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1.
由于滤纸在其制造工艺中部分含氨氮的化合物渗入滤纸纤维内部,并且不易去除,并对通过滤纸的测定样品造成很大误差.因此,对测定样品的预处理应使用无胺法制成的滤纸. 相似文献
2.
从温泉、堆肥等环境采集样品,以滤纸条为唯一碳源,用微晶纤维素粉和羧甲基纤维素钠(CMC-Na)-刚果红培养基进行分离和筛选出几株高温纤维素分解菌.进行测定这些菌株的Cx、滤纸酶活性试验,两种酶的作用温度相对较宽,Cx酶的最适酶活性温度约70℃,而滤纸酶活性的最适温度因菌株差异有所差异. 相似文献
3.
在环境监测工作中,对水中悬浮物质测定,常采用滤纸重量法。方法虽操作简便,但如何做到准确测定不易掌握。如当测定水质中含悬浮物低时（小于２２ｍｇ／Ｌ）,经烘干恒重后测定,结果往往出现负值,或自控样品空白值也会出负值现象,质量控别样品达不到规范要求等。根据分析实验结果,影响悬浮物的准确测定,有较多影响因子。主要有：滤纸中可溶物含量约为０．１６—０．２５％,经过水样过滤后,可溶物溶解损失,空气湿度及放冷时间长短。因此,在测定悬浮物时除按监测分析方法要求餐,还应注意上述几点的影响,以得到更为精确的监测结果… 相似文献
4.
本实验运用石灰滤纸法(LTP法)对重庆涪陵部分蚕区的大气氟化物进行较长时间(10天左右)的吸收，再用氟离子选择电极法测定其含量，进而根据能斯特方程推算出大气中氟的含量以测定大气氟污染情况。同时还比较了各种测定方法的优缺点及实用性等。通过对涪陵地区的三个不同采样点的滤纸样品氟含量和空白滤纸氟含量的测定，测得1#、2#、3#大气含氟量的平均值分别为0．598μg/dm2．d、2．357μg/dm2．d、1．567μg/dm2．d，与国家环境空气质量标准(GB 3095—1996)比较对照可知涪陵蚕区1#表现正常；2#点含氟量极高，严重超标；3#点轻微超标。 相似文献
5.
采用中速定量滤纸为滤料测定悬浮物时,滤纸上可溶物含量约0．25％,经水过滤后溶解于水,影响测定值．所以滤纸用前先用蒸馏水冲洗过滤几遍,以除去可溶性物质,再烘干至恒重,待用． 相似文献
6.
悬浮物测定时滤纸上可溶物的影响及消除 总被引：1，自引：0，他引：1
采用中速定量滤纸为滤料测定悬浮物时,滤纸上可溶物含量约0．25％,经水过滤后溶解于水,影响测定值．所以滤纸用前先用蒸馏水冲洗过滤几遍,以除去可溶性物质．再烘干至恒重,待用。 相似文献
7.
《邢台职业技术学院学报》2017,(3):100-104
实验中利用(1+3)硝酸,把生铁样品用钢量瓶溶解、稀释、过滤于200ml容量瓶中,用5%硝酸冲洗滤纸并将溶液稀释至刻度,用ICP测定生铁中As,Cr,Cu,Ni,Sn。本方法的回收率在97.8%-102.6%之间。 相似文献
8.
本试验采用国家标准规定的蓄脂瓶法和文献介绍的滤纸包法分别测定了10种饲料中的粗脂肪含量。结果经统计分析表明差异不显著t0.05),且相对偏差均小于5％,属允许的相对偏差范围内。滤纸包法和蓄脂瓶法一样都可用于测定饲料中的粗脂肪,但滤纸包法因方法简便,又能节省实验器材、试剂而更适于进行实验教学及大批量的饲料检测。 相似文献
9.
以麦糠纤维素为碳源,从造纸厂污水治理产生的废弃物——黑泥中分离出9株能分解纤维素的菌株。分别对其进行了滤纸分解度、羧甲基纤维素酶活力、天然纤维素酶活力、不同温度对纤维素分解菌酶活力的影响等方面的测定。结果表明:W-07菌株对滤纸的分解能力最强,不到14h滤纸全成糊状;同时羧甲基纤维素酶活力、滤纸糖化力和天然纤维素酶活力也最高,且在55℃的条件下具有最高的酶活力。将该菌种经扩大培养后应用到有机肥生产中,不但能减少黑泥对环境的再污染,同时产生了良好的经济效益。 相似文献
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11.
The properties of two types of fly ash geopolymers made from class F fly ashes produced in wet bottom and dry bottom boilers were investigated in the present study. The source material used in the geopolymer concrete was activated with sodium hydroxide and sodium silicate solution. The results revealed that the geopolymer produced with wet bottom boiler fly ash(CZ-FA)hardened quickly, and had higher early-age strength and lower shrinkage than the geopolymer produced with dry bottom boiler fly ash(SX-FA). The compressive strength of the two geopolymers made from CZ-FA and SX-FA was 45 MPa and 15 MPa respectively when cured at 60 ℃ and delayed for 14 d. However, after 90 days' delay, the compressive strength of both the samples is almost the same, up to 80 MPa. Nearly 20% volume shrinkage of the samples made from SX-FA was much higher than that made from CZ-FA, which was almost zero. XRD, SEM/EDS and FT-IR were used to analyze the main reason of the differences. 相似文献
12.
冯喜忠 《商丘师范学院学报》2005,21(5):167-169
功和动能定理在求解相关的物理问题时有着重要作用，在不同的参考系中计算的功值是不相同的．其差值决定于运动物体在这一运动过程中的动量增量与两系相对速度的乘积．在不同的惯性系中质点的动能定理有着相同的形式．质点系内力所作的功在不同的惯性系中也是相等的，其功值的大小与参考系的选择无关，在非惯性系中应用动能定理应当考虑惯性力所作的功．结论才是正确的， 相似文献
13.
专业认同是教师专业成长的起点,也是教师专业发展的动力之源.研究幼儿园教师专业认同的理论模型和基本结构具有重要的理论与实践意义.本研究拟在确认幼儿园教师专业认同结构要素的基础上,通过因素分析来建构幼儿园教师专业认同的理论模型.为此,本研究选取了604名幼儿园教师作为有效样本,用探索性因素分析考察问卷的结构要素,用验证性因素分析考察问卷的构念效度.结果发现:通过探索性因素分析可以确定幼儿园教师专业认同的六维结构要素,分别是目标确信、情感归属、投入意愿、胜任效能、持续承诺和人际支持;利用结构方程模型的验证性因素分析检验问卷的效度,表明问卷六维结构与数据显示拟合良好:问卷的内部一致性系数、分半信度分别为0.90和0.81,说明问卷结构清晰,信度、效度理想,可以作为测评幼儿园教师专业认同水平的有效工具. 相似文献
14.
Gautam Puhan 《Journal of Educational Measurement》2010,47(1):54-75
In this study I compared results of chained linear, Tucker, and Levine-observed score equatings under conditions where the new and old forms samples were similar in ability and also when they were different in ability. The length of the anchor test was also varied to examine its effect on the three different equating methods. The three equating methods were compared to a criterion equating to obtain estimates of random equating error, bias, and root mean squared error (RMSE). Results showed that, for most studied conditions, chained linear equating produced fairly good equating results in terms of low bias and RMSE. Levine equating also produced low bias and RMSE in some conditions. Although the Tucker method always produced the lowest random equating error, it produced a larger bias and RMSE than either of the other equating methods. As noted in the literature, these results also suggest that either chained linear or Levine equating be used when new and old form samples differ on ability and/or when the anchor-to-total correlation is not very high. Finally, by testing the missing data assumptions of the three equating methods, this study also shows empirically why an equating method is more or less accurate under certain conditions . 相似文献
15.
The Effects of a Student Sampling Plan on Estimates of the Standard Errors for Student Passing Rates
Examined in this study were three procedures for estimating the standard errors of school passing rates using a generalizability theory model. Also examined was how these procedures behaved for student samples that differed in size. The procedures differed in terms of their assumptions about the populations from which students were sampled, and it was found that student sample size generally had a notable effect on the size of the standard error estimates they produced. Also the three procedures produced markedly different standard error estimates when student sample size was small. 相似文献
16.
陈志宏 《湖南城市学院学报》2001,18(3):93-94
篮球运动中学生的视野并非单纯由生理结构所决定；它同技战术、环境因素、心理状态有机联系；教学与训练中须将多种因素有机融合方能产生最佳效果. 相似文献
17.
李广义 《常熟理工学院学报》2007,21(3):53-57
在环境伦理学中,自然价值一方面指自然物对人的有用性,即自然的外在价值或工具价值;另一方面是指自然界或生态系统的自我满足,即自然物之间彼此联结、相互利用而产生的动态平衡效应,即自然的内在价值或固有价值。自然价值是外在价值和内在价值的统一。 相似文献
18.
《The Journal of educational research》2012,105(5):245-249
AbstractThe purpose of this study was to examine the quality of writing of second and sixth graders who were taught by two different writing approaches (whole language and traditional). The writing samples were rated on two separate criteria-quality of content and mastery of mechanics. Three raters evaluated the writing samples, and an analysis of variance was performed to measure differences. The findings were as follows: (a) Second graders who were taught by teachers using the whole language approach produced better writing samples when evaluated on meaning and content, (b) There was no difference in writing samples in the correct use of mechanics of second graders taught by either approach, (c) There was no difference in writing samples of sixth graders taught by either approach. 相似文献
19.
近年来关于DINA模型的相关研究显示,样本量、先验分布、经验贝叶斯或完全贝叶斯估计方法、样本的代表性、项目功能差异和Q阵误指等,均可能是导致DINA项目参数估计发生偏差的原因。使用Monte Carlo模拟试验,对DINA项目参数(猜测参数和失误参数)的组合变化类型和偏差量进行考察,通过条件极大似然估计法估计知识状态,发现项目参数估计值与真值偏差不大时,对知识状态估计的精度影响不大;但是项目参数偏离真值较大时,尤其是在三种组合类型上,对属性掌握存在明显的高估或低估现象。研究结果对于诊断测验等值有一定的启示:若两个测验上锚题的项目参数出现了较大的偏差(0.1),则需要考虑等值的必要性。 相似文献
20.
Pigeons were trained to match temporal (2 and 8 sec of keylight) and color (red and green) samples to vertical and horizontal comparison stimuli. In Experiment 1, samples that were associated with the same correct comparison stimulus displayed similar retention functions; and there was no significant choose-short effect following temporal samples. This finding was replicated in Phase 1 of Experiment 2 for birds maintained on the many-to-one mapping, and it was also obtained in birds that had been switched to a one-to-one mapping by changing the comparison stimuli following color samples. However, in Phase 2 of Experiment 2, when the one-to-one mapping was produced by changing the comparison stimuli following temporal samples, a significant choose-short effect was observed. In Experiment 3, intratrial interference tests gave evidence of temporal summation effects when either temporal presamples or color presamples preceded temporal targets. This occurred even though these interference tests followed delay tests that failed to reveal significant choose-short effects. The absence of significant choose-short effects in Experiment 1 and in Phase 1 of Experiment 2 indicates that temporal samples are not retrospectively and analogically coded when temporal and nontemporal samples are mapped onto the same set of comparisons The interference test results suggest that the temporal summation effect arises from nonmemorial properties of the timing system and is independent of the memory code being used 相似文献