关于电压、电势和电势差概念的理解

文章讨论了稳定涡旋电场中导体上的电压,并把该情况及似稳条件下导体上的"电势""电势差"与静电场中的电势、电势差作了比较。结果表明:只存在静电场时,空间任一点有电势,两点间有电势差;存在涡旋电场时,在一定条件下(形成稳定电流和似稳电流时)在导体上任一点有"电势",只在由导体连接着的两点间有"电势差"。当电场为只由静止电荷激发的静电场,此时一点的电势值与零点的选择有关,电势差与积分路径无关;当电场为全部电场中的保守场部分时,一点的"电势"值与零点的选择有关,"电势差"也与积分路径无关。两点间电势差是单位正电荷从一点经任意路径移到另一点时外力克服静电力做功而增加的能量,即静电势能的增量;两点间"电势差"是单位正电荷从导体上任一点经导体中的任意路径移到另一点时获得的(净)能量,是外力所做的功除去发热剩余的能量,数值上恰等于静电势能的增量。     

含二茂铁基的取代缩氨基脲,取代缩氨基硫脲的合成和性质

缩氨基脲、缩氨基硫脲既是很好的金属离子配体,又有很好的生物活性,如抗细菌、病毒、抗结核、抗麻疯病、抗风湿、抗嗜眠等,文献曾有一些报道。其中有些在结构上调整,引入二茂铁基,显示了一些特殊性质。本文在此基础上进一步合成了12个新型结构的含二茂铁基的缩氨基脲(或硫脲),对它们的性质作了初步研究。     

含蒽醌基偶氮染料的合成及其吸收光谱的研究

高产率地合成了一系列1-氨基蒽醌与2-羟基-3-氨替酰氨萘酚(色酚)的偶氮染料, 对其进行了元素分析、红外光谱表征。研究了不同取代基对偶氮染料吸收光谱的影响, 考察了光照条件下该类偶氮染料在DMF稀溶液中吸收光谱的变化特征。     

Sol-gel derived oxides and mixed oxides catalysts with narrow mesoporous distribution

A novel sol-gel process for preparing oxides and mixed oxides sols from precipitation and peptization process is reported in this article. Inorganic salts are used as raw materials in this study. It is found that the amount of acid has great influence on the stability and particle diameter distribution of the precursor sols. Ultrasonic treatment is used to prepare alumina sol at room temperature. The result of 27AI NMR shows that there exist AI_13~(7+) species in the sol. By controlling the sol particles with narrow particle diameter distribution, alumina, titania and silica-alumina (SA) materials with narrow mesoporous distribution are formed by regular packing of sol particles during gelation without using any templates. The results also show that the structure and particle diameter distribution of precursor sol determine the final materials' texture.     

甲烷部分氧化制合成气NiO/γ-Al2O3催化剂的失活研究:溶胶-凝胶法对催化性能的影响

The nickel-based catalyst used in partial oxidation of methane(POM)to syngas emerged as the most practical one because of the high turnover rate and inexpensive cost.However,nickel-based catalyst supported on γ-Al2O3 is usually unstable at high temperature owing either to carbon deposition[1],the loss and sintering of nickel[2] or to phase transformation.     

牙本质龋的太赫兹成像研究

牙本质龋与牙髓感染状态及活力密切相关,龋损深度则决定临床治疗方案,但目前牙本质龋的检测及诊断方法如：视诊、探诊容易受到主观因素影响;X线辅助检查对龋病灵敏度低等,都有一定缺陷,可靠性及有效性仍有待提高。太赫兹时域光谱可以利用不同的物理参数成像,在牙本质龋在体、无损检测方面有较大应用潜力。为探索牙本质龋损的太赫兹光谱图像开展本研究。实验通过搭建透射、反射式扫描太赫兹平台,对15枚含牙本质龋离体牙磨片扫描,通过数据二维重构,获得了不同参数的太赫兹透射和反射图像,再将太赫兹图像与实验室研究龋病的光镜图像与X线图像对比、拟合并进行光镜下、太赫兹图像下龋损面积评价。结果表明：太赫兹图像与光镜图像相符,较X线图像灵敏度更高。反射模式下由于太赫兹反射信号较弱,使得样品厚度,表面粗糙程度以及系统噪声对实验结果影响较大,图像仅能辨识样本轮廓,不能用于区分牙釉质、牙本质及牙本质龋。透射模式下的频域1.4 THz相位差成像、时域信号最小值对应的时间成像都能区分牙釉质,牙本质和牙本质龋,可以用来鉴别三者,其中最小值对应的时间成像效果最佳。对光镜下测得牙本质龋损面积与太赫兹透射模式下的时域信号最小值对应的时间图...     

The synchronization of FitzHugh--Nagumo neuron network coupled by gap junction

It is well known that the strong coupling can synchronize a network of nonlinear oscillators. Synchronization provides the basis of the remarkable computational performance of the brain. In this paper the FitzHugh-Nagumo neuron network is constructed. The dependence of the synchronization on the coupling strength, the noise intensity and the size of the neuron network has been discussed. The results indicate that the coupling among neurons works to improve the synchronization, and noise increases the neuron random dynamics and the local fluctuations; the larger the size of network, the worse the synchronization. The dependence of the synchronization on the strength of the electric synapse coupling and chemical synapse coupling has also been discussed, which proves that electric synapse coupling can enhance the synchronization of the neuron network largely.     

含蒽醌基单偶氮染料吸收光谱研究

由1－氨基蒽醌与不同偶合基合成了8个含蒽醌基单偶氮杂料，对其进行了元素分析、红外光谱和紫外光谱表征。对其紫外吸收光谱的研究表明，当偶合基由2－羟基－3－氨替酰蔡酚变为2－羟基－11氢－苯并咔唑－3－氨替酰氨蔡酚时，偶氮染料在吸收红移130nm。用紫外灯光和红外灯光8个偶氮染料进行了光照实验，发现紫外光照会引起偶氮染料DMF衡溶液减色，没有观察到N＝N双键的顺反异构吸收变化。     

PEG还原Cu(Ⅱ)制备Cu2O纳米立方晶

Cuprous oxide (Cu₂O) nanocubes have successfully been prepared through a simple and novel method by heating Cu(ethyl acetoacetate)₂ (Cu(EAC)₂) and poly(ethyleneglycol) (PEG) in the absence of other chemicals. The PEG acted as the reducing agent as well as the stabilizer. The XRD results indicated that no metal Cu or CuO developed in the preparation process, and only Cu₂O nanoparticles with the cuprous structure were produced. The TEM images revealed that all the Cu₂O nanoparticles were cubic-shaped or square-shaped particles. The size and shape of Cu₂O nanocubes were dependent on concentrations of the Cu(Ⅱ) precursor, reactant temperatures, and chain length of PEGs. It is interesting that the reducing reactivity of PEG was sensitive to its chain length, and the reduction reaction activity was drastically dropped with the decreasing of polymer′s chain length.     

溶胶-凝胶法制备甲烷部分氧化制合成气用催化剂

用溶胶－凝胶法制备了一系列ＮｉＯ／γ－Ａｌ２Ｏ３催化剂，应用低温氮吸附，ＸＲＤ和ＴＰＲ等物理化学方法表征了这种新材料的结构和物化性能。结果表明，由于载体与活性组分间的强相互作用，使溶胶－凝胶法制备的催化剂具有粒度小，活性组分在载体表面均一高分散和热稳定性好等特点，同时，考察了该催化剂上甲烷部分氧化制合成气的反应性能，发现当Ｎｉ含量适当时，可获得高的反应活性和选择性。