Pressure-sensitive molecular film for investigation of micro gas flows

For the development of micro- and nano-technology, it has been strongly desired to understand thermo-fluid phenomena inside or around micro- and nano-devices. An optical measurement technique based on the absorption and the emission of photons by molecules is useful for experimental analyses of thermo-fluid phenomena of micro and nanoflows. The pressure-sensitive paint (PSP) technique is a potential diagnostic tool for pressure measurements of micro/nano gas flows because it works as a so-called “molecular sensor”. However, the micro-scale measurement of PSP has been limited by the aggregation of the luminescent molecules and their thick film due to the use of a polymer binder. In our previous work, we adopted the Langmuir–Blodgett (LB) technique to fabricate pressure-sensitive molecular film (PSMF) with ordered molecular assemblies, and investigated properties of PSMF. In this study, a novel approach to enhance the luminescent intensity of PSMF is proposed, and the pressure distribution in a micro-nozzle is successfully measured by using PSMF. Moreover, we compared the pressure distribution measured by PSMF with that numerically analyzed by the direct simulation monte carlo (DSMC) method, showing good agreement with each other.     

Force sensorless robust tracking servo system suppressing periodic disturbance and sudden disturbance for optical disk system

This paper proposes a new force sensorless robust tracking servo system, which detects and suppresses both the periodic disturbance and the sudden disturbance without force sensor. The proposed system estimates both the periodic disturbance and the sudden disturbance and the sudden disturbance by using a new sudden disturbance observer and the memory of tracking error. In the proposed system, the influence of sudden disturbance is suppressed by the proposed sudden disturbance observer. On the other hand, the influence of periodic disturbance is suppressed by means of ZPET feed‐forward servo system. The experimental results point out that the proposed tracking servo system has a precise tracking response against both the periodic disturbance and the sudden disturbance. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 82–90, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20614     

Mobile robot navigation by a Distributed Vision System

This paper proposes aDistributed Vision System (DVS), which is an intelligent infrastructure for mobile robots consisting of manyvision agents (VAs) embedded in an environment. The system monitors the environment from various viewing points with the VAs, maintains the dynamic environment models, and provides various information to robots. Based on this concept, we have developed a prototype of the DVS which consists of sixteen vision agents and simultaneously navigates two robots in a model town.     

Influence of quadrature‐axis reactance of large turbine generator on operation

Two‐pole large generators are extensively used in power utilities. Growing demand for electric power in recent years has led to substantial increases in the capacity of generators. In line with this trend, our company has manufactured two‐pole turbine generators in the 900,000‐kVA to 1,200,000‐kVA classes. As the capacity of generators becomes larger, equivalent circuits are increasingly expected to improve their precision in estimating operation characteristics. The Park model has been widely used as an equivalent circuit model. The Park model with quadrature axis transient reactance $x_{q}^{\prime}$ is claimed to be useful for accurately estimating the load rejection characteristics of turbine generators. However, it is difficult to measure $x_{q}^{\prime}$, few studies based on measured data have appeared. As one of the few examples, we have conducted a measured data on a 500,000‐kVA‐class generator. Recently, the authors obtained test data on $x_{q}^{\prime}$ of a 900,000‐kVA‐class generator. In this study, based on these data, we studied the effect of $x_{q}^{\prime}$ using the finite element method and a transient analysis program (EMTP‐ATP). © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(3): 17–27, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21099     

Effects of coal blending on the reduction of PM10 during high-temperature combustion 2. A coalescence-fragmentation model

A coalescence-fragmentation model has been developed to predict the behaviors of coal mineral particles during the combustion of pulverized bituminous coals or coal blends. Based on the computer-controlled scanning electron microscope (CCSEM) characterization of coal minerals, the particle size distributions (PSDs) and mineral species of ash particles can be simulated. In particular, the interactions among excluded minerals (mainly referring to the excluded Ca-bearing-species and Fe-bearing-species) and included minerals are accounted for in this model. The PSDs and the mineral species of ash particles are derived from the coalescence and fragmentation of coal mineral particles. Based on this proposed model, both of the predicted PSDs and the mineral species of ash particles are in good agreement with their corresponding experimentally measured values. And the comparisons further demonstrate that the combined effects of coalescence of included minerals and fragmentation of excluded minerals have direct impacts on the ash-forming process. In addition, for the coals rich in excluded Ca- and/or Fe-bearing-species, the interactions among included minerals and excluded minerals are another important mechanism governing ash formation for high-rank coals.     

Stress intensity factors for interface cracks between orthotropic and monoclinic material

Different expressions are used in the literature for the stress intensity factors of interface cracks between anisotropic material. In particular, two of these approaches will be discussed and compared for orthotropic and monoclinic materials. Relations between the stress intensity factors will be found. Expressions for the interface energy release rate G_i{\mathcal{G}_i} are presented. Although the expressions appear different, they are shown to be the same by using the relations between the stress intensity factors. Phase angles are defined which may be used in a fracture criterion.     

Delay, noise, and resonance: human balancing and temporal non-locality

A rather peculiar phenomenon has been observed while a human was balancing a stick on a fingertip. The balancing time improved when the subject moved another object with the other hand. This was particularly so for many subjects with medium stick balancing skills. On the basis of this example, I consider how this seemingly simple task is composed of intricate mixtures of feedback delay, fluctuations, and predictions. I present some simple models of dynamics in which these factors lead to complex behaviors. From these examples, I infer that the concept of “nonlocality” could play an important role in characterizing biological and physiological systems.     

Ultrasonic-Assisted Soldering of 5056 Aluminum Alloy Using Quasi-Melting Zn-Sn Alloy

To obtain sound butt-joints of 5056 aluminum alloy rods, ultrasonic-assisted soldering was conducted using Zn-18Sn and Zn-60Sn alloys. Each solder foil was inserted between rods of 5056 aluminum alloy. Ultrasonic vibration was propagated to faying surfaces at soldering temperatures below the liquidus temperature of the solder alloys, and then the samples were air cooled to room temperature. The optimum vibration time at the soldering temperature must be more than 2 seconds to have complete wetting and less than 4 seconds to avoid excessive dissolution of the 5056 alloy. The 5056 alloy joints soldered using quasi-melting. Zn-Sn alloys showed greater strength than the joints soldered at the temperatures over its respective liquidus temperature. As the soldering temperature was increased, the increased formation of the intermetallic compound Mg₂Sn or phases containing Mg generated by dissolution of 5056 into the solder layer decreased the joint strength. Ultrasonic-assisted soldering at an optimum temperature between solidus and liquidus of the Zn-Sn alloys is an important consideration for producing sound joints with sufficient strength.     

奥多摩森林疗法之路

在日本,森林疗法的相关研究已近30年,在近些年的研究分析中,森林疗法的疗效已经得到科学证实。由此,日本社会引发了对人工林活用的重新审视。通过介绍位于日本东京都西多摩郡奥多摩町的奥多摩森林疗法之路的建设项目,深入浅出地分析了项目设计过程的整体思路以及思考重点。探讨了如何充分利用自然原始条件,创造可供人们康复治疗的人工林设...     

Theoretical models of mercury dissolution from dental amalgams in neutral and acidic flows

This article reports an experimental and theoretical investigation of mercury dissolution from dental amalgams immersed in neutral (noncorrosive) and acidic (corrosive) flows. Atomic absorption spectrophotometric measurements of Hg loss indicate that in neutral flow, surface oxide films formed in air prior to immersion persist and effectively suppress significant mercury release. In acidic (pH 1) flows, by contrast, oxide films are unstable and dissolve; depending on the amalgam’s material composition, particularly its copper content, two distinct mercury release mechanisms are initiated. In low copper amalgam, high initial mercury release rates are observed and appear to reflect preferential mercury dissolution from unstable Sn₈Hg (γ ₂) grains within the amalgam matrix. In high copper amalgam, mercury release rates are initially low, but increase with time. Microscopic examination suggests that this feature reflects corrosion of copper from grains of Cu₆Sn₅ (η′) and consequent exposure of Ag₂Hg₃ (γ ₁) grains; the latter serve as internal mercury release sites and become more numerous as corrosion proceeds. Three theoretical models are proposed in order to explain observed dissolution characteristics. Model I, applicable to high and low copper amalgams in neutral flow, assumes that mercury dissolution is mediated by solid diffusion within the amalgam, and that a thin oxide film persists on the amalgam’s surface and lumps diffusive in-film transport into an effective convective boundary condition. Model II, applicable to low copper amalgam in acidic flow, assumes that the amalgam’s external oxide film dissolves on a short time scale relative to the experimental observation period; it neglects corrosive suppression of mercury transport. Model III, applicable to high copper amalgam in acidic flow, assumes that internal mercury release sites are created by corrosion of copper in η′ grains and that corrosion proceeds via an oxidation-reduction reaction involving bound copper and diffusing hydrogen ions. The models appear to capture the correct time dependence of each dissolution mechanism and to provide reasonable fits to the experimental data.