Parameter design of event‐driven logic controller for two‐wheeled vehicle

Programmable Logic Controllers (PLCs) are widely used in industry. In PLC‐based control systems, low‐resolution (especially ON‐/OFF) sensors are inexpensive, and actuators are commonly used because they are compatible with programming languages used in PLCs. PLC switches the actuators ON/OFF as the state of the sensor changes between ON/OFF. In designing PLC‐based systems, the design of the parameters of these sensors and actuators (e.g., position of limit switches and torque of motors) is an important problem because they affect the overall performance of the system. This problem, however, has not yet been fully discussed. In the present paper, a systematic design method for this problem is developed. The main concept is to express the model of the system as a Mixed Logical Dynamical System (MLDS) and to formulate the problem as a mathematical programming problem. The developed idea is applied to the line‐following control of a two‐wheeled vehicle. The usefulness of the proposed method is demonstrated through simulation and experiments. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(2): 51–60, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20584     

Observation of internal pulsed current flow through the ZnO specimen in the spark plasma sintering method

In spark plasma sintering (SPS), it is supposed that a part of the large pulsed sintering current flows into the specimen and affects the sintering behavior. To clarify the influence of the internal pulsed current that flows through the specimen during SPS, measurement of the electrical resistance of the specimen was conducted using Pt electrodes and the internal pulsed current was successfully observed using a magnetic probe during the sintering of ZnO and other materials. Two Pt electrodes were installed on the sides of a ZnO sample through a carbon die, and decrease of electrical resistance was observed with the progress of sintering. The internal current that flows through the specimen during SPS was several hundred ampere, and the ratio of the internal current to the total current was found to be dependent on the material and the progress of SPS process.     

Growth of porous type anodic oxide films at micro-areas on aluminum exposed by laser irradiation

Aluminum covered with pore-sealed anodic oxide films was irradiated with a pulsed Nd-YAG laser to remove the oxide film at micro-areas. The specimen was re-anodized for long periods to examine the growth of porous anodic oxide films at the area where substrate had been exposed by measuring current variations and morphological changes in the oxide during the re-anodizing. The chemical dissolution resistance of the pore-sealed anodic oxide films in an oxalic acid solution was also examined by measuring time-variations in rest potentials during immersion.The resistance to chemical dissolution of the oxide film became higher with increasing pore-sealing time and showed higher values at lower solution temperatures. During potentiostatic re-anodizing at five 35-μm wide and 4-mm long lines for 72 h after the film was removed the measured current was found to increase linearly with time. Semicircular columnar-shaped porous type anodic oxide was found to form during the re-anodizing at the laser-irradiated area, and was found to grow radially, thus resulting in an increase in the diameter. After long re-anodizing, the central and top parts of the oxide protruded along the longitudinal direction of the laser-irradiated area. The volume expansion during re-anodizing resulted in the formation of cracks, parallel to the lines, in the oxide film formed during the first anodizing.     

Absorption of chlorine into still liquid in a simple stop-cock type absorber

Rates of absorption of chlorine from the downwardfacing surface into still liquids of various solutions, such as hydrochloric acid, sodium chloride solution, sodium hydroxide solutions, and pure water, were measured at 25°C. and 1 atm. in a simple stop-cock type absorber. It was found that the absorption rates followed Higbie's penetration theory for long contact times when the effects of free convection of the liquid near the gas-liquid interface were negligible. Using this type of absorber, results suggest that diffusivity of the gaseous solute in liquid can be conveniently measured with only a small amount of absorbent, and, in addition, that kinetic studies on moderately slow gas-liquid chemical reaction systems should be possible.     

Numerical analysis of the general characteristics of stereological bias in surface liberation assessment of ore particles

In mineral processing, ground ore particles containing valuable minerals are commonly separated from the gangue by flotation. For efficient flotation, surface liberation, in which the particle surface is composed of one phase, is important. Surface liberation is commonly measured by two-dimensional (2D) measurement of particle sections of resin-mounted samples. Such 2D measurement is considered to result in a form of error called stereological bias; however, the stereological bias associated with surface liberation assessment has not been fully studied. A series of numerical simulations was here conducted, to investigate the influence of a particle’s texture (the 3D internal particle structure) and shape on such stereological bias. First, a total of 110 patterns of texture (10 patterns of grain size times 11 levels of grain content) were modeled, to determine the general characteristics of the stereological bias. Then, the influence on the stereological bias, of particle shape as represented by the aspect ratio (an index of global shape) and corrected sphericity (an index of surface roughness), was investigated. The results revealed that texture had the largest, aspect ratio the second largest, and corrected sphericity the smallest influence on the stereological bias in surface liberation measurement. Based on the results, it is suggested that a rough estimate of the stereological bias in the measurement of irregularly shaped real ore particles can be made from much simpler numerical models of spherical particles.     

‘Model for a short-lived future’? Early tribulations of the Barbican redevelopment in the City of London, 1940–1982

This article recounts the chequered history of the Barbican redevelopment in the City of London, exploring its origins, planning, and implementation, together with its changing reputation. The Barbican is an interesting example of a modernist housing scheme, comprising multi-storey flats and social facilities set within a pedestrian precinct, something relatively unusual in the British context. The scheme was originally conceived in the 1950s as a publicly funded alternative to the rapid expansion of private office development and was pushed through in the 1960s by the City Corporation acting as its own developer. Subsequently, the whole project became mired in controversy and technical difficulties, and, as a result, on completion, few viewed it favourably. However, with urban regeneration again on the political agenda since the 1990s, the Barbican's image has improved, and it is increasingly recognized as one of the more notable achievements of British post-war modernism.