61 resultados para Machiavelli, Niccolò, 1469-1527.


Relevância:

10.00% 10.00%

Publicador:

Resumo:

介绍了我国土壤污染的突出特点及其危害,回顾了污染土壤从清洁技术研究到物理、化学和生物修复研究的历程,总结了污染土壤修复取得的初步成果,提出了污染土壤修复的实质和系统技术方法。根据我国土壤污染的实际和修复需求,本文提出了当前本领域急需开展的研究内容,预测了污染土壤修复研究对环境科学相关学科的推动作用。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In this paper, Y2O3 powder phosphors without metal activators were successfully prepared by the sol-gel method. The obtained sample shows an intense bluish-white emission (ranging from 350 to 600 nm, centered at 416 nm) under a wide range of UV light excitation (235-400 nm). The chromaticity coordinates of the sample are x = 0.159, y = 0.097, and the quantum yield is as high as 64.6%, which is a high value among the phosphor family without metal activators. The luminescent mechanisms have been ascribed to the carbon impurities in the Y2O3 host.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In this work, a new promoter, tetrasulfophthalocyanine (FeTSPc), one kind of environmental friendly material, was found to be very effective in both inhibiting self-poisoning and improving the intrinsic catalysis activity, consequently enhancing the electro-oxidation current during the electro-oxidation of formic acid. The cyclic voltammograms test showed that the formic acid oxidation peak current density has been increased about 10 times compared with that of the Pt electrode without FeTSPc. The electrochemical double potential step chronoamperometry measurements revealed that the apparent activity energy decreases from 20.64 kJ mol(-1) to 17.38 kJ mol(-1) after Pt electrode promoted by FeTSPc. The promoting effect of FeTSPc may be owed to the specific structure and abundant electrons of FeTSPc resulting in both the steric hindrance of the formation of poisoning species (CO) and intrinsic kinetic enhancement. In the single cell test, the performance of DFAFC increased from 80 mW cm(-2) mg(-1) (Pt) to 130 mW cm(-2) mg(-1) after the anode electrode adsorbed FeTSPc.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A donut-shaped spray chamber has been developed for the introduction of aerosol and/or volatile chemical species into the inductively coupled plasma. Compared with the Fassel-Scott spray chamber, it gives a higher efficiency of aerosol generation and transportation and superior stable inner pressure. As a result, it brings the benefits of higher intensity signal, lower background, higher measurement precision, and better detection limits. Using:his spray chamber, it is more convenient to introduce volatile chemical species into the sampling system, and more flexible for the choice of introducing aerosol and volatile chemical species separately or simultaneously into the plasma. It is also suitable for FIA technique. (C) 1998 Elsevier Science B.V. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

胆红素系列氧化过程中的自催化现象牛建军,董绍俊(中国科学院长春应用化学研究所电分析化学开放研究实验室,长春,130022)关键词胆红素;胆汁红紫素;电催化氧化胆红素(BR)曾一度被认为是一种毒害性物质,因为它是导致黄疸病和核黄疸的主要原因[1,2]。...

Relevância:

10.00% 10.00%

Publicador:

Resumo:

由六次甲基四碲富瓦烯(HMTTeF)所形成的有机化合物晶体,有两种可能的化学结合形式:一种是分子中的Te原子离子化,形成离子型化合物;另一种是分子中心共轭π键离子化,或者形成离子型化合物,或者形成混合价态型化合物。至今被报道的HMTTe F化合物晶体都只含有其中一种化学结合形式,而标题化合物晶体则同时含有上述两种化学结合形式。本文将该晶体的晶体结构、化学结合与电导性的关系作简要的讨论。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Through random sequencing, we found a total of 884000 base-pairs (bp) of random genomic sequences in the genome of Chinese shrimp (Fenneropenaeus chinensis). Using bio-soft Tandem Repeat Finder (TRF) software, 2159 tandem repeats were found, in which there were 1714 microsatellites and 445 minisatellites, accounting for 79.4% and 20.6% of repeat sequences, respectively. The cumulative length of repeat sequences was found to be 116685 bp, accounting for 13.2% of the total DNA sequence; the cumulative length of microsatellites occupied 9.78% of the total DNA sequence, and that of minisatellites occupied 3.42%. In decreasing order, the 20 most abundant repeat sequence classes were as follows: AT (557), AC (471), AG (274), AAT (92), A (56), AAG (28), ATC (27), ATAG (27), AGG (18), ACT (15), C (11), AAC (11), ACAT (11), CAGA (10), AGAA (9), AGGG (7), CAAA (7), CGCA (6), ATAA (6), AGAGAA (6). Dinucleotide repeats, not only in the aspect of the number, but also in cumulative length, were the preponderant repeat type. There were few classes and low copy numbers of repeat units of the pentanucleotide repeat type, which included only three classes: AGAGA, GAGGC and AAAGA. The classes and copy numbers of heptanucleotide, eleven-nucleotide and thirteen-nucleotide primer-number-composed repeats were distinctly less than that of repeat types beside them.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文对我国胶州湾养殖的主要滤食性贝类菲律宾蛤仔的生理生态学进行了系统研究,通过资料收集、现场调查、定点连续观测、现场模拟实验等综合性方法探讨了菲律宾蛤仔养殖对胶州湾生态环境的影响。主要系统调查了不同季节胶州湾自然沉积物中C、N和P的变化;研究了菲律宾蛤仔生物沉积作用的周年变化;同时还研究了不同月份菲律宾蛤仔的耗氧率,排泄率的变化。结果如下: 1、综述了滤食性贝类通过滤食、生物沉积和呼吸排泄等作用对海区环境的影响,系统评述了埋栖性贝类生物沉积的测定方法及其生态效应。国际上已有不少研究专门报道了贝类在海区现场的生物沉积作用,而在我国,关于埋栖性贝类生物沉积特征的研究较少。 2、在胶州湾红岛附近养殖海区,从2003年10月到2004年7月以及2005年8月到2005年12月对菲律宾蛤仔生物沉积进行了现场测定。大、中和小规格菲律宾蛤仔生物沉积速率范围分别为121.6~1527.4mg/ind·d,49.5~902.1mg/ind·d,14.2~653.9mg/ind·d。海底自然沉积物OM分别为3.1%和5.7±1.1%。而大、中和小规格菲律宾蛤仔生物沉积物的OM分别为6.2±1.2%、5.9±1.3%和6.1±1.4%。大、中和小菲律宾蛤仔生物沉积物TP含量分别为399±26ppm,372±16ppm,345±15ppm。大、中和小规格蛤子生物沉积物中的OP分别为80±17ppm,92±12ppm和102±10ppm,明显高于对照沉积物的OP。生物沉积物中的OP/TP要明显高于对照沉积物,前者为23~25%,而后者仅为20%。菲律宾蛤仔生物沉积速率呈明显季节性变化,其与软体干重呈异速方程关系,a值的变化范围为0.85~4.50(平均为2.32)。菲律宾蛤仔贝肉的OC和ON含量分别为40.80±7.59%和的10.26±2.19%。贝壳的OM、TP、OP、OC和ON含量分别为3.28±0.47%、109.2±16.6ppm、64±22.9ppm、12.21±0.30%和0.19±0.05%。 3、不同规格菲律宾蛤仔的代谢率呈明显季节变化。7月份,单位个体菲律宾蛤仔耗氧率最高为1.72 g/ind•h;8月份,排氨率和排磷率达到最高,分别为2.44μmol/ind•h、0.58μmol/ind•h。菲律宾蛤仔的O:N在10.7~31.9范围内,O:N和N:P具有明显的季节变化,8月份最大。 4、研究了本湾底质环境特征,测定了自然沉积物的OM、OC、ON、TP和OP的含量。胶州湾站位沉积物的有机质和C、N、P含量季节变化不大,有机质含量大约为3.5%,OC和ON含量大约为0.7%和0.06%。TP含量为285ppm左右,OP含量大约为50ppm。养殖海区沉积物有机质和C、N、P的含量明显高于非养殖海区沉积物含量,其C/N、C/OP和OP/TP一般也比非养殖海区站位高。 夏季,胶州湾菲律宾蛤仔养殖区(平均密度按600ind/m2计算)单位面积(m2)的生物沉积速率平均为176g/m2•d,对于整个海湾,将有1.2万吨的悬浮颗粒物通过贝类排粪作用沉积到海底。通过菲律宾蛤仔的呼吸作用,单位面积(m2)的耗氧量为6.67gO2/m2•d;同时从海底向水体释放大约为16.7μmolN /m2•d和3.3μmolP/m2•d的溶解态N和P;对于整个海湾,菲律宾蛤仔将耗掉水体中的467T/d氧气,同时向水体中释放16.4T/d氨氮和7.2T/d无机磷。对于半封闭的胶州湾,大规模菲律宾蛤仔的滩涂养殖其产生的生物沉积物聚集于海底可能会对海区底部的物理化学和生物环境产生很大影响;而氧的消耗、氨和无机磷的排泄,会对水层中的物理化学环境和营养盐循环产生很大影响。从而由此推测,菲律宾蛤仔高密度大规模的养殖,在整个胶州湾水层-底栖系统耦合作用中可能起着很重要的作用。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本发明涉及一种花锚植物的引种栽培技术,该技术包括种子处理技术和引种栽培技术。本发明通过采用花锚种子的物理和化学处理方法,使花锚种子萌发率达75%以上;通过地膜覆盖技术,即在种子播种前采用地膜覆盖7- 28天,可有效地控制杂草数量和生长,为规模化种植奠定可靠的基础;通过在拔1500 —4500米的原产水浇大田或适宜旱耕地的引种栽培途径,可快速恢复花锚植物的资源量,并有效地保证花锚植物的药材品质和药效成分。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

广义特征值问题是结构动力分析计算的关键之一.应用Reyle igh极小值原理,将神经网络的能量函数的极小点对应于广义特征值问题的最小特征值所对应的特征向量,在神经网络朝着能量函数极小点运动的同时得到了最小特征值所对应的特征向量的精确解答.从特征值的变分特性出发,给出了基于罚函数法的其他特征值的神经网络求解方案,从而在理论上给出了广义特征值问题的所有特征值的神经网络求解方法.仿真计算表明,该方法正确、有效可行.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文通过所设计的估计器的预测以及同时采用事件和时间驱动的执行器方案来弥补机器人遥操作系统中的不确定时延现象。利用该方案对机器人遥操作系统所涉及的试验的软硬件进行设计,试验结果说明了此补偿策略的有效性。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

在未来持续多变和不可预测的竞争环境中,保持企业的竞争地位和生存发展的重要概念就是由敏捷制造和动态联盟构成的敏捷竞争的概念。动态联盟的思想加上当今高速信息网的建立和CALS提供的支持全球合作的技术和标准,为我们确定先进制造技术的研究计划,帮助中国的广大企业顺利地进入21世纪的国际合作大环境都有着重要的意义。

Relevância:

10.00% 10.00%

Publicador:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

混汞法是一种设备简单、操作简便且应用历史悠久的提金方法,在世界范围内得到了普遍使用,同时也导致了严重的汞污染。本文介绍了混汞法的流程以及汞的释放过程和释放因子;综述了应用混汞法提金的不同国家和地区,对由此引发的大气、水体、生物(包括人体)和土壤汞污染的研究现状,并讨论了采金地区的环境管理政策。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

利用以水玻璃、硫酸、硫酸铝和废铁屑为原料研制出的聚硅酸硫酸铝铁类混凝剂 ,在静态处理造纸废水的基础上 ,使用自行设计的动态模拟实验装置 ,对贵州省某造纸厂总排口废水进行混凝处理。在最佳水力条件下 ,造纸废水色度去除率达 96.9% ,CODCr去除率达 92 .5 % ,出水水质低于国家造纸工业污染物排放一级标准 ,说明复合型聚硅酸铝铁类混凝剂对造纸废水有着优异的去除效果