河套平原典型县域耕地土壤养分空间变异特征研究

为研究河套平原地区土壤养分状况,探究县域尺度土壤养分的空间变异性与分布特征,以杭锦后旗县域耕地为对象,采用实地调查和地统计学相结合的方法,研究该区耕层土壤有机质、全氮、有效磷、速效钾养分含量状况,分析土壤养分空间分布及其变异特征。结果表明,研究区耕层土壤有机质、全氮、速效磷和速效钾平均含量依次为13.90 g/kg、0.93 g/kg、16.25 mg/kg和170.79 mg/kg,土壤有机质和全氮处于缺乏状态,速效磷含量中等,而速效钾的含量较为丰富。从空间变异及相关性看,各土壤养分的变异程度都为中等变异,有机质和速效钾为中等相关性,全氮和有效磷均为弱相关性。从空间分布格局看,土壤有机质与全氮分布规律相近,呈现西北部高、东南部和东北部低的特点;土壤速效钾整体分布较为均衡;速效磷空间差异明显,呈东高西低格局。针对该地区土壤养分含量及分布规律,在进行养分管理过程中,应以控氮、稳磷、稳钾、全区规划与重点应对相结合的原则,坚持以有机肥为主、有机与无机相结合的施肥策略。对县域尺度耕地土壤养分状况的调查研究和统计分析,明晰了区域土壤养分空间分布特征及其与土地利用方式之间的关系,为河套平原耕地土壤养分管理、地力培育以及合理施肥运筹等提供科学依据。     

Implementation of an easily reconfigurable dynamic simulator for recirculating aquaculture systems

Methodology of Programmable Process Structures has been implemented and applied for the flexible automatic generation and simulation of Recirculating Aquaculture Systems. First, we implemented and validated the model for a pilot unit, based on short time experiments with Common carp (Cyprinus carpio), utilizing data and functionalities from the literature. Afterwards, starting from this model we generated a hypothetical single tank model of simulated increasing volume, to demonstrate how it supports the simplified, preliminary analysis, design and control of the possible multi-stage systems. We showed that the simulation of a single tank with an appropriately increasing volume makes possible to study the various control strategies, as well as to design the structure and the grading strategy of the multi-stage systems, without an increased combinatorial complexity. In the knowledge of the simulated increasing volume, we determined the volumes of subsequent stages by equidistant partitioning of the rearing time, algorithmically. Considering the available (or planned) tank volumes, this method makes possible to design a multi-stage system that approximately corresponds to the previously optimized single tank model. This conclusion was illustrated by the generation and simulation of the model for the respective multi-stage system.     

油梨嫁接苗分级标准探讨

通过逐步聚类分析方法，初步探讨了油梨嫁接苗的分级标准。分析得出以苗高和茎粗为油梨嫁接苗的分级质量指标，将油梨嫁接苗分为三级，即Ⅰ级苗：苗高≥74cm，茎粗≥1.13cm；Ⅱ级苗：74cm＞苗高≥66 cm，1.13cm＞茎粗≥0.93cm；Ⅲ级苗：苗高＜66cm，茎粗＜0.93cm。     

果品分级技术研究的现状及展望

通过有效的检测，及时解决虫害或机械造成的损伤，从而减轻果品之间病虫害的传播，同时 还需要对残次品进行处一定理，以确保成本的有效降低，达到全面提高我国果品的品质，增加国际市 场的竞争力。基于此，本文主要讨论了果品分级技术的落实现状以及发展情况。     

美国油气管道基本失效概率评估方法及启示

为充分利用油气管道历史失效数据,减少失效概率评估过程中的主观性,提出油气管道基本失效概率的概念及评估方法。对美国管道及危险物品安全管理局数据库的油气管道里程数据、事故数据及失效因素数据进行全面分析,采用基于事故统计的方法评估油气管道基本失效概率。结果表明:美国危险液体管道、输气集气管道、配气管道发生一般事故的基本失效概率分别为1.29次/(10^3 km·a)、2.17次/(10^4 km·a)及4.08次/(10^5 km·a),发生较大事故的基本失效概率分别为4.58次/(10^4 km·a)、1.41次/(10^4 km·a)及2.38次/(10^5 km·a),发生重大事故的基本失效概率分别为9.09次/(10^6 km·a)、9.79次/(10^6 km·a)及1.11次/(10^5 km·a)。美国基本失效概率可作为油气管道失效概率评估的基准线,也可作为风险可接受标准的依据,但不能直接应用于中国管道风险评价,需对其进行修正,建立适用于中国管道的失效数据库。     

Log Characteristics and Sawn Timber Recovery of Home-Garden Teak from Wet and Dry Localities of Kerala, India

There is a widely held view among smallholders that teak timber produced from small-scale agroforestry systems, especially home-garden forestry, fetches a lower price than that from conventional plantation forestry. To examine the veracity of this view, the wood quality attributes of teak from two home gardens in the district of Ernakulam (wet site) and Palakkad (dry site) in India were compared to those of forest plantation in Nilambur. The logs were graded using standard timber trade practices into high, medium and low quality as determined by the potential sawn timber grade-yield recovery pattern. Of 96 home garden teak logs (aged 35 years) from wet and dry sites, 59% belonged to timber Grade II–IV and the rest were classified as poles. Grade I logs (export quality) with a girth above 150 cm were not available from either of the homesteads. Faster-grown teak in the wet site produced large diameter logs (dbh 1.37 m) with average diameter of 39.6 cm, which is comparable to that of best site quality in India. In contrast, the average dbh for teak grown in the dry site was 24 cm as compared to the average dbh of 31 cm recorded from the same aged forest plantation in Nilambur. It was found that only 10% of logs belonged to Grade II timber and the rest fell under grades III and IV with more frequent visual defects. The sawn timber recovery percentage was lower for the dry site (66.8%), whereas there was no significant difference in grade from the wet and forest plantation sites, with recovery rates of 76.5% and 78.8%, respectively. The general notion that home garden teak has a large proportion of sapwood seems to be baseless, no significant difference being found between the heartwood-sapwood ratio of home-garden and forest plantation teak. Lack of appropriate silvicultural practices in home-garden forestry caused the production of more defective logs, adversely affecting the market price of timber.

Economic evaluation of forest drainage and fertilization in northern Ontario peatlands with an investment decision model

Drainage and fertilization of an existing peatland black spruce (Picea mariana (Mill.) B.S.P.) stand and 24 possible methods of planting a clear-cut area near Cochrane, Ontario were evaluated by means of a recently developed forestry investment decision model, FIDME.Results indicate that, on the basis of the cost estimates used and assumptions made, drainage of the existing stand is the most economical treatment if it can reduce the rotation age by 30 years or more. Drainage combined with fertilization is the second best alternative if this treatment can reduce the rotation age by 40 years or more. Fertilization of the undrained site ranks a distant third, and then only if it reduces the rotation age by 10 years; otherwise, it will be uneconomical to apply.In the case of the clear-cut area, planting bare-root stock on a mechanically prepared but undrained site without weed control ranked first among the 24 alternatives considered; the same treatment, but with weed control included, ranked second. Planting containerized seedlings on a mechanically prepared but undrained site with weed control ranked third, followed by planting bare-root stock on a mechanically prepared and drained site with weed control. In contrast, planting containerized seedlings on an unprepared site and with no weed control ranked as the least cost-effective method considered.     

黄枝油杉种苗质量分级标准研究

黄枝油杉由于其分布区狭窄,繁殖速度慢,资源少,是国家二级保护植物。为了更好地保护其种质资源,通过实验研究种苗质量分级标准。分别对2年生和4年生的黄枝油杉种苗性状特征描述,以地径和株高作为主要分级标准代表,运用Excel 2003和SPSS 26.0对种苗特征数据进行统计学相关分析、主成分分析、K均值聚类分析,将其种苗分别2年生和4年生分别分成了三级。2年生一级株高＞20 cm,冠幅＞11 cm,地径≥0.10 cm;4年生一级株高＞127 cm,冠幅＞56 cm,地径≥0.80 cm。2年生二级株高14~20 cm,冠幅8~11 cm,地径≥0.10 cm;4年生二级株高96~127 cm,冠幅38~56 cm,地径≥0.80 cm;2年生三级株高＜14 cm,冠幅＜8 cm,地径≥0.10 cm;4年生三级株高＜96 cm,冠幅＜38 cm,地径≥0.80 cm。     

The critical stress in various stress levels of bending member on fire exposure for mechanical graded lumber

This study focused on the relationship between stress level and the fire resistance of structural lumber. The 210 samples were prepared from 15-year-old trees of Acacia mangium from the Forest Estate Plantation, Indonesia. Specimens were 20 ® × 20 (T) × 500mm (L) and were air-dried. Sixty samples were tested under four-point bending stress to obtain the modulus of elasticity (MOE) and the modulus of rupture (MOR) for classifying the stress grades of the remaining 150 samples. The tests were performed using a four-point load bending position at various stress level while the specimens were exposed to fire along the shear-free region. Time to failure was affected by the stress levels in an exponential trend. Despite changes in stress level, charring rate, and time to failure, the critical stress of a member from the same species was similar. The fire performance under applied load could be predicted by using simplified fire-testing methods. The developed testing apparatus is valid for evaluating the small-scale fire resistant behavior of structural lumber in bending.     

黄河兰州段多环芳烃生态风险的初步评价

以黄河兰州段11个不同采样点3种多环芳烃的临测浓度及其对6～38种水生生物的LC50为基础资料,分别应用商值法、概率密度函数重叠面积和联合概率曲线3种风险浮价方法对黄河兰州段苯并(a)芘、荧蒽、芘的生态风险进行了评价.结果表明:黄河兰州段3种PAHs残留具有一定的生态风险.其中低暴露风险条件下(受威胁生物不超过1%),...