Exploring the tidal effect of urban business district with large-scale human mobility data

Business districts are urban areas that have various functions for gathering people, such as work, consumption, leisure and entertainment. Due to the dynamic nature of business activities, there exists significant tidal effect on the boundary and functionality of business districts. Indeed, effectively analyzing the tidal patterns of business districts can benefit the economic and social development of a city. However, with the implicit and complex nature of business district evolution, it is non-trivial for existing works to support the fine-grained and timely analysis on the tidal effect of business districts. To this end, we propose a data-driven and multi-dimensional framework for dynamic business district analysis. Specifically, we use the large-scale human trajectory data in urban areas to dynamically detect and forecast the boundary changes of business districts in different time periods. Then, we detect and forecast the functional changes in business districts. Experimental results on real-world trajectory data clearly demonstrate the effectiveness of our framework on detecting and predicting the boundary and functionality change of business districts. Moreover, the analysis on practical business districts shows that our method can discover meaningful patterns and provide interesting insights into the dynamics of business districts. For example, the major functions of business districts will significantly change in different time periods in a day and the rate and magnitude of boundaries varies with the functional distribution of business districts.     

Model-based robust control design and experimental validation of collaborative industrial robot system with uncertainty

Based on the traditional PID control and robust control algorithm, a novel practical robust control method is designed for the 6-DOF collaborative industrial robot with uncertainty. The proposed algorithm consists of a robust term and a model-based PD control term, which we call MPDP controller. It is demonstrated by Lyapunov theoretical analysis that the algorithm is able to guarantee uniform boundedness and uniform ultimate boundedness of the system. Simulations and experiments show the good performance of MPDP control in a robot with smaller steady-state tracking errors and better robustness compared to PID controllers.     

基于改进三角模糊VIKOR法的用户储能系统配置方案综合评估

针对不确定环境下用户储能系统配置方案评估决策,提出一种基于改进三角模糊多准则妥协解排序(VIKOR)法的评估模型。首先,运用扎根理论构建评估指标集,并采用灰色关联-粗糙集方法进行指标筛选,形成评估指标体系。然后,采用主、客观相结合的方法计算指标组合权重,以提高其准确性,其中主观权重由模糊层次分析(FAHP)法求得,客观赋权法由改进标准间重要性相关性(CRITIC)法求得。最后,考虑指标之间的冲突性与模糊性,运用改进三角模糊VIKOR法对配置方案评估与排序比选。通过仿真分析,验证了本文所建模型的有效性和可行性。     

面向鲁棒频谱感知的模糊K-means++算法

恶意用户通过向数据融合中心发送伪造的频谱感知数据,解决自身频谱资源短缺问题,但会极大地降低频谱感知系统的检测概率。为了解决此问题,提出了基于模糊K means++的数据融合算法。该算法首先引入模糊处理机制处理样本的数据特征值,以此来增加样本间的差异性;然后将模糊处理后的数据发送到融合中心,融合中心采用离群点挖掘的方法排除恶意用户,并对保留下来的用户进行融合,使样本向量具有鲁棒性;最后运用K means++算法对样本向量进行聚类。该算法利用轮盘法选择聚类中心,可有效抵御恶意用户的攻击,提高系统感知性能;无需知晓信号与噪声的分布等一些先验信息,也避免了繁杂的门限推导。从仿真结果可以看出,该算法对抵御恶意用户攻击具有突出的效果,有效提升了协同频谱感知系统的稳定性和鲁棒性。     

Predicting Mobile Cross-Platform Adaptation Using a Hybrid Sem–ANN Approach

Owing to constant changes in user needs, new technologies have been introduced to keep pace by building sustainable applications. Researchers and practitioners are keen to understand the factors that create an attractive user interface. Although the use of cross-platform applications and services is increasing, limited research has examined and evaluated cross-platforms for developing mobile applications for different operating systems. This study evaluates cross-platform features, identifying the main factors that help to create an attractive user adaptation when building sustainable applications for both Android and iOS. Flutter and React Native were selected so end-users could test their features using the cross-platform usability assessment model. Usability, satisfaction, and navigation were tested to measure the cross-platform adaptation and end-user experience. The data were analyzed using hybrid structural equation modeling (SEM) and artificial neural network (ANN) approaches. The study results show that usability and navigation both have a positive effect on adaptation on Flutter and React Native, while satisfaction only has an effect on Flutter. The navigation variable was also the most significant predictor of adaptation for both models. This study has several implications and makes contributions to the research field, to developers, and to end-users.     

融合用户信任度的概率矩阵分解群组推荐算法

利用推荐系统进行群组推荐时,群组成员之间的交互关系对推荐结果有很大影响,但传统的群组推荐算法较少考虑用户信任度的重要性,致使社交关系信息不能得到充分利用。在群组融合时考虑群组内用户间的交互关系,提出一种基于用户信任度和概率矩阵的群组推荐算法。在获取用户信任度数据后,使用概率矩阵分解（PMF）算法补全信任度矩阵并进行归一化处理,得到相似度矩阵,同时在后验概率计算过程中加入用户间的信任度因素,通过极大化后验概率获得预测评分。在此基础上,对群组中用户的权重进行归一化处理,使用基于用户交互关系的权重策略融合群组成员偏好,得到最终的推荐结果。在Epinions和FilmTrust数据集上的实验结果表明,该算法可使融合结果更具群组特性,同时提高推荐结果的可靠性和可解释性,且均方根误差和命中率均优于PMF、NeuMF、RippleNet等对比算法。     

杭州“智慧医疗”系统功能属性用户需求研究

目的确定杭州"智慧医疗"系统用户使用现状及各版块功能属性用户需求模型。方法在综合前期现状调研获取的杭州"智慧医疗"各版块用户行为现状及焦点小组和深入访谈发掘的用户各版块需求基础之上,编制KANO问卷对31家医院455名用户进行调查。结果 (1)用户对于智慧医疗的了解度和使用频率均不高;但使用意愿较强。(2)确立了各版块的KANO属性归类,其中属于线性属性(O)的有诊间结算的支付安全性,属于魅力型(A)的有分时预约的预约便捷性和时间精确性、诊间结算的便捷性、多功能自助机的便捷性和人工指导服务、智慧医疗App的使用便捷性和功能全面性、微信平台推送内容的便民性和及时性。结论 (1)用户对智慧医疗的总体了解度和使用频率均不高,但使用意愿较强,智慧医疗系统应基于用户需求进行优化并强化宣传推广。(2)各功能属性优先顺序如下:诊间结算的支付安全性、分时预约的预约便捷度、诊间结算的便捷度、分时预约的时间精确性、多功能自助机的人工指导服务、操作便捷度、智慧医疗APP功能全面性、使用便捷度、微信平台推送内容的便民度、推送内容及时性。     

Anticipating Cutoff Diameters in Deterministic Lateral Displacement (DLD) Microfluidic Devices for an Optimized Particle Separation

Deterministic lateral displacement (DLD) devices enable to separate nanometer to micrometer‐sized particles around a cutoff diameter, during their transport through a microfluidic channel with slanted rows of pillars. In order to design appropriate DLD geometries for specific separation sizes, robust models are required to anticipate the value of the cutoff diameter. So far, the proposed models result in a single cutoff diameter for a given DLD geometry. This paper shows that the cutoff diameter actually varies along the DLD channel, especially in narrow pillar arrays. Experimental and numerical results reveal that the variation of the cutoff diameter is induced by boundary effects at the channel side walls, called the wall effect. The wall effect generates unexpected particle trajectories that may compromise the separation efficiency. In order to anticipate the wall effect when designing DLD devices, a predictive model is proposed in this work and has been validated experimentally. In addition to the usual geometrical parameters, a new parameter, the number of pillars in the channel cross dimension, is considered in this model to investigate its influence on the particle trajectories.     

Probabilistic crack trajectory analysis by a dimension reduction method

This paper proposes a novel analysis method of stochastic crack trajectory based on a dimension reduction approach. The developed method allows efficiently estimating the statistical moments, probability density function and cumulative distribution function of the crack trajectory for cracked elastic structures considering the randomness of the loads, material properties and crack geometries. First, the traditional dimension reduction method is extended to calculate the first four moments of the crack trajectory, in which the responses are eigenvectors rather than scalars. Then the probability density function and cumulative distribution function of the crack trajectory can be obtained using the maximum entropy principle constrained by the calculated moments. Finally, the simulation of the crack propagation paths is realized by using the scaled boundary finite element method. The proposed method is well validated by four numerical examples performed on varied cracked structures. It is demonstrated that this method outperforms the Monte Carlo simulation in terms of computational efficiency, and in the meanwhile, it has an acceptable computational accuracy.     

User‐perceived Availability of a Software Rejuvenation Model with Recovery Time Omission

In this paper, the idea of omitting the recovery time when it is too short that it can be considered as negligible is incorporated in a software rejuvenation model. Two new models are introduced, in which the instantaneous availability is defined when firstly the rejuvenation time and secondly both rejuvenation and repair times can be omitted. The main purpose consists in regarding system software as operational when the time spent in a non‐operational state, like the rejuvenation and the failure states, does not exceed a predefined time threshold. By modeling the evolution of such a software rejuvenation model using continuous‐time Markov chains, we define its availability depending on whether the rejuvenation and the repair critical times are constant or random variables. Copyright © 2015 John Wiley & Sons, Ltd.