减少竹节布规律性竹节疵点的有效措施

将竹节纱分为周期性竹节纱和随机竹节纱.为减少规律性竹节疵点,周期性竹节纱应采取多个储纬器、设定无规律的引纬比例、延长竹节循环周期、两种竹节周期的筒纱同时使用等方法;对随机竹节纱则提出应完善竹节纱系统功能的建议.     

Statistical power of Fisher test for the detection of short periodic gene expression profiles

Many cellular processes exhibit periodic behaviors. Hence, one of the important tasks in gene expression data analysis is to detect subset of genes that exhibit cyclicity or periodicity in their gene expression time series profiles. Unfortunately, gene expression time series profiles are usually of very short length, with very few periods, irregularly sampled and are highly contaminated with noise. This makes the detection of periodic profiles a very challenging problem. Recently, a hypothesis testing method based on the Fisher g-statistic with correction for multiple testing has been proposed to detect periodic gene expression profiles. However, it was observed that the test is not reliable if the signal length is too short. In this paper, we performed extensive simulation study to investigate the statistical power of the test as a function of noise distribution, signal length, SNR, and the false discovery rate (FDR). We have found that the number of periodic profiles can be severely underestimated for short length signal. The findings indicate that caution needs to be exercised when interpreting the test result for very short length signals.     

Periodic variation of torque and its relations to interfacial sticking and slipping during friction stir welding

Abstract

The fraction of slipping between the tool and the workpiece during friction stir welding was calculated based on the measured torque and axial force with a sampling frequency of 1000 Hz. The results showed that the torque and fraction of slipping present a variation with the same periodicity that is equal to the time of one tool rotation. A model was proposed to present the average slipping fraction under different process parameters. The variation of the contact condition between the tool and the workpiece in one rotation was explained.     

Periodically Aligned Si Nanopillar Arrays as Efficient Antireflection Layers for Solar Cell Applications

Periodically aligned Si nanopillar (PASiNP) arrays were fabricated on Si substrate via a silver-catalyzed chemical etching process using the diameter-reduced polystyrene spheres as mask. The typical sub-wavelength structure of PASiNP arrays had excellent antireflection property with a low reflection loss of 2.84% for incident light within the wavelength range of 200–1,000 nm. The solar cell incorporated with the PASiNP arrays exhibited a power conversion efficiency (PCE) of ~9.24% with a short circuit current density (J _SC ) of ~29.5 mA/cm² without using any extra surface passivation technique. The high PCE of PASiNP array-based solar cell was attributed to the excellent antireflection property of the special periodical Si nanostructure.     

空间相机偏流角的周期性连续调整

为了减小偏流角对空间相机图像质量的影响,延长相机一次性有效连续摄像时间,提出了一种在相机摄像前的准备阶段,偏流角的周期性连续调整方法。首先,详细分析偏流角调整的需求,确定调整策略;然后,介绍了偏流角调整系统的构成及工作原理;最后,系统设计和实验验证。实验结果表明:单次调整误差≤40″,调整周期为512ms,摄像开始时偏流角≤56″,对图像MTF值的影响≤0.03%,一次性有效连续摄像时间最大可延长9.488s。有效减少了偏流角对图像质量的影响,延长了有效摄像时间,完全满足空间相机对偏流角的控制要求。     

金属晶体中原子堆积方式的周期性

本文试图从金属中原子的价电子周期性排布,以寻求成键金属原子的价电子构形与金属的三种堆积结构的周期性出现的内在联系。     

A new approach to the periodicity lemma on strings with holes

We first give an elementary proof of the periodicity lemma for strings containing one hole (variously called a “wild card”, a “don’t-care” or an “indeterminate letter” in the literature). The proof is modelled on Euclid’s algorithm for the greatest common divisor and is simpler than the original proof given in [J. Berstel, L. Boasson, Partial words and a theorem of Fine and Wilf, Theoret. Comput. Sci. 218 (1999) 135–141]. We then study the two-hole case, where our result agrees with the one given in [F. Blanchet-Sadri, Robert A. Hegstrom, Partial words and a theorem of Fine and Wilf revisited, Theoret. Comput. Sci. 270 (1-2) (2002) 401–419] but is more easily proved and enables us to identify a maximum-length prefix or suffix of the string to which the periodicity lemma does apply. Finally, we extend our result to three or more holes using elementary methods, and state a version of the periodicity lemma that applies to all strings with or without holes. We describe an algorithm that, given the locations of the holes in a string, computes maximum-length substrings to which the periodicity lemma applies, in time proportional to the number of holes. Our approach is quite different from that used by Blanchet-Sadri and Hegstrom, and also simpler.     

Finite state automata representing two-dimensional subshifts

A new type of two-dimensional automaton has been defined to recognize a class of two-dimensional shifts of finite type having the property that every admissible block found within the related local picture language can be extended to a point of the subshift. Here it is shown that this automaton accurately represents the image of the represented two-dimensional shift of finite type under a block code. It is then shown that these automata can be used to check for a certain type of two-dimensional transitivity in the factor language of the corresponding shift space and how this relates to periodicity in the two-dimensional case. The paper closes with a notion of “follower sets” that are used to reduce the size of the automata representing two-dimensional sofic shifts.     

Periodic properties of user mobility and access-point popularity

Understanding user mobility and its effect on access points (APs) is important in designing location-aware systems and wireless networks. Although various studies of wireless networks have provided useful insights, it is hard to apply them to other situations. Here we present a general methodology for extracting mobility information from wireless network traces, and for classifying mobile users and APs. We used the Fourier transform to reveal important periods and chose the two strongest periods to serve as parameters to a classification system based on Bayes’ theory. Analysis of 1-month traces shows that while a daily pattern is common among both users and APs, a weekly pattern is common only for APs. Analysis of 1-year traces revealed that both user mobility and AP popularity depend on the academic calendar. By plotting the classes of APs on our campus map, we discovered that their periodic behavior depends on their proximity to other APs.

汽车用薄板的表面形貌的分形研究

本文将分形理论用于薄板表面形貌的研究上,提出了分形维数反映了表面形貌的规律性的观点。利用触针轮廓仪和数据采集系统对几种不同的毛化薄板的三维形貌进行了测量,计算了这些薄板的分形维数,并对这些薄板的表面形貌的规律性进行了讨论。