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61.
本文采用同时具有识別、分解、解释异常三重作用的三元解释法■,在黄沙坪异常负值区有效地提取了由未知的深源磁性体引起的剩余异常。该异常与已知的中、浅源磁性体分处于极为类同的成矿地质背景中。后者与隐伏岩体、铅锌多金属盲矿体之间有着密切的成生联系。这为前者间接找矿提供了有力的依据。定量解释结果中,两者间的磁矩等效关系,论证了已知矿床西侧深部空间里,仍存在找到又一个大型矿床的前景。 相似文献
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63.
Characteristics and analysis of the geomagnetic variations in regions around the Qiongzhou Strait(范国华)(姚同起)(顾左文)(朱克佳)(陈伯舫)(冯戬... 相似文献
64.
Field measurements of NO and NO2 emissions from soils have been performed in Finthen near Mainz (F.R.G.) and in Utrera near Seville (Spain). The applied method employed a flow box coupled with a chemiluminescent NO
x
detector allowing the determination of minimum flux rates of 2 g N m-2 h-1 for NO and 3 g m-2 h-1 for NO2.The NO and NO2 flux rates were found to be strongly dependent on soil surface temperatures and showed strong daily variations with maximum values during the early afternoon and minimum values during the early morning. Between the daily variation patterns of NO and NO2, there was a time lag of about 2 h which seem to be due to the different physico-chemical properties of NO and NO2. The apparent activation energy of NO emission calculated from the Arrhenius equation ranged between 44 and 103 kJ per mole. The NO and NO2 emission rates were positively correlated with soil moisture in the upper soil layer.The measurements carried out in August in Finthen clearly indicate the establishment of NO and NO2 equilibrium mixing ratios which appeared to be on the order of 20 ppbv for NO and 10 ppbv for NO2. The soil acted as a net sink for ambient air NO and NO2 mixing ratios higher than the equilibrium values and a net source for NO and NO2 mixing ratios lower than the equilibrium values. This behaviour as well as the observation of equilibrium mixing ratios clearly indicate that NO and NO2 are formed and destroyed concurrently in the soil.Average flux rates measured on bare unfertilized soils were about 10 g N m-2 h-1 for NO2 and 8 g N m-2 h-1 for NO. The NO and NO2 flux rates were significantly reduced on plant covered soil plots. In some cases, the flux rates of both gases became negative indicating that the vegetation may act as a sink for atmospheric NO and NO2.Application of mineral fertilizers increased the NO and NO2 emission rates. Highest emission rates were observed for urea followed by NH4Cl, NH4NO3 and NaNO3. The fertilizer loss rates ranged from 0.1% for NaNO3 to 5.4% for urea. Vegetation cover substantially reduced the fertilizer loss rate.The total NO
x
emission from soil is estimated to be 11 Tg N yr-1. This figure is an upper limit and includes the emission of 7 Tg N yr-1 from natural unfertilized soils, 2 Tg N yr-1 from fertilized soils as well as 2 Tg N yr-1 from animal excreta. Despite its speculative character, this estimation indicates that NO
x
emission by soil is important for tropospheric chemistry especially in remote areas where the NO
x
production by other sources is comparatively small. 相似文献
65.
采用可以有效控制环境因子的室内土壤培养试验,初步研究了科尔沁沙地30种植物叶凋落物的CO2释放量及释放速率。结果表明:①在28 d培养期内,不同植物叶凋落物释放的CO2量差异很大,其中,多年生植物叶凋落物CO2释放量平均值大于一年生植物,但二者之间的差异不显著;禾本科植物叶凋落物CO2释放量平均值明显小于其他植物,二者之间呈显著差异。②在28 d培养期内,不同植物叶凋落物每四天CO2释放速率差异很大。一年生与多年生植物叶凋落物28 d内每四天释放CO2的速率无显著差异;禾本科与其他植物叶凋落物每四天释放CO2的速率在培养的前16 d差异呈显著,而后差异消失。③植物叶凋落物的全碳含量,氮含量,C/N,灰分/N及灰分含量不同造成CO2释放量及释放速率的差异。叶凋落物28 d释放CO2的量与叶凋落物初始碳含量及灰分含量均无相关关系,与叶凋落物初始氮含量呈显著正相关,与叶凋落物C/N及灰分/N呈显著负相关。叶凋落物培养期内每四天释放CO2的速率与叶凋落物初始碳含量无相关关系;叶凋落物0\_20天释放CO2的速率与叶凋落物初始氮含量呈显著正相关,与叶凋落物C/N呈显著负相关;叶凋落物9\_28天CO2释放速率与灰分/N呈显著负相关;培养后期(17\_28天)的CO2释放速率与灰分含量呈显著负相关。 相似文献
66.
遥感影像混合像元分解中的端元选择方法综述 总被引:7,自引:1,他引:7
端元选择是进行遥感影像混合像元分解的首要步骤,也是最关键的步骤,其直接影响混合像元分解的精度。该文对遥感影像混合像元分解中端元产生的特定背景、当前存在的端元选择途径和端元选择方法进行综述,并通过对当前端元选择方法的分析,提出了选择或构造端元选择方法应遵循的几个原则。 相似文献
67.
In this paper, the adaptive chirplet decomposition combined with the Wigner-Ville transform and the empirical mode decomposition combined with the Hilbert transform are employed to process various non-stationary signals (strong ground motions and structural responses). The efficacy of these two adaptive techniques for capturing the temporal evolution of the frequency content of specific seismic signals is assessed. In this respect, two near-field and two far-field seismic accelerograms are analyzed. Further, a similar analysis is performed for records pertaining to the response of a 20-story steel frame benchmark building excited by one of the four accelerograms scaled by appropriate factors to simulate undamaged and severely damaged conditions for the structure. It is shown that the derived joint time–frequency representations of the response time histories capture quite effectively the influence of non-linearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event; in this context, tracing the mean instantaneous frequency of records of critical structural responses is adopted.The study suggests, overall, that the aforementioned techniques are quite viable tools for detecting and monitoring damage to constructed facilities exposed to seismic excitations. 相似文献
68.
本文继续文献 [10 ]的工作 ,进一步讨论了测量平差 Gauss- Markov模型参数岭型广义逆估计的若干性质 ,如允许性、优效性、相对效率、抗干扰性等等 ,得到了许多重要结论。计算结果表明 ,在设计阵呈病态时 ,岭型广义逆估计确能明显改善 L S估计 相似文献
69.
改进了游离二氧化硅(fSiO2)测定中试样的分解方法,采用硫-磷混酸替代单独使用磷酸分解试样,防止了焦磷酸盐的形成,同时,氟硼酸对fSiO2的溶解率符合测定要求。改进的方法用于标准物质中fSiO2的测定,结果与标准值或磷酸溶矿重量法相符。对于ω(fSiO2)=3.26%的标样10次测定的RSD为2.4%。 相似文献
70.