国家级重大科技计划中标准化科研项目的对比分析及对我国标准化科研工作的借鉴意义——以国家重点研发计划、NITRD和PRISM为例

本文使用文献调研法、网站调研法、特征归纳法、分析比较法对美国NITRD、日本PRISM、我国重点研发计划进行了调研和分析比较。全面梳理了所收集到的科技计划的背景、战略意义及目标,通过对比分析,发现在科技计划的管理模式上、资助方式及产学研结合方面,日本PRISM计划和美国NITRD计划更加关注高校、初创私营科研机构的创新环境,促进科研创新环境的建立和发展。并从标准化科研角度切入,建议应在科技计划中设立标准化科研专项并持续加大标准化专项经费投入,及对标准化专业科研团体的扶持和培育力度。

Effect of prisms on visual acuity,contrast sensitivity and nystagmus in patients with albinism

AIM:To investigate the effect of using base-out prisms on nystagmus,visual acuity and contrast sensitivity in patients with albinism.METHODS:In this interventional study,patients with albinism who had nystagmus were enrolled.A comprehensive eye exam was conducted,which included refraction,assessment of far and near vision acuity,and contrast sensitivity measurements.To check for the nystagmus,a videonystagmography was used.The tests were carried out in three modes:without any correction,with optical correction,and with correction using base-out prisms in three different powers,including 4,6,and 8 prism diopters.RESULTS:Totally 23 patients with average age of 28.65±12.13 were examined.It was found that the use of optical correction and optical correction with prisms resulted in a statistically significant improvement in both far(at least:P<0.006)and near visual acuity(at least:P<0.001 except for prism 8;P<0.02).In addition,contrast sensitivity significantly improved at all low and medium frequencies except for correction with prism 8 in frequency 1.5(at least:P<0.01 except for prism 4,frequency 6;P=0.04).no significant improvement was observed in the evaluation of nystagmus characteristics.CONCLUSION:Optical correction with a prism can improve visual acuity and some spatial frequencies,but failed to improve nystagmus parameters.

PRISM媒体分析平台在IP播出的应用

当前,广播电视的传输技术正在实现从SDI技术向IP技术的传输架构过渡,如何监测SDI/IP混合环境中的信号数据仍然是挑战。本文介绍了PRISM媒体分析平台实际应用中的插件选项,分析其中监测的IP系统数据,研究将多个IP信号与PRESET插件结合的可行性。

发达国家重大科技计划研究及对我国标准化科研的启示——以日本PRISM计划为例

随着全球化的发展,世界主要经济体将“标准化战略”作为一种通过构建技术壁垒提高国际竞争力的重要手段。本文通过以日本PRISM计划下设的“推进标准利用支持专项”为例,分析日本政府推进政府与私营部门协同开展标准化工作的基本思路、政策布局和具体做法,为我国政府与私营部门协调开展标准化工作,参与国际竞争提供参考。

Cracks coalescence mechanism and cracks propagation paths in rock-like specimens containing pre-existing random cracks under compression

The mechanism of cracks propagation and cracks coalescence due to compressive loading of the brittle substances containing pre-existing cracks （flaws） was modeled experimentally using specially made rock-like specimens from Portland Pozzolana Cement （PPC）. The breakage process of the specimens was studied by inserting single and double flaws with different inclination angles at the center and applying uniaxial compressive stress at both ends of the specimen. The first crack was oriented at 50＆#176; from the horizontal direction and kept constant throughout the analysis while the orientation of the second crack was changed. It is experimentally observed that the wing cracks are produced at the first stage of loading and start their propagation toward the direction of uniaxial compressive loading. The secondary cracks may also be produced in form of quasi-coplanar and/or oblique cracks in a stable manner. The secondary cracks may eventually continue their propagation in the direction of maximum principle stress. These experimental works were also simulated numerically by a modified higher order displacement discontinuity method and the cracks propagation and cracks coalescence were studied based on Mode I and Mode II stress intensity factors （SIFs）. It is concluded that the wing cracks initiation stresses for the specimens change from 11.3 to 14.1 MPain the case of numerical simulations and from 7.3 to 13.8 MPa in the case of experimental works. It is observed that cracks coalescence stresses change from 21.8 to 25.3 MPa and from 19.5 to 21.8 MPa in the numerical and experimental analyses, respectively. Comparing some of the numerical and experimental results with those recently cited in the literature validates the results obtained by the proposed study. Finally, a numerical simulation was accomplished to study the effect of confining pressure on the crack propagation process, showing that the SIFs increase and the crack initiation angles change in this case.

Failure characteristics and its influencing factors of rock-like material with multi-fissures under uniaxial compression

The compression test on rock-like specimens with prefabricated closed multi-fissures made by pulling out the embedded metal inserts in the precured period was done on the servo control uniaxial loading instrument. The influence of fissure inclination angle and distribution density on the failure characteristics of fissure bodies was researched. It was found that, the fissure inclination angle was the major influencing factor on the failure modes of fissure bodies. The different developmental states of micro-cracks would appear on specimens under different fissure inclination angles. However, the influence of fissure distribution density on the failure mode of fissure bodies was achieved by influencing the transfixion pattern of fissures. It was shown by the sliding crack model that, the effective shear, which drove the relative sliding of the fissure, was a function of fissure inclination angle and friction coefficient of the fissure surface. The strain-softening model of fissure bodies was established based on the mechanical parameters that were obtained by the test of rock-like materials under the same experimental condition. And the reliability of experimental results was identified by using this model.

A damage constitutive model of rock-like materials containing a single crack under the action of chemical corrosion and uniaxial compression

To describe the deformation and strength characteristics of the corroded rock-like specimens containing a single crack under uniaxial compression,a damage constitutive model combining hydro-chemical damage with coupling damage of micro-flaws and macro-cracks is proposed.Firstly,based on phenomenological theory,the damage variable of the rock-like specimens subjected to water environment erosion and chemical corrosion is obtained.Secondly,a coupled damage variable for cracked rock-like specimens is derived based on the Lemaitre strain equivalence hypothesis,which combines the Weibull statistical damage model for micro-flaws and the fracture mechanics model for a macro single crack.Then,considering the residual strength characteristics of the rock-like materials,the damage variable is modified by introducing the correction coefficient,and the damage constitutive model of the corroded rock-like specimens with a single crack under uniaxial compression is established.The model is verified by comparing the experimental stress−strain curves,and the results are in good agreement with those provided in the literature.Finally,the correction coefficient of the damage variable proposed in this paper is discussed.The damage constitutive model developed in this paper provides an effective method to describe the stress−strain relationship and residual strength characteristics of the corroded rock-like specimens with a single crack under uniaxial compression.

Non-parallel double-crack propagation in rock-like materials under uniaxial compression

Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological disaster. In this study, crack propagation processing was studied through loading pre-fractured specimens of concrete block, termed as rock-like material, in uniaxial compression tests. New non-parallel double-crack geometry was introduced to observe crack coalescence. The flaw combinations are different from the normally used flaw configurations. In addition, ultrasonic detection tests were performed on the test blocks. The stress and strain data of these tests and characteristic parameters of sound wave were recorded. The stress-strain curves of each test block under the uniaxial compression test were drawn, relations among deformation characteristics and crack angle of the crack specimens, and their overall strength were analyzed. It is found that strength of the specimen decreases as crack inclination increases under two crack inclinations. The highest uniaxial compressive strength is found in the specimen with the cracks at the same angle in different directions. Based on description of the crack initiation location, crack surface and the ultimate failure patterns, failure modes of eight subtype for test blocks are divided into three categories. It is expected that the study results could be beneficial for engineering application of jointed rock masses.

An experimental study on fracture mechanical behavior of rock-like materials containing two unparallel fissures under uniaxial compression

Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalescence process, a series of uniaxial compression tests were carried out for rock-like material with two unparallel fissures.In the present study, cement, quartz sand, and water were used to fabricate a kind of brittle rock-like material cylindrical model specimen. The mechanical properties of rock-like material specimen used in this research were all in good agreement with the brittle rock materials. Two unparallel fissures（a horizontal fissure and an inclined fissure） were created by inserting steel during molding the model specimen.Then all the pre-fissured rock-like specimens were tested under uniaxial compression by a rock mechanics servocontrolled testing system. The peak strength and Young＇s modulus of pre-fissured specimen all first decreased and then increased when the fissure angle increased from 0？to 75？.In order to investigate the crack initiation, propagation and coalescence process, photographic monitoring was adopted to capture images during the entire deformation process.Moreover, acoustic emission（AE） monitoring technique was also used to obtain the AE evolution characteristic of prefissured specimen. The relationship between axial stress, AE events, and the crack coalescence process was set up： when a new crack was initiated or a crack coalescence occurred, thecorresponding axial stress dropped in the axial stress–time curve and a big AE event could be observed simultaneously.Finally, the mechanism of crack propagation under microscopic observation was discussed. These experimental results are expected to increase the understanding of the strength failure behavior and the cracking mechanism of rock containing unparallel fissures.

STUDY ON DAMAGE BIFURCATION AND INSTABILITY OF ROCK-LIKE MATERIALS

The critical bifurcation orientation and its corresponding hardening modulus for rock-like geomaterials are derived by considering the effect of stiffness degradation and volumetric dilatancy under the assumption of isotropic damage. The dependency of the localized orientation on the degree of damage and initial Poisson＇s ratio of rock is examined and the bifurcation behavior of the uniaxial compression sample under the plane-stress condition is compared with that under plane-strain condition. It is shown that the localization orientation angle intimately depends on both the initial Poisson＇s ratio and degree of damage for the rock sample under the uniaxial compression condition. As the initial Poisson＇s ratio or degree of damage increases, the orientation angle of the plane on which localization tends to be initiated gets to decrease. At the same time, the localization orientation angle of a rock sample under the plane-stress condition is larger than that under the plane-strain condition.

Mechanism of stress distribution and failure around two different shapes of openings within fractured rock-like materials

The complexity of a rock masses structure can lead to high uncertainties and risk during underground engineering construction.Laboratory tests on fractured rock-like materials containing a tunnel were conducted,and twodimensional particle flow models were established.The principal stress and principal strain distributions surrounding the four-arc-shaped and inverted U-shaped tunnels were investigated,respectively.Numerical results indicated that the dip angle combination of preexisting fractures directly affects the principal stress,principal strain distribution and the failure characteristics around the tunnel.The larger the absolute value of the preexisting fracture inclination angle,the higher the crushing degree of compression splitting near the hance and the larger the V-shaped failure zone.With a decrease in the absolute value of the preexisting fracture inclination angle,the compressive stress concentration of the sidewall with preexisting fractures gradually increases.The types of cracks initiated around the four-arc-shaped tunnel and the inverted U-shape tunnel are different.When the fractures are almost vertical,they have a significant influence on the stress of the sidewall force of the four-arc-shaped tunnel.When the fractures are almost horizontal,they have a significant influence on the stress of the sidewall of the inverted U-shaped tunnel.The findings provide a theoretical support for the local strengthening design of the tunnel supporting structure.

Experimental study of polyurethane foam reinforced soil used as a rock-like material

In this study, p o ly u reth an e foam ty p e th e rm o se t polym erizing, d u e to chem ical reaction b e tw e e n itsliquid ingredients, w as teste d as b in d e r afte r solidifying and th e n a rock-like m aterial m ixing w ith asandy silt ty p e soil w as prep ared . The uniaxial com pressive stren g th s （UCSs） o f p o ly u reth an e foamreinforced soil specim ens w ere d e term in ed for different p o ly u reth an e ratios in th e m ixture. A dditionally,a series o f te sts o n slake durability, im pact value, freezing-th aw in g resistance, and ab rasio n resistance ofp o ly u reth an e reinforced soil （PRS） m ix tu re w as co n d u cted . The UCS values over 3 M Pa w ere m easuredfrom th e PRS specim ens. The testin g results show ed th a t tre a te d soil can econom ically b ecom e adesirable rock-like m aterial in term s o f slake d u ra b ility a n d resistances ag ain st freezing-thaw ing, im pacteffect an d abrasion. As a n o th e r ch aracteristic o f th e rock-like m aterial m ade w ith p o ly u reth an e foam,u n it volum e w eig h t w as found to be q uite low er th a n th o se o f n atu ral rock m aterials.

Identification of the Discrete Element Model Parameters for Rock-Like Brittle Materials

An inverse method for parameters identification of discrete element model combined with experiment is proposed.The inverse problem of parameter identification is transmitted to solve an optimization problem by minimizing the distance between the numerical calculations and experiment responses.In this method,the discrete element method is employed as numerical calculator for the forward problem.Then,the orthogonal experiment design with range analysis was used to carry out parameters sensitivity analysis.In addition,to improve the computational efficiency,the approximate model technique is used to replace the actual computational model.The intergeneration projection genetic algorithm(IP-GA)is employed as the optimization algorithm.Consequently,the parameters of the discrete element model are determined.To verify the effectiveness and accuracy of the inverse results,the comparisons of shape deviation experiments with discrete element simulations are provided.It indicates that the effective and reliable discrete element model parameters can be quickly obtained through several sets of experimental data.Hence,this inverse method can be applied more widely to determine the parameters of discrete element model for other materials.

Prism彩色电子纸在装饰应用场景中的创新实践

基于Prism彩色电子纸原理,通过与其他电子纸技术对比分析,着重介绍了Prism彩色电子纸的原理、种类和特点,以及其在指示牌、温湿度计、服饰类、建筑类等装饰型场景的创新实践,并对Prism未来的发展方式进行展望。

质量比对D形截面柱体流致振动的影响

利用涡激振动进行海流能收集的VIVACE装置是新能源领域的研究热点.应用FLUENT软件采用k-ωSST湍流模型和Newmark-β法,通过数值模拟探究了四个质量比(2,5,7和10)在迎流角90°下D形截面柱体的流致振动响应,系统分析了D形截面柱体在横流向上的振动幅值、频率、平衡位置偏移量、尾涡脱落模式以及能量转化效率.所模拟的雷诺数范围为288~2880,对应的约化速度为2~20.结果表明,质量比对D形截面柱体流致振动的影响明显,质量比会改变D形截面柱体流致振动的响应分支.质量比越大,D形截面柱体进入驰振对应的约化速度越低;质量比增大,D形截面柱体平衡位置偏移量相对减小.随着约化速度的增大,D形截面柱体出现了涡激振动、涡激振动-驰振及完全驰振等响应分支.在所模拟的范围内,D形截面柱体高能量转化效率出现在涡激振动分支,而不是在驰振分支;在质量比为10且约化速度为4.5时,一级能量转化效率达到最大值44%.相关研究可为VIVACE装置的振子选型提供参考.

直角三棱镜补充视角的密封圈缺陷检测研究

为解决三维激光检测中被测物体底面点云无法被高效获取的问题,本文提出了基于直角三棱镜折射原理的补充视角三维点云扫描获取方法。该方法使用直角三棱镜将底面图像折射到侧面,弥补了三维检测的底面检测视角缺失的问题,补充了底面检测视角。本文以密封圈作为缺陷检测对象,采用结构光三维相机采集三维点云。与直接扫描法相比,本方法可以一次性实时、快速地寻找出密封圈完整的表面缺陷,尤其使底面缺陷检测变得更容易,且无需设置特殊的夹取装置或复杂的机械臂等机械结构,仅需增加一块直角三棱镜。实验证实,直角三棱镜补充视角的点云扫描方法能够达到成像要求,对常见的密封圈断裂缺陷与塌陷缺陷均可很好的检出,检测准确率可达到100,满足密封密封圈缺陷检测的需求。

双自由度D形截面柱体流致振动的二维数值模拟

本文研究了D形截面柱体在顺流向和横流向两个自由度下的流致振动特性,迎流角为90°,质量比为2.6,雷诺数为370~3685,应用RANS方程采用SST k-ω湍流模型和Newmark-β法求解水流运动和柱体运动,入口流速采用匀加速法,检验了数值模型的网格和时间步长敏感性,并与相关文献的实验结果进行对比,验证了数值模型的可靠性。基于计算结果,系统分析了D形截面柱体的振幅、振动频率、水动力系数、尾涡脱落模式,以及平均位置偏移情况。结果表明,双自由度D形截面柱体在约化速度为8~14的区间内表现为涡激振动-驰振模式,尾涡多为2S和S+2S交替脱落,双自由度振幅比单自由度有显著的增大。升力主要偏向截面的直线边一侧,且升力出现了多个倍频。横流向和顺流向平均偏移量最大都可达到一倍特征长度以上。

双面棱镜现场检校和标定技术研究

全站仪组网监测项目中,控制网精度决定监测精度,为解决全站仪组网监测控制网精度较差的问题,对传递控制坐标设备双面棱镜装配结构及测量原理进行深入研究,提出一种有效的解决方案,通过标定双面棱镜左右侧常数来保证双面棱镜中心唯一,以减少坐标传递误差,从而提高整个监测控制网精度。另外,由于双面棱镜制造精度较差,对全站仪测量中双面棱镜的角度、距离误差进行理论研究,提出一种采用全站仪对双面棱镜测量常数进行现场检校、标定的方法,该方法对外部测量环境要求低,操作简单,现场实际标定常数较厂家提供常数的精度有大幅提高,并在某地铁监测项目进行验证,全站仪组网监测精度提高约1 mm,具有较高的实用价值。

用分光计测三棱镜折射率光路图的MATLAB动画演示

建立了三棱镜光路图的数学模型,应用MATLAB绘制光路图,检验了模型的正确性.随着三棱镜的旋转,直观地演示了分光计中光路图和偏向角的变化过程,指出了最小偏向角.

基于PRISM和泰森多边形的地形要素日降水量空间插值研究

以黑河流域河西走廊中段地区为例,利用该研究区年、月降水与地形间较强的相关性特点,在PRISM方法的基础上对该地区日降水量进行了空间插值计算。文章提出了以月降水量的PRISM空间插值结果为该月逐日降水空间分布的参考本底,利用泰森多边形方法确定空间日降水的概率,从而实现黑河流域河西走廊中段地区日降水的空间制图方法,并对该方法得到的日降水时空数据集进行了误差分析和评估。分析结果表明,这一方法简单可靠,满足分布式水文模型或相关陆表过程分布式模拟对分布式日降水数据时空精度的要求。