多延迟动脉自旋标记技术的量化原理及其临床研究

动脉自旋标记(Arterial Spin Labeling,ASL)技术作为一种新兴的灌注成像技术,能够在无需对比剂下进行无损成像,其临床应用日趋广泛。本文阐述了多延迟ASL技术的量化原理,然后与正电子发射型计算机断层显像技术(Positron emission computed tomography,PET)和电子计算机断层扫描技术(Computed tomography,CT)进行对比,分析了该技术在实际应用中的优势。最后,总结了多延迟ASL技术的临床研究内容及科研前景,并探讨了其在脑血管等疾病研究中的应用,指出多延迟ASL技术对于脑血管等疾病的预防及治疗具有巨大的潜力。

H.264变换编码与量化原理分析

详细分析了 H .2 64视频编码标准中的整数变换和量化过程。 H .2 64采用 4× 4整数变换 ,并将尺度调整融合在量化过程中 ,降低变换算法复杂度和减少乘法次数 。

逆序量化原理及其应用

本文提出“逆序量化原理”并给出其证明；同时，将其用于行列式有关性质、定理的证明。这使得证明通俗易懂且过程大为简化，可指导工程数学教材的建设与课堂教学。

量化分级管理在“五小”长效管理中的运用思考

[目的]探讨食品卫生量化分级管理原理在“五小”经营单位长效管理中运作模式。[方法]按食品卫生量化分级管理原理对“五小”经营单位硬件设施和软件管理进行全面整改,并按量化分级要求进行评级和挂牌。[结果]经近一年的整治和管理,“五小”经营单位的总体面貌较前有显著改观。[结论]为使量化分级管理原理真正在“五小”长效管理模式中顺利运作,并取得监督效果,要做到宣传与培训,荣誉与责任,信心与决心,监督与指导和长效与突击并存。

基于Slant变换的半脆弱水印算法

为了使算法同时具有较高的定位精度和鲁棒性,提出了一种基于Slant变换的半脆弱性数字水印算法.算法引入"相关块组"的概念,结合Slant变换高能量集中性及直流量化原理完成水印嵌入过程,在认证过程中使用了定位参考块.实验结果表明,该算法能容忍一定程度的JPEG压缩、Gauss噪声等偶然篡改,对图像中发生的篡改可以有效地检测并进行精确地定位.

轻质混凝土技术问题综述

从发展、分类、填料体积分数原理、轻量化原理及技术问题、工程应用、性能影响因素等方面对轻质混凝土材料进行了介绍,提出了目前存在的问题,展望了轻质混凝土的研究方向,可以为轻质混凝土的制备和应用提供参考。

新型频率测量方法的研究

根据量化时延原理的短时间间隔精确测量方法 ,在时频测量领域有着广泛的用途。该方法可被广泛地应用于高精度频率、时间及相位等信号的测量。文章详细介绍了此种新型时间间隔测量方法的原理 ,及其与一种从多周期同步法发展而来的高精度、定闸门测频方法的相互结合。从而实现了高速、高精度、连续的宽频率范围的测量。

控制球阀质量评价与常用标准的性能测试差异分析与应用研究

为了提升控制球阀的可靠性、安全性等关键技术指标以及科学的评定产品质量等级,更好地满足石油石化等工况的精准选型与使用要求。分析研究了控制球阀质量评价办法与国内外常用球阀标准现状、产品判定原则、产品性能测试项目差异及影响,阐述了现有球阀标准性能测试的不足与标准判定原则的局限性以及评价办法中的产品质量量化分等原理,列举了控制球阀质量评价办法中创新设计的性能测试项目与方法,为石油石化用户采购选优评级提供科学依据,为控制球阀新标准的制定与球阀标准的修订提供技术指引和支撑。

First principles calculation on electronic structure,chemical bonding,elastic and optical properties of novel tungsten triboride

The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calculated energy band structures show that the hP24 phase WB3 is metallic material.The density of state(DOS) and the partial density of state(PDOS) calculations show that the DOS near the Fermi level is mainly from the W 5d and B 2p states.Population analysis suggests that the chemical bonding in hP24-WB3 has predominantly covalent characteristics with mixed covalent-ionic characteristics.Basic physical properties,such as lattice constant,bulk modulus,shear modulus and elastic constants Cij were calculated.The elastic modulus E and Poisson ratio υ were also predicted.The results show that hP24-WB3 phase is mechanically stable and behaves in a brittle manner.Detailed analysis of all optical functions reveals that WB3 is a better dielectric material,and reflectivity spectra show that WB3 can be promised as good coating material in the energy regions of 8.5-11.4 eV and 14.5-15.5 eV.

Generation of electricity from CO_2 mineralization: Principle and realization

Current CO2 reduction and utilization technologies suffer from high energy consuming. Thus, an energy favourable route is in urgent demanding. CO2 mineralization is theoretically an energy releasing process for CO2 reduction and utilization, but an approach to recovery this energy has so far remained elusive. For the first time, here we proposed the principle of harvesting electrical energy directly from CO2 mineralization, and realized an energy output strategz1 for CO2 utilization and reduction via a CO2-mineralization fuel cell （CMFC） system. In this system CO2 and industrial alkaline wastes were used as feedstock, and industrial valuable NaHCO3 was produced concomitantly during the electricity generation. The highest power density of this system reached 5.5 W/m2, higher than many microbial fuel cells. The maximum open circuit voltage reached 0.452 V. Moreo- ver, this system was demonstrated viable to low concentration CO2 （10%） and other carhonation process. Thus, the existing of an energy-generating and environmentally friendly strategy to utilize CO2 as a supplement to the current scenario of CO2 emis- sion control has been demonstrated.

Progress in optimization of mass transfer processes based on mass entransy dissipation extremum principle

The mass entransy and its dissipation extremum principle have opened up a new direction for the mass transfer optimization. Firstly, the emergence and development process of both the mass entransy and its dissipalion extremum principle are reviewed. Secondly, the combination of the mass entransy dissipation extremum principle and the finite-time thermodynamics for opti- mizing the mass transfer processes of one-way isothermal mass transfer, two-way isothermal equimolar mass transfer, and iso- thermal throttling and isothermal crystallization are summarized. Thirdly, the combination of the mass entransy dissipation ex- tremum principle and the constructal theory for optimizing the mass transfer processes of disc-to-point and volume-to-point problems are summarized. The scientific features of the mass entransy dissipation extremam principle are emphasized.

Quantization of Space in the Presence of a Minimal Length

In this article, we apply the Generalized Uncertainty Principle （GUP）, which is consistent with quantum gravity theories to an elementary particle in a finite potential well, and study the quantum behavior in this system. The generalized Hamiltonian contains two additional terms, which are proportional to ap3 （the result of the maximum momentum assumption） and a2p4 （the result of the minimum length assumption）, where a - 1/MpIc is the GUP parameter. On the basis of the work by Ali et al., we solve the generaiized Schrodinger equation which is extended to include the a2 correction term, and find that the length L of the finite potentiai well must be quantized. Then a generalization to the double-square-well potential is discussed. The result shows that all the measurable lengths especially the distance between the two potential wells are quantized in units of aolp1 in GUP scenario.