岩浆岩的熔点、粘度及其与化学成分的关系   总被引：4，自引：0，他引：4  

周殉若  吴国忠  朱广玲 《岩石学报》1987,3(1)

本文研究了我国中、新生代一些岩浆岩的化学成分、熔点、人工玻璃的折射率和比重以及它们在不同温度下的粘度。在常压下岩石酸度愈大,熔点愈高。熔点与岩石的Fe~(2+(+Fe~(3+)+Mn+Mg±Ca为反相关;与Si+Al+K+Na为正相关。计算粘度与温度的关系表明,酸度愈大,粘度愈大;碱度愈大,粘度愈小,温度愈高,粘度愈低;同一温差下,酸度愈大,粘度变化愈大。  相似文献   

Comparative study of the kinetics and mechanisms of dissolution of carbonate minerals   总被引：9，自引：0，他引：9  

Lei Chou  Robert M. Garrels  Roland Wollast 《Chemical Geology》1989,78(3-4):269-282

The influence of pH on the rate of dissolution of various carbonates (calcite, aragonite, witherite, magnesite and dolomite) has been investigated at 25°C using a continuous fluidized bed reactor. The general rate dependence on pH observed for the simple carbonates is very similar and is in agreement with the results observed for calcite and aragonite by L.N. Plummer and coworkers. However, the rate of dissolution of magnesite is approximately four orders of magnitude lower than calcite.

For simple carbonates, the elementary steps involved in the dissolution reaction are:

where M represents the metal ion which can be Ca, Mg and Ba. According to the stoichiometry of the three reaction steps and the thermodynamic constraints, the total forward and backward rates can be expressed as:

The rate constants (k₁, k₂, k₃ and k₋₃) determined with our experimental results for calcite, aragonite and witherite show that the dissolution rates are similar for these three minerals and that the nature of the cations does not play a significant role. The good agreement between the K_sp calculated from the measured k₃/k₋₃ ratio and the theromodynamic value suggests that our dissolution mechanism is coherent.

The rate dependence on pH of the dissolution of dolomite obeys a fractional order at low pH's and confirms previously published observations therein. However, the two-step reaction mechanism proposed does not explain the fractional reaction order observed, which is likely due to a more complex surface reaction.  相似文献   

Organic geochemical characterization of the New Albany Shale group in the Illinois Basin     

Mei-In M. Chou  Donald R. Dickerson 《Organic Geochemistry》1985,8(6):413-420

Benzene extractable aliphatic hydrocarbons from the New Albany Shale in the Illinois Basin were characterized by gas chromatography and mass spectrometry, and the total organic matter of the shale was characterized by solid state carbon-13 cross polarization magic angle spinning nuclear magnetic resonance. Core samples from a northwest-trending cross-section of the Illinois Basin were studied. Gas chromatography (GC) and gas chromatography-mass spectrometric analysis (GC/MS) data indicate a regional variation of the aliphatic composition of the shale extracts. A positive, linear relationship between the two ratios, pristane/n-C₁₇ and phytane/n-C₁₈, is indicated. The NMR results indicated that organic matter deposited in northwestern Illinois shale is relatively high in aliphatic hydrocarbon content while, in contrast, organic matter found in southeastern Illinois shale is relatively low in aliphatic hydrocarbon content. Our findings suggest that the organic variation of the shale is mainly due to the differences in thermal maturity of the shale organic matter and the use of pristane/n-C₁₇ ratio as a thermal parameter in the study of oil may be extended to the study of the ancient sediments.  相似文献   

Propagation of spiral density waves in a magneto-active disk     

Chih-Kang Chou  Pei-Long Chen 《Astrophysics and Space Science》1994,211(1):13-29

The propagation of spiral density waves in a differentially rotating, self-gravitating, magnetoactive and highly flattened disk is investigated by using the asymptotic theory for tightly wound spirals developed by Lin and his collaborators. We adopt the continuum fluid model as the primary basis, and our treatment will be largely analytical. The disk plasma is studied in the frozen field approximation and inhomogenceous magnetic fields in the plane of the disk are considered in detail.In a differentially rotating disk with strong magnetic fields, the field lines will be considerably distorted and the mutual influence of magnetic fields and differential rotation is by no means obvious.In this paper we present a new asymptotic dispersion relation for tightly wound spiral density waves with magnetic fields along the spiral armsB (r). The effects of the magnetic fields lead to such terms likek ²(a ² +V _A ² ), wherek is the wave number,a represents the speed of sound,V _A = (B ²/4)^1/2 is the Alfvén speed,B denotes the field strength, and is the plasma density. These terms depict the well-known magnetoacoustic waves and could have been anticipated without a detailed computation. However the interaction of magnetic fields and differential rotation may give rise to other significant terms which are not so easy to foresee.We also present a more exact local dispersion relation by using the WKB approximation and study the effects of magnetic fields on the growth rate through the parametersQ andJ defined in the literature.Although the effects of the magnetic fields are rather insignificant for applications to Galactic dynamics, the effects of the magnetic fields are important for applications to star formation and problems related to the solar nebula.  相似文献   

Effects of Climate Change on Evapotranspiration from Paddy Fields in Southern Taiwan   总被引：1，自引：0，他引：1  

Pao-Shan Yu  Tao-Chang Yang  Chien-Chih Chou 《Climatic change》2002,54(1-2):165-179

The major objective of this study was to investigate the effects of climate change on evapotranspiration from paddy fields. A sensitivity analysis of meteorological variables at the Kao-Hsiung station, one of meteorological stations in southern Taiwan, was carried out using the modified Penman formula. Forty-eight-year records of temperature, relative humidity, sunshine duration, wind speed, and precipitation depth comprised the database. Trend and persistence analyses of the data were performed using the Mann–Kendall test, the Cumulative Deviation test, Linear Regression, andthe Autocorrelation Coefficient. The results indicated that only temperature and relative humidity have significant long-term trends and persistence. Two climatic scenarios, viz. (1) linear extrapolation of climatic trends and (2) the predictions of General Circulation Models (GCMs), were assumed to investigate the effects of climate change on evapotranspiration. The study revealed that evapotranspiration from paddy fields increased under both climatic scenarios studied.  相似文献   

基于PALSAR数据的青藏高原冻土形变检测方法研究   总被引：1，自引：0，他引：1  

谢酬  李震  李新武 《国土资源遥感》2008,19(3):15-19

季节性冻胀和融沉导致的地面形变是青藏高原冻土区建设施工与维护的主要问题。对冻融造成的形变进行有效监测是青藏铁 路建设与维护的前提。差分干涉测量技术是地表形变监测的重要手段之一,PALSAR（L波段的合成孔径雷达）数据在非城市区域具 有较高的相关性,适合青藏高原冻土区的地表形变监测。本文选用4景覆盖研究区域的PALSAR数据,研究利用该数据进行冻土形变 检测的方法,并对其检测结果进行了分析。结果表明,该方法与水准测量方法有较好的一致性。  相似文献   

Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay     

Jérôme Harlay  Caroline De Bodt  Anja Engel  Sandra Jansen  Quentin d’Hoop  Judith Piontek  Nicolas Van Oostende  Steve Groom  Koen Sabbe  Lei Chou 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1251-1265

The distribution of transparent exopolymer particles (TEP) was investigated during a coccolithophorid bloom in the northern Bay of Biscay (North Atlantic Ocean) in early June 2006. MODIS chlorophyll-a (Chl-a) and reflectance images before and during the cruise were used to localize areas of important biological activity and high reflectance (HR). TEP profiles along the continental margin, determined using microscopic (TEP_micro) and colorimetric (TEP_color) methods, showed abundant (6.1×10⁶–4.4×10⁷ L^?1) and relatively small (0.5–20 μm) particles, leading to a low total volume fraction (0.05–2.2 ppm) of TEP_micro and similar vertical profiles of TEP_color. Estimates of carbon content in TEP (TEP-C) derived from the microscopic approach yielded surface concentration of 1.50 μmol C L^?1. The contribution of TEP-C to particulate organic carbon (POC) was estimated to be 12% (molar C ratio) during this survey. Our results suggest that TEP formation is a probable first step to rapid and efficient export of C during declining coccolithophorid blooms.  相似文献   

Flow around sunspots from it p-mode frequency shift measurements     

Sun  Ming-Tsung  Chou  Dean-Yi  Lin  Chia-Hsien  Team  The TON 《Solar physics》1997,176(1):59-65

We use five-day helioseimic data from the Taiwan Oscillation Network to study the flow around a sunspot, NOAA 7887. The p-mode oscillations in an annular region centered at the sunspot are decomposed into the modes propagating toward and away from the sunspot. We find that the frequency of an outgoing mode is greater than that of the corresponding incoming mode. This indicates that the plasma is flowing outward from the sunspot. The outflow velocity is estimated to be about 40–80 m s^-1.  相似文献   

The Effect of Helicity Dissipation on the Critical State of an Avalanche Model for Solar Flares     

Yung-Ping Chou 《Solar physics》2001,199(2):345-369

We perform numerical simulations using an avalanche model for solar flares, in which the effect of avalanche event duration is included and the lateral boundary condition can be either open or periodic. The results from the simulations show that self-organized criticality (SOC) exists under a variety of conditions of helicity dissipation, and they are similar in the sense that the indices of power-law distributions of avalanche sizes are the same, while the duration and waiting time distributions differ little. Of interest are: (1) if there exists helicity dissipation in the course of avalanches, SOC exists only when the amount of helicity dissipation per avalanche is small; (2) sudden reductions in the total helicity of the system do not severely disturb SOC, if the amount reduced is moderate; (3) the distribution of waiting times is shown to be exponential, in consistent with the Poisson statistics other avalanche models have predicted, and the exponent increases as the effect of event duration becomes larger. The self-similar structure of the avalanche time series is also examined. These results imply that, although helicity is dissipated in resistive diffusion of flares, the amount of dissipation should be small and the conservation law of helicity thus holds in an approximate sense. Also, the coronal mass ejections (CMEs), observed to take helicity out of the solar corona in an eruptive way, may disrupt the statistical equilibrium of the corona only temporarily.  相似文献   

数值天气预报的创新之路--从初值问题到反问题   总被引：2，自引：2，他引：2  

丑纪范 《气象学报》2007,65(5):673-682

基于大气并非是一个确定论的系统,从信息论的视角考察了数值天气预报问题。认为表征初值和边值的数据可以视为输入信息(信息源),而数值模式则不过是一个信息变换机构,它把输入信息变换成预报结论而输出来,输出的预报结论则是未来天气状况的信息。于是预报的准确性受制于:一是输入信息所包含的输出信息的信息量,另一是信息在变换过程中丢失的信息量。从初值的形成过程揭示出了当前观测系统在一个时刻提供的数据没有包含初值所要求的全部信息,而缺失的部分或多或少的隐藏在过去的观测数据中。提为初值问题意味着只依据一个时刻的状态导致输入的信息量缺失,应考虑过去的历史数据以增加输入数据中所包含的预报量的信息。文中指出由于输出信息比输入还多的数值模式是不存在的,这样的改进带有根本性。进一步论证了数值模式的误差信息,也或多或少的隐藏在过去的历史数据中,为了充分使用过去的观测数据,本文建议改变问题的提法,不提成初值问题,提成反问题。资料同化本质上是反问题,其欠定性不应人为夸大。提成反问题的数值天气预报能充分应用过去的历史资料,将天气方法、统计方法、动力方法有机地结合在一起。对于这个反问题如何具体求解方面,在分析了业务和研究的区别,模式的普适性和针对性的统一的基础上,给出了反问题的具体解决途径。强调无需构建新模式(这是非常困难的工作),只需运行现成的模式,借助所关心的预报对象的历史数据来改造现成模式,因而是完全可行的。  相似文献