扫描控制单元电子学线路

简要介绍了一种新的扫描控制单元电子学线路 ,它是为高电离态原子光谱学实验研究装置控制及数据获取电子学系统专门设计研制的 ,是该系统的关键电路之一。

Structural and PL properties of Cu-doped ZnO films

Cu-doped ZnO films with hexagonal wurtzite structure were deposited on silicon (1 1 1) substrates by radio frequency (RF) sputtering technique. An ultraviolet (UV) peak at similar to 380nm and a blue band centered at similar to 430nm were observed in the room temperature photoluminescent (PL) spectra. The UV emission peak was from the exciton transition. The blue emission band was assigned to the Zn interstitial (Zn-i) and Zn vacancy (V-Zn) level transition. A strong blue peak (similar to 435 nm) was observed in the PL spectra when the alpha(Cu) (the area ratio of Cu-chips to the Zn target) was 1.5% at 100 W, and ZnO films had c-axis preferred orientation and smaller lattice mismatch. The influence of alpha(Cu) and the sputtering power on the blue band was investigated.

Calorimetric study on two biphenyl liquid crystals

The molar heat capacities of the two biphenyl liquid crystals, 3BmFF and 3BmFFXF3, with a purity of 99.7 mol% have been precisely measured by a fully automated precision adiabatic calorimeter in the temperature range between T = 80 and 350 K. Nematic phase-liquid phase transitions were found between T = 297 K and 300 K with a peak temperature of T-peak = (298.071 +/- 0.089) K for 3BmFF, and between T = 316 and 319 K with a peak temperature of T-peak = (315.543 +/- 0.043) K for 3BmFFXF3. The molar enthalpy (Delta(trs)H(m)) and entropy (Delta(trs)S(m)) corresponding to these phase transitions have been determined by means of the analysis of the heat capacity curves, which are (15.261 +/- 0.023) U mol(-1) and (51.202 +/- 0.076) J K-1 mol(-1) for 3BmFF, (31.624 +/- 0.066) kJ mol(-1) and (100.249 +/- 0.212) J K-1 mol(-1) for 3BmFFXF3, respectively. The real melting points (TI) and the ideal melting points (TO) with no impurities of the two compounds have been obtained from the fractional melting method to be (298.056 +/- 0.018) K and (298.165 +/- 0.038) K for 3BmFF, (315.585 +/- 0.043) K and (315.661 +/- 0.044) K for 3BmFFXF3, respectively. In addition, the transitions of these two biphenyl liquid crystals from nematic phase to liquid phase have further been investigated by differential scanning calorimeter (DSC) technique; the repeatability and reliability for these phase transitions were verified. (C) 2004 Elsevier B.V. All rights reserved.

Thermodynamic study of ibuprofen by adiabatic calorimetry and thermal analysis

Molar heat capacities of ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 400 K. The polynomial functions of C-p,C-m (J K-1 mol(-1)) versus T were established on the heat capacity measurements by means of the least fitting square method. The functions are as follows: for solid ibuprofen, at the temperature range of 79.105 K less than or equal to T less than or equal to 333.297 K, C-p,C-m = 144.27 + 77.046X + 3.5171X(2) + 10.925X(3) + 11.224X(4), where X = (T - 206.201)/127.096; for liquid ibuprofen, at the temperature range of 353.406 K less than or equal to T less than or equal to 378.785 K, C-p,C-m = 325.79 + 8.9696X - 1.6073X(2) - 1.5145 X-3, where X = (T - 366.095)/12.690. A fusion transition at T = 348.02 K was found from the C-p-T curve. The molar enthalpy and entropy of the fusion transition were determined to be 26.65 kJ mol(-1) and 76.58 J mol(-1) K-1, respectively. The thermodynamic functions on the base of the reference temperature of 298.15 K, (H-T - H-298.15) and (S-T - S-298.15), were derived. Thermal characteristic of ibuprofen was studied by thermo-gravimetric analysis (TG-DTG) and differential scanning calorimeter (DSC). The temperature of fusion, the molar enthalpy and entropy of fusion obtained by DSC were well consistent with those obtained by adiabatic calorimeter. The evaporation process of ibuprofen was investigated further by TG and DTG, and the activation energy of the evaporation process was determined to be 80.3 +/- 1.4 kJ mol(-1). (C) 2003 Elsevier B.V. All rights reserved.

地下水埋深较大条件下井灌区土壤水分动态变化特征

针对 2 0世纪 80年代以来 ,北方井灌区农田地下水开采多 ,补给少 ,地下水位普遍下降的问题 ,通过分析在北京市东南郊水资源试验区连续 4年土壤水分观测资料 ,探讨了平原井灌区地下水埋深较大条件下 (超过 6m ) 0～ 3 m层土壤水分动态变化规律。按春灌期 ,雨季和秋末～春初三个阶段分析了土壤水分的季节性变化特点。分析表明 ,在土壤干旱时期 ,农田灌溉或降雨后 ,灌水和降雨 (小于 80 m m)主要补充于 0～ 1m土层 ;雨季 ,当表层土壤水分得到一定补充 ,又遇较大次降水 (10 0～ 15 0 m m )时 ,降雨主要被 1.0～ 2 .5 m层土壤所容纳 ,田面不会产生径流 ,同时地下水位回升幅度较大。研究认为 ,0～ 3 m层土壤对降水有很强的调蓄能力 ,雨季平均有 85 %的降水滞蓄其中。因此 ,在田间采取一定的拦蓄水措施 ,即使在遇到大暴雨 (15 0～ 2 0 0 m m )的情况下 ,也可以做到农田地表不产流或少产流、绝大部分降雨就地拦蓄入渗 ,增加土壤水资源量。