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新型生物可降解PLA沙障与传统草方格沙障防风效益  [PDF]
党晓宏,,,,,,,,,,,王红霞,赵鹏宇
北京林业大学学报 , 2015, DOI: 10.13332/j.1000-1522.20140245
Abstract: 为了解新型材料生物可降解聚乳酸纤维(PLA)沙障防风效益,通过测定PLA沙障样地内不同高度风速,分别研究1mx1m、2mx2m、3mx3m规格PLA沙障防风效能、地表粗糙度与风速廓线特征,同时以相同坡位同种规格的传统半隐蔽式麦草沙障样地和流动沙丘为对照,对比研究了PLA沙障与传统麦草沙障的防风效益。结果表明,新型生物可降解PLA沙障防风效能显著大于麦草沙障,2种类型沙障最大差值可达10.3%,2种材料沙障不同规格防护效果为1mx1m规格较其他2种规格更好;2种材料沙障增加地表粗糙度表现为PLA沙障>麦草沙障>流动沙丘,且均随规格增大呈逐渐下降趋势,在相同地形条件下,PLA沙障地表粗糙度均值为麦草沙障的1.4倍;2种材料沙障在迎风坡坡底、坡中、坡顶及背风坡4种地形下地表粗糙度差异不明显,其地表粗糙度均值为0.7cm;1mx1m规格的PLA方格沙障和麦草沙障内的风速廓线曲线呈现“S"型曲线特征,而在2mx2m和3mx3m规格的2种材料沙障内,风速廓线与对照裸沙丘相似,其风速廓线均呈指数函数分布。随着沙障规格的增大,降低风速作用减弱,其风速廓线逐渐由“S"型趋向于指数函数曲线。
聚乳酸纤维沙障对表层土壤含水量的影响  [PDF]
李谦,高永,汪季,周丹丹,迟悦春
中国水土保持科学 , 2012,
Abstract: ?在乌兰布和沙漠西南缘选择大小、走向相近的裸沙丘分别铺设聚乳酸纤维(pla)沙障与麦草沙障,设计规格为1m×1m、2m×2m、3m×3m。从2008年开始连续3年对2种沙障不同规格、不同坡位表层土壤含水量进行测定,同时以未铺设任何沙障的裸沙丘作为对照,比较新型材料pla沙障与传统沙障麦草沙障对表层土壤含水量的长时间影响。结果表明:1)pla沙障与麦草沙障以及裸沙丘含水量都随年份的增加而增加,2类沙障含水量增长幅度明显优于裸沙丘;2)就沙障规格而言,长时间保持土壤水分,效果最好的是pla沙障2m×2m规格;3)在0~10cm深度,pla沙障土壤含水量表现为迎风坡>背风坡>坡顶,麦草沙障与pla沙障相反;4)在10~20cm深度,pla沙障土壤含水量表现为坡顶>迎风坡>背风坡,麦草沙障同样与pla沙障相反。
月壤及模拟月壤微观结构的研究  [PDF]
李丽华,唐辉明,刘数华
岩土力学 , 2012,
Abstract: 为了对比研究月壤与模拟月壤的微观结构,介绍了月壤的形成作用过程和5种基本颗粒类型;通过真实月壤照片,对月壤微观结构进行了分析;利用火山灰为模拟月壤主体材料,对其成分进行了检测;对模拟月壤的火山灰颗粒进行了显微图像分析试验。结果表明,月壤存在胶结物微观颗粒,胶结物颗粒具有分支的组织形态和封闭的气泡,并且有金属铁珠存在;火山灰所含的主要成分及含量与月壤相似,经过粉碎的火山灰试样棱角较为明显,其纵横比峰值略小,稍显长条状,但与月壤比较相近,而复杂度因子则略有欠缺,说明颗粒还不够粗糙和多棱
模拟月壤研制的初步设想  [PDF]
郑永春,王世杰,刘建忠,李泳泉,邹永廖
空间科学学报 , 2005,
Abstract: 模拟月壤是月球样品的地球化学复制品.作者总结世界上已有的5种模拟月壤JSC-1,MLS-1,MLS-2,MKS-1和FJS-1的研制过程、方法与基本理化性质.认为系列化模拟月壤研制对中国首次月球探测有重要意义.在此基础上,作者提出系列化模拟月壤研制的基本思路.
钻进取样试验用模拟月壤  [PDF]
殷参
地质与勘探 , 2012,
Abstract: 钻具在月壤中进行钻进取样,是一个钻具与月壤相互作用的过程。为获得可靠的月壤钻具,在其研制过程中应在月壤里进行钻进试验。但地球上的真实月壤很珍贵,难以满足钻进试验的需要。采用能够较好地模拟真实月壤主要物理力学特性的模拟月壤,代替真实月壤进行钻进取样试验,是月壤钻具研制的一个必要手段。国外已对月壤进行了大量的研究,并取得了丰富的成果。本文在对真实月壤以及模拟月壤研究进行总结的基础上,对月壤钻具研制中所需的模拟月壤进行了简要的阐述,可供月壤钻具研制参考。
Effects of electron radiation on properties of PLA  [PDF]
R. Malinowski,P. Rytlewski,M. ?enkiewicz
Archives of Materials Science and Engineering , 2011,
Abstract: Purpose: The aim of the paper was to examine the effects of electron radiation on physicochemical properties of pristine poly(lactic acid) (PLA), or polylactide, and of polylactide containing a selected crosslinking agent.Design/methodology/approach: Samples to be examined were prepared in granulated forms or as moulded pieces and then treated with the high-energy electron radiation (ca. 10 MeV). The methods of gel permeation chromatography (GPC), rheology, Fourier transform infrared (FTIR) spectroscopy, and dynamic mechanical thermal analysis (DMA) were used to determine physicochemical properties of the samples. A humidity sensor was utilised to determine water vapour permeability.Findings: It has been found that PLA undergoes degradation upon the electron radiation. Triallyl isocyanurate (TAIC) when introduced into polylactide causes plasticization of this polymer whereas irradiation of polylactide containing TAIC leads to crosslinking of PLA. Crosslinked PLA exhibits limited plastic flow or no flow at all and an elevated glass transition temperature. Water vapour permeability of a film made of PLA modified this way is much less than that of a film produced from original PLA.Research limitations/implications: Further studies of crosslinked PLA are advisable, especially assessment of the gelation degree, strength of the plasticized material, and biodegradation.Practical implications: Crosslinked PLA may be applied in practical processes, especially in thermoforming in which increased resistance of a material against deformation at elevated temperatures is required.Originality/value: Substantial influence of the electron radiation on properties of PLA was established. The material undergoes significant degradation upon even relatively small radiation doses. In order to crosslink PLA, TAIC in the amount of ca. 3 wt% and the electron radiation doses of up to ca. 60 kGy have to be applied.
粘土沙障及麦草沙障合理间距的调查研究  [PDF]
常兆丰, 仲生年, 韩福桂, 刘虎俊
中国沙漠 , 2000,
Abstract: 确定机械沙障障间距的基本原理是障间风蚀沙量等于积沙量。障间凹曲面面积与障间距及沙面坡度之间存在着显著的回归关系,运用这种回归关系就可以建立障间风蚀沙量等于积沙量的等式方程。在民勤沙区取样分别建立粘土沙障和麦草沙障的风蚀沙量等于积沙量的等式方程,计算出沙面坡度0°~8°和0°~10°的粘土沙障和麦草沙障间距分别是253.1~185.9cm和261.4~155.0cm;粘土沙障高度应为适宜高度范围内的最小值;粘土沙障在障高为15cm、沙面坡度>8°时障间没有风蚀。麦草沙障在坡度>10°时障间没有风蚀;15cm高的粘土沙障和固沙有效高度13cm的麦草沙障的最小间距分别是185.9cm和155.0cm;若需要在固定就地沙面的基础上接纳外来流沙或者需要风蚀部分就地沙粒时,可将接纳沙量或风蚀沙量的平均厚度作为参数之一计算障间距;按照风蚀沙量≤积沙量的障间距设置的沙障,其方格形式只适合在害风方向多变的地段设置。
响叶杨(populusadenopoda)种子的形成及其寿命  [PDF]
吴琼美,樊汝汶
南京林业大学学报(自然科学版) , 1984, DOI: 10.3969/j.jssn.1000-2006.1984.01.014
Abstract: <正>用显微技术及软x射线摄影,定位观察响叶杨种子发育过程中的形态变化与胚胎发育的对应关系。根据观察、试验的结果,讨论了环境条件与种子寿命的关系;还测定了响叶杨种子寿命的变化规律及其影响因素,探索延长这种子寿命的方法。
Josep Pla und Montaigne. Eine Skizze [Josep Pla and Montaigne. An outline]  [PDF]
Geisler, Eberhard
Zeitschrift für Katalanistik , 2006,
Abstract: Joseph Pla was a great admirer of French literature. As such, the writer Michel de Montaigne was of particular importance to him. Accordingly, Pla once remarked that he owed a plethora of fundamental philosophical knowledge to the author of Essais, as well as the ability to weigh and judge. In Pla’s opinion, the Frenchman was an ideal representative of a non-bombastic view of man and as a moralist. In the following passages, three further relations between the two authors will be reflected upon. To begin with, the depiction of the self and the emerging difficulty with the same phenomenon shall be treated; since the ego is not always present to itself, it vacillates between authenticity on the one hand, and convention and role on the other. Therefore the topic of the instability of human relation stands at the center of Montaigne’s observations as well as of Pla’s, which can evidently be traced in his tale “Contraban”; the theme of instability is counterbalanced by a certain consistency in these authors’ views. At last it demonstrates that both authors tend, with regard to their view of man, towards a policy of power decomposition. Thus they establish, with their understanding of nature and health, an inevitable counterimage (since Pla is defined by a profession towards antique cynicism and its use of the verb “badar”).
响蜜Lie科的新记录
杨岚
动物学研究 , 1995,
Abstract: 1994年10月15日马中翼等人在云南省泸水县的老窝捕获到1只雄鸟,经中国科学院昆明动物研究所鉴定为黄腰响蜜lie,为我国鸟类科的新记录。标本保存在中国科学院昆明动物研究所鸟类标本室。科的特征体形较小。嘴形似雀,短而粗实,上嘴稍弯曲;尾羽12枚;翅形长而尖,仅具9枚初级飞羽;脚呈对趾型,第2、3趾向前,第1、4趾向后,似啄木鸟。
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