Power management system for a 2.5 W remote sensor powered by a sediment microbial fuel cell

One of the challenges in using wireless sensors that require high power to monitor the environment is finding a renewable power source that can produce enough power. Sediment microbial fuel cells (SMFCs) are considered an alternative renewable power source for remote monitoring, but current research on SMFCs has demonstrated that they can only produce several to tens of mW of continuous power. This limits the use of SMFCs as an alternative renewable remote power source to mW-level power. Such low power is only enough to operate a low-power sensors. However, there are many remote sensors that require higher power, on the order of watts. Current technology using a SMFC to power a remote sensor requiring watts-level intermittent power is limited because of limitations of power management technology. Our goal was to develop a power management system (PMS) that enables a SMFC to operate a remote sensor consuming 2.5 W of power. We designed a custom PMS to store microbial energy in capacitors and use the stored energy in short bursts. Our results demonstrate that SMFCs can be a viable alternative renewable power source for remote sensors requiring high power.     

The effect of top and bottom lids on natural convection inside a vertical cylinder

Natural convection experiments inside a vertical cylindrical cavity were performed for Rayleigh numbers of 1.08 × 10¹⁰–2.11 × 10¹³ and for four different geometrical arrangements: both-open (pipe-shape), bottom-closed (cup-shape), top-closed (cap), and both-closed (cavity) cylinders. A copper electroplating system was employed for the measurements of heat transfer rates using analogy concept. The lids used to close top or bottom were adiabatic; i.e. inactive surfaces in the electrodeposition experiments. The bottom-closed cavity showed the highest heat transfer rates and then followed both-closed, both-open, top-closed ones in both laminar and turbulent flows. The results were in satisfactory agreements with the existing correlations developed for similar geometrical configurations and the empirical correlations were derived. The numerical simulations were carried out using the FLUENT 6.2 to explain the measured results. The analysis of the streamline and the local Nusselt number gave explanations for the observation.     

2-D WO3 decorated with Pd for rapid gasochromic and electrical hydrogen sensing

The ultrathin two-dimensional (2D) nanomaterials display unique properties owing to their ultrahigh specific surface area and strong quantum confinement of electrons in two dimensions. In this work, we fabricated a rapid gasochromic and electrical hydrogen sensing system containing 2D WO₃ and Pd nanoparticles. 2D WO₃ nano-plates (NP) are synthesized using sol–gel method and Pd nanoparticles are coated on WO₃ by green photochemical deposition method. The sensor is fabricated by dispersing the 2D WO₃/Pd composite on filter paper. In presence of hydrogen gas, 2D WO₃/Pd composite produces visible change in color from brown to dark blue. With the fabricated sensor, as low as 0.1% H₂ gas in air at room temperature can be easily detected using electrical sensing scheme whereas for higher concentration from 1 to 100%, eye readable gasochromic scheme can be utilized. The use of 2D WO₃ decreased the response time in great deal compared to WO₃ nanoparticles indicating the advantage of 2D structure in fabricating rapid response H₂ sensors. The proposed method is simple and can be easily employed to large scale fabrication system for commercial applications.     

Recrystallization and precipitation behavior of low-activation V-Cr-Ti alloys after cold rolling

Recrystallization and precipitation behavior after cold working were investigated for three V-4Cr-4Ti alloys, NIFS-HEAT-1, NIFS-HEAT-2 and US 832665, which contain different levels of impurities. The decrease in hardness and the initiation of recrystallization against test temperature do not depend on the oxygen level. However, the rate of grain growth decreased with the increase in the impurity levels. Bimodal distribution of the precipitates was observed after annealing at 1273 K. The large precipitates were Ti-rich precipitates, and the small ones were composed mainly of Ti, C and O (Ti-C-O precipitates). The impurities were dissolved from Ti-C-O precipitates above 1273 K, and the level of impurities in the matrix increased and resulted in the increase in the hardness. Based on the results, the annealing temperature for V-4Cr-4Ti alloys is recommended not to exceed 1273 K for the purpose of maintaining good mechanical properties such as tensile and impact properties.     

Redox-induced performance degradation of anode-supported tubular solid oxide fuel cells

Redox behavior of a Ni-Y₂O₃-stabilized ZrO₂ (YSZ) composite anode support and the performance degradation of an anode-supported tubular solid oxide fuel cell (SOFC) were studied under complete oxidation and reduction conditions (degrees of oxidation and reduction = 100%). Materials characterization studies showed that the exposure time in oxidizing and reducing atmospheres played a critical role in the degradation of the porous structures and the physical properties of the anode support. In particular, the redox cycling with an 8 h exposure time resulted in the cracking of YSZ network, leading to significant decay of the mechanical strength. The polarization experiments on the redox-cycled anode-supported tubular cell showed serious performance degradation as a result of the decreases of open-circuit potential and power density. The ac-impedance measurements combined with microstructural observations indicated that the performance degradation resulted mainly from (i) the degradation of anode support, (ii) microcracks across the whole cell, and (iii) interface delamination.     

High-density inductively coupled plasma chemical vapor deposition of silicon nitride for solar cell application

The silicon nitride films were deposited by means of high-density inductively coupled plasma chemical vapor deposition in a planar coil reactor. The process gases used were pure nitrogen and a mixture of silane and helium. Passivated by silicon nitride, solar cells show efficiency above 13%. Strong H-atom release from the growing SiN film and Si–N bond healing are responsible for the improved electrical and passivation properties of SiN film. This paper presents the optimal refractive index of SiN for single layer antireflection coating as well as double layer antireflection coating in solar cell applications.     

Nanoparticle‐Enhanced Silver‐Nanowire Plasmonic Electrodes for High‐Performance Organic Optoelectronic Devices

Improved performance in plasmonic organic solar cells (OSCs) and organic light‐emitting diodes (OLEDs) via strong plasmon‐coupling effects generated by aligned silver nanowire (AgNW) transparent electrodes decorated with core–shell silver–silica nanoparticles (Ag@SiO₂NPs) is demonstrated. NP‐enhanced plasmonic AgNW (Ag@SiO₂NP–AgNW) electrodes enable substantially enhanced radiative emission and light absorption efficiency due to strong hybridized plasmon coupling between localized surface plasmons (LSPs) and propagating surface plasmon polaritons (SPPs) modes, which leads to improved device performance in organic optoelectronic devices (OODs). The discrete dipole approximation (DDA) calculation of the electric field verifies a strongly enhanced plasmon‐coupling effect caused by decorating core–shell Ag@SiO₂NPs onto the AgNWs. Notably, an electroluminescence efficiency of 25.33 cd A^?1 (at 3.2 V) and a power efficiency of 25.14 lm W^?1 (3.0 V) in OLEDs, as well as a power conversion efficiency (PCE) value of 9.19% in OSCs are achieved using hybrid Ag@SiO₂NP–AgNW films. These are the highest values reported to date for optoelectronic devices based on AgNW electrodes. This work provides a new design platform to fabricate high‐performance OODs, which can be further explored in various plasmonic and optoelectronic devices.     

Spectroscopic Analysis of the Structure and Properties of Alkali Tellurite Glasses

Structural development of tellurite glasses with the addition of Li₂O and Na₂O has been studied using infrared, Raman, and X-ray photoelectron spectroscopies. The increase in intensity of the peak at 755 cm⁻¹ in the infrared spectra as compared to the peak at 620 cm ⁻¹ suggests the transformation of TeO₄ building units to TeO₃ pyramids with the addition of alkali oxide. Proposed structural change is further supported by the strong compositional dependence of the 755-cm⁻¹ peak in the Raman spectra as well as by the formation of a shoulder in the O 1 s peak of X-ray photoelectron spectra. In contrast to alkali silicate glasses, formation of nonbridging oxygens with the addition of alkali oxide is not observed.     

Eleutheroside E,an active compound from Eleutherococcus senticosus,regulates adipogenesis in 3T3-L1 cells

In this study, we investigated the anti-adipogenic effects of Eleutherococcus senticosus and its active compounds in vitro to examine new functions. We first analyzed the active compounds in E. senticosus growing in Korea using HPLC and found that the concentration of eleutheroside B and E was higher in stems and roots than in other plant parts. There were no significant (p<0.05) differences in eleutheroside concentration between plant ages. Anti-adipogenic effects of E. senticosus on lipid accumulation in 3T3-L1 cells were examined. Extracts of stems and roots more effectively inhibited lipid accumulation in 3T3-L1 cells than extracts of other plant parts. Eleutheroside E was responsible for the pharmacological anti-adipogenic effects via regulation of the mTOR pathway. This is the first report of an anti-adipogenic effect of E. senticosus and the active compound eleutheroside E.