Three Basic Theorems in Numerical Analysis in Control Engineering Course and Their Application

International Journal of Control, Automation and Systems - Control system design packages like MATLAB, SICLAB, OCTAVE, etc. have become essential components of both undergraduate and graduate...     

An estimation of friction from the indentation of metals by acute-angled conical indenters

The paper describes a method for estimating the coefficient of friction (COF) between sliding surfaces by an indentation of an acute-angled indenter. The COF estimated by the method is compared with the COF measured by a friction tester. The conical indenter, which is made of WC and has an apex angle of 45°, is used for the experiments. A micro-Vickers hardness tester is used for the indentation tests. The friction tester used is one of Bowden–Leben type. A copper and a 0.45% carbon steel are used for the indentation and sliding specimens. The estimation of the COF is based on the equilibrium equation of indentation, which takes the friction between the contacting surfaces of the indenter and the specimen into consideration. The results show that the estimated COF is approximately equal to the measured one. Based on the results, the validity of this method is discussed.     

A superelastic nanocrystalline Cu-Sn alloy thin film processed by electroplating

A nanocrystalline Cu-Sn alloy film was processed by electroplating, and the indentation tests and microstructural observation were conducted on the electroplated Cu-Sn alloy film. The indentation tests at room temperature showed that a large amount of strain was recovered on unloading for the electroplated Cu-Sn alloy film, in contract, such a large reversible strain was not found in an electroplated pure Cu film. Thus, the electroplated Cu-Sn alloy film exhibited superelastic behavior. The grain size of the Cu-Sn alloy film was 99 nm. In spite of the very small grain size, the austenite start and finish temperatures of the Cu-Sn alloy film were relatively high. This is suggested to be related to the presence of the α-Cu phase.     

Evidence for enhanced thermal conduction through percolating structures in nanofluids

The unusually large enhancement of thermal conductivity (k/k(f)～4.0, where k and k(f) are the thermal conductivities of the nanofluid and the base fluid, respectively) observed in a nanofluid containing linear chain-like aggregates provides direct evidence for efficient transport of heat through percolating paths. The nanofluid used was a stable colloidal suspension of magnetite (Fe(3)O(4)) nanoparticles of average diameter 6.7?nm, coated with oleic acid and dispersed in kerosene. The maximum enhancement under magnetic field was about 48φ (where φ is the volume fraction). The maximum enhancement is observed when chain-like aggregates are uniformly dispersed without clumping. These results also suggest that nanofluids containing well-dispersed nanoparticles (without aggregates) do not exhibit significant enhancement of thermal conductivity. Our findings offer promising applications for developing a new generation of nanofluids with tunable thermal conductivity.     

Development of a method to lower recontamination after chemical decontamination by depositing Pt nano particles: (I) Consideration of the suppression mechanism using a quantum dynamics calculation

The Pt coating (Pt-C) process has been developed to lower the recontamination by radioactive elements after chemical decontamination of piping surfaces. In this process, a layer of fine Pt nano particles is formed in an aqueous solution on the base metal of the piping following the chemical decontamination. In this study, we confirmed that the suppression effect by the Pt-C toward ⁶⁰Co deposition on type 316 stainless steel using a ⁶⁰Co deposition test under hydrogen water chemistry. Furthermore, we investigated the suppression mechanism of deposition of radioactive elements by a quantum molecular simulation. The deposition amounts of ⁶⁰Co which were incorporated in oxides after 1000 h with and without the Pt-C process were about 90 and 10.2 Bq/cm², respectively. The amount of ⁶⁰Co deposition with Pt-C is about 10% that of non-coated specimens. The ⁶⁰Co incorporation for the Pt-C specimen was suppressed by decreasing the formation of oxides. We considered this phenomenon using a quantum dynamics calculation and concluded that the Fe–O bonds in oxides were weakened by the effect of Pt and hydrogen radicals which were produced in the reaction between H₂ and Pt, and then oxides were dissolved into the water.     

Comparison of carbonaceous aerosols in Tokyo before and after implementation of diesel exhaust restrictions

We compared the status of carbonaceous aerosols in Tokyo before and after the implementation of a diesel vehicle regulation intended to reduce the quantity of particulate carbon from diesel engines in one of the largest scale ever attempts at vehicle exhaust control. Radiocarbon (14C) in elemental carbon (EC) and total carbon (TC) were analyzed to identify fossil fuel carbonaceous particles emitted from diesel-powered vehicles. One-sided paired-month t-tests showed no distinct difference in the absolute concentrations of particles in terms of total mass (19.5 to 18.0 microg m(-3); p = 0.321), EC (3.6 to 3.3 microg m(-3); p = 0.272), and TC (6.3 to 6.2 microg m(-3); p = 0.418) for the finest particles (d(a) < 1.1 microm) after the implementation of the regulation. The ratios of the concentrations of the chemical constituents were, however, altered after the regulation. EC/TC was significantly decreased from 56.7% to 50.2% (p = 0.039). Although it was not statistically significant, the percentage of fossil carbon in EC also decreased (67.8% to 63.8%; p = 0.104). Since EC is predominantly of combustion origin, the observed decrease was likely due to the decrease in fossil EC emissions from diesel-powered vehicles. The decrease in EC/TC after the implementation of the regulation was also likely to have resulted from attachment to diesel vehicle exhaust systems of particulate filters as required as part of the regulation by the Tokyo Metropolitan Government. The EC/TC of fossil carbon of the finest particles decreased from 66.2% to 55.2% (p = 0.066), but EC/TC of biomass carbon did not decrease but rose slightly from 43.6% to 44.5% (p > 0.5). Thus, the relative ratios of components of carbonaceous aerosol particles, such as 14C, could provide a better understanding of the atmospheric pollution status, despite short-term fluctuations, than do measurements of absolute concentrations.     

Aqueous-phase synthesis of ultra-stable small CdSe nanoparticles

Very stable and small CdSe nanoparticles (NPs) were synthesized from the aqueous solutions containing L-cysteine (Cys) at room temperature. The Cys-capped CdSe NPs showed a very sharp excitonic peak at 420 nm. Its very small full width at half maximum (18 nm) indicates very high quality of the CdSe NPs. Their absorption features experienced little change over a month, implying an excellent stability of the CdSe NPs. The synthesis conditions were very critical to the optical property and stability of the CdSe NPs: only those prepared at specific conditions (n(Se-precursor)/n(Cd-precursor) = 0.25-0.5, n(Cys)/n(Cd-precursor) = approximately 9, pH = approximately 12) showed very sharp absorption peaks and maintained an excellent stability against time. Under these conditions, the peaks always appear at nearly the same wavelength, indicating that these NPs are selectively stable and grow at a particular size and structure.     

Curie Temperature Anomaly in Lead Zirconate Titanate/Silver Composites

The Curie temperatures of lead zirconate titanate-based (PZT-based) composites that were incorporated with silver particles were evaluated as a function of the silver content. Although the substitution of the silver ion has been considered to decrease the Curie temperature, PZT/silver composites exhibited higher Curie temperatures than those of monolithic PZT ceramics. It was found that the Curie temperature gradually increased as the silver content increased. It was suggested that the observed Curie temperature anomaly resulted from the relaxation of transformation-induced internal stress by intergranular silver particles.     

Development of incremental deep drawing process

This paper deals with development of an incremental deep drawing process. On a newly developed incremental deep drawing set-up, the aluminium sheets are formed; the forming is carried out by deep-drawing the blank as in the conventional method but incrementally. Fractures at the punch or die corner in the blank may or may not occur depending on the conditions; the process parameters involved are punch size, punch corner radius, increment in punch displacement, blank holding force or pressure, etc. It is thus shown that different shapes are formed by one set of common tools. It is thereby confirmed that incremental deep drawing is possible without using a particular tool set for a particular shape.     

A Study of Polymer Electrolyte Fuel Cells by the Measurement of AC Impedance,Current Interrupt,and Dew Points: 2. Effect of Cell Temperature

The effect of cell temperature on the performance of a polymer electrolyte fuel cell was examined in the present study. Measurements using the current interrupt and AC impedance methods showed that membrane resistance increased as the cell temperature was reduced. The charge transfer resistance, determined by the AC impedance method, also increased with decreasing cell temperature. The results of electrochemical analysis showed that the temperature of the cell strongly affected the performance of the membrane–electrode assembly in the cell. In addition, the water balance calculated from dew points of fuel gases changed with cell temperature. At a cell temperature of 80 °C, ca. 80% of the water generated on the cathode passed through the membrane to the anode, while at a cell temperature of 40 °C, only ca. 20% of the water on the cathode passed through the membrane to the anode.