Optimal Pattern Research Articles

(Invited) Micromolding of NiFe and Ni Thick Films for 3D Integration of MEMS

Electrodeposition process was studied in order to obtain uniformly thick magnetic films which could be incorporated in magnetic microsensors and actuators. Ni and NiFe patterns of different dimensions were deposited by micromolding on a Cu/Ti seed layer. In the case of NiFe deposit, a linear deposition rate was calculated by measuring the deposit thickness using mechanical profilometry. The optimum pattern composition for the fabrication of magnetic microdevices was 80 at. % of Ni, that was found by comparing the magnetic properties of the deposits obtained from different conditions. The deposits structure was also characterized. All the parameters were studied as a function of the current density so that by controlling the electrodeposition conditions the characteristics of the deposits could be controlled. NiFe films were integrated in multilayered magneto-impedance sensors. They present good adherence even after performing annealing at both 300°C and 500°C and sensor sensitivity reaches 10%/Oe.

Numerical study of the influences of different patterns of the building and green space on micro-scale outdoor thermal comfort and indoor natural ventilation

Citizens could enjoy a healthy and comfortable living environment if outdoor thermal comfort and sufficient natural ventilation are available in their dwellings. In this paper, numerical studies were performed with the Simulation Platform for Outdoor Thermal Environment (SPOTE) to investigate: (1) the thermal environment and pedestrian thermal comfort of the occupants in the open space with different patterns of the building and green space; (2) the wind pressures on the building facades and the natural ventilation rate of these buildings. The conclusions are summarized as follows: (1) it has been observed that the long facades of building and green space, which are parallel to the prevailing wind direction, can accelerate horizontal vortex airflow at the edges where such airflow could strengthen the convective exchange efficiency of hot air in low altitude and cold air in high altitude, and can obtain thermal comfort and sufficient natural ventilation at the pedestrian level; (2) after a series of simulations and comparisons, the configuration in which buildings are grouped in staggered layout with a centralized green space can provide better ventilation conditions and suitable air movement as a result of attenuated revised standard effective temperature (SET*). This configuration is regarded as the optimum pattern of the building and green space.

English

Twenty-eight isolates were isolated from samples of different sugarcane varieties infected with red rot during this survey; the culture was maintained on slants and Petri plates at 29±2°C. These isolates showed variability in their optimum radial growth pattern. These isolates were morphologically differentiated into two distinct groups: fifteen had light colour and thirteen had dark colour. Cultural characters of the isolates were divided into five groups viz. light sporulating, sparsely light sporulating, light non-sporulating, dark sporulating and dark non-sporulating. The length of the conidia varied from 25.1 to 30.5 µm and the width of the conidia varied from 4.2 to 5.5 µm; however, all the conidia were found to be falcate. The virulence of various isolates on the cane stalk showed a wide range of variation. However, all the light sporulating and dark sporulating isolates showed more or less similar virulence against a set of standard susceptible cane varieties. In this study, 28 isolates were tested based on fourteen pathological standards, in which six (Cf208, Cf608, Cf908, Cf1508, Cf2109 and Cf2609) were found to be most virulent. We have found that Colletotrichum falcatum isolates were culturally, morphologically and pathologically dissimilar and six new races are found reported in India.   Key words: Red rot, Colletotrichum falcatum, Saccharum officinarum, races, virulence.

Risk-based spatial zone determination problem for stage-based evacuation operations

This study seeks to determine risk-based evacuation subzones for stage-based evacuation operations in a region threatened/affected by a disaster so that information-based evacuation strategies can be implemented in real-time for the subzone currently with highest evacuation risk to achieve some system-level performance objectives. Labeled the evacuation risk zone (ERZ), this subzone encompasses the spatial locations containing the population with highest evacuation risk which is a measure based on whether the population at a location can be safely evacuated before the disaster impacts it. The ERZ for a stage is calculated based on the evolving disaster characteristics, traffic demand pattern, and network supply conditions over the region in real-time subject to the resource limitations (personnel, equipment, etc.) of the disaster response operators related to implementing the evacuation strategies. Thereby, the estimated time-dependent lead time to disaster impact at a location and the estimated time-dependent clearance time based on evolving traffic conditions are used to compute evacuation risk. This time-unit measure of evacuation risk enables the ERZ concept to be seamlessly applied to different types of disasters, providing a generalized framework for mass evacuation operations in relation to disaster characteristics. Numerical experiments conducted to analyze the performance of the ERZ-based paradigm highlight its benefits in terms of better adapting to the dynamics of disaster impact and ensuring a certain level of operational performance effectiveness benchmarked against the idealized system optimal traffic pattern for the evacuation operation, while efficiently utilizing available disaster response resources.

Mooring Pattern Optimization Using A Genetic Algorithm

In this paper, a constraint Genetic Algorithm is used for the purpose of mooring pattern optimization. The Genetic Algorithm is applied through a mathematical formulation which is introduced to define a typical mooring system optimization problem. The mathematical formulation is used in a case study on a spread moored crane barge, operating in the vicinity of a jacket type platform, in order to minimize its surge motions towards the platform. For this purpose, a set of criteria regarding clearances between anchors and seabed preinstalled facilities (pipelines), and also between the crane barge and the jacket platform are presented and considered. An automatic process of repetitive analyses implementing a MATLAB code as an interface between the Genetic Algorithm and a mooring system analysis program is used, and an optimum solution is resulted by performing 4000 quasi-dynamic analyses in time domain. The effectiveness of the Genetic Algorithm in leading to an optimum mooring system pattern is studied and it is shown that using a proper formulation of the problem, the Genetic Algorithm can be a very useful tool for finding an optimum pattern for mooring systems in fields with constraints on anchor locations and vessel motions.

Optimum Allocation of Agricultural Land to the Vegetable Crops under Uncertain Profits using Fuzzy Multiobjective Linear Programming

Decision making in agriculture had been embedded with a scientific planning for higher yields to cater the needs of overwhelming population and higher benefits for the prosperity of the farmers. The optimal cropping pattern that is allocation of land to various crops by making use of limited resources has become majorchallenge to fetch higher profits. Traditionally, farmers have relied on experience, intuition and comparisons with their neighbors to make decisions regarding cropping pattern. Basically,profit is a function of many factors which are sometimes beyond our control; hence intuitionand experience do not guarantee the optimal (maximum) profits. Many researches provided the optimum cropping patterns using Linear Programming (LP) technique in case of fixed prices (profits) of crops. But volatility in prices is very high for vegetable crops (cash crops) due to their expensive cultivation with high risk of profitability despite enhanced profits over food crops.Uncertainty in prices has countless impact on net returns ofcrops in agriculture. This paper aimed to provide a procedure for handling the volatility in profits of vegetable crops using Fuzzy Multi objective Linear Programming (FMOLP) along with step wise procedure to solve the model very easily using solver tool in MS-Excel. Numerical example cited in this paper is based on crisp profit coefficients and their chance of occurrence (probability) observedover period.

Optimum Back-pressure Forging Using Servo Die Cushion

This study focused on utilizing a servo die cushion (in conjunction with a servo press) as a “back-pressure load generator,” to determine its effect on shape accuracy of the formed part and total forming load in forward extrusion during cold forging. The effect of back-pressure load application was confirmed in experiments, and the optimum setting pattern of back-pressure load was considered to minimize both shape accuracy of the formed part and back-pressure energy, which was representative of forming energy using a sequential approximate optimization. The precise back-pressure load control by the servo die cushion enabled the ideal load-pattern setting for optimization to be achieved.

Day-to-Day Departure-Time Adjustment Process for CTM-Based Morning Commute Problem by Optimum Pattern

This paper is concerned with the day-to-day departure-time adjustment process for morning commute, which is expressed as a finite-dimensional discrete dynamical system. The total departure demand of morning commute is assigned to several time intervals. An optimum pattern is introduced to depict the process. In order to model the behavior of morning commute, the classic schedule delay concept and the cell transmission model are applied. A numerical example is given to illustrate the application of the day-to-day departure-time adjustment process by optimum pattern.

Micromolding of NiFe and Ni Thick Films for 3D Integration of MEMS

Electrodeposition process was studied in order to obtain uniformly thick magnetic films which could be incorporated in magnetic microsensors and actuators. Ni and NiFe patterns of different dimensions were deposited by micromolding on a Cu/Ti seed layer sputtered on SiO2/Si (for NiFe) and glass (for Ni). In the case of NiFe deposit, a linear deposition rate was calculated by measuring the deposit thickness using mechanical profilometry. The optimum pattern composition for the fabrication of magnetic microdevices was 80 at.% of Ni, that was found by comparing the magnetic properties of the deposits obtained from different conditions. The deposits structure was also characterized. All the parameters were studied as a function of the current density so that by controlling the electrodeposition conditions the characteristics of the deposits could be controlled. NiFe films were integrated in multilayered magneto-impedance sensors. They present good adherence of the layers even after performing annealing at both 300°C and 500°C and sensor sensitivity reaches 1%/Oe.

Nitrogen Foam Anti-Edge Water-Incursion Technology for Heavy Oil Reservoir with Edge Water

The steam stimulation is a main method to develop the heavy oil reservoir. However, the huff-puff wells will be water-flooded quickly if the reservoir has edge water, and the oil production level will decrease sharply. An experimental device, which can simulate edge water and steam stimulation process, was designed according to the feature of Henan heavy oil reservoir with edge water on the basis of steam flooding device, and the effect factors and application conditions of nitrogen foam anti-edge water-incursion technology were researched. The results show that the anti-edge water-incursion technology is suitable for the heavy oil reservoir with a medium energy edge water, and a better foam plugging will be got if the technology is applied at the time of serious water-flooded. The optimum injection pattern of the technology is a N2 slug first, followed by a nitrogen foam slug, and then the steam slug. Field tests were proceeded on the basis of experiment results and field experience, the operation success rate is 100%, the average drainage period reduces by 0.7d, the average cycle water cut reduces by 23%, the average cycle oil production increases by 2 times, and the average single-well oil-steam ratio increases by 0.25. So the technology can reduce water cut and increase oil production significantly, and the target of edge water inhibition is achieved.

Ground-dwelling spider (Araneae) and carabid beetle (Coleoptera: Carabidae) community assemblages in mixed and monoculture stands of oak (Quercus robur L./Quercus petraea (Matt.) Liebl.) and Scots pine (Pinus sylvestris L.)

A mixed tree species composition is frequently proposed as a way to increase habitat heterogeneity and support greater biodiversity in commercial forests. However, although international forest policy is increasingly advocating stands of mixed tree species, there is evidence to question the biodiversity benefits conferred by such forests. Using active ground-dwelling spiders and carabid beetles as biodiversity indicator taxa, we investigated the effect of forest stand composition on spider and carabid beetle community structure and composition. We conducted pitfall trapping in the summer of 2011 in 42 plantation forest stands across three different geographical regions in the UK and Ireland. Three common plantation forest stand types were examined: oak monocultures, Scots pine monocultures, and intimate Scots pine and oak mixtures (oak ⩽60% cover). Forest stand type had a weak effect on spider and beetle species richness, with no significant differences in mixed stands compared with monocultures. There were few differences in species composition between the stand types in each region and indicator species analysis found few species specifically affiliated with any of the forest stand types. Land use history is hypothesised to have contributed, at least in part, to the observed important regional differences in spider and beetle assemblages. Our results do not support the perception that intimate mixtures of dominant tree species benefit biodiversity in plantation forest stands. Further research is required to determine the optimum percentages and planting patterns required for mixtures of canopy tree species in order to support forest biodiversity.

Investigation of Light Extraction Efficiency and Internal Quantum Efficiency in High-Power Vertical Blue Light-Emitting Diode with 3.3 W Output Power

Light extraction efficiency (LEE) and internal quantum efficiency (IQE) of InGaN-based vertical blue light-emitting diode (LED) structures are investigated by numerical simulations and experiments. LEE of vertical LEDs is calculated for various structural and material parameters by using three-dimensional finite-difference time-domain (FDTD) simulations, and the optimum textured patterns on the n-GaN surface is found from the FDTD simulation. High-power vertical LED structures are fabricated based on the simulation results. The output power at 3 A injection current is measured to be 3.3 W, and the peak value of the external quantum efficiency (EQE) is found to be 64%. In addition, LEE of the fabricated vertical LED is expected to be 70–80% from the FDTD simulations. Combining the results of EQE and LEE, the peak IQE of the experimented vertical LED can be estimated to be 80–90%.

Enhanced Groove Geometry for Herringbone Grooved Journal Bearings

Although gas-lubricated herringbone grooved journal bearings (HGJB) are known for high rotordynamic stability thresholds, small clearance to diameter ratios are required for stable rotor operation. Tight clearances not only increase bearing losses but also yield challenging manufacturing and assembly tolerances, which ultimately translate into cost. Traditionally, the grooves of HGJB are of helical nature with constant cross section and pitch. The current paper aims at increasing the clearance to diameter ratio and the stability threshold of grooved bearings by introducing enhanced groove geometries. The axial evolution of groove width, depth, and local pitch are described by individual third order polynomials with four interpolation points. The expression for the smooth pressure distribution resulting from the narrow groove theory is modified to enable the calculation of bearing properties with modified groove patterns. The reduced order bearing model is coupled to a linear rigid body rotordynamic model for predicting the whirl speed map and the corresponding stability. By introducing a critical mass parameter as a measure for stability, a criterion for the instability onset is proposed. The optimum groove geometry is found by coupling the gas bearing supported rotor model with a multiobjective optimizer. By maximizing both the clearance to diameter ratio and the rotordynamic stability it is shown that with optimal groove geometry, which deviates from helicoids with constant pitch and cross section, the critical mass parameter can be improved by more than one order of magnitude compared to traditional HGJB geometries. The clearance to diameter ratio can be increased by up to 80% while keeping the same stability margin, thus reducing both losses and manufacturing constraints. The optimum groove pattern distributions (width ratio, angle, and depth) are summarized for a variety of L/D ratios and for different compressibility numbers in a first attempt to set up general design guidelines for enhanced gas-lubricated HGJB.

Optimization of modal load pattern for pushover analysis of building structures

Nonlinear Static Procedures (NSPs) have been developed as a practical tool to estimate the seismic demand of structures. Several researches have accomplished to minimize errors of NSPs, namely pushover procedures, in the Nonlinear Time History Analysis (NTHA), as the most exact method. The most important issue in a typical pushover procedure is the pattern and technique of loading which are extracted based on structural dynamic fundamentals. In this paper, the coefficients of modal force combination is focused involving a meta-heuristic optimization algorithm to find the optimum load pattern which results in a response with minimum amount of errors in comparison to the NTHA counterpart. Other parameters of the problem are based on the FEMA recommendations for pushover analysis of building structures. The proposed approach is implemented on a high-rise 20 storey concrete moment resisting frame under three earthquake records. In order to demonstrate the effectiveness and robustness of the studied procedure the results are presented beside other well-known pushover methods such as MPA and the FEMA procedures, and the results show the efficiency of the proposed load patterns.

Aggregate Production Planning Using Goals Programming(ENG)

This paper investigates Aggregate Production Planning (APP) model in a multi-plant producing multi-product to satisfy portion of fully deterministic demand in several cities for short term planning horizon. A Preemptive Goal Programming (PGP) approach is proposed with different scenarios to solve the APP model with conflicting multi-objective functions in order to maximize the total net profit with limited investment (budget), limited storage space, production capacity, and resources of the company. The proposed PGP model is also used to minimize the total production, inventory, transportation and defective items costs with optimum transportation pattern. A model is optimality solved and validated for a small numeric example of production planning problem with the results of optimal solutions for different scenarios obtained using optimization software LINGO package. Keywords: Aggregate production planning, Linear programming, Multi-objective criteria, Preemptive Goal Programming, Transportation .

Determining optimum flash patterns for emergency service vehicles: An experimental investigation using high definition film

An investigation of how emergency vehicle lighting (EVL) can be improved is reported with reference to an analysis of police vehicle road traffic accidents (Study 1). In Study 2, 37 regular drivers were shown film clips of a marked police vehicle, in which flash rate (1 Hz, 4 Hz) and pattern (single, triple pulse) were varied on the blue Light Emitting Diode (LED) roofbar. Results indicate a 4 Hz flash rate conveys greater urgency than a 1 Hz rate, while a 1 Hz, single flash combination was ranked the least urgent of all combinations. Participants claimed they would leave significantly more space before pulling out in front of an approaching police car (gap acceptance) in the 4 Hz single pulse condition in comparison to other EVL combinations. The preliminary implications for which flash characteristics could prove most optimal for emergency service use are discussed with regard to effects on driver perception and expected driving behaviour.

Optimization of hybrid LED package system for energy saving based on micro machining technology and taguchi method

A new concept, ‘hybrid LED package system (HLP system)’, is proposed as a simpler LED manufacturing process that unifies two steps of the process, the package step and the module step. Moreover, the HLP system can increase optical efficiency by virtue of its integrated optical pattern. A square pyramidal pattern was selected as the basic shape of the pattern of the HLP system. Four shape parameters of the HLP system were selected for optimizing the system. Nine cases of optical simulations organized according to the Taguchi method were performed using LightTools, and the optimum values of the parameters were determined by an SN ratio analysis. Using the optimum values, 28% higher illuminance and 32% higher luminance were predicted simultaneosly compared to the values without the integrated optical pattern. The optimum square pyramidal pattern was machined on a metal mold using an ultra-fine planer and a 90 degree angle diamond tool which would be used as a mold for manufacturing the optimized integrated optical pattern of the HLP system. The exact shape of the square pyramidal pattern with a height of 25 µm and a 90 degree angle was obtained. This study verified that the micro machined mold for manufacturing an optimized integrated optical pattern could be machined accurately, and finally the HLP system with the integrated optical pattern had higher uniform and brighter light distribution.

Optimum Directivity Patterns of Concentric Ring Arrays with Dipole Radiators for Wireless Communications

the literature survey concentric ring arrays using isotropic radiators are reported. Sufficient data is not available to optimization of the first sidelobe level, null to null beamwidth and directivity. In this paper, the author is proposed the problem of designing concentric ring arrays with practical radiating element. The practical radiating element is considered as dipoles to achieve optimum directional patterns for wireless communications. The numerically simulated patterns are computed and compared with the concentric isotropic ring arrays for different number of concentric rings. KeywordsRing Array, Concentric Dipole Ring Array,

Evaluation of applying axial variation of enrichment distribution method and radial variation of enrichment distribution in VVER/1000 reactor using a Hopfield neural network to optimize fuel management

In this present work the analysis technique was developed to find the optimum core configuration by applying neural network. This work investigates an appropriate way to solve the problem of optimizing fuel management in VVER/1000 reactor. To automate this procedure, a computer program has been developed.This program suggests an optimal core configuration which is determined to establish safety constraints. The suggested solution is based on the use of coupled programs, which one of them is the nuclear code, for making a database and modeling the core, and another one is Hopfield Neural Network Artificial (HNNA).The first stage of computational procedure consists of creating the cross section database and calculating neutronic parameters by using WIMSD4 and CITATION codes. The second one, consists of finding the optimum core loading pattern by applying the primary fuel assemblies of the VVER/1000 reactor core, using the HNNA method that based on minimizing power peaking factor (PPF) and maximizing the effective multiplication factor (keff). In the third second one, we apply a heuristic method to flat the flux core and decreasing the power peaking factor of the core. It consists of finding the best axial and radial variation of enrichment distribution to reach an optimum core loading pattern, by using HNNA and the cross section database.Finally, we compared obtained results of these methods to obtained results of the primary core, Suggested pattern of the Russian contractor.In total, the results show that applying the HNNA led us to the appropriate PPF and keff. Therefore, we achieved to a set of two basic parameters PPF and keff as effective factors on satisfying the safety constraints of VVER/1000 reactor core. It should be mentioned to say that the obtained results of HNNA suggested pattern is promising.Therefore, these methods ultimately eventuated to find the optimum configuration for VVER/1000 reactor core.

中国东部暖温带刺槐花期空间格局的模拟与预测

PDF HTML阅读 XML下载 导出引用 引用提醒 中国东部暖温带刺槐花期空间格局的模拟与预测 DOI: 10.5846/stxb201209281359 作者: 作者单位: 北京大学城市与环境学院,北京大学城市与环境学院,北京大学城市与环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(41071027,40871029);中国博士后科学基金项目(2012M520105) Simulation and prediction of spatial patterns of Robinia pseudoacacia flowering dates in eastern China’s warm temperate zone Author: Affiliation: Peking University,Peking University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:模拟刺槐开花日期与气温之间的空间关系,对于揭示蜜源植物物候空间格局形成的生态机制和掌握养蜂生产的时宜,具有重要的科学意义。利用中国东部暖温带26个站点1986-2005年的刺槐开花始期、盛期和末期数据,建立了基于日均温的多年平均和逐年物候空间模型,模拟多年平均和逐年刺槐开花日期的空间格局,并对模型进行了空间外推检验。进而,将1986-2005年8 km×8 km分辨率的日均温格点数据代入多年平均和逐年物候空间模型,得到连续地理空间多年平均和逐年刺槐开花日期的空间格局,并尝试设计了研究区内转地放蜂的适宜路线。结果表明:中国东部暖温带1986-2005年多年平均及逐年最佳期间日均温的空间格局分别控制着多年平均和逐年刺槐开花日期的空间格局。各地多年平均刺槐开花日期的空间序列与最佳期间日均温的空间序列呈显著负相关(P<0.001),多年平均气温-物候空间模型对刺槐开花始期、盛期和末期的方差解释量分别为87%、86% 和77%,模拟的均方根误差(RMSE)分别为2.5、2.7 d和4.1 d。同样,各地逐年刺槐开花日期的空间序列与最佳期间日均温的空间序列均呈显著负相关(P<0.05),逐年气温-物候空间模型对刺槐开花始期、盛期和末期的方差解释量分别介于44%-94%、57%-92%和39%-84%之间,模拟的平均RMSE分别为3.9、4.0 d和5.4 d。预测得到的连续地理空间多年平均刺槐开花日期呈现出自南向北、从平原向丘陵和山地逐渐推迟的空间演进特征。据此,中国东部暖温带地区转地放蜂可以沿西线、中线和东线进行,放蜂的大致持续时间可达40-50 d。此外,预测得到的连续地理空间1986-2005年期间刺槐开花始期、盛期和末期的线性趋势以提前为主,呈显著提前的面积分别占总面积的78%、26%和32%。 Abstract:Modeling spatial relationships between Robinia pseudoacacia flowering date and air temperature is crucial for revealing the ecological mechanism of spatial patterns of honey plant phenology and knowing well the right time of bee keeping production. Using Robinia pseudoacacia phenology data of beginning of flowering (BF), full flowering (FF) and end of flowering (EF) at 26 stations of eastern China's warm temperate zone during 1986 to 2005, we established daily mean temperature-based multi-year mean and yearly spatial phenology models to simulate multi-year mean and yearly spatial patterns of Robinia pseudoacacia flowering dates, and validated these models by extensive spatial extrapolation. Then, we substituted gridded daily mean temperature data with the spatial resolution of 8 km into the multi-year mean and yearly spatial phenology models, and obtained spatial patterns of multi-year and yearly Robinia pseudoacacia flowering dates over continuous geographic coverage during 1986 to 2005. Moreover, we attempted to project suitable routes of migratory beekeeping within the study area. The results show that spatial patterns of multi-year mean and yearly temperatures within the optimum length period control spatial patterns of multi-year mean and yearly Robinia pseudoacacia flowering dates, respectively in eastern China's warm temperate zone during 1986 to 2005. Spatial series of multi-year mean Robinia pseudoacacia flowering dates correlate negatively with spatial series of multi-year mean temperature within the optimum length period (P < 0.001) at the 26 stations. The multi-year mean spatial phenology models explained 87% of variance in BF date with a root mean square error (RMSE) of 2.5 days, 86% of variance in FF date with a RMSE of 2.7 days, and 77% of variance in EF date with a RMSE of 4.1 days. Similarly, spatial series of Robinia pseudoacacia flowering dates correlate negatively with spatial series of daily mean temperature within the optimum length period in each year (P < 0.05) at the 26 stations. The explained variances of yearly spatial phenology models to BF, FF and EF dates are between 44%-94%, 57%-92% and 39%-84%, respectively. The mean RMSEs of yearly simulation of BF, FF and EF dates are 3.9 days, 4.0 days and 5.4 days, respectively. The predicted multi-year mean Robinia pseudoacacia flowering dates over continuous geographic coverage show a delayed spatial progression from south to north, and from plains to hills and mountains. Therefore, migratory beekeeping can be implemented along with west, middle and east routes in eastern China's warm temperate zone with durations between 40 day and 50 days. In addition, the predicted linear trends in BF, FF and EF dates over continuous geographic coverage from 1986 to 2005 indicate a dominant advancement and the areas with significant advancement account for 78%, 26% and 32% of the total area, respectively. 参考文献 相似文献 引证文献