Effect of various rib arrangements on heat transfer in a semicylinder channel with effusion flow

The flow and heat transfer characteristics of various rib configurations on a concave channel surface with effusion holes were investigated. A semicylindrical channel with three rows of effusion holes was used to simplify the blade leading edge and eight kinds of ribs were attached on the internal concave surface for comparison. Continuous and broken ribs were both applied at 90°, as were upstream-pointed V-shaped and downstream-pointed V-shaped ribs. The Reynolds-averaged Navier–Stokes equation was solved using commercial software. The result included the divided-area-averaged and local Nusselt number distribution; the overall average Nusselt number on the concave surface is also discussed.     

Improving quality of multimedia services through network performance isolation in a mobile device

Multimedia Tools and Applications - Due to the advancement of hardware and software, today’s mobile devices, such as smartphones, tablet PCs, and laptops, are capable of providing a wide...     

Power density optimization for MEMS piezoelectric micro power generator below 100 Hz applications

Microsystem Technologies - In piezoelectric based micro-power generator (PMPG), electrical energy is generated from mechanical vibration by gaining on the piezoelectric effects. This study...     

Paeonolide as a Novel Regulator of Core-Binding Factor Subunit Alpha-1 in Bone-Forming Cells

Paeonia suffruticosa has been extensively used as a traditional medicine with various beneficial effects; paeonolide (PALI) was isolated from its dried roots. This study aimed to investigate the novel effects and mechanisms of PALI in pre-osteoblasts. Here, cell viability was evaluated using an MTT assay. Early and late osteoblast differentiation was examined by analyzing the activity of alkaline phosphatase (ALP) and by staining it with Alizarin red S (ARS). Cell migration was assessed using wound healing and Boyden chamber assays. Western blot and immunofluorescence analyses were used to examine the intracellular signaling pathways and differentiation proteins. PALI (0.1, 1, 10, 30, and 100 μM) showed no cytotoxic or proliferative effects in pre-osteoblasts. In the absence of cytotoxicity, PALI (1, 10, and 30 μM) promoted wound healing and transmigration during osteoblast differentiation. ALP staining demonstrated that PALI (1, 10, and 30 μM) promoted early osteoblast differentiation in a dose-dependent manner, and ARS staining showed an enhanced mineralized nodule formation, a key indicator of late osteoblast differentiation. Additionally, low concentrations of PALI (1 and 10 μM) increased the bone morphogenetic protein (BMP)–Smad1/5/8 and Wnt–β-catenin pathways in osteoblast differentiation. Particularly, PALI (1 and 10 μM) increased the phosphorylation of ERK1/2 compared with BMP2 treatment, an FDA-approved drug for bone diseases. Furthermore, PALI-mediated early and late osteoblast differentiation was abolished in the presence of the ERK1/2 inhibitor U0126. PALI-induced RUNX2 (Cbfa1) expression and nuclear localization were also attenuated by blocking the ERK1/2 pathway during osteoblast differentiation. We suggest that PALI has biologically novel activities, such as enhanced osteoblast differentiation and bone mineralization mainly through the intracellular ERK1/2-RUNX2 signaling pathway, suggesting that PALI might have therapeutic action and aid the treatment and prevention of bone diseases, such as osteoporosis and periodontitis.     

Investigation of graphene‐on‐metal substrates for SPR‐based sensor using finite‐difference time domain

In this study, the authors investigated the effects of a single layer graphene as a coating layer on top of metal thin films such as silver, gold, aluminum and copper using finite‐difference time domain method. To enhance the resolution of surface plasmon resonance (SPR) sensor, it is necessary to increase the SPR reflectivity and decrease the full‐width‐half maximum (FWHM) of the SPR curve so that there is minimum uncertainty in the determination of the resonance dip. Numerical data was verified with analytical and experimental data where all the data were in good agreement with resonance angle differing in <10% due to noise present in components such as humidity and temperature. In further analysis, reflectivity and FWHM were compared among four types of metal with various thin film thicknesses where graphene was applied on top of the metal layers, and data was compared against pure conventional metal thin films. A 60 nm‐thick Au thin film results in higher performance with reflectivity of 92.4% and FWHM of 0.88° whereas single layer graphene‐on‐60 nm‐thick Au gave reflectivity of 91.7% and FWHM of 1.32°. However, a graphene‐on‐40 nm‐thick Ag also gave good performance with narrower FWHM of 0.88° and reflection spectra of 89.2%.Inspec keywords: graphene, surface plasmon resonance, finite difference time‐domain analysis, reflectivity, metallic thin films, silver, gold, aluminium, copper, chemical sensors, biological techniquesOther keywords: graphene‐on‐metal substrates, SPR‐based sensor, finite‐difference time domain, metal thin films, surface plasmon resonance sensor, SPR curve, resonance angles, reflectivity, C, Ag, Au, Al, Cu     

Characteristics of ITO films deposited on a PET substrate under various deposition conditions

ITO films, with a thickness of 150 nm to 160 nm, were deposited on an unheated hard coated PET substrate or non-alkali glass substrate via dc magnetron sputtering. Depositions were carried out under the following various conditions: total gas pressure (P_tot), dc sputtering power, target — substrate (T-S) distance, and O₂ or H₂ addition ratio. The ITO coated on the PET substrate showed relatively lower resistivity than that of the ITO coated on a glass substrate. Relatively small changes in the resistance (ΔR/R₀=0.4) of the films were obtained for each deposition condition for the ITO/PET deposited under a sputtering power of 70 W, P_tot of 0.5 Pa, and T-S of 50 mm. It has been confirmed that the results of the electrical property showed concurrence with the results of the bending test. Specifically, the films that have a good electrical property showed only a small change in resistance to the increasing cycle number for each deposition condition. Therefore, it can be assumed that the increased resistance of the ITO films could be due to the formation of micro defects such as micro-cracks and the micro detachment of the ITO film from the flexible PET substrate.     

Optimization of hot pressing parameters in membrane electrode assembly fabrication by response surface method

The aim of this research was to study the effect of the membrane electrode assembly fabrication factors on the performance of a passive micro direct methanol fuel cell by studying the hot pressing parameters. The MEA was prepared with a Nafion 117 membrane and porous electrodes having an active area of 1 cm² with Pt and Pt/Ru catalysts of 8 mg cm⁻² loading at the cathode side and anode side, respectively. The Design of Experiment work was performed with the Response Surface Method using the Central Composite Design. The One-factor-at-a-time method was used to select the significant level of factors for the DOE method, which are temperature in the range of 100–135 °C and pressure in the range of 6.0–16.0 kgf cm⁻². The results show that the proposed mathematical model in the Response Surface Method can be used adequately for prediction and optimization within the factor levels investigated. The combined optimum hot pressing parameters that gave the highest performance of 7.23 mW cm⁻² predicted in this study are temperature 130 °C and pressure 6 kgf cm⁻².     

Geometrical effects in SRO-MISS switching devices

The switching behaviour of MISS devices was studied as a function of the geometrical shape. It was found that the MISS characteristics are very dependent upon the area of the electrode as well as the area of the p-n junction. If the ratio of the electrode area to the p-n junction area is decreased, the switching voltage increases. This is because a fraction of the current through the electrode flows laterally (current spreading), and increases the switching voltage of the device. The effect of current spreading in the device was shown more convincingly in further experiments on isolation, and the effect of the electrode perimeter. The degree of the current spreading was found to be dependent upon the conductivity of the SRO layer, which alters the sensitivity of the switching parameters to the geometry.     

High sensitivity and small size MEMS capacitive microphone using a novel slotted diaphragm

A novel single-chip microelectromechanical systems (MEMS) capacitive microphone with a slotted diaphragm for sound sensing is developed to minimize the microphone size and improve the sensitivity by decreasing the mechanical stiffness of the diaphragm. The behaviors of the microphones with clamped and slotted diaphragms are analyzed using the finite element method (FEM). According to the results, a clamped microphone with a 2.43 × 2.43 mm² diaphragm and a slotted one with a 1.5 × 1.5 mm² diaphragm have the same mechanical sensitivity, but the size of slotted microphone is at least 1.62 times smaller than clamped structure. The results also yield a sensitivity of 5.33 × 10⁻⁶ pF/Pa for the clamped and 3.87 × 10⁻⁵ pF/Pa for the slotted microphone with a 0.5 × 0.5 mm² diaphragm. The sensitivity of the slotted diaphragm is increased 7.27 times. The pull-in voltage of the clamped microphone is 105 V, and slotted one is 49 V. The pull-in voltage of the slotted microphone is about 53% decreased.