基于离散元法的履带式电动割草机性能的仿真

针对果园割草机工作时漏割率高、燃油污染大的问题,设计了一种适用于丘陵山地的履带式电动割草机。利用SOLIDWORKS、EDEM软件完成整机模型和杂草模型的构建,并通过单因素仿真试验研究了不同割刀类型下的割刀转速、割刀高度对漏割率的影响,结果表明漏割率随着割刀转速增加和割刀高度的减小而降低,在割刀转速500 r/min、割刀高度75 mm条件下不同割刀割草情况的对比后得出,一字割刀受力最小。在此基础上,进行三因素三水平的正交仿真设计,构建二阶多项式响应面模型,对割刀类型、割刀转速和割刀高度的交互作用进行显著性分析,确定最优参数组合为一字割刀,转速为1017.439 r/min,割刀高度为90.919 mm,根据优化参数进行仿真实验,得出漏割率的值为4.479,满足漏割率≤5%的要求,研究可为履带式电动割草机的结构设计及工作参数优化提供参考。

覆膜烟地杂草发生规律及防除

烟地覆膜栽培,虽能保温增温,促进烟叶早熟高产,但烟地杂草在透明地膜覆盖下易疯长,与烟苗争肥、争水、争光.疯长杂草甚至顶破地膜,严重影响盖膜效果.本研究的目的是探索既能保湿增温又能防除杂草的烟地覆膜技术,并根据杂草发生特点及覆膜技术选择除草剂适时施用,以作为烤烟高产栽培综合技术的内容实施,促进烤烟生产的发展.

中草药治疗小儿胃结石32例

1986年8月～2000年8月,我们采用中草药治疗小儿胃结石32例,取得满意效果,现报告如下.

Effect of Different Flue-curing Techniques on the Taste and Aroma Substances of Tobacco Leaves

[Objective]This study aimed to optimize the conditions for curing tobacco leaf, so as to improve its flavor and quality. [Method] Leaves of Yuanyan 87 were col ected and cured by three different techniques （moderate-intensity conditions throughout the curing course; high-intensity conditions at leaf yel owing and wilting stages, moderate-intensity conditions at leaf drying and vein drying stages; high-in-tensity conditions throughout the curing course）, and then the contents of 48 aroma substances and taste indices of the finished tobacco leaves were measured. [Result] The contents of 28 aroma substances in the tobacco leaves cured under high-inten-sity conditions throughout the course were higher and the taste indices of these to-bacco leaves were better, compared with those flue-cured by the other two tech-niques. The contents of the other 20 aroma substances were not significantly af-fected by the curing techniques. The second best technique was high-intensity con-ditions at leaf yel owing and wilting stages and moderate-intensity conditions at leaf drying and vein drying stages. Curing tobacco leaves at moderate-intensity condi-tions throughout the course was the worst one. [Conclusion] Compared with the oth-er two methods, the contents of aroma substances and taste indices of the tobacco leaves cured under high-intensive conditions throughout the course were the best.

The Nucleosides Contents and Their Variation in Natural Cordyceps sinensis and Cultured Cordyceps Mycelia

Aim: To compare the contents of nucleosides from natural Cordyceps sinensis and cultured Cordyceps mycelia, and to study the effect of humidity and heat on the content of nucleosides. Methods: The contents of nucleosides were determined by using high performance capillary electrophoresis (HPCE). Beckman P/ACE System 5010 apparatus equipped with a UV detector and a Beckman untreated fused-silica capillary (57 cm 75 mm, 50 cm effective length) was used. Before sample injection, the capillary was rinsed with 1 molL-1 sodium hydroxide solution and running buffer for 5 min, respectively. A voltage of 20 kV was applied for the separation. Pressure injection was 586 kPa for 6 seconds, and the wavelength of detector was 254 nm. The running time was 20 min at 20 oC. The effect of humidity and heat on the contents of nucleosides from natural Cordyceps sinensis and cultured Cordyceps mycelia was observed for 1, 3, 5 and 10 days at temperature 40 oC, and relative humidity 75%. Results: The content of nucleosides from natural Cordyceps sinensis was higher than that from cultured Cordyceps mycelia. But the contents of nucleosides from freshly collected natural Cordyceps sinensis were very low, even below the limit of quantitation. The contents of nucleosides from natural Cordyceps sinensis were significantly increased by humidity and heat, but this phenomenon was not observed in cultured Cordyceps mycelia. Conclusion: There are differences between the nucleosides from natural Cordyceps sinensis and cultured Cordyceps mycelia. The nucleosides in natural Cordyceps sinensis may be derived from the degradation of nucleic acids. This implies that adenosine being used for the quality control of natural Cordyceps sinensis may have to be reconsidered.

Development of Artificial Diet for Erigonidium graminicolum(sundevall)

[Objective] This study was to find out the artificial diet formula for Erigoni- dium graminicolum （Sundevall） to realize its indoor artificial breeding. [Method] Using orthogonal decomposition method, the diet most suitable for the normal and quick growth of Erigonidium graminicolum （sundevall）, was developed by adding different species and different proportions of fresh insects to the artificial diet based on the formula of total nutrient solution proposed by Zhao Jing-zhao. [Result] The most suit- able formula for the development and growth of Erigonidium graminicolum （Sundevall） is 10 ml of egg white, 2 g of honey, 2 g of sucrose, 10 ml of water, 5 g of Ci- cadella viridis, moderate amount of cornmeal, compound vitamin B1 and vitamin C1. [Conclusion] The development of new type artificial diet can provide timely and nec- essary material premise for its large-scale indoor propagation.

Study on the Degradation Trend of Ryegrass-White Clover Artificial Grassland

[Objective] The study aimed to explore the degradation law and trend of artificial grassland. [Method] Taking the ryegrass （Lolium perenne） - white clover （ Trifolium repens） artificial grassland in Maiping Township, Guizhou Province as the research object, the grassland vegetation of 40 quadrate from different areas （area around the sheep shed, hilltop, hillside, flatland at the foot of the hill） were analyzed by comparing the dominance and richness index. [ Result] Degradation of different degrees appeared in various areas of this artificial grassland. To be specific, the degradation of grassland around the sheep shed was not serious for less consumption by the sheep; however, the areas on the hilltop and hillside degenerated to the grassland types of dallis grass （ Paspalum dilatatum Poir. ） -Indian lovegrass （ Eragrostis pilosa） and dallis grass - cogongrass [ Imperata cylindrica （ Linn. ） Beauv. ], respectively, and the area at the foot of the hill degenerated to the grassland type dominated by garland chrysanthetnum （ Chrysanthemum coronarium L. ） and knotgrass （ Paspalum distichum L. ）. [ Conclusion ] This study provided a basis for grassland improvement as well as the efficient and sustainable utilization of grazing-type artificial grassland in South China.

Soil CH_4 fluxes response to understory removal and N-fixing species addition in four forest plantations in Southern China

CH4 is one of the most important greenhouse gases, and mainly comes from soils in forest ecosystems. The objective of this study was to determine the effects of forest management practices such as understory removal and N-fixing species （Cassia alata） addition, on soil CH4 fluxes in four forest plantations in southern China. Fluxes of CH4 were measured in Eucalyptus urophylla plantation （B1）, Acacia crassi-carpa plantation （B2）, 10-native-species-mixed plantation （B3）, and 30-native-species-mixed plantation （B4） stands using the static chamber method in Southern China. Four forest management treatments, includ-ing （1） understory removal and replacement with C. alata （UR＋CA）; （2） understory removal only （UR）; （3） C. alata addition only （CA）; and （4） control without any disturbances （CK）, were applied in the four forest plantations. The results showed that plantation types had a significant effect on soil CH4 fluxes. B1 and B2 tended to be CH4 consumers, while B3 and B4 inclined to be CH4 producers. UR decreased CH4 fluxes by providing a more optimal soil temperature and moisture regime for mi-croorganism community and increasing substrate mineralization. How-ever, CA enhanced CH4 fluxes in B1 and B2 for N-fixing function of C. alata while lowered CH4 fluxes in B3 and B4. Soil CH4 flux rate was significantly related to soil temperature and moisture conditions in the top 10-cm soil layer. Furthermore, the quality of substrates, such as Soil Organic Carbon （SOC） and mineral N might also be important driving factors for CH4 fluxes. This study improved our understanding on CH4 fluxes in plantations under different management practices such as UR and CA.

Analysis of Characteristics of Grazed Artificial Pastures in the South of Guizhou

＂Ryegrass, orchard grass, Festuca arundinacea and Trifolium repens＂ were researched in Dushan County, Guizhou Province, in order explore grass characteristics by different grazing methods in seasons. The results show that grass community height in different groups was of little differences（P0.05）; the group of moderate grazing in spring, summer and autumn dominated in grass cover; grass density showed insignificant variations among different treatment groups（P0.05） and in the groups of heavy grazing in spring and autumn and moderate grazing in summer and of moderate grazing in spring, summer and autumn, grass community density was higher compared with the other groups（P0.05）; as for above-ground biomass, the group of moderate grazing in spring and autumn and heavy grazing in summer and of moderate grazing in spring, summer and autumn dominated.

Research on the Soil Carbon Storage of Alpine Grassland under Different Land Uses in Qinghai-Tibet Plateau

In this article, we mainly analysis the soil carbon storage of the alpine grassland under different land uses in Qinghai-Tibet Plateau. The samples of this investigation include six experimental fields which are fenced mowing grassland, artificial grassland, winter and spring grazing meadowland, summer and autumn mild grazing land, summer and autumn moderate grazing pasture and summer and autumn severe grazing land and seven soil layers included 0 cm-5 cm, 5 cm-10 cm, 10 cm-20 cm, 20 cm-30 cm, 30 cm-50 cm, 50 cm-70 cm and 70 cm-100 cm. The results show that the soil carbon storage in different soil layers will gradually reduce and the difference was remarkable （P 〈 0.05）. What is more, the soil carbon storage of alpine grassland under different land uses has following sequence： winter and spring grazing grassland 〉 summer and autumn mild grazing land 〉 artificial grassland 〉 summer and autumn moderate grazing meadowland 〉 summer and autumn severe grazing pasture 〉 fenced mowing meadow, and the significant difference between them is remarkable （P 〈 0.05）.

Investigation on influencing factors of 5-HMF content in Schisandra

In order to investigate the influencing factors of 5-hydroxymethyl-2-furaldehyde （5-HMF） content in Schisandra, confirm the theory of 5-HMF deriving mainly from Schisandra processing course, and give some suggestions about the Schisandra processing method, the 5-HMF contents in decoctions of Schisandra under different heating temperature, decocting time, soaking time, processing methods and treatment with different solvents before decocting the Schisandra were measured by RP-HPLC method. The results showed that there is great difference of 5-HMF level in decoctions from differently processed Schisandra and unprocessed Schisandra; decocting time of 60 rain has some effects on 5-HMF level in decoctions and there is certain quantity 5-HMF in processed Schisandra itself and very little 5-HMF in unprocessed Schisandra. Heating time, heating temperature and treating solvents all have effect on 5-HMF level in decoction of Schisandra. 5-HMF in Schisandra was mainly from processing course. Both long heating time and high heating temperature can increase 5-HMF level in Schisandra. The production of 5-HMF in Schisandra may have some relationships with some polar components, which can dissolve in water, ethanol and acetone, especially in ethanol. To control processing temperature, processing time and treatment with some solvent is very important for controlling 5-HMF level in Schisandra.

Response of Artificial Grassland Carbon Stock to Management in Mountain Region of Southern Ningxia, China

Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L. （alfalfa） grassland biomass carbon and soil organic carbon density （SOCD） in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period （viz. 0-10 year）. Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0-10 year. During 0-30 year, the SOCD from 0-100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for l0 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.

Effect of turf on the cutting movement of female football players

Purpose： The globalisation of artificial turf and the increase in player participation has driven the need to examine injury risk in the sport of football. The purpose of this study was to investigate the surface--player interaction in female football players between natural and artificial turf. Methods： Eight university level female football players performed an unanticipated cutting manoeuvre at an angle of 30° and 60°, on a regulation natural grass pitch （NT） and a 3G artificial turf pitch （AT）. An automated active maker system （CodaSport CXS System, 200 Hz） quantified 3D joint angles at the ankle and knee during the early deceleration phase of the cutting, defined from foot strike to weight acceptance at 20% of the stance phase. Differences were statistically examined using a two-way （cutting angle, surface） ANOVA, with an α level of p 〈 0.05 and Cohen＇s d effect size reported. Results： A trend was observed on the AT, with a reduction in knee valgus and internal rotation, suggesting a reduced risk of knee injury. This findings highlight that AT is no worse than NT and may have the potential to reduce the risk of knee injury. The ankle joint during foot strike showed large effects for an increase dorsiflexion and inversion on AT. A large effect for an increase during weight acceptance was observed for ankle inversion and external rotation on AT. Conclusion： These findings provide some support for the use of AT in female football, with no evidence to suggests that there is an increased risk of injury when performing on an artificial turf. The ankle response was less clear and further research is warranted. This initial study provides a platform for more detailed analysis, and highlights the importance of exploring the biomechanical changes in performance and injury risk with the introduction of AT.

The Bifurcation Behavior of CO Coupling Reactor

The bifurcation behavior of the CO coupling reactor was examined based on the one-dimensional pseudo homogeneous axial dispersion dynamic model. The method of finite difference was used for solving the boundary value problem; the continuation technique and the direct method were applied to determine the bifurcation diagram. The effects of dimensionless adiabatic temperature rise, Damkohler number, activation energy, heat transfer coefficient and feed ratio on the bifurcation behavior were investigated. It was shown that there existed static bifurcation and the oscillations did not occur in the reactor. The result also revealed that the reactor exhibited at most 1-3-1 multiplicity patterns within the range of practical possible parameters and the measures, such as weakening the axial dispersion of reactor, enhancing heat transfer, decreasing the concentration of ethyl nitrite, were efficient for avoiding the possible risk of multiple steady states.

Soil Carbon Stock and Flux in Plantation Forest and Grassland Ecosystems in Loess Plateau, China

Carbon sequestration occurs when cultivated soils are re-vegetated. In the hilly area of the Loess Plateau, China, black locust （Robinia pseudoacacia） plantation forest and grassland were the two main vegetation types used to mitigate soil and water loss after cultivation abandonment. The purpose of this study was to compare the soil carbon stock and flux of these two types of vegetation which restored for 25 years. The experiment was conducted in Yangjuangou catchment in Yah＇an City, Shaanxi Province, China. Two adjacent slopes were chosen for this study. Six sample sites were spaced every 35-45 m from summit to toe slope along the hill slope, and each sample site contained three sampling plots. Soil organic carbon and related physicochemical properties in the surface soil layer （0-10 cm and 10-20 cm） were measured based on soil sampling and laboratory analysis, and the soil carbon dioxide （CO2） emissions and environmental factors were measured in the same sample sites simultaneously. Results indicated that in general, a higher soil carbon stock was found in the black locust plantation forest than that in grassland throughout the hill slope. Meanwhile, significant differences in the soil carbon stock were observed between these two vegetation types in the upper slope at soil depth 0-10 cm and lower slope at soil depth 10-20 cm. The average daily values of the soil CO2 emissions were 1.27 μmol/（m2·s） and 1.39 μmol/（m2·s） for forest and grassland, respectively. The soil carbon flux in forest covered areas was higher in spring and less variation was detected between different seasons, while the highest carbon flux was found in grassland in summer, which was about three times higher than that in autumn and spring. From the carbon sequestration point of view, black locust plantation forest on hill slopes might be better than grassland because of a higher soil carbon stock and lower carbon flux.

Interrelation between Seasonal Grazing Behavior of Guizhou Black Goat and Grassland Productivity

In order to discover the relationship of the Guizhou black goat seasona grazing behavior traits and grassland productivity, the varieties of grazing behavior of Guizhou black goat and its relationship with the grassland productivity under different grazing intensity in all seasons on Guizhou karst artificial grassland were studied. Obvious differences for goat grazing behavior were found under differen grazing intensity in either the same season or different seasons. The grazing behav ior in the same season showed that it could significantly reduce the mouth eating grass within 5 minutes, each step number, feeding speed, each food intake, daily feed intake（P0.05） under high grazing intensity. In different seasons, it could in crease the feeding time within 5 min, marching step, standing time and intake（P0.05） in the spring; while in the summer, it could improve intake mouth number each mouth eating grass number and feeding rate（P0.05）. It had no obvious dif ference in ruminant behavior parameters in the same season under different grazing intensity, but in different seasons, it can obviously increase ruminant within 5 minutes, number of ruminant feed group（P0.05） in the spring, and it can obviously in crease the time and number of each food group chew（P0.05） in the summer. The correlation analysis of main goat grazing behavior parameter showed that it had good correlation among other parameters except within 5 min walk time, each feed intake and daily feed intake（P0.05）.The relationship between goat grazing behavio parameters and grassland productivity showed that, the foraging time and standing time within 5 min were lower in the medium level of grassland productivity, while number of food intake, every step to eat grass and daily feed intake were higher with increasing grassland productivity, goats feeding speed was reduced, but each intake was increased.

Exploration of tortoise shell structure mechanical characteristics

As one of the oldest creatures on the earth, the tortoises have formed a nearly perfect shell structure after millions of years of evolution In this paper, Chinese tortoise shell is studied. Firstly, the scanning model of the tortoise shell is established by means of computer tomography （CT） scanning technology and MIMICS software. Secondly, the solid model of three-dimensional structure of the tortoise shell is constructed by using geomagic studio reverse engineering software. Afterwards, the compression numerical simulation of the tortoise shell structure under low strain rate is conducted with the help of finite element software LS-DYNA. Finally, load-bearing characteristics of the tortoise shell structure and dome-shaped structure are compared and analyzed. The results show that compared withthe dome-shaped structure with the same volume, tortoise shell structure has a higher structural rigidity and can withstand higher pressure. Therefore, tortoise shell structure provide some reference to the design of armored vehicles, sheltersand other types of thin shell structures.

Separation and Purification of Tobacco Peroxidase I from Nicotiana Tobaccum

A new isoenzyme of tobacco peroxidase(TOP) I was purified from tobacco (K326) by using acetone powder, ammonium sulfate precipitation and column chromatography on DEAE-52 cellulose, Sephadex G-75 and DEAE-Sephadex A-50. It is an iron-protein containing haemachrome, whose molecular weight is 21888.5 and the isoelectric point is 3.5. The optimum pH value and temperature of this enzyme is 6.0 and 45℃respectively. The enzyme is stable in the pH range from 3.0 to 10.0 and has a favorable thermostability.

Interactions Ticks, Hosts and Pastures： Case of the Girolando Dairy Cattle and the Artificial Pastures of Panicum maximum and Panicurn maximum var. C1

On the Kpinnou ranch in Benin, it was observed that the Girolando dairy cattle which graze Panieum maximum var. CI are more susceptible to infestation of ticks. The purpose of this study was to highlight the interactions between ticks and their bovine hosts and two types of artificial grazing pastures. Nineteen young Girolando dairy cattle were used during the big rainy season （March-June） 2009. All present ticks on the animals have been counted according to the body region. The bovine have been divided into two relatively homogeneous groups often and nine animals. The group I of 10 animals had been grazed on Panicum maximum whereas the group 2 of 9 animals had been grazed on Panicum maximum var. C 1. During the two months of grazing, a weekly monitoring of the evolution of the load in ticks has been achieved. Four genera of ticks were identified on the bovine Girolandos （Amblyomma, Hyalomma, Rhipicephalus and Boophilus）. The Boophilus genus is the most abundant （P 〈 0.05）. The animals having grazed Panicum maximum var. C I are more infested than those that have been grazed Panicum maximum. A variation of the rate of infestation of the animals has been observed in relation to the different body areas. The colour of the coat also has an effect on the load in tick of the bovine. The bovine of dark coat are in general more infested （P 〈 0.05） than those of clear colour.

Process Optimization of Vacuum Fried Rice-Straw Mushroom （Volvariella Volvacea） Stem Chip Making

The study was aimed to obtain the optimum conditions for vacuum frying and predicting the moisture lost during rice straw mushrooms stem chip production. The raw materials were obtained from the local farmer around the campus. A completely randomized factorial experimental design and Duncan＇s multiple range tests were used to achieve the objectives. Three temperatures, i.e. 80, 90 and 100 ℃ and five frying time, i.e. 3, 6, 9, and 15 minutes with a 2 mm slice thickness were studied to determine the optimum condition and predict the moisture decrease. Results showed that the vacuum frying time in general affects the chips color and oil uptake significantly （p 〈 0.01） and correlated with the moisture decrease. The chips moisture content decline significantly after vacuum frying at 90 ℃ and 100 ℃ for 3 minutes. While for the 80 ℃ vacuum frying, the significant decrease of moisture occurred due to the increase of vacuum frying time from 3 to 6 minutes （p 〈 0.01）. The optimum conditions for a 2 mm slice thickness chips making are vacuum frying at 100 ℃ for 3 minutes. The chips moisture lost followed generally a two-stage of falling rate pattern during vacuum frying, and each could be well predicted by an exponential equation （R2 = 0.99）.