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- 저자 : Griffiths J. (검색결과 24 건)
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오세화,박수열,Griffiths, J. 한국공업화학회 2001 응용화학 Vol.5 No.2
The majority of dyes belong to the chromophoric class known as donor-acceptor systems, the essential structural feature of such systems being the presence of one or more electron donating groups conjugated to one or more electron withdrawing groups via an unsaturated bridge. Visible light absorption is then associated with the migration of electron density from the donor region of the molecule to the acceptor region. H-Chromophores is a special type of donor-acceptor system, and can be regarded as made up of two cross-conjugated donor-acceptor systems sharing a common conjugating bridge. Several new H-chromophore systems were synthesised with a view to examining there colour properties, pH sensitivity and redox behaviour. This could be reversed by air-oxidised, suggesting that these chromophores could be useful as colour formers.
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Change in mean temperature as a predictor of extreme temperature change in the Asia–Pacific region
Griffiths, G. M.,Chambers, L. E.,Haylock, M. R.,Manton, M. J.,Nicholls, N.,Baek, H.-J.,Choi, Y.,Della-Marta, P. M.,Gosai, A.,Iga, N.,Lata, R.,Laurent, V.,Maitrepierre, L.,Nakamigawa, H.,Ouprasitwong, John Wiley Sons, Ltd. 2005 International journal of climatology Vol.25 No.10
<P>Trends (1961–2003) in daily maximum and minimum temperatures, extremes and variance were found to be spatially coherent across the Asia–Pacific region. The majority of stations exhibited significant trends: increases in mean maximum and mean minimum temperature, decreases in cold nights and cool days, and increases in warm nights. No station showed a significant increase in cold days or cold nights, but a few sites showed significant decreases in hot days and warm nights. Significant decreases were observed in both maximum and minimum temperature standard deviation in China, Korea and some stations in Japan (probably reflecting urbanization effects), but also for some Thailand and coastal Australian sites. The South Pacific convergence zone (SPCZ) region between Fiji and the Solomon Islands showed a significant increase in maximum temperature variability.</P><P>Correlations between mean temperature and the frequency of extreme temperatures were strongest in the tropical Pacific Ocean from French Polynesia to Papua New Guinea, Malaysia, the Philippines, Thailand and southern Japan. Correlations were weaker at continental or higher latitude locations, which may partly reflect urbanization.</P><P>For non-urban stations, the dominant distribution change for both maximum and minimum temperature involved a change in the mean, impacting on one or both extremes, with no change in standard deviation. This occurred from French Polynesia to Papua New Guinea (except for maximum temperature changes near the SPCZ), in Malaysia, the Philippines, and several outlying Japanese islands. For urbanized stations the dominant change was a change in the mean and variance, impacting on one or both extremes. This result was particularly evident for minimum temperature.</P><P>The results presented here, for non-urban tropical and maritime locations in the Asia–Pacific region, support the hypothesis that changes in mean temperature may be used to predict changes in extreme temperatures. At urbanized or higher latitude locations, changes in variance should be incorporated. Copyright © 2005 Royal Meteorological Society.</P>
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Galloping analysis of stranded electricity conductors in skew winds
J. H. G. Macdonald,P. J. Griffiths,B. P. Curry 한국풍공학회 2008 Wind and Structures, An International Journal (WAS Vol.11 No.4
When first commissioned, the 1.6 km span 275kV Severn Crossing Conductor experienced large amplitude vibrations in certain wind conditions, but without ice or rain, leading to flashover between the conductor phases. Wind tunnel tests undertaken at the time identified a major factor was the lift generated in the critical Reynolds number range in skew winds. Despite this insight, and although a practical solution was found by wrapping the cable to change the aerodynamic profile, there remained some uncertainty as to the detailed excitation mechanism. Recent work to address the problem of dry inclined cable galloping on cablestayed bridges has led to a generalised quasi-steady galloping formulation, including effects of the 3D geometry and changes in the static force coefficients in the critical Reynolds number range. This generalised formulation has been applied to the case of the Severn Crossing Conductor, using data of the static drag and lift coefficients on a section of the stranded cable, from the original wind tunnel tests. Time history analysis has then been used to calculate the amplitudes of steady state vibrations for comparison with the full scale observations. Good agreement has been obtained between the analysis and the site observations, giving increased confidence in the applicability of the generalised galloping formulation and providing insight into the mechanism of galloping of yawed and stranded cables. Application to other cable geometries is also discussed.
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Galloping analysis of stranded electricity conductors in skew winds
Macdonald, J.H.G.,Griffiths, P.J.,Curry, B.P. Techno-Press 2008 Wind and Structures, An International Journal (WAS Vol.11 No.4
When first commissioned, the 1.6 km span 275kV Severn Crossing Conductor experienced large amplitude vibrations in certain wind conditions, but without ice or rain, leading to flashover between the conductor phases. Wind tunnel tests undertaken at the time identified a major factor was the lift generated in the critical Reynolds number range in skew winds. Despite this insight, and although a practical solution was found by wrapping the cable to change the aerodynamic profile, there remained some uncertainty as to the detailed excitation mechanism. Recent work to address the problem of dry inclined cable galloping on cable-stayed bridges has led to a generalised quasi-steady galloping formulation, including effects of the 3D geometry and changes in the static force coefficients in the critical Reynolds number range. This generalised formulation has been applied to the case of the Severn Crossing Conductor, using data of the static drag and lift coefficients on a section of the stranded cable, from the original wind tunnel tests. Time history analysis has then been used to calculate the amplitudes of steady state vibrations for comparison with the full scale observations. Good agreement has been obtained between the analysis and the site observations, giving increased confidence in the applicability of the generalised galloping formulation and providing insight into the mechanism of galloping of yawed and stranded cables. Application to other cable geometries is also discussed.
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Stabilization of single-electron pumps by high magnetic fields
Fletcher, J. D.,Kataoka, M.,Giblin, S. P.,Park, Sunghun,Sim, H.-S.,See, P.,Ritchie, D. A.,Griffiths, J. P.,Jones, G. A. C.,Beere, H. E.,Janssen, T. J. B. M. American Physical Society 2012 Physical review. B, Condensed matter and materials Vol.86 No.15
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The Synthesis and Visible Absorption Properties of Squaryliums
박수열,오세화,( J. Griffiths ) 한국공업화학회 2001 한국공업화학회 연구논문 초록집 Vol.2001 No.-
The near-infrared, i.e. beyond about 700 nm, have been a increase in interest in recent years. In past time they are understandable, since light absorption beyond 750 nm is undetectable by the eye and makes no contribution to the observed colour. However now such dyes find use in high technology application, i.e. lasers, laser addressed liquid crystal display, optical data storage, optical filters and many other electro-optical application. Particularly, the squarylium compounds based on donor-acceptor chromophores were investigated and the visible absorption spectroscopic properties of the various squaryliums were examined for the near-infrared region. Also, our results show that squaryliums colud be possible to be producing near-infrared absorbing materials with a view to investigate colour and their constitution relationships which show narrower, more intense bands than other materials, especially, methine dyes such as azo and azamethine typed compounds in visible absorption regions.
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Yi-Xiáng J Wáng,James F Griffith,Min Deng,David KW Yeung,Jing Yuan 대한영상의학회 2015 Korean Journal of Radiology Vol.16 No.1
Bilateral oophorectomy leads to reduced bone mineral density (BMD), and reduced BMD is associated with increased marrow fat and reduced marrow perfusion. Purpose of this study was to investigate how soon these changes occur following surgical oophorectomy. Six patients who underwent hysterectomy and bilateral salpingo-oophorectomy were studied. At baseline, mean patient age was 49.5 years (range: 45–54 years). Third lumbar vertebral body BMD measurement using quantitative CT, marrow fat fraction (FF) using MR spectroscopy and marrow perfusion using dynamic contrast enhanced MRI were conducted immediately prior to surgery and at 3, 9, and 21 months after surgery. Reduced BMD, increased marrow FF, and reduced marrow perfusion occurred synchronously post-oophorectomy. There was a sharp decrease of 12.5 ± 7.2% in BMD (n = 6), a sharp increase of 92.2 ± 46.3% (n = 6) in FF, a sharp decrease of 23.6 ± 3.9% in maximum contrast enhancement (n = 5), and of 45.4 ± 7.7% for enhancement slope (n = 5) during the initial 3 months post surgery. BMD and marrow perfusion continued to decrease, and marrow FF continued to increase at a slower rate during the following 18 months. Friedman test showed a significant trend for these changes (p < 0.05). Bilateral oophorectomy leads to a rapid decrease in lumbar BMD, an increase in marrow fat content, and a decrease in marrow blood perfusion.
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Syntheses of Symmetric Hetero typed Squarylium Dyes
박수열,오세화,박희문,( J. Griffiths ) 한국공업화학회 2001 한국공업화학회 연구논문 초록집 Vol.2001 No.-
The many squaryliums of organic class have received a great deal of attention in recent years due to the potential applications of these materials in many fields such as electrophotographic processes, photovoltaic cells and in diode-laser optical storage recording system. Therefore, by suitable choice of terminal amino residues in the 1,3-squaryliums it is possible to displace the absorption band into the near-infrared regions. In this section, the visible absorption properties of the heterocyclic squaryliums were studied and their colour change phenomena were considered. As a these results it was designed that heterocyclic squarylium dyes could be probably suitable indicators for both titrimetric and colourimetric purposes. Interestingly, Some squarylium dyes are used for semi-permanent hair dyes due to low molecule weight, soluble in water and high affinity on hair with polar structure.
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