Abstract:178 recombinant inbred lines (F12) of crossing rice varieties Gang 46B with A232 were used to investigate the length,width and aspect ratio of flag leaves in Lingshui,Hainan province and Wuhan,Hubei Province. 14 QTLs in total including 5 flag leaf width QTLs,6 flag leaf length QTLs,and 3 flag leaf lengthto width ratio QTLs were detected,which were distributed on rice chromosomes 1,2,4,6,7,10 and 12. LOD values were ranged from 2.52 to 5.62. The contribution rate of a single QTL to phenotypic variation varied from 5.56% to 21.27%.

Abstract:The pot experiment was used to study the effects of salt stress on growth of Oceanrice 86 and absorption,transportation and distribution of mineral elements using Huanghuazhan as control. The results showed that salt stress inhibited the dry matter accumulation of rice plants. The salt tolerance threshold of Oceanrice 86 and Huanghuazhan was 8.72 g/kg and 6.35 g/kg,repectively. Compared with Huanghuazhan,salt tolerance of Oceanrice 86 was stronger. Under salt stress,Oceanrice 86 selectively absorbed Na + through the root system and regulated the distribution of Na+ at the organ level. Its leaf sheath accumulated more Na +,reducing the toxicity of Na+ to the leaves. The content of K + in Huanghuazhan leaves did not change significantly from that of the control,but the K + content in the leaf sheath and root system was 4.64 g/kg in the soil. The K+ content was greatly reduced by 53.8% and 70.0%,respectively. The K+ content in various organs of Oceanrice 86 gradually decreased with the increase of the degree of salt stress,and the decrease of K+ content in leaves was relatively low. The content of Ca2+ and Mg2+ in the leaf sheath of Huanghuazhan decreased significantly with the increase of saltstress,while Oceanrice 86 had no significant changes. Compared with Huanghuazhan,Oceanrice 86 had a strong ability to inhibit Na + and promote the upward transport of Ca2 + and Mg2 +.

Abstract:A surfaceenhanced Raman spectroscopy (SERS) technique based on functionalized Au@Ag nanorods (Au@Ag NRs) was established to quantitatively detect Hg2+ in aqueous solutions.In the presence of Hg2+,its coordination with 2,5 dimercapto 1,3,4-thiadiazole (DMCT) on the surface of Au@AgNRs caused the aggregation of SERS detection probes,resulting in a “hot spot” effect,leading to the SERS signal of DMCT increased at 1 360 cm-1.The increased SERS signal showed a good linear relationship with Hg2+ in the concentration range from 0.1 to 10 μg/L :Y=195.49384X+1676.23663(R2=0.991).The detection limit was as low as 17 ng/L,much lower than that of the Hg2+ content(1 μg/L) in drinking water specified by World Health Organization(WHO).The results of spiked recovery test carried out in the actual water sample showed that the spiked recoveries of Hg2+ were from 100.1% to 106.5%,and the relative standard deviations were from 1.23% to 7.99%.The Hg2+ sensing detection technique with accuracy,rapidity and high sensitivity based on SERS has an effective application for quantitatively detecting Hg2+ in real water.

Abstract:“Hot Green No. 2” pakchoi was pot-planted with five treatments including 0% C,1% C,2% C,4% C and normal application of potassium fertilizer to investigate the effects of biochar application on potassium content of different forms in red soil and the growth of pakchoi. Results showed that the effects of biochar on content of water-soluble potassium,exchangeable potassium and non-exchangeable potassium in red soil were increased by 12.6%-51.8%,13.3%-43.5% and 10.3%-26.1%,respectively,compared to the control. The effect of biochar on improving different forms of potassium between 4% C and normal potassium was the most similar. Biochar application increased soil pH value significantly by 0.06-0.25 units,as available phosphorus,available potassium and organic carbon in soil. Also the cation exchange capacity,exchangeable calcium and magnesium content increased significantly,while the exchangeable aluminum content decreased significantly with a decrease of 87%-98%. Biochar application could improve pakchoi growth performance as increasing the biomass,leaf number,plant height and fresh weight of pakchoi.

Abstract:This study investigated symbiotic function of purple acid phosphatase gene MtPAP3 in Medicago truncatula with MtPAP3Pro∶∶GUS histochemical location,over-expression and CRISPR/Cas9 gene knock-out. The results showed that MtPAP3 was mainly located in vascular bundle of roots and nodules,and meristem and infection zone of nodules. The transcription levels of MtPAP3 were enhanced in roots and nodules under Pi deficiency conditions. The numbers and nitrogenase activity of nodules were increased in transgenic overexpression plants. The knock-out of MtPAP3 significantly inhibited the development and nitrogenase activity of nodules. It is indicated that MtPAP3 involves in phosphorus metabolism and symbiotic nitrogen fixation in nodules under low phosphorus stress.

Abstract:Two phosphate solubilizing bacterial strains,PSB-1 and HZP1,were isolated form soybean nodules and rhizosphere soil. The ability of these two strains to produce IAA (indole-3-acetic acid IAA) and the ability to dissolve inorganic phosphorus were measured by Salkowski colorimetry and molybdenum antimony-phosphonium colorimetry. Soybean and Astragalus sinensis were co-inoculated. Results showed that both two phosphate solubilizing strain produced IAA. The legume growth-promoting effects of the phosphate solubilizing strains and rhizobium inoculum were investigated in unsterilized soil and soybean planting field. Inoculation with HZP1 or PSB-1 promoted the growth of Astragalus sinensis and soybean. Co-inoculation of phosphorus-solubilizing strains with rhizobium further increased the shoot biomass,fresh weight of nodules and the number of nodules of soybean and Astragalus sinensis. The results of field tests showed that inoculation with rhizobium or phosphate dissolving agents alone had a certain effect of increasing yield but double inoculation with rhizobium and phosphate dissolving bacteria did not increase the yield significantly.

Abstract:The dynamic changes of plant community structures at different restoration stages in the aerial-seeding region in Otindag Sandy Land were studied,aiming to understand the restoration characteristics and change rules of vegetation restoration. From 2013 to 2017,vegetation survey tests were conducted in 11 aerial seeding areas in the Otindag Sandy Land. Correspondence analysis,correlation analysis,and Mann-Kendall trend analysis were used to analyze stages of vegetation restoration in the aerial seeding area and to discuss the status and role of each functional plant in the community based on a functional perspective. The results showed that it was divided into three recovery stages across 19 years. Moreover,after aerial seeding,the degree of dependence among the following seven functional plants of rubs/subshrubs,perennial weeds,annual/biennial weeds，perennial leguminous forage,perennial gramineous forage and annual/biennial gramineous forage,was decreased gradually.Community stability was increased by the number of recovery years. Dominant function type of vegetation restoration was not consistent in different restoration stages,resulting in timing management could be employed at different stages. Consequently,the succession stage and overall development trend of plant community are more conducive to the recovery and reconstruction of the vegetations in degraded sandy land.

Abstract:Based on the tourist statistics data of the Taizishan Forest Park,the paper used the composition method of ecological footprint to calculate the tourism ecological footprint,tourism ecological carrying capacity and tourism sustainable development of the forest park. The results show that: the total tourist ecological footprint of the Taizishan National Forest Park in 2018 was 1 013.36 hm2,the total tourism ecological carrying capacity was 10 738.99 hm2,the total tourism ecological surplus was 9 725.63 hm2,the degree of tourism sustainable development was 0.09,which reflected that the tourism of the Taizishan National Forest Park is in an ideal state of ecological surplus and sustainable development. 

Abstract:Currently,litter size trait is an important indicator to measure sow fertility and play important roles in determining total income of pig farm in China. An accurate prediction of these traits in the early life of an animal will allow pig producers to adjust their management practices in order to cull bad sows early and improve the reproductive ability of core sows. However,there are many factors not only influence sow’s litter size trait,but also influence each other. Traditional prediction methods may not be powerful enough to capture complex interactions while avoiding overfitting. In this case,learning algorithms that can learn from current data to predict the animal’s future performance offers promise. In this study,firstly,the sow’s production data,including total number of piglets born (TNB),number born alive (NBA),number of healthy piglets(NHP),number of piglets aged 5 day (N5D) and number of piglets weight above 1 kg (NPWA1) were processed and described statistically. Then,the R-package Boruta was used to screen out important eigenvalues affecting the litter size traits of sows,such as breed,parity,mating season,delivery season,gestation period,interval birth and birth litter weight. Last,regression analysis was performed by traditional linear regression method and three different machine learning methods including decision tree (DT),K-nearest neighbor (KNN) and support vector machine (SVM). The evaluation index of model including R2 and MSE are obtained by ten flod cross validation. Additionally,modeling methods was assessed by these indexes and best model was screened scatter plot using a part of original data. The results showed that the R2 of all regression analysis methods in TNB,NBA,NHP,N5D NPWA1 was over 0.71 (0.71-0.88),which showed that the selection of characteristics is correct. The SVM model was not only significantly better than other machine learning methods (P<0.05),but also better than traditional regression method in predicting TNB,NBA,NHP,N5D and NPWA1. The SVM model of NPWA1 is the best in all models. Therefore,machine learning methods will become a new approach for pig producers to breed high-fecundity sows in the future.

Abstract:To investigate the expression of BMPR1A in various tissues during different physiological periods (follicular and luteal phases) and in ewes of different fecundity (monotocous and polytocous),and to analyze the association of its polymorphism with litter size in Small Tail Han (STH) sheep,qPCR was used to detect the expression of BMPR1A in 14 tissues in STH sheep,meanwhile,Sequenom MassARRAYSNP assay was applied to genotype three single nucleotide polymorphism sites (SNPs) of BMPR1A gene in different sheep breeds,and then the association between the BMPR1A polymorphism and litter size in STH sheep was analyzed. The results showed that the expression of BMPR1A in hypothalamus and ovary of polytocous ewes was higher than that of monotocous ewes,but did not reach a significant level (P>0.05). From genotyping,the genotype and allele frequencies of g.41128335A>T and g.41127600C>T loci of BMPR1A were significantly different (P<0.05) between polytocous and monotocous sheep breeds. The χ2 test indicated that the three SNPs were under Hardy-Weinberg equilibrium (P>0.05) in most of the sheep breeds. Association analysis showed that three loci of BMPR1A gene had no significant association with the litter size of different groups of STH sheep (P>0.05),and the litter size of mutation was higher than that of wild for g.41128335A>T and g.41127598A>G loci. Therefore,we concluded that there may be a certain positive correlation between the expression of BMPR1A gene and litter size in STH sheep,but the three SNPs had no significant association with the litter size of STH sheep,which indicated they may not be the key loci that affect the expression or function of BMPR1A. 

Abstract:Mycoplasma bovis is one of the serious pathogens causing bovine respiratory diseases. Meanwhile,M. bovis can cause a variety of clinical signs,including bronchopneumonia,mastitis,arthritis,genital tract inflammation,and tenosynovitis. Adhesion to airway epithelial cells is a key step for M. bovis colonization and invasion of cells. Adhesin is one of the main virulence factors of M. bovis. Research about attachment has become an important field of pathogenic mechanisms research of M. bovis. To further analyze the adhesion characteristics of the M. bovis VspX protein,experiments,including indirect immunofluorescence assay,adhesion assay of protein and mutant strain to embryonic bovine lung (EBL) cells,antibody inhibition adhesion detection,ELISA assay of protein and strains binding fibronectin (Fn),were carried out,to clarify the molecular mechanism of VspX protein adhesion. The results showed that the M. bovis VspX protein was located on the surface of the strain. The recombinant VspX protein (rVspX) was able to adhere to the embryonic bovine lung (EBL) cells. Compared with the M. bovis wild strain (M. bovis WT),the M. bovis VspX gene-deleted mutant strain (M. bovis ΔVspX) had a significantly decreased ability to adhere to EBL cells in vitro (P<0.05). The above results showed that the VspX protein was an adhesion-related protein. The anti-rVspX monoclonal antibody was able to inhibit the adhesion of M. bovis to EBL cells,which further confirmed the specificity of the adhesion. Also,the rVspX protein bound to Fn in a dose-dependent manner,and the M. bovis ΔVspX strain had a significantly lower adherence ability to Fn (P<0.05) than that of the M. bovis WT strain. These results further demonstrated the binding specificity of M. bovis VspX protein to Fn. And Fn was distributed on the surface of EBL cells. In summary,the study validated that M. bovis VspX protein was an adhesion-related protein with Fn binding properties,and the adhesion of VspX to EBL cells was mediated by the extracellular matrix component,Fn.

Abstract:Epidemic haemorrhagic disease virus (EHDV) is an arbovirus that seriously endangers ruminants. Currently,nine serotypes of EHDV have been discovered worldwide,and five of them are prevalent in China. Neutralization test is the gold standard for serotype identification of EHDV,which has the shortcomings of time-consuming,laborious and long experimental period. Therefore,establishing an accurate and rapid serotyping method for EHDV is of great significance for the prevention and control of this disease. In this study,the second gene segment (Seg-2),which determines the serotype of epizootic haemorrhagic disease virus (EHDV),was used as the target gene to establish a one-step RT-PCR method for serotype-specific detection of EHDV. The results of specificity test showed that the method could accurately identify different serotypes of EHDV,and had no cross-reaction with bluetongue virus,chuzan Virus and akabane virus. The results of sensitivity test showed that the detection limit of the EHDV nucleic acid for different serotypes could reach 102 copies. EHDV strains isolated from different times and different regions in China were identified by this one-step RT-PCR and the results showed that the 31 EHDV isolates belonged to five serotypes,inculding EHDV-1,-5,-6,-7 and -10. The results of the RT-PCR were completely consistent with the results of the serum neutralization test. The above results showed that the method established in this study had good specificity and high sensitivity,and could quickly and accurately identify the serotype of EHDV strains.

Abstract:After immunizing Bactrian camel with CRP as immunogen,the peripheral blood lymphocytes were isolated,the total RNA was extracted,and then the cDNA was obtained by reverse transcription. The target gene fragment was obtained by nested PCR and cloned on the arm of T7 vector of phage to construct the original phage library. After four rounds of biological panning,the phage library after panning was identified by Phage-ELISA. The recombinant plasmids of pET-28a and positive clones were constructed by BamH Ⅰ and HindⅢ double enzyme digestion and transformed into BL21 strain for low-temperature induction expression. The single domain antibody was purified by His-Ni affinity chromatography,and then the reactivity between the single domain antibody and CRP was identified by indirect ELISA. The results showed that the phage library with a capacity of 1.08×108 cfu was successfully constructed,and the gene insertion rate was 96.43% (27/28). Four positive clones were successfully constructed and expressed in BL21 cells. The molecular weight was about 22 ku. By ELISA,the four antibodies showed high affinity and specificity. The titer of V2 and V3 was 1∶3 200,which proved that the antibody could be applied to the development of practical detection methods.

Abstract:Recombinant expression vector of the Streptococcus agalactiae ATCC51487 gene was established by using PCR amplification,double digestion of EcoRⅠand XhoⅠ,and resistance screening,etc. Effects of induction temperature,concentration and time on the expression products were examined. The protein was purified by affinity chromatography and ion exchange chromatography,and the activity of SrtA was determined using energy transfer resonance. The results showed that after the srtAΔN82-pGEX- 6p - 1 vector was transformed into BL21 (DE3),a large amount of soluble protein were obtained by inducing at 1 mmol/L IPTG at 37℃ for 6 h. The purity of SrtA was higher than 85%. Moreover,the purified SrtA could significantly increase the fluorescence intensity when co-incubated with the substrate,indicating that the recombinant SrtA had good biological activity.

Abstract:With Penicillium digitatum DSM62840 as the object of research,the extraction conditions of related enzymes in the process of converting limonene to α-terpenol were optimized to obtain high activity. And limonene converting-enzyme was extracted by high pressure cell crushing method. Taking the limonene converting-enzyme activity as evaluation indicator,the response surface methodology was used to optimize the extraction technology based on single factor test. At the same time,the properties of limonene converting-enzyme were preliminarily studied. The results showed that the optimum conditions for extracting were as follows: disruption pressure of 100 MPa,crushing times of 6,and liquid-to material ratio of 15∶1 (mL/g). Under the conditions,the yield of α-terpenol was 855.75 mg/L,and the enzyme activity was 71.31 U. The optimum conversion time of limonene converting-enzyme was 4 h,and the highest enzyme activity was obtained in phosphate buffer. Limonene converting-enzyme might be cytochrome P450,and different metal ions have different effects on the enzyme: Fe2+ had slight inhibition on the enzyme,while Ca2+,Mg2+,Mn2+,Zn2+，Co2+，Ba2+，Na+，K+，Fe3+ and Ni2+ had different activation effects on the enzyme. SDS-PAGE analysis of the crude enzyme solution showed that the extraction effect could be better under the optimum conditions.

Abstract:The polypeptides were prepared from silver carp skin by the method of mixed enzymatic hydrolysis,and divided into SP1(＞6 ku),SP2(3-6 ku) and SP3(＜3 ku) by ultrafiltration. The antioxidant capacity in vitro of three polypeptides and the amino acid composition of SP1 and SP3 were analyzed. It was suggested that SP3 has the strongest antioxidant capacity in vitro. Subsequently,the antioxidant capacity in vivo of SP3 was measured. The results showed that the order of hydroxyl radical scavenging rate,superoxide anion radical scavenging rate and reducing ability in the three polypeptides was SP3＞SP2＞SP1,but there was no significant difference in chelating rate of copper ions. Analysis of amino acid composition showed that the percentage of hydrophobic amino acid in SP3 was significantly higher than SP1. Besides, compared with the injured group,SP3 group had higher indexes of liver and spleen. Furthermore,SP3 significantly increased the activities of SOD,GSH-Px and CAT and decreased the content of MDA in serum and liver. In conclusion,SP3 has better antioxidant activity than SP1 and SP2.

Abstract:Deep-frying is one of the traditional method of food processing with multiple advantages. However there are some safety hazard factors in deep-fired food which recently received many attentions. Advanced glycation end products (AGEs) is one of the main harmful compounds in deep-fried food which leads to human aging and insulin secretion defects. Nε-carboxymethyllysine (CML) and fluorescent AGEs are usually used as the marker of AGEs. Grass carp is the largest freshwater fish in China. A large number of grass carp is processed using deep-frying every year. Therefore it is necessary to study the level of CML and fluorescent AGEs in deep-fried grass carp and to find effective methods to reduce the content. The purpose of the study was to investigate the effects of frying time and batter on the content and distribution of AGEs in deep-fried fish nuggets and to develop processing method to reduce the safety concerns. In this study deep-fried fish nuggets (DFN) and breaded fish nuggets (BFN) were prepared using grass carp for 0,30,90,120,180,240 and 300 s. The AGEs content and physicochemical properties of the crust and internal of the fried fish were measured. The results showed that water loss oil absorption,Maillard reaction and oil oxidation mainly occurred on the fish crust during frying. Therefore the CML content in the fish crust of DFN and BFN was 5.6 and 6.4 times that of the interior,respectively. Extending frying time resulted in higher water loss and oil absorption in both the fish crust and interior while the malondialdehyde content firstly increased and then became stable. Extending frying time could also promote Maillard reaction in the fish crust and significantly increased the content of CML and fluorescent AGEs. Compared with DFN,the BFN crust had lower moisture content and higher fat content. The Maillard reaction and fluorescent AGEs content rapidly increased during the late frying period but the use of the batter prevented the protein from directly contacting the high-temperature oil and thus the CML and fluorescent AGEs content in BFN crust were significantly reduced by 34.6% and 20.8% compared with DFN at 300 s. The use of the batter also significantly reduced the CML content in the interior of fish but had no significant effect on the fluorescent AGEs content. In conclusion the use of the batter and reducing the frying time could reduce the AGEs content in the fish crust and interior.The study provided basic information for the development of the healthy aquatic food.

Abstract:To study the effects of micro-flowing water treatment on the crucian carp flesh quality,the main nutritional components,taste characteristics,odour characteristics,and volatile components of the pond-cultured crucian carp (Carassius auratus gibelio) flesh processed by the micro-flowing system were measured after different treatment durations (0-9 d).The results showed that the micro-flowing water treatment hardly influenced the moisture,crude protein and crude fat contents in cultured crucian carp flesh(P>0.05),whereas it had significant effects on the ash,muscle glycogen,total sugar content in fish flesh as well as on the taste,odour and sensory scores (P<0.05). With the extension of micro-flowing water treatment time,the glycogen and total sugar contents significantly decreased while the ash content significantly increased (P<0.05). According to the results of electronic tongue and electronic nose detection,the micro-flowing water treatment can significantly change the taste and odour characteristics of crucian carp flesh. As the micro-flowing water treatment time extended,the content of odour volatiles in the flesh of the crucian carp significantly decreased,and the representative flavor substance in the fish significantly increased. Meanwhile,the odour,taste,texture,and the sum scores of steamed fish were also greatly raised. The sensory score of the crucian carp flesh processed for 7 d was higher than that of samples processed for 0 d,1 d,3 d,and 5 d. However,there was no difference between the samples processed for 7 d and 9 d with micro-flowing water treatment. In summary,the short-time micro-flowing water treatment (≤7 d) hardly affected the crude protein and crude fat contents of crucian carp flesh,but it could remarkably improve the flesh quality of crucian carp with the most suitable treatment duration (7 d).

Abstract:Freezing is a common processing method used in the production of surimi. In order to prevent quality deterioration during freezing storage,commercial cryoprotectant (4% sucrose and 4% sorbitol) is added,which introduces excessive sweetness and calorie and limits partial consumers. With low sweetness,rich probiotic function and reasonable structure,inulin is a potential cryoprotectant. Therefore,it is essential to conduct a systematic research on the freezing resistance of inulin with different degree of polymerization for surimi. The purpose of the study was to investigate the effects of inulin with different degrees of polymerization on protein denaturation and quality deterioration of surimi,and to reveal the relationship between protein biochemical properties and gel properties. In this study,frozen silver carp surimi was prepared by adding short chain inulin (degree of polymerization 2-6),natural inulin (degree of polymerization 10-23) and long chain inulin (degree of polymerization 23-46). The protein biochemical and gel’s indicators were measured during frozen storage. Furthermore partial least squares regression analysis(PLSR) was performed to analyze the relationship between protein and gel’s indicators. Results showed that,all of the inulin had anti-freezing effect on surimi. Short chain inulin had the best effect among these,and could significantly inhibit the decrease of the salt-soluble protein content,Ca2+-ATPase activity,sulfhydryl content and the increase of surface hydrophobicity (P＜0.05). Meanwhile,secondary structure,sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel properties (water holding capacity,gel strength and texture) of sample added with short chain inulin was the closest to those of fresh surimi. In addition,salt-soluble protein content,secondary structure,surface hydrophobicity and sulfhydryl content had sequentially decreased influence on gel qualities,which could be used as main indexes indirectly evaluating gel quality of frozen surimi. But Ca2+-ATPase activity exerted little influence. This study provided a reference for the freezing denaturation of surimi and the development of new cryoprotectant.

Abstract:Mechanized transplanting of rapeseed is an efficient planting mode. However,the complicated structure and instability of seedling detaching process affects the transplanting quality of rapeseed substrate seedling. An inclined detach device for rapeseed substrate seedling transplanter was developed to solve the problem that the seedling transplanting device of the traditional transplanting machine is easy to tip over during the transplanting of rapeseed. The structural composition and the seedling detach processes were analyzed. The key components were designed and the main structural parameters of the seedling detach device were determined. A mechanical model of seedlings in the transporting and separating stages of the seedling detach process was constructed to analyze the main factors affecting the stability of the seedlings. The results showed that the seedling block was stable during the transporting stage when the frictional characteristics of the seedlings were constant and the inclination angle of the belt was between 24.5° and 35.0°. The lager of the clamping force,the better of the separation effect in the separating stage. The optimized key parameters of the seedling detach device included 30° inclination angle of the belt,lager than 0.8 N clamping force(fj1),and 0.5-0.8 MPa air pressure of the cylinder(P). The results of bench experiment showed that the capsizes rate of seedlings block was 4.2% and the detaching rate was 92.5%,meeting the needs of seedling detaching of rapeseed substrate seedling. It will provide a reference for designing detach device of rapeseed substrate seedling transplanter

Abstract:A certain combine harvester cutting platform and grain allocation device was used to establish the geometric model based on Pro/E software and reasonably simplify by importing the model established into ADAMS. The virtual prototype model was obtained by adding constraints,loads and drives,and kinematics simulation was carried out on this basis. The range of the threshing device and other relevant parameters were obtained through the establishment of different drives and the simulation analyses of different working conditions of the threshing device. The results showed that only when the speed ratio was λ>1,the motion trajectory was cycloid,forming a closed buckle so that the spring teeth can push the crop stalk backwards. When the reel ratio of the reel is 1.55,it is closest to the best effect of the reel,which can meet the working requirements of normal work and avoid unnecessary falling loss. The maximum and minimum forward movement distances of the reel increase with the increase of pull-grain speed ratio. The forward movement range of the reel is 0.00-0.38 m.

Abstract:A kind of water chestnut （Eleocharis dulcis (Burm. f.) Trin. ） peeler using the combined cutting method of flat blade to remove top bud,inclined blade to remove bottom,and arc blade to remove lateral peel was designed to solve the problems of the irregular shape,large peeling loss and uncleanness of water chestnut. By measuring and modeling the shape parameters of water chestnut,the outer contour curve of water chestnut was fitted to determine the range of structural parameters of blades. Based on 3D printing technology,the single factor experiment was used to determine the effects of rotary speed,inclination angle and length of the inclined blade,and chord length of the arc blade on loss rate and removal rate of water chestnut. The structural parameters and motion parameters were optimized. The results showed that the removal rate and the loss rate of the peeler designed was 93% and 24.4% when the rotary speed was 40 r/min,the inclination angle and length of the inclined blade were 82° and 14 mm,and chord length of the arc blade was 22 mm(42.75 mm in diameter),significantly higher than that of manual peeling and mechanical friction peeling.

Abstract:Because of the existence of soil adhesion characteristics,it often causes soil to adhere to the surface of working parts,which increases the energy consumption of equipment and even prevents normal operation. With the improvement of modern agricultural mechanization and the increasing variety of soil-engaging components,researchers put forward higher requirements for designing and optimizing soil-engaging components. In this study,a paddy field soil adhesion measuring instrument was designed. The single factor experiment was carried out with normal pull-out velocity vn,tangential velocity vτ and paddy field soil spatial depth as influencing factors. The factors affecting the contact interface adhesion were preliminarily obtained. The results showed that the soil adhesion increased with the increase of normal drawing speed vn and tangential velocity vτ,and first increased and then decreased with the increase of spatial depth of paddy field soil.

Abstract:Dongfanghong-LX754 tractor and Huaifeng1LS-740 subsoiler were used to study the effects of different positions of farm tools on the vibration characteristics of tractor with suspended farm tools. CATIA software was used to establish simplified geometric model of tractor and farm tools. MATLAB was used to write random road surface file,which was imported into ADAMS to write tire property file and establish the mechanical system model of farm tool,tractor and road surface. Effects of the parameters of the suspension device on the vertical vibration acceleration of the driver,the pitch vibration angular acceleration at the seat installation and the vertical vibration acceleration of the tractor body were obtained by simulation. The results showed that when the angle between the inner lifting arm and the horizontal direction increased from 20° to 70°,the driver acceleration peak value reduced to 17.61 from 30.09 m/s2. The peak frequency of vertical vibration increased from 1.36 to 2.12 Hz. Seat installed in longitudinal vibration angular acceleration peak value reduced to 7.56 from 11.12 rad/s2. Tractor barycenter vertical vibration acceleration peak value reduced to 29.33 from 42.42 m/s2. It will provide an important reference for designing vibration damping system of tractor.

Abstract:The effects of different holding times on the biochar yield,composition,pH,electrical conductivity and pore structure of five kinds of straws including rice,wheat,corn,rape and cotton were investigated.Correlation between the physical and chemical properties of different biochars was analyzed.The results showed that effects of straw type and holding time on the physicochemical properties of biochar fertilizer were significant (P<0.05).The biochar yields and the carbon conversion efficiency of straws ranged from 41% to 61%,and 53% to 65%,respectively.With the increase of holding time,the biochar yields decreased,while the pyrolysis degree and the fixed carbon contents of biochars increased.The pH and electrical conductivity increased with the increase of holding time.The holding time was negatively correlated with carbon yield,H,O contents and volatile matter content of biochars,and positively correlated with fixed carbon content.The optimal holding time is 60-90 min,and the biochars obtained under this condition has a rich pore structure with smooth surface.The biochars with lower H/C and higher pH and electrical conductivity can be used as a good carbon-based fertilizer additive material.