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Pressure Wave and Fluid Velocity in a Bend-Mode Inkjet Nozzle with Double PZT Actuators

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Journal of Thermal Science 2013年第1期22卷 29-35页

作者： Sungu Kim Jaeyong Sung Myeong Ho Lee Graduate School Dept.of Mechanical EngineeringSeoulTech dept.of Mechanical and Automotive Engineering SeoulTech

A new concept of bend-mode inkjet nozzle with double PZT (lead zirconate titanate) actuators has been designed and fabricated in the present study. Then the pressure wave and fluid velocity at the nozzle exit have been investigated. The complex pressure behavior inside the channel was solved numerically based on the narrow channel acoustic theory. The two PZTs attached to a rectangular channel were actuated sequentially by setting the waveforms of each PZT to be center-aligned with various pulse widths. As a result, the double PZT actuation is superior to the single PZT actuation in view of strong momentum force and fast dissipation of residual pressure. The maximum fluid velocity at the nozzle exit is observed when the respective pulse widths equal to their optimum pulse widths. The numerical results are supported by the experimental results with the fabricated inkjet device by measuring the speed of meniscus just out of the nozzle.

关键词： double PZT actuators inkjet nozzle narrow channel theory pressure wave sequential actuation

Persisting challenges for performance-based building assessment

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Earthquake Engineering and Engineering Vibration 2014年第S1期13卷 79-94页

作者： B.Bayhan I.Kazaz P.Gulkan dept.of Civil Engineering Bursa Technical University Assistant Professor dept.of Civil Engineering Erzurum Technical University Associate Professor dept.of Civil Engineering Cankaya University Professor

Intense research and refinement of the tools used in performance-based seismic engineering have been made,but the maturity and accuracy of these methods have not been adequately confirmed with actual data from the field. The gap between the assumed characteristics of actual building systems and their idealized counterparts used for analysis is wide. When the randomly distributed flaws in buildings as they exist in urban areas and the extreme variability of ground motion patterns combine,the conventional procedures used for pushover or dynamic response history analyses seem to fall short of reconciling the differences between calculated and observed damage. For emergency planning and loss modeling purposes,such discrepancies are factors that must be borne in mind. Two relevant examples are provided herein. These examples demonstrate that consensus-based analytical guidelines also require well-idealized building models that do not lend themselves to reasonably manageable representations from field data. As a corollary,loss modeling techniques,e.g.,used for insurance purposes,must undergo further development and improvement.

关键词： reinforced concrete building nonlinear analysis performance-based seismic assessment performance limits damage

Paederia foetida- a promising ethno-medicinal tribal plant of northeastern India

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Journal of Forestry Research 2013年第4期24卷 801-808页

作者： Silpi Chandadept.of Pharmacy Jaypee University of Information Technology Indira P Sarethy Biplab De Kuldeep Singh dept.of Biotechnology Jaypee Institute of Information Technology dept.of Pharmaceutical Science Assam University dept.of Pharmacy Jaypee University of Information Technology

The northeastern region of India constitutes one of the biodi- versity hotspots of the world. The ethnic groups inhabiting this region practice their distinctive traditional knowledge systems using biodiver- sity for food, shelter and healthcare. Among the less-studied plants, Paederia foetida has been used by various ethnic tribes as food and medicine. Many of its therapeutic properties relate to the gastrointestinal system and suggest its potential utility for gastrointestinal ailments. This is a review of the ethnobotanical uses, phytochemistry and therapeutic properties of P. foetida compiled from various reports. P. foetida is promising as a remedy for life-style related conditions, especially treat- ment of ulcers. Its utility highlights the need for proper evaluation of tribal plants as medicines and the species could be considered for devel- opment of new drugs.

关键词： Paederia foetida Tribal medicine ethnobotany phyto-chemistry therapeutic ulcer

Influence of Surface Treatment on the Corrosion Resistance of Stainless Steel in Simulated Human Body Environment

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Journal of Materials Science & Technology 2009年第5期25卷 611-614页

作者： Esmaeil Jafari Mohammad Jafar Hadianfard dept.of Materials Science and Engineering

In the present research, the influence of chromium enrichment by surface treatment on corrosion resistance of type 316L stainless steel in body environment was investigated. For this study, weight loss test during 18 months, cyclic and liner polarization tests before and after surface treatment and metallography by electron and light microscopy were used to evaluate the effectiveness of the proposed method. In addition, X-ray photoelectron spectroscopy （XPS） method was used to determine the chromium concentration in the surface layer after surface treatment. Results show that the surface treatment has improved corrosion resistance of the type 316L stainless steel in body environment.

关键词： Surface treatment Corrosion Passive film Polarization resistance

Analysis of Viscous Heating in a Micro-Rocket Flow and Performance

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Journal of Thermal Science 2008年第2期17卷 116-124页

作者： José A.Moríigo José Hermida Quesada dept.of Space Programmes National Institute for Aerospace Technology dept.of Aerodynamics and Propulsion National Institute for Aerospace Technology

Micro-rockets for propulsion of small spacecrafts exhibit significant differences with regard to their macroscale counterparts,mainly caused by the role of the viscous dissipation and heat transfer processes in the micron-sized *** goal of this work is to simulate the transient operation of a micro-rocket to investigate the effects of viscous heating on the flow and performance for four configurations of the expanding gas and wafer *** modelling follows a multiphysics approach that solves the fluid and solid regions fully coupled.A contin- uum-based description that incorporates the effects of gas rarefaction through the micro-nozzle,viscous dissipa- tion and heat transfer at the solid-gas interface is ***-equilibrium is addressed with the implementa- tion of a 2nd-order slip-model for the velocity and temperature at the *** results stress that solid-fluid cou- pling exerts a strong influence on the flowfield and performance as well as the effect of the wafer during the first instants of the transient in micro-rockets made of low and high thermal conductivity materials.

关键词： Micronozzles propulsion MEMS slip flow viscous heating

Brillouin expanded time-domain analysis based on dual optical frequency combs

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Light(Science & Applications) 2024年第8期13卷 1534-1544页

作者： Jae Hyeong Youn Kwang Yong Song Sonia Martin-Lopez Miguel Gonzalez-Herraez María R.Fernández-Ruiz dept.of Physics Chung-Ang UniversitySeoulKorea dept.of Electronics Universidad de AlcaláMadridSpain

Brillouin Optical Time-Domain Analysis(BOTDA)is a widely-used distributed optical fiber sensing technology employing pulse-modulated pump waves for local information retrieval of the Brillouin gain or loss *** spatial resolution of BOTDA systems is intrinsically linked to pulse duration,so high-resolution measurements demand high electronic bandwidths inversely proportional to the *** paper introduces Brillouin Expanded Time-Domain Analysis(BETDA)as a modified BOTDA system,simultaneously achieving high spatial resolution and low detection *** two optical frequency combs(OFCs)with different frequency intervals as pump and probe,local Brillouin gain spectra are recorded by their spectral beating traces in an expanded time domain.A 2-cm-long hotspot located in a 230m single-mode fiber is successfully measured in the time domain with a detection bandwidth of less than 100 kHz using dual OFCs with tailored spectral phase,line spacing,and bandwidth.

关键词： pump optical fiber

Output only modal identification and structural damage detection using time frequency & wavelet techniques

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Earthquake Engineering and Engineering Vibration 2009年第4期8卷 583-605页

作者： S.Nagarajaiah B.Basu dept.of Civil & Environmental Eng.and dept.of Mechanical Eng.& Material Sc. Rice University dept.of Civil Structural& Environmental Eng.Trinity College Dublin

The primary objective of this paper is to develop output only modal identification and structural damage detection. Identification of multi-degree of freedom （MDOF） linear time invariant （LTI） and linear time variant （LTV--due to damage） systems based on Time-frequency （TF） techniques--such as short-time Fourier transform （STFT）, empirical mode decomposition （EMD）, and wavelets--is proposed. STFT, EMD, and wavelet methods developed to date are reviewed in detail. In addition a Hilbert transform （HT） approach to determine frequency and damping is also presented. In this paper, STFT, EMD, HT and wavelet techniques are developed for decomposition of free vibration response of MDOF systems into their modal components. Once the modal components are obtained, each one is processed using Hilbert transform to obtain the modal frequency and damping ratios. In addition, the ratio of modal components at different degrees of freedom facilitate determination of mode shape. In cases with output only modal identification using ambient/random response, the random decrement technique is used to obtain free vibration response. The advantage of TF techniques is that they arc signal based; hence, can be used for output only modal identification. A three degree of freedom 1：10 scale model test structure is used to validate the proposed output only modal identification techniques based on STFT, EMD, HT, wavelets. Both measured free vibration and forced vibration （white noise） response are considered. The secondary objective of this paper is to show the relative ease with which the TF techniques can be used for modal identification and their potential for real world applications where output only identification is essential. Recorded ambient vibration data processed using techniques such as the random decrement technique can be used to obtain the free vibration response, so that further processing using TF based modal identification can be performed.

关键词： Time-frequency methods short time Fourier transform Hilbert transform wavelets modal identification:output only structural health monitoring damage detection

Understanding the Mechanism of Nanoparticle Formation in a Wire Explosion Process by Adopting the Optical Emission Technique

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Plasma Science and Technology 2013年第6期15卷 562-569页

作者： B.DEBALINA M.KAMARAJ S.R.CHAKRAVARTHI N.J.VASA R.SARATHI dept.of Metallurgical and Materials Engg. IIT MadrasChennai 600036India dept.of Aerospace Engg. IIT MadrasChennai 600036India dept.of Engineering Design IIT MadrasChennai 600036India dept.of Electrical Engg. IIT MadrasChennai 600036India

In the present study nano-tungsten carbide particles were generated in a wire explosion *** plasma generated during the wire explosion process was analyzed using optical emission spectroscopy（OES）.The impact of ambient pressure on the plasma temperature,electron density and plasma lifetime was *** variations of the plasma produced under different experimental conditions were *** produced nanoparticles were characterized through wide angle X-ray diffraction（WAXD） and transmission electron microscopy（TEM） studies. Particles produced with a negative DC charging voltage had a larger mean size when compared to a positive charging *** dependence on the plasma duration was observed where plasma was sustained for a longer duration with a negative DC charging voltage.

关键词： optical emission wire explosion tungsten carbide life time nano particle

AN INVESTIGATION OF THE RELATION BETWEEN COTTON FIBRE PROPERTIES AND YARN QUALITY BY USING HIGH VOLUME INSTRUMENT(HVI)SYSTEM

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Journal of China Textile University(English Edition) 1993年第2期10卷 7-13页

作者： M.A.Zaman 储才元严灏景 dept.of Textile Engineering

The objective of this paper is to establish reliable prediction equations relating cotton fibreproperties measured by HVI system and yarn quality,A useful statistical method is adopted for de-veloping a multiple regression model interpreting the relation between the data of Spinlab HVIfibre properties and quality parameters of yarn STQ (Strength Tex Quotient).The percent relativecontribution of a fibre property with respect of STQ is also *** results show that the totalcontribution of the HVI measured fibre properties can account for 77.4% of known variation ofyarn *** main feature of the approach is its flexibility in accommodating all fibre *** examination of regression equation showed that it could be well applied to predict STQ ofyarns spun from the same spinning system,but,for different spinning systems and also for yarns ofdifferent linear density,modification of the equation would be needed.

关键词： regression analysis correlations cotton fibres fibre properties cotton yarn yarn properties ring spinning High Volume Instrument