墨粉灌装车间噪声测试分析与控制

本文应用峰值频率声压级对比方法并结合相干分析技术对某墨粉灌装车间主噪声源进行了诊断，分析了声源特性，在此基础上提出了经济合理的治理措施，实施后取得了满意的结果，车间噪声达到了相应的国家标准。     

功率超声对Al-Si合金凝固过程中溶质偏析的抑制效应

研究了功率超声作用下，直径为10 mm Al-1%Si合金键合线水平连铸坯的微观组织形貌以及溶质元素在基体中的分布情况.实验结果表明：在功率超声作用下，铸坯的凝固组织得到了细化，Si元素在α(Al)基体中的固溶度及其分布的均匀性得到了提高，溶质偏析得到了抑制.从功率超声对Al-1%Si合金凝固过程中的溶质扩散，结晶温度间隔，液穴形态，温度场和流动场以及合金微观组织形貌的影响出发，尝试性地对功率超声抑制溶质元素微观偏析的机理进行探讨性的解释和说明. 关键词： 功率超声 水平连铸 Al-1%Si合金 溶质偏析     

Synthesis,Crystal Structure and Luminescent Mechanochromism of a Square-planar Pt(Ⅱ) Complex Based on 1,10-Phenanthroline Derivative

A new square-planar platinum(Ⅱ) complex, [Pt(Me3SiC≡Cphen)(C≡CC6H4Cl-3)2](1), was synthesized by using 3-trimethylsilylethynyl-1,10-phenanthroline(Me3SiC≡Cphen) and 3-chlorophenylacetylene ligands, and its structure was characterized by single-crystal X-ray crystallography. 1 crystallizes in triclinic, space group P1 with a = 6.9524(5), b = 12.7796(11), c = 17.5846(10) ?, α = 78.484(5), β = 88.700(5), γ = 75.600(6)°, V = 1482.23(19) ?3, Z = 2, C33H24Cl2N2 PtSi, Mr = 742.62, Dc = 1.664 g/cm3, F(000) = 724, μ(Mo Ka) = 4.979 mm-1, R = 0.0369 and wR = 0.0786. In 1, adjacent molecules along the a axis are stacked in a columnar structure through π···π interactions, and such neighboring columnar structures are connected with each other by C–H···π hydrogen bonds to form a 2D supramolecular network. 1 exhibits reversible luminescence mechanochromic property with the luminescence red shift in a range of ca. 146~182 nm. Extremely large red-shifts of luminescence spectra suggest that luminescent mechanochromic property of 1 is due to the formation of aggregate via Pt–Pt interaction during the mechanical grinding. Based on this property, a simple device was developed and used for rewritable data storage.     

切割那些事

正祝你生日快乐,祝你生日快乐,祝你生日快乐!吹蜡烛喽,噗!贝卡,是我生日哎,你一口气把蜡烛吹灭了,几个意思啊?乔乔,那个……我是太激动了,一不小心……这样吧,我来替你切蛋糕。你想切成几块呢?(夺过塑料刀)贝卡你辛苦了,切蛋糕就不用你代劳啦!数学制造出了各种奇异的数字模式,有意思的是,你可以通过几个大小一样的球,轻松地检验它们是否正确。如果你只是一个普通人,那么你可以使用橘子或弹珠;但如果你是一位无所不     

Tunable terahertz acoustic-phonon emission from monolayer molybdenum disulfide

The acoustic-phonon emission from monolayer molybdenum disulfide (ML-MoS₂) driven by a direct-current electric field is studied theoretically using the Boltzmann equation method. It is found that the Cerenkov emission of terahertz acoustic-phonons can be generated when a very weak electric field is applied to ML-MoS₂. The physical mechanisms of acoustic-phonon emission are analyzed from the perspective of condensed matter physics. The acoustic-phonon emission from ML-MoS₂ is also compared with those from graphene and GaAs. The results reveal that the frequencies of acoustic-phonons generated by ML-MoS₂ are between the frequencies of those generated from GaAs and graphene. The results of this work suggest that the ML-MoS₂ can make up for graphene and GaAs in respect of acoustic-phonon emission and be used in tunable hypersonic devices such as terahertz sound sources.     

碱式磷酸锌光学性质的理论计算及其实验验证

Zn₂(OH)PO₄ (ZPOH)属于正交晶系,其空间群为P2₁2₁2,该结构没有对称中心。基于赝势平面波方法,计算了ZPOH的电子结构,线性折射率和倍频(SHG)系数,并拟合了色散方程。为了验证计算值,使用水热法合成了ZPOH微晶,实验测得其SHG效应与理论计算相符,同时测试了ZPOH的紫外(UV)吸收边及其热稳定性。     

共焦点的椭圆与双曲线的一组性质及应用

从多角度对共焦点的椭圆和双曲线进行了研究,得到一组性质,并举例说明性质的应用.     

靶向性调控胫骨前肌对静态平衡的影响——基于经颅直流电刺激的干预

目的 采用随机、双盲交叉实验设计，探究经颅直流电刺激(transcranial direct current stimulation, tDCS)对胫骨前肌的靶向性调控是否可以诱导静态平衡表现的改善。方法 使用经颅磁刺激(transcranial magnetic stimulation, TMS)确定胫骨前的肌皮层热点靶区，24名在校大学生以随机的顺序接受两次刺激——20 min, 2 mA tDCS和假刺激(sham),每次刺激前后分别完成TMS测试和平衡能力测试，评估tDCS靶向性调控胫骨前肌对皮层兴奋性以及双足睁眼、双足闭眼、单足睁眼和单足闭眼静态平衡的影响。结果 (1)tDCS和Sham未呈现明显的组间差异；相比基线，tDCS刺激显著增大双足睁眼的平均速度，显著降低单足闭眼的动摇总轨迹长。(2)相比Sham, tDCS显著增大双足睁眼和单足闭眼Y方向平均中心变位。相比基线，tDCS显著降低双足睁眼Y方向平均中心变位、单足闭眼Y方向平均速度。(3)相比Sham, tDCS显著增加双足睁眼X方向平均中心变位、单足闭眼X方向平均中心变位和双足睁眼X方向最大动摇经。相比基线，tDCS...     

Determination of periodontal pathogens in human oral cavityEI北大核心CSCD

The simultaneous detection of Porphyromonas gingivalis （PG），Tannerela forsythia （TF），and Treponema dentinarum（TD）based on multiplex polymerase chain reaction（PCR）and capillary electrophoresis （CE），and the effect of sampling position were investigated. Results demonstrated that there was a linear relationship between migration time and DNA length when DNA fragments were separated by capillary electrophoresis，and the correlation coefficient was 0.9976. In 0.5% hydroxyethyl cellulose （HEC），the PCR products of these periodontal pathogens could be separated within 1.6 min. When sampling at different positions in the periodontal pocket，the PCR products were also different. When analyzing PCR products by capillary electrophoresis，the maximum relative deviation of the peak time was 7.4%. Based on fluorescence intensity，it could be inferred that the concentrations of PG，TD and TF in the gingival fluid were 5.13×10-11 ，7.89×10-11 and 4.87×10-11 ng/µμL，respectively. © 2023, Youke Publishing Co.,Ltd. All rights reserved.