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Search Results: 1 - 10 of 4743 matches for " Zhaoyong Guan "
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Graphene/g-C2N bilayer:gap opening, enhanced visible light response and electrical field tuning band structure
Zhaoyong Guan,Jia Li,Wenhui Duan
Physics , 2015,
Abstract: Opening up a band gap of the graphene and finding a suitable substrate are two challenges for constituting the nano-electronic equipment. A new two-dimensional layered crystal g-C2N (Nat. Commun. 2015, 6, 1–7) with novel electronic and optical properties can be effectively synthesized via a wet-chemical reaction. And g-C2N can be used as a suitable substrate to open the band gap of graphene as much as 0.239 eV, which is large enough for the band gap opening at room temperature. The physics behind the band gap opening is that g-C2N substrate can produce the inhomogeneous electrostatic potential over the graphene layer. The imposition of external electrical field can tune the band gap of the hybrid of graphene/g-C2N effectively from the semiconductors to the metal. The hybrid graphene/g-C2N displays an enhanced optical activity compared with the pure g-C2N monolayer.
The seasonal cycle of interhemispheric oscillations in mass field of the global atmosphere
ChuHan Lu,ZhaoYong Guan,ShiLong Mei,YuJing Qin
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0316-3
Abstract: Using the daily and monthly data of surface air pressure, meridional wind, radiation and water vapor from NCEP/NCAR reanalysis for the period of 1979–2006, we have examined the seasonal variations of the interhemispheric oscillations (IHO) in mass field of the global atmosphere. Our results have demonstrated that IHO as observed in surface air pressure field shows the distinct seasonal cycle. This seasonal cycle has an interhemispheric seesaw structure with comparable annual ranges of surface air pressure in the Southern and Northern Hemispheres. Mass of water vapor changes out-of-phase between the Southern and Northern Hemispheres, showing clearly a seasonal cycle with its annual range almost equivalent to annual range of the IHO seasonal cycle. Amazingly, the cross-equatorial flow is found to be induced by annual changes in water vapor mass as a response of the atmosphere to seasonal cycle of forcing from hemispheric net surface short-and long-wave radiations. The IHO seasonality exhibits its larger variations in magnitude in mid-latitudes other than in other regions of the globe. Additionally, our results also show that the global air mass is redistributed seasonally not only between the Northern and Southern Hemispheres but also between land and sea. This land-sea air mass redistribution induces a zonal pattern of surface air pressure in the Northern Hemisphere but the meridional pattern in the Southern Hemisphere.
Comparison of the Hadley cells calculated from two reanalysis data sets
Yujing Qin,Panxing Wang,Zhaoyong Guan,Yang Yue
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2030-3
Abstract: The mass stream function of mean meridional circulation is calculated from the ECMWF and NCEP/NCAR reanalysis data sets using a superposition computation scheme. The comparison of results shows that the common ascending leg of the Hadley cell calculated from the ECMWF data is strong and narrow, and averagely lies more north of the equator in comparison with its counterpart from the NCEP/NCAR data, and furthermore the Hadley cell from the ECMWF data shows an obvious double-layer structure. Therefore, there are obvious differences between Hadley cells displayed by the two objective analysis data sets.
Seasonality of Interannual Inter-hemispheric Oscillations over the Past Five Decades

GUAN Zhaoyong,LU Chuhan,MEI Shilong,CONG Jing,

大气科学进展 , 2010,
Abstract: Air mass is inter-hemispherically redistributed, leading to an interesting phenomenon known as the Inter-Hemispheric Oscillation (IHO). In the present article, the seasonality of the interannual IHO has been examined by employing monthly mean reanalyses from NCEP/NCAR, EAR40, and JRA25 for the period of 1958--2006. It is found that the IHO indices as calculated from different reanalyses are generally consistent with each other. A distinct seesaw structure in all four seasons between the northern and southern hemispheres is observed as the IHO signature in both the surface air pressure anomalies (SAPAs) and the leading EOF component of the anomalous zonal mean quantities. When the SAPAs are positive (negative) in the northern hemisphere, they are negative (positive) in the southern hemisphere. Large values of SAPAs are usually observed in mid- and high-latitude areas in all but the solstice seasons. In boreal summer and winter, relatively stronger perturbations of IHO-related SAPA are found in the Asian monsoon region, which shows a large difference from the status in boreal spring and fall. This suggests that seasonal mean monsoon activity is globally linked via air mass redistribution globally on interannual timescales, showing a very interesting linkage between monsoons and the IHO in the global domain. In all seasons, large values of SAPA always exist over the Antarctic and the surrounding regions, implying a close relation with Antarctic oscillations.
中国东南部与川渝陕甘地区夏季降水30~60天CISO的反相现象
焦敏 Jiao Min,管兆勇 Guan Zhaoyong
大气科学 , 2014, DOI: 10.3878/j.issn.1006-9895.2013.12116
Abstract: 利用1979~2010年NCEP/NCAR逐日再分析资料和我国753站逐日降水资料,研究了中国东南部和川渝陕甘地区夏季降水30~60天气候季节内振荡(ClimatologicalIntraSeasonalOscillation,CISO)的反相现象。结果显示两个区域夏季降水CISO在7月中旬之前存在显著的反相关系,且在传播特征上有明显差异。川渝陕甘地区降水局地低频振荡显著,中国东南部降水CISO北传特征清晰。低频环流分析表明,对流层低层低频槽、脊的更替形成了川渝陕甘地区降水CISO的“驻相”振荡,低频气旋式、反气旋式环流位置的移动则产生了中国东南部降水CISO的北传。CISO垂直环流显示上升支与下沉支正好处于川渝陕甘地区与中国东南部,较好地反映了低频降水在两区域的相反变化。中国东南部、长江中下游与川渝陕甘地区三者之间存在动力学上的关联,这可部分地解释川渝陕甘地区和中国东南部之间降水CISO的反相关系。这种反相关系的形成还与气候态下的西太平洋副热带高压和贝加尔湖附近大陆高压脊的季节内变化有关。揭示中国东南部与川渝陕甘地区之间降水CISO的反相现象对于丰富人们对我国夏季风区低频振荡局地特征的认识和理解降水季节内振荡产生机制有重要意义。
对流层上层斜压波包活动与2003年江淮流域梅雨的关系
梅士龙 Mei Shilong,管兆勇 Guan Zhaoyong
大气科学 , 2008, DOI: 10.3878/j.issn.1006-9895.2008.06.08
Abstract: 利用NCEP/NCAR再分析和中国740站逐日降水资料,研究了2003年淮河流域梅雨期间对流层上层斜压波动的传播情况。结果发现,斜压波组织成波包向下游传播且具有明显的下游频散效应。波动起源于巴尔喀什湖西北侧,沿着西北-东南向的路径向东南传播,传至江淮流域大约需要3天。斜压波包所带来的扰动能量为江淮流域暴雨的发生发展提供了必要的能量积聚。通过与1998和1997年这两个梅雨年份的比较,发现1998年异常强梅雨年的斜压波包的活动特征与2003年的相似,但在梅雨降水非常偏少的1997年,未发现有明显的斜压波包向下游的传播。
江淮流域夏季降水异常与西北太平洋副热带30~60天振荡强度年际变化的联系
贾燕 JIA Yan,管兆勇 GUAN Zhaoyong
大气科学 , 2010, DOI: 10.3878/j.issn.1006-9895.2010.04.03
Abstract: 利用1978~2007年NCEP/NCAR再分析资料和地面观测站降水资料,研究了夏季江淮流域降水多寡与30~60天振荡(ISO)强度年际变化的联系。结果表明:江淮流域夏季降水异常与台湾海峡地区及西北太平洋低频能量变化相关显著。定义了ISO强度指数,对ISO强度指数高低年夏季低频降水以及低频环流的位相合成表明:高指数年主要通过存在于南海—西北太平洋地区的低频气旋、反气旋系统的交替活动来影响副热带高压的进退,从而引起江淮流域夏季降水异常;低指数年江淮流域夏季降水主要受西太平洋副热带高压位置及强度变化的影响,降水异常区主要位于江南地区。进一步研究表明,非30~60天低频降水扰动与低频振荡强度也有很好的相关。低频环流对双周以及天气时间尺度环流变化可能存在调制作用,这种作用对江淮流域夏季降水的年际异常起到非常重要的作用。
时间平均流场对风场振动的优势选择作用
管兆勇 Guan Zhaoyong,黄士松 Huang Shisong
大气科学 , 1994, DOI: 10.3878/j.issn.1006-9895.1994.01.12
Abstract: 本文根据谐谱展开的水平动量方程,在一定的假设下导出了集时间平均场的涡、散性质于一体的诊断关系式——大气振动频率的优势选择判据,并据此讨论了基本?场的水平不均匀对大气振动的影响。通过这个关系式,利用1982年ECM?WF资料对优势频率进行了计算,给出了对流层高、中、低各层的全球分布。?从而指出在实际大气中存在着基本场对某频率上的振动有选择放大作用。
Activities of baroclinic wave packets in the upper troposphere related to Meiyu of 2003 in the Yangtze River\|Huaihe River valley
对流层上层斜压波包活动与2003年江淮流域梅雨的关系

MEI Shilong,GUAN Zhaoyong,
梅士龙
,管兆勇

大气科学 , 2008,
Abstract: Using NCEP/NCAR reanalysis daily data from 1980 to 2003 along with 740-station precipitation data in China,the authors analyze the propagation features of the baroclinic wave packets in middle latitudes of the Northern Hemisphere during the Meiyu period of 2003.The results demonstrate that the baroclinic waves in the upper troposphere organize into the Rossby wave packets during the Meiyu period of 2003,dispersing to their downstream area distinctly.The waves originate from the regions northwest of Lake Balkhash and then spread southeastward to their downstream regions.About 3 days later,wave packets arrive in the Yangtze River-Huaihe River valley.The energy dispersion associated with baroclinic wave packets leads to the energy accumulation for rainstorms in the Yangtze River-Huaihe River valley.To further understand the downstream effect of the baroclinic wave packets,the authors compare the propagation features of the wave packets during the Meiyu periods of 1998 and 1997.It is found that the activities of baroclinic wave packets in flood Meiyu year 1998 are very similar to those in 2003.However,the downstream effect was not clearly observed in 1997 which is known as a dry Meiyu year in the Yangtze River-Huaihe River valley.
The Influence of the Time Mean Flow on the Formation of Dominant Oscillation of Wind in the Atmosphere
时间平均流场对风场振动的优势选择作用

Guan Zhaoyong,Huang Shisong,
管兆勇
,黄士松

大气科学 , 1994,
Abstract: Based on the horizontal mementum equations denoted by Fourier spectra coefficients, a relationtaking account of the vortical and divergent nature of the time mean now is obtained under certain conditions.The relation can be used to diagnose the influence of the non-uniform basic wind field on theformation of dominant oscillations of wind disturbance in the atmosphere.By using the ECMWF dayto day grid data of 1982, the frequency corresponding to the dominant oscillation in the wind field iscomputed from the relation.Thus, the global distributions of the frequencies are given at the lower,middle and upper levels in the troposphere.It is pointed out that there do exist the phenomena that thebasic wind field (time mean) could choose the oscillation with a certain frequency as the duminantoscillation in the atmosphere.
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