Process variation compensation technique for voltage‐controlled ring oscillator

A voltage‐controlled ring oscillator with process variation compensation circuits is designed using 0.25 µm CMOS technology. The simulation results show that the proposed ring oscillator increases the guaranteed frequency tuning range by 12% compared to a conventional ring oscillator. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Gas sensitiveness of polypyrrole films doped chemically in the gas phase

Electropolymerized polypyrrole films were electrochemically reduced and then chemically doped with one of PCl₃, SO₂, NO₂ or iodine vapour in the gas phase. These chemically-doped polypyrrole films showed a resistance decrease when they were exposed to electron-acceptor gases having electron affinities larger than those used in the chemical doping, except for one case of exposure of iodine-doped polypyrrole films to NO₂, where (although iodine has reportedly a larger electron affinity than NO₂) a resistance increase was seen, which was caused by a partial substitution of the doped iodine with exposed NO₂. The phenomenon is discussed in terms of the stabilization of gaseous species on adsorption. The present study suggests that a selective gas sensitivity may be attached to polypyrrole films if they are doped with an appropriate gas in advance.     

Human-sized anthropomorphic robot hand with detachable mechanism at the wrist

In this paper, we proposed a human-sized multi-fingered robot hand with detachable mechanism at the wrist. The fingers are tendon-driven by wires and the actuators are embedded in the arm part. The driving forces from the arm part are transmitted to the hand part by a gear mechanism at the wrist. The gear mechanism makes the hand part and the arm part splittable. The detachable mechanism enables separate maintenance of the hand and arm parts. To avoid undesired joint mutual interferences due to the tendon-driven mechanism, a joint motion correction control is implemented in that counteracting motions are ordered to actuators. The correction coefficient can be calculated based on the mechanical configuration. The developed robot hand has the size of 200[mm](length) × 78[mm](width) × 24.6[mm](thickness) and can exert 10[N] at the fingertip. The performance of the developed robot hand was shown by a motion control experiment.     

Perpendicular oriented cylinders via directional coalescence of spheres embedded in block copolymer films induced by solvent annealing

Polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer with PS volume fraction of 25.2 vol% was synthesized by atom transfer radical polymerization. Non-pretreated silicon wafers were used as the substrates to prepare perpendicular oriented PS cylinders in PMA matrix via solvent annealing which could induce the transformation of spheres to vertically oriented and hexagonally packed cylinders. The spherical microdomains were formed after the evaporation of solvents from the solutions of the block copolymer in selective solvents mixed from methanol, acetone and dichloromethane. The thickness of films could be as thick as 1000 nm, which were much thicker than usual cases and the cylinders came from the directional coalescence of the spheres, thus any pre-treatments of the substrates were not required for perpendicular orientation. The structures were characterized by small angle X-ray scattering (SAXS), transmission electron microscope (TEM), atom force microscopy (AFM) and grazing incidence small angle X-ray scattering (GISAXS).     

High-temperature tribological properties of spark-plasma-sintered Al2O3 composites containing barite-type structure sulfates

Al₂O₃–50BaSO₄–20Ag, Al₂O₃–50BaSO₄–10SiO₂, Al₂O₃–50(mass%)SrSO₄, Al₂O₃–50PbSO₄–5SiO₂, Al₂O₃–50BaSO₄ and Al₂O₃–50BaCrO₄ composites (mass%) were prepared by spark plasma sintering and their microstructure and high-temperature tribological properties were evaluated. Al₂O₃–50BaSO₄–20Ag composites (mass%) showed the lowest friction coefficients at the temperature ranging from 473 to 1073 K. Thin Ag film was observed on the wear tracks of the composites above 473 K. In addition, the friction coefficients of Al₂O₃ composites containing SrSO₄ and PbSO₄ were as low as those of Al₂O₃–BaSO₄ and Al₂O₃–BaCrO₄ composites at the temperatures up to 1073 K. The thin films formed on the wear tracks of the Al₂O₃–SrSO₄ composites were composed of Al₂O₃ and SrSO₄ phases, while the films formed on the wear tracks of the Al₂O₃–PbSO₄–SiO₂ composites consisted of Al₂O₃, PbSO₄ and SiO₂ phases.     

Micro cutting in the micro lathe turning system

As an application of cutting for the manufacture of micro mechanical parts and as a trial of the development of a miniature machining system matching the micro size of the work piece, a micro lathe turning system has been developed. A work material 0.3 mm in diameter is clamped and cut to a minimum of 10 μm in diameter with a rotation speed up to 15,000 rpm. The whole size of the equipment is about 200 mm which can be set under an optical microscope. A micro diamond single point tool has been applied to the cutting of various shapes, and the usefulness of such a micro cutting tool for the various forms has been confirmed. Cutting force has been investigated using a three directional force sensor and the possibility of the reduction of resistant force to improve working accuracy and to apply to micro parts has been examined.     

Identifying through-thickness material properties of carbon-fiber-reinforced plastics using the virtual fields method combined with moiré interferometry

An investigation into the use of a novel curved-beam composite specimen is conducted to measure the interlaminar (through-thickness) tensile properties of carbon-fiber-reinforced plastic. A combination of a numerical model and full-field displacement/strain measurement with moiré interferometry is utilized in this study. Through-thickness material properties are identified from the measured displacement distribution using the virtual fields method. Because of the shape and the loading condition of the proposed curved composite beam, both tensile and shear stresses exist in the through-the-thickness direction. Therefore, the interlaminar tensile modulus, as well as the interlaminar shear modulus, can be evaluated. The measurement results by moiré interferometry provide the material properties through inverse analysis.     

Time dependence of mesoscopic strain distribution for triaxial woven carbon-fiber-reinforced polymer under creep loading measured by digital image correlation

This paper presents the time dependence of the mesoscopic strain of a triaxial woven carbon-fiber-reinforced polymer under creep loading measured using digital image correlation (DIC). Two types of DIC techniques were employed for the measurement: conventional subset DIC and mesh DIC. Static tensile and creep tests were carried out, and the time dependence of the mesoscopic strain distribution was investigated by applying these techniques. The ultimate failure of this material is dominated by inter-bundle decohesion caused by relative rigid rotation and relating shear stress. Therefore, these were focused on in the present study. During the creep tests, the fiber directional strain, shear strain, and rotation were monitored using the DIC, and the mechanism for the increase in the specimen’s macro-strain over time was investigated based on the results obtained by the DIC measurement.     

Functionalized NIR‐II Semiconducting Polymer Nanoparticles for Single‐cell to Whole‐Organ Imaging of PSMA‐Positive Prostate Cancer

Development of molecular probes holds great promise for early diagnosis of aggressive prostate cancer. Here, 2‐[3‐(1,3‐dicarboxypropyl) ureido] pentanedioic acid (DUPA)‐conjugated ligand and bis‐isoindigo‐based polymer (BTII) are synthesized to formulate semiconducting polymer nanoparticles (BTII‐DUPA SPN) as a prostate‐specific membrane antigen (PSMA)‐targeted probe for prostate cancer imaging in the NIR‐II window. Insights into the interaction of the imaging probes with the biological targets from single cell to whole organ are obtained by transient absorption (TA) microscopy and photoacoustic (PA) tomography. At single‐cell level, TA microscopy reveals the targeting efficiency, kinetics, and specificity of BTII‐DUPA SPN to PSMA‐positive prostate cancer. At organ level, PA tomographic imaging of BTII‐DUPA SPN in the NIR‐II window demonstrates superior imaging depth and contrast. By intravenous administration, BTII‐DUPA SPN demonstrates selective accumulation and retention in the PSMA‐positive tumor, allowing noninvasive PA detection of PSMA overexpressing prostate tumors in vivo. The distribution of nanoparticles inside the tumor tissue is further analyzed through TA microscopy. These results collectively demonstrate BTII‐DUPA SPN as a promising probe for prostate cancer diagnosis by PA tomography.     

Study on crack propagation behavior in a quenched glass plate

Crack pattern transition and crack propagation behavior in a quenched glass plate are investigated. Theoretical analysis indicates that the distance between the crack tip and the cold front is closely related to the crack pattern transition. This theoretical result is examined experimentally using instantaneous phase-stepping photoelasticity. As expected theoretically, when the crack tip remains close enough to the cold front, crack propagation remains straight. When this distance reaches a given value, the crack oscillates. These experimental results are in good agreement with the theory of crack pattern transition. Therefore, present theoretical analysis is valid in predicting the instability of crack propagation. The crack tip stress field is also examined by the present experimental method. In particular, in the oscillating regime, the mode-I stress intensity factor frequently becomes larger than the fracture toughness, and the mode-II stress intensity factor has a nonzero value during propagation. For the former result, some reasons are discussed, but the cause of this problem is still unknown. However, the latter result can be explained by the theoretical analysis of an infinitesimal kinked edge crack just after crack initiation.