Optimal two-impulse rendezvous using constrained multiple-revolution Lambert solutions

A solution to the fixed-time minimum-fuel two-impulse rendezvous problem for the general non-coplanar elliptical orbits is provided. The optimal transfer orbit is obtained using the constrained multiple-revolution Lambert solution. Constraints consist of lower bound for perigee altitude and upper bound for apogee altitude. The optimal time-free two-impulse transfer problem between two fixed endpoints implies finding the roots of an eighth order polynomial, which is done using a numerical iterative technique. The set of feasible solutions is determined by using the constraints conditions to solve for the short-path and long-path orbits semimajor axis ranges. Then, by comparing the optimal time-free solution with the feasible solutions, the optimal semimajor axis for the two fixed-endpoints transfer is identified. Based on the proposed solution procedure for the optimal two fixed-endpoints transfer, a contour of the minimum cost for different initial and final coasting parameters is obtained. Finally, a numerical optimization algorithm (e.g., evolutionary algorithm) can be used to solve this global minimization problem. A numerical example is provided to show how to apply the proposed technique.     

Study on transmission mechanism of thermal infrared remote sensing for abrupt geothermal anomaly in volcanic region

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浙东南地区蜡石矿及其成矿远景

本文总结了浙东南地区蜡石矿的分布,成因类型及其特征;成矿地质条件和控矿因素;划分了成矿远景区和提出了地质工作布置建议。     

基于多元时间序列的Kn近邻预测模型

提出了一种基于多元时间序列的Ｋｎ近邻短期气候预测模型。该模型既保留了Ｋｎ近邻算法的优良特性,同时又考虑了气候系统有关状态量之间的物理关系和动力行为特性。用该模型对云南各区域的平均月雨量距平值进行预测试验,其对云南１９９１年５月～１９９８年６月的月雨量距平值预测检验的距平符号相关准确率为６３．５％,对云南１９９１～１９９８年的５月雨量距平值预测检验的距平符号相关准确率则可达到７０．０％。该模型的建立具有一定的实际业务应用价值。     

1993年7月湖北咸宁4.1级地震序列的活动特征

1993年 7月底至 8月中旬在咸宁发生的ML4 .1震群是一比较典型的有感震群 ,通过多种测震手段对该震群进行分析和处理 ,得到下列认识和结果 :1、该震群是一个非前兆震群。 2、此震群是一个主震型震群 ,地震主要发生在两个阶段 ,每个阶段均出现密集 -平静过程。 3、该震群可能与NE向潜山断裂的活动有关。 4、对咸宁震群的各种测震学参数计算表明 ,有一些参数在湖北省比较适用 (如b ,η ,U ,K ,ρ等 ) ,而有些则不适合 (如h ,F 等 )。     

尼罗罗非鱼(Oreochromis niloticus Linn)胃酸的PH值,周日变化及其在消化兰藻中的作用

通过测定喂食水华微囊藻的尼罗罗非鱼胃PH值、不同颜色粪便的叶綠素/脱镁叶綠素比例,发现尼罗罗非鱼具有一个与摄食相关的胃酸分泌周期。摄食旺期胃平均PH值为1.47,最低值为0.8。停食后PH值升高,最大值为6.0。用不同浓度的盐酸处理水华微囊藻和对不同颜色粪便的营养分析结果表明,高浓度的胃酸(PH<2)溶解了水华微囊藻细胞壁,为肠消化酶对细胞内含物进行消化创造了先决条件。     

Land use effects on soil organic carbon,microbial biomass and microbial activity in Changbai Mountains of Northeast China

Land use changes are known to alter soil organic carbon （SOC） and microbial properties, however, information about how conversion of natural forest to agricultural land use as well as plantations affects SOC and microbial properties in the Changbai Moun- tains of Northeast China is meager. Soil carbon content, microbial biomass carbon （MBC）, basal respiration and soil carbon mineraliza- tion were studied in five selected types of land use： natural old-growth broad-leaved Korean pine mixed forest （NF）; spruce plantation （SP） established following clear-cutting of NF; cropland （CL）; ginseng farmland （GF） previously under NF; and a five-year Mongolian oak young forest （YF） reforested on an abandoned GF, in the Changbai Mountains of Northeast China in 2011. Results showed that SOC content was significantly lower in SP, CL, GF, and YF than in NF. MBC ranged from 304.4 mg/kg in CL to 1350.3 mg/kg in NF, which was significantly higher in the soil of NF than any soil of the other four land use types. The SOC and MBC contents were higher in SP soil than in CL, GF, and YF soils, yielding a significant difference between SP and CL. The value of basal respiration was also higher in NF than in SP, CL, GF, and YF. Simultaneously, higher values of the metabolic quotient were detected in CL, GF, and YF soils, indicat- ing low substrate utilization of the soil microbial community compared with that in NF and SP soil. The values of cumulative mineral- ized carbon and potentially mineralized carbon （Co） in NF were significantly higher than those in CL and GF, while no significant dif- ference was observed between NF and SP. In addition, YF had higher values of Co and C mineralization rate compared with GF. The results indicate that conversion from NF into agricultural land （CL and GF） uses and plantation may lead to a reduction in soil nutrients （SOC and MBC） and substrate utilization efficiency of the microbial community. By contrast, soils below SP were more conducive to the preservation of soil organic matter, which was reflected in the comparison of microbial indicators among CL, GF, and YF land uses. This study can provide data for evaluating soils nutrients under different land use types, and serve as references for the rational land use of natural forest in the study area.     

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