Analysis of spectral properties of acoustic noise produced during magnetic resonance imaging

Magnetic resonance imaging (MRI) technique enables non-invasive analysis of the human vocal tract during phonation. Creation of MR images of the vocal tract is accompanied by simultaneous recording of the produced speech. The paper analyzes and compares spectral properties of an acoustical noise produced by mechanical vibration of the gradient coils during scanning in the open-air MRI equipment working in a weak magnetic field with low B₀ up to 0.2 T. This noise exhibits harmonic character, so it is suitable to analyze its properties in the spectral domain. Obtained results of spectral analysis will be used to devise a new cepstral-based filtering method for noise suppression of recorded speech.     

点缺陷对硼掺杂直拉硅单晶p/p~+外延片中铜沉淀的影响

系统研究了点缺陷对晶体硅中氧沉淀生成的影响,及点缺陷和氧沉淀对重掺硼直拉硅单晶p/p⁺外延片中铜沉淀的影响.样品先在不同的气氛下进行1250℃/60 s快速热处理,随后在750℃/8 h+1050℃/16 h常规热处理过程中引入铜沾污.通过腐蚀结合光学显微镜研究发现,以O₂作为保护气氛时,p⁺衬底中的沉淀密度较小,以Ar和N₂作为保护气氛时,重掺硼p⁺衬底中生成了高密度的沉淀,且在上述所有样品的外延层中均无缺陷生成.研究认为,以O₂作为保护气时引入的自间隙硅原子（Si_I）可以抑制沉淀的形成,而以Ar和N₂作为保护气氛时引入的空位则会促进沉淀的生成,这是导致此差异的主要原因.另外,研究还发现,p/p⁺外延结构能很好地吸除硅片中的铜杂质,从而保持了外延层的洁净.     

Controlled decoherence of three-level rf-SQUID qubit with asymmetric potential

A scheme is proposed to controll the decoherence of three-level rf-SQUID qubit with asymmetric potential by designing an external electric circuit for superconductive flux qubit. The results show that it may not only raise the gate speed but also extend decoherence time for a three-level structure.     

Approximate solution for the Klein Gordon-Schrdinger equation by the homotopy analysis method

The Homotopy analysis method is applied to obtain the approximate solution of the Klein--Gordon--Schr?dinger equation. The Homotopy analysis solutions of the Klein--Gordon--Schr?dinger equation contain an auxiliary parameter which provides a convenient way to control the convergence region and rate of the series solutions. Through errors analysis and numerical simulation, we can see the approximate solution is very close to the exact solution.     

加速器电水锤数值模拟与实验研究

强流加速器水介质形成线放电或击穿形成的冲击波对陶瓷真空界面具有破坏作用。为获得该冲击载荷的信息,应用通用软件ANSYS/LS-DYNA建立了一种水下爆炸有限元模型,将电弧放电等效为爆炸源,模拟得到了冲击波传播时序、压力历史曲线及陶瓷板的加速度响应;为验证模型的有效性,应用"针-板"电极水开关在输出电脉冲40～50 ns、幅值100～300 kV可调的10级陡化前沿Marx发生器上开展了电水锤缩比实验研究。实测了不同击穿电压下冲击波峰压、波速和主脉冲宽度,并依据经验公式计算了放电沉积能量和冲击波能量,平均约17%的间隙放电能量转换为冲击波机械能。对冲击波能量与峰压关系进行了拟合,并与数值模拟结果进行了比较,二者变化趋势基本一致,量级上吻合较好。     

大学校园户外学习空间的声舒适性研究——以5栋山西高校图书馆的室外空间为例

影响图书馆室外空间声舒适度评价的因素较多,本文采用声漫步、问卷调查和建筑物理参数测量的方法,对山西省三所高校共五所校区的图书馆室外空间的声环境进行了调研。结果表明,声源类型对主观声舒适度评价有较大影响,还会影响到声压级和主观声舒适度的关系。景观评价和主观声舒适度评价之间有正相关关系,人们对安静的声环境有较高的偏好,而对于有舒适背景声的声环境,喜好性的选择则表现的较为多样化。本文还分析了建筑物理环境舒适度整体评价与各项物理量主观评价之间的关系,这些物理量是影响舒适度整体评价的主因子,但还有其它因素会对整体评价产生影响。     

Annihilation-Derivative,Creation-Derivative and Representation of Quantum Martingales

On the basis of the quantum white noise theory we introduce the notion of creation- and annihilation-derivatives of Fock space operators and study the differentiability of white noise operators. We define the Hitsuda–Skorohod quantum stochastic integrals by the adjoint actions of quantum stochastic gradients and show explicit formulas for their creation- and annihilation-derivatives. As an application, we derive direct formulas for the integrands in the quantum stochastic integral representation of a regular quantum martingale. Work supported by the Korea–Japan Basic Scientific Cooperation Program “Noncommutative Stochastic Analysis and Its Applications to Network Science.”     

Study of top and bottom contact resistance in one organic field-effect transistor

This paper reports that the organic field-effect transistors with hybrid contact geometry were fabricated, in which the top electrodes and the bottom electrodes were combined in parallel resistances within one transistor. With the facility of the novel structure, the difference of contact resistance between the top contact geometry and the bottom contact geometry was studied. The hybrid contact devices showed similar characteristics with the top contact configuration devices, which provide helpful evidence on the lower contact resistance of the top contact configuration device. The origin of the different contact resistance between the top contact device and the bottom contact device was discussed.     

Anilinolysis of O‐butyl phenyl phosphonochloridothioate in acetonitrile: Synthesis,characterization, kinetic study,and reaction mechanism

This paper describes a simple optimized method for the synthesis of O‐butyl phenyl phosphonochloridothioate ( 4 ) under mild conditions. The target compounds were characterized by ¹H‐nuclear magnetic resonance (NMR), ¹³C‐NMR, and ³¹P‐NMR spectroscopy, as well as mass spectroscopy. The apparent structure of 4 was confirmed by optimization using the B3LYP/6‐311 + G(d,p) level in the Gaussian 09 program in acetonitrile. The nucleophilic substitution reactions of 4 with X‐anilines (XC₆H₄NH₂) and deuterated X‐anilines (XC₆H₄ND₂) were investigated kinetically in acetonitrile at 55.0°C. The free energy relationship with X in the anilines looked biphasic concave upwards with a break region between X = H and X = 3‐MeO, giving large negative ρ_X and small positive β_X values. The deuterium kinetic isotope effects were secondary inverse (k_H/k_D < 1: 0.789‐0.995) and the magnitudes, (k_H/k_D), increased when the nucleophiles were changed from weakly basic to strongly basic anilines. A concerted S_N2 mechanism is proposed on the basis of the selectivity parameters and the variation trend of the deuterium kinetic isotope effects with X.     

Evaluation of ADC measurements among solid pancreatic masses by respiratory-triggered diffusion-weighted MR imaging with inversion-recovery fat-suppression technique at 3.0 T

Purpose

The objective of this paper was to investigate the value of apparent diffusion coefficients (ADCs) for differential diagnosis among solid pancreatic masses using respiratory triggered diffusion-weighted MR imaging with inversion-recovery fat-suppression technique (RT-IR-DWI) at 3.0 T.

Materials and Methods

20 normal volunteers and 72 patients (Pancreatic ductal adenocarcinoma [PDCA, n = 30], mass-forming pancreatitis [MFP, n = 15], solid pseudopapillary neoplasm [SPN, n = 12], and pancreatic neuroendocrine tumor[PNET, n = 15]) underwent RT-IR-DWI (b values: 0 and 600 s/mm²) at 3.0 T. Results were correlated with histopathologic data and follow-up imaging. ADC values among different types of pancreatic tissue were statistically analyzed and compared.

Results

Statistical difference was noticed in ADC values among normal pancreas, MFP, PDCA, SPN and PNET by ANOVA (p < .001). Normal pancreas had the highest ADC value, then followed by PNET, PDCA, MFP and SPN. There was noticeable statistical difference in ADC values among PDCA, MFP and normal pancreas by Least Significant Difference (LSD) (p < .001). ADC of SPN was statistically lower than that of PNET (p = 0.1800 × 10^− 4), PDCA (p = 0.0300 × 10^− 4) and normal pancreas (p = 0.0007 × 10^− 4). ADC of PNET was statistically lower than that of normal pancreas (p = 0.0360) and higher than that of MFP (p = 9.3000 × 10^− 4).

Conclusions

ADC measurements using RT-IR-DWI at 3.0 T may aid to disclose the histopathological pattern of normal pancreas and solid pancreatic masses, which may be helpful in characterizing solid pancreatic lesions.