基于ICR的履带车辆路径跟踪与转向控制算法研究

针对丘陵山区单边制动农用履带车辆路径跟踪精度低、控制次数多、转向偏差大等问题,本文开展不同负载条件下履带车辆路径跟踪控制研究。首先,对履带车辆的转向运动学进行理论分析,并建立履带车辆运动学模型;其次,根据履带车辆单边制动转向特性,提出一种基于瞬时旋转中心（Instantaneous center of rotation,ICR）的大角度转向控制算法,该算法能够根据规划路径的转向点位置与履带车辆转向瞬心,规划出最优的转向目标点,并控制履带车辆在该转向目标点一次性转向到所需航向,与此同时,完成转向控制器设计;最后,开展履带车辆在3种不同负载条件下的仿真试验与田间试验。仿真结果表明,大角度转向控制算法产生的跟踪路径平均误差面积与平均转向控制次数分别降低68.95%、68.77%;田间试验结果表明,大角度转向控制算法产生的跟踪路径平均横向偏差均值、平均转向控制次数与转向点处平均最小偏差分别减少57.27%、33.93%、62.29%,且路径跟踪效果更优,验证了大角度转向控制算法的有效性。试验结果满足履带车辆路径跟踪的要求,为实现农用履带车辆的路径跟踪提供理论基础与参考。     

Principles and practices of the photo-thermal adaptability improvement in soybean

As a short-day(SD) and thermophilic plant, soybean(Glycine max(L.) Merr.) is sensitive to photo-thermal conditions. This characteristic severely limits the cultivation range of a given soybean cultivar and affects the performances of agronomic traits such as yield, plant architectures, and seed quality. Therefore, understanding the mechanism of photo-thermal sensitivity will provide a theoretical basis for soybean improvement. In this review, we introduce the advances in physiological, genetic, and molecular researches in photoperiodism of soybean, and progress in the improvement of the photo-thermal adaptability. We also summarize the photo-thermal conditions and characteristics of widely-planted soybean cultivars of major production regions in China. Furthermore, we proposed a novel concept of ‘ecotyping' and the strategies for widely-adapted soybean cultivar breeding. This review provides an important guide for improving the adaptability of soybean.     

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Comparative study of milk compositions of cattle,sheep and goats in Nigeria

Variations in the milk composition of Nigerian cattle, sheep and goats (Bunaji, Yankasa and Red Sokoto breeds, respectively), as well as residual phenotypic correlations between the milk constituents, were investigated. Results indicated that sheep and goats differed significantly (P < 0.05) from cattle in all constituents except protein percentage, which averaged 5.43%, 5.43% and 5.49%, respectively. Caprine milk contained the highest percentages of fat (5.80%), total solids (15.37%) and ash (0.77%), and bovine milk contained the least percentages of fat (0.68%) and lactose (1.84%). Overall, the milk compositions of sheep and goats were very similar as they were not statistically different from each other (P > 0.05). Residual phenotypic correlations between the milk constituents revealed highly significant (P < 0.01) and positive relationships between total solids and solids‐not‐fat (0.97 and 0.98 in cattle and sheep, respectively). All other correlations were positive in cattle (ranging from 0.12 to 0.77), except between protein and total solids (?0.44) and protein and solids‐not‐fat (?0.64). Multiple linear regression equations were fitted to predict the percentages of protein and fat. It was demonstrated that the protein percentage could be predicted from total solids and solids‐not‐fat with the highest accuracy of 94%, 86% and 82% in cattle, sheep and goats, respectively. On the other hand, the accuracy of prediction of fat percentage was very low in all the species (R² = 0.01, 0.3 and 0.37 in cattle, sheep and goats, respectively).     

Disease pattern and grade distribution of coast erosion in Liaodong bay

To identify distribution and development of coast erosion in Liaodong bay, erosion situations of typical coastal zone are studied on the basis of field investigation data. The results show that according to erosion landform features, coast erosion in Liaodong bay can be divided into five patterns: washing and abrasion type, wave collapse type, block avalanche type, karst depression type, interface slip type; according to degree of corrosion and siltation, coast erosion in Liaodong bay can be divided into five grades: serious erosion, intensive erosion, erosion, micro-erosion, stability. Sandy coast is eroded mainly in wave collapse type, rocky coast is eroded mainly in block avalanche type and karst depression type, and silty mud coast is eroded mainly in washing and abrasion type. Investigation on disease pattern and grade distribution of coast erosion is helpful to prevention of coastal zone in Liaodong bay.     

The influence of light intensity,temperature and carbon dioxide concentration on anthocyanin content and blueing of ‘Baccara’ roses

The effect of light intensity, temperature and CO₂ concentration on anthocyanin content, blueing of flowers and size of flower buds was examined in ‘Baccara’ roses. Reflectance percentage at 425 nm was found to be an accurate measure of petal blueing. Reflectance was higher as the degree of blueing (determined by subjective estimation) increased and pigmentation decreased. During the first stage of development of the flower branch (elongation stage) temperature and light intensity had no effect on blueing. During Stage 2 of development (main stage of bud development), high temperatures and low light intensities caused blueing, whereas low temperatures during this stage, even at low light intensities, prevented blueing. Blueing was associated with low concentrations of CO₂ (0–100 vpm) as well as darkness. High concentrations of CO₂ (1500–3000 vpm) prevented blueing and increased pigmentation and flower size. The effectiveness of CO₂ in preventing blueing is related to high light intensities.     

Current knowledge on Amaranthus spp.: research avenues for improved nutritional value and yield in leafy amaranths in sub-Saharan Africa

In the past 20 years, very little progress has been achieved in reducing food insecurity, child malnutrition and hunger in Africa. Under-nutrition and micronutrients deficiencies are widespread and affect mainly women and children. To address these problems, increased consumption of African leafy vegetables is promoted as sources of both micronutrients and bio-active compounds. Widely promoted African leafy vegetables include Amaranthus spp., a taxonomic group cultivated worldwide. Species of this genus are used as pseudo-cereals in Europe and America, and are mostly planted as vegetables in Africa. Amaranthus has been rediscovered as a promising food crop mainly due to its resistance to heat, drought, diseases and pests, and the high nutritional value of both seeds and leaves. Leaves are rich in proteins and micronutrients such as iron, calcium, zinc, vitamin C and vitamin A. All parts of the plant are used as medicine to heal many diseases in African communities. This paper focuses on leafy amaranths traditionally utilized on the continent. It briefly reviews the current knowledge on taxonomy, ecology, nutritional and nutraceutical value, production and cultivation systems, reproductive biology, genetic resources and breeding of amaranths. Species of interest include: A. blitum, A. caudatus, A. cruentus, A. dubius, A. hypochondriacus, A. spinosus, A. thunbergii, A. tricolor, and A. viridis. Research and development opportunities on nutritive and nutraceutical properties, production and commercialization, taxonomic evaluation and breeding perspectives were explored.     

Assessing the use of erosion modeling to support payment for environmental services programs

Purpose

Payment for environmental services (PES) has assumed increasing importance in discussions about sustainable development strategies. Many of the PES programs are based on water erosion control and the corresponding environmental and economic benefits generated in the basins where they are implemented. The main objective of this study was to show how erosion susceptibility models can support PES programs.

Materials and methods

The application of the Universal Soil Loss Equation (USLE) in the Sarandi Experimental River Basin (32.7 km²), located in the Federal District, Brazil, was used as a study case. Then a scheme for organizing knowledge about ecosystem services related to erosion control and water resources was performed. Considering the generated scheme, the USLE results, the land use map, and the water use in the region, we evaluated how erosion modeling could support PES programs.

Results and discussion

The results show that a large part of the study basin (90%) presents “low” susceptibility to erosion, which is significant in terms of the use and conservation of ecosystem services, as well as being a limitation regarding the need for the implantation of PES programs for erosion control. Incentives for maintaining the natural vegetation in areas with higher erosion susceptibility have the greatest potential to justify PES programs in the study basin, and the sanitation company is the potential payer for erosion control in the Sarandi River Basin.

Conclusions

The application of the USLE in a spatially distributed form proved to be an important support tool for land management and the implementation of PES policies.