Relay-based single carrier transmission with SFBC in uplink fast fading channels

This letter proposes a relay-based single carrier frequency-domain equalization (SC-FDE) with space-frequency block code (SFBC) in a distributed fashion. The proposed scheme achieves spatial diversity in uplink fast fading channels without the complexity of multiple antennas at source (mobile equipment). The source of the proposed system has a very simple transmitter structure without any increase of peak-to-average power ratio (PAPR). In order to obtain spatial diversity, the transmit sequence of relay is efficiently generated in the time domain, which realizes the SFBC. The corresponding destination structure and frequency domain equalization are also presented. Simulation result shows that the proposed system considerably outperforms the distributed space-time block code (D-STBC) SC-FDE over fast fading channels.     

Phenylpropanoids from red kohlrabi sprouts inhibits nitric oxide production in RAW 264.7 macrophage cells

The sprouts of red kohlrabi (Brassica oleracea var. gongylodes) were extracted with methanol, and the concentrated extracts were successively partitioned with ethyl acetate, n-butyl alcohol (n-BuOH), and H₂O. From the n-BuOH fraction, four phenylpropanoids were isolated through repeated silica gel and ODS column chromatographies. On the basis of physico-chemical and spectroscopic data including NMR, MS, and IR, the isolated compounds were identified as 3-(3,4,5-trimethoxyphenyl)-2E-propenoic acid methyl ester (1), (E)-sinapic acid methyl ester (2), (E)-sinapoyl glucoside (3), and lawsoniaside B (4). Moreover, the compounds dose-dependently inhibited NO production in RAW 264.7 cells with IC₅₀ values of 41.22 (1), 38.32 (3), and 22.65 (4) μM, respectively. With further studies, these compounds may be potentially useful in developing new anti-inflammatory agents.     

Inkjet printing of conjugated polymer precursors on paper substrates for colorimetric sensing and flexible electrothermochromic display

Inkjet-printable aqueous suspensions of conjugated polymer precursors are developed for fabrication of patterned color images on paper substrates. Printing of a diacetylene (DA)-surfactant composite ink on unmodified paper and photopaper, as well as on a banknote, enables generation of latent images that are transformed to blue-colored polydiacetylene (PDA) structures by UV irradiation. Both irreversible and reversible thermochromism with the PDA printed images are demonstrated and applied to flexible and disposable sensors and to displays.     

Blocker design for axisymmetric hot steel forging by expert system and fem

A hot forging of steel usually consists of buster, blocker and finisher processes. The blocker is a transient shape to ease the metal flow in the finisher dies and it is designed by experienced engineers with rules. Recently, due to the lack of such engineers, it is necessary to develop an expert system to automate the design operations. In the present study, a rule-based expert system was developed for the blocker design of axisymmetric hot steel forging. In this paper, the major rules used in the system are summarized and the designed blockers were verified by rigid thermoviscoplastic finite element method.     

Synergetic effect of BN for the electrical conductivity of CNT/PAN composite fiber

Carbon nanotube (CNT) fillers in composite materials improve electrical conductivity, thermal stability, and mechanical properties. Boron nitride (BN) is an insulating material that is also thermally stable. Therefore, CNT and hexagonal boron nitride (hBN) fillers have been used to obtain composite materials’ high electrical conductivity. In this study, CNT-hBN/polyacrylonitrile (PAN) fibers were spun using simple wet-spinning and the effect of hBN on the electrical conductivity of the CNT-hBN/PAN composite was investigated. Contrary to predictions, as the content of the insulating material, BN, increased up to 15 wt%, the electrical resistance of the composite fiber decreased.

     

Moment equation for the packed column with spherical composites

A mathematical model was proposed to describe the mass-transport phenomena in packed column with spherical composites which are consisted of the outer shells and the inner spheres. Any contact resistance between the former and the latter was assumed to be negligible. The first and the second moments were derived by means of the moment generating properties of Laplace transform.     

Development and application of an oligonucleotide microarray and real-time quantitative PCR for detection of wastewater bacterial pathogens

Conventional microbial water quality test methods are well known for their technical limitations, such as lack of direct pathogen detection capacity and low throughput capability. The microarray assay has recently emerged as a promising alternative for environmental pathogen monitoring. In this study, bacterial pathogens were detected in municipal wastewater using a microarray equipped with short oligonucleotide probes targeting 16S rRNA sequences. To date, 62 probes have been designed against 38 species, 4 genera, and 1 family of pathogens. The detection sensitivity of the microarray for a waterborne pathogen Aeromonas hydrophila was determined to be approximately 1.0% of the total DNA, or approximately 10(3)A. hydrophila cells per sample. The efficacy of the DNA microarray was verified in a parallel study where pathogen genes and E. coli cells were enumerated using real-time quantitative PCR (qPCR) and standard membrane filter techniques, respectively. The microarray and qPCR successfully detected multiple wastewater pathogen species at different stages of the disinfection process (i.e. secondary effluents vs. disinfected final effluents) and at two treatment plants employing different disinfection methods (i.e. chlorination vs. UV irradiation). This result demonstrates the effectiveness of the DNA microarray as a semi-quantitative, high throughput pathogen monitoring tool for municipal wastewater.     

The simulation and test results of the TSC type RPC & HF system for enhancement of the KSTAR power system stabilization

The Korea Superconducting Tokamak Advanced Research (KSTAR) device requires a large pulse power to generate and confine plasma in order to function as a nuclear fusion device. Such a large pulse power causes voltage-drop and voltage-distortion in the electric power system, because it generates large reactive power and harmonic currents. These effects are detrimental to other experimental devices and deteriorate the power quality delivered by the power system. Therefore, it is important to stabilize the KSTAR power system by compensating for the reactive power and rejecting the harmonic currents using a Reactive Power Compensator (RPC) & Harmonic Filter (HF) system. The TSC type RPC & HF system has been fabricated to have a total capacity of 35 MVar and included two features. The first is a fast response speed of within 10 cycles to compensate for the reactive power. The second is a stable KSTAR power system in which no resonance is detected due to the installation of the TSC type RPC & HF system. This paper presents simulation results of the TSC type RPC & HF system and test results of the plasma experiment of KSTAR carried out in 2009.     

Ammonium fluoride-activated synthesis of cubic δ-TaN nanoparticles at low temperatures

Cubic delta-tantalum nitride (δ-TaN) nanoparticles were selectively prepared using a K₂TaF₇ + (5 + k) NaN₃ + kNH₄F reactive mixture (k being the number of moles of NH₄F) via a combustion process under a nitrogen pressure of 2.0 MPa. The combustion temperature, when plotted as a function of the number of moles of NH₄F used, was in the range of 850°C to 1,170°C. X-ray diffraction patterns revealed the formation of cubic δ-TaN nanoparticles at 850°C to 950°C when NH₄F is used in an amount of 2.0 mol (or greater) in the combustion experiment. Phase pure cubic δ-TaN synthesized at k = 4 exhibited a specific surface area of 30.59 m²/g and grain size of 5 to 10 nm, as estimated from the transmission electron microscopy micrograph. The role of NH₄F in the formation process of δ-TaN is discussed with regard to a hypothetical reaction mechanism.     

New Charge Carrier Transport-Assisting Paths in Ultra-Long GaN Microwire UV Photodetector

GaN-based materials are the hottest research topic in UV photodetectors (PDs) because of their low operating voltage, small volume, long lifetime, high-temperature resistance, and low energy consumption. However, there are still fundamental issues to be overcome, and the most important issue is to get a photoconductive gain. In this paper, the following new approaches are provided to innovatively improve the photoconductive gain of UV PDs in GaN-based materials. First, the aspect ratio of the 1D GaN microwire (MW) structure is dramatically improved by analyzing the pulse growth mechanism using the metal-organic vapor deposition system. Second, the comprehensive strain behavior in the MW epitaxial growth system is successfully analyzed. Third, the fabricated metal-semiconductor-metal-based MW UV PD shows photoresponsivity and sensitivity of 28.365 A W⁻¹ and 93.16%, respectively, at the −2 V bias, which significantly outperforms the conventional structures in the UV region. Finally, a trap-assisted Poole–Frenkel effect-based energy bandgap mechanism, that allows the defect level formed by lattice mismatch between the substrate and GaN to be used as an electron carrier path, is newly defined. This study will present the direction of future UV PDs by providing a new MW structure based on GaN materials, a third-generation semiconductor.