Constraint Factor Research Articles

Process analysis and optimization of simultaneous saccharification and co-fermentation of ethylenediamine-pretreated corn stover for ethanol production

BackgroundImproving ethanol concentration and reducing enzyme dosage are main challenges in bioethanol refinery from lignocellulosic biomass. Ethylenediamine (EDA) pretreatment is a novel method to improve enzymatic digestibility of lignocellulose. In this study, simultaneous saccharification and co-fermentation (SSCF) process using EDA-pretreated corn stover was analyzed and optimized to verify the constraint factors on ethanol production.ResultsHighest ethanol concentration was achieved with the following optimized SSCF conditions at 6% glucan loading: 12-h pre-hydrolysis, 34 °C, pH 5.4, and inoculum size of 5 g dry cell/L. As glucan loading increased from 6 to 9%, ethanol concentration increased from 33.8 to 48.0 g/L, while ethanol yield reduced by 7%. Mass balance of SSCF showed that the reduction of ethanol yield with the increasing solid loading was mainly due to the decrease of glucan enzymatic conversion and xylose metabolism of the strain. Tween 20 and BSA increased ethanol concentration through enhancing enzymatic efficiency. The solid-recycled SSCF process reduced enzyme dosage by 40% (from 20 to 12 mg protein/g glucan) to achieve the similar ethanol concentration (~ 40 g/L) comparing to conventional SSCF.ConclusionsHere, we established an efficient SSCF procedure using EDA-pretreated biomass. Glucose enzymatic yield and yeast viability were regarded as the key factors affecting ethanol production at high solid loading. The extensive analysis of SSCF would be constructive to overcome the bottlenecks and improve ethanol production in cellulosic ethanol refinery.

Experimental evaluation of nanoindentation as a technique for measuring the hardness and Young’s modulus of Zircaloy-2 sheet material

Experiments have been performed on a Zircaloy-2 sheet material to evaluate nanoindentation as a technique for measuring the Young’s modulus and hardness of the nuclear material. Room temperature transverse and longitudinal mechanical properties of an unirradiated Zircaloy-2 sheet material were measured with nanoindentation. The results were compared with those of tensile testing and Vickers microindentation obtained on the same material. Anisotropy evaluated with the conventional methods of microhardness measurement and tensile testing could be accurately confirmed by the nanoindentation measurement technique. The results show that the nanoindentation technique can be used to measure the Young’s modulus and hardness of small-volume samples of the material. The constraint factor, employed for converting hardness to yield strength, has also been determined and is reported for the material.

Planning the next-generation biofuel crops based on soil-water constraints

Widely blended in the transportation fuels, biofuels have been generally regarded as indispensable components in the U.S. national energy portfolio. Although the current production of cellulosic biofuels has been staggering at pilot scales, it is expected that large-scale cultivation of cellulosic biofuel crops may occur when techniques for cost-effective bioconversion of lignocellulosic biomass to ethanol are available. However, it is still unclear if enough land is in existence to accommodate potential large-scale lignocellulosic crops development without negative effects on the environment and food market. The appropriate land use for the next-generation biofuel crops should be planned and allocated in a manner that the competitive use of land dedicated to food and energy production and other side effects could be minimized. This research proposes an approach of identifying the potential available land for planting switchgrass in the U.S. Midwest using a GIS-based multi-criteria analysis that combines soil and water constraint factors. The results showed that land areas of approximately 13.6 million ha are unsuitable for profitable food crops but available for switchgrass cultivation in 7 U.S. Great Plains states. The findings can assist decision-makers in formulating land use policies and related environmental management strategies.

An experimental-finite element method based on beach marks to determine fatigue crack growth rate in thick plates with varying stress states

The relation between the fatigue crack growth rate and stress state is significant for fatigue life estimation, especially for thick-welded structures with complex stress states. This paper proposes a hybrid Experimental-Finite Element Method aimed to obtain the fatigue crack growth rate corresponding to plane stress and plane strain states. A static load marking method is proposed to mark a series of crack fronts in a single edge notched bending specimen at known numbers of cycles, which is analysed by nonlinear finite element method to evaluate the stress state by a local constraint factor. Stress intensity factor at the center of the thickness and the surface position where plane strain and plane stress states approximately exist and remain unchanged with crack propagation, is calculated by the 1/4-node displacement method with consideration of non-orthogonal mesh influence. The J-integral method and the virtual crack closure technique are also applied to check the performance of the methods in dealing with the actual cracked body problem. Crack length increments are determined based on the crack front profiles. The da/dN-ΔK curves of plane strain and plane stress states are determined and compared with the results from normal fatigue crack growth rate tests according to Chinese standard: GB/T 6398-2000. The fatigue crack growth behavior of a semi-elliptical surface crack located at the weld toe of a T-plate welded joint subjected to cyclic tension loading is assessed based on the curves and the analytical results are compared with the experimental results. The asymptotic crack shape observed in experiments is successfully predicted by using the curves determined by the hybrid method.

Optimization of BI test parameters to investigate mechanical properties of Grade 92 steel

The ball indentation (BI) testing is used to evaluate the tensile properties of materials namely yield strength, strength coefficient, ultimate tensile strength, and strain hardening exponent. The properties evaluated depend on a number of BI test parameters. These parameters include the material constants like yield slope (YS), constraint factor (CF), yield offset parameter (YOP). Number of loading/unloading cycles, preload, indenter size and depth of penetration of indenter also affects the properties. In present investigation the effect of these parameters on the stress-strain curve of normalized and tempered Grade 92 steel is evaluated. Grade 92 is a candidate material for power plant application over austenitic stainless steel and derives its strength from M23C6, MX precipitates and high dislocation density. CF, YS and YOP changed the strength properties considerably. Indenter size effect resulted in higher strength for smaller indenter. It is suggested to use larger indenter diameter and higher number of loading cycles for GRADE 92 steel to get best results using BI technique.

Essential refinements of spherical nanoindentation protocols for the reliable determination of mechanical flow curves

Understanding and linking mechanical properties obtained by spherical indentation experiments to uniaxial data is extremely challenging. Since the first attempts in the early 20th century numerous advances gradually allowed to expand the output of indentation tests. Still, the extraction of flow curves from spherical nanoindentation has not yet been fully established, as tip shape problems and size effects impede a straight-forward implementation. Within this study, we show new calibration procedures originating from fundamental geometrical considerations to account for tip shape imperfections. This sets the base for strain-rate controlled tests, which in turn enables us to measure rate-dependent material properties either with constant strain-rate or by strain-rate jump tests. Finally, experimental evaluation of the constraint factor in consideration of the mechanical properties and induced strain enables the extraction of flow curves. Testing materials with refined microstructures ensures the absence of possible size-effects. This study contributes to a significant improvement of current experimental protocols and allows to move flow curve measurements from single spherical imprints one step closer to its implementation as a standard characterization technique for modern materials.

Dynamics of N-NH4+, N-NO3-, and total soil nitrogen in paddy field with azolla and biochar

Nitrogen (N) is one of macronutrients which is dynamic in the soil and becomes constraint factor for rice crops. The addition of nitrogen fertilizers and its absorption in paddy field causes the dynamics of nitrogen, thus declines of N absorption efficiency. The aim of this research is to know influence Azolla, biochar and different varieties application on N-NH4+, N-NO3-, and total soil N in paddy field. This research was conducted in a screen house located in Jumantono Laboratory, Faculty of Agriculture, Universitas Sebelas Maret (UNS) with altitude 170 m asl from April to June 2016. Treatment factors that were examined consisted of azolla (0 and 10 tons/ha), biochar (0 and 2 tons/ha), and rice varieties (Cisadane, Memberamo, Ciherang, IR64). The results of this research showed that there was no interaction between azolla, biochar and varieties. Nevertheless, azolla treatment with dose of 10 tons/ha increased soil NH4+ content (41 days after planting, DAP) by 13.4% but tend to decrease at 70 and 90 DAP. Biochar treatment with dose of 2 ton/ha increases NO3- soil content (70 DAP) by 1.7% but decreases total N soil by 5.8% (41 DAP) and 4.7% (90 DAP). Different rice varieties generated different soil NH4+ content (41 DAP) and rice root volume. Cisadane variety can increase soil NH4+ content (41 DAP) by 52.08% and root volume by 51.80% (90 DAP) compared with Ciherang variety. Organic rice field management with azolla and biochar affects the availability of N in the soil and increase N absorption efficiency through its role in increasing rice root volume.

사회 연결망 분석을 통한 개별관광객의 관광지 접근성 분석

This study examines public transit, which is one of the constraint factors for tourism activities. The centrality of the network of bus routes near Ulsan destinations were examined through social network analysis to confirm the mobility environment of tourists. The network of bus routes was visualized to identify weaknesses involving tourism destinations by using the bus routes listed in the “Ulsan Metropolitan City Bus Route Guide.” Centrality was analyzed using UCINET and the bus networks using Netdrew. First, it was confirmed that social network analysis is useful as a methodology for research on tourism transit systems related to the mobile environment of individual tourists. Second, it was confirmed that visualization of the bus network is useful for bus route analysis and improvement. Third, it was confirmed that the number of accessible destinations using bus routes is limited, so tourism activities are also limited. Traffic-related research should jointly consider temporal and spatial characteristics. However, this study considered only spatial characteristics, so further research should also consider temporal characteristics.

Three-dimensional analysis of an edge crack in a plate of finite thickness with the first-order plate theory

In this paper, plasticity effects at the tip of an edge through-the-thickness crack are investigated by invoking the strip-yield model and the first order plate theory. The latter theory is the simplest extension of the classical plane theories of elasticity, which is capable of accounting for three-dimensional effects and, in particular, the plate thickness effect. By utilising the distributed dislocation technique, new results are obtained on the interaction of the free boundaries (free edge and free plate planes) with the crack tip plasticity region. Numerical results for the crack tip opening displacement and global constraint factor are first presented at various crack length to plate thickness and applied stress to yield stress ratios. The results are validated against past 3D solutions for an embedded crack as well as analytical solutions obtained under the plane stress or plane strain assumption. The new model and results can be utilised in advanced fracture and fatigue analyses of cracks emanating from a free surface.

RNA 3-dimensional structural motifs as a critical constraint of viroid RNA evolution.

Viroids are circular noncoding RNAs infecting plants [1, 2]. During infection, viroids, like RNA viruses, generate swarms of sequence variants called quasispecies [3, 4]. Viroids in Avsunviroidae family replicate in chloroplasts and display the highest mutation rates among all living entities [5]. Viroids in Pospiviroidae family replicate in the nucleus with a relatively lower mutation rate resembling some RNA viruses [6]. Those sequence variants generated during replication are described by the concept of sequence space, which harnesses a geometric representation to illustrate genetic similarities via physical distances. Given the high mutation rate and fast propagation, viroid RNAs have a potentially large sequence space for the evolution of new variants. However, in reality, they use only a small fraction of this space. Constraints of viral sequence space may include genome size, replication fidelity, error thresholds, host or tissue tropism, etc. These factors have been nicely reviewed elsewhere [3, 7, 8] and are not the focus of this Pearl. In addition, RNA secondary structures have been considered, though not adequately, as a constraint factor [8]. Viroids, in contrast to viruses, entirely rely on their RNA structural motifs for function due to their noncoding nature, which offers insights into their capacity to explore regions of sequence space influenced by RNA structures. Here, we describe that 3-dimensional (3D) structural motifs formed by non–Watson-Crick (non-WC) base pairs in viroid RNAs act as a critical constraint for the sequence space of viroid genome evolution. This constraint operates because RNA 3D motifs can play crucial roles by mediating (1) RNA–RNA interactions for the folding of a part or a whole of RNA into a distinct tertiary conformation and (2) RNA–protein interactions. Therefore, mutations in a 3D motif that do not disrupt the structure and function will be retained in the population, whereas mutations that disrupt the 3D structures of motifs, and consequently the function, will be lost.

PELAKSANAAN PENDIDIKAN KARAKTER DI MADRASAH ALIYAH NEGERI 2 PALEMBANG

Moral degeneration has become a common phenomenon that plagues mankind in various parts of the world today, including in Indonesia. Various moral cases have occurred and adorned mass media almost all the time, ranging from cases of corruption, acts of violence, sexual harassment, pornography, prostitution, drug abuse, even murder. Since 2010 the Center for Curriculum and Bookkeeping has initiated a pioneering program of character education implementation in several districts / cities in all provinces in Indonesia.This study uses a combination of quantitative and qualitative approaches. The data were collected using interviews and questionnaires. Data analysis is done descriptively in order to explain / describe the implementation of character education and the factors that become obstacles of its implementation.In this research can be concluded that character education in MAN 2 Palembang has not been implemented maximally. Some things that have not been implemented related to the implementation of character education are: not all contextual learning strategies used, not all teachers use contextual learning strategies, there has been no specific effort to revitalize the activities of co-curricular and extra curricular, related to the integration of teachers in learning, there are still 33.33 % of teachers are doing poorly (20.8% are poor in learning planning, 25% on learning implementation aspects, and 4.2% on learning assessment aspects). Many factors constraints and support the implementation of character education in MAN 2 Palembang. The obstacles faced by the madrasah include: difficulty in carrying out routine activities, difficulties in performing spontaneous activities, and difficulties in conducting conditioning activities. While the constraints factor from the teacher side is the difficulty of integrating character education in the learning process, which include: difficulties linking character education with materials, methods, strategies, and learning media, difficulty determining the value of character to be achieved, difficulty measuring the attainment of character education in participants students, too many students per class, not all teachers and employees can be role models, the number of things that affect the character, as well as the many aspects of character that must be developed. While the factors supporting the implementation of character education in MAN 2 Palembang include: support of all madrasah residents, family environment, madrasah infrastructure facilities, budget, student association, and student motivation.

Evaluation on the development degree of China’s seven pilot carbon markets

China is preparing to establish a nationwide carbon market in 2017, and in order to facilitate this goal, seven pilot carbon markets have been under study for the past few years. This paper summarizes the operation experience and challenges of the seven pilot carbon markets in China. It has been widely accepted that the essence of a carbon market is to solve environmental problems through market mechanisms, with environmental benefit being the fundamental purpose, market mechanism being the key measure, and policies and regulations being an important guarantee for an orderly carbon market. Therefore, this paper constructs an evaluation index system composed of 34 detailed sub-indexes in three dimensions, such as environmental constraint force, market resource allocation ability, and supporting policies and facility completeness. Through analyzing the operation data from 2013 to 2016, the weights of the sub-indexes are obtained. In addition, the study obtains experts’ opinions from over 10 carbon permits exchanges, consultancy firms and research institutions in China, and conducts a comprehensive evaluation on the development degree of the seven pilot carbon markets. Results show that the pilot carbon markets that include private SMEs as the covered entities for emissions control present relatively higher environmental constraint force. But too many covered entities could increase the difficulty of market performance management, while the pilots that include high energy-consuming state-owned enterprises as the entities for emissions control demonstrate a phenomenon of “high market compliance rate with low trading volume”. The resource allocation capability of China’s carbon market has not been effectively brought into play, and low degree of market participation has become an important constraint factor for market development. Due to the lack of laws and regulations at the national macro-level, the legally binding force of the pilot markets construction is obviously insufficient, and the supporting policies are lacking foresights. Generally, the development of China’s pilot carbon markets is still in such a fragmented state as in the aspects of environment, market and policy development, and the market operation has not yet achieved the purpose of solving environmental problems through market mechanisms. Accordingly, policy recommendations pointed out by this study are that tightening the allowance of free quota and progressively increasing the auction proportion, improving legal construction, increasing the services and products of carbon finance and standardizing the order of market transactions, enhancing capacity building of local governments and promoting the participation willingness and capability of emissions control entities, will be necessary.

Representative Stress‐Strain Curve by Spherical Indentation on Elastic‐Plastic Materials

Tensile stress‐strain curve of metallic materials can be determined by the representative stress‐strain curve from the spherical indentation. Tabor empirically determined the stress constraint factor (stress CF), ψ, and strain constraint factor (strain CF), β, but the choice of value for ψ and β is still under discussion. In this study, a new insight into the relationship between constraint factors of stress and strain is analytically described based on the formation of Tabor’s equation. Experiment tests were performed to evaluate these constraint factors. From the results, representative stress‐strain curves using a proposed strain constraint factor can fit better with nominal stress‐strain curve than those using Tabor’s constraint factors.

孑遗植物长苞铁杉(Tsuga longibracteata)分布格局对未来气候变化的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 孑遗植物长苞铁杉(Tsuga longibracteata)分布格局对未来气候变化的响应 DOI: 10.5846/stxb201806021236 作者: 作者单位: 中国科学院成都生物研究所,中国科学院成都生物研究所,中国科学院成都生物研究所,中国科学院成都生物研究所,中国科学院成都生物研究所,中国科学院成都生物研究所,中国科学院成都生物研究所,中国科学院成都生物研究所,中国科学院成都生物研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0502101） The suitable distribution area of Tsuga longibracteata revealed by a climate and spatial constraint model under future climate change scenarios Author: Affiliation: Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences,Chengdu Institute of biology, Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:长苞铁杉（Tsuga longibracteata）是中国特有的珍贵树种，不仅对研究裸子植物的系统发育、古生态和古气候具有重要作用，而且该树种具有造林、用材和药用等方面的较高价值。研究长苞铁杉在气候变化下的分布格局变化是制定其保护和可持续利用的重要基础。采用最大熵模型（MaxEnt），结合不同时期（当前、2050年和2070年）和不同二氧化碳排放情境下（RCP2.6和RCP8.5）的气候因子变量，探讨气候变化与物种地理分布格局的关系，预测长苞铁杉的潜在分布区变迁。本研究考虑了空间约束对物种分布的限制作用，构建了气候因子预测模型（C）和气候+空间约束因子预测模型（C+S）分别进行潜在分布区预测，比较其结果差异。结果显示，最干月降水量和温度年较差是影响长苞铁杉地理分布的主导气候因子，空间约束因子对长苞铁杉未来的地理分布有重要影响。随时间年限增加，长苞铁杉总潜在适生区面积降低，特别是中高等级的适生区面积有不同程度地减少，分布范围总体向北移动，这些变化趋势在RCP8.5情境下更加突出。这一结果表明未来气候变化会导致长苞铁杉种群分布范围收缩和生境适宜度下降，加剧其受胁程度。加入空间约束因子后，C+S模型的预测精度更高，结果更符合长苞铁杉的迁移、扩散特性。长苞铁杉未来的核心分布区仍位于现存的湘、桂、黔结合部，表明其具有"原地避难"的特性，应进一步加强对现有野生资源的保护。渝、川、鄂结合部的大巴山等地区是未来气候变化下长苞铁杉的理论分布区域，可作为长苞铁杉应对未来气候变化的引种地区，应提早进行人工引种、栽培等前期研究。研究结果可为气候变化背景下长苞铁杉的保护、物种迁地保存和可持续管理提供科学依据，也可为准确预测濒危、珍稀植物的地理分布范围提供方法参考。 Abstract:Tsuga longibracteata is a unique, precious, relic tree species in China, which has been used for afforestation, as well as timber and medicine. Further, the plant is worth studying because it is important in the study of phylogeny of gymnosperms, paleoecology, and the Paleoclimate. Predicting changes in suitable distribution areas of Tsuga longibracteata under climate change scenarios are an important basis for formulating its conservation and development strategy. In this study, the Maximum Entropy Model (MaxEnt) was used to explore the relationship between climate change and the geographical distribution of the species in different time periods (current, 2050, and 2070) and carbon dioxide emissions (RCP2.6 and RCP8.5), to predict the changes in the suitable distribution areas of Tsuga longibracteata. In addition, the spatial constraints on species distribution were considered, and the climate factor prediction model (C) and climate + spatial constraint factor prediction model (C+S) were respectively used to predict the changes in potential distribution areas of the tree. The results showed that the precipitation for the driest month and the annual temperature range were the dominant climatic factors affecting its geographical distribution with spatial constraints on having some important influences. With the increase in time, the total suitable distribution area of the tree was reduced, especially the most and more suitable distribution areas decreased greatly and shifted towards the north, which were more prominent trends in RCP 8.5 scenario. Our findings indicated that future climate change may lead to shrinkage of the Tsuga longibracteata population and decreased its suitable habitat area; thus, increasing threats to its population. On adding the space constraint factor in the model, the prediction accuracy of the C+S model was higher, and the results more strongly fit with the migration and diffusion characteristics of the tree. The core distribution area in the future was still located at the junction of the three provinces in Hunan, Guangxi, and Guizhou, where the tree is currently distributed, indicating the junction is a refuge place for the tree in the future climate changes. In addition, the Daba mountain area in combination with the Chongqing, Sichuan, and Hubei are the theoretical distribution area of Tsuga longibracteata in the future under climate change. They can be used as new introduction culture areas of the tree under the future climate change. The results provided a scientific basis for the conservation and sustainable management of the species in the context of the climate change, and a case integrating spatial constraint into a climate model for species distribution prediction, which will benefit accurate prediction of the geographical distribution of endangered and rare plants. 参考文献 相似文献 引证文献

Thickness Effect Analysis on Fatigue Crack Propagation of 7475 Plate Material under Variable Amplitude Loading

In the crack growth prediction models, the effect of variable amplitude loading is taken into account by different ways. One of them the Newman’s model is used very often, but in its original form it is not able to take into account the effect of specimen thickness. The new modification which involves the specimen thickness is presented. The study of variable thickness impact is based on the FE – analysis of M(T) specimen. The variability of constrained factor α was analysed for several load levels and specimen thicknesses. The value of α is governed by the ratio of thickness B versus plastic zone size rp. The effect of overloads on the plastic zone and relevant constraint factor value is analysed as well. During loading, it was found, that the constraint factor value is lower after overloads than when creating monotonic plastic deformation on the same load level in a large part of the cycle. The influence of thickness effect based on different α value after overload was successfully implemented into the strip yield model. Simulation of crack growth taking into account the thickness of the specimen under variable amplitude loading shows similar behaviour like the experimental data.

An Evaluation of Implementation of Quality Management System ISO 9001:2008 on Contractor for Six Senses Uluwatu Villa Resort Bali Project

The project quality management system is a necessary process to ensure that the project would be executed has guaranteed quality system according to expectations and needs. An evaluation of quality management systems of ISO 9001:2008 series studied on contractor in Indonesia. As case study on PT Hutama Karya contractor for Six Senses Uluwatu Villa Resort Bali project. The execution was achieved by using a research instrument in the form of a checklist. A factor that becomes an obstacle in the implementation was obtained through observation, interview and verify documents of related staff. Assessment of the implementation of ISO 9001:2008 are clause 4, clause 5, clause 6, clause 7, and clause 8 is obtained by qualitative descriptive statistical analysis method, using audit score methods developed with rating measurement scale. Data analysis results can be categorized as very good with the percentage of 93.13%. The implementation level of the 4th clause, quality management system of 90.00% included in the category is very good. The implementation level of the 6th clause, management of resources of 91.76% is included in the very good category. The implementation level of the 7th clause, product realization of 93.33% is included in the very good category. The implementation level of the 8th clause i.g. measurement, analysis and improvement of 94.00% is categorized as very good. The 5th clause becomes the element that gets the highest score with the percentage of 96.25%. The 4th clause becomes the element with the lowest value with a percentage of 90.00%. Implementation has not reached 100% due to labor factor. Labor factor results in the emergence of another constraint factor such as documentation.

内陆盐沼芦苇根系形态及生物量分配对土壤盐分因子的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 内陆盐沼芦苇根系形态及生物量分配对土壤盐分因子的响应 DOI: 10.5846/stxb201707141283 作者: 作者单位: 西北师范大学地理与环境科学学院，甘肃省湿地资源保护与产业发展工程研究中心,西北师范大学地理与环境科学学院，甘肃省湿地资源保护与产业发展工程研究中心,西北师范大学地理与环境科学学院,西北师范大学地理与环境科学学院,西北师范大学地理与环境科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41461013，91125014）；甘肃省生态学重点学科基金项目资助 Response of root morphology and biomass of Phragmites australis to soil salinity in inland salt marsh Author: Affiliation: Research Center of Wetland Resources Protection and Industrial Development Engineering of Gansu Province, College of Geography and Environmental Science, Northwest Normal University, Lanzhou,Research Center of Wetland Resources Protection and Industrial Development Engineering of Gansu Province, College of Geography and Environmental Science, Northwest Normal University, Lanzhou,Research Center of Wetland Resources Protection and Industrial Development Engineering of Gansu Province, College of Geography and Environmental Science, Northwest Normal University, Lanzhou,Research Center of Wetland Resources Protection and Industrial Development Engineering of Gansu Province, College of Geography and Environmental Science, Northwest Normal University, Lanzhou,Research Center of Wetland Resources Protection and Industrial Development Engineering of Gansu Province, College of Geography and Environmental Science, Northwest Normal University, Lanzhou Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根系形态和生物量分配是决定根系吸收能力发挥的重要特征，其对环境限制因子的响应与适应策略一直是研究的热点。然而，有关土壤盐分对植物根系性状的影响还存在许多不确定性。选择兰州秦王川国家湿地公园芦苇群落为研究对象，垂直于沙河河岸从湿地边缘至湿地中心，依次设置3个不同土壤盐分梯度样地（样地I、样地Ⅱ和样地Ⅲ），采用全根挖掘法和Win-RHIZO根系分析仪相结合的方法，研究了芦苇（Phragmites australis）根冠比、根总长度、比根长、根分叉数、根平均直径等形态参数的变化特征。结果表明：随着样地土壤盐分含量的增加，湿地群落的高度、盖度、密度、地上生物量逐渐下降，芦苇的根冠比、根分叉数呈逐渐减小的趋势，比根长、根总长度呈先下降后上升的趋势，而根平均直径呈相反的变化趋势；研究区土壤含盐量总体以中度盐渍化为主，表层土壤盐分呈现强变异性，随土层深度的增加含盐量呈下降趋势，而变异程度有所差异；芦苇根系性状与土壤含盐量的相关性分析可知，土壤含盐量与根总长度和比根长呈极显著相关关系（P < 0.01），与根冠比、根分叉数呈显著相关（P < 0.05），而与根平均直径相关性不显著。内陆盐沼的芦苇表现出敏感植物的特性，通过根系形态的调整和生物量分配策略的改变来适应盐分强变异的土壤环境，体现了逆境胁迫下湿地植物应对多重环境选择压力的生态适应机制。 Abstract:Root morphology and biomass allocation are important features for determining the capacity of root absorption, and the nature of the responses to environmental constraint factors and adaptation strategies have been a hot research topic. However, numerous uncertainties about the effects of soil salinity on the root traits of plants still exist. This study was performed on Phragmites australis community in Qinwangchuan National Wetland Park of Lanzhou. Three different plots with a soil salinity gradient (plot I, Ⅱ, and Ⅲ) were set up from the edge to the center of wetland, which was perpendicular to the bank of the Sha River. The change characteristics of the morphological parameters such as the ratio of root to shoot, total and specific root lengths, root forks, and the average root diameter of P. australis were studied using the combined method of total root excavation along with the Win-RHIZO root analyzer. The results showed that the height, coverage, density, and above-ground biomass of the wetland community decreased gradually with the increase of soil salinity. In addition, the ratio of root to shoot and root forks of P. australis decreased gradually, and the specific and total root lengths of P. australis first decreased and then they subsequently increased whereas the average root diameter showed an opposite trend. The soil salinity was dominated by moderate salinization, and the surface soil salinity showed strong variability. Specifically, the soil salinity of the plots showed a decreasing trend with increasing soil depth, and the variation degree was different. According to the correlation analysis, there was a significant correlation between the soil salinity, total root length, and specific root length (P < 0.01). Furthermore, the soil salinity was significantly correlated with the root/shoot ratio and root forks (P < 0.05), but not the root mean diameter. The P. australis specimens in the inland salt marshes showed the characteristics of sensitive plants. They adapted to the soil environment that had a strong salt variation by modifying their root morphology and changing the biomass allocation strategy. This phenomenon reflected the ecological adaptation mechanism used by wetland plants to cope with multiple environmental selection pressures under adverse stress conditions. 参考文献 相似文献 引证文献

Multi-Controller Placement Towards SDN Based on Louvain Heuristic Algorithm

The separation of the forwarding and control planes of software-defined networking brings a lot of flexibility to network management. However, with the increase in network capacity, network structure becomes more and more complicated. The controller placement problem in a large-scale network is still a hard nut to crack because of high complexity and difficulty in the tradeoff between performance. In this paper, a novel approach named community detection controller deployment is proposed. With the aid of theory of complex network analysis, the network topology of the controller to be deployed is regarded as a network composed of multiple communities, and then a suitable position is selected in each community to place the controller, which is capable of avoiding the complexity of global deployment. In order to balance the number of switches managed by the controller in each community, the scale constraint factor is introduced into Louvain heuristic algorithm to limit the number of nodes in each community and balance the differences in the number of nodes among different communities. Distinct from the existing clustering-based approaches, this method can independently identify partitions with community attributes according to the network structure without manual intervention. On the other hand, it can adjust the number of nodes within communities on demand to achieve topological equilibrium partition. Experiments are performed on real network topologies, and corresponding results show that the proposed method is more suitable for networks with plenty of nodes and can effectively balance the controllers’ load while keeping latency at a lower level.

Mapping and determining the center of mass of a rotating object using a moving observer

For certain applications, such as on-orbit inspection of orbital debris, defunct satellites, and natural objects, it is necessary to obtain a map of a rotating object from a moving observer, as well to estimate the object’s center of mass. This paper addresses these tasks using an observer that measures its own orientation, angular rate, and acceleration, and is equipped with a dense 3D visual sensor, such as a stereo camera or a light detection and ranging (LiDAR) sensor. The observer’s trajectory is estimated independently of the target object’s rotational motion. Pose-graph mapping is performed using visual odometry to estimate the observer’s trajectory in an arbitrary target-fixed frame. In addition to applying pose constraint factors between successive frames, loop closure is performed between temporally non-adjacent frames. A kinematic constraint on the target-fixed frame, resulting from the rigidity of the target object, is exploited to create a novel rotation kinematic factor. This factor connects a trajectory estimation factor graph with the mapping pose graph, and facilitates estimation of the target’s center of mass. Map creation is performed by transforming detected feature points into the target-fixed frame, centered at the estimated center of mass. Analysis of the algorithm’s computational performance reveals that its computational cost is negligible compared with that of the requisite image processing.

English

Urban and peri-urban agriculture (UPA) have been considered solutions for improving poor living conditions in undeveloped urban and peri-urban areas of developing countries. Therefore, this paper aims to identify the factors affecting UPA decision-making, with special attention to land constraints among poor urban slum dwellers in Bangladesh. A logit regression model was applied using secondary individual household data obtained from the International Food Policy Research Institute (IFPRI), and the predicted probabilities of engaging in UPA for each significant independent variable were estimated. In moderately populated Jessore, households that had more family members without children under five, had some savings, lived in their own house or lived there without paying rent, and had any water logging around the house 1 to 60 days per year were more likely to engage in UPA than other households. On the other hand, in densely populated Tongi, households that lived in their own house or lived there without paying rent, lived there for longer periods, had any water logging around the house less than four months per year, or could rely on neighbors through a difficult period were more likely to engage in UPA than other households. This finding suggests that constraint factors associated with engaging in UPA differ in various urban settings. Therefore, nonprofit/community organizations or local governments are required to plan carefully when promoting UPA, which is one of the coping strategies of poor urban dwellers wishing to enhance their resilience against food insecurity. Key words: Urban and peri-urban agriculture, urban slum, Bangladesh.