Computing a flattest, undercut-free parting line for a convex polyhedron, with application to mold design

A parting line for a polyhedron is a closed curve on its surface, which identifies the two halves of the polyhedron for which mold-boxes must be made. A parting line is undercut-free if the two halves that it generates do not contain facets that obstruct the de-molding of the polyhedron. Computing an undercut-free parting line that is as “flat” as possible is an important problem in mold design. In this paper, algorithms are presented to compute such a parting line for a convex polyhedron, based on different flatness criteria.     

Colloidal chemistry as a guide to design intended dispersions of carbon nanomaterials

In this review, some established concepts from Colloidal Science and their application to graphene and carbon nanotubes dispersions in organic or aqueous media are highlighted to rationalize alternatives for some issues in terms of colloidal properties. Recent applications for carbon-based dispersions are presented, as well as van der Waals interactions in carbon materials and strategies to overcome these interactions, such as increasing electrostatic repulsion between dispersed particles, surface functionalization, or adsorption of passivation agents such as macromolecules, which are the basis of many dispersion and exfoliation procedures. The demonstration of how knowledge and fine control of colloidal interactions have been used to overcome several limitations, such as the preparation of stable and concentrated dispersions of carbon materials and keeping appreciable electrical conductivity, is presented. It is also showed that the same knowledge can help the development of more environmentally friendly carbon-based colloids as well as the improvement of similar systems as dispersions of two-dimensional materials.     

A linear time algorithm to remove winding of a simple polygon

In this paper, we present a linear time algorithm to remove winding of a simple polygon P with respect to a given point q inside P. The algorithm removes winding by locating a subset of Jordan sequence that is in the proper order and uses only one stack.     

精密电压基准及应用

本文介绍了在ＵＪ５２多量限电位差计中用ＬＭ３９９代替锌汞电池的电路和方法。取得了较好的效果。     

提高直流复射式检流计内阻测量精度的措施

本文介绍了在电磁学实验中，就如何提高直流复射式检流计内阻测量精度所采用方法，本方法使内阻测量的平均相对误差最大可以减小达两个数量级以上。     

体吸收型激光能量计能量损失补偿方法的研究

借助传热学基本理论对体吸收型激光能量计因热辐射、热对流和热传导造成的热能损失进行了分析，在此基础上建立了能量计热能损失的数学模型。根据数学模型采用最小二乘法对测量数据进行了曲线拟合，得到与实际降温曲线非常接近的拟合曲线。利用拟合曲线对测量数据进行补偿修正后使得能量计的测量重复性得到了很大提高。该方法对于体吸收型激光能量计的研制具有一定的理论意义。     

基于文丘里管和涡轮流量计的液液两相流测量

本文研究了运用单相流量计组合进行液液两相流参数测量的方法.该方法首先通过静态混合器将液液两相流混合成为均相流,然后利用文丘里管获得两相流差压,利用涡轮流量计获得两相流总体积流量,最后通过液液两相流测量模型获得液液两相流总体积流量、总质量流量、混合密度以及分相流量.初步实验结果表明该方法是可行的,在总体积流量1～6 m3/h,油含率15%～85%的范围内,可有效地测量液液两相流的总体积流量、总质量流量和两相流混合密度,测量相对误差在5%以内,但液液两相流分相流量测量相对误差较大,仍需进一步研究.     

潜在视功能检测仪光学参数特性的研究与优化

针对潜在视功能检测仪临床使用中量程有限和对高度屈光不正患者检测结果有一定误差的现象，研究了其光学系统成像特性，建立了系统对视力板成像的视觉放大率公式，分析了准直透镜、成像透镜焦距变化对视觉放大率的影响。系统中视力板移动检测时，准直透镜焦距影响视觉放大率变化快慢，决定视觉放大率曲线的平缓程度；成像透镜焦距对视觉放大率产生整体影响，使视觉放大率曲线产生整体平移。找出了系统的理想参数，能使视觉放大率在整个视力板移动范围内保持不变，消除了检测过程中视力板放大率不同带来的检测误差。通过对各参数的数值分析，得到最优参数，系统检测量程从原来的－7D～＋12D扩大为－11D～＋15D。     

基于前向近红外散射光谱测量雾和雨天大气消光的应用研究

在可见和近红外区,由于大气的吸收作用忽略不计,大气消光由散射决定,主要贡献来自于雾滴、雨滴、其他形式降水和小粒子。基于前向近红外散射光谱的前向散射式能见度仪(FVM)采用近红外的LED光源照射到约100 mL的空气体积上,并测量前向30°～36°范围内的粒子的散射光强。由于该前向角范围内,雾滴和霾粒子的散射相函数不受粒子尺寸分布的影响,经过波长校正后,散射强度与大气消光系数成正比,该散射消光比通过对比标准人工观测值获得。然而,在把雾和霾的散射消光比应用到雨天测量时,会产生难以接受的误差。要得到雨天消光的准确测量,就需要找到适合雨滴的散射消光比。基于Mie散射理论计算了不同尺寸分布下的雾滴和雨滴的散射相函数,并对雾天和雨天下FVM的测量值与人工实际观测值进行了对比分析,发现FVM在雨天的消光要比人工观测值高出约20%～60%。根据测量结果,可以定出FVM在雨天测量的校准系数,因此,基于前向近红外散射光谱的FVM不仅能够测量雾天的大气消光,还能对雨天的消光进行较准确的估算