Q≤＞0.707对频率响应影响的证明

介绍了在电路理论教学中 Q≤ >0 .70 7对频率响应影响的证明方法 ,若在教学中补充该内容 ,则能加深学生对该课程相关内容的理解。     

ECR plasma etch fabrication of C-doped base InGaAs/InP DHBT structures: A comparison of CH4/H2/Ar vs BCl3/N2 plasma etch chemistries

We compare ECR plasma etch fabrication of self-aligned thin emitter carbondoped base InGaAs/InP DHBT structures using either CH₄/H₂/Ar or BCl₃/N₂ etch chemistries. Detrimental hydrogen passivation of the carbon doping in the base region of our structure during CH₄/H₂/Ar dry etching of the emitter region is observed. Initial conductivity is not recovered with annealing up to a temperature of 500°C. This passivation is not due to damage from the dry etching or from the MOMBE growth process, since DHBT structures which are ECR plasma etched in BCl₃/N₂ have the same electrical characteristics as wet etched controls. It is due to hydrogen implantation from the plasma exposure. This is supported with secondary ion mass spectroscopy profiles of structures which are etched in CH₄/D₂/Ar showing an accumulation of deuterium in the C-doped base region.     

准分子激光对钛宝石辐照作用的研究

采用波长为193 nm的ArF准分子激光对钛宝石进行辐照,对比辐照前后的吸收光谱,218 nm处的吸收增加幅度明显大于193 nm和266 nm的吸收峰.通过对不同品质因素(FOM)值样品在420 nm处的荧光强度检测,发现FOM值随荧光强度减小而增大,对比钛宝石样品在准分子激光辐照前后的420 nm荧光谱,可以发现荧光强度明显降低.在检测样品的电子顺磁共振(EPR)谱后发现,Ti3 离子的电子顺磁共振信号在辐照后强度明显增强.表明钛宝石在准分子激光辐照过程中有Ti4 离子向Ti3 离子转变趋势.     

Clinical role of diffusion-weighted imaging: neonatal studies

The application of diffusion-weighted imaging to the early diagnosis of neonatal cerebral infarction and hypoxic ischemic encephalopathy is illustrated. Diffusion-weighted images showed early infarction before conventional imaging in both cases. These were subsequently seen with conventional imaging on follow-up. In four cases of grades I and II hypoxic-ischemic encephalopathy (HIE) no abnormality was seen with either diffusion-weighted or conventional imaging. In four other cases of grades II and III HIE, much more extensive changes were seen with diffusion-weighted imaging than with conventional imaging. Follow-up scans with conventional imaging confirmed the abnormalities in the two surviving infants. Diffusion-weighted imaging may be particularly useful for the early diagnosis of ischemic-anoxic injury in infants.     

针对水轮机调节系统非最小相位的混合控制策略

串补输电系统中次同步谐振的模态阻尼分析主要采用复转矩系数法和特征根分析方法，但都需要复杂建模，且只能从大量计算结果中得到次同步谐振发生的规律，不能给出直观的机理解释。文中在系统等效为单机无穷大系统的情况下，推导出多模式次同步谐振各扭振模式阻尼的显式表达式。经验证，可以较精确地近似特征根分析的结果。该表达式在理论上有助于进一步理解次同步谐振的机理和系统参数对次同步谐振的影响，在工程应用上可用于快速、方便地分析各种运行条件下次同步谐振的风险及其严重程度。     

磁共振成象测井的处理解释

磁共振成象测井（ＭＲＩＬ）可以提供地层有效孔隙度、束缚流体孔隙体积、可动流体孔隙体积及渗透率等储层信息。结合其它常规测井资料，还可以提供地层的油水饱和度。文中详细介绍了磁共振成象测井资料的处理解释方法，并提供了解释应用实例。     

肺癌的MRI征像及诊断价值

本文将我院1991年9月至1995年9月经MRI检查确诊的34例肺癌的MRI表现及图像特征进行分析，并对肺癌MRI诊断价值进行探讨。用安科公司生产的ASP—O15永磁型扫描仪，采用SE序列，T－WI：30／500，TZ－WI：90／1800，做冠状及横断面扫描。     

Water status of cooked white salted noodles evaluated by MRI

Transverse relaxation time (T₂)-weighted images and T₂ maps of white salted noodles (WSN) were investigated by magnetic resonance imaging technique. T₂-weighted images and T₂ maps clearly showed the differences in water status between noodles. The migration of moisture from surface regions to central regions of boiled WSN at different migration rates were investigated during storage. The distribution of T₂ values changed differently depending on the cooking and storage times. The small differences in T₂ values between surface region and central region of noodles cooked for 5 and 15 min were attributed to the limited water absorption during short cooking time, which resulted in high firmness. The changes in starch granules morphology observed under scanning electron microscope and the increase of noodle firmness measured by texture analyzer were significantly affected by the water status in noodles. The water status can be controlled by the cooking time.     

指数形式关联噪声驱动下单模激光线性模型的随机共振

研究了具有指数形式关联的两白噪声驱动下单模激光线性模型受信号调制后的输出信噪比，发现了随机共振现象。根据计算结果讨论了噪声(噪声强度、噪声间互关联程度和关联时间)和信号(信号频率和信号强度)对信噪比的影响。     

Direct ESR and spin trapping methods for the detection and identification of radical fragments in Nafion membranes and model compounds exposed to oxygen radicals

Direct electron spin resonance (ESR) and spin trapping methods are used in our laboratory in order to identify radical fragments in fluorinated membranes (Nafion) used in fuel cells and in model compounds when exposed to reactive oxygen species. Oxygen radicals were generated by the Fenton reaction, by the photo-Fenton method, and by UV-irradiation of aqueous H₂O₂ solutions. Direct ESR detection led to the identification of fluorinated radical fragments in UV-irradiated Nafion neutralized by Cu(II), Fe(II), and Fe(III) cations and exposed to H₂O₂. In Nafion exposed to the Fenton reagent in the presence of DMPO (5,5-dimethyl-1-pyrroline) as the spin trap, radical adducts of hydroxyl and carbon-centered radicals (CCRs) were detected. A fluorinated model compound, perfluro-(2-ethoxyethane) sulfonic acid (CF₃CF₂OCF₂CF₂SO₃H, PFEESA), that mimics the side chain of Nafion was chosen for study, with the goal to shed light on the more complicated degradation processes in the polymeric membranes. Analysis of the spin adducts obtained from UV-irradiated PFEESA in the presence of H₂O₂ and MNP (2-methyl-2-nitrosopropane) as the spin trap suggested that the side chain of Nafion is a possible site of attack by oxygen radicals.