2000年~2018年中国食用菌出口国际竞争力分析

利用我国省级面板数据对食用菌出口国际竞争力进行分析,结果表明,近年来我国食用菌出口国际竞争力呈现明显上升趋势,但是我国30个省市间食用菌出口贸易竞争力呈现明显的区域异质性,其中北京、上海、广东等地的食用菌出口贸易竞争力明显高于中部和西部地区。农业产值、城市化水平、食用菌生产规模进口国购买力与食用菌出口国际竞争力之间为显著的正相关关系,而汇率水平、食用菌产品价格与食用菌出口国际竞争力之间为显著的负相关关系。     

利用盈亏平衡分析法对奶牛场经济效益的分析

盈亏是判断企业经济效益的一个重要标准,而盈亏平衡分析即量本利分析则是了解企业生产和销售后果、为其未来生产和销售决策提供依据的一种重要方法。选择当前奶牛场盈亏问题为研究对象,在简要介绍盈亏平衡分析方法的基础上,通过分析和对比西安光明荷斯坦奶牛育种有限公司和杨凌示范区良种奶牛繁育中心的相关资料,得到了两牛场在现有条件下的保本点分别为265头和291头,在目前的经营规模下两场均不能赢利。在现有饲养规模下,当产奶量分别为31．20和33．69k时,两场可处于盈亏平衡点。当产奶量低于118638．90kg时,采用后者的经营模式成本较前者高。降低总成本、提高产奶母牛的比例等措施可以降低保本点产量,从而提高企业经济效益。     

关于拓扑度计算的若干结果及应用

通过构造距离函数d（x）,并结合拓扑度的计算,利用区域的边界特征,得到一些新的不动点存在定理,所得结果可以广泛用于一些非线性微分方程解存在性问题的讨论中.     

磁化水处理对苜蓿根瘤菌生长和结瘤固氮的影响

为明确磁化水对根瘤菌生长及结瘤固氮的作用,测定在2万Gs恒定磁场下处理的磁化水对苜蓿根瘤菌生长及其结瘤固氮的影响.结果表明:不同磁化次数的磁化水均能显著影响XGL026菌株生长,降低OD值,磁化水培养基中的活菌数为普通培养基的86.96%～65.72%,菌数降低幅度随磁化次数增加而增大,磁化3次以上的磁化水对活菌数的降低效应极为显著(P<0.01).在盆栽苜蓿上接种绿色荧光蛋白基因(GFP)标记菌株XGL026-GFP,采用磁化水灌溉对根瘤菌在根际土壤中的存活和定殖具有抑制作用,苜蓿单株结瘤数与普通水对照相比平均减少46.4%(P<0.01).磁化水处理的苜蓿地上、地下部分的固氮率分别降低21.06%和20.48%,固氮量分别降低26.64%和37.5%,植株干物质重分别减少27.62%和13.46%.表明磁化水处理对苜蓿根瘤菌的生长、定殖和固氮及植株干物质重均有抑制作用.     

高寒地区燕麦根际联合固氮菌研究Ⅲ固氮菌对燕麦生长的影响及其固氮量测定

利用稳定性15N同位素稀释法研究了接种固氮菌株对燕麦生长的影响及固氮量.结果表明,接种不同供试固氮菌株对燕麦生长的影响不同,大多数菌株明显促进燕麦生长(株高、根长、根表面积和生物量),部分菌株则对燕麦生长影响不明显.菌株固氮百分率和固氮量差异较大,固氮百分率为13.78%～63.96%,大于50%的有5株(Azotobacter sp.ChO7、Pseudomonas sp.ChO3、Azotobacter sp.ChO4、Azotobacter sp.ChO5和Azospirillum lipoferum ChO6);固氮量为0.065 3～0.315 8 mg/株,Azotobacter sp.ChO4最高,其次是 Pseudomonas sp.ChO3、Azotobacter sp.ChO7、Azotobacter sp.ChO5和A. lipoferum ChO6等.综合固氮量和对燕麦生长影响认为,菌株A. lipoferum ChO6、Azotobacter sp.ChO4、Pseudomonas sp. ChO3、Azotobacter sp.ChO5和Azotobacter sp.ChO7等可作为燕麦固氮菌肥研制的菌种.     

The Performance of Pea (Pisum sativum L.) and its Role in Determining Yield Advantages in Mixed Stands of Pea and Oat (Avena sativa L.)

On a brown warp soil (Fluventic Eutrochrept) near Goettingen, Germany, conventional leafed pea ( Pisum sativum L. cvs Messire and Bohatyr) and semileafless types (cvs Profi, Juno and Azur) were grown in mixed stands together with oat ( Avena sativa cvs Alf and Lutz) in substitutively designed experiments from 1995 to 1997. Oat was the dominant component. Crowding coefficients for oat averaged 7.4. No relationship could be detected between the crowding coefficient of oat and any yield advantage from the mixture. Crowding coefficients for pea varied substantially, between 0.1002 (Juno and Alf in 1996) and 0.2979 (Bohatyr and Alf in 1996). Crowding coefficients for semileafless pea cultivars were smaller than for conventional leafed types. The yield advantage of the mixture increased as the crowding coefficient of pea increased. The maximum yield increase for the mixture was achieved when the relative yield total (RYT)=1.17 or + 11 dt grain DM ha^–1 for mixtures of the long-strawed conventional leafed cultivars Bohatyr and Alf (in 1996). The crowding coefficients of pea were positively correlated with the level of symbiotically fixed N₂ in the mixed stands. When N₂ fixation with mixed cropping was about 30 kg N ha^–1, RYT was unity. Increasing symbiotic N₂ in the mixtures resulted in increasing yield advantages in the mixture. Short-strawed pea cultivars seem unsuitable for mixing with oat. Plant height of pea appeared to be more important than plant leaf type. Accordingly, mixtures containing the long-strawed semileafless pea cultivars Profi and Alf were more successful. It is concluded that increased competitiveness of the pea component in the mixture with oat entails increasing the level of symbiotic N₂ fixation including resource complementarity and thus yield advantage in the mixed stands.     

Coupled Fixed Point Theorems for Set-valued Nonexpansive Mappings

In strictly convex Banach spaces, by Set valued mappings being monodromied via the optimal approximation for weakly compact convex set and using contraction mapping sequence to approximate nonexpanding mapping.The author has obtained theorems of coupled fixed point for set valued nonexpansive mappings.     

红壤坡地土壤侵蚀定位土芯Eu示踪方法研究

利用人工模拟降雨装置和径流小区观测法相结合,详细阐述了Eu定位土芯的布设、取样及分析方法。试验研究结果表明,Eu定位土芯中子活化分析技术可以准确地测定不同地形部位的土壤侵蚀量。坡面侵蚀泥沙的分布表现为沉积、侵蚀交错出现,呈现波形变动,符合多项式的变化,相关关系也较好。休闲裸坡地上,整个坡面大都表现出上坡的上中部为侵蚀运移,下坡为沉积。布样80d后,发现测定流失泥沙结果与模型拟合结果的相关关系较好,准确度也较高。因此建议一般应在Eu土芯布样3个月后取样为好。预测结果和实际情况也比较相近,最大误差为7.671t/hm2,取样误差为1mm。     

Genetic analyses of hunting traits in leashed and non-leashed test systems in Norwegian Elkhound

ABSTRACT

Norwegian Elkhound Grey is used for both leashed and non-leashed tracking. This study provides influence of fixed effects and estimates of genetic parameters of traits related to both types of tracks. In total, 5393 records from 1991 animals tested in the years 1995–2014 on lashed performance (5 traits), and 5405 records from 2070 animals tested in the years 2005–2014 on non-leashed performance (10 traits) were included in the dataset. The pedigree file contained 8623 animals. Heritabilities were generally low for the non-leashed traits and a bit higher for the leashed traits. Genetic correlations within trait group were very highly positive for the leashed dog traits, but variable among some traits in the non-leashed group. Genetic correlations between performance traits in the two groups were generally negative and unfavourable. Genetic trends were generally positive for the time periods.     

粮食安全视角下东北地区耕地利用功能转型特征研究

系统考察东北地区耕地利用功能转型对粮食生产的影响,有助于从国家全局层面把握耕地与粮食之间的关系,从而为我国实现农业现代化和粮食安全高质量发展提供科学参考。本文基于2011—2020年全国省级面板数据,采用熵权法、双固定模型等估计方法,明晰东北地区耕地利用功能转型特征及其影响国家粮食安全的作用机制。结果表明：2011—2020年,我国粮食安全水平呈上升态势,东北地区耕地利用功能转型有效赋能全国粮食安全。在地区异质性研究中,辽宁省、黑龙江省耕地利用功能转型的粮食安全保障效应更加明显,吉林省作用渠道有待畅通。在维度异质性研究中,东北地区耕地利用功能转型主要通过促进粮食数量安全和粮食经济安全保障我国粮食安全,粮食生态质量保障效应不明显。据此,为了使东北地区耕地利用功能转型更好地促进国家粮食安全,从提供东北地区耕地利用与粮食生产经济补贴、因地制宜制定东北地区耕地利用功能转型策略、打造以生态质量为导向的“优质粮食工程”等方面提出建议。