一种新的通用航空机载防撞逻辑设计方法

由于机载防撞系统(TCAS)是针对具有较大垂直高度变化率的大型飞机设计的,系统设定条件和与之相关的解脱建议并不能适用于通航飞机.针对通用航空的防撞问题,提出了一种基于马尔可夫决策过程(MDP)的防撞逻辑设计方法.首先,将飞机空中相遇过程的动态模型转换为离散转移函数;然后,基于防撞系统结果事件末端效用函数进行MDP建模,采用动态规划方法导出了最优防撞逻辑的迭代方程;最后,给出了通航飞机最优化防撞逻辑的设计流程并对最优防撞逻辑进行了计算机仿真.仿真结果表明,通过调整效用比参数可以在保证安全性能的同时有效降低系统告警率.在垂直相遇高度小于30 m的相遇过程占比高达18%的情况下,当告警率大于0.85时系统的碰撞概率仅为2.88×10-4左右.该设计方法对我国在低空空域通用飞机防撞系统的研究具有一定的参考价值.     

An experimental study on the effect of ad placement,product involvement and motives on Facebook ad avoidance

Facebook users do not visit the social networking site to see advertising. They are either just surfing the platform or searching for information. Therefore, advertising content is vulnerable to ad avoidance. In this study, the effect of two Facebook ad placements, sidebar ads and message stream ads, on ad avoidance intention was investigated through an online experiment. Sidebar placements are put next to the content stream, while message stream advertising is interwoven with the original Facebook content. 253 Respondents (M_age?=?39.4, SD?=?8.7, 50.2% female) were given either a searching or surfing task. The intention of respondents to avoid ads placed in the message stream was significantly higher than to avoid ads placed in the sidebar. Through multiple moderation analysis, we found that Facebook motivations and product involvement were significant moderators of the effect of ad placement on ad avoidance intent. Our results point to the crucial role of the degree of product involvement when targeting Facebook ads to the right audience and choosing the appropriate ad placement. We discussed implications for research and the professional field.     

Self-intersections and smoothness of general offset surfaces

A convex body N moves such that it touches a closed surface M. While doing this, it is undergoing a purely translational motion. A fixed point of N traces out the general offset surface during this motion. We study the connection between singularities and self-intersections of and the possible collisions of M with N during this motion and obtain some global results. Received 27 January 1999.     

Pattern-restricted permutations composed of 3-cycles

In this paper, we characterize and enumerate pattern-avoiding permutations composed of only 3-cycles. In particular, we answer the question for the six patterns of length 3. We find that the number of permutations composed of n 3-cycles that avoid the pattern 231 (equivalently 312) is given by $3^{n?1}$, while the generating function for the number of those that avoid the pattern 132 (equivalently 213) is given by a formula involving the generating functions for the well-known Motzkin numbers and Catalan numbers. The number of permutations composed of n 3-cycles that avoid the pattern 321 is characterized by a weighted sum involving statistics on Dyck paths of semilength n.     

The dynamics of a zooplankton–fish system in aquatic habitats

Diel vertical migration is a common movement pattern of zooplankton in marine and freshwater habitats. In this paper, we use a temporally periodic reaction–diffusion–advection system to describe the dynamics of zooplankton and fish in aquatic habitats. Zooplankton live in both the surface water and the deep water, while fish only live in the surface water. Zooplankton undertake diel vertical migration to avoid predation by fish during the day and to consume sufficient food in the surface water during the night. We establish the persistence theory for both species as well as the existence of a time-periodic positive solution to investigate how zooplankton manage to maintain a balance with their predators via vertical migration. Numerical simulations discover the effects of migration strategy, advection rates, domain boundary conditions, as well as spatially varying growth rates, on persistence of the system.     

OP-Fibo: An efficient Forbidden Pattern Free CAC design

Occurring crosstalk fault between wires is among the significant reliability challenges in transferring data between Processing Elements (PEs). Crosstalk fault occurs due to inter-wire coupling capacitances based on the appeared transition patterns on the channel. Among these transition patterns, Triplet Opposite Direction (TOD) causes the worst crosstalk effects on the transferred flits in the channels of NoCs. Forbidden Pattern Free Crosstalk Avoidance Codes (FPF-CACs) can efficiently omit TODs. However, state-of-the-art FPF-CAC has ambiguity in its mapping algorithm. This problem leads to generating more than one code word for some data words. To solve this problem, this paper aims to reduce crosstalk fault by proposing a FPF-CAC called Omissive Penultimate-Fibo (OP-Fibo). OP-Fibo benefits ambiguity-free numerical system and mapping algorithm that can generate unique code words for all of the data words and can save additional wires. Evaluations indicate that the proposed numerical system can be utilized in wires with any arbitrary channel width and also, can significantly improve the reliability with better overheads with respect to recently proposed FPF-CAC.     

On pattern avoiding flattened set partitions

Let Π = B_1/B_2/… /B_k be any set partition of[n]= {1,2,...,n} satisfying that entries are increasing in each block and blocks are arranged in increasing order of their first entries.Then Callan defined the flattened Π to be the permutation of[n]obtained by erasing the divers between its blocks,and Callan also enumerated the number of set partitions of[n]whose flattening avoids a single3-letter pattern.Mansour posed the question of counting set partitions of[n]whose flattening avoids a pattern of length 4.In this paper,we present the number of set partitions of[n]whose flattening avoids one of the patterns:1234,1243,1324,1342,1423,1432,3142 and 4132.     

Solution Bounds for Elliptic Partial Differential Equations via Feynman-Kac Representation

We transform suitable smooth functions into hard bounds for the solution to boundary value and obstacle problems for elliptic partial differential equations based on the probabilistic Feynman-Kac representation. Unlike standard approximate solutions, hard solution bounds are intended to limit the location of the solution, possibly to a large extent, and, thus, have the potential to be very useful information. Our approach requires two main steps. First, the violation of sufficient conditions is quantified for the test function to be a hard bounding function. After extracting those violation terms from the Feynman-Kac representation, it remains to deal with a boundary value problem with constant input data. Although the probabilistic Feynman-Kac representation is employed, the resulting numerical method is deterministic without the need for sophisticated probabilistic numerical methods, such as sample paths generation of reflected diffusion processes. Throughout this article, we provide numerical examples to illustrate the effectiveness of the proposed method.     

Pattern avoidance in “flattened” partitions

To flatten a set partition (with apologies to Mathematica^®) means to form a permutation by erasing the dividers between its blocks. Of course, the result depends on how the blocks are listed. For the usual listing—increasing entries in each block and blocks arranged in increasing order of their first entries—we count the partitions of [n] whose flattening avoids a single 3-letter pattern. Five counting sequences arise: a null sequence, the powers of 2, the Fibonacci numbers, the Catalan numbers, and the binomial transform of the Catalan numbers.