相互作用模型在城市规划中的运用

城市增长是未来几个世纪备受关注的问题。为了保证城市可持续发展，有必要对城市的发展进行监控，但预测城市的发展趋势需要一些空间信息的支持、卫星图像能够提供可靠的信息用来评定城市增长的不同状态，而预测未来的建设区段则更加重要。本文构建了相互作用模型（interaction models），或者更精确地说叫潜力模型（potential model），以确定城市空间的扩展方向。该模型被运用于法国斯特拉斯堡地区的分析，采用了两张遥感数据影像，一张用于模型处理，一张用于检验结果。另外，模型还运用GIS技术以提高准确度，同时还考虑到了交通网络。     

Error matching detection and robust estimation adjustment approach for map conflation

The conflation of geographic datasets is one of the key technologies in the realm of spatial data capture and integration in geographic information system (GIS). Map conflation is a complex process of matching and merging spatial data. Due to various reasons such as errors in original data related to map data discrepancies, a great amount of uncertainties exists during the process and this will result in errors in featuring matching, especially point feature. Thus, it is vital to develop the method to detect the errors in feature matching and further the conflation results will not be affected. In this paper, error matching detection and robust estimation adjustment methods are proposed for map conflation. The characteristics of errors in feature matching are first analyzed, then a new approach for map conflation based on the least-squares adjustment is presented, and a robust estimation adjustment method is further proposed to detect and process matching errors. The results of the map conflation test show that the proposed method not only determines the errors in feature matching, but also obtains the optimal merging results in map conflation.     

OFDM系统峰平比问题的研究

OFDM技术最主要的缺点是具有较大的峰值平均功率比（PAPR）。本文就目前降低PAPR对OFDM系统影响的主要方法进行了简单的综述，一类是从OFDM信号着手；包括剪波法（限幅法），编码技术，相位旋转方法；另一类方法是对高频率放大器的实现线性化技术，主要是放大器预失真方法。     

Performance optimization of thermionic refrigerators based on van der Waals heterostructures

In this paper, an irreversible thermionic refrigerator model based on van der Waals heterostructure with various irreversibilities is established by utilizing combination of non-equilibrium thermodynamics and finite time thermodynamics. The basic performance characteristics of the refrigerator are obtained. The effects of key factors, such as bias voltages, Schottky barrier heights and heat leakages, on the performance are studied. Results show that cooling rates and coefficients of performances(COPs) can attain the double maximum with proper modulation of barrier heights and bias voltages. Increasing cross-plane thermal resistance as well as decreasing electrode-reservoir thermal resistance and reservoir-reservoir thermal resistance can enhance the performance of the device. The optimal performance region is the interval between the maximum cooling rate point and the maximum COP point. By modulating the bias voltage, the working state of the device can fall into the optimal performance region. The optimal performance of the refrigerator when using single layer graphene and a few layers graphene as electrode material is also compared.