图wn*pk的优美性

提出图wn*pk的概念,并在n≡0(mod 2)且n≥4,k≡1(mod 2),k≡0(mod 2)和n≡1(mod 2)且n≥5,k≡1(mod 2),k≡0(mod 2)时,证明图wn*pk是优美的.     

对偶L_q变换法则

在已有结果的基础上对对偶L_q Brunn-Minkowski理论做了一些推广,主要讨论了对偶L_q Brunn-Minkowski型不等式并得到部分结果.给出统一的处理对偶L_q Brunn-Minkowski型不等式的方法,称此方法为对偶L_q变换法则,通过运用此法则给出了关于对偶混合体积著名的对偶L_q Brunn-Minkowski型不等式的简化证明.     

关于Diophantine方程Sx(n)=Sy(3)

摘要设Sm(n)是第m个n角数，给出当n-2为平方数时方程Sx(n)=Sy(3)的全部解的通式，并证明当n-2为非平方数时该方程有无穷多组正整数解．     

复$L_p$混合Petty投影不等式

通过支撑函数引入了复$L_p$混合投影体的概念. 在此基础上,建立了复$L_p$混合Petty投影不等式, 得到了复$L_p$混合投影体的单调性.     

氧化钽/氧化铝薄膜的阻变特性和突触特性

通过微电子加工工艺,制备出具有ITO/TaO_x/AlO_x/Ti结构的双介质层阻变存储器.器件中引入的氧化铝介质层有效地减小了器件的运行电流,降低了高/低阻态间切换所需的功耗,并增大了高/低阻态电阻比值.研究表明,器件的高低态电阻与其切换电压均有良好的稳定性和均匀性,且器件表现出可靠的擦写性能与保持性能.进一步研究表明,器件高阻态导电受肖特基发射机制主导,低阻态导电受空间电荷限制机制主导.器件还具有连续可调的电阻渐变行为,利用反复电脉冲刺激下的器件电阻变化来表征突触的权值,可以模拟突触行为.     

钙钛矿La0.7CexBa0.3-xMnO3的磁热性能研究

【目的】通过固相反应法制备La_(0.7)Ce_xBa_(0.3-x)MnO_3(x=0,0.05,0.10,0.15,0.20)的钙钛矿锰氧化物,研究Ce元素的不同掺杂量对原体系磁热性能的影响。通过Ce元素的掺杂,来调节原体系过高的居里温度以及改善体系的磁热性能。【方法】通过X射线粉末衍射的方式确定其单相结构,并使用振动样品磁强计对钙钛矿样品进行磁性能的测试。【结果】La0.7CexBa0.3-xMnO3(x=0,0.05,0.10,0.15,0.20)的居里温度分别为342.1K,319.8K,270.0K,244.3K和199.7K。在0~2T的外磁场下,该体系的最大磁熵变分别为2.54J/(kg·K),2.32J/(kg·K),2.51J/(kg·K),2.03J/(kg·K)和1.87J/(kg·K),且最大磁熵变都在居里温度附近。【结论】随着Ce元素掺杂量的增加,化合物居里温度逐渐降低;而最大磁熵变则呈先减小后增大又减小的趋势。同时由Arrott曲线判断这5个样品的相变都是二级相变。当Ce元素的掺杂量为0.05~0.10时,该体系的居里温度在室温附近,且最大磁熵变仍保持较大的值。     

若干Ramsey数Rn(3)和Rn(4)的下界估计

用构造性的方法研究了索数阶循环图的基本性质，得到若干Ｒａｍｓｅｙ数的下界。     

Extra Low NOx Emission Furnace with HTAC Technology

HTAC (High Temperature Air Combustion) technology needs high temperature air and low oxygen atmosphere to complete its unique combustion and achieve extra low NO_x production. In order to apply HTAC technology to forge furnace and meet the NO_x emission standard, exhaust gas regeneration technology in combination with no-fuel-switch and U-shape air circulation methods was applied on forge furnace. The results show that extra low NO_x emission (NO_x = 2.9 × 10-5, in volume fraction) could be obtained, the NO, emission meets the standards of Japan and US, HTAC mechanism is discussed finally.     

Influence of residual stress on the phase equilibrium of Ti(CxNy) thin films

In order to provide a theoretic basis for the research of Ti(C_xN_y) thin films, the thermodynamic database of Ti-C-N ternary system is established and the phase diagram sections are calculated. In addition to the assessed thermodynamic properties of Ti-C-N system, the influence of the residual strain energy of Ti(C_xN_y) thin films on the phase equilibria is analyzed. The classical formula for calculating the elastic strain energy is expressed into a Redlich-Kister form in order to perform the thermodynamic and equilibrium calculations using the Thermo-Calc software. Isothermal sections at 900 and 1100 K are calculated with this database and compared with those calculated without considering the residual stress. As a result, with the addition of strain energy δ-fcc Ti(C_xN_y) phase area shrinks. It is therefore concluded that with the influence of the residual stress in Ti(C_xN_y) thin solid film, the precipitation of pure δ film requires more precise control of composition.     

Correlation between Thermal Expansion and Magnetic Characteristics of Fe-Ni Alloys in Fe1-xNix/Cu Superlattices

Thermal expansion behaviors of FeNi alloys were investigated by means of X-ray diffraction technique within a Fe_1-xNi_x/Cu superiattice structure. It was found that with a Ni concentration of x = 0.35, FeNi alloy layers showed the well-known Invar behavior, but for alloy layers with either lower or higher Ni concentrations, thermal expansion coefficients were larger. Based on results of magnetic measurements it is concluded that FeNi alloy layers with Ni concentrations lower than the Invar composition are in a superparamagnetic state which leads not only to low spontaneous magnetizations but also to large thermal expansions of the alloy layers.     

An extrapolation theorem on martingale spaces with Ap weights

In this paper, we prove an extrapolation theorem of operators in martingale spaces with A _p weights, which shows that for operators T defined on martingale space L _u ¹ , if T is bounded on martingale space L ^p0(w) for some 1 < p ₀ < ∞ and every, w∈ A _∞, so it is on L ^p,s (w) for every 1 < p, s < ∞, and w ∈ A _∞. We also get some properties of A _p weights and prove that if w ∈ A ₁, then the maximal operator M is bounded on L ^p,q (w) with 1 < p < ∞, 1 < q ≤ ∞.     

Possibility of Reducing Formations of NOx and SO2 Simultaneously during Coal Combustion

Comparing with other NO_x and SO₂ control technologies, in-bed reducing NO_x and SO₂ simultaneously during coal combustion may lower the investment and operation cost. However, there are several possible contradictions between the reduction of NO_x and the capture of SO₂ during combustion: 1) CO rich atmosphere is favorable for the reduction of NO_x, whereas O_2 rich favorable for the capture of SO₂; 2) higher preheating temperature of coal is favorable for reducing NO_x, but unfavorable for reducing SO₂; 3) sulphation of some minerals may deactivate their catalytic effect on the reduction of NO_x. The attempts to eliminate such contradictions by coating coal granules with thin layer of monometallic oxides and mixed oxides were proposed. Ni₂O₃ and Fe₂O₃ showed high activity on NO_x reduction and CaO and Cr₂O₃ showed good effect on sulfur capture. The mixed metallic oxides, e.g., Fe₂O₃NiO, etc., showed effective for both NO_x reduction and SO₂ retention. It is possible to in-bed reduce NO_x and SO₂ simultaneously if the adhering materials are properly chosen to be difunctional materials of both active catalysts for NO_x reduction reactions and better sorbents for SO₂ retention.     

CuO/Ce_xZr_(1-x)O_2催化剂催化CO氧化性能的研究

采用共沉淀法制备Ce_xZr_(1-x)O_2载体,等体积浸渍法制备CuO/Ce_xZr_(1-x)O_2催化剂,考察载体中CeO_2与ZrO_2质量比(mCeO_2∶mZrO_2)和CuO负载量对CuO/Ce_xZr_(1-x)O_2催化剂结构及物化性能的影响.采用X射线衍射(XRD)、比表面积及孔容积测试(BET)、氢气程序升温还原(H_2-TPR)、一氧化碳程序升温还原(CO-TPR)等方法对CuO/Ce_xZr_(1-x)O_2催化剂进行表征,结果表明:当mCeO_2∶mZrO_2为4∶1时,CuO负载量为10%(质量分数)时,10%CuO/Ce_(0.815)Zr_(0.185)O_2催化剂具有较大的比表面积和孔容积,较好的Cu物质分散度,以及较好的还原性能和CO氧化性能.因此,在催化CO氧化反应中,10%CuO/Ce_(0.815)Zr_(0.185)O_2催化剂表现出较优的活性,在常压下,CO完全转化温度低至80℃.     

NOx Formation from Several Chinese Coals during Combustion in Packed Bed

The formation characteristics of NO_x during combustion of four typical Chinese coals have been studied in a packed bed combustor. The studies included the effects of chemical composition of coals and volatile matters, and combustion conditions, i.e. preheating temperatures of combustion gas, on conversion of NO_x during combustion. In term of the combustion experiments, there is a close relation between coal composition and conversions of NO_x. Coals with a higher nitrogen content give a lower F_NOx0, and coals with a higher volatile content give a lower F_NOx0. The further devolatilization experiments showed that volatile matters in the coal have an important effect on reducing conversion of coal-nitrogen to NO_x. It was interpreted as that the release of volatile matters during combustion caused a fuel-rich circumstance in the vicinity of coal particles which may restrain the formation of NO_x. Preheating temperatures of combustion gas has significant effects on conversions of NO_x and there exist a critical preheating temperature. At such temperature, lower F_NOx0 can be reached.     

模板法制备CexZr1-xO2及催化餐饮废油合成生物柴油

以松木为模板,使用模板法制备了不同铈锆含量的Ce_xZr_1-xO₂复合氧化物的催化剂,用于餐饮废油与甲醇进行酯交换反应合成生物柴油.采用BET、SEM对Ce_xZr_1-xO₂进行表征分析.研究不同制备方法、CeO₂的负载量和煅烧温度对催化剂活性的影响,以及不同的酯交换反应条件对生物柴油产率的影响.制备的Ce_xZr_1-xO₂具有松木的生物形态,并有助于催化剂形成多孔道结构.以Ce_xZr_1-xO₂为催化剂,考察甲醇和餐饮废油的酯交换反应.结果表明：当x=0.5,煅烧温度为600℃时,甲醇与餐饮废油物质的量比为60：1,催化剂用量（基于餐饮废油的质量）的质量分数为5%,反应温度为190℃,反应时间为6 h的反应条件下,酯交换反应的甲酯收率达到91.1%.     

纳米SnOx的水热合成及其储锂电化学性能

采用水热法在不同碱性条件下制备了不同形貌结构的SnO₂和SnO纳米材料，研究了两类锡基氧化物作为锂离子电池负极材料的储锂性能. 结果表明: SnCl₂·2H₂O直接水热水解或在碱性较弱时生成SnO₂，当碱性较强(pH>13)时则生成纳米SnO; 与SnO₂相比，SnO因其特殊的交叉网状花簇结构，表现出较高的首次充电、放电容量(1 059、1 590 mAh/g，库伦效率66.6%)、循环稳定性(循环500次，可逆容量达315 mAh/g)和倍率稳定性(在2.0 A/g下的可逆容量达到548 mAh/g). 碱性越强，SnO₂的循环稳定性和倍率稳定性越好，这归因于碱性越强生成的SnO₂颗粒越小，增大了电解液与电极材料的接触面积，缩短了Li+的传输距离，提高了循环稳定性和倍率稳定性. 研究结果为寻找长寿命、高容量负极材料的应用提供了参考.     

关于差分方程xn=(A+xn-1p)/(B+xn-kp)正解的有界性

证明差分方程x_n=(A x_(n-1)~p)/(B x_(n-k)~p),n=0,1,2,…,(其中k≥2,A,B,p∈(0, ∞))在p~(k-1)≥k~k/(k-1)~(k-1)时,有无界的解,并且当p~(k-1)相似文献   

铜纳米颗粒对氧化铪/氧化锌双介质层阻变特性的影响

通过微电子加工工艺制备了具有Ti/HfO_x:Cu NPs/ZnO/ITO结构的阻变存储器,研究铜纳米颗粒对器件阻变性能的影响. 研究表明,铜纳米颗粒不仅使器件操作电压减小、并且更加均一,而且增大了器件高低阻态的电阻值比（开关比）,高、低阻态电阻值更加稳定,表现出优异的耐擦写特性. 纳米颗粒的引入还使低阻态的导电由普尔-法兰克发射机制主导转变为欧姆导电细丝主导. 进一步研究发现,纳米颗粒增强了局部电场,不仅保证了较小电压下可产生更多的氧空位,还限定了导电细丝的位置. 此外,铜纳米颗粒有利于降低器件操作电压并提高其均一性,有助于提高阻态电阻值的稳定性.     

模板法制备La2O3-CexZr1-xO2催化酯交换反应的研究

以松木屑为模版,制备了La₂O₃-Ce_xZr_1-xO₂复合氧化物,用于催化餐饮废弃油合成生物柴油的酯交换反应。采用BET比表面积分析仪、扫描电子显微镜（SEM）对La₂O₃-Ce_xZr_1-xO₂进行表征。研究不同制备方法对催化剂活性的影响,分析不同的反应条件对酯交换反应产率的影响。结果表明：当反应条件为x=0.5,催化剂量为餐饮废油质量的5%,甲醇与餐饮废油物质的量的比为54：1时,在165℃下反应4.5 h左右,酯交换反应获得生物柴油的产率为91.1%。     

MnBi1-xCrx(x=0.04,0.08,0.12,0.16)合金的晶体结构与磁性能

本研究采用真空电弧熔炼法制备了MnBi_(1-x)Cr_x(x=0.04,0.08,0.12,0.16)系列合金,利用X射线衍射仪(XRD)、Rietveld全谱拟合和振动样品磁强计(VSM)研究和测定MnBi_(1-x)Cr_x系列合金样品的晶体结构和磁性能。结果发现,退火后的样品主相是低温相(LTP)MnBi(空间群:P6_3/mmc(194))。Rietveld全谱拟合分析确定每个样品中各相的含量并解析出主相MnBi_(1-x)Cr_x的晶体结构。M(M=Bi,Cr)原子之间的原子间距d_(M-M)随着掺杂量增大而增大。M原子与Mn原子的间距d_(M-Mn)随着掺杂量增大而减小。在400K时趋于饱和,且在掺杂量小于x=0.12时,饱和磁化强度随着掺杂量的增加而增大,在掺杂量大于x=0.12时,饱和磁化强度已经达到饱和,为20.55emμ/g,且不随掺杂含量的变化而变化。随着Cr含量的增加,矫顽力亦逐渐增加,并且在掺杂量为x=0.12时达到最大值。随着测试温度的上升,合金矫顽力均呈上升趋势。MnBi_(1-x)Cr_x(x=0.04,0.08,0.12,0.16)的德拜温度分别为378.46K,369.52K,354.62K和351.64K。