超宽带盘锥天线的设计

介绍了盘锥天线的性能、设计原理,分析了各个参数对天线性能的影响。通过改变 天线结构,即在圆盘和下锥体之间引入一个上锥体,将盘锥天线和双锥天线结合起来,既保 持了盘锥天线的特性,又减少了圆盘和下锥体的分布电容,从而有效地增加了其带宽。在理 论计算的基础上利用ANSOFT HFSS软件对设计出的新型盘锥天线进行仿真优化,优化的结果 表明天线覆盖了从300 MHz到10 GHz的频带,在33∶1的带宽范围内驻波比基本小于 3,该方法有效地展宽了带宽。     

基于QualNet的战术数据链三维动态仿真

基于QualNet仿真软 件设计并实现了战术数据链在模拟环境下的三维动态仿真。将战术数据链仿真拓展到三维空 间,加入目标的机动性因素,给出了三维仿真的动态模型及其满足的更普遍关系式,具有一 定的参考价值和指导意义。     

基于地理加权和元胞自动机的建设用地发展模拟

为了防止建设用地的肆意扩张,缓解经济和生态平衡之间的矛盾,为政府部门的前期规划工作提供更合理的借鉴。为此以大连市某区域为研究区,将地理加权回归的思想融入到元胞自动机中,实现了城市空间发展的模拟,并与二次logistic回归模型作了对比。结果表明,在土地利用格局与影响因素建模过程中,存在着不同程度的空间自相关性,并在空间结构上不是单一趋势分布的,体现着空间不稳定性。将地理加权回归和元胞自动机的结合,不仅体现了空间分异特征,而且模拟精度也有所提高。     

Approaches to performance measurement in hedonic analysis: Price indexes for laptop computers in the 1990's

This paper estimates price indexes for laptop personal computers using hedonic methods and data taken from PC Magazine technical reviews. We use benchmark test results to construct a measure of system performance that encapsulates factors that have previously gone unmeasured, such as the interactions between hardware components. The resulting hedonic function is parsimonious yet has good explanatory power. A second approach to performance measurement is developed using a set of technical proxies that are shown to closely approximate the benchmark test scores, and are thus nearly perfectly equivalent in terms of resulting price index estimates. While not as parsimonious as a single performance measure, these proxies have the advantage of not requiring direct performance testing, and could thus be applied to larger data sets. Laptops were found to have declined in quality-adjusted price at an average rate of 40% per year for the period 1990-1998.     

Research on e-commerce transaction networks using multi-agent modelling and open application programming interface

We provide a formal definition of an e-commerce transaction network. Agent-based modelling is used to simulate e-commerce transaction networks. For real-world analysis, we studied the open application programming interfaces (APIs) from eBay and Taobao e-commerce websites and captured real transaction data. Pajek is used to visualise the agent relationships in the transaction network. We derived one-mode networks from the transaction network and analysed them using degree and betweenness centrality. Integrating multi-agent modelling, open APIs and social network analysis, we propose a new way to study large-scale e-commerce systems.     

MONOPOLISTIC LOCATION CHOICE IN A TWO‐SIDED HOTELLING MODEL

We analyse the optimal location choice of a monopolistic firm that operates two arbitrarily located platforms on a two‐sided market. By extending the traditional Hotelling framework, we show that the optimal platform locations are equivalent to the one‐sided benchmark if both sides are either restricted to single‐ or multi‐homing. In the mixed case (one side single‐homes, the other one multi‐homes), the optimal platform locations are in line with the respective symmetric case. If the monopolist is restricted to choosing the same location on either side of the market, the optimal locations are determined by the relative profitability of the market sides.     

Where to vacation? An agent-based approach to modelling tourist decision-making process

Agent-based models (ABMs) are becoming more relevant in social simulation due to the potential to model complex phenomena that emerge from individual interactions. In tourism research, complexity is a subject of growing interest and researchers start to analyse the tourism system as a complex phenomenon. However, there is little application of ABMs as a tool to explore and predict tourism patterns. The purpose of the paper is to develop an ABM that increases knowledge in tourism research by (i) considering the complexity of tourism phenomenon, (ii) providing tools to explore the complex relations between system components and (iii) giving insights on the functioning of the system and the tourist decision-making process. A theoretical ABM is developed to improve knowledge on tourist decision-making in the selection of a destination to vacation. Tourists’ behaviour, such as individual motivation, and social network influence in the vacation decision-making process are hereby discussed.     

Establishing the validity of cycle path capacity assumptions in the Highway Capacity Manual

Cycle mode share increase is widely desired, but highway design practitioners lack the numerical tools to deliver infrastructure, instead relying on design standards and intuition, with little literature basis. As a case in point, the US Highway Capacity Manual (which is well used internationally) has developed levels of service for cycle infrastructure that are, at their core, based on an assumption of noninteraction between multiple cyclists. This paper uses a modified implementation of the Social Force Model to test the validity of this assumption. Necessary changes such as the consideration of acceleration characteristics and minimum maintainable speed are included. The resulting model produces valid outcomes in keeping with established traffic flow properties, reflecting three-phase traffic flow theory and the ability for the stochastic elements in traffic flow to cause flow breakdown. The developed simulation indicates that there is a fundamental difference in outcome if cyclists are assumed to have a fixed speed versus one they can change given their surroundings. This difference in outcomes is found to exist within the range of literature design flow capacities for bicycle infrastructure and also yields emergent outcomes that align closely with those known behaviors of highway vehicles, which intuitively transfer to cyclists. These findings reinforce the standing need for large-scale empirical studies to determine the basic numerical and behavioral parameters for cyclists, upon which all design ultimately rests.     

Proteus仿真使用中的几个缺陷和应对办法

Proteus仿真软件,是当前EDA工具软件的优秀代表。但在使用过程中该软件存在一些缺陷。本文列举了该软件在模拟仿真中存在的几个缺陷以及我们采取的应对方法,供大家参考和讨论。     

Computer Simulation as a Tool for Planning and Management of Visitor Use in Protected Natural Areas

The United Nations Environment Programme’s Principles on Implementation of Sustainable Tourism suggest that implementing sustainable tourism must include monitoring visitor use of protected natural areas and directing it to areas where the environmental and social impacts of tourism are minimised. Thus, sustainable tourism management requires information about the spatial and temporal flow of visitor use in protected natural areas to help identify potential tourism-related threats to the natural and cultural resources of an area and the quality of visitors’ experiences. Recent research has identified at least four ways in which simulation modelling of visitor use can facilitate more informed planning and management of sustainable tourism in protected natural areas, including (1) describing existing visitor use flows; (2) monitoring the condition of ‘hard to measure’ indicator variables; (3) testing the effectiveness of alternative visitor use management practices; and (4) guiding the design of research on public attitudes. The purpose of this paper is to demonstrate, using findings from studies conducted in the Inyo National Forest and Isle Royale National Park, USA, each of these four potential contributions of computer simulation to sustainable tourism management and planning. The paper concludes with an assessment of the limitations of existing applications of computer simulation to nature-based tourism and recommendations for future research.