Effects of walking speed and age on the directional stride regularity and gait variability in treadmill walking

Journal of Mechanical Science and Technology - In Inertial measurement unit (IMU) based gait analysis systems, the shoe-type sensor is not commonly used, unlike trunk attached sensors. The purpose...     

Dual wavelength OLEDs with blue and yellow emission peaks

New organic light emitting diodes (OLEDs) with dual peak emission spectra were fabricated and their electrical and optical characteristics were investigated. In the experiments, the blue emission materials GDI602 and GDI602 were doped with GDI691(2%)[GDI602∶GDI691(2%)] and the yellow emission material Alq3 was doped with Rubrene(10%)[Alq3∶Rubrene(10%)]. Under an applied voltage of 10 V, the OLED with the GDI602/Alq3∶Rubrene(10%) emission layer had a luminance of 325 Cd/m² and a power efficiency of 0.7 lm/W, whereas the OLED with the GDI602∶GDI691(2%)/Alq3∶Rubrene(10%) emission layer had a luminance of 500 Cd/m² and a power efficiency of 0.94 lm/W. The dual peak wavelengths of the OLEDs were fixed but the relative intensities of the peak wavelengths varied according to the applied voltage. The OLED with the GDI602/Alq3∶Rubrene(10%) emission layer showed a somewhat reddish-white emission with a Commission Internationale de L'Eclairage(CIE) coordinate of (0.33, 0.32) at 9 V. In contrast, the OLED with the GDI602: GDI691(2%)/Alq3∶Rubrene(10%) emission layer showed an almost pure white emission with a CIE coordinate of (0.32, 0.33) at 6 V; furthermore, the color changed to blue as the applied voltage was increased.     

3G wireless and cdma2000 1/spl times/ evolution in Korea

The cdma2000/spl reg/ I/spl times/EV-DV system is designed to meet the ever-increasing demand for high-speed packet data transmission while providing the same level of revenue generated by conventional voice communications on existing cdma2000 1/spl times/ systems. It supports concurrent voice and high-speed data on a single cdma 1.25 MHz carrier, and offers improved flexibility for operators to manage data and voice services cost efficiently. However, the Korean market has proved that providing higher bandwidth to the user does not guarantee the success of mobile data service. Users tend not to use expensive mobile wireless data services such as video streaming, video on demand, and MP3 music download service that they feel do not provide enough justification for their costs. The problem LG Telecom faces now as a mobile operator is not only to evolve technologies that enable various services, but also to find a way to provide attractive services at reasonable prices. This article describes experiences in the wireless data market in Korea as well as the market needs and driving forces for cdma2000 1/spl times/EV-DV developments.     

Intersegmental dynamics of the lower limb in vertical jumps

The purpose of this study was to investigate changes in intersegmental dynamics of the lower limb at the instant of push-off in vertical jumps. Using a mathematical model including dynamic equations, the net joint moment (NET) was decomposed into a muscle moment (MUS), gravitational moment, and interaction moment (INT) in terms of joint acceleration and velocity. Ten subjects performed two submaximal jumps(60% and 80% of maximal height) and one maximal jump. Results showed that the hip and ankle joints mainly utilized MUS to generate NET at the push-off instant, while the knee joint primarily used INT at the instant of push-off. The hip MUS increased with increasing jump height because the deep countermovement (larger flexion angle of hip and knee joint at the push-off instant) in maximal jump was a disadvantage from intersegmental dynamics, but may be neurophysiologically advantageous.     

Structural Safety Assessment of Ocean-Floating Photovoltaic Structure Model

In designing photovoltaic (PV) structures made to float in oceans through use of a buoyant system, one must consider wave load and mooring load in addition to the load applied in PV generation systems installed on land. It is also necessary to study the safety of such floating structures during high tide and low tide, focusing on aspects such as mooring conditions caused by large differences in reservoir depth between low and high water levels. This study focuses on finite element analysis and strength assessment of an ocean-floating PV structure. The aims of this study are to suggest a structure for a floating PV buoy with a tidal power plant to be installed in Sihwaho Lake, to analyze its safety, and to propose a suitable structure model for an ocean-floating PV system. As a result of structural analysis and safety assessment of the proposed unit structure, the maximum unity check (UC) value of allowable stress design (ASD) for load conditions with maximum stress was found to be much smaller than the reference value, indicating a sufficient degree of safety. In the structural design of floating PV generation systems, wind and wave loads must be considered in the detailed design of the overall and local structure. A 20 kW ocean-floating PV system was developed in November 2013 based on this study.     

Synthesis of biodiesel from an oil fraction separated from food waste leachate

Biodiesel was produced from an oil fraction separated from food waste leachate, using a batch reactor system, to evaluate its potential as a renewable energy source for the first time. In order to reduce the free fatty acid content of the leachate oil fraction, three different acid catalysts, H₂SO₄, zeolite and Amberlyst-15, were used in the pretreatment process. The residual oil fraction after pretreatment was further treated over KOH as a base catalyst to produce a fatty acid methyl ester (FAME). The FAME content in the product was analyzed using GC/MS. A large number of different FAMEs were detected, which is characteristic of the food-waste-derived raw material used in this study. The FAME content of the product was highest when pretreated over Amberlyst-15, followed by trans-esterification. Additional refining and process optimization would be expected to further increase the FAME content. Therefore, it was concluded that the production of biodiesel from the oil fraction separated from food waste leachate is promising.     

Novel ESD protection transistor including SiGe buried layer toreduce local temperature overheating

This paper introduces a new NMOS electrostatic discharge (ESD) protection transistor which contains a buried SiGe narrow-bandgap layer between the source and the drain region. The simulations carried out by a two-dimensional simulator show that the ESD induced current flows mainly through the buried layer in the new structure, which strongly suppresses local overheating on the silicon surface. As a result, the peak lattice temperature for the Machine Model with 300 V level is 400°C in the new structure, which is much lower than in the normal structure, 1150°C. In the new structure, the parasitic bipolar turn-on is faster and the bipolar current gain (β) is higher than in the normal structure by as much as 8 ns and 10 times, respectively. The snapback voltage is reduced by 1.5 V in the new structure     

A new assay for endonuclease/methyltransferase activities based on graphene oxide

A new endonuclease/methyltransferase activity assay method based on graphene oxide (GO) is developed. Substrate DNA is designed to possess a double-stranded part to serve as a nuclease substrate and a single-stranded part for anchoring the DNA to the GO surface via strong noncovalent binding. Nuclease-mediated DNA hydrolysis induces the recovery of fluorescence intensity of the dye attached to the end of the double-stranded DNA region. This GO-based method allows real-time measurement and quantitative assay for endonuclease/methyltransferase activities in short time.     

Preparation of scrolled graphene oxides with multi-walled carbon nanotube templates

A simple and efficient wet-chemical strategy was developed to form graphene oxide scrolls around multi-walled carbon nanotube templates through covalent bond formation. Scanning electron microscopy, atomic force microscopy, transmission electron microscopy and dynamic light scattering measurements confirmed the scrolled conformation of graphene oxide sheets while Fourier transform infrared spectroscopy and X-ray photoelectron data indicated the formation of covalent bonds between the scrolled sheets and the nanotubes. Conformational changes of the graphene oxide sheets were also monitored by Raman spectroscopy. All the data suggested successful formation of graphene oxide scrolls with multi-walled carbon nanotube templates.