Effects of ultrahigh pressure extraction conditions on yields and antioxidant activity of ginsenoside from ginseng

Ultrahigh pressure technique was employed to extract ginsenosides from roots of ginseng (Panax ginseng C.A. Meyer). The optimal conditions for ultrahigh pressure extraction (UPE) of total ginsenosides were quantified by UV-vis spectrophotometry with the ginsenoside Re as standard, the signal ginsenosides were quantified by HPLC and ELSD with ginsenosides Re, Rg(1), Rb-1, Rc and Rb-2 as standards. Orthogonal design was applied to evaluate the effects of four independent factors (extraction pressure, extraction temperature, extraction time and ethanol concentration) on the yield and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of ginsenoside, which are based on microwave extraction (ME), ultrasound extraction (UE), soxhlet extraction (SE) and heat reflux extraction (HRE) method. The results showed that UPE method can produce ginsenoside with the highest yield and the best radical scavenging activity compared to other used ones. Scanning electron microscopic (SEM) images of the plant cells after ultrahigh pressure treatment was obtained to provide visual evidence of the disruption effect.

BONDING OF ALUMINA AND METAL USING BULK METALLIC GLASS FORMING ALLOY

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al2O3 ceramic using Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.

Bonding Of Alumina And Metal Using Bulk Metallic Glass Forming Alloy

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al2O3 ceramic using Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.

FREQUENCY AND TEMPORAL COHERENCE PROPERTIES OF DISTRIBUTED BRAGG REFLECTOR LASER

This article presents the investigation of frequency and temporal coherence properties of distributed Bragg reflector laser. In this scheme, a square-wavefrom voltage is applied to the phase section of the laser to little optical wavelength, and delayed optical heterodyne technique is used for the analysis of spectral characteristics. Experiments show that lightwaves emitted from the same active region asynchronously are partially frequency and temporal coherent. When the two wavelengths are closer, the two waves are strong v coherent, and the coherence properties get weak as the delay v time increases. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Left 52: 822-825, 2010 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25031

Optical spectral relation between the master and the frequency-locked slave lasers

In this paper, the spectral relation between the master and the frequency-locked slave laser (FLSL) is investigated by the conventional technique of optical intensity modulation and optical heterodyne. Experimentally, we demonstrate that under complete and stable locking condition, the lightwave of the FLSL and the sidebands of the master laser produced by the optical intensity modulation are perfectly coherent (frequency coherence). Referring to our recent studies, the lightwave of the master laser and its corresponding sidebands are also perfectly coherent. Additionally, the spectral structures of two perfectly coherent lightwaves are identical in the level of wave train. Therefore, we indirectly verify that the spectral structures of the FLSL and the master laser are identical in the level of wave train.

DISCRETELY TUNABLE FIBER RING LASER USING FBG TUNABLE FILTER AND MACH-ZEHNDER INTERFEROMETER

A discretely tunable Er-doped fiber-ring laser using a fiber Mach-Zehnder interferometer (MZI) and a tunable fiber Bragg grating (FBG) is proposed. In this scheme, the combination of MZI and FBG acts as a discrete wavelength selector. Analysis of its transmission function shows that discrete wavelength tuning can be realized, and experiments demonstrate 64 single-mode outputs with a mode spacing of 181.7 pm, and the output power is quite stable in the whole tuning range. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51 2595-2598, 2009; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.24690

FREQUENCY RESPONSE OF FIBER RING RESONATOR AND ITS APPLICATION IN DFB LASER WAVELENGTH VARIATION MEASUREMENT

Frequency response of a fiber ring resonator (FRR) composed of an ordinary optical coupler and a segment of optical fiber is theoretically and experimentally investigated. The frequency response equation based oil small-signal modulation is derived and studied in detail. It is shown that the shape of the frequency response curve is very sensitive to the wavelength; as a result, the FRR can be applied to measure the wavelength of a lightwave source with high resolution. With this method, we demonstrate the measurement of tiny changes of wavelength of a DFB laser. (C) 2009 Wiley Periodicals. Inc. Microwave Opt Technol Lett 51 2444-2448, 2009 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24608

Q-switched and mode-locked diode-pumped Nd : YVO4 laser with an intracavity composite semiconductor saturable absorber

We have demonstrated a passively Q-switched and mode-locked Nd:YVO4 laser with an intracavity composite semiconductor saturable absorber (ICSSA). Stable Q-switched and mode-locked pulses with Q-switched envelope pulse duration of 180 ns and pulse repetition rate of 72KHz have been obtained. The maximum average output power was 1.45W at 8W incident pump power. The repetition rate of the mode-locked pulses inside the Q-switched envelope was 154 MHz. Experimental results revealed that this ICSSA was suitable for Q-switched and mode-locked solid-state lasers. (c) 2007 Elsevier Ltd. All rights reserved.

High-average-power and high-conversion-efficiency continuous wave mode-locked Nd : YVO4 laser with a semiconductor absorber mirror

A high-power continuous wave (cw) mode-locked Nd:YVO4 solid-state laser was demonstrated by use of a semiconductor absorber mirror (SAM). The maximum average output power was 8.1 W and the optic-to-optic conversion efficiency was about 41 %. At the maximum incident pump power, the pulse width was about 8.6 ps and the repetition rate was 130 MHz. Experimental results indicated that this absorber was suitable for high power mode-locked solid-state lasers. (C) 2006 Elsevier Ltd. All rights reserved.

New algorithms of the TSM and TOM methods for calibrating microwave test fixtures

Based on the conventional through-short-match (TSM) method, an improved TSM method has been proposed in this Letter. This method gives an analytical solution and has almost all the advantages of conventional TSM methods. For example, it has no phase uncertainty and no bandwidth limitation. The experimental results show that the accuracy can be significantly improved with this method. The proposed theory can be applied to the through-open-match (TOM) method. (C) 2002 Wiley Periodicals. Inc.

An 8-b 1-GSmaples/s CMOS cascaded folding and interpolating ADC

This paper presents an 8-bit low power cascaded folding and interpolating analog-to-digital converter (ADC). A reduction in the number of comparators, equal to the number of times the signal is folded, is obtained. The interleaved architecture is used to improve the sampling rate of the ADC. The circuit including a bandgap is implemented in a 0.18-mu m CMOS technology, and measures 1.47 mm X 1.47 mm (including pads). The simulation results illustrate a conversion rate of 1-GSamples/s and a power dissipation of less than 290mW.

Pipeline Architecture and Parallel Computation-Based Real-Time Stereovision Tracking System for Surgical Navigation

This paper studies the development of a real-time stereovision system to track multiple infrared markers attached to a surgical instrument. Multiple stages of pipeline in field-programmable gate array (FPGA) are developed to recognize the targets in both left and right image planes and to give each target a unique label. The pipeline architecture includes a smoothing filter, an adaptive threshold module, a connected component labeling operation, and a centroid extraction process. A parallel distortion correction method is proposed and implemented in a dual-core DSP. A suitable kinematic model is established for the moving targets, and a novel set of parallel and interactive computation mechanisms is proposed to position and track the targets, which are carried out by a cross-computation method in a dual-core DSP. The proposed tracking system can track the 3-D coordinate, velocity, and acceleration of four infrared markers with a delay of 9.18 ms. Furthermore, it is capable of tracking a maximum of 110 infrared markers without frame dropping at a frame rate of 60 f/s. The accuracy of the proposed system can reach the scale of 0.37 mm RMS along the x- and y-directions and 0.45 mm RMS along the depth direction (the depth is from 0.8 to 0.45 m). The performance of the proposed system can meet the requirements of applications such as surgical navigation, which needs high real time and accuracy capability.

Study on the technology of thermal cracking of paraffin to alpha olefins

Alpha olefins are mainly produced from paraffin cracking in China, but their quality is not good because of bad quality of cracking feed and outdated technology. The technology of paraffin once-through cracking, paraffin recycle cracking of removing the heavy fraction after wax vaporizing and that of removing the heavy fraction before wax vaporizing were investigated in this paper. It was found that the technology of paraffin recycle cracking of removing the heavy fraction before wax vaporizing is new and better under the same operating conditions. Using hard paraffin (mp 54-56 degrees C) as feed, the high-quality alpha olefins products (C-5-C-21) containing more than 97 wt% of olefins and more than 88 wt% of alpha olefins are produced under optimum process conditions, which are a steam to paraffin ratio of 15 wt%, process temperature of 600 degrees C, low hydrocarbon partial pressure and residence time of 2 s. In addition, with the technology of the second injecting steam in ethylene cracking used in paraffin cracking, producing coke in paraffin cracking furnace has been markedly reduced.