320排CT低碘浓度联合低管电压在冠脉成像中的应用研究

目的探讨320排螺旋CT低管电压技术联合低碘浓度在冠状动脉成像中的可行性.方法将40例疑似冠心病患者随机分为两组,使用东芝320排螺旋CT进行冠状动脉扫描,分别对两组图像质量进行主观和客观评分,对比有效辐射剂量及碘摄取量.结果 A,B两组的有效辐射剂量及碘摄入量比较差异具有统计学意义(P0.05),B组患者有效辐射剂量低于A组,且有效辐射剂量较A组降低72.95%,B组患者有效碘摄入量较A组减少18.29%,两组图像噪声值、左冠脉开口处强化CT值差异具有统计学意义(P0.05),B组图像噪声高于A组,两组图像质量主观评分比较差异无统计学意义(P0.05).结论 320排螺旋CT冠状动脉成像采用"双低"扫描方案能降低有效辐射剂量和碘摄入量.     

政府在高职教育校企合作中的功能定位和作为

在公共服务型政府的职能框架下,分析校企合作困境中的政府因素,研究得出政府在高职院校校企合作中应担负起健全机制、建立法规、加强管理的职能,并对校企合作过程进行组织协调、扶持保障、责任监督和对校企合作成果进行评价激励的结论,为校企合作中政府的功能定位和作为提供参考。     

同伦近似对称法：六阶Boussinesq方程的同伦级数解

提出了用以处理非线性问题的同伦近似对称法,并利用该方法研究流体动力学中的六阶Boussinesq方程.各阶相似约化解和各阶相似约化方程均可以写出通式,从而导出相应的同伦级数解.零阶相似约化方程等价于Painlevé IV型方程或Weierstrass椭圆方程,高阶相似解可以通过解线性变系数常微分方程得到.辅助参数具有调节同伦级数解的收敛性的作用.由近似对称法得到的级数解和各阶相似约化方程均能够由同伦近似对称法重新得到.     

环境稳定性与市场效率

投资者的预期及偏好乃资本市场行为的微观基础,由此演示在环境不稳定或不确定等条件下市场本身无法克服自我强化过程的出现,从而出现价格泡沫及过度振荡等低效率行为,降低市场效率,这说明资本市场乃典型的复杂系统,其效率应体现其适应环境变化、纠正价格扭曲的能力,进而使有效市场假设成为稳定环境下市场适应性的特例,另外,对影响市场效率的因素和政府的积极作用作了简要的探讨。     

Muscarinic acetylcholine receptor is involved in acetylcholine regulating stomatal movement

In animal cells, action of acetylcholine depends on its binding with its two specific receptors on the plasma membrane: the nicotinic and muscarinic respectively. The present investigation has shown that agonists of muscarinic receptor (muscarine) could induce stomatal opening, while the antagonists (atropine) could block stomatal opening induced by acetylcholine. Their effects can only be realized in medium containing Ca²⁺, but not in medium containing K⁺. The results tend to reveal that the muscarinic receptor is involved in acetylcholine-induced stomatal movement.     

State transfer control of quantum systems on the Bloch sphere

The state transfer under control fields is analyzed based on the Bloch sphere representation of a single qubit. In order to achieve the target from an arbitrary initial state to a target state, the conditions that parameters should satisfy are deduced separately in two different requirements: One is in the case of the rotation angle around the x-axis being fixed and another is in the situation with a given evolution time. Several typical states trajectories are demonstrated by numerical simulations on the Bloch sphere. The relations between parameters and the trajectories are analyzed.     

Method of adaptive PLL bandwidth adjustment without phase slipping

In a system based on the phase lock loop（PLL）, a trade-off must be made between the tracking precision and the dynamic performance if constant parameters are adopted. To overcome this drawback, a new method called no phase slipping adaptive bandwidth（NPS-AB） is proposed, which can adjust the loop bandwidth adaptively for different working conditions. As a result, both the tracking precision and the dynamic performance can be achieved concurrently. NPS-AB has two features to keep the loop stable： one is the capability of quick response to dynamics; the other is a series of additional constraints when the bandwidth is switched. Compared with other methods, there is no phase slipping during the adjustment process for NPS-AB. The phase integer ambiguity can be avoided and the phase value is kept valid. It is meaningful for carrier ranging systems. Simulation results show that NPS-AB can deal with sudden dynamics and keep the pseudo-range value stable in the entire dynamic process.     

Design of control sequence of pulses for the population transfer of high dimensional spin 1/2 quantum systems

On the basis of the relationship between the Hamiltonian of spin 1/2 quantum system under control and the energy level structure and transitions, a radio frequency pulse sequence is designed using intuitive and half counter-intuitive sequences of pulse to transfer the population of the 3-qubit system coherently. The effectiveness of the designed control sequence is verified through the system simulation experiment of the evolution of state. In principle, the design method of the control pulse sequence proposed can be generalized to use in the quantum systems of higher dimension.     

C3N4/ZnO复合材料可见光下的甲醛光电气敏性能

以水热法合成的ZnO纳米棒花为载体,将C_3N_4定量负载在其表面,制备C_3N_4/ZnO复合材料.由于C_3N_4与ZnO的能级匹配,可有效促进其光生电荷的分离,降低光生电荷复合率,显著提高载流子浓度,使其光电流明显增加.C_3N_4与ZnO质量比为2%的样品(2%C_3N_4/ZnO)性能最佳,其光电流在370 nm处可达120μA,为纯ZnO的2.4倍.在室温可见光下,2%C_3N_4/ZnO样品对HCHO的光电气敏响应值可达122%,比纯ZnO高4倍左右.结果表明,适量C_3N_4的负载有效延长了光生电荷的寿命,使ZnO材料在可见光区对HCHO气体表现出高效的光电气敏性能.     

模糊分级聚类分析与广州产业结构研究

为了对广州市产业结构进行层次分级，以确定相应的产业发展政策，本文采用模糊分级聚类分析方法，依据经济等八项评价指标，采用专家咨询法构筑基础矩阵，从１９个行业中，聚类出了优先发展行业，主导产业及一般类产业三个层次，从而为广州市制订２０年基本实现现代化的发展战略提供了科学决策依据，我们的结论是，电力能源业必须先行发展，同时继续发挥油加工业等行业的主导优势等。