The Impacts and Causes of Land Fragmentation on Farm Productivity: Case Review of East African Countries

This report provides an overall assessment of land fragmentation problems in East Africa. Many parts of East Africa have become highly fragmented, putting development systems and activities in these areas at risk of complete collapse. Land fragmentation occurs when land gets converted for agriculture, industrialization, or urbanization, invaded by non-local plants, or enclosed for individual use and by subdividing farmlands into subsequent smaller units called parcels with varying average farm sizes. Fragmentation results from inappropriate agricultural development processes and ineffective land use planning that fails to recognize how farmland is used, and the importance of its interconnected areas. Insecurity of tenure and resource rights are key factors in making this possible. Land fragmentation is one of the key reasons why the ability of most resources in East Africa becomes scarcer, and those remaining become “privatized” by more powerful community members—keen to maintain their access to them. Such individualistic attitudes are new and disadvantage the poorest even further by affecting the traditional customary safety nets and agricultural outputs. Neither the government nor customary governance systems effectively protect resource access for the poorest. This review summary report identifies the key causes, measures, and implications, government interventions, and the common remedies to land fragmentation problems in the East African Countries of Kenya, Uganda, Rwanda, and Tanzania including neighboring Ethiopia, and the Sudan. The findings indicated from 2005 to 2015, the population kept increasing for all the named countries in East Africa with Rwanda and Uganda having a substantial increase in population density. The study review further explores the trend in the performance of agriculture by average farm sizes within the intervals of five years by highlighting their strong linkages and found that the average farm size has declined drastically, especially for Kenya. This can only mean that small farms kept becoming smaller and smaller and that there were more small-scale farmers. The results further depicted that the major and commonly cultivated food crops among the East African countries include maize, sorghum, rice, cassava, sweet potatoes, bananas, Irish potatoes, beans, peas, etc., with maize yields (Mt/ha) in 2003 for Uganda being the highest (1.79 Mt/ha) and the lowest in Rwanda (0.77 Mt/ha) respectively. Therefore, from the review results, recommendations are being made as to how the negative impacts of land fragmentation on agricultural productivity can be reduced or mitigated. One way is by community sensitization and awareness about the importance of land consolidation and its proposition on farm productivity.

基于Landsat8遥感影像的巢湖及周围地区土地利用变化研究

随着我国经济快速发展,人地矛盾日益突出,巢湖及周围地区作为安徽省中部的重要生态区和重要经济区,土地利用类型的变化影响着该区域的社会、政治、经济和生活。通过地理空间数据云官网获取Landsat8遥感影像数据,运用遥感技术(RS)和地理信息技术(GIS),针对研究区2017年、2019年和2021年三个时期的土地利用变化进行研究,分别从土地利用的变化幅度、土地利用的数量关系、土地利用动态度、土地利用程度分析研究区的土地利用类型的变化过程,分析该变化的驱动因子并提出对策,为今后该地区的经济建设和区域规划提供参考。

Degradation problems of the land/water ecotones in China and their ecological impact to water systems

Degradation of land/water ecotones in China is a serious problem and it is often neglected by people. The types of ecotone degradation are described and analyzed. The degradation of land/water ecotones enhanced the water quality reduction, bank erosion, desasters such as landslide, flood and drought, biodiversity reduction, lost of fertilized lands, decrease of the resource value of water scenic beauty and many others. The paper analyzes how these problems are related with each other.

Land Use Change and Its Impact on Values of Ecosystem Services in the West of Jilin Province

According to interpreting the LANDSAT TM/ETM images of 1986 and 2002, the spatial-temporal characteristics of land use changes were analyzed during 16 years base on GIS. In addition, the change of ecosystem services due to land use change was estimated by the method of vaulting global ecosystem services. The result shows that there were rapid increases in the area of cropland, saline-alkaline land, and dramatic decreases in grassland, water area and wetland between 1986 and 2002. The annual value of the ecosystem services was declined from 767.1 ×10s Yuan/a in 1986 to 624.1 × 10s Yuan/a in 2002, the estimated annual ecosystem service value declined by 18. 6 % （i. e. 1.6% per year） between 1986 and 2002. It indicates that there had been a sever harm to ecosystem functions and services, which results from the deterioration of ecological environment and the adjustment of land use that aim to currently economic benefit.

The Socio-Economic Impact of Land Use and Land Cover Change on the Inhabitants of Mount Bambouto Caldera of the Western Highlands of Cameroon

This work assessed the impact of land use and land cover (LULC) change on the socio-economic conditions of the inhabitants in the Mount Bambouto Caldera from 1980-2016. To achieve this, three time series satellite images;Landsat Thematic Mapper (TM) (1980), Landsat Enhanced Thematic Mapper (ETM) (2001), and Landsat 8 Operational Land Imager (OLI) (2016) scenes were employed to investigate the changes in LULC. The use of satellite images was supplemented with individual interviews, discussions with focus groups and key informants, and direct field observations. Five categories of LULC classes were identified namely: thick woody vegetation (natural forest and oil palms), light vegetation (croplands), savannah (grasslands), buildings (settlements), and bare grounds. The results showed that between 1980 and 2016, croplands, buildings and bare lands increased by 4%, 0.43% and 5.7% respectively while savannah/grassland and natural forest decreased by 4.4% and 5.8% respectively. Household survey revealed soil fertility decline and lack of credit schemes to be major constraints to crop production. Many religious holidays contribute to seasonal food shortages and the community faces a host of socio-economic and institutional challenges. Consequently, majority of house-holds are destitute, live in abject poverty;which is an indication of the need for interventions by government and other development stakeholders to tackle the problems of soil fertility, land use change and food insecurity.

A Study on the Theory and Approach of Environmental Impact Assessment in General Land Use Planning

In this paper,the theory and approach of environmental impact assessment in general land use planning are studied from different aspects.First,starting from the content and concept of general land use planning,the necessity of environmental impact assessment in general land use planning is illustrated.On the basis of its evaluation theories and methodologies,it attempts to establish index system of environmental impact assessment in general land use planning,and point outs that current general land use planning requires public participation.

Land Cover Change and Its Socio-Economic Impact on the Residents of the Mara River, Kenya

Anthropogenic activities are increasingly catalyzing natural climatic factors that drive land cover change at different spatial scales. Available land cover data of the Mara River basin however give a broader picture of the entire basin regardless of the heterogeneity that exists at the sub-catchment level. This study sought to establish sub-catchment specific information on land cover changes through examination of satellite images of four Mara River sub-catchments (Amala, Nyangores, Talek and Sand River) for the period 1987-2017. The relationship between temperature, rainfall and land cover was also computed. In addition, a household survey and focus group discussions were conducted in each sub-catchments to establish the socio-economic impacts of land cover change on the community’s wellbeing. Forest cover was dominant in Amala (39.8%) and Nyangores (43.7%) sub-catchments in 1987 but by 2017 crop lands had surpassed forest cover in the two sub-catchments, accounting for 53.2% and 45.7%, respectively. However, in Talek (52.8%) and Sand River (47.4%) sub-catchments, grassland was the dominant land cover type in 1987 and after the 30 year period, grasslands remained dominant in Sand River, while shrub land became dominant in Talek sub-catchment. A weak positive correlation was observed between rainfall and forest cover, shrub land and cropland, while a negative correlation was observed between rainfall and bare land. Average temperature showed a positive moderate correlation with bare land and built up areas. Analysis of survey data revealed that livestock keeping, temperature increase, type of trees, education level of household head and weak environmental laws were the main drivers of land cover change (P −0.587), beans (r = −0.5459), sorghum (r = −0.351), cow peas (r = −0.544), and pigeon peas (r = −0.337). Focus group discussions participants were supportive of environmental protective measures to reverse negative land cover changes, while planting drought resistant trees, crop diversification and awareness creation among community members were recommended as the most ideal environmental management strategies.

Economic and Land Use Impacts of Improving Water Use Efficiency in Irrigation in South Asia

This paper modifies and uses an advanced computable general equilibrium model coupled with biophysical data on land and water resources by Agro-Ecological Zone (AEZ) at the river basin level to examine the economy-wide consequences of im-provements in water use efficiency (WUE) in irrigation in South Asia. This is the first time the benefits of such improvements have been evaluated in an economy-wide context. It shows that such improvements increase production of food items, enhance food exports, and significantly improve food security in South Asia. Improvement in water use efficiency also leads to lower food prices, provides the opportunity to extend irrigated areas, decreases demand for cropland, and enhances reforestation. Im-provement in water use efficiency in irrigation also generates important net GDP gains across the South Asia region. Investments in improved WUE of up to 40% can be economically justified in Bangladesh, India, and Sri Lanka. However, in Nepal, for an improvement of more than 20% in WUE, the economic gains are smaller than costs from the associated investments. In Pakistan and rest of South Asia, an improvement in WUE of up to 30% appears to be economically profitable.

舰载飞机着舰撞击载荷实测技术研究

针对国内飞机起落架载荷测量中普遍存在的静标动测问题,从理论和机理上分析了静标定的应变法实测动态载荷存在问题的原因。同时,考虑到舰载飞机因定点着舰方式遭受严重的动态载荷,重点研究了舰载飞机着舰撞击载荷的静标动测问题。通过动态落震试验模拟飞机着舰过程,根据测力平台的实测载荷分析,获取了应变法实测载荷精度受动态影响的程度,提出一种改进的惯性修正方法,即:通过落震试验数据辨识质量矩阵,通过辨识的质量矩阵和实测加速度修正应变法的实测载荷。试验结果表明,改进的惯性修正方法进一步提高了垂向载荷的测量精度,显著提高了航向和侧向载荷的实测精度。

严控“溢价率”条件下住宅用地定价影响因素研究

土地市场是全国统一大市场的有机组成部分,地价管理是土地市场建设的核心工作之一。文章从土地的商品属性和特征价格出发,阐述了不完全竞争状态下的地价波动现象,强调了建立要素市场价格异常波动调节机制的必要性。基于评估方法交叉混淆、评估参数偏差不当、权重选取主观随意、土地评估对未来房价走势及库存和销售情况不敏感等问题,分析了土地评估的局限性。结合严控“溢价率”政策对住宅用地定价的更高要求,指出政府在确定土地出让价格时需一并考虑土地出让底价与15%“溢价率”之间的上下限关系。研究认为:确定住宅用地出让价格是一项复杂而庞大的系统工程,并非由单一因素决定,除参考土地评估价格以外,还应重视土地储备成本、土地出让计提、土地隐性成本、出让年度计划、土地使用强度、地价房价关系、房屋去化周期等7种因素对土地出让价格的影响。在此基础上,将土地出让成本的硬性约束作用、土地供应的政策导向作用、房地联动的产业关联作用纳入住宅用地价格形成机制之中。

Using classification assignment rules to assess land-use change impacts on forest biodiversity at local-to-national scales

Background： Ecosystem representation is one key component in assessing the biodiversity impacts of land-use changes that will irrevocably alter natural ecosystems. We show how detailed vegetation plot data can be used to assess the potential impact of inundation by a proposed hydroelectricity dam in the Mokihinui gorge, New Zealand, on representation of natural forests. Specifically we ask： 1） How well are the types of forest represented Locally, regionally, and nationally; and 2） How does the number of distinct communities （i.e. beta diversity） in the target catchment compare with other catchments nationally？ Methods： For local and regional comparisons plant species composition was recorded on 45 objectively located 400 m2 vegetation plots established in each of three gorges, with one being the proposed inundation area of the Mokihinui lower gorge. The fuzzy classification framework of noise clustering was used to assign these plots to a specific alliance and association of a pre-existing national-scale classification. NationaLly, we examined the relationship between the number of alliances and associations in a catchment and either catchment size or the number of plots per catchment by fitting Generalised Additive Models. Results： The four alliances and five associations that were observed in the Mokihinui lower gorge arepresent in the region but limited locally. One association was narrowly distributed nationally, but is the mostfrequent association in the Mokihinui lower gorge; inundation may have consequences of national importance to its long-term persistence. That the Mokihinui lower gorge area had nearly twice as many plots that could not be assigned to pre- existing alliances and associations than either the Mokihinui upper or the Karamea lower gorges and proportionally more than the national dataset emphasises the compositional distinctiveness of this gorge. These outlier plots in the Mokihinui lower gorge may be unsorted assemblages of species or reflect sampling bias or that native- dominated woody riparian vegetation is rare on the landscape. At a national scale, the Mokihinui catchment has a higher diversity of forest alliances and associations （i.e. beta-diversity） than predicted based on catchment size and sampling intensity. Conclusions： Our analytical approach demonstrates one transparent solution to a common conservation planning problem： assessing how well ecosystems that will be destroyed by a proposed land-use change are represented using a multi-scale spatial and compositional framework. We provide a useful tool for assessing potential consequences of land-use change that can help guide decision making.

东北三省耕地利用格局变化对粮食全要素生产率的影响

耕地是粮食生产最基本的要素,当前粮食需求扩大与粮食生产区域性不足矛盾突出,寻求更合理的耕地利用格局来实现粮食全要素生产率的提升具有重要意义。本研究基于土地利用/土地覆被变化(LUCC)遥感监测数据,应用GIS软件提取东北三省2000、2005、2010、2015年耕地利用格局相关数据,同时运用数据包络分析模型估算了2000、2005、2010年和2015年东北三省区域和市域粮食全要素生产率。在耕地利用格局变化分析和粮食全要素生产率测算的基础上,从耕地利用格局变化的角度选取指标构建面板数据模型,定量分析其对粮食全要素生产率的影响。结果表明:东北三省市域粮食全要素生产率4个时期均值分别为0.81、0.78、0.82和0.83,粮食全要素生产率空间分布从最初的相对均匀到局部集聚;耕地转出率和耕地斑块破碎度与粮食全要素生产率呈负相关关系,耕地面积比例、耕地转入率和耕地斑块聚合度与粮食全要素生产率呈正相关关系;东北三省粮食全要素生产率提高主要源于耕地面积增加、林地和未利用地向耕地的转入以及耕地在流域的聚合,粮食全要素生产率的降低主要源于耕地转入减少和建设用地对耕地的嵌入式占用。研究表明,严格规划耕地利用格局、持续开展土地整理、提高耕地聚合度,可在保证耕地有效数量的同时,提高耕地利用格局的集聚性和合理性,促进粮食全要素生产率的提升。

不同缓冲性能乒乓球鞋对人体下肢落地冲击力的影响研究

为分析不同缓冲性能的乒乓球鞋在剧烈运动落地时对人体下肢冲击力的影响,选择20位乒乓球运动员为研究对象,通过比较研究对象在疲劳干预后穿着不同缓冲性能的乒乓球鞋从50cm高处落地时的下肢冲击力、负载率等参数,从生物力学视角下对穿着乒乓球鞋从高处落地时人体下肢的冲击力影响进行分析。结果表明:良好的缓冲能够明显增强人体髋关节、膝关节或是踝关节落地角度变化量,显著增强人体下肢稳定性,但不能显著影响人体落地时踝关节处神经-肌肉的控制情况。

海浪情形下舱囊组合体着水冲击特性研究

为了研究舱囊组合体在海浪情形下的着水冲击特性,文章基于某型返回舱和气囊的组合模型,利用LS-DYNA软件中的流固耦合算法、气囊仿真算法以及造波算法建立返回舱-气囊-波浪-空气的多介质耦合模型,模拟海浪情形下舱囊组合体的着水过程,并讨论不同入水角度和不同入水位置对返回舱过载、气囊内压以及气囊受力的影响。经分析可知,舱囊组合体入水角度越大,过载越小,随着入水角度的增大,气囊的内压峰值呈减小趋势。此外,舱囊组合体在海浪波峰处着水的过载明显小于在波谷处着水的过载,气囊系统的受力分布表现出明显差异。研究结果可为海上回收系统的设计和入水冲击试验提供技术参考。

国外新一代飞船回收着陆系统设计综述

为开展大规模的商业航天活动并瞄准未来载人深空探测任务,美国加紧研制了以洛克希德·马丁公司的猎户座飞船、波音公司的星际航线飞船和星际探索公司的载人龙飞船为代表的新一代载人飞船,该类飞船均采用由多个降落伞组成的群伞系统进行着陆前减速、配置着陆缓冲气囊或倾斜飞船返回舱姿态实现低冲击着陆和无损回收,以达到飞船返回舱可重复使用并提升航天员着陆舒适度的目的。从工程应用角度出发,调研了国外新一代飞船回收着陆功能的方案设计、技术指标体系、产品参数和技术验证情况,从系统层面对其设计思想进行归纳总结,梳理出国外新一代载人飞船回收着陆功能的研制进展及发展趋势,以期为中国开展相关研制工作提供参考。

Hierarchical Voronoi Structure Inspired by Cat Paw Pads Substantially Enhances Landing Impact Energy Dissipation

When a human lands from a high drop,there is a high risk of serious injury to the lower limbs.On the other hand,cats can withstand jumps and falls from heights without being fatally wounded,largely due to their impact-resistant paw pads.The aim of the present study was to investigate the biomechanism of impact resistance in cat paw pads,propose an optimal hierarchical Voronoi structure inspired by the paw pads,and apply the structure to bionic cushioning shoes to reduce the impact force of landing for humans.The microstructure of cat paw pads was observed via tissue section staining,and a simulation model was reconstructed based on CT to verify and optimize the structural cushioning capacity.The distribution pattern,wall thickness of compartments,thickness ratio of epidermis and dermis,and number of compartments in the model were changed and simulated to achieve an optimal composed structure.A bionic sole was 3D-printed,and its performance was evaluated via compression test and a jumping-landing experiment.The results show that cat paw pads are a spherical cap structure,divided from the outside to the inside into the epidermis,dermis,and compartments,each with different cushioning capacities.A finite element simulation of different cushioning structures was conducted in a cylinder with a diameter of 20 mm and a height of 10 mm,featuring a three-layer structure.The optimal configuration of the three layers should have a uniform distribution with 0.3–0.5 mm wall thickness,a 1:1–2 thickness ratio of epidermis and dermis,and 100–150 compartments.A bionic sole with an optimized structure can reduce the peak impact force and delay the peak arrival time.Its energy absorption rate is about 4 times that of standard sole.When jumping 80,100,and 120 cm,the normalized ground reaction force is also reduced by 8.7%,12.6%and 15.1%compared with standard shoes.This study provides theoretical and technical support for effective protection against human lower limb landing injuries.

航空轮胎着陆冲击动力学仿真与安全分析

本文针对飞机着陆冲击动力学建立了飞机单轮主起落架有限元模型,并进行着陆冲击动力学仿真和安全分析。首先,通过对机身、起落架、轮胎和道面结构的简化构建了飞机单轮主起落架三维模型,并利用Hypermesh完成模型的网格划分。其次,采用Ogden模型描述轮胎橡胶的应力-应变关系,建立了轮胎有限元模型,验证了轮胎变形的仿真结果与经验公式计算结果基本一致。最后,采用隐式动力学算法研究了不同着陆速度下轮胎的承受载荷和变形情况,并结合适航标准对轮胎着陆冲击的安全性进行分析,得到了飞机着陆速度的安全阈值,为航空轮胎着陆安全性评估提供了新的研究方法。

发射装置减振参数优化设计

为提升发射装置着陆的抗冲击性,本研究建立动力学模型,利用有限元仿真相同冲击荷载的弹体动态响应,以验算动力学模型的准确性。并采用粒子群优化算法对发射装置的减振系统进行参数优化,选取结构刚度与阻尼作为优化变量,以最小化弹体的动态响应峰值为目标。优化结果表明,适当调整刚度与阻尼能显著减少冲击过载和振动幅度,有效优化弹体在冲击荷载作用下的动态响应。这一研究可为发射装置的设计及其减振系统的优化提供科学依据和方向。

新基建对工业用地绿色利用效率的影响研究

新基建不仅对城市工业用地建设管理提供了新途径,而且对城市集约化绿色化发展也具有重要意义。文章采用2011—2020年我国30个省份的面板数据,运用双向固定效应模型,检验新基建水平对工业用地绿色利用效率的赋能效果及其异质性。实证检验结果表明:新基建并没有提升工业用地绿色利用效率水平,样本期间研究发现新基建的三大内涵(“信息基建”“融合基建”“创新基建”)中“信息基建”和“创新基建”显著促进工业用地绿色利用效率的提升,而“融合基建”对其存在显著负向影响。在地区异质性上,新基建对东北地区有正相关关系,对东、中部地区呈现负相关关系,但回归系数并不显著,而对西部地区存在显著负向作用。

篮球鞋结构对人体生物力学的影响研究综述

篮球运动中频繁的跑步、急停、起跳等动作给下肢各关节带来的冲击是不可避免的,且落地阶段下肢关节的生物力学指标与肌肉活动等均会有一定程度的改变,很容易发生运动损伤。篮球鞋作为篮球运动必不可少的运动装备,对促进运动员技能发挥、降低运动损伤风险有着重要作用。对此,本文简述了篮球鞋结构及其对人体生物力学影响的研究现状,从篮球鞋鞋底硬度、鞋帮高度方面探讨了篮球鞋结构对人体生物力学与冲击力的具体影响。结果显示落地动作下人体所承受的巨大冲击力是导致运动损伤的主要原因,为此分析了穿着篮球鞋不同落地动作下人体生物力学特征。