Meta-analysis of potentially confounding effect of class size on associations between object-oriented metrics and maintainability

This paper uses three size metrics,which are collectable during the design phase,to analyze the potentially confounding effect of class size on the associations between object-oriented（OO）metrics and maintainability.To draw as many general conclusions as possible,the confounding effect of class size is analyzed on 127 C＋＋ systems and 113 Java systems.For each OO metric,the indirect effect that represents the distortion of the association caused by class size and its variance for individual systems is first computed.Then,a statistical meta-analysis technique is used to compute the average indirect effect over all the systems and to determine if it is significantly different from zero.The experimental results show that the confounding effects of class size on the associations between OO metrics and maintainability generally exist,regardless of whatever size metric is used.Therefore,empirical studies validating OO metrics on maintainability should consider class size as a confounding variable.

With Respect to Academic Achievement, How Important is Class Size?

This essay will discuss how important the influence of class size is on academic achievement.

On the Normal Subgroup with Exactly Two G-Conjugacy Class Sizes

Let G be a finite group with a non-central Sylow r-subgroup R, Z（G） the center of G, and N a normal subgroup of G. The purpose of this paper is to determine the structure of N under the hypotheses that N contains R and the G-conjugacy class size of every element of N is either i or m. Particularly, it is shown that N is Abelian if N ∩ Z（G）=1 and the G-conjugacy class size of every element of N is either 1 or m.

A Result on Character Degrees and Conjugacy Class Sizes in Finite Groups

Let G be a finite group and π be a set of primes including at least two elements. We write cd（G） and cs（G） to denote the set of complex irreducible character degrees and conjugacy class sizes of G , respectively, and write π（m）to denote the set of all prime divisors of a positive integer m . For any 1≠m∈cd（G） and 1≠m∈cs（G）, in this note, we shall present the corresponding group structures of finite group G in the case π（m）=π , respectively, which generalizes the result of finite groups with character degrees of two distinct primes. Furthermore, we shall see that the influence of the two sets on the group structure is analogous.

On conjugacy class sizes of primary and biprimary elements of a finite group

Let m, n 〉 1 be two coprime integers. In this paper, we prove that a finite solvable group is nilpotent if the set of the conjugacy class sizes of its primary and biprimary elements is {1, rn, n, mn}.

Small Class Size Boosts Test Scores Later

Smaller class sizes in early grades translated into students scoring higher on math tests in later grades in Tennessee’s experiment to see if smaller classes improved education, a study said on Friday. 低年级的小型班级能够使学生在高年级时获得数学测试的高分。田纳西州的一项旨在了解小型班级是否能够改进教育的实验得出如此结论。一项研究周五如是说。

Phytoplankton size class derived from phytoplankton absorption and chlorophyll-a concentrations in the northern South China Sea

A previously developed model was modified to derive three phytoplankton size classes (micro-, nano-, and pico-phytoplankton) from the overall chlorophyll-a concentration, assuming that each class has a specific absorption coefficient. The modified model performed well using in-situ data from the northern South China Sea, and the results were reliable and accurate. The relative errors of the size-fractioned chlorophyll-a concentration for each size class were: micro-:21%, nano-:41%, pico-:26%, and nano+pico:23%. The model was then applied on ocean color remote sensing data to examine the distribution and variation of phytoplankton size classes in northern South China Sea on a large scale.

Comparison of two classification methods to identify grain size fractions of aeolian sediment

Grain-size class-Std(GSCStd) and Grain-size class-dD(GSCdD) methods are simple statistical approaches for classifying bulk grain-size distributions(GSDs) into grain-size fractions. Although these two methods were developed based on similar statistical principles, the classification difference between these two methods has not been analyzed. In this study, GSCStd and GSCdD methods are conducted in thirteen grain-size data sequences to examine the applicability for identifying grain size fractions. Results show that, application of the GSCStd method is equivalent to that of the GSCdD method in identifying finer grain-size fractions, and the difference between the two methods mainly comes from the identification of coarse grain-size fractions. Thus, finer grain-size fractions are recommended for use in research of surface aeolian and paleo-aeolian sediments. In addition, our results do not completely agree with previous studies, coarser grain-size fractions in our case suggest that the GSCdD method may not be more applicable than the GSCStd method.

Problems and Countermeasures of Colloquial English Large Size Class Teaching of Higher Vocational Public English under the Constructivism Theory

Based on the theory of constructivism, this article analyzes the open problems colloquial English large size class teaching of higher vocational public English and points out the countermeasures of colloquial English large-scale class teaching of higher vocational public English.

Practice and Thoughts on due Statistics for Four Classes of Enterprises Above Designated Size

“Four classes of enterprises above designated size”(hereinafter called four-classes enterprises)refer to objects of statistical survey that have reached a certain scale in China’s current statistical method system,including four classes in national economy,namely,industrial enterprises above designated size,construction and real estate development and management enterprises above qualifications,wholesale and retail,catering and accommodation enterprises,and service enterprises above designated size,which are the primary part of national economic and social development activities.This paper is focused on analyzing the practice and difficulties in the current statistics work of four-classes enterprises,and then this paper proposes some recommendations.

An Improved Algorithm for Imbalanced Data and Small Sample Size Classification

Traditional classification algorithms perform not very well on imbalanced data sets and small sample size. To deal with the problem, a novel method is proposed to change the class distribution through adding virtual samples, which are generated by the windowed regression over-sampling (WRO) method. The proposed method WRO not only reflects the additive effects but also reflects the multiplicative effect between samples. A comparative study between the proposed method and other over-sampling methods such as synthetic minority over-sampling technique (SMOTE) and borderline over-sampling (BOS) on UCI datasets and Fourier transform infrared spectroscopy (FTIR) data set is provided. Experimental results show that the WRO method can achieve better performance than other methods.

A bio-optical inversion model to retrieve absorption contributions and phytoplankton size structure from total minus water spectral absorption using genetic algorithm

We propose a bio-optical inversion model that retrieves the absorption contributions of phytoplankton and colored detrital matter(CDM),as well as the phytoplankton size classes(PSCs),from total minus water absorption spectra.The model is based on three-component separation of phytoplankton size structure and a genetic algorithm.The model performance was tested on two independent datasets(the NASA bio-Optical Marine Algorithm Dataset(NOMAD) and the northern South China Sea(NSCS) dataset).The relationships between the estimated and measured values were strongly linear,especially for aCDM(412),and the Root Mean Square Error(RMSE) of the CDM exponential slope(SCDM) was relatively low.Next,the inversion model was directly applied to in-situ total minus water absorption spectra determined by an underwater meter during a cruise in September 2008,to retrieve the phytoplankton size structure in the seawater.By comparing the measured and retrieved chlorophyll a concentrations,we demonstrated that total and size-specific chlorophyll a concentrations could be retrieved by the model with relatively high accuracy.Finally,we applied the bio-optical inversion model to investigate changes in phytoplankton size structure induced by an anti-cyclonic eddy in the NSCS.

Zooplankton community size-structure change and mesh size selection under the thermal stress caused by a power plant in a semi-enclosed bay

Zooplankton samples were collected using 505, 160 and 77 μm mesh nets around a power plant during four seasons in 2011. We measured total length of zooplankton and divided zooplankton into seven size classes in order to explore how zooplankton community size-structure might be altered by thermal discharge from power plant. The total length of zooplankton varied from 93.7 to 40 074.7 μm. The spatial distribution of mesozooplankton(200-2 000 μm) populations were rarely affected by thermal discharge, while macro-(2 000-10 000 μm)and megalo-zooplankton(>10 000 μm) had an obvious tendency to migrate away from the outfall of power plant.Thus, zooplankton community tended to become smaller and biodiversity reduced close to power plant.Moreover, we compared the zooplankton communities in three different mesh size nets. Species richness,abundance, evenness index and Shannon-Wiener diversity index of the 505 μm mesh size were significantly lower than those recorded from the 160 and 77 μm mesh size. Average zooplankton abundance was highest in the 77 μm mesh net((27 690.0±1 633.7) ind./m^3), followed by 160 μm mesh net((9 531.1±1 079.5) ind./m^3), and lowest in 505 μm mesh net((494.4±104.7) ind./m^3). The ANOSIM and SIMPER tests confirmed that these differences were mainly due to small zooplankton and early developmental stages of zooplankton. It is the first time to use the 77 μm mesh net to sample zooplankton in such an environment. The 77 μm mesh net had the overwhelming abundance of the copepod genus Oithona, as an order of magnitude greater than recorded for 160 μm mesh net and 100% loss through the 505 μm mesh net. These results indicate that the use of a small or even multiple sampling net is necessary to accurately quantify entire zooplankton community around coastal power plant.

Diversity and Structure of Miombo Woodlands in Mozambique Using a Range of Sampling Sizes

Forest assessments are essential to understand the tree population structure and diversity status of forests and to provide information for biodiversity recovery planning. Unfortunately, the majority of Miombo woodlands in Mozambique lack of inventory data, and consequently are often insufficient for management. This study aimed to assess the species richness, diversity and structure of Miombo woodlands using a range of sampling sizes in Mocuba district, Mozambique. Plant inventory was carried out in 128 systematically selected sample plots in 71.6 ha, which was divided into eight treatments, i.e., TI： 0.1 ha; T2：0.25 ha; T3：0.375 ha; T4：0.5 ha; T5：0.625 ha; T6：0.75 ha; T7：0.875 ha; T8：1.0 ha, with 16 repetitions. All stems _〉 10 cm diameter at breast height, and species name to evaluate the floristic composition, richness of tree species, diversity and diameter distribution were recorded. A total of 36,535 individuals were recorded, belonging 124 species, 83 genera and representing 31 botanical families. The most important species was the Brachystegia spiciformis Benth. and the richest botanical family was Fabaceae. The forest showed an average of 517 ＋ 85 trees/ha, and high species diversity and evenness. Analysis of covariance shows that the intercepts and slope of exponential function for diameter distribution are not significantly different for the eight treatments. Compared with the entire composite forest, inventory means were accurately estimated and size class distributions were well represented for plots 〈 0.25 ha, for selecting an efficient sampling design suited to forest characteristics and the inventory＇s purpose.

Quantitative Analysis of the Sized Ranged Plastic Debris on Beach Shoreline along the Limbe Coastline, Cameroon

In recent years, increased interest in investigating the accumulation of sized ranged plastic debris has been observed on beaches along coastlines. The abundance and distribution of the 4M’s sized class plastic debris were quantitatively assessed on five sandy beaches, in Cameroon. Duplicates of 2 × 2 m (4 m2) quadrants were sampled in each beach/month with a total of 80 quadrants. Collected plastic samples were washed, sieved and dried. Particles of size, ≥2 mm, were sorted and measured using a 30 cm ruler, and converted to mm. Overall, 12,822 particles by number (530.59 g) with a mean abundance of 40.07 items/m2 (1.66 g/m2) plastic debris was recorded. ANOVA (p = 0.05) shows a linear relationship between the meso- and micro-sized classes with significantly higher abundance recorded in LDB sites. The highest abundance by weight was recorded in August and June numerically. 80% of the plastic particles were between the size range, of 5 - 20 mm by number and 6 - 100 mm by weight. Moreover, in all beaches micro-sized class plastics were dominated by number 42.40% with fragmented debris dominant, in number/weight, 54.86% (25.69%) while meso-sized class plastics were 29.28% dominated by weight, with fragmented debris type, the most prevalence in number and weight as 46.11% (26.18%). On average, color and shape fractions revealed, colored and irregularly shaped plastics were dominant with an abundance of 80.45 ± 18.17 items/m2 (2.58 ± 0.68 g/m2) and 47.24 ± 20.40 items/m2 (1.39 ± 0.66 g/m2). Finally, the 0.0001 g plastic debris was dominant with a concentration, of 33.68 ± 7.23 items/m2. The intense use of beaches for recreation and poor waste disposal has increased the potential for plastic contamination.

湖北南河国家级自然保护区及周边七子花群落特征与种群结构

七子花(Heptacodium miconioides Rehder)为我国特有的落叶灌木或小乔木,被列入国家重点保护野生植物名录和世界自然保护联盟(IUCN)受威胁植物名录。2022年8月,被认为在湖北消失115年的七子花,在谷城南河国家级自然保护区及其周边被重新发现。本研究以新发现的3个七子花种群(傅家寨、玉皇阁和李庙镇)为研究对象,分析其生境特征、伴生群落物种组成、种群结构和受威胁因素。分布区的植被为典型的落叶阔叶林,以小叶鹅耳枥(Carpinus stipulata H.J.P.Winkl.)、化香树(Platycarya strobilacea Siebold&Zucc.)、七子花和栓皮栎(Quercus variabilis Blume)为优势种。新发现种群共记录到151株七子花,基本都分布于海拔1000~1300 m的山脊或崖壁上。七子花的大小级结构图呈纺锤型,表明新发现种群为衰退型,实生苗更新不足。新发现的151株个体中有137株(91%)产生萌蘖,共产生936个萌蘖,平均每株6.83个。大量的萌蘖在很大程度上弥补了幼苗的不足,使该物种能够占领其生态位,利于种群的维持。新发现种群位于偏远山区的山脊和崖壁上,人为干扰较小,因此可以推测内因是其种群衰退的主要驱动力。建议对周边区域开展更大规模的调查,同时采用包括就地保护、人工扩繁、迁地保护和野外回归在内的整合保护计划加强对七子花的保护和可持续利用。

神农架南坡小叶青冈+曼青冈常绿阔叶林物种组成与群落结构

本研究在神农架南坡建立1 hm2的常绿阔叶林动态监测固定样地,分析了该群落的物种组成、区系特征、垂直结构、径级结构和空间分布格局。结果显示,群落物种丰富,共调查到维管植物216种,隶属78科154属,其中胸径≥1 cm的木本植物38科69属107种。区系成分中,热带分布的科、属分别占总科、属数的50.00%和40.58%;温带分布的科、属分别占总科、属数的34.21%和53.63%。常绿树种占比55.14%(59种),落叶树种占比44.86%(48种),其中常绿树种的多度、胸高断面积和重要值占比分别为82.23%、64.79%和73.03%。偶见种占比33.64%(36种),稀有种占比8.41%(9种)。群落垂直结构明显,可分为乔木层、灌木层和草本层,各个层次物种丰富。径级结构呈倒“J”型,属于增长型群落。优势种的空间分布呈现出不同程度的聚集分布。研究表明,该群落的常绿树种重要值明显高于落叶树种,属于小叶青冈(Cyclobalanopsis myrsinifolia Blume)+曼青冈(Cyclobalanopsis oxyodon Miq.)群系,是该区域代表性的常绿阔叶林。区系成分体现出神农架作为中亚热带和北亚热带分界线的特征。群落有着较好的更新能力,呈现向常绿阔叶林顶极群落演替的趋势。

鱼类最佳体长频率分析组距研究

随着计算机技术的发展,近几年以鱼类体长频率为基础估算鱼类生物学特征值的体长频率分析法迅速被广泛应用,而确定体长分组组距是开展鱼类体长频率分析的必要步骤,但往往不被重视,常被随意采用为1mm、5mm或10mm等。为了尽量减少误差,本研究根据1997年12月至1998年12月在珠江口水域尖尾罟网和掺缯网周年月度渔业资源调查中康氏小公鱼(Stolephorus commersoni)和棘头梅童鱼(Collichthys lucidus)的生物学测定资料,分别以不同的体长分组组距重构体长频率组成数据,采用FAO推出基于ELEFAN技术的FiSATⅡ软件估算渐近体长L∞和生长系数K值,进一步估算鱼类资源开发参数(Z,M,F,E),分析以不同体长分组组距为基础估算结果的差异。结果表明,以相差较大的不同分组组距重构体长频率组成数据来估算渐近体长L∞、生长系数K和资源开发参数均有明显的差异,建议以体长全距、体长标准差和样品数量等影响因素来共同确定某种鱼类的体长分组组距,从而提高估算结果的可信度,以达到定量分析鱼类生物学特征值的目的。

外语专业教学加大班型的可行性研究

长期以来,外语专业基础课多以小班进行.随着高校招生数量的剧增,外语专业大班教学已经存在.根据外语专业多年来小班教学和近年加大班型教学获得的数据,本文从多角度研究了班型大小对教学效果的影响.研究结果表明:班型大小与听、读、写的教学效果没有必然的联系,影响教学效果的重要因素不是班型大小,而是班型大小以外的因素.遥当加大班型进行教学是可行的.

适用于不平衡样本数据处理的支持向量机方法

支持向量机算法在处理不平衡样本数据时,其分类器预测具有倾向性.样本数量多的类别,其分类误差小,而样本数量少的类别,其分类误差大.本文针对这种倾向性问题,在分析其产生原因的基础上,提出了基于遗传交叉运算的改进方法.对于小类别训练样本,利用交叉运算产生新的样本,从而补偿了因训练数据类别大小差异而造成的影响.基于UCI标准数据集的仿真实验结果表明,改进方法比标准支持向量机方法具有更好的分类准确率.