Home About us Contact
|
Home About us Contact | ||
|
|
||
Regime Transition (regime + transition)
Selected AbstractsClan Politics and Regime Transition in Central Asia by Kathleen CollinsDEVELOPMENT AND CHANGE, Issue 3 2007Lawrence P. Markowitz No abstract is available for this article. [source] Fluid Evolution and Metallogenic Dynamics during Tectonic Regime Transition: Example from the Jiapigou Gold Belt in Northeast ChinaRESOURCE GEOLOGY, Issue 2 2009Jun Deng Abstract The Jiapigou gold belt, one of the most important gold-producing districts in China, is located in the northern margin of the North China Craton (NCC). The tectonic evolution of the gold belt is closely related to the Siberian Plate (SP) in the north, Yangtze Craton (YC) in the south and Pacific Plate in the east. In order to investigate the nature of the tectono-fluid-metallogenic system, the authors investigated the relationships among the tectonic regimes, fluid evolution and metallogenesis. This paper examined the corresponding spatial,temporal relationship between the ore-controlling tectonic regime and hydrothermal fluid evolution in the Jiapigou gold belt. There are two types of gold mineralization: disseminated ores that are distributed within the NW-trending main ductile shear zone and gold-bearing quartz veins and minor disseminated ores that are distant to the ductile shear zone. The fluid inclusions in quartz contain a large amount of CO2. Metamorphic fluids of middle to high temperatures and pressures and meteoric waters of low temperatures and pressures mixed together during mineralization. A proposed ore-forming model is as follows: in the pre-ore phase, the collision of SP and NCC resulted in the NS-trending compression of the ore belt. This formed the NE-trending and NW-trending shear faults and EW-trending folds. During the ore-forming phase, the collision of YC and NCC resulted in dextral shearing of the NW-trending Jiapigou fault and the NE-trending Green faults. High-pressure fluids caused by the compression flowed into the dilatant zone. This may have caused both phase separation of CO2 -bearing fluids and the mixing of meteoric waters, metamorphic waters and magmatic source fluids and finally resulted in the disequilibrium of the ore fluids and precipitation of ore minerals. [source] Studies on Regime Transition, Operating Range and System Stability in a Liquid-Solid Circulating Fluidized BedCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2009P. Natarajan Abstract In the present work, the variations in the solids circulation rate and solids holdup were analyzed to study the behavior of a liquid-solid circulating fluidized-bed (LSCFB) regime. The results confirm the existence of two regions in the regime of LSCFB. A new concept of critical liquid velocity, jlc, is proposed in the present work for demarcation between region,1 and region,2, which is found to be a constant value of about 1.3,ut for all particles considered. The operating range of the LSCFB regime is obtained for the various particles and a correlation is developed from the data to estimate the maximum total liquid velocity. The predicted maximum liquid velocity was compared with the experimental values and found to be in good agreement within ±9,%. The effects of total liquid velocity, particle size and density on the stable operating range are discussed. Analysis of the experimental results shows that stable operation prevails both in region,1 and region,2. [source] Inter-decadal variation of the summer precipitation in East China and its association with decreasing Asian summer monsoon.INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2008Part I: Observed evidences Abstract In recent two decades, North and Northeast China have suffered from severe and persistent droughts while the Yangtze River basin and South China have undergone much more significant heavy rainfall/floods events. This long-term change in the summer precipitation and associated large-scale monsoon circulation features have been examined by using the new dataset of 740 surface stations for recent 54 years (1951,2004) and about 123-yr (1880,2002) records of precipitation in East China. The following new findings have been highlighted: (1) One dominating mode of the inter-decadal variability of the summer precipitation in China is the near-80-yr oscillation. Other modes of 12-yr and 30,40-yr oscillations also play an important role in affecting regional inter-decadal variability. (2) In recent 54 years, the spatial pattern of the inter-decadal variability of summer precipitation in China is mainly structured with two meridional modes: the dipole pattern and the positive-negative-positive ("+ , + " pattern). In this period, a regime transition of meridional precipitation mode from "+ , + " pattern to dipole pattern has been completed. In the process of southward movement of much precipitation zone, two abrupt climate changing points that occurred in 1978 and 1992, respectively, were identified. (3) Accompanying the afore-described precipitation changes, the East Asian summer monsoon have experienced significant weakening, with northward moisture transport and convergence by the East Asian summer monsoon greatly weakened, thus leading to much deficient moisture supply for precipitation in North China. (4) The significant weakening of the component of the tropical upper-level easterly jet (TEJ) has made a dominating contribution to the weakening of the Asian summer monsoon system. The cooling in the high troposphere at mid- and high latitudes and the possible warming at low latitude in the Asian region is likely to be responsible for the inter-decadal weakening of the TEJ. Copyright © 2007 Royal Meteorological Society [source] Characterization of flow regime transition and particle motion using acoustic emission measurement in a gas-solid fluidized bedAICHE JOURNAL, Issue 5 2010Wang Jingdai Abstract Particle motion is a major determinant of the dynamical performance of a fluidized bed. It plays an important role in determining and optimizing the complex correlation of fluidization condition between particle-particle and particle-environment in a system. A passive acoustic emission (AE) technique is applied to monitor, characterize, and control the fluidization condition of polyethylene particles in a gas-solid fluidized bed. Experimental results show that AE signals are very sensitive to the particle movements by analyzing energy distribution, which can help to understand the status of the system. The AE energy temporal analysis is further used to identify the transition of flow regimes. Moreover, the activity of particle motion can be quantitatively determined by using a combination of granular temperature and AE spatial energy analysis. This work provides valuable insights into the dynamic behavior of particles in a gas-solid fluidized bed based on AE technique. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Influence of elevated pressure and particle lyophobicity on hydrodynamics and gas,liquid mass transfer in slurry bubble columnsAICHE JOURNAL, Issue 3 2010Vinit P. Chilekar Abstract This article reports on the influence of elevated pressure and catalyst particle lyophobicity at particle concentrations up to 3 vol % on the hydrodynamics and the gas-to-liquid mass transfer in a slurry bubble column. The study was done with demineralized water (aqueous phase) and Isopar-M oil (organic phase) slurries in a 0.15 m internal diameter bubble column operated at pressures ranging from 0.1 to 1.3 MPa. The overall gas hold-up, the flow regime transition point, the average large bubble diameter, and the centerline liquid velocity were measured along with the gas,liquid mass transfer coefficient. The gas hold-up and the flow regime transition point are not influenced by the presence of lyophilic particles. Lyophobic particles shift the regime transition to a higher gas velocity and cause foam formation. Increasing operating pressure significantly increases the gas hold-up and the regime transition velocity, irrespective of the particle lyophobicity. The gas,liquid mass transfer coefficient is proportional to the gas hold-up for all investigated slurries and is not affected by the particle lyophobicity, the particle concentration, and the operating pressure. A correlation is presented to estimate the gas,liquid mass transfer coefficient as a function of the measured gas hold-up: . © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Detecting regime transitions in slurry bubble columns using pressure time seriesAICHE JOURNAL, Issue 7 2005Keshav C. Ruthiya Abstract Changes in the coherent standard deviation and in the average frequency of measured pressure time series with gas velocity, are proposed, as unique and unambiguous criteria to mark flow regime transitions in slurry bubble columns. In a 2-dimensional (2-D) slurry bubble column, pressure time series are measured at different gas velocities simultaneously with high-speed video recording of the gas-liquid flow. The frequency of occurrence and the average diameter of the large bubbles are determined from video image analysis. The gas velocity where the first large bubbles are detected, with an average diameter of 1.5 cm, and with a frequency of occurrence of one bubble per s, is designated as the first regime transition point (transition from the homogeneous regime to the transition regime). At this point, the coherent standard deviation of the measured pressure fluctuations clearly increases from zero. The gas velocity where the average diameter and the frequency of occurrence of the large bubbles become constant, is designated as the second regime transition point (transition from the transition regime to the heterogeneous regime). From this point onward, the slope of the coherent standard deviation of the measured pressure fluctuations clearly decreases with gas velocity, while the average frequency becomes constant. These clear changes with gas velocity in the coherent standard deviation, and in the average frequency are also demonstrated in a 3-D slurry bubble column. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Liberal and Illiberal Democracy in Latin AmericaLATIN AMERICAN POLITICS AND SOCIETY, Issue 1 2008Peter H. Smith ABSTRACT This article examines the incidence of liberal and "illiberal" democracy in Latin America from 1978 through 2004. It demonstrates, first, that illiberal democracy,which combines free and fair elections with systematic constraints on citizens'rights,became the norm throughout the region. Second, it shows that regime transitions most often ended not in liberal democracy but in illiberal democracy. Third, rare events logit analysis reveals that two variables, hyperinflation and presidential elections, had significant impact on movement toward fuller democracy. As a form of short-term economic shock, hyperinflation generates widespread discontent; given the opportunity to vote, citizens elect reformist opposition candidates who, once in office, remove controls on civil liberties. This scenario substantially increases the likelihood of transition from illiberal to liberal democracy. [source] | ||||||||||||||||