Results on memory-limited U-shaped learning

U-shaped learning is a learning behaviour in which the learner first learns a given target behaviour, then unlearns it and finally relearns it. Such a behaviour, observed by psychologists, for example, in the learning of past-tenses of English verbs, has been widely discussed among psychologists and cognitive scientists as a fundamental example of the non-monotonicity of learning. Previous theory literature has studied whether or not U-shaped learning, in the context of Gold’s formal model of learning languages from positive data, is necessary for learning some tasks.It is clear that human learning involves memory limitations. In the present paper we consider, then, the question of the necessity of U-shaped learning for some learning models featuring memory limitations. Our results show that the question of the necessity of U-shaped learning in this memory-limited setting depends on delicate tradeoffs between the learner’s ability to remember its own previous conjecture, to store some values in its long-term memory, to make queries about whether or not items occur in previously seen data and on the learner’s choice of hypotheses space.     

U-shaped, iterative, and iterative-with-counter learning

This paper solves an important problem left open in the literature by showing that U-shapes are unnecessary in iterative learning from positive data. A U-shape occurs when a learner first learns, then unlearns, and, finally, relearns, some target concept. Iterative learning is a Gold-style learning model in which each of a learner’s output conjectures depends only upon the learner’s most recent conjecture and input element. Previous results had shown, for example, that U-shapes are unnecessary for explanatory learning, but are necessary for behaviorally correct learning. Work on the aforementioned problem led to the consideration of an iterative-like learning model, in which each of a learner’s conjectures may, in addition, depend upon the number of elements so far presented to the learner. Learners in this new model are strictly more powerful than traditional iterative learners, yet not as powerful as full explanatory learners. Can any class of languages learnable in this new model be learned without U-shapes? For now, this problem is left open.     

U形波纹管疲劳寿命研究

疲劳寿命是U形波纹管的重要指标.利用传统公式和MSC Fatigue软件对波纹管的应力和寿命进行了计算.经试验验证和分析,认为利用MSC Fatigue软件进行疲劳寿命的方法是可行的,为波纹管的寿命分析提供了新的研究途径.     

Balancing of parallel U-shaped assembly lines

A new hybrid assembly line design, called parallel U-shaped assembly line system, is introduced and characterised along with numerical examples for the first time. Different from existing studies on U-shaped lines, we combine the advantages of two individual line configurations (namely parallel lines and U-shaped lines) and create an opportunity for assigning tasks to multi-line workstations located in between two adjacent U-shaped lines with the aim of maximising resource utilisation. Utilisation of crossover workstations, in which tasks from opposite areas of a same U-shaped line can be performed, is also one of the main advantages of the U-shaped lines. As in traditional U-shaped line configurations, the newly proposed line configuration also supports the utilisation of crossover workstations. An efficient heuristic algorithm is developed to find well-balanced solutions for the proposed line configurations. Test cases derived from existing studies and modified in accordance with the proposed system in this study are solved using the proposed heuristic algorithm. The comparison of results obtained when the lines are balanced independently and when the lines are balanced together (in parallel to each other) clearly indicates that the parallelisation of U-shaped lines helps decrease the need for workforce significantly.     

Variations on ray shooting

We solve some problems related toray shooting in the plane, such as finding the first object hit by a query ray or counting the number of objects intersected by the query line. Our main results are an algorithm for finding the first hit when the objects are lines, and an algorithm for the case when the objects are segments. If the segments form simple polygons, this information can be used for reducing the complexity of the algorithms. The algorithms are efficient in space and in query time. Moreover, they are simple and therefore of practical use.This research was partially supported by the NY Metropolitan Research Fund. The second author is currently at IBM Haifa Research Group, Haifa 32000, Israel.     

Variations on Lanczos' tridiagonalization process

Lanczos' tridiagonalization processes transform a matrix into an equivalent tridiagonal one. In this paper, we propose several ways of implementing these procedures. They are based on different choices of the auxiliary polynomials which appear in the underlying theory of formal orthogonal polynomials and on a change in their normalization. We also give transpose-free variants of Lanczos processes in the spirit of the CGS and BiCGStab algorithms for solving a system of linear equations. Numerical experiments show that some of the variants proposed have a better numerical behavior than the original algorithms. Received: August 1999 / Revised version: December 1999     

A bulk-micromachined bistable relay with U-shaped thermal actuators

This paper reports a deep-reactive ion etching (DRIE)-through-etched laterally bistable MEMS relay for power applications, with a primary emphasis on the design and modeling of its U-shaped transient thermal actuators, and a secondary emphasis on the design and fabrication of its contact element. In this relay, a contact crossbar is carried by a curved-beam bistable mechanism , which is toggled by transient U-shaped thermal actuators with their hot beam adiabaticly heated by electrical pulses. Each U-shaped thermal actuator comprises uniform-thickness hot and cold beams with a gap between them so they bend differently. This paper develops both a basic model and a complete model for the actuator that are verified by Finite Element Analysis and serve as effective design tools. The DRIE process creates nonideal etched surfaces, which pose challenges for good relay contacts. Both contact design and process development are discussed to help alleviate this problem. The fabricated relay exhibits a minimum total on-state resistance of 60 m/spl Omega/, and a maximum current carrying capacity of 3 A. It switches with a 1 ms actuation pulse, and a maximum 5 Hz repetition rate.     

Analytic Variations on the Airy Distribution

The Airy distribution (of the ``area' type) occurs as a limit distribution of cumulative parameters in a number of combinatorial structures, like path length in trees, area below walks, displacement in parking sequences, and it is also related to basic graph and polyomino enumeration. We obtain curious explicit evaluations for certain moments of the Airy distribution, including moments of orders -1 , -3 , -5 , etc., as well as +frac13 , -frac53 , -frac 11 3 , etc. and -frac73 , -frac 13 3 , -frac 19 3 , etc. Our proofs are based on integral transforms of the Laplace and Mellin type and they rely essentially on ``non-probabilistic' arguments like analytic continuation. A by-product of this approach is the existence of relations between moments of the Airy distribution, the asymptotic expansion of the Airy function Ai(z) at +∈fty , and power symmetric functions of the zeros -α _k of Ai(z) . Received June 6, 2000; revised February 17, 2001.     

Persian Variations

The concept of variation is essential in geometric design. It is surprising that patterns very different may be variations of the same model. We define two families of pentagonal patterns with three kind of variations, and give some suggestions how to analyse these patterns and create in this style. We then search for self-similarity systems in a strict sense. Although from a systematic search, the two solutions proposed here can also generate some traditional 2-level patterns. In searching for subdivisions of the tiles into rhombuses, we found two solutions. Both can be compatible with the Binary Tiling (not with the Penrose Tiling). Then, using the concept of X-Tiles defined in a previous paper (Castera et al., http://castera.net/entrelacs/public/articles/Flying_Patterns.pdf, 2011), we find new relationship between the two families of pentagonal patterns. In the last chapter we show and comment some examples taken from traditional architecture in Iran, and infer a self-similar system for pattern with interlaces from a 2-level tiling in Isfahan. This paper reflect the point of view of a pattern designer.     

Optimal allocation of heterogeneous workers in a U-shaped production line

In this paper, we deal with a U-shaped production line with multiple heterogeneous multi-function workers. Skills of workers are assumed to be different. We consider an optimization problem for finding an allocation of workers to the line that minimizes the overall cycle time under the minimum number of workers satisfying the demand. All of processing, operation and walking times are deterministic. We propose an algorithm for computing an optimal allocation of workers to machines.     

Variations on the Theme of Scarf's Counter-Example

We study the relation between the stability of a competitive equilibrium (CE)and the price adjustment mechanism used to attain that equilibrium point.Using two specific examples, a three-commodity exchange economy with a uniquecompetitive equilibrium (Scarf's global instability example) and atwo-commodity, two-trader type exchange economy with multiple competitiveequilibria, we show that the stability of a CE depends critically upon thedynamics of the price adjustment mechanism. A particular CE may be unstableunder one price adjustment mechanism but stable under another. The jointdynamics of the chosen price adjustment mechanism and the given economydetermines the overall stability of its competitive equilibrium. Our resultssuggest that context-rich studies of economic systems which focus on aspecific price adjustment mechanism may provide insights into the dynamics andstability of economic systems that are often not revealed through acontext-independent analysis.     

回报函数学习的学徒学习综述

通过研究基于回报函数学习的学徒学习的发展历史和目前的主要工作,概述了基于回报函数学习的学徒学习方法．分别在回报函数为线性和非线性条件下讨论,并且在线性条件下比较了2类方法——基于逆向增强学习（IRL）和最大化边际规划（MMP）的学徒学习．前者有较为快速的近似算法,但对于演示的最优性作了较强的假设;后者形式上更易于扩展,但计算量大．最后,提出了该领域现在还存在的问题和未来的研究方向,如把学徒学习应用于POMDP环境下,用PBVI等近似算法或者通过PCA等降维方法对数据进行学习特征的提取,从而减少高维度带来的大计算量问题．     

Stochastic analysis of a U-shaped production line with multiple workers

In a conveyor system for mass production as in the Ford system, each station processes just one item in one cycle time, where the cycle time is the time-interval between two successive outputs. In a Just-In-Time production system, a single-unit production and conveyance system is applied to a part production line without conveyors, and multi-function workers and a U-shaped layout of machines have been introduced. The multi-function worker takes charge of multiple machines. In this paper, we consider a U-shaped line with multiple multi-function workers, each of which is responsible for several machines. We formulate it into a marked Petri net, which has a convex property of a generalized semi-Markov process. This shows that the cycle times of two different systems are comparable in the sense of an increasing convex order. We also show the reversibility of the system, that is, the expected cycle time of the reversed system where each worker operates items and walks in the reversed order of stations is the same as that of the original system.     

超级分布学习对象的学习服务研究

以超级分布学习对（super distributed learning object,SDLO）的寻找伙伴服务为例,对SDLO的学习服务、学习服务的通信进行了描述,并给出学习服务算法,最后利用Aglet2．0．2开发出了SDLO原型系统,对SDLO的学习服务进行了验证。SDLO的学习服务是其分布性、协作性等特性的重要体现,为知识的交流、共享与创新提供了有力支持,从而达到分布式学习和协作学习的目的。     

基于核极限学习机的标记分布学习

标记分布学习作为一种新的学习范式,利用最大熵模型构造的专用化算法能够很好地解决某些标记多样性问题,但是计算量巨大。基于此,引入运行速度快、稳定性更高的核极限学习机模型,提出基于核极限学习机的标记分布学习算法（KELM-LDL）。首先在极限学习机算法中通过RBF核函数将特征映射到高维空间,然后对原标记空间建立KELM回归模型求得输出权值,最后通过模型计算预测未知样本的标记分布。与现有算法在各领域不同规模数据集的实验表明,实验结果均优于多个对比算法,统计假设检验进一步说明KELM-LDL算法的有效性和稳定性。     

Sliding-Mode Control Variations

The purpose of this paper is to present a framework in which high-order control variations are employed in sliding mode control to modify the sliding dynamics and/or reduce the dimension of the sliding surface. Control variations are implemented as sampled data feedback controllers with the variations generated during the sample intervals. This approach can greatly simplify nonlinear controller design and achieve asymptotic or practical stabilization for systems which fall outside the scope of the standard treatment of sliding mode control     

Computer support for learning mathematics: A learning environment based on recreational learning objects

In this paper, we introduce an electronic collaborative learning environment based on Interactive Instructors of Recreational Mathematics (IIRM), establishing an alternative approach for motivating students towards mathematics. The IIRM are educational software components, specializing in mathematical concepts, presented through recreational mathematics, conceived as interactive, recreation-oriented learning objects, integrated within the environment. We present the architecture of the learning environment which integrates communication services that support the interaction processes of the learning community, through instant messaging, chat rooms, and multi-player math games. Through the environment’s interface of their personal workspace, students have access to several easy-to-use mechanisms that allows them to customize its content, its layout, and its appearance. At internal levels, the functionality of IIRM is enhanced with features supported by the environment infrastructure. We evaluated different aspects of the learning environment in three short, motivation-oriented math courses given to Mexican high-school students. The results indicate that the use of the IIRM-based electronic learning environment, positively affects student attitudes towards mathematics. We believe that this approach has the potential to promote the mathematics learning process, basically on its motivational aspects.     

DCU-Net: a dual-channel U-shaped network for image splicing forgery detection

Neural Computing and Applications - The detection and location of image splicing forgery are a challenging task in the field of image forensics. It is to study whether an image contains a...     

A survey on deep learning and deep reinforcement learning in robotics with a tutorial on deep reinforcement learning

This article is about deep learning (DL) and deep reinforcement learning (DRL) works applied to robotics. Both tools have been shown to be successful in delivering data-driven solutions for robotics tasks, as well as providing a natural way to develop an end-to-end pipeline from the robot’s sensing to its actuation, passing through the generation of a policy to perform the given task. These frameworks have been proven to be able to deal with real-world complications such as noise in sensing, imprecise actuation, variability in the scenarios where the robot is being deployed, among others. Following that vein, and given the growing interest in DL and DRL, the present work starts by providing a brief tutorial on deep reinforcement learning, where the goal is to understand the main concepts and approaches followed in the field. Later, the article describes the main, recent, and most promising approaches of DL and DRL in robotics, with sufficient technical detail to understand the core of the works and to motivate interested readers to initiate their own research in the area. Then, to provide a comparative analysis, we present several taxonomies in which the references can be classified, according to high-level features, the task that the work addresses, the type of system, and the learning techniques used in the work. We conclude by presenting promising research directions in both DL and DRL.