工作面跨采对深部掘进巷道的影响分析

在2423断东工作面跨巷道开采期间,通过对-1100一采轨道大巷的矿压观测数据的整理与分析,为巷道超前加固支护提供可靠的矿压数据和理论依据。     

张集矿1212(3)综放工作面矿压显现特征分析

通过对张集矿1212（3）综放工作面矿压观测分析，得出综采放顶煤开采的采场矿压显现特征，综合评价其支架的适应性与工作状态，为类似条件下的综采放顶煤及现场管理提供依据。     

倾斜煤层采场矿压显现规律研究

大倾角煤层开采时矿压显现特征具有许多不同于缓倾斜煤层开采的特征;利用数值模拟的方法,以山西某矿1025工作面为工程背景,研究了大倾角工作面开采时上覆岩层的运移特征,并进行了现场观测,分析工作面来压特征,确定了初次来压及周期来压步距及来压时的动载系数,为类似条件下的工作面顺利开采提供一定的借鉴意义。     

煤巷锚杆受相邻采面矿压影响分析

本文通过全过程、全方位的跟踪矿压观测，采取数据统计分析方法，对动压煤巷锚杆支护在成巷期间受相邻采面影响时的矿压关系进行分析，提出了类似条件下锚杆科学支护的依据。     

预防综放面坚硬顶板超前剪切破坏方法

综放面开采过程中,坚硬顶板超前剪切破坏,会造成工作面台阶下沉,甚至工作面整体垮落.通过矿压观测,判断顶板来压方式,采取强制放顶,防止顶板剪切破坏.     

运输石门上覆保护煤柱的开采技术与实践分析

文章介绍了在盘区运输石门上覆近层间距煤层的工作面布置方法及开采技术,同时对开车期间的矿压显现、周期来压强度、步距进行观测和总结分析。通过对下伏865轨道及皮带运输石门采用U29拱型棚和单体柱的加强支护,实现了安全开采,为类似条件下安全开采大巷上覆煤柱提供借鉴经验和科学依据,为提高老矿煤炭资源回收率,延长矿井服务年限拓宽了思路,提供了新的方法。     

张集煤矿综采工作面缩小防水煤柱试采

通过对张集矿井西翼地质构造、水文地质条件、13—1煤层赋存条件及其顶底板岩性组合、水裂隙发育规律及矿压显现规律的研究，在1212(3)、1215(3)面把防水煤柱缩小到60m，并采用综放、一次采全高的开采方式进行试验性开采，取得了成功。     

锚索网在煤巷支护中的应用

锚索网支护是一项新兴的煤巷支护新技术新工艺。它是运用锚索网支护悬吊理论、围岩加固理论以及组合梁理论，结合工程设计施工中有关顶板离层、表面位移、锚固力等矿压观测数据，及时对不同岩性岩层调整相应的支护参数，从而达到对巷道进行合理支护。     

采矿专业学生之矿压能力互馈核心单元的研究

采矿学生是煤炭高校的特色组成,矿压能力是煤矿开采的生存技能。从采矿学生的内涵和矿压能力的演化入手,将矿压课程分为五个核心单元,并从五个衡量层面进行分析。     

不同基岩厚度综放上限开采矿压显现规律

文章研究了不同基岩厚度上限开采综放采场矿压显现规律,确定了合理的综放工作面开采上限,将基岩厚度降低到最小33 m,通过限厚开采,确保了水体下综放开采条件煤炭资源的安全回收,从而最大限度地提高了资源回收率,减少了煤炭资源损失,对煤炭资源的安全高效开采具有重要的理论价值和现实意义。     

Statistical estimates of learners�� judgments about knowledge in calibration of achievement

In theoretical models of self-regulated learning, calibration is one important component in successful learning. Two issues of calibration are explored. First, Nelson (1987) suggested the G (gamma) coefficient is the most appropriate measure of calibration (judgment accuracy) and rejected signal detection theory’s d′ statistic because data commonly challenge distributional assumptions. We empirically examined this issue, comparing G and d′. Second, we examined whether a learner’s calibration varies across three domains of knowledge: general, word, and mathematics. A sample of 266 university students volunteered to participate in the study. Participants were selected from various undergraduate and graduate courses. Participants first answered demographic items. Then they completed three knowledge tests (general, word, and mathematics) and judged correctness for each answer provided. Order of domains was randomly counterbalanced among participants. Results show that d′ is a valid measure of calibration, that assumptions about underlying distributions can be tested, and that preliminary evidence suggests that d′ may be a superior measure of accuracy compared to G. Finally, calibration varied by domain.     

A simple method for chiral resolution of 1,1′-Bl-2-naphthol

An improved method for preparing enantiomerically pure 1,1′-bi-2-naphthols is described. 1,1′-bi-2-naphthol boric anhydride was generated from the reaction of racemic 1,1′-bi-2-naphthol and boric anhydride. Its two diastereoisomers, could be efficiently separated in THF using (L)-proline as the resolving agent. Treatment in three successive steps yielded 79% and 74% enantiomerically pure (S)-and (R)-1,1′-bi-2-naphthol respectively.     

INVESTIGATING A POSSIBLE GAP BETWEEN STUDENTS’ EXPECTATIONS AND PERCEPTIONS: THE CASE OF A PRE-ENTRY SCIENCE PROGRAM

This study investigated a gap that may have existed between students’ expectations and perceptions of the 2007 Pre-Entry Science Program (PESP) cohort at the National University of Lesotho and factors that might have influenced these expectations and perceptions. Questionnaires and semi-structured interviews were used for data collection and administered to students participating in PESP. The gaps between expectations and perceptions that existed were measured using Cohen′s effect size. A large effect size was found for the ability of presenters to give students a good grasp of concepts within the subject area. Factors that seem to have influenced the students′ expectations and perceptions were identified as students′ background knowledge, previous experience, informal communication, and individual needs. Suggestions made to narrow the gap include knowing students′ expectations at the beginning of the program and then making a conscious effort to meet them.     

The estimation of the IRT reliability coefficient and its lower and upper bounds, with comparisons to CTT reliability statistics

The primary purpose of this study is to investigate the mathematical characteristics of the test reliability coefficient ρ _XX′ as a function of item response theory (IRT) parameters and present the lower and upper bounds of the coefficient. Another purpose is to examine relative performances of the IRT reliability statistics and two classical test theory (CTT) reliability statistics (Cronbach’s alpha and Feldt–Gilmer congeneric coefficients) under various testing conditions that result from manipulating large-scale real data. For the first purpose, two alternative ways of exactly quantifying ρ _XX′ are compared in terms of computational efficiency and statistical usefulness. In addition, the lower and upper bounds for ρ _XX′ are presented in line with the assumptions of essential tau-equivalence and congeneric similarity, respectively. Empirical studies conducted for the second purpose showed across all testing conditions that (1) the IRT reliability coefficient was higher than the CTT reliability statistics; (2) the IRT reliability coefficient was closer to the Feldt–Gilmer coefficient than to the Cronbach’s alpha coefficient; and (3) the alpha coefficient was close to the lower bound of IRT reliability. Some advantages of the IRT approach to estimating test-score reliability over the CTT approaches are discussed in the end.     

Splicing-site recognition of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) DNA sequences by support vector machines

Motivation: It was found that high accuracy splicing-site recognition of rice (Oryza sativa L.) DNA sequence is especially difficult. We described a new method for the splicing-site recognition of rice DNA sequences. Method: Based on the intron in eukaryotic organisms conforming to the principle of GT-AG, we used support vector machines (SVM) to predict the splicing sites. By machine learning, we built a model and used it to test the effect of the test data set of true and pseudo splicing sites. Results: The prediction accuracy we obtained was 87.53% at the true 5′ end splicing site and 87.37% at the true 3′ end splicing sites. The results suggested that the SVM approach could achieve higher accuracy than the previous approaches. Project partially supported by the Start-up Funding of Zhejiang University to Chen Liang-biao     

Analysis of the 3′ ends of tRNA as the cause of insertion sites of foreign DNA in Prochlorococcus

The purpose of this study was to investigate the characteristics of transfer RNA (tRNA) responsible for the association between tRNA genes and genes of apparently foreign origin (genomic islands) in five high-light adapted Prochlorococcus strains. Both bidirectional best BLASTP (basic local alignment search tool for proteins) search and the conservation of gene order against each other were utilized to identify genomic islands, and 7 genomic islands were found to be immediately adjacent to tRNAs in Prochlorococcus marinus AS9601, 11 in P. marinus MIT9515, 8 in P. marinus MED4, 6 in P. marinus MIT9301, and 6 in P. marinus MIT9312. Monte Carlo simulation showed that tRNA genes are hotspots for the integration of genomic islands in Prochlorococcus strains. The tRNA genes associated with genomic islands showed the following characteristics: (1) the association was biased towards a specific subset of all iso-accepting tRNA genes; (2) the codon usages of genes within genomic islands appear to be unrelated to the codons recognized by associated tRNAs; and, (3) the majority of the 3′ ends of associated tRNAs lack CCA ends. These findings contradict previous hypotheses concerning the molecular basis for the frequent use of tRNA as the insertion site for foreign genetic materials. The analysis of a genomic island associated with a tRNA-Asn gene in P. marinus MIT9301 suggests that foreign genetic material is inserted into the host genomes by means of site-specific recombination, with the 3′ end of the tRNA as the target, and during the process, a direct repeat of the 3′ end sequence of a boundary tRNA (namely, a scar from the process of insertion) is formed elsewhere in the genomic island. Through the analysis of the sequences of these targets, it can be concluded that a region characterized by both high GC content and a palindromic structure is the preferred insertion site.     

Introducing the History of Science at the French Middle School

In scientific teaching, especially in physics and chemistry, some historical aspects have been introduced at the secondary level in France, since 1993. Particularly, in 2007, the syllabuses of 11′–15′ years old level (collège) propose precise activities in history of science and technology. Detailed guidance has been distributed in official ministerial literature. The invention of Volta’s battery in 1800 is one of the examples proposed, which is detailed here.     

Evaluation of the antioxidant effects of four main theaflavin derivatives through chemiluminescence and DNA damage analyses

Theaflavins (TFs) are the dimers of a couple of epimerized catechins, which are specially formed during black tea fermentation. To explore the differences among four main TF derivatives (theaflavin (TF₁), theaflavin-3-gallate (TF₂A), theaflavin-3′-gallate (TF₂B), and theaflavin-3,3′-digallate (TF₃)) in scavenging reactive oxygen species (ROS) in vitro, their properties of inhibiting superoxide, singlet oxygen, hydrogen peroxide, and the hydroxyl radical, and their effects on hydroxyl radical-induced DNA oxidative damage were systematically analyzed in the present study. The results show that, compared with (−)-epigallocatechin gallate (EGCG), TF derivatives were good antioxidants for scavenging ROS and preventing the hydroxyl radical-induced DNA damage in vitro. TF₃ was the most positive in scavenging hydrogen peroxide and hydroxyl radical, and TF₁ suppressed superoxide. Positive antioxidant capacities of TF₂B on singlet oxygen, hydrogen peroxide, hydroxyl radical, and the hydroxyl radical-induced DNA damage in vitro were found. The differences between the antioxidant capacities of four main TF derivatives in relation to their chemical structures were also discussed. We suggest that these activity differences among TF derivatives would be beneficial to scavenge different ROS with therapeutic potential.     

Synthesis of Schiff bases of naphtha[1,2-d]thiazol-2-amine and metal complexes of 2-（2＇-hydroxy）benzylideneaminonaphthothiazole as potential antimicrobial agents

Objective： A series of 2-benzylideneaminonaphthothiazoles were designed and synthesized incorporating the lipophilic naphthalene ring to render them more capable of penetrating various biomembranes. Methods： Schiff bases were synthesized by the reaction of naphtha[1,2-d]thiazol-2-amine with various substituted aromatic aldehydes. 2-（2＇-Hydroxy）ben- zylideneaminonaphthothiazole was converted to its Co（Ⅱ）, Ni（Ⅱ） and Cu（Ⅱ） metal complexes upon treatment with metal salts in ethanol. All the compounds were evaluated for their antibacterial activities by paper disc diffusion method with Gram positive Staphylococcus aureus and Staphylococcus epidermidis and Gram negative Escherichia coli and Pseudomonas aeruginosa bacteria. The minimum inhibitory concentrations of all the Schiff bases and metal complexes were determined by agar streak dilution method. Results： All the compounds moderately inhibited the growth of Cram positive and Gram negative bacteria. In the present study among all Schiff bases 2-（2＇-hydroxy）benzylideneaminonaphthothiazole showed maximum inhibitory activity and among metal complexes Cu（Ⅱ） metal complex was found to be most potent. Conclusion： The results obtained validate the hypothesis that Schiff bases having substitution with halogens, hydroxyl group and nitro group at phenyl ring are required for the antibacterial activity while methoxy group at different positions in the aromatic ring has minimal role in the inhibitory activity. The results also indicated that the metal complexes are better antibacterial agents as compared to the Schiff bases.     

Effect of mineral admixtures and repeated loading on chloride migration through concrete

The effect of fly ash (FA) and ground granulated blast furnace slag (GGBFS) on chloride migration through concrete subjected to repeated loading was examined. Portland cement was replaced by three percentages (20%, 30%, and 40%) of mineral admixtures. Five repeated loadings were applied to concrete specimens using a WHY series fully automatic testing machine. The maximum loadings were 40% and 80% of the axial cylinder compressive strength (f′c). Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured. The results showed that the replacement percentages of mineral admixtures, the curing time and repeated loading had a significant effect on chloride migration through concrete. The transport number of chloride through concrete cured for 28 d increased with increasing FA replacement and markedly decreased with extension of the curing time. 20% and 30% GGBFS replacement decreased the transport number of chloride through concrete, but 40% GGBFS replacement increased the transport number. Five repeated loadings at 40% or 80% f′c increased the transport number of chloride for all mixes.