文献
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使用2kW半导体激光在工具钢表面熔覆高速钢粉末。在同轴送粉的粉末汇聚点与激光的聚焦点可获得无裂纹的熔覆层。随着激光功率的增加,熔覆层厚度和粉末利用率增加,同时基体对熔覆层的稀释率下降。获得的熔覆层的硬度达到800Hv0.3,基体硬度200Hv0.3,表明大功率半导体激光在表面熔覆领域具有很好的应用前景。 相似文献