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Negative Thermal Expansion of GaFe(CN)_6 and Effect of Na Insertion by First-Principles Calculations
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We study the negative thermal expansion(NTE) properties and effect of Na insertion on the NTE of the framework material GaFe(CN)_6 by first-principles calculations based on density functional theory within the quasi-harmonic approximation. The calculated results show that the material exhibits NTE due to the low transverse vibrational modes of the CN groups. The modes demonstrate larger negative values of the mode Grüneisen parameters. Once Na is introduced in the framework of the material, it prefers to locate at the center of the quadrates of the framework material and binds to the four N anions nearby. As a consequence, the transverse vibrational mode of the CN group is clearly hindered and the NTE of the material is weakened. Our theoretical calculations have clarified the mechanisms of NTE and the effect of the guest Na on the NTE of the framework material. 相似文献
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针对现有空气源热泵冷热水机组高温环境运行效果差、效率低、排气温度过高导致停机等问题,设计一套基于准双级压缩循环理论,以R410A为制冷剂的中压补气型空气源热泵冷热水机组。在50℃极端环境温度下,采用中压补气技术,对系统的制冷性能进行实验研究。结果表明:(1)系统出水温度由10℃增至15℃时,制冷量增加77.28%,EER提高59.02%,系统的制冷量、功率和EER均随出水温度的升高而增加;(2)相较不补气模式,系统排气温度由111.9℃降至106.23℃,制冷量由14.14 kW增至16.05 kW,可有效降低排气温度,提升制冷量,能更好提高系统超高温制冷时的稳定性。 相似文献
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研究了均匀半空间上含有有限厚度的初应力磁电弹覆盖层结构中Love波的波动方程问题.基于初应力下磁电弹材料的运动方程,应力自由的表面条件和连续的界面条件,得到了电磁学开路和短路时Love波的波速方程.结果对新型磁电弹表面波器件的理论研究具有重要的意义. 相似文献
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The influences of nucleon coupling constants on the neutrino scatting and cooling properties of neutron stars are investigated. The results in the GM1, GPS250 and NL-SH parameter sets show that the magnitude of the neutrino emissivity and density ranges where the dUrca process of nucleons is allowed differ obviously between the three parameter sets in nucleon-only and hyperonic matter. Furthermore, the neutron stars in the GPS250 set cool very quickly, whereas those in the NL-SH set cool slowly. The cooling rate of the former can be almost three times more that of the latter. It can be concluded that the stiffer the equation of state, the slower the corresponding neutron stars cool. The hyperon Λ makes neutrino emissivity due to the direct Urca process of nucleons lower compared with nucleon-only matter, and postpones the dUrca process with muons. However, these Λ effects are relatively weaker in the GPS250 set than in the GM1 set. 相似文献
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苯丙酮尿症(PKU)是新生儿先天性苯丙氨酸羟化酶缺陷所引起的苯丙氨酸代谢障碍疾病.本研究采用超高效液相色谱-质谱联用技术, 测定了5例PKU新生儿出生3天和出生30天后的血斑与20例年龄相仿的正常新生儿血斑中辅酶Q10的绝对含量和辅酶Q9的相对含量,其中,健康新生儿血斑中辅酶Q10的含量为(122.1±24.9) ng/mL,PKU新生儿组的含量为(59.0±12.0) ng/mL.采用气相色谱-质谱联用技术测定了胆固醇和葡萄糖的相对含量.研究结果表明,与对照组相比,PKU新生儿血斑中辅酶Q10、Q9、胆固醇和葡萄糖的含量均显著降低,辅酶Q10的降低与血斑中苯丙氨酸含量升高呈现显著反向相关.本研究结果为PKU患儿的饮食治疗方案提供了依据. 相似文献
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针对国内外市场对近距离、大屏幕投影系统中需降低投影镜头加工难度及成本的要求,该文设计了一款超短焦投影镜头。设计过程中选用折反式结构,利用物、像关系原理,结合物方视场计算反射镜面型参数,得出反射镜面型。该方法便于校正大视场畸变、抵消折射镜组的像散和场曲,整个光学系统包括15片球面透镜和一片非球面反射镜,系统总长286 mm,投影距离500 mm,投射画面尺寸254 cm(100英寸),系统投射比0.22,相对照度大于85%,MTF(modulation transfer function)在0.4 lp/mm时大于0.5,水平TV畸变小于0.55%,垂直TV畸变小于0.65%。该系统的多项设计指标均优于市面上现有的产品指标,采用同轴球面设计易于加工、装调,可有效降低生产成本。 相似文献
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It has been shown that non-rotating black holes Recently study showed that thermal fluctuations would give in three or four dimensions possess a canonical entropy. rise to logarithmic corrections to Bekenstein Hawking entropy in area with a model-dependent uncertain coefficient. In this paper, the thermal fluctuations on Bekenstein-Hawking entropy in three-dimensional AdS black holes, Schwarzschild-de Sitter space and Kerr-de Sitter (KdS) spacetime with J = 0 will be considered based on a uniformly spaced area spectrum approach. Our conclusion shows that there is the same correction form in all cases we considered. 相似文献
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空间引力波探测任务采用的是外差法激光干涉测量技术,其对系统的噪声和精度要求极为苛刻。望远镜是引力波探测天文台的重要组成部分,起到激光信号收发的作用,其光学系统应具备大倍率、高像质、杂光抑制能力强,波前误差一致性好的特点。针对上述要求,对大倍率离轴四反无焦光学系统进行了设计和优化。基于初级像差理论阐述了初始结构的求解方法。系统具有中间像面和可用的实出瞳,便于杂光抑制和与后端科学干涉仪的承接。优化过程中,建立了波前一致性优化函数,通过优化设计,系统入瞳直径为200 mm,放大倍率为40倍,科学视场为±8μrad,波前误差RMS值优于0.005λ,PV值优于0.023λ(λ=1064 nm),波前一致性残差RMS值优于0.0008λ(λ=1064 nm),在捕获视场±200μrad内的成像质量均接近衍射极限,并对系统公差进行了分析,满足引力波探测的应用需求。 相似文献
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合成了两种稀土高氯酸盐与L-脯氨酸配合物的晶体.经热重、差热、化学分析及对比有关文献,知其组成 是[Pr2(L-Pro)6(H2O)4](ClO4)6和[Er2(L-PrO)6(H2O)4](ClO4)6,质量分数为99.24%和98.20%.选用RE(NO3)· 6H2O(RE=Pr,Er)、LPro、NaClO4·H2O和 NaNO3作辅助物,使用具有恒温环境的反应热量计,以 2 mol·L-1HCl 作溶剂,分别测定了[2RE(NO3)3·6H2O+6L-PrO+6NaClO4·H2O]和{ [RE2(L-PrO)6(H2O)4](ClO4)6+6NaNO3}在 298.15 K时的溶解热.设计一热化学循环求得化学反应的反应焓rH分别是:63.904 kJ·mol-1和 91.017 kJ·mol-1,经计算得配合物[RE2(L-Pro)6(H2O)4](ClO4)6(s)在 298.15 K时的标准生成焓(298.15 K)分别 是-6 594.78 kJ·mol-1和-6 532.87 kJ·mol-1。 相似文献