玩滤镜,选圆形还是方片? NiSi F-STOPPER PRO 100方片滤镜快评

正拍摄风光照片少不了要用到各种好玩的滤镜,我们将通过对NiSi F-STOPPER PRO 100的评测向你展示方片滤镜系统在选购、使用上的一些要点。近日,耐司公司发布了旗下最新型号的方形滤镜系统——NiSi F-STOPPER PR0 100,该系统包括耐司全新开发的方形滤镜支架、Nisi ND100o方形滤镜(100mm~*100mm)、方形渐变滤镜(100mm~*150mm)及方形偏光镜(100mm~*100mm),通过转接环适用于82mm口径以下的镜头。对于更大口径镜头的用户,可以观望耐司即将推出的1 50方形滤镜系统。     

蓄能空调系统中蓄能槽体的设计选型及经济性分析

阐述了蓄能空调系统中的蓄能槽体的分类和性能以及方形钢板蓄能槽体的设计选型,介绍了工程实践中常用的圆形槽体和方形槽体的容积与重量关系的统计资料,可供蓄能设备的选型设计及估算重量作参考.     

方形孔轴套冷挤压成形工艺研究及数值模拟分析

目的通过对方形孔轴套的分析,确定冷挤压工艺成形方形孔轴套的可行性,为方形孔轴套的实际生产提供理论依据和支持。方法结合Deform软件,对方形孔轴套的挤压成形过程进行了数值模拟,重点分析了零件在冷挤压成形过程中的应力场、应变场的变化情况。结果通过模拟得出,在成形难度大的区域没有出现折叠和破裂缺陷。结论确定了冷挤压工艺成形方形孔轴套的可行性。     

方形升降式网箱下沉过程防倾覆装置与技术的研究

针对方形升降式网箱在接近下沉临界状态时极易发生整体侧倾覆而导致下沉失败的关键技术难题,通过对升降式网箱下沉过程的动态变化研究,全面分析了引起网箱侧翻的内外影响因素,探明了风浪流作用和网箱水下配重导致的倾覆转动力矩是造成其侧倾覆的主要外内在原因;并采取相应技术手段,在原有方形升降式网箱的结构基础上,构建了网衣十字交叉网筋和网底刚性支撑杆组件组成的防倾覆装置系统,改变了网箱下沉倾斜过程的受力状态,实现了网箱在恶劣海况条件下的稳定下沉。试验与模拟结果显示,对于配置有防倾覆装置的正方体型升降式网箱系统,其下沉稳定倾角不大于27°,从而为方形升降式网箱动态下沉自平衡技术的创立和完善提供理论依据和方法。     

方形量块的校准

方形量块以耐磨材料制造,区别于普通的截面为矩形的量块,其外形为正方形,且量块中央存在贯穿的中孔,被广泛使用于机械加工制造,航空航天等各领域各方面.文章通过将方形量块与截面为矩形的量块相比较,介绍了方形量块的结构特性、使用特性,并结合计量校准工作的实际,针对方形量块的计量特性,提出了方形量块的校准项目和校准方法,并讨论其...     

基于多CCD规则零件二维尺寸的测量

讨论了一种基于多CCD的规则零件二维尺寸在线测量模型及关键技术,介绍了一种基于2-CCD的薄片方形零件在线测量系统。实验表明,该系统测量精度高,速度快,可作为测量系统模型广泛应用于包装线的纸板在线宽度测量等各种大型零件精密测量中。     

四边简支新型类方形蜂窝夹层结构振动特性研究

新型类方形蜂窝是六边形蜂窝的一种过渡形式,对其等效弹性参数和振动特性的研究具有重要意义。采用改进的Gibson公式对比分析了双壁厚与等壁厚类方形蜂窝夹芯的面内等效弹性参数的差异,并应用经典层合板理论分析了不同等效弹性参数下2种壁厚类型的四边简支类方形蜂窝夹层结构的振动特性,基于有限元仿真技术分析了不同壁厚类方形蜂窝夹层结构的振动特性,并与理论分析结果进行对比。结果表明等效弹性参数的数值模拟结果与理论值基本吻合。在蜂窝基本结构参数相同的条件下,双壁厚类方形蜂窝夹芯的面内等效剪切模量、面外刚度和等效密度均比等壁厚类方形蜂窝夹芯大;在低阶振动模态下,双壁厚类方形蜂窝夹层结构的固有频率比等壁厚类方形蜂窝夹层结构的低,在高阶振动模态下,双壁厚类方形蜂窝夹层结构的固有频率比等壁厚类方形蜂窝夹层结构的高;影响夹层结构固有频率的3个主要因素所占权重由大到小依次为蜂窝夹芯yoz面等效剪切模量、蜂窝夹芯等效密度,蜂窝夹芯壁厚。研究结果表明采用经典层结构理论计算得到类方形蜂窝夹层结构的固有频率与数值仿真结果的一致性较好,这进一步证明了采用改进Gibson公式得到的类方形蜂窝夹芯等效弹性参数的正确性,同时证明了将该振动理论运用到一般蜂窝夹层结构研究的可行性,为扩展研究其他类型蜂窝夹层结构振动特性奠定了基础。     

卷破波斜向作用下方形桥墩砰击荷载研究

沿海桥梁常受到破碎波浪作用,其中卷破波砰击严重威胁结构安全。该文通过理论和试验相结合的方法研究了方形桥墩受到的卷破波砰击荷载。以结构破波荷载经验计算公式和MLM理论模型为基础,建立了方形截面桥墩卷破波砰击荷载理论计算模型。通过卷破波水槽试验探究砰击角度与砰击荷载的关系;对比不同砰击角度理论和试验下方形桥墩截面砰击压强时程,验证了理论模型的有效性,结合试验与理论模型确定了不同砰击角度下方形桥墩卷曲因子的取值范围。研究表明：卷破波砰击方向与方形桥墩迎水轴向夹角越小,砰击荷载越大;该文提出的理论模型能很好地描述方形截面砰击压强时程随砰击角度的变化情况;根据试验结果拟合得出了方形截面卷曲因子随砰击角度的变化公式。     

改进的引力模型耦合明文像素相关交叉机制的图像加密算法

目的解决当前图像加密技术严重依赖混沌系统,使其通用性较差,难以直接加密非方形图像,且因混沌系统的周期性,算法的安全性不足的问题。方法提出了改进的引力模型耦合明文像素相关交叉算子的图像加密算法。首先,利用多个一维混沌映射,定义联合混沌变换模型,输出密钥流;随后,基于明文像素位置,设计像素相关交叉机制,联合密钥流,对明文进行高效置乱;构造质量动态变化函数,用其替代传统引力模型中的恒定粒子质量,增强算法的敏感性,并用改进的引力模型对置乱图像完成扩散,彻底改变像素值;最后,构建密文增强模型,对输出密文进行二次扩散,扩大密文的NPCR(Number of pixel change rate)与UACI(Unified average changed intensity)值。结果实验结果表明:与当前图像加密机制相比,所提加密算法不但可以扩散方形图像,而且能够对非方形目标直接加密,具有更高的通用性与安全性,以及更强的抗差分攻击能力。结论所提出的算法能够加密非方形尺寸的图像,具有较强的通用性与安全性。     

复合加固方形木柱的抗震性能分析

为了提高方形木柱的承载能力和抗震性能,提升古建木结构的抗震安全性,提出采用内嵌钢筋、外包碳纤维(carbon fiber reinforced polymer, CFRP)布复合加固木柱。通过方形木柱的低周往复荷载试验,研究了不同加固模式、钢筋用量、CFRP布加固量等因素对木柱抗震加固效果的影响;利用有限元软件OpenSees对复合加固方形木柱的抗震性能开展了数值模拟,通过数值模拟结果和试验数据的对比验证了有限元模型的可靠性;分析了轴向荷载、钢筋直径、CFRP布层数等参数对复合加固方形木柱滞回性能、侧向承载能力、延性性能、刚度退化以及耗能能力的影响。分析结果表明,内嵌钢筋可以显著提升方形木柱的侧向承载能力和耗能能力;外包CFRP布能够限制木材横向变形和内嵌钢筋的外凸,提高方形木柱的延性性能,延缓其刚度退化;复合加固能够大幅度提高方形木柱侧向承载力、延性及耗能能力,改善其刚度和强度退化,抗震加固效果显著。     

电容层析成像三维图像重建研究

进行了电容层析成像(ECT)三维图像重建的仿真研究。首先利用COMSOL软件对ECT传感器进行三维建模,基于其高精度的有限元求解,计算ECT的灵敏度矩阵;其次,基于Matlab软件实现了基于线性反投影(LBP)及Landweber迭代算法的ECT图像重建,并利用图像显示程序获得了三维重建图像;最后,对球体及圆柱体模型进行了三维ECT图像重建,获得了较好的重建结果。     

一种电容层析成像图像重建优化算法

提出一种电学层析成像(ECT)图像重建优化算法。通过将传统正则化算法转化为最小二乘问题进行求解,结合lp范数逼近正则化最小化问题,利用重新加权的方法进行迭代计算。以油-气两相流模型进行仿真及静态实验,将所提出的优化算法与常用的LBP、Landweber迭代及Tikhonov正则化算法进行对比。结果表明,与常用算法相比,采用该优化算法对管道中心物体及多物体分布流型进行图像重建,其图像相对误差均为最低,且重建图像的形状保真度明显提高。     

基于改进的LBP人脸识别算法

针对基本LBP算子提取的特征不够完整,不能全面地表达出人脸局部特征的问题,提出了基于分块的完备局部二值模式(CLBP)人脸识别算法。首先对原始人脸图像进行分块处理,对每一分块的图像进行局部差异值和中心像素灰度值分析,用Su2CLBP(8,2)、Mu2CLBP(8,2)和CCLBP(8,2)算子分别提取每一分块的直方图统计特征。然后将所有分块的CLBP直方图序列连接起来,得到人脸图像的CLBP特征,将其作为人脸的鉴别特征用于分类识别。最后利用Chi平方统计法计算直方图的不相似度,用最近邻准则进行分类。所提出的算法分别在ORL、FERET、YALE数据库中进行实验,分别取得了高达99.5%、92%、98.67%的识别率,与分块LBP算法相比识别率分别有2.5%、8%、2.67%的提高。实验结果表明,完备LBP提取的特征比较全面且具有较强的鉴别能力,在ORL、FERET、YALE人脸库中均能获得较好的识别率。     

改进的共轭梯度算法的图像重建算法

针对电容层析成像图像重建问题的病态性,在Tikhonov正则化的基础上,以正则化解决方案的规模和给定数据的质量为理论依据,引入一个数学变换,提出了一种新的正则化方法,该方法克服了常规正则化方法扰乱原系统的缺陷。同时,将ECT物理模型进行规范化,并对共轭梯度算法进行改进。仿真实验表明,改进的共轭梯度算法的成像质量高于LBP算法、 Tikhonov正则化算法和共轭梯度算法,并利用相关系数进行了验证。     

The Extended Column Test: Test effectiveness, spatial variability, and comparison with the Propagation Saw Test

The Extended Column Test (ECT) is a new stability test that aims to assess the fracture propagation potential across a 0.90 m wide isolated column. This paper: 1) describes the test procedure and presents new recording standards for the test, 2) uses two independent datasets (each consisting of over 300 tests) to assess the effectiveness of the test, 3) looks at the spatial variability of ECT results from several test grids, and 4) compares adjacent results between the ECT and the Propagation Saw Test (PST) on stable and unstable slopes. Our results indicate that the ECT is an effective stability test, with a false-stability rate less than other standard snow stability tests. Results are sometimes quite spatially uniform, though occasionally slopes may exhibit variable ECT results. In comparison to the PST, our data suggest that the ECT has a lower false-stability rate, but a higher false instability rate. Overall, the ECT is better at discriminating between stable and unstable slopes in our dataset. No test is perfect and all tests must be used in conjunction with additional data, but our results show that the ECT is valuable additional tool for assessing snow stability.     

The Extended Column Test: Test effectiveness,spatial variability,and comparison with the Propagation Saw Test

The Extended Column Test (ECT) is a new stability test that aims to assess the fracture propagation potential across a 0.90 m wide isolated column. This paper: 1) describes the test procedure and presents new recording standards for the test, 2) uses two independent datasets (each consisting of over 300 tests) to assess the effectiveness of the test, 3) looks at the spatial variability of ECT results from several test grids, and 4) compares adjacent results between the ECT and the Propagation Saw Test (PST) on stable and unstable slopes. Our results indicate that the ECT is an effective stability test, with a false-stability rate less than other standard snow stability tests. Results are sometimes quite spatially uniform, though occasionally slopes may exhibit variable ECT results. In comparison to the PST, our data suggest that the ECT has a lower false-stability rate, but a higher false instability rate. Overall, the ECT is better at discriminating between stable and unstable slopes in our dataset. No test is perfect and all tests must be used in conjunction with additional data, but our results show that the ECT is valuable additional tool for assessing snow stability.     

A new self-calibration method for electronic current transformers

Compared with traditional current transformers (CTs), electronic current transformers (ECT) have the following advantages: (1) no saturation problem, (2) wider measurement range, (3) smaller footprint, (4) lighter weight, and (5) easier for digitization. Hence, the ECT is one of the critical components in the development of intelligent substations. Since the majority of the sensing elements of ECTs are semiconductor materials, their accuracy and sensitivity are influenced by the ambient temperature. Moreover, the quiescent output voltage of the semiconductor-based ECT is also affected by the ambient temperature. This paper proposes a self-calibration method with the ability of quiescent-output-voltage compensation and sensitivity compensation. The proposed design can automatically adjust the quiescent output voltage and the sensitivity variation when the temperature changes. The experimental test results demonstrate that an ECT with the proposed self-calibration method can achieve Class 0.5 for measuring CTs and Class 5P20 for protective CTs.     

Imaging of two-dimensional unsaturated moisture flows in uncracked and cracked cement-based materials using electrical capacitance tomography

The development of visualizing tools to monitor unsaturated moisture flow in cement-based materials is of great importance, as most degradation processes in cement-based materials are connected to and take place in the presence moisture. This paper investigates the ability of electrical capacitance tomography (ECT) to image two-dimensional (2D) unsaturated moisture flow in cement-based materials. In ECT, the electrical permittivity distribution within an object is reconstructed based on measured capacitances between electrodes attached on the object’s surface. In a series of experiments, mortar specimens with and without discrete cracks were imaged with ECT during a 2D moisture ingress. The results show that ECT is able to monitor the evolution of the moisture flow, and to approximate the shape and position of the moisture front. These findings indicate that ECT is a viable method for monitoring and visualizing 2D unsaturated moisture flow in cement-based materials in the presence and absence of discrete cracks.     

Application of electrical capacitance tomography in particulate process measurement – A review

Particulate process measurement presents challenges because it often involves multiphase flow. Due to its advantages over other tomography modalities, electrical capacitance tomography (ECT) is widely applied in monitoring and measuring particulate processes. This paper presents a review on the application of ECT in particulate process measurement, including the monitoring of flow regime and solids distribution, solids flow velocity measurement, and fluidized bed dryers. The electrostatic phenomenon and the effect of electrostatics on the performance of ECT systems are also addressed. Finally, the challenges to ECT for particulate process measurement are given.