有限域上一种新的求逆电路

求逆运算在编码理论和密码学中有着广泛的应用,因此设计简洁高效的求逆电路具有重要的现实意义。基于线性反馈移位寄存器和逻辑门,采用比特串行搜索方法,设计了一种新的应用于有限域上的求逆电路。该电路与用ROM查表法或纯组合逻辑电路实现求逆相比可节省芯片资源,且易于实现,具有广阔的应用前景。     

Variation in rubber chemistry and dynamic mechanical properties of the milking liner barrel with age

The milking liner is the interface between the milking machine and the cow. Liner properties important to milking performance were investigated for liners of different ages using discriminating tests rather than the normal, rubber-industry quality control-based tests. Large variations in the liner mechanical properties occurred depending on where the sample was taken; stiffness increased 4-fold 40 to 50 mm below the top of the liner. This was related to changes in the chemistry of the rubber created by absorption of milk-derived products (MDP) into the rubber and losses of formulation components, particularly 50% of the plasticizer and all of the antidegradent 40 to 50 mm below the top of the liner, with age and use. The presence of MDP leads to calcium and phosphate deposits on the inner surface of the liner barrel where the MDP was absorbed. The detailed liner properties can be used to explain the forces on the cow's teat and its reactions and effects on milk flow behavior, and to guide future liner development.     

自适应调频声衬及其控制系统设计

为克服现有声衬结构固定、敏感频率无法调节的弊端,提出了一种逆压电效应的调频式声衬结构。该声衬由颈部、共振腔以及压电膜片组成亥姆霍兹共振器。采用有限元法对声衬结构的固有频率、声场分布进行了计算,研究了压电膜片变形与共振频率偏移的关系。在阻抗管内对压电声衬致动前后系统的传递损失进行了对比,系统传递损失峰值频率与驱动电压呈线性关系,灵敏度为0.1Hz/V。在建立控制电压-驱动电压-噪声频率的对应关系的基础上,提出了一种基于光敏电阻的直流升压电路,采用LabVIEW软件编制了压电声衬的自适应控制程序,当噪声频率从746变化至788Hz时,驱动电压由110V自动升高至420V,声衬始终工作于共振状态,实现了宽频噪声的自适应控制。     

Numerical study of mixed convection nanofluid in an annulus enclosure between outer rotating cylinder and inner corrugation cylinder

Numerical investigations are presented for mixed convection problems in a concentric inner sinusoidal cylinder and an outer rotating circular cylinder, which were kept at constant hot and cold temperatures, respectively. The free space between the cylinders and the enclosure walls was filled with a water‐Cu nanofluid. The governing equations are formulated for velocity, pressure, and temperature formulation and are modeled in COMSOL5.2a, a partial differential equation solver based on the Galerkin finite element method. The governing parameters considered are the solid volume fraction, [0, 0.02, 0.04, and 0.06], Re (1, 25, 100, 200, and 300), and Ra (less than 10⁴), and the inner cylinder corrugation frequencies varied from (N = 3, 6, and 9). According to the calculations, the Reynolds number, the Rayleigh number, the nanoparticle volume fraction, and the number of corrugations play an important role of forming the stream and isothermal lines, the local and the average Nusselt number inside the annulus enclosure. The average Nusselt number decreases with increasing Reynolds number and the number of corrugations, while it increases as the Rayleigh number and the volume fraction increase.     

Natural convection heat transfer from a horizontal cylinder using holographic interferometry

The natural convection heat transfer from a horizontal cylinder with a uniform wall temperature in an infinite space was experimentally investigated. Infinite fringe interferograms of the cylinder heated from 295.15 to 355.15 K were recorded using the holographic interferometry technique. The temperature field around the cylinder was reconstructed based on phase difference recovery using a MATLAB code. The distributions of the local and average Nusselt numbers over the cylinder were then obtained. A correlation of the average Nusselt number was proposed for a Rayleigh number range of 2.7–6.0 × 10⁴. The experimental results are in good agreement with previous correlations, with a deviation of ±10%. The holographic interferometry technique was found to be satisfactory and reliable for heat transfer analyses.     

660MW超临界汽轮机闷缸技术及应用

介绍了潍坊发电厂660MW超临界汽轮机闷缸试验过程,通过可靠的安全保证措施可以确保在盘车停止的情况下汽缸均匀冷却,不出现上下缸温差过大、轴承超温等不利现象。指出了闷缸过程中需要注意的事项,取得的技术经验可为同类型机组提供借鉴。     

大型核电机组半速汽轮机长叶片系列的研发

大型低压焊接转子技术及半速低压长叶片是低参数大型化核电汽轮机开发的2个技术关键。文章着重介绍了上海汽轮机厂开发半速长叶片的技术路线：采用先进的ILB长叶片设计体系以及转速模化原理,得到与现有全速700～910mm叶片相同热力和强度振动特性的1450～1820mm半速系列长叶片;进一步对模化放大后叶片型线的精细优化设计及最终的全尺寸动振动试验,可充分保证高效率和高安全可靠性。所开发的半速长叶片系列将满足不同冷却水温1100～1850MW核电汽轮机的要求。     

南海高温高压气田尾管回接管柱改进及入井质量控制

南海西部海域高温高压条件苛刻,气井开发将准177.8 mm尾管回接至井口并全井段封固作为井筒完整性保障的技术措施之一。由于常规回接工具插入回接筒困难、密封能力有限,不能满足高温高压气井的要求,同时回接尾管材质软,采用特殊螺纹设计,入井质量要求高,因此优化改进了尾管回接工具及管柱结构,包括节流带孔碰压浮箍、4道密封件以及顶部封隔器+防上顶卡瓦的设计;开展了特殊螺纹上扣准确度控制技术研究,基于螺纹密封脂的摩擦因数修正了套管上扣扭矩计算公式,总结了上扣曲线可接受度的关键判断方法,提出了上卸扣速度精细化调整建议。上述工具和技术在6口高温高压开发井进行了应用,尾管回接作业提效20%,并有效提高了套管入井质量和井筒完整性。     

二氧化碳压缩机高压缸振动异常案例分析

某二氧化碳压缩机组,运行期间高压缸振动大,本文针对此问题进行排查,制定解决方案,验证解决效果,最终形成一套完整的案例分析。     

提花机电子花筒的设计与实现

为了节省提花布料制造成本,缩短织造新品种新花型的周期,提高生产率,提出利用电磁铁吸合的工作原理。由控制系统控制横针的进出。来替代机械花简和纹板。设计研究出电子花筒。同时对热量的起源。散热的最佳效果等方面进行分析。实施了减少热量提高散热效果等一系列措施,解决了电子花筒普遍存在的关键问题——散热问题。使产品的稳定性大大提高。图3参7