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.

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.

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.

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 1 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.

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,m,n,mn}.

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.

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.

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.

浮动滚子推杆盘形凸轮机构的传动性能评价与第Ⅰ类尺寸综合问题

以德国某高速印刷机送纸机构为研究对象,提出“功率传动节点”和“泛压力角”新概念,得到送纸机构存在“第一、第二功率传动节点”和“第一、第二泛压力角α_(1)和α_(2)”的结论。通过“释放滚子中心C”提出浮动滚子推杆盘形凸轮机构的一般型及其第Ⅰ类尺寸综合问题的科学准确描述,揭示关键构件的受力汇交特征,提出“瞬时/整程满足第二泛压力角α_(2)≤[α_(2)]条件”特别是“瞬时/整程满足第一、第二泛压力角α_(1)≤[α_(1)]∩α_(2)≤[α_(2)]条件”滚子中心的求解原理、路径和机构最小尺寸的求解方法,较为圆满解决了浮动滚子推杆盘形凸轮机构的传动性能评价与第Ⅰ类尺寸综合问题,并用算例进行了验证。

学校效率、教师权益与班级规模的博弈——20世纪美国小班化改革前史

本文考察美国小班化改革潮流兴起之前影响学校班级规模的多方面因素。文章聚焦20世纪20年代和60年代不同利益群体试图改变班级规模的斗争历程。在20年代,高举效率大旗的城市督学在学校经费紧张的情况下,利用班级规模研究的“科学依据”,突破外部机构设定的班级规模上限。在60年代,深受工作条件困扰的教师群体通过教师工会与集体谈判,将班级规模上限写入教师聘用合同,以求缩减班级规模。两组围绕班级规模的博弈揭示了美国学校历史中复杂的权力与利益纠葛,有助于进一步理解过往与当今时代小班化改革所面临的种种冲突。

基于SEIADR模型研究口罩对COVID-19传播的影响

为了模拟COVID-19流行病的传播,将无症状感染者引入SEIDR模型中,提出了一个改进的SEIADR模型来分析戴口罩对COVID-19流行病最终规模和基本再生数的影响。为了研究口罩对新冠肺炎传播的影响,将人群分为两组:一组戴口罩(包括易感者、暴露者、有症状感染者、无症状感染者、死亡人群和康复人群);另一组不戴口罩(包括易感者、暴露者、有症状感染者、无症状感染者、死亡人群和康复人群)。运用分组动力学模型确定了流行病的基本再生数和控制再生数;从生物学意义对再生数进行了解释,并根据文献中的相关数据模拟了疾病的最终规模;最后通过数值分析模拟了戴口罩对流行病传播过程中的动态影响。数据模拟表明,如果所有人不戴口罩,那么控制再生数为1.35;如果50%的人戴口罩,口罩的易感性和传染性降低50%,那么控制再生数会下降到0.39,而病例最终规模也将从73.20%降到16.15%。

中型邮轮A级分隔简化策略及其应用

邮轮概率法破损稳性评估方法中要求计入A级防火分隔带来的进水中间阶段的影响。然而实际工程实践中发现,中型邮轮布置中存在大量A级分隔(如A级舱壁、甲板等),如果以遍历的方式考察计算这些A级边界,则会导致生成的破损工况数量过多,超出常规计算机的计算能力,无法顺利得到计算结果。以某中型邮轮实船为例,给出A级分隔的简化处理策略,并通过对比计算验证该组策略的合理性,旨在为邮轮设计者提供一种高效的设计参考方法。

小班化背景下学生养成教育的实施策略刍论

在立德树人教育背景下,实现个别化教育,组织开展小班化教学活动,对于学生的健康成长和全面发展有着深刻的意义。教师在养成教育过程中实施小班化教学,可以使学生在接受养成教育的过程中主体性得到关注,综合素质得到全面提升,进而逐渐养成良好的行为习惯、学习习惯、道德品质,形成知情意行良好统一。文章从小班化教学的含义和特点入手,指出小班化背景下实施养成教育的意义,并对小班化背景下学生养成教育的实施策略进行探究。

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。