Based on SPOT-5 images, 1：1 million topographic maps, the maps of the returning farmland to forest project and the Chongqing forest project, social and economic statistics, etc., this paper identifies the features an...Based on SPOT-5 images, 1：1 million topographic maps, the maps of the returning farmland to forest project and the Chongqing forest project, social and economic statistics, etc., this paper identifies the features and factors influencing farmland marginalization. The results showed： （1） During 2002-2012, the rate of farmland marginalization was 16.18%, which was mainly found in the high areas of northern Qiyao mountains and the medium-altitude areas of southern Qiyao mountains. And this farmland marginalization will increase, associated with non-agriculturalization of rural labourers and aging of the remaining labourers. （2） Elevation, distance radius from villages and road connections had a great in- fluence on farmland marginalization. Farmland marginalization rates showed an increasing trend with the increase of elevation, and 60.88% of the total farmland marginalization area is found at an altitude greater than 1000 m above sea level. The marginalization trend also increases with slope and distance from the distribution network. （3） Farmland area per labourer and the average age of farm labourers were major factors driving farmland marginalization. Farmland transfer and small agricultural machinery sets affect farmland marginalization with respect to management and productivity efficiency. （4） Farmland with ＂comparative-disadvantage-dominated marginalization＂ accounted for 55.32% of the total farmland marginalization area, followed by ＂location-dominated marginalization＂ （33.80%）. （5） According to the specifics of each real situation, different policies are suggested to mitigate the margin- alization. A ＂continuous marginalization＂ policy will encourage the return of farmland to forest in ＂terrain-dominated marginalization＂. An ＂anti-marginalization＂ policy is suggested to create new rural accommodation and improve the rural road system to counteract ＂terrain-dominated marginalization＂. And another ＂anti-marginalization＂ policy is planned to improve management and micro-mechanization for ＂comparative-disadvantage-dominated marginalization＂. A new idea was developed to integrate high resolution remote sensing and statistical data with survey information to identify land marginalization and its driving forces in mountainous areas.展开更多
The analysis of company data useful for economic decisions,if not interpreted in an overall view of the company situation,can lead to wrong conclusions.This is the case when a company has to choose between several sal...The analysis of company data useful for economic decisions,if not interpreted in an overall view of the company situation,can lead to wrong conclusions.This is the case when a company has to choose between several sales options for one or more products in the presence of a limiting factor.The continuation of the investigation often denies the initial analysis.Not everything is as it appears,therefore,at the beginning of the deepening of the data useful for economic decisions.As it is well known,the choices of profitability concerning the planning of the sale of company products take place,at least in the majority of cases,through the determination of the contribution margin,i.e.the profitability margin connected to the individual goods/services sold by the companies(selling price net of variable costs).The contribution margin can be determined with four objectives:(1)Determination of the yield of the single product,net of variable costs only.In this case,the margin defines unitary,from net product yield to unitary contribution margin.(2)Determination of the return on total sales of an individual product,net of variable costs.In this hypothesis,reference is made to the first level(or gross)contribution margin.(3)Determination of the ability of the individual product to contribute to the coverage of fixed costs common to the company.This margin is determined net of special product variable and fixed costs.This aggregate is defined as a Level II(or semi-gross)margin.(4)Determination of the useful value in the planning choices in case of presence of scarce productive factors.In this case,it must identify the so-called unitary margin for low factor.Here we will only deal with the problem of the use of the contribution margin in the presence of rare factors.To complete the analysis,below are some very brief considerations regarding,respectively,the unitary,level I,and level II contribution margin in order to better understand where the problem of the most convenient choice of income is located in the event of the presence of rare production factors,especially in an environment characterized by a plurality of sales options.展开更多
According to the differences of structural deformation characteristics, the southern margin of the Junggar basin can be divided into two segments from east to west. Arcnate thrust-and-fold belts that protrude to the n...According to the differences of structural deformation characteristics, the southern margin of the Junggar basin can be divided into two segments from east to west. Arcnate thrust-and-fold belts that protrude to the north are developed in the eastern segment. There are three rows of en echelon thrust-and-fold belts in the western segment. Thrust and fold structures of basement-involved styles are developed in the first row, and decollement fold structures are formed from the second row to the third row. In order to study the factors controlling the deformation of structures, sand-box experiments have been devised to simulate the evolution of plane and profile deformation. The planar simulation results indicate that the orthogonal compression coming from Bogeda Mountain and the oblique compression with an angle of 75° between the stress and the boundary originating from North Tianshan were responsible for the deformation differences between the eastern part and the western part. The Miquan-Uriimqi fault in the basement is the pre-existing condition for generating fragments from east to west. The profile simulation results show that the main factors controlling the deformation in the eastern part are related to the decollement of Jurassic coal beds alone, while those controlling the deformation in the western segment are related to both the Jurassic coal beds and the Eogene clay beds. The total amount of shortening from the Yaomoshan anticline to the Gumudi anticline in the eastern part is -19.57 km as estimated from the simulation results, and the shortening rate is about 36.46%; that from the Qingshuihe anticline to the Anjihai anticline in the western part is -22.01 km as estimated by the simulation results, with a shortening rate of about 32.48%. These estimated values obtained from the model results are very close to the values calculated by means of the balanced cross section.展开更多
随着风电在电力系统中占比的逐年攀升,传统机组单独承担调频任务已难以适应其需求变化。因此,风电需具备与传统电源协同调节系统频率的能力。首先,基于风电调频的快速性和火电调频的持久性,设计了一种以火电为主、风电为辅的联合一次调...随着风电在电力系统中占比的逐年攀升,传统机组单独承担调频任务已难以适应其需求变化。因此,风电需具备与传统电源协同调节系统频率的能力。首先,基于风电调频的快速性和火电调频的持久性,设计了一种以火电为主、风电为辅的联合一次调频控制策略。其次,充分考虑风电场内各机组的运行差异,提出一种基于裕度因子的功率分配策略,有效挖掘各机组的调频能力并确保其安全运行。同时,提出一种针对风电场内风机分组运行的持久备用功率再分配策略。该策略预先安排少数风电机组以低减载率的超速模式运行,当调频风机退出频率支撑后,减载风机将根据调频风机的转速,采用一种基于转速反比例因子的差异化能量分配策略,以有效弥补调频风机退出后的能量缺额,缓解频率二次跌落(secondary frequency drop,SFD)。仿真结果表明,所提策略能够实现风火联合参与一次调频,在保证经济性和可靠性的前提下,充分发掘风电调频性能,有效改善电力系统频率响应特性。展开更多
胶莱盆地东北缘是胶东东部地区近年来发现的一个重要金成矿区,自1989年蓬家夼金矿(大型)发现以来,先后在牧牛山为中心的胶莱盆地东北缘发现了宋家沟(大型)、土堆-沙旺(大型)、辽上(特大型)等金矿床(点)(李国华等,2016),初步统计全区金...胶莱盆地东北缘是胶东东部地区近年来发现的一个重要金成矿区,自1989年蓬家夼金矿(大型)发现以来,先后在牧牛山为中心的胶莱盆地东北缘发现了宋家沟(大型)、土堆-沙旺(大型)、辽上(特大型)等金矿床(点)(李国华等,2016),初步统计全区金资源量已超过223 t(Bo Junwei et al.,2024)。展开更多
目的探讨吻合器痔上粘膜环切(procedure for prolapse and hemorrhoids,PPH)联合外痔切除术治疗混合痔后患者出现肛缘水肿、慢性疼痛的危险因素,为临床预防相关并发症提供指导建议。方法选取本院2020年1月至2022年12月采用吻合器手术切...目的探讨吻合器痔上粘膜环切(procedure for prolapse and hemorrhoids,PPH)联合外痔切除术治疗混合痔后患者出现肛缘水肿、慢性疼痛的危险因素,为临床预防相关并发症提供指导建议。方法选取本院2020年1月至2022年12月采用吻合器手术切除治疗的混合痔患者300例进行临床研究,根据患者术后是否并发肛缘水肿、慢性疼痛将患者分别进行分组,对比各组患者的一般资料、手术情况及术后康复资料,分析引起肛缘水肿、慢性疼痛的危险因素。结果300例吻合器手术切除治疗的混合痔患者,其中发生肛缘水肿67例,未发生肛缘水肿233例,肛缘水肿患者的高血压占比、肥胖占比、便秘占比大于非水肿组,差异具有统计学意义(P<0.05);Logistic回归模型分析结果:合并肥胖、合并便秘、是发生肛缘水肿的独立危险因素(P<0.05)。300例吻合器痔切除手术切除的患者,其中发生慢性疼痛34例,未发生慢性疼痛266例,慢性疼痛组年龄≥65岁占比、糖尿病占比、肥胖占比、便秘占比的患者占比大于非慢性疼痛患者,差异具有统计学意义(P<0.05);Logistic回归模型结果显示:合并肥胖、合并便秘是发生慢性疼痛的独立危险因素(P<0.05)。结论肥胖、合并便秘会增大混合痔患者吻合器手术切除联合外痔切除术治疗后发生肛缘水肿的风险,合并肥胖、合并便秘会增大其发生慢性疼痛的风险。展开更多
Taken as an example the Upper Permian reef section on the carbonate platformmargin at Ziyun, Guizhou, the paper discusses the missing time of a hiatus surface, an impor-tant problem in chemical sequence stratigraphy, ...Taken as an example the Upper Permian reef section on the carbonate platformmargin at Ziyun, Guizhou, the paper discusses the missing time of a hiatus surface, an impor-tant problem in chemical sequence stratigraphy, with the concept of cosmic chemistry. Then thepaper proposes a series of new concepts for chemical sequence stratigraphy, including the con-densation surface, relative compaction factor and time missing factor. Finally a quantitativecurve of Late Permian relative sea-level change in the Ziyun area is presented with timecoordinates.展开更多
基金The NSFC-IIASA Major International Joint Research Project, No.41161140352 Natural Science Foundation of Chongqing, No.2010JJ0069 Science and Technology Great Special Project on Controlling and Fathering Water Pollution during the National 12th Five-year Plan, No.2012ZX07104-003
文摘Based on SPOT-5 images, 1：1 million topographic maps, the maps of the returning farmland to forest project and the Chongqing forest project, social and economic statistics, etc., this paper identifies the features and factors influencing farmland marginalization. The results showed： （1） During 2002-2012, the rate of farmland marginalization was 16.18%, which was mainly found in the high areas of northern Qiyao mountains and the medium-altitude areas of southern Qiyao mountains. And this farmland marginalization will increase, associated with non-agriculturalization of rural labourers and aging of the remaining labourers. （2） Elevation, distance radius from villages and road connections had a great in- fluence on farmland marginalization. Farmland marginalization rates showed an increasing trend with the increase of elevation, and 60.88% of the total farmland marginalization area is found at an altitude greater than 1000 m above sea level. The marginalization trend also increases with slope and distance from the distribution network. （3） Farmland area per labourer and the average age of farm labourers were major factors driving farmland marginalization. Farmland transfer and small agricultural machinery sets affect farmland marginalization with respect to management and productivity efficiency. （4） Farmland with ＂comparative-disadvantage-dominated marginalization＂ accounted for 55.32% of the total farmland marginalization area, followed by ＂location-dominated marginalization＂ （33.80%）. （5） According to the specifics of each real situation, different policies are suggested to mitigate the margin- alization. A ＂continuous marginalization＂ policy will encourage the return of farmland to forest in ＂terrain-dominated marginalization＂. An ＂anti-marginalization＂ policy is suggested to create new rural accommodation and improve the rural road system to counteract ＂terrain-dominated marginalization＂. And another ＂anti-marginalization＂ policy is planned to improve management and micro-mechanization for ＂comparative-disadvantage-dominated marginalization＂. A new idea was developed to integrate high resolution remote sensing and statistical data with survey information to identify land marginalization and its driving forces in mountainous areas.
文摘The analysis of company data useful for economic decisions,if not interpreted in an overall view of the company situation,can lead to wrong conclusions.This is the case when a company has to choose between several sales options for one or more products in the presence of a limiting factor.The continuation of the investigation often denies the initial analysis.Not everything is as it appears,therefore,at the beginning of the deepening of the data useful for economic decisions.As it is well known,the choices of profitability concerning the planning of the sale of company products take place,at least in the majority of cases,through the determination of the contribution margin,i.e.the profitability margin connected to the individual goods/services sold by the companies(selling price net of variable costs).The contribution margin can be determined with four objectives:(1)Determination of the yield of the single product,net of variable costs only.In this case,the margin defines unitary,from net product yield to unitary contribution margin.(2)Determination of the return on total sales of an individual product,net of variable costs.In this hypothesis,reference is made to the first level(or gross)contribution margin.(3)Determination of the ability of the individual product to contribute to the coverage of fixed costs common to the company.This margin is determined net of special product variable and fixed costs.This aggregate is defined as a Level II(or semi-gross)margin.(4)Determination of the useful value in the planning choices in case of presence of scarce productive factors.In this case,it must identify the so-called unitary margin for low factor.Here we will only deal with the problem of the use of the contribution margin in the presence of rare factors.To complete the analysis,below are some very brief considerations regarding,respectively,the unitary,level I,and level II contribution margin in order to better understand where the problem of the most convenient choice of income is located in the event of the presence of rare production factors,especially in an environment characterized by a plurality of sales options.
基金financially supported by the National Natural Science Foundation of China(No.40972091)
文摘According to the differences of structural deformation characteristics, the southern margin of the Junggar basin can be divided into two segments from east to west. Arcnate thrust-and-fold belts that protrude to the north are developed in the eastern segment. There are three rows of en echelon thrust-and-fold belts in the western segment. Thrust and fold structures of basement-involved styles are developed in the first row, and decollement fold structures are formed from the second row to the third row. In order to study the factors controlling the deformation of structures, sand-box experiments have been devised to simulate the evolution of plane and profile deformation. The planar simulation results indicate that the orthogonal compression coming from Bogeda Mountain and the oblique compression with an angle of 75° between the stress and the boundary originating from North Tianshan were responsible for the deformation differences between the eastern part and the western part. The Miquan-Uriimqi fault in the basement is the pre-existing condition for generating fragments from east to west. The profile simulation results show that the main factors controlling the deformation in the eastern part are related to the decollement of Jurassic coal beds alone, while those controlling the deformation in the western segment are related to both the Jurassic coal beds and the Eogene clay beds. The total amount of shortening from the Yaomoshan anticline to the Gumudi anticline in the eastern part is -19.57 km as estimated from the simulation results, and the shortening rate is about 36.46%; that from the Qingshuihe anticline to the Anjihai anticline in the western part is -22.01 km as estimated by the simulation results, with a shortening rate of about 32.48%. These estimated values obtained from the model results are very close to the values calculated by means of the balanced cross section.
文摘随着风电在电力系统中占比的逐年攀升,传统机组单独承担调频任务已难以适应其需求变化。因此,风电需具备与传统电源协同调节系统频率的能力。首先,基于风电调频的快速性和火电调频的持久性,设计了一种以火电为主、风电为辅的联合一次调频控制策略。其次,充分考虑风电场内各机组的运行差异,提出一种基于裕度因子的功率分配策略,有效挖掘各机组的调频能力并确保其安全运行。同时,提出一种针对风电场内风机分组运行的持久备用功率再分配策略。该策略预先安排少数风电机组以低减载率的超速模式运行,当调频风机退出频率支撑后,减载风机将根据调频风机的转速,采用一种基于转速反比例因子的差异化能量分配策略,以有效弥补调频风机退出后的能量缺额,缓解频率二次跌落(secondary frequency drop,SFD)。仿真结果表明,所提策略能够实现风火联合参与一次调频,在保证经济性和可靠性的前提下,充分发掘风电调频性能,有效改善电力系统频率响应特性。
文摘目的:分析机器人辅助根治性前列腺切除术(robot-assisted radical prostatectomy,RARP)后切缘阳性(positive surgical margin,PSM)的危险因素并建立预测模型。方法:回顾性分析2020年1月—2023年11月就诊于复旦大学附属肿瘤医院的420例行RARP的患者临床资料,根据术后PSM情况分为阳性组和阴性组。采用单因素及多因素logistic回归分析RARP后PSM的独立危险因素。根据影响因素分析结果,利用R语言软件绘制RARP后PSM的列线图,绘制受试者工作特征(receiver operating characteristic,ROC)曲线并计算曲线下面积(area under the curve,AUC)评估模型的区分度,并进行拟合优度检验。结果:多因素logistic回归分析显示,临床分期、PSA、术后病理Gleason评分、双侧前列腺浸润及PSA密度(PSAD)是RARP后发生PSM的危险因素(均P<0.05),将以上5个预测因素纳入模型构建,列线图预测模型的AUC为0.886(95%CI:0.838~0.934)。决策曲线阈值概率为0~30%及50%~60%时具有较高净收益,校正曲线与理想曲线基本相符,表明该模型具有良好的临床应用价值。结论:本研究建立了有效的RARP后PSM预测模型,对个性化预测具有一定的临床应用价值。
文摘胶莱盆地东北缘是胶东东部地区近年来发现的一个重要金成矿区,自1989年蓬家夼金矿(大型)发现以来,先后在牧牛山为中心的胶莱盆地东北缘发现了宋家沟(大型)、土堆-沙旺(大型)、辽上(特大型)等金矿床(点)(李国华等,2016),初步统计全区金资源量已超过223 t(Bo Junwei et al.,2024)。
文摘目的探讨吻合器痔上粘膜环切(procedure for prolapse and hemorrhoids,PPH)联合外痔切除术治疗混合痔后患者出现肛缘水肿、慢性疼痛的危险因素,为临床预防相关并发症提供指导建议。方法选取本院2020年1月至2022年12月采用吻合器手术切除治疗的混合痔患者300例进行临床研究,根据患者术后是否并发肛缘水肿、慢性疼痛将患者分别进行分组,对比各组患者的一般资料、手术情况及术后康复资料,分析引起肛缘水肿、慢性疼痛的危险因素。结果300例吻合器手术切除治疗的混合痔患者,其中发生肛缘水肿67例,未发生肛缘水肿233例,肛缘水肿患者的高血压占比、肥胖占比、便秘占比大于非水肿组,差异具有统计学意义(P<0.05);Logistic回归模型分析结果:合并肥胖、合并便秘、是发生肛缘水肿的独立危险因素(P<0.05)。300例吻合器痔切除手术切除的患者,其中发生慢性疼痛34例,未发生慢性疼痛266例,慢性疼痛组年龄≥65岁占比、糖尿病占比、肥胖占比、便秘占比的患者占比大于非慢性疼痛患者,差异具有统计学意义(P<0.05);Logistic回归模型结果显示:合并肥胖、合并便秘是发生慢性疼痛的独立危险因素(P<0.05)。结论肥胖、合并便秘会增大混合痔患者吻合器手术切除联合外痔切除术治疗后发生肛缘水肿的风险,合并肥胖、合并便秘会增大其发生慢性疼痛的风险。
基金This study was supported by the National Climbing Project "Sequence Stratigraphy and Sea-level Eustasy on the Margins of the Chinese Palaeocontinent"(No.8502208)and the China Postdoctoral Foundation.
文摘Taken as an example the Upper Permian reef section on the carbonate platformmargin at Ziyun, Guizhou, the paper discusses the missing time of a hiatus surface, an impor-tant problem in chemical sequence stratigraphy, with the concept of cosmic chemistry. Then thepaper proposes a series of new concepts for chemical sequence stratigraphy, including the con-densation surface, relative compaction factor and time missing factor. Finally a quantitativecurve of Late Permian relative sea-level change in the Ziyun area is presented with timecoordinates.
