Incremental learning of Bayesian sensorimotor models: from low-level behaviours to large-scale structure of the environment

This paper concerns the incremental learning of hierarchies of representations of space in artificial or natural cognitive systems. We propose a mathematical formalism for defining space representations (Bayesian Maps) and modelling their interaction in hierarchies of representations (sensorimotor interaction operator).

We illustrate our formalism with a robotic experiment. Starting from a model based on the proximity to obstacles, we learn a new one related to the direction of the light source. It provides new behaviours, like phototaxis and photophobia. We then combine these two maps so as to identify parts of the environment where the way the two modalities interact is recognisable. This classification is a basis for learning a higher level of abstraction map that describes the large-scale structure of the environment.

In the final model, the perception–action cycle is modelled by a hierarchy of sensorimotor models of increasing time and space scales, which provide navigation strategies of increasing complexities.     

Protective ability of cerium-containing conversion films on aluminium

The options for electroless deposition of conversion films of lanthanum group metal oxides, in particular cerium, as an alternative to chromate conversion films (containing Cr⁶⁺) have been studied on aluminium. The main task of the study was to establish the influence of copper ions as a component of electrolytes for conversion treatment on the processes of formation and on the corrosion protective ability of cerium oxide films.

It has been ascertained that the electrochemical activation of the aluminium surface in the presence of Cu²⁺ in the electrolyte, leads to formation of oxide layers richer in cerium and possessing a better protective ability.

The presence of active cathodic sections of electroless, contact-deposited Cu has been shown to promote the corrosion activity of the system, due to the possibility of the appearance of micro-galvanic couples Al/Cu. A model experiment has been carried out to establish the inclination of the system to pitting corrosion. It has been shown that at the studied concentration of Cu²⁺ in the electrolyte the character of the corrosion does not change observably but there is a catalysing effect of the copper ions in the working electrolyte. The copper islands on the Al surface also have a catalysing effect, which is dominating in the processes of cerium oxide film formation. The chemical state and the composition of the conversion films have been defined by XPS measurements.     

Formation behaviours of blowhole and chill layer by GTAW in cast iron

Cast irons have some excellent characteristics in wear resistance, vibrational damping etc., and are widely used in many industrial machinery applications. But, the weldability has been much inferior originated from its high-carbon content. Several researches have reported that some of the important factors affecting the weldability were formation of blowhole and chill layer during fusion welding and subsequent rapid cooling.

In this study, the formation behaviours of those were investigated in both flake and nodular graphite cast irons. Tungsten inert gas arc welding was performed using several kinds of filler metal varied nickel and chromium content.

The study was made by paying attention to carbon behaviour and influence of nickel and chromium in filler metal on it.

Experimental results obtained were as follows.

1. The amount of blowhole increased with nickel content and decreased with chromium content.

2. On the other hand, the amount of chill layer increased with chromium content and decreased with nickel content.

3. It was estimated that both blowhole and chill layer formation were related to activity and diffusivity changes of carbon affected by nickel and chromium content. Then consequently they have a correlation relationship each other.

     

Connectionism,Processing, Memory

computing devices such as Turing machines resolve the dilemma between the necessary finitude of effective procedures and the potential infinity of a function's domain by distinguishing between a finite-state processing part, defined over finitely many representation types, and a memory sufficiently large to contain representation tokens for any of the function's arguments and values. Connectionist networks have been shown to be (at least) Turing-equivalent if provided with infinitely many nodes or infinite-precision activation values and weights. Physical computation, however, is necessarily finite.

The notion of a processing-memory system is introduced to discuss physical computing systems. Constitutive for a processing-memory system is that its causal structure supports the functional distinction between processing part and memory necessary for employing a type-token distinction for representations, which in turn allows for representations to be the objects of computational manipulation. Moreover, the processing part realized by such systems provides a criterion of identity for the function computed as well as helps to define competence and performance of a processing-memory system.

Networks, on the other hand, collapse the functional distinction between processing part and memory. Since preservation of this distinction is necessary for employing a type-token distinction for representation, connectionist information processing does not consist in the computational manipulation of representations. Moreover, since we no longer have a criterion of identity for the function processed other than the behaviour of the network itself, we are left without a competence-performance distinction for connectionist networks,     

Research at the Dr Sheelagh Campbell Laboratory at Teledyne-Impulse-PDM

Dr Sheelagh Campbell FIMF, Honorary Editor-in-Chief of Transactions (2002–2010) and Principal Lecturer at the University of Portsmouth, made important and varied contributions in the fields of chemistry and applied electrochemistry, in research, teaching and committee work, throughout her career.

Following the sad loss of Dr Campbell in 2010, readers and contributors to the journal will be delighted to hear about a research laboratory opened in her name at Teledyne-Impulse-PDM.     

Microstructure and properties of TiN/Ni composite coating prepared by plasma transferred arc scanning process

The TiN/Ni composite coatings were deposited on 7005 aluminium alloy by high speed jet electroplating and then processed with plasma transferred arc(PTA) scanning process. The microstructure, microhardness and friction coefficient of PTA scanning treated specimens were investigated. It is shown that the PTA scanning treated specimens have a rapidly solidified microstructure consisting of the uniformly distributed TiN phase and fine Al₃Ni₂ intermetallic phases. The composite coating has an average microhardness of approximately HV 800. The friction coefficient of PTA scanning treated specimens (oscillated at around 0.25) is considerably lower than that of TiN/Ni composite coating (oscillated at around 0.35). The corrosion behavior of the composite coating in 3.5% NaCl solution at room temperature was also determined using a potentiostat system. In comparison with the corrosion potential _corr of −0.753 V for 7005 aluminium alloy, the corrosion potentials for TiN/Ti composite coating and PTA scanning treated specimen are increased by 0.148 V and 0.305 V, respectively. The PTA scanning treated specimen has the lowest corrosion current densityJ_corr as well as the highest corrosion potential _corr, showing an improved corrosion resistance compared with 7005 aluminium alloy.     

三种不同体系的微生物腐蚀及控制

介绍了"水一金属"、"油(水)-金属"和"水-混凝土"三种易发生微生物腐蚀体系的相关腐蚀机理和控制方法,重点阐述了不同体系中硫酸盐还原菌(SRB)的腐蚀过程,并从环境介质的pH值、溶解氧含量、溶液中某些特定离子、生物膜以及微生物之间的相互作用等方面对微生物腐蚀的影响因素进行了论述,并介绍了不同体系微生物腐蚀的控制方法.     

土壤环境中管线钢硫酸盐还原菌腐蚀

腐蚀是世界各国共同面临的问题之一,每年因腐蚀造成的经济损失占全国GDP的3%~5%,其中土壤腐蚀约占总腐蚀的20%。金属的土壤腐蚀是一种自发的冶金逆过程,它不仅会导致埋地金属构筑物腐蚀破坏,还会引发管线泄漏、燃烧和爆炸等事故,给社会带来巨大的经济损失和社会危害。微生物腐蚀是埋地管线钢腐蚀的重要腐蚀类型之一,其中以硫酸盐还原菌引起的腐蚀最为严重。从环境因素、材料因素和微生物因素三个方面,对土壤环境中管线钢硫酸盐还原菌腐蚀进行了简要概述。埋地管线钢微生物腐蚀研究最多的是环境因素的影响,包括土壤类型、土壤含水量、土壤阴离子、化肥、农药、土壤宏电池和剥离涂层。材料因素的研究多集中在阴极保护、外加应力和杂散电流等因素的影响。相比前两种影响因素,微生物因素最为复杂,也是研究最少的一个方面。微生物因素的研究是一个全新的研究领域,包括膜内生物酶的影响以及膜内电子传递等。今后一段时间,埋地管线钢微生物腐蚀仍以环境和材料因素等多因素的耦合作用为主要研究方向。     

海洋环境下金属材料微生物腐蚀研究进展

海洋环境下的微生物易附着在金属材料表面形成生物膜,进而导致金属材料表面的微生物腐蚀(MIC)。分析了海洋环境下常见的易导致腐蚀的微生物种类及其特征,如硫酸盐还原菌(SRB)、铁氧化细菌(IOB)、产酸菌(APB)与产粘液菌(SPB)等,归纳了船舶与海洋平台涉及的微生物腐蚀及其与材料摩擦磨损的协同作用。在此基础上,重点综述了近年来碳钢、不锈钢与铜合金在海洋环境下的微生物腐蚀研究进展,包括溶解氧(DO)浓度、胞外聚合物(EPS)、生物膜微观形态等因素对碳钢MIC的影响,不锈钢在MIC过程中钝化膜与Cr元素化合物形态与含量变化,微生物抵抗Cu离子毒性机制以及铜合金在MIC过程中出现的脱合金成分腐蚀。对比了碳钢、不锈钢与铜合金表面在MIC中由生物膜、腐蚀产物与钝化膜形成的复合表面层结构差异。并从阴极去极化理论与微生物电化学腐蚀理论的角度解释了MIC,总结了两种理论间的关联性与局限性,指出了一些亟待解决的问题。     

Effect of nitrogen on crevice corrosion in austenitic stainless steel

Corrosion properties of high nitrogen austenitic steels in chloride solutions have been investigated. Nitrogen behavior was evaluated at various electrode potentials, and analysis of the surface film was carried out with XPS. The alloy used for the experiments had a composition of 23%Cr-4%Ni-0-1%Mo-0.7-1%N and was obtained through electro-slag remelting (ESR) under high nitrogen pressure. High nitrogen austenitic steel produced in the solution by crevice corrosion under a constant potential of 0.2 V (SCE). In the transpassive region and at 0.7 V (SCE), the products in the solution were , and . The amount of dissolved and increased with the electrode potential. in the solution suppressed decreases of pH, having a re-passivation effect. For crevice corrosion under a higher electrode potential than 0.4 V (SCE), the number of crevice corrosion points and the corrosion loss decreased as the electrode potential increased. This behavior can be attributed to the corrosion suppressing effect of dissolved in the solution as a product of crevice corrosion. The presence of chromium and iron oxides in the passivation film and crevice corrosion surface film were identified from XPS analysis. N 1s spectra indicated the presence of a nitride (CrN) or NH₃.     

Evaluation of a biocide effect upon microbiologically influenced corrosion of mild steel

The microbiologically influenced corrosion (MIC) is a very dangerous process, which affects the oil industry. The activity and microorganisms' growth at the pipelines steel cause surface modifications, which can induce a more complex corrosion process. The biocide evaluation for the MIC decrease has been normally based upon microbiological tests, and just a few references mention alternating methods which can be used as criteria for their evaluation. In this work, a commercial biocide was tested, using different electrochemical laboratory techniques, to determine its effect upon a biofilm generating bacteria consortium. Using microbiological techniques, the biocide lethal concentration was determined, and a concentration of 200 ppm was used to kill completely the consortium population in both, plancktonic and sessile parts. The electrochemical techniques: Polarisation Resistance (PR) and Electrochemical Impedance Spectroscopy (EIS), allowed describing the corrosion process associated to the microbial consortium and the biocide effect upon it.