Poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate): Correlation between colloidal particles and thin films

We deal with correlation between sizes of colloidal particles and minimum thickness of spin-coated thin films of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) studied by a dynamic light scattering (DLS), a scanning transmission electron microscopy coupled with an energy dispersive X-ray spectroscopy (STEM-EDX), C₆₀-sputtering X-ray photoelectron spectroscopy (XPS), and an atomic force microscopy. Based on the various measurements, it was pointed out that, PEDOT/PSS colloidal dispersion contained majority of primary nanoparticles with mean diameter of 41 nm and 16 nm for BAYTRON P AG (denote P grade) or BAYTRON PH500 (denote PH grade) solutions, respectively, and small amount of clusters aggregated by the primary particles, based on the DLS measurement and STEM observation. On the other hand, PEDOT/PSS thin films with thickness of 44 nm and 16 nm were easily prepared by spin-coating on silicon wafers from the P and PH grade solutions, respectively. Results of STEM-EDX, DLS, and XPS measurements suggested that the PEDOT/PSS thin films consist of the randomly packed primary nanoparticle-“monolayer”.     

Compensation of performance degradation caused by fault based on GIMC structure: Application to a redundant sensor fault of flexible arm

In recent years, control system reliability has received much attention with an increase of situations where computer‐controlled systems such as robot control systems are used. In order to improve reliability, control systems need to have abilities to detect a fault (fault detection) and maintain the stability and the control performance (fault tolerance). This paper deals with the strain gauge sensor fault of a flexible arm robot. In order to achieve a fault‐tolerant control system, the effect of the fault is identified as dual Youla parameter by regarding the estimation error of the faulty sensor signal as the faulty plant output. Moreover, Youla parameter is designed so as to suppress the effect of dual Youla parameter. Youla parameter is implemented in GIMC (Generalized Internal Model Control) structure proposed by Zhou. Since GIMC structure includes a conditional feedback, it is suitable for achieving a fault‐tolerant control system. The effectiveness of the proposed fault‐tolerant control system is confirmed by experiments. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 48–58, 2009; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20830     

Direct design from input/output data of a fault‐tolerant control system based on GIMC structure

This paper deals with a method for the design of a fault‐tolerant control system based on the Generalized Internal Model Control (GIMC) structure, consisting of a standard outer loop feedback controller and an extra inner loop controller. The distinguishing feature of the GIMC structure is that controller design for performance and robustness may be performed separately. The outer loop controller is designed for nominal performance using some controller synthesis to meet the (nominal) control specification, while the inner loop controller is designed to make a trade‐off between robustness and performance. This feature is suitable for fault‐tolerant control. The outer loop controller is designed for the fault‐free case, and the inner loop controller for the fault‐time case. In the conventional methods, the inner loop controller is designed to maximize the robust stability margin without fault information. Therefore, the performance in the fault‐time case tends to become conservative. In this paper, the inner loop controller is directly designed from experimental data collected from the faulty system. Since the collected data contains information on the fault, conservativeness in the conventional methods is decreased. The inner loop controller is designed by Virtual Reference Feedback Timing (VRFT). VRFT is a method of direct design from input‐output data without identifying any models. Since the complexity of the controller can be specified by the designer, no complexity reduction is necessarily required, which is advantageous in implementation. The effectiveness of the proposed design method is confirmed by an experiment. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(4): 53–62, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20929     

Effect of Mixed Grain Sizes on the Thermoelectric Propertiesof Ca0.9Yb0.1MnO3

Ca_0.9Yb_0.1MnO₃ has been identified as a material that might be suitable for thermoelectric applications. We fabricated micro/nanograined Ca_0.9Yb_0.1MnO₃ composites, with the aim of controlling the passage of electrons and phonons simultaneously. Micro/nanograined Ca_0.9Yb_0.1MnO₃ composites containing various fractions of nanosized powder were prepared by sintering mixtures of microparticulate and nanoparticulate Ca_0.9Yb_0.1MnO₃, obtained by solid-state reaction and by gas-phase reaction, respectively. The electrical resistivity increased markedly when the weight fraction of nanosized powder exceeded 50%, probably as a result of a percolation phenomenon. However, the thermal conductivity was considerably reduced when the weight fraction of nanosized powder exceeded 25%, but then remained almost constant. The absolute values of the Seebeck coefficient of micro/nanograined Ca_0.9Yb_0.1MnO₃ composites were larger than those of monolithic micro- or nanograin Ca_0.9Yb_0.1MnO₃, probably as a result of the effects of potential-barrier scattering. The highest dimensionless figure of merit ZT value of 0.09 at 973 K was achieved with a sample containing 50% nanosized powder, and this value is 10% larger than that of monolithic micrograined Ca_0.9Yb_0.1MnO₃.     

Large distance flow-slide at Jono-Oge due to the 2018 Sulawesi Earthquake,Indonesia

There was a shallow earthquake in the Central Sulawesi province of Sulawesi island of Indonesia with a moment magnitude (Mw) 7.5 on 28th September 2018 at 18:02:44 local time. The event was preceded by major foreshocks and followed by aftershocks of significant magnitude. The epicenter of the main shock was in the Donggala regency of Minahasa peninsula of Central Sulawesi, approximately 70 km from the provincial capital of Palu. The earthquake was caused by the tectonic movement of the left lateral Palu- Koro fault within the Molucca Sea microplate, triggering major geotechnical failure and structural damage in Palu city and Sigi regency. Thousands of people died or are still unaccounted for, and countless others were injured. Balaroa, Petobo, Jono-Oge and Sibalaya were the worst hit mainly due to large-scale flow-slides and mud flows. It was the first time that such large-scale flow failures were triggered by an earthquake, and that the failure of very gentle sloping ground swept away whole localities. The objective of this research was to provide insight into the scale of ground failure and other infrastructural damage caused by the event, especially in Jono-Oge area, where the flow distance was longest. The authors performed preliminary and detailed surveys in the area twice by conducting Portable Dynamics Cone Penetration Test (PDCPT), collecting disturbed and undisturbed samples and using aerial drone (UAV) photography. The findings of the reconnaissance survey are described here along with subsequent data interpretation. Finally, the mechanism of the flow-slides is discussed.     

Increased impact strength of biodegradable poly(lactic acid)/poly(butylene succinate) blend composites by using isocyanate as a reactive processing agent

Poly(lactic acid) (PLA) blended with poly(butylene succinate) (PBS) was prepared in the presence of lysine triisocyanate (LTI) by using a twin‐screw extruder and injection molding machine. The physical properties, rheological behavior, compatibility, and morphology were investigated by using a tensile test, a Charpy impact test, melt mass‐flow rate (MFR) measurements, size exclusion chromatography (SEC), and laser scanning confocal microscopy (LSCM). The impact strength of PLA/PBS(90/10 wt %) blend composite was about 18 kJ/m² in the absence of LTI, and it increased to 50–70 kJ/m² in the presence of LTI at 0.5 wt %. The MFR value of PLA/PBS(90/10 wt %) decreased from 25 g/10 min at 200°C in the absence of LTI to approximately 3 g/10 min in the presence of LTI. These results imply that isocyanate groups of LTI reacted with both terminal hydroxyl or carboxyl groups of the polymers. Spherical particles at 1 μm were observed by using LSCM in the presence of LTI. These results indicate that the LTI is a useful reactive processing agent to increase the compatibility of PLA/PBS blend composites to increase the impact strength of PLA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Multilayer formation via spinodal decomposition in TiO2-VO2 epitaxial films on sapphire substrates

We present multilayer formation via spinodal decomposition in rutile TiO₂-VO₂ (TVO) epitaxial films on sapphire substrates. (001)- and (101)-oriented TVO solid-solution films are grown epitaxially on TiO₂/Al₂O₃ using a pulsed laser deposition technique and annealed inside the spinodal region. X-ray diffraction measurements and scanning transmission electron microscopy (STEM) observations show that the films are phase-separated along the [001] direction and lamellar structures are formed in a parallel or slanted direction to the sapphire substrates depending on the film orientation. The results indicate the multilayer formation via spinodal decomposition in the TVO films. STEM investigations also reveal a relatively high Ti concentration in the decomposed phases, reflecting the influence of lattice deformation on the phase decomposition in the films. Our work shows that spinodal decomposition is a promising approach for the formation of a multilayer structure in TVO films and helps deepen understanding the spinodal decomposition in TVO system.     

Soret coefficient of a sodium germanate glass melt: Experiment,theory, and molecular dynamics simulation

The Soret effect is a diffusion phenomenon driven by a temperature gradient in a multicomponent system. This effect in condensed systems is not fully understood. Previously, we reported a theoretical model called “adjusted Kempers model” to predict the Soret coefficient in glass melts, and compared the experimental value to the theoretical value for 11Na₂O-89B₂O₃ (mol%) melts. Here, molecular dynamics calculations, as well as theoretical and experimental values, are quantitatively compared in 10Na₂O-90GeO₂ melts. We used a vertical tubular furnace to cause a temperature gradient and heated the sample from top side to reduce the natural convection. We measured the composition of 10Na₂O-90GeO₂ glass samples after 45, 90, and 180 hours of heat treatment under a temperature gradient, and estimated the steady-state Soret coefficient near 1373 K to be 1.09 × 10⁻³ K⁻¹. In addition, we calculated Soret coefficients to be 3.65 × 10⁻³ K⁻¹ and 1.85 × 10⁻³ K⁻¹ in theory and molecular dynamics calculation, respectively. The ratios between the experimental and theoretical Soret coefficients were 1.2 and 3.3 for 11Na₂O-89B₂O₃ melts and 10Na₂O-90GeO₂ melts, respectively. The difference in ratios may be attributed to the mass and size of diffusion species in the glass melts.     

Micrometer-scaled OFET channel patterns fabricated by using PEDOT/PSS microfibers

We have easily fabricated channel patterns of organic field-effect transistors (OFETs), in which channel lengths were 5 μm, by using wet-spun poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) microfibers with diameters of ca. 5 μm. Pentacene-based FETs with a top-contacted configuration, showed a hole mobility of 0.13 cm² V^?1 s^?1 and on/off current ratio of 9.4 × 10⁴. The device also showed large current of ca. 160 μA (V_D = ?50 V; V_G = ?50 V), reflecting shorter channel length of the devices. We have evaluated self-assembled monolayer (SAM) through measurements of water contact angle and by Zisman plot. As a result, critical surface tension of the octadecyltrichlorosilane (OTS)-treated SiO₂ surface is 17 mN m^?1 which is consistent with that of well-known SAM. We also well analyzed the cross-sections of the device by a scanning transmission electron microscopic (STEM) technique. The results indicated that the thicknesses of the pentacene layer in the channel part and Au layer in the source/drain part were ca. 30 and 30 nm, respectively. Furthermore, it is also indicated that the 100-nm grains of the pentacene were well adhered on the surface of the SAM-formed SiO₂ layer.