Moderate scale and realization potential of new citrus-planting business entities in hilly and mountainous areas in China

The natural and economic conditions of agricultural resources vary greatly in China,especially in hilly and mountainous areas.The phenomenon of land fragmentation has become increasingly prominent,so that large-scale operations cannot be fully achieved in a short period of time,and the centralized and continuous scale of operations cannot be realized in China.In addition,with increasingly strict farmland protection and agricultural land use control systems,the issues of nongrain production and nonagricultural cultivated land use have become increasingly restricted.Thus,it is quite necessary to determine the appropriate scale of operations and the means to achieve moderately scaled operations for the new business entities.On the basis of microsurvey data for 108 new citrus-planting business entities in the modern agricultural park in the Chongqing's Jiangjin District,an area with long citrus-planting history,we measured the moderate scale of new citrus-planting business entities to maximize profit using a translog growth model.According to the projection pursuit model,we evaluated the suitability conditions of citrus planting in garden land,woodland,grassland,and general cultivated land in the study area.We then explored the potential for new moderate-scale business entities within different farming radii.The results showed that large-scale planting conditions of citrus in garden land,forest land,grassland,and general cultivated land in the study area were suitable,and the proportion of high-suitable and mediumsuitable land was 73.42%.Under the existing social and economic conditions,the moderate scale of new citrus-planting business entities in the study area was 1.8–2.7 hm^(2).In particular,its rankings from large to small were agricultural enterprises(17.19–25.78 hm^(2)),farmer cooperatives(16.88–25.33 hm^(2)),big growers and breeders(6.39–9.59 hm^(2)),and family farms(5.02–7.53 hm^(2)).In the sample of 108 households,only 47.22%of the entities achieved moderate-scale operation,of which 25%of the entities achieved a scale greater than moderate operation.However,52.78%of the entities achieved a scale of less than moderate operation.These entities would have to transfer the surrounding adjacent garden land,forest land,grassland,or general cultivated land to achieve largescale land management.The land area of the adjacent gardens in a 1000 m farming radius could meet the moderate-scale operation demand of the vast majority of new business entities.For the vast majority of new business entities,the land area of the adjacent woodland,grassland,and general cultivated land could supplement the garden land to achieve moderate-scale operation in a 500 m farming radius.If the land area with moderate suitability and high suitability is prioritized,the land area in the adjacent gardens in the 1000 m farming radius could meet the moderate-scale operation demand for the vast majority of new business entities.Within the 500 m farming radius,the vast majority of new business entities have achieved moderate-scale operations if the land area adjacent to forest land,grassland,and general arable land was supplemented by gardens;however,a few entities could not achieve moderate-scale operations.From the village perspective,gardens were prioritized.Sixteen villages had planting areas and planting suitability that exceeded the average level of the study area,accounting for 23.53%.If combined with the reserve potential of the garden land,eight villages could improve their potential,accounting for 11.76%.Therefore,the conditions of large-scale citrus planting in the study area should be further improved,and the scale expansion of new citrus-planting business entities should receive additional scientific guidance.

Research on Safety Risk Assessment Method for Large Scale Field Operation Project

By applying man-machine-environment system engineering theory, safety risks on large scale field operation project have been evaluated in this article. The factors concerning with the man, machine and environment in system were proposed separately. The value for lowest indexs was determined by decision-making of expert group. The weights were calculated based on AHP, and then safety risk assessment in different layers was made. The results show that the assessment method is reasonable, and it is significant for large scale field operation project safety managerment.

Reform Paths of Rural Land Property Rights System in the Context of Agricultural Modernization

The reform of rural land property rights system can promote large-scale and intensive agricultural production,improve the quality of laborers,improve agricultural production efficiency,increase farmers'income,and effectively promote the development of agricultural modernization.In the context of the reform of the"separation of three powers",the rural land property rights system still has problems in terms of ownership,use rights,disposal rights,and income rights,which affect the healthy development of agricultural modernization.In this situation,it is necessary to further clarify the subject of rural land ownership,thoroughly improve the right to use rural land,vigorously improve the right to dispose of rural land,effectively protect the right to benefit from rural land,and deeply promote the reform of the rural land property rights system in order to effectively promote the development of agricultural modernization.

在深化可持续发展研究中发展地理学

可持续发展研究对地理学提出了挑战，也是地理学的发展机会，地理学家有责任在发展自己学科的同时把可持续发展的研究引向深入。地理学家要能对似乎已得到广泛认同的概念提出挑战性的思想，要在观念形态、经济－社会体制、科学技术三个层次上把可持续发展的论题引向深入，同时要对论题的空间尺度和时间尺度有明确的界定，尤其要重视区域尺度和近期的可持续发展研究，重视可持续发展思想和战略的可操作性。

中医健康量表的建立和初步评价

从中医学关于健康的概念和中医学健康观的基本特点出发,吸取现代科学研究方法有关"操作化"的思路和程序,构建基于中医学理论的中医健康量表的预试稿(iHSTCM)。2002年11月—2003年1月在广州市以652例问卷调查数据,进行内容筛选,通过数理统计方法,确立了中医健康量表(HSTCM)的领域、方面和条目。中医健康量表具有理论和应用上的合理性,可以进一步应用于中医药临床。

手机依赖的概念内涵及其现状调查——一项基于大学生群体的研究

本研究在文献回顾和访谈的基础上，以使用与满足理论、媒介系统依赖理论和行为成瘾理论为理论框架，从物质性依赖、社会性依赖和心理性依赖三个层面测量“手机依赖”。通过筛选条目、形成初步量表、预测试和正式测试，形成有较好信度和效度的量表。经探索性因素分析和验证性因素分析发现，对手机的物质性依赖包括“消遣型”“讯息型”和“指导型”，社会性依赖包括“社会意义”和“个体意义”，心理性依赖体现为“戒断性”和“生理反应”。研究进一步对当代大学生的手机依赖现状以及有关影响因素进行了探索。

L^p CONTINUITY OF HRMANDER SYMBOL OPERATORS OpS_(0,0) ~m AND NUMERICAL ALGORITHM

If we use Littlewood-Paley decomposition, there is no pseudo-orthogonality for Ho¨rmander symbol operators OpS m 0 , 0 , which is different to the case S m ρ,δ （0 ≤δ 〈 ρ≤ 1）. In this paper, we use a special numerical algorithm based on wavelets to study the L p continuity of non infinite smooth operators OpS m 0 , 0 ; in fact, we apply first special wavelets to symbol to get special basic operators, then we regroup all the special basic operators at given scale and prove that such scale operator’s continuity decreases very fast, we sum such scale operators and a symbol operator can be approached by very good compact operators. By correlation of basic operators, we get very exact pseudo-orthogonality and also L 2 → L 2 continuity for scale operators. By considering the influence region of scale operator, we get H 1 （= F 0 , 2 1 ） → L 1 continuity and L ∞→ BMO continuity. By interpolation theorem, we get also L p （= F 0 , 2 p ） → L p continuity for 1 〈 p 〈 ∞ . Our results are sharp for F 0 , 2 p → L p continuity when 1 ≤ p ≤ 2, that is to say, we find out the exact order of derivations for which the symbols can ensure the resulting operators to be bounded on these spaces.

Changing Trend and Influencing Factors of Rice Production Cost in China

Rice is one of the three major food crops in China.The change of its production cost is related to food security and farmers'income in China.This paper analyzes the changing trend of rice production cost in China from 2009 to 2019,analyzes the factors leading to the change from the aspects of land scale,labor force structure,agricultural science and technology level,etc.On this basis,this paper puts forward measures and suggestions to reduce rice production cost and improve farmers'income.

A restriction theorem for Grushin operators

We study the Grushin operators acting on Rx d1× Rt d2 and defined by the formula L -∑ j d1=1 xj-∑ j d1=1｜xj｜2 ∑ k d2=1 2 tk. We establish a restrictiontheorem associated with the considered operators. Our result is an analogue of the restriction theorem on the Heisenberg group obtained by D. Muller [Ann. ofMath., 1990, 131： 567-587].

Multiobjective Optimal Water ResourcesManagement for a Large River Basin

The availalability. use, development, and management of water resources are receivingincreasing attentioll worldwide. As demands for water continues to grow and the resources continue todwindle or at best remain constant at some level, it has become increasingly necessary to develop moreand more methods for the managaement of this scarce resource especially in arid and semiarid regions.The necessity of integrated planning and management of the basin arises because of insufficient anderratic nature of the rainfall. The purpose of this paper is to determine the optimal operation policy ofthe water resources for the river basins to meet the multi-objective demands of water requirements. Anoptimization approach has been developed to aid decision making in the real time allocation of waterwithin t he context of a large-scale, multi-objective, complex river system. The optimization approach isbased on the Progressive Optimality Algorithm, Golden Search techniqlle, and the ε-constraint method.As a case study, the present methodology is applied to the Yellow River Reservoir system in China andpresented in a companion paper in this issue.