双向搜索分层化的多约束路由启发式计算方法

提出一种多约束路由的双向搜索层次化计算方法,第一层分别从源和目的节点出发,计算到达各中间节点的可达路径,第二层在各可达路径中进行路径的筛选。可达路径是采用邻接矩阵变换方式获得的,筛选路径是根据非线性开销函数采用启发方式择优选取。当两方向搜索的节点数累计总和达到n-2后,则对接合并两方向到达中间节点的路径,获得多条经过不同中间节点的源到目的节点的路径,从中选择最佳路径作为路由输出。通过算例详细介绍了可达路径计算及启发式选优方法,论述了算法的正确性与合理性,分析了最坏时间杂性,简介了新算法具备并行运算特征。通过仿真实验评估,不仅更进一步验证了新算法的正确性,而且表明新算法在性能上要优于其他算法。     

Layered heuristic algorithm for multiple restriction routes

A layered algorithm by bidirectional searching is proposed in this paper to solve the problem that it is difficult and time consuming to reach an optimal solution of the route search with multiple parameter restrictions for good quality of service. Firstly, a set of reachable paths to each intermediate node from the source node and the sink node based on adjacent matrix transformation are calculated respectively. Then a temporal optimal path is selected by adopting the proposed heuristic method according to a non-linear cost function. When the total number of the accumulated nodes by bidirectional searching reaches n-2, the paths from two directions to an intermediate node should be combined and several paths via different nodes from the source node to the sink node can be obtained, then an optimal path in the whole set of paths can be taken as the output route. Some simulation examples are included to show the effectiveness and efficiency of the proposed method. In addition, the proposed algorithm can be implemented with parallel computation and thus, the new algorithm has better performance in time complexity than other algorithms. Mathematical analysis indicates that the maximum complexity in time, based on parallel computation, is the same as the polynomial complexity of O(kn2-3kn+k), and some simulation results are shown to support this analysis.     

EFP Warhead Missile Fuze Analysis and Simulation

The explosive formed penetrator (EFP) warhead missile projects the blast fragments in one direction normal to the missile longitudinal axis. Through analyzing on the two restrictions of EFP warhead explosion: trajectory restriction and attitude requirement, the concept of fuze time-delay tolerance is presented to be the measurement of the time of the EFP warhead explosion. The calculation models of fuze time-delay tolerance under two restrictions are provided. Some crucial parameters playing important roles in calculation under attitude requirements are simulated. The simulation results show that the engagement plane angle, roll rate and warhead attack standoff influence the tolerance dramatically.     

Fitting the experimental conditions and characteristics of Pt/C catalyst for the selective hydrogenation of citral

A Pt catalyst supported on activated carbon was prepared and pretreated at different conditions. Both experimental conditions and catalyst characteristics were optimized. The influence of the textural properties of the support on the catalytic performance, based on the study of the internal and external diffusional limitations, is presented. The Pt-dispersion and its localization along the porosity of the support, strongly influences the activity and the product distribution. The production of valuable unsaturated alcohols is favored using catalysts with a Pt-particle size of around 8?nm working at a high hydrogen pressure and moderate temperatures. Secondary reactions are favored by increasing the temperature and the presence of active particles inside the mesopores of the support.     

Beggar thy neighbour,beggar thy neighbourhood

Neighbourhood effects and the economies of housing consumption are, independently, thoroughly researched topics in the urban economics literature. Little has been said, however, about the effects of housing consumption restrictions on the dispersal of neighbourhood effects to different economic groups. At a time of rising public concern about economic inequality, properly understanding the link between housing market restrictions and neighbourhood effects across the income spectrum is of increasing importance. This paper proposes a model to better assess how labour productivity as influenced by neighbourhood effects changes with restrictions in housing consumption. The results of the model show that except in the case where no labour complementarity exists between the high and low‐skilled population segments, housing restrictions excluding the poor from the better‐off neighbourhoods will lead to welfare losses for both populations.     

Fine particulate matter measurements in Swiss restaurants,cafés and bars: What is the effect of spatial separation between smoking and non‐smoking areas?

Abstract  We performed 124 measurements of particulate matter (PM_2.5) in 95 hospitality venues such as restaurants, bars, cafés, and a disco, which had differing smoking regulations. We evaluated the impact of spatial separation between smoking and non-smoking areas on mean PM_2.5 concentration, taking relevant characteristics of the venue, such as the type of ventilation or the presence of additional PM_2.5 sources, into account. We differentiated five smoking environments: (i) completely smoke-free location, (ii) non-smoking room spatially separated from a smoking room, (iii) non-smoking area with a smoking area located in the same room, (iv) smoking area with a non-smoking area located in the same room, and (v) smoking location which could be either a room where smoking was allowed that was spatially separated from non-smoking room or a hospitality venue without smoking restriction. In these five groups, the geometric mean PM_2.5 levels were (i) 20.4, (ii) 43.9, (iii) 71.9, (iv) 110.4, and (v) 110.3 μg/m³, respectively. This study showed that even if non-smoking and smoking areas were spatially separated into two rooms, geometric mean PM_2.5 levels in non-smoking rooms were considerably higher than in completely smoke-free hospitality venues.  

Practical Implications

PM_2.5 levels are considerably increased in the non-smoking area if smoking is allowed anywhere in the same location. Even locating the smoking area in another room resulted in a more than doubling of the PM_2.5 levels in the non-smoking room compared with venues where smoking was not allowed at all. In practice, spatial separation of rooms where smoking is allowed does not prevent exposure to environmental tobacco smoke in nearby non-smoking areas.     

Supervised hours requirements in graduated driver licensing: Effectiveness and parental awareness

Most states require teens to complete a certain number of hours of supervised driving practice to obtain a license to drive unsupervised. Although widely implemented, the effect of requiring supervised practice is largely unknown. Using auto-regressive integrated moving average (ARIMA) interrupted time-series analysis, we found no change in fatal and injury crash involvement of 16–17-year-old drivers in Minnesota following enactment of a 30 h supervised driving requirement. To supplement and provide insight into these findings, we conducted telephone interviews with parents of newly licensed teenage drivers in five states with varying amounts of required supervised driving, including Minnesota. Interviews revealed awareness of supervised driving requirements was limited. Only a third of parents (32%) overall could correctly identify the number of hours their state required. In Minnesota only 15% of parents could identify the amount of supervised driving their teen was required to complete. Awareness of the number of hours required was substantially higher (55%) in Maryland. Unlike the other states, Maryland requires submission of a driving log detailing the hours of supervised driving. The findings suggest states need to develop more effective mechanisms to ensure parents are aware of supervised hours requirements.     

固-流结构矩形声子晶体中弹性波的传输特性

利用一维固-流结构矩形声子晶体中弹性波横向受限的条件,推导出弹性波在其中各个模式满足的关系式,利用它研究了弹性波各模式的特性。并利用色散法研究了弹性波的传输特性随模式量子数和矩形边长的变化规律。得出了一些不同于一维非受限声子晶体的新特征,即一维矩形声子晶体的禁带由模式量子数确定,禁带频率中心和频率宽度与模式量子数和边长有关。     

Short-term effects of a teenage driver cell phone restriction

On December 1, 2006, North Carolina began prohibiting use of any mobile communication device by drivers younger than 18. The current study examined the effects of the law on teenage drivers’ cell phone use. Teenage drivers were observed at high schools in North Carolina 1-2 months before and approximately 5 months after the law took effect. The proportion of teenagers using cell phones did not change significantly (11.0% before the law took effect, 11.8% after). Cell phone use among teenage drivers at high schools in South Carolina, an adjacent state without a teenage driver phone ban, was stable at about 13%. Interviews were conducted with parents and teenagers in North Carolina both before and after the law took effect. In post-law interviews, teenagers were more likely than parents to say they knew about the cell phone restriction (64% vs. 39%), but support for the ban was greater among parents (95% vs. 74%). Only 22% of teenagers and 13% of parents believed the law was being enforced fairly often or a lot. Although the proportion of teenagers who reported using phones while driving declined somewhat following the law, about half admitted they used their phones, if they had driven, on the day prior to the interview. Overall, the findings suggest that North Carolina's cell phone restriction had little to no effect on teenage drivers’ use of cell phones shortly after the law took effect.     

平板掺杂光子晶体中电磁波的缺陷模

为了研究1维平板掺杂光子晶体中电磁波的模式及其缺陷模特性,推导出1维平板掺杂光子晶体中电磁波的各个模式满足的条件,利用特征矩阵法计算出TE波和TM波各模式的缺陷模随模式量子数和平板厚度的变化规律,得出了一些不同于1维非受限掺杂光子晶体缺陷模的新特征。结果表明,电磁波的模式由模式量子数确定,缺陷模与模式量子数和平板厚度有关。