Economic impacts of the Natural Forest Protection Program in Yunnan Province, China:an input-output analysis

The paper assesses the economic impacts of the natural forest protection program （NFPP） on the economy of Yunnan Province, China.in terms of gross output, value added,employment, and household income. An inputoutput model is developed to estimate NFPP＇s economic impacts by means of backward linkages in the forestry sector and logging and haudage sector. It is found than the NFPP has positive impacts on gross output, value added and houschold income in the initial year, but has significantly negative impacts on the regional economy in the following years as the investment decreases.

Life Cycle Input-Output Analysis Extended to Use, Disposal, and Recycling Stages Applied to Embodied CO2 Emissions of a Refrigerator

Input-output analysis is widely employed to analyze inventories of a product＇s embodied energy and environmental burdens. However, input-output analysis focuses only on the production stage and ignores other life cycle phases. Input-output analysis is not exactly a LCA （life cycle assessment） method in the strict sense of ISO 14040 standards, which must cover all stages of a product＇s life cycle, ＂from the cradle to the grave＂, so to speak. A tiered hybrid LCA is a useful tool that covers all life cycle stages by combining a process analysis with the input-output analysis method. This study aims to extend input-output analysis to the use, disposal, and recycling stages by using matrix-based method. The new method is applied to the analysis of the embodied CO2 emissions of a refrigerator as a case study. The entire life cycle C02 emissions are estimated to be 2.9 tons, including indirect emissions, and the reduction in CO2 emissions due to recycling steel scrap is calculated as 48.5 kg. The authors conclude that the new method enables a consistent inventory analysis for all life cycle stages by combining process and input-output methods.

A process-level hierarchical structural decomposition analysis (SDA) of energy consumption in an integrated steel plant

A hierarchical structural decomposition analysis(SDA) model has been developed based on process-level input-output(I-O) tables to analyze the drivers of energy consumption changes in an integrated steel plant during 2011-2013. By combining the principle of hierarchical decomposition into D&L method, a hierarchical decomposition model for multilevel SDA is obtained. The developed hierarchical IO-SDA model would provide consistent results and need less computation effort compared with the traditional SDA model. The decomposition results of the steel plant suggest that the technology improvement and reduced steel final demand are two major reasons for declined total energy consumption. The technical improvements of blast furnaces, basic oxygen furnaces, the power plant and the by-products utilization level have contributed mostly in reducing energy consumption. A major retrofit of ancillary process units and solving fuel substitution problem in the sinter plant and blast furnace are important for further energy saving. Besides the empirical results, this work also discussed that why and how hierarchical SDA can be applied in a process-level decomposition analysis of aggregated indicators.

Structural Decomposition Analysis on Energy Intensity Changes at Regional Level

As China's energy intensity fluctuated in recent years, it is necessary to examine whether this fluctuation happened at a regional level. This paper establishes a decomposition model by using the structural decomposition analysis (SDA) method at a regional level. Then this model is employed to empirically analyze the changes of Beijing's energy intensity. The conclusions are as follows: during 2002-2010, except petroleum, the energy intensity decreased and the changes were mostly attributed to the technology changes, while the final use variation actually increased the energy intensity; comparing different periods of 2002-2010, the decline rates of energy intensity for coal and hydropower were decreasing, resulting from the production technology being more energy-intensive than before; the energy intensity changes of petroleum firstly increased substantially and then decreased moderately.

By Sector Water Consumption and Related Economy Analysis Integrated Model and Its Application in Hai River Basin, China

This paper established a by sector water consumption and economy analysis integrated model with input–output analysis method. The model can be used to identify the relationships between economic activities and the direct water consumption, the total water consumption and the intersectoral water transaction for detailed sectors in regional economy. The method is applied to Hai River Basin in China that is characterized by water shortage. The results found that in Hai River Basin, agriculture sector is responsible for 81.2% of the direct total water consumption in the region, but industrial and service sectors account for 53.2% of the indirect total water consumption. To 24 industrial and service sectors, their ratios of indirect water consumption to total water consumption belong to [90%, 99%]. To per unit output, water consumption intensity was highest in agriculture sector 1 at 96.91 m3 per thousand Yuan, the value of 28 industrial and service sectors were smaller than 1. Products of sector 1, sector 24, sector 3, sector 12, sector 6, sector 11 and sector 10 are the main suppliers of indirect water.

Stability and reinforcement analysis of rock slope based on elasto-plastic finite element method

The rigid body limit equilibrium method(RBLEM) and finite element method(FEM) are two widely used approaches for rock slope's stability analysis currently. RBLEM introduced plethoric assumptions; while traditional FEM relied on artificial factors when determining factor of safety(FOS) and sliding surfaces. Based on the definition of structure instability that an elasto-plastic structure is not stable if it is unable to satisfy simultaneously equilibrium condition, kinematical admissibility and constitutive equations under given external loads, deformation reinforcement theory(DRT) is developed. With this theory, plastic complementary energy(PCE) can be used to evaluate the overall stability of rock slope, and the unbalanced force beyond the yield surface could be the identification of local failure. Compared with traditional slope stability analysis approaches, the PCE norm curve to strength reduced factor is introduced and the unbalanced force is applied to the determination of key sliding surfaces and required reinforcement. Typical and important issues in rock slope stability are tested in TFINE(a three-dimensional nonlinear finite element program), which is further applied to several representatives of high rock slope's stability evaluation and reinforcement engineering practice in southwest of China.

An Analysis of the Influence of Chinese Agriculture on National Economy and the Macroeconomic Effects

As a basic industry,agriculture has a far-reaching impact on national economy. Based on input-output tables of China in 2005 and2010,this paper gives a deep insight into the relationship between agriculture and national economy and its macroeconomic effects by the methods of input-output analysis,industrial correlation and macroeconomic effect analysis. The results show that the agricultural development is highly dependent on the national economy,but makes low contribution; agriculture contributes to promoting employment and improving the structure of national income distribution; despite the government's tax incentive,the agricultural equipments are updated slowly,and the corporate profits are at low level; agricultural export effect is far below the average industry level,but the import effect increases over the years,and final products are often used for domestic consumption. Finally,we set forth recommendations for improving the development of agriculture and national economy.

含DG的交直流不平衡配电系统暂态电压稳定性分析

分布式电源(DG)以及大量恒功率直流负荷接入交直流配电系统使得母线暂态电压表现出正负极耦合且多波动的特性,现有暂态电压稳定性评估方法准确率低且适用性较差。推导分析了双极交直流配电系统直流侧线路、负荷参数不平衡时影响系统母线暂态电压稳定的因素。基于二元表判据思想,提出一种改进的自适应母线暂态电压稳定性评估指标。针对参数不平衡时含DG的双极交直流配电系统,引入稳定性保持因子,提出母线与系统的暂态电压稳定裕度计算方法。基于所提方法利用MATLAB/Simulink仿真平台在改进的IEEE 33节点与IEEE 69节点双极交直流配电系统中量化影响系统暂态电压稳定性的因素,并对比验证了所提指标的有效性和优越性。

水轮发电机转子不圆度诱发的定子铁心振动特性研究

大型水轮发电机的转子不圆度问题使定子铁心受到低频磁吸力作用,磁吸力交变频率与定子铁心固有振动频率接近时,将诱发定子铁心的低频振动。针对转子不圆度所导致的气隙磁场不对称现象,首先推导了定子铁心上特定点受到的周期性磁吸力表达式,获得铁心振动频率与转子磁极不圆度之间的关联规律。随后以1台334 MV·A水轮发电机为例仿真了机组正常和单个磁极、连续磁极、间隔磁极以及椭圆磁极等典型不圆度状态下的电磁力分布,进一步利用瞬态结构分析得到了定子铁心的振动特性。最后在MJF-30-6故障模拟机组上模拟了磁极不圆度造成的磁场不对称现象,定子铁心振动理论分析和仿真结果吻合。

SOLVABILITY RESULTS OF A CONDITIONAL INPUT-OUTPUT EQUATION BASED ON A TYPE OF NONLINEAR LEONTIEF MODEL

A class of nonlinear and continuous type Leontief model and its corresponding conditional input-output equation are introduced, and two basic problems under the so called positive or negative boundary assumption are presented. By approaches of nonlinear analysis some solvability results of this equation and continuous perturbation properties of the relative solution sets are obtained, and some economic significance are illustrated by the remark.

基于不平衡数据的网络流量异常检测方法研究

为有效解决不平衡数据影响的问题,确保面对大规模网络流量数据异常检测的实时性,提出了基于不平衡数据的网络流量异常检测方法。通过优化SMOTE(合成少数类过采样)算法对含不平衡数据的网络流量数据进行平衡处理,将得到的数据集通过核主成分分析方法实现特征提取后,输入到卷积神经网络中。通过卷积和池化过程进一步实现网络流量数据深度特征提取,依据Softmax分类层对网络流量特征进行分类,利用训练好的卷积神经网络预测模型实现不平衡数据的网络流量异常检测。通过实验验证,该方法展现出了良好的效率和稳定性。在迭代次数为40次时,实现最佳不平衡数据处理结果,能够对异常数据进行精准识别。

SOME RESULTS ON CONTINUOUS TYPE CONDITIONAL INPUT-OUTPUT EQUATION-FIXED POINT AND SURJECTIVITY METHODS

Based on the classical(matrix type)input-output analysis,a type of nonlinear (continuous type) conditional Leontief model,input-output equation were introduced,as well as three corresponding questions,namely,solvability,continuity and surjectivity,and some fixed point and surjectivity methods in nonlinear analysis were used to deal with these questions. As a result,the main theorems are obtained,which provide some sufficient criterions to solve above questions described by the boundary properties of the enterprises consuming operator.

Comparison Between Modal Analysis and Impedance-based Methods for Analysing Stability of Unbalanced Microgrids with Grid-forming Electronic Power Converters

Stability in unbalanced power systems has deserved little attention in the literature.Given the importance of this scenario in distribution systems with distributed generation,this paper revisits modal analysis techniques for stability studies in power systems,and explains how to tackle unbalanced power systems with voltage-dependent loads.The procedure is described in detail and applied to a low-voltage(LV)simple case study with two grid-forming electronic power converters and unbalanced loads.Results are then compared with those obtained with the popular impedance-based method.While the latter is easier to implement using simulation or field data,the former requires complete information of the system,but gives a better insight into the problem.Since both methods are based on a small-signal approximation of the system,they provide similar results,but they discern different information.A larger second case study based on an LV CIGRE distribution system is also analysed.Results are obtained using a detailed Simulink model of the microgrids with electronic power converters.

Regional Agricultural Input-Output Model and Countermeasure for Production and Income Increase of Farmers in Southern Xinjiang,China

Agricultural input and output status in southern Xinjiang,China is introduced,such as lack of agricultural input,low level of agricultural modernization,excessive fertilizer use,serious damage of environment,shortage of water resources,tremendous pressure on ecological balance,insignificant economic and social benefits of agricultural production in southern Xinjiang,agriculture remaining a weak industry,agricultural economy as the economic subject of southern Xinjiang,and backward economic development of southern Xinjiang.Taking the Aksu area as an example,according to the input and output data in the years 2002-2007,input-output model about regional agriculture of the southern Xinjiang is established by principal component analysis.DPS software is used in the process of solving the model.Then,Eviews software is adopted to revise and test the model in order to analyze and evaluate the economic significance of the results obtained,and to make additional explanations of the relevant model.Since the agricultural economic output is seriously restricted in southern Xinjiang at present,the following countermeasures are put forward,such as adjusting the structure of agricultural land,improving the utilization ratio of land,increasing agricultural input,realizing agricultural modernization,rationally utilizing water resources,maintaining eco-environmental balance,enhancing the awareness of agricultural insurance,minimizing the risk and loss,taking the road of industrialization of characteristic agricultural products,and realizing the transfer of surplus labor force.

不平衡电网下电流源型PWM整流器改进型无差拍控制

三相电流源型PWM整流器运行在电网电压不平衡情况下,引起直流侧及网侧电流存在大量低次谐波,势必对后级变换器供电稳定性、安全性等存在不利影响。针对该问题,首先建立整流器数学模型,推导出不平衡电网下直流侧电压和网侧电流表达式,揭示出系统直流侧和网侧电流产生低次谐波的机理。其次,根据瞬时功率理论设计内环电流参考指令,并利用无差拍控制实现网侧电流对参考电流的跟踪。然而传统无差拍控制存在延时问题,将影响网侧电流的跟随性能,造成电能质量下降。为解决该问题,提出了网侧电流内环改进型无差拍控制,利用两步预测法补偿系统延时。最后,基于Matlab/Simulink平台搭建仿真模型,验证所提控制策略的正确性与有效性。结果表明,所提方法能有效抑制直流侧和网侧电流低次谐波,实现网侧电流正弦化和直流侧电压稳定输出。

基于中性线电流离散分析治理三相负荷不平衡

当三相负荷不平衡时,必然会引起中性线电流的产生。针对三种不同三相负荷不平衡条件下中性线电流的变化情况,建立与之对应的三相负荷不平衡度算法模型。采用中性线电流的离散分析建立三相负荷不平衡度算法,作为三相负荷不平衡治理的有效判据,结合试验分析,得到了三相负荷不平衡度与中性线电流的变化规律,并应用于低压供配电系统三相负荷不平衡的治理分析。结果表明:所提三相负荷不平衡度算法对低压供配电系统三相负荷不平衡的治理具有较强的实用性。提出的以三相负荷不平衡度为自适应变量,以中性线电流为过程监测量,采用有功调配与无功补偿相结合策略,能够有效反映三相负荷不平衡的治理情况。

破碎岩体隧道洞口开挖诱导滑坡与古滑坡耦合分析

以大栗树高速公路隧道洞口施工为工程背景,研究了在考虑古滑坡因素下洞口工作面边坡失稳及其加固技术。利用钻孔测斜数据(BCD)和Midas GTS折减强度有限元分析模型,分别推测了最危险滑动面,得知两者滑动面位置相似。并采用不平衡推力传递法,基于BCD推断滑动面计算安全系数。以BCD和有限元法的滑动面为基础,将滑动面近似假设为对数螺旋线,考虑地形因素,建立考虑多台阶边坡上限分析模型,研究了不同加固措施对边坡稳定的影响。结果表明,3种方法计算出的边坡安全系数结果相近。

基于非平衡MD&A文本数据的财务欺诈识别

财务欺诈不仅会导致会计信息失真,还会危害经济的健康发展。因此,找到一种高效的智能化欺诈识别方法具有重要的现实意义。本文基于2020—2022年美国上市公司提交到EDGAR数据库的年度报告,聚焦于报告中管理层讨论与分析部分的文本信息(Management Discussion and Analysis,MD&A)并对其进行分析。考虑到现有数据中欺诈和非欺诈样本数据极度不平衡的特点,本文在分层注意力网络的基础上设计了一个更高效的财务欺诈识别模型,最终使得欺诈识别模型的F1分数和F2分数分别提高了4.1%和3.7%,所提出的算法框架能够有效提高非平衡MD&A文本数据集的分类正确率。研究结果为财务欺诈识别系统性能的提高以及其他领域长文本分类任务的预测提供了新的解决思路,并进一步验证了使用MD&A文本数据进行财务欺诈识别的有效性,为使用非平衡数据进行欺诈识别提供了直接的实证支持。

电流源型PWM整流器改进预测滑模控制

针对三相电流源型整流器(Current source rectifier,CSR)拓扑提出了一种改进预测控制策略。首先,在CSR交流侧,对传统有限集模型预测控制进行了优化预测算法,减小了程序计算负担;其次,在CSR直流侧,采用滑模控制得到网侧有功功率参考值,提高了系统的动态性能。针对CSR交流侧LC滤波器容易产生谐振的问题,所提控制策略的代价函数增加了有源阻尼约束项;采用龙伯格状态观测器观测CSR交流侧电容电压,减少了传感器的使用。基于功率流的定量分析生成网侧电流参考,使得整流器能够在不平衡电网电压的情况下能实现恒定输出电流、网侧电流正弦化和高输入功率因数。最后,通过Matlab/Simulink仿真与样机试验验证了所提控制策略的正确性。

悬臂同轴双转子系统不平衡耦合振动抑制试验研究

针对悬臂同轴双转子系统不平衡耦合振动突出问题,以某开式转子发动机输出端双转子系统为研究对象,对悬臂双转子系统振动耦合机理进行了理论推导、仿真分析和试验研究。首先,采用有限元法(FEM)建立了双转子系统等效动力学模型和耦合动力学方程,分析了悬臂同轴双转子系统耦合振动机理;然后,利用有限元软件对双转子系统进行了模态分析、临界转速分析以及不平衡响应分析,建立了自敏感系数概念以定量评价系统对不平衡振动的敏感度和耦合状态;最后,根据实际结构设计了悬臂同轴双转子实验台,进行了不同转速比下的不平衡振动抑制实验,并结合实验结果对仿真结果进行了验证。研究结果表明:模拟仿真提出的自敏感系数可作为双转子系统实际振动测点布置和不平衡振动抑制策略的理论依据;通过应用先平衡内转子后平衡外转子的不平衡振动分步抑振策略,可使双转子系统不平衡振动降幅达80%以上。该研究对双转子系统传感器测点布局和系统耦合振动抑制具有一定的指导意义。