回归分析方法在书库架位预留计算中的实证分析

架位预留是书库管理中的核心,以华南农业大学图书馆经济学类图书为例,探讨了回归分析法在架位预留中的具体计算方法,以及这种方法的适用性。     

高校图书馆新书书库借阅情况的统计与分析

以河池学院为例，对河池学院图书馆新书书库馆藏量、外借率、藏书比例等作统计分析，并对今后图书馆馆藏建设的优化进行了探讨。     

优化书库环境加强图书保护

通过分析损害图书的各种自然因素,阐明优化书库环境、加强图书保护的重要性。     

黄山市城市水土流失及预防对策

在调查研究的基础上,对黄山市在建设开发中存在的乱建、乱采、乱挖、乱倒（“四乱”）现象进行了分析,探讨了其产生的主要人为因素,并在此基础上,提出了若干加强预防监督措施的策略。     

努力抓好生态农业建设的几点体会

南县地处湖南省北隅，洞庭湖平原中部，土地肥沃，物产丰富，水资源充足。但是，七十年代忽视了对自然资源的保护和台理开发利用，加之人口骤增，使生态失调问题日趋严重；滥砍乱伐，造成水土流失，农村能源严重短缺；     

徐州煤田塌陷地的复垦与利用

文中论述了徐州煤田概况，塌陷及其危害，为了综合整治塌陷地进行了复垦的总体规则。同时开展了６项复垦试验，取得了显著地经济效益，社会效益和生态效益，新复垦的农田由于土层被搅乱，其理化性状不良，肥力偏低，耕层缺少有机质和氮素，因此，要重视复垦的改良和施肥。     

深水养殖网箱浮架变形模拟及结构改进设计

由高密度聚乙烯材料制作的网箱浮架在波浪流冲击下具有明显的变形,过大变形甚至会导致浮架失效破坏。该研究介绍了一种用于模拟波流作用下网箱系统受力变形的有限元计算模型,并利用前人的研究结果对数值模型进行了验证。在此基础上,以中国南海区常用规格80 m周长的圆形网箱为研究对象,设定27种大浪强流条件,对各种规则波和水流组合条件下深水网箱浮架动力变形进行了数值模拟,给出了不同波流工况下浮架最大变形位置处的应变模拟结果。结果表明,浮架变形随着波高或流速的增加而增大,但随着波浪周期的增加变化很小,在波高7m、周期9s、流速1.5m/s条件下浮架发生屈服破坏的风险极大。为降低高海况下浮架局部屈服破坏风险,对浮架结构进行了改进,科学提出了一种能够有效增强网箱浮架结构安全的技术措施。     

黄瓜自动分级系统的研制

该文回顾了农产品分级的机器视觉技术，提出了黄瓜分级的标准。开发了机器视觉系统，包括照明、彩色CCD像机、抓取架、微机、图像监视器、挑选机器人和传送带。设计了分级系统的软硬件设备。     

安远县“八个禁止”抓好水土保持重点治理项目区管护

<正>为了抓好水土保持重点治理项目区管护工作,该局与乡村两级签订了《水土保持重点治理项目区管护公约》,该公约明确规定:禁止在保护区内进行乱砍、乱开、乱烧、乱挖等破坏植被人为造成水土流失的一切行为     

农业生产面临的问题及金融对策

霍邱县农业生产亟待解决的问题是农业投入不足，农业生产成本啬，生产资料市场乱，价格高，农民负担反弹现象严重农业综合生产能力较低。作者银行角度谈几点金融对策，拓宽农业投入。     

保鲜运输车温度场分布特性试验研究

为解决果蔬保鲜运输车厢体内温差过大的问题,搭建了基于压差原理的保鲜运输温度场试验平台。通过改变回风道风速、回风道长度、开孔隔板开孔率、堆栈方式、气流导轨等影响气流形式的因素,研究了这些因素对保鲜运输车厢温度场分布的影响。结果表明:回风道风速越大,回风道越长,保鲜厢内的温度场均匀性越好;堆栈方式为中间两侧留空时,厢体内温度场均匀性优于仅中间留空、两侧留空和满载等3种堆栈方式;开孔隔板开孔率对保鲜室中横截面温度场均匀性的影响较大;有气流导轨时的温度场均匀性优于无气流导轨时。当回风道长度为1.5m,回风道风速为8m/s,开孔率为16.11%,堆栈方式为中间两侧留空,有气流导轨时,保鲜运输车厢内的温度场均匀性较优,此时保鲜室内中纵截面温度分布的标准差为1.15℃,中横截面温度分布的标准差为2.04℃。研究结果为果蔬保鲜运输车的厢体结构优化提供参考。     

Influence of the nitrification inhibitor DMPP on the community composition of ammonia-oxidizing bacteria at microsites with increasing distance from the fertilizer zone

The effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N transformations and composition of ammonia-oxidizing bacteria (AOB) communities was investigated at the centimeter scale in a microcosm experiment under laboratory conditions. After 28 days, samples were collected from soil treated with urea or urea and DMPP at increasing distance from the fertilizer zone; this distance ranged from 0 to 5 cm in both horizontal and vertical directions. The results showed that DMPP application significantly increased soil pH and NH ₄ ⁺ -N and mineral N (NH ₄ ⁺ -N, NO ₃ ^? -N, and NO ₂ ^? -N) concentrations but decreased (NO ₃ ^? + NO ₂ ^? )-N concentration, and such effect was decreased by increasing the distance from the fertilizer zone. Fingerprint profiles of denaturing gradient gel electrophoresis showed that the number of bands decreased by increasing the distance from the fertilizer zone due to decreasing NH ₄ ⁺ -N concentrations in the urea treatment. Compared to urea applied alone, DMPP application increased NH ₄ ⁺ -N concentrations and decreased AOB diversity from 0 to 3 cm but promoted diversity from 3 to 5 cm distance from the fertilizer zone. A phylogenetic analysis showed that AOB communities were dominated by Nitrosospira cluster 3. Therefore, the nitrification inhibitor DMPP modified the composition of AOB communities by increasing the distance from the fertilizer zone and this probably was related to the changes in soil pH and inorganic N concentration.     

Adverse Effects of Ammonia on Nitrification Process: the Case of Chinese Shallow Freshwater Lakes

Nitrification is a process in which ammonia is oxidized to nitrite (NO ₂ ^? ) that is further oxidized to nitrate (NO ₃ ^? ). The relations between these two steps and ambient ammonia concentrations were studied in surface water of Chinese shallow lakes with different trophic status. For the oxidations of both ammonia and NO ₂ ^? , more eutrophic lakes generally showed significantly higher potential and actual rates, which was linked with excessive ammonia concentrations. Additionally, both potential and actual rates for ammonia oxidation were higher than those for NO ₂ ^? oxidation in the more eutrophic lakes, while in the lakes with lower trophic status, both potential and actual rates for ammonia oxidation were almost equivalent to those for NO ₂ ^? oxidation. This can be explained by the excessive unionized ammonia (NH₃) concentration that inhibits nitrite-oxidizing bacteria in the more eutrophic lakes. The laboratory experiment with different ammonia concentrations, using the surface water in a eutrophic lake, showed that ammonia oxidation rates were proportional to the ammonia concentrations, but NO ₂ ^? oxidation rates did not increase in parallel. Furthermore, NO ₂ ^? oxidation was less associated with particles in natural water of the studied lakes. Without effective protection, it would be selectively inhibited by the excessive ammonia in hypereutrophic lakes, resulting in NO ₂ ^? accumulation. Shortly, the increased concentrations of ammonia cause a misbalance between the NO ₂ ^? -producing and the NO ₂ ^? -consuming processes, thereby exacerbating the lake eutrophication.     

Mercury antagonists: Effects of sodium chloride and sulfur group (VIa) compounds on excystment of the brine shrimp artemia

Brine shrimp excystment, although highly resistant, is severely inhibited by mmolar mercuric chloride. The presence of 100 mmolar NaCl largely prevents the toxic response. The chloride effect can be explained if the toxic Hg species, neutral HgCl₂, is converted into HgCl _inf3 ^sup2? and HgCl _inf4 ^sup2? since charged species not likely to penetrate cyst walls. Other Hg antagonists include SO _in3 ^su2? , SeO _inf3 ^sup2? , TeO _inf3 ^sup2? and TeO _inf4 ^sup2? , but not SO _inf4 ^sup2? and SeO _inf4 ^sup2? . The activity of both Te species can be explained by ready reduction of Te(VI) to Te(IV). Significant anti-mercurial effects were seen in mmolar thiols, ethionine and organoselenium compounds. Thiamine and methionine were both active Hg antagonists at 10 to 30 mmolar levels. The activities of S, Se and Cl^? compounds show that both geochemical and physiological modes of defense against and adaptation to high Hg levels exist.     

Difference in the Use of a Quartz Filter and a PTFE Filter as First-Stage Filter in the Four-Stage Filter-Pack Method

We evaluated the differences in the use of a quartz filter and a polytetrafluoroethylene (PTFE) filter as a first (F0)-stage filter in a four-stage filter-pack method. A four-stage filter-pack method can completely collect sulfur species (SO₂ and SO ₄ ^2? ), nitrate species (HNO₃ and NO ₃ ^? ), and ammonium species (NH₃ and NH ₄ ⁺ ) with little or no leakage irrespectively of the first-stage filter used. On the other hand, a seasonal variation was observed in the efficiency of collection between the quartz filter and the PTFE filter depending on the material to be collected. There was no seasonal variation in the efficiency of collection in sulfur species; in contrast, a clear seasonal variation was observed for the nitrate and ammonium species. As for NO ₃ ^? , the PTFE filter was more vulnerable than the quartz filter at air temperatures below 21°C, while the quartz filter was more vulnerable than the PTFE filter at air temperatures exceeding 21°C. A similar vulnerability for air temperature was observed for NH ₄ ⁺ , although the threshold air temperature was 23°C for NH ₄ ⁺ . Consequently, the evaporation loss of NO ₃ ^? would be mainly attributable to the volatilization of NH₄NO₃, although it is also partially due to the volatilization of NH₄Cl.     

大中型拖拉机需求量混沌特征分析及预测时效研究

中国大中型拖拉机需求量是一个复杂的非线性系统。该文在分析大中型拖拉机需求特点的基础上,建立了基于混沌理论的农业装备需求特性分析及预测时效模型。采用中国1952至2004年大中型拖拉机需求量的实测数据,重点研究了其需求系统的相空间重构、关联维数的确定和柯尔莫哥洛夫熵的计算。结果表明：中国大中型拖拉机需求为混沌系统,影响需求量的因素有1～12个,最大可预测的时效为8a。     

Foliar Nitrogen Uptake from Wet Deposition and the Relation with Leaf Wettability and Water Storage Capacity

This study assessed the foliar uptake of ¹⁵N-labelled nitrogen (N) originating from wet deposition along with leaf surface conditions, measured by wettability and water storage capacity. Foliar ¹⁵N uptake was measured on saplings of silver birch, European beech, pedunculate oak and Scots pine and the effect of nitrogen form (NH ₄ ⁺ or NO ₃ ^? ), NH ₄ ⁺ to NO ₃ ^? ratio and leaf phenology on this N uptake was assessed. Next to this, leaf wettability and water storage capacity were determined for each tree species and phenological stage, and the relationship with ¹⁵NH ₄ ⁺ and ¹⁵NO ₃ ^? uptake was examined. Uptake rates were on average five times higher (p?<?0.05) for NH ₄ ⁺ than for NO ₃ ^? and four times higher for deciduous species than for Scots pine. Developing leaves showed lower uptake than fully developed and senescent leaves, but this effect was tree species dependent. The applied NH ₄ ⁺ to NO ₃ ^? ratio did only affect the amount of N uptake by senescent leaves. The negative correlation between measured leaf contact angles and foliar N uptake demonstrates that the observed effects of tree species and phenological stage are related to differences in leaf wettability and not to water storage capacity.     

Nitrate reduction coupled with microbial oxidation of sulfide in river sediment

Purpose

Nitrate (NO ₃ ^? ) is often considered to be removed mainly through microbial respiratory denitrification coupled with carbon oxidation. Alternatively, NO ₃ ^? may be reduced by chemolithoautotrophic bacteria using sulfide as an electron donor. The aim of this study was to quantify the NO ₃ ^? reduction process with sulfide oxidation under different NO ₃ ^? input concentrations in river sediment.

Materials and methods

Under NO ₃ ^? input concentrations of 0.2 to 30?mM, flow-through reactors filled with river sediment from the Pearl River, China, were used to measure the processes of potential NO ₃ ^? reduction and sulfate (SO ₄ ^2? ) production. Molecular biology analyses were conducted to study the microbial mechanisms involved.

Results and discussion

Simultaneous NO₃ ^? removal and SO₄ ^2? production were observed with the different NO ₃ ^? concentrations in the sediment samples collected at different depths. Potentially, NO ₃ ^? removal reached 72 to 91?% and SO ₄ ^2? production rates ranged from 0.196 to 0.903?mM?h^?1. The potential NO ₃ ^? removal rates were linearly correlated to the NO ₃ ^? input concentrations. While the SO ₄ ^2? production process became stable, the NO ₃ ^? reduction process was still a first-order reaction within the range of NO ₃ ^? input concentrations. With low NO ₃ ^? input concentrations, the NO ₃ ^? removal was mainly through the pathway of dissimilatory NO ₃ ^? reduction to NH ₄ ⁺ , while with higher NO ₃ ^? concentrations the NO ₃ ^? removal was through the denitrification pathway.

Conclusions

While most of NO ₃ ^? in the sediment was reduced by denitrifying heterotrophs, sulfide-driven NO ₃ ^? reduction accounted for up to 26?% of the total NO ₃ ^? removal under lower NO ₃ ^? concentrations. The vertical distributions of NO ₃ ^? reduction and SO ₄ ^2? production processes were different because of the variable bacterial communities with depth.     

Effect of an attendant anion on the balance of cations in the soil-solution system with an ordinary chernozem as an example

The effect of different anions on the balance of heavy metal cations in the soil-solution system has been assessed under model laboratory conditions. It has been found that the uptake of the Cu, Zn, and Pb cations by an ordinary chernozem from solutions of different salts is accompanied by the displacement of the exchangeable cations to the solution in the following order: Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. The sum of the displaced exchangeable cations in most cases exceeds the amount of the adsorbed heavy metal cations. According to the effect of the anions on the displacing capacity of the metal cations, the following series are formed: for copper, SO ₄ ^2? ? Cl^? > OAc^? > NO ₃ ^? ; for lead, Cl^? ? NO ₃ ^? > OAc^?; and, for zinc, SO ₄ ^2? ? Cl^? ? OAc^? > NO ₃ ^? .