Multi-objective model auto-calibration and reduced parameterization: Exploiting gradient-based optimization tool for a hydrologic model

Multi-objective model optimization methods have been extensively studied based on evolutionary algorithms, but less on gradient-based algorithms. This study demonstrates a framework for multi-objective model calibration/optimization using gradient-based optimization tools. Model-independent software Parameter ESTimation (PEST) was used to auto-calibrate ISWAT, a modified version of the distributed hydrologic model Soil and Water Assessment Tool (SWAT2005), in the Shenandoah River watershed. The time-series processor TSPROC was used to combine multiple objectives into the auto-calibration process. Two sets of roughness coefficients for main channels, one assigned and calibrated according on soil types and one determined via empirical equations, were examined for stream discharge simulation. Five different weighting alternatives were investigated for their effects on ISWAT calibrations. Results showed that using Manning's roughness coefficients obtained from empirical equations improves simulation results and calibration efficiency. Applying a two-step weighting alternative to different observation groups would provide the best calibration results.     

基于LDAP与Struts的数字校园门户统一身份申请系统

数字校园是推动教育信息化的重要系统工程,LDAP(Lightweight Directory Access Protocol)在数字校园门户统一身份认证中得到广泛应用.在讨论轻量级目录访问协议LDAP、Java Web开发技术的基础上,设计并实现了一个数字校园统一身份申请系统.该系统结合数字校园门户来进行邮件帐号和国际访问帐号的申请,具有较好的可移植性、可扩充性和安全性.     

实时监控数据图形展示与历史回放关键技术研究

管道腐蚀检测系统有利于工程师监测埋地管道腐蚀情况,节省管道维护开销。主要就管道腐蚀检测系统设计中有关实时监控数据图形展示与历史回放等关键问题的相关实现技术进行较深入研究,采用面向对象技术和特殊链表数据结构及算法。经系统实际运行,本方法不但有效解决系统设计中存在的若干问题,而且有效提高了系统开发效率、系统可维护性以及系统运行效率与质量。     

移动进程的蛰伏性及空间逻辑

界程逻辑(Ambient Logic)定义了一个示范性的空间逻辑来描述移动界程演算中移动进程的空间性质.然而在某些移动计算系统中,界程逻辑对移动进程空间性质的描述粒度是不够的.分析移动进程的蛰伏性质,用蛰伏和活跃来描述移动进程的存在状态,由此给出一种界程逻辑的扩展,称为状态空间逻辑.该逻辑能够描述移动进程的蛰伏性,进而更细粒度地刻画进程空间性质,且其在移动界程演算上的满足性是可判定的.同时还给出了状态空间逻辑公式的形式解释和蛰伏空间公式的逻辑推导规则.     

Accurately estimating reflectance parameters for color and gloss reproduction

A new method is described to estimate diffuse and specular reflectance parameters using spectral images, which overcomes the dynamic range limitation of imaging devices. After eliminating the influences of illumination and camera on spectral images, reflection values are initially assumed as diffuse-only reflection components, and subjected to the least squares method to estimate diffuse reflectance parameters at each wavelength on each single surface particle. Based on the dichromatic reflection model, specular reflection components are obtained, and then subjected to the least squares method to estimate specular reflectance parameters for gloss intensity and surface roughness. Experiments were carried out using both simulation data and measured spectral images. Our results demonstrate that this method is capable of estimating diffuse and specular reflectance parameters precisely for color and gloss reproduction, without requiring preprocesses such as image segmentation and synthesis of high dynamic range images.     

Using QuickBird imagery and a production efficiency model to improve crop yield estimation in the semi-arid hilly Loess Plateau,China

Crop yield is a key element in rural development and an indicator of national food security. A method that could estimate crop yield over large hilly areas would be highly desirable. Methods including high spatial resolution satellite imagery have the potential to achieve this objective. This paper describes a method of integrating QuickBird imagery with a production efficiency model (PEM) to estimate crop yield in Zhonglianchuan, a hilly area on Loess Plateau, China. In the PEM model, crop yield is a function of the photosynthetic active radiation (PAR), fraction of absorbed photosynthetically active radiation (f_APAR) and light-use efficiency (LUE). Based on the high spatial resolution QuickBird imagery, a land cover classification is used to attribute a class-specific LUE. The f_APAR is related to spectral vegetation indices (SVI), which can be derived from the satellite images. The LUE, f_APAR and incident PAR data were combined to estimate the crop yield. Farmer-reported crop yield data in 80 representative plots were used to validate the model output. The results indicated QuickBird imagery can improve the accuracy of predicted results relative to the Landsat TM image. The predicted yield approximated well with the data reported by the farmers (r² = 0.86; n = 80). The spatial distributions of crop yield derived here also offers valuable information to manage agricultural production and understand ecosystem functioning.     

纳他霉素结合ε-聚赖氨酸对火龙果贮藏品质的影响

目的 探究纳他霉素与ε-聚赖氨酸复配对火龙果贮藏品质的协同作用,为火龙果保鲜技术提供参考。方法 以红肉火龙果为材料,采用3个复配浓度(纳他霉素与ε-聚赖氨酸的复配比例为1∶1,质量浓度分别为400、800、1 200 mg/L,分别记作处理1、处理2、处理3)处理火龙果,于温度(25±2)℃、相对湿度(75±5)%下贮藏,对火龙果的感官指标、内容物和抗氧化酶活性的变化进行分析。结果 贮藏0~12 d,与对照组相比,3个处理组的质量损失率明显降低,降低幅度为45.50%~57.06%(P＜0.05);腐烂率明显降低,降低幅度为16.31%~38.30%;硬度和L^*的降低幅度分别为8.88%~21.02%、4.25%~6.24%;可溶性固形物(TSS)含量和呼吸强度的降低幅度分别为3.13%~11.79%、2.41%~46.76%。在贮藏10 d期间,丙二醛(MDA)含量显著降低(19.47%~33.98%);超氧化物歧化酶(SOD)、过氧化物酶(POD)活性分别显著增加了1.09%~27.59%、1.11%~32.77%。在贮藏8 d内,过氧化氢酶(CAT)活性增加了11.52%~36.19%;在贮藏12 d时,抗坏血酸过氧化氢酶(APX)活性显著提高了1.73%~23.98%。结论 3种处理均可延缓火龙果质量损失率和腐烂率的上升,减缓果皮L^*和硬度的下降速度,降低呼吸强度和MDA含量,提高SOD、CAT、POD、APX活性。其中,处理1(即400 mg/L ε-PL+400 mg/L Natamycin)更好地维持了火龙果的商业品质。     

基于本体的Web服务发现方法研究

针对传统Web服务发现准确率低下的问题,提出一种基于本体的服务发现方法.该方法首先基于领域本体构建了Web服务描述模型,并应用OWL-S描述Web服务增强了Web服务的语义信息,然后从基本信息语义相似度、功能语义相似度等方面综合计算Web服务相似度,最后基于Web服务相似度进行请求服务与目标服务的匹配.给出了基于本体的服务发现相关算法,并设计了基于三层架构的服务发现原型系统.实验结果表明,该方法可提高Web服务发现的查全率及查准率.     

基于数据挖掘技术的自适应入侵检测系统模型

为了提高数据库系统的安全,将改进的数据预处理算法和改进的Apriori算法应用于数据库入侵检测系统,提出一个基于数据挖掘技术的自适应的数据库入侵检测系统模型.模型中,针对滥用检测规则生成的局限性,提出将改进算法的中间结果运用到滥用检测规则的生成中,不断完善滥用检测规则库,结合滥用检测和异常检测的特点,先进行滥用检测,再进行异常检测,降低漏检率和误警率.检测结果表明,不断更新规则库,能够提高系统的自适应性.     

Modelling water dynamics with DNDC and DAISY in a soil of the North China Plain: A comparative study

The performance of the DNDC and Daisy model to simulate the water dynamics in a floodplain soil of the North China Plain was tested and compared. While the DNDC model uses a simple cascade approach, the Daisy model applies the physically based Richard's equation for simulating water movement in soil. For model testing a three years record of the soil water content from the Dong Bei Wang experimental station near Beijing was used. There, the effect of nitrogen fertilization, irrigation and straw removal on soil water and nitrogen dynamics was investigated in a three factorial field experiment applying a split-split-plot design with 4 replications. The dataset of one treatment was used for model testing and calibration. Two other independent datasets from further treatments were employed for validating the models. For both models, the simulation results were not satisfying using default parameters. After parameter optimisation and the use of site-specific van Genuchten parameters, however, the Daisy model performed well. But, for the DNDC model, parameter optimisation failed to improve the simulation result. Owing to the fact that many biological processes such as plant growth, nitrification or denitrification depend strongly on the soil water content, our findings bring us to the conclusion that the site-specific suitability of the DNDC model for simulating the soil water dynamics should be tested before further simulation of other processes.