Magnetic Resonance Imaging Segmentation via Weighted Level Set Model Based on Local Kernel Metric and Spatial Constraint

Magnetic resonance imaging (MRI) segmentation is a fundamental and significant task since it can guide subsequent clinic diagnosis and treatment. However, images are often corrupted by defects such as low-contrast, noise, intensity inhomogeneity, and so on. Therefore, a weighted level set model (WLSM) is proposed in this study to segment inhomogeneous intensity MRI destroyed by noise and weak boundaries. First, in order to segment the intertwined regions of brain tissue accurately, a weighted neighborhood information measure scheme based on local multi information and kernel function is designed. Then, the membership function of fuzzy c-means clustering is used as the spatial constraint of level set model to overcome the sensitivity of level set to initialization, and the evolution of level set function can be adaptively changed according to different tissue information. Finally, the distance regularization term in level set function is replaced by a double potential function to ensure the stability of the energy function in the evolution process. Both real and synthetic MRI images can show the effectiveness and performance of WLSM. In addition, compared with several state-of-the-art models, segmentation accuracy and Jaccard similarity coefficient obtained by WLSM are increased by 0.0586, 0.0362 and 0.1087, 0.0703, respectively.     

The effect of predator competition on positive solutions for a predator–prey model with diffusion

A diffusive predator–prey model with predator competition is considered under Dirichlet boundary conditions. Some existence and non-existence results are firstly obtained. Then by investigating the bifurcation of positive solutions, the multiplicity of positive solutions is established for suitably large m$m$. Furthermore, by meticulously analyzing the asymptotic behaviors of positive solutions when k$k$ goes to ∞$\infty$, we find that there is at most a positive solution for any c∈R$c\in R$ when k$k$ is sufficiently large. At last, some numerical simulations are presented to supplement the analytic results in one dimension.     

The synthesis and photolysis mechanisms of 8‐nitroquinoline‐based photolabile caging groups for carboxylic acid

Photolabile protecting groups have been extensively studied and applied for protection of small biological molecules, which make it convenient to detect the biological processes of the caged compounds. In this study, a series of 8‐nitroquinoline‐based photolabile caging groups for carboxylic acid were synthesized with improved photolysis efficiency. Among them, 6‐bromo‐8‐nitro‐1, 2‐dihydroquinolinyl chromophore was proven the best derivative on account of its longest absorption wavelength (345 nm), highest caging ability, and quantum yield (Φ = 0.003). Moreover, density functional theory calculations were performed in order to study the photolysis mechanisms. Theoretical calculations revealed that the reaction was kinetically inert under general mild condition with the high barrier height of 34.3 kcal/mol at carbonyl migration step, while under the photolysis condition, because of the large energy gap (64.5 kcal/mol) between S₀ and S₁ states, the reaction should be accessible in the triplet ground state (T₁) through successive excitation of S₀ → S₁ states, subsequent intersystem crossing of S₁ → T₁ states, and finally returned to the stable S₀ state for product via potential energy surface crossing between T₁ and S₀ states. Copyright © 2014 John Wiley & Sons, Ltd.     

灰色预测模型在汇率分析中的应用

首先建立IM（1,1）预测模型,在此基础上再使用马尔科夫预测方法,构造出一种全新的预测方法,应用于汇率的预测与控制中。     

单开关调制的PFN型层叠Blumlein线发生器

采用平板线加载的陶瓷电容型脉冲形成网络（PFN）构成了单开关调制的层叠Blumlein线发生器。采用传输线理论对短路寄生传输线的短路特性进行了理论分析,结果表明,短路寄生传输线的阻抗可以等效为耦合电感在主传输线的放电频率下产生的感抗。Pspice软件模拟表明,层叠线Blumlein线的电压叠加效率随耦合电感增加而增加。提出了一种磁环增感方法,在4级层叠Blumlein线上实现了3.1倍的脉冲电压叠加。     

Effects of Quantum Noise on Quantum Clock Synchronization

In laboratory environment, the channel apparatus will generate particular dominant quantum noise. The noise then will give rise to some errors during synchronization. In this work, the accuracies of one qubit transport protocol and entangled states transport protocol in the presence of noise have been studied. With the help of three important and familiar noise models, the quantum noise will degrade the accuracy has been proved. Due to the influence of quantum noise, the accuracy of entangled qubits decrease faster than that of one qubit. The entangled states will improve the accuracy in noise-free channel, and will degrade the accuracy in noise channel.     

300GHz超导SIS接收机系统的设计与构建

超导SIS(Superconductor-Insulator-Superconductor)混频技术是新兴的低噪声检测技术.其卓越的低噪声性能已使其成为毫米波和亚毫米波频段灵敏度最高的谱线接收设备,接收机的自动控制和稳定性有更高的要求,研制能够长期稳定工作的接收机有很重要的意义.本文主要讨论了我们自行研究设计工作在4K温度,准光学系统的毫米波超导SIS接收机的组成部件,根据我们制备的超导SIS隧道结器件的特性指标,计算设计了300GHz波段的超导接收机天线和结的集成芯片.     

Geometric Phase in a Time-Dependent A-Type Jaynes-Cummings Model

By using the Lewis-Riesenfeld invariant theory, we have studied the dynamical and the geometric phases in a generalized time-dependent A-type Jaynes Cummings model. We lind that, compared with the dynamical phases, the geometric phases in a cycle case are independent of the frequency of the photon field, the coupling coefficient between photons and atoms, and the atom transition frequency. It is pointed out that the geometric phases in a cycle ease can be measured under the case of a stronger time-dependent photon field and a stronger coupling photon-atom system. On the other hand, the geometric phases of the model may be measured in the composition of cold atoms.     

Bernstein Polynomial Estimation in the Partially Linear Model under Monotonicity Constraints

In this paper, a Bernstein-polynomial-based likelihood method is proposed for the partially linear model under monotonicity constraints. Monotone Bernstein polynomials are employed to approximate the monotone nonparametric function in the model. The estimator of the regression parameter is shown to be asymptotically normal and efficient, and the rate of convergence of the estimator of the nonparametric component is established, which could be the optimal under the smooth assumptions. A simulation study and a real data analysis are conducted to evaluate the finite sample performance of the proposed method.     

毛细管离子色谱法测定爆炸残留物中的无机阴离子

建立了爆炸残留物中无机阴离子的毛细管离子色谱检测方法.分离柱为Dionex IonPac AS19Capillary柱,通过考察阴离子保留情况,选择以10μL·min-1流速的KOH梯度洗脱,进样量为0.4μL,对爆炸残留物中常见无机阴离子进行了分析.在上述条件下,Cl-,NO2-,ClO3-,NO3-,SO24-,SCN-,ClO4-能很好地分离,并在质量浓度为0.01～5.00μg·mL-1时与对应色谱峰面积之间的线性关系良好,检出限分别为0.36、0.46、1.25、0.92、1.06、1.61、2.65ng·mL-1,回收率为95.84%～102.40%.该方法简便、快速、准确,可用于实际样品的测定.