夹具规划设计中的映射研究

介绍了夹具规划设计过程中特征模型间的区别 ,分析了进行特征转换的必要性 ,并着重探讨了夹具设计系统中特征映射的问题 ,给出了制造特征与夹具特征间特征映射的具体实现方法 ,从而实现了夹具规划中不同特征模型之间的转换     

油藏特征模型的建立及其应用

针对油藏概念模型和实际模型存在的不足,提出了一个能够反映油藏主要地质特征、井网特征、生产特征、渗
流特征和剩余油分布特征的新模型油藏特征模型,给出了建立油藏特征模型的详细思路和具体步骤。油藏特征
模型建模相对简单,反映油藏地质特征和开发特征的程度介于概念模型和实际模型之间,但能够反映油藏的主要渗流
特征和剩余油分布特征,在此基础上,可以开展油藏开发机理和具体的注水技术措施研究。同时,该油藏特征模型的
建立也提供了一种新的建模思路,扩展了目前油藏模型的类型。最后,以孔二北油田为例详细介绍了建立油藏特征模
型的具体过程,并提出了建立在此油藏特征模型基础上的优化周期注水技术措施。     

基于零件图的板料件产品模型

本文基于板料件零件图及其成形工艺,探讨了板料件特征构型方法,提出了以特征线为核心的产品模型.采用特征线可较好地解决形状特征与精度特征的统一描述问题,使得产品模型的特征信息完备.本文详细地描述了形状特征和精度特征及其与特征线的关系.     

决策依赖聚类的高维数据特征选择

针对启发式特征选择和特征聚类驱动特征选择方法的不足,研究了决策依赖的特征冗余性问题,提出了一种基于邻域粗糙集的决策依赖特征聚类的高维数据特征选择方法(RDCFS).首先,依据邻域粗糙集模型,设计了一种特征联合依赖度增益度量,刻画数据特征在分类和辨识层面上的冗余性和关联性.其次,构建了一种最优特征簇结构的评估准则和特征冗...     

有关特征建模技术的研究

开发基于特征建模的ＣＡＤ系统是实现ＣＡＤ／ＣＡＭ一体化的根本方法,讨论了特征及其分类、特征空间及特征关系等关键技术,提出了基于特征的产品模型,并对其实现做了研究,最后建立了完整的特征模型。     

基于特征的回转体类零件成形工艺推理机制

针对回转体类零件成形工艺特点,研究了基于特征的回转体类零件挤压成形工艺推理机制.应用特征建模和知识熔接技术,建立了基于特征并包含几何特征层、工艺特征层和工艺推理层3个层次的回转体类零件特征模型,并研究了各层次之间的知识传递方法.建立了基于特征的回转体类零件成形工艺设计系统,通过应用特征组合、特征搜索匹配、工艺特征排序等技术完成挤压成形工艺路线推理,实现领域专家知识的应用,极大地提高了回转体类产品工艺设计的效率和质量.     

基于互信息的二进制区分矩阵特征约简方法

基于互信息度量的特征约简是一种重要的Filter特征约简方法,其目的是剔除条件特征中与决策类别不相关的特征,并使约简子集中特征间的相关性最小.为此,本文基于特征间的区分性评价准则,提出了互信息下二进制区分矩阵的特征约简模型,并从理论上证明了二进制区分矩阵模型与互信息模型下特征约简的等价性;其次给出了条件特征的重要性度量准则,并利用渐进式计算方法构造了一种快速的特征约简算法;最后通过实验进一步验证了算法的可行性.     

基于颜色和纹理特征图像检索技术的研究

对基于内容的图像检索中的低层特征的相关检索算法进行了深入研究,对现有颜色和纹理的自然特征中提取出的特征量的检索成功率进行了测试,发现使用单一的特征对图像进行检索查全率不高.为了提高查全率,综合了颜色和纹理特征的检索算法,给颜色特征和纹理特征分配一定的权重,设计了权重设计器,确定了查全率达到最高值时颜色和纹理特征的权重分配,提高了检索效率,识别效果很好.     

雷达图图形特征提取中的特征排序

基于多元数据的雷达图图表示,提出了雷达图重心图形特征.针对同样的多元数据不同的特征排序会导致不同的雷达图图表示,进而产生不同的重心特征,而这些重心特征会最终影响分类器的性能,因此提出一种新的问题,即雷达图图形特征提取中的特征排序问题.基于这个新的问题,设计了一种新的解决方法,即提出了基于改进的遗传算法的特征排序.同时也研究并改进了传统的基于排序的特征选择方法.基于一些机器学习数据库的分类实验结果表明:一方面,数据的原始特征排序下的重心特征和传统的特征提取方法相比,并不总是最优,但是在遗传算法下特征排序的重心特征优于传统的特征提取方法;另一方面,在遗传算法下特征排序的重心特征优于传统的基于排序的特征选择方法下的重心特征.尤其对于高维小样本的肺癌数据达到了12.5%的留一法交叉验证错误率,效果非常好.乳腺癌数据和糖尿病数据等的分类结果优于目前国际上的报道.     

基于改进蚁群算法的高精度文本特征选择方法

为了反映特征子集对分类结果的整体影响,去除噪声特征项,提出了一种基于改进蚁群算法的高精度文本特征选择方法。建立了特征选择数学模型,实现了特征选择过程与分类器分类过程间的直接关联;设计了特征优选与特征精选相结合的模型求解方案,降低了模型求解过程中的计算复杂度;提出了基于等效路径增强和局部搜索更新相结合的改进蚁群算法,提高了解的质量和稳定性。实验结果表明,与现有文本特征选择方法相比,该方法能大幅提升分类精度。     

青藏高原冬季积雪异常对东、南亚夏季风影响的初步数值模拟研究

利用一个耦合了简化的简单生物圈模式的大气环流谱模式（ＳＳｉＢ－ＧＣＭ），初步探讨了青藏高原冬季积雪异常对东、南亚夏季风环流和降水的影响及其机理。结果表明，高原地区冬季积雪增加将使随后的夏季东、南亚季风明显减弱，主要表现为东、南亚季风区降水减少，索马里急流、印度季风槽和印度西南气流减弱。另外，还提出欧亚大陆雪盖与整个高原雪盖和高原东部雪盖对东、南亚夏季风影响的敏感性问题。与欧亚大陆雪盖相比，高原雪盖是影响东、南亚季风的更敏感区，冬季高原以外雪盖增加，有可能使亚洲季风增强；当高原东部雪盖增加时，高原以东地区及印支半岛降水减少，印度东部、南部和孟加拉湾西北部降水反而增加     

青藏高原起沙量数值模拟分析

青藏高原可能是东亚上空沙尘气溶胶的重要源地。利用WRF/chem模式模拟了1961-2015年逐日青藏高原的起沙量,其结果表明:1)起沙源区主要分布在高原西部、藏北高原南部、雅鲁藏布江及其支流河谷和柴达木盆地;2)月起沙量具有双峰型结构,峰值分别出现在4-5月及11-12月;春季及秋冬季排放的沙尘气溶胶大致有以藏北高原为中心向东南方向分布的规律;3)高原年平均起沙量为10.13±1.89Tg,从1961-2015年呈现震荡向上的趋势;4)青藏高原对东亚(不包含青藏高原)月起沙量的平均贡献率为16%,其中冬季均能达到25%以上,1月最大可以达到48%。这一研究表明青藏高原是重要的沙尘源地。     

青藏高原中部地区不稳定大气边界层高度的确定与分析

利用1998年第2次青藏高原大气科学实验（Tibet Plateau Experiment, TIPEX）当雄大气边界层加强观测站的湍流观测资料,计算了青藏高原中部地区不稳定大气边界层的高度;结合低空探空获取的温度随高度的探测资料,对比分析了高原边界层演变规律,以及实验站干季、雨季不同时期的高原边界层发展规律异同;讨论了高原边界层厚度受高原地形的影响。得到高原边界层演变规律及高原边界层发展迅速,持续时间长等特点。     

青藏高原近地面层气象要素变化特征

利用第2次青藏高原气象科学实验(TIPEX)1998年5-7月改则、当雄和昌都3个大气边界层加强观测站获取的近地面层观测资料,分析了青藏高原西部、中部和东部地区近地面层风速、温度和湿度的日变化特征及其廓线规律,给出了青藏高原地区地表空气动力学参数和地表温度变化规律,讨论了高原近地面层湍流通量特征及逆湿现象。     

论青藏高原大气折射对地面精密测量的影响

首次提出了青藏高原大气折射对地面精密测量影响的特殊性问题，论述了开展高原大气折射研究的重要意义，分析了国内外研究现状，阐明了研究的目标和主要内容。     

A very strong summer monsoon event during 30-40 kaBP in the Qinghai-Xizang (Tibet) Plateau and its relation to precessional cycle

Guliya ice core records, high lake-level records in the Qinghai-Xizang Plateau and at its north side as well as vegetation succession records indicated that during the period of 30-40 kaBP, namely the later age of the megainterstadial of last glacial period, or the marine oxygen isotope stage 3, the climate of the Qinghai-Xizang Plateau was exceptionally warm and humid, the temperature was 2-4℃ higher than today and the precipitation was 40% to over 100% higher than the current average, all these suggested the existence of an exceedingly strong summer monsoon event. It has been inferred that the occurrence of such an event was attributed, on the one hand, to the stronger summer low pressure over the Plateau, which strengthened the attraction to the summer monsoon; on the other hand, to the vigorous evaporation of the tropic ocean surface, which promoted the moisture-rich southwest monsoon to flow over the Qinghai-Xizang Plateau. The background responsible for the formation of the very strong summer monsoon was that the period of 30-40 kaBP was just in the strong insolation stage of the 20ka precessional cycle, when the Qinghai-Xizang Plateau received extraordinary strong solar radiation and thus enlarged the thermodynamical contrast between the Plateau and the mid-south part of the Indian Ocean.     

Water vapor image of snow storm process over southern Tibet

The northward movement of the storm over Bengal Bay was the main weather system producing heavy snow over southern Tibet in Nov. 1995. The effect of the Tibetan Plateau on the track of the storm over Bengal Bay and its cloud system was discussed by analyzing the GMS-5 water vapor image. It is estimated from this discussion that the altitude of the Plateau obstruct effect on synoptic system can reach up to 300 hPa.     

Amplitude of climatic changes in Qinghai-Tibetan Plateau

On the basis of ice core and meteorological data from the Qinghai-Tibetan (Q-T) Plateau, this article focuses on the discussion of the problems related to the sensitivity of temporal and spatial changes of the climate in high-altitude regions, particularly in the Q-T Plateau. The features of abrupt climatic changes of the past 100 ka, 2 000 a and recent years indicate that the amplitude of these changes in the Q-T Plateau was obviously larger than that in low-altitude regions. The scope of temperature change above 6 000 m in the Q-T Plateau between glacial and interglacial stages could reach over 10°C, but only about 4°C in low-elevation regions close to sea level. During the last 2 000 a, the amplitude of temperature changes at Guliya (over 6 000 m a.s.l.) in the Q-T Plateau reached 7°C, in comparison with 2°C in eastern China at low altitude. In the present age, apparent differences of climatic warming have been observed in the Q-T Plateau, indicating that the warming in high-elevation regions is much higher than that in low-elevation regions. The temperature in over 3 500 m regions of the Q-T Plateau have been increasing at a rate of 0.25×10¹/a in recent 30 years, but almost no change has taken place in the regions below 500 m. Thus, we concluded that high-altitude regions are more sensitive to climatic changes than the low-altitude regions.     

A very strong summer monsoon event during 30–40 kaBP in the Qinghai-Xizang (Tibet) Plateau and its relation to precessional cycle

Guliya ice core records, high lake-level records in the Qinghai-Xizang Plateau and at its north side as well as vegetation succession records indicated that during the period of 30–40 kaBP, namely the later age of the megainterstadial of last glacial period, or the marine oxygen isotope stage 3, the climate of the Qinghai-Xizang Plateau was exceptionally warm and humid, the temperature was 2–4°C higher than today and the precipitation was 40% to over 100% higher than the current average, all these suggested the existence of an exceedingly strong summer monsoon event. It has been inferred that the occurrence of such an event was attributed, on the one hand, to the stronger summer low pressure over the Plateau, which strengthened the attraction to the summer monsoon; on the other hand, to the vigorous evaporation of the tropic ocean surface, which promoted the moisture-rich southwest monsoon to flow over the Qinghai-Xizang Plateau. The background responsible for the formation of the very strong summer monsoon was that the period of 30–40 kaBP was just in the strong insolation stage of the 20ka precessional cycle, when the Qinghai-Xizang Plateau received extraordinary strong solar radiation and thus enlarged the thermodynamical contrast between the Plateau and the midsouth part of the Indian Ocean.     

Comparison of sensible and latent heat fluxes during the transition season over the western Tibetan Plateau from reanalysis datasets

The sensible and latent heat fluxes during the transition season over the western Tibetan Plateau from the NCEP-1 (NCEP/NCAR Reanalysis 1), AR-II (NCEP-DOE Reanalysis 2) and ERA40 reanalysis datasets were compared and analyzed. The results show that the phase change in soil moisture has a significant effect on the sensible and latent heat fluxes over the western Tibetan Plateau (TP) due to the freezing–thawing processes during the transition from the dry to the wet period. The uncertainties in the sensible and latent heat fluxes over the western TP are quite high in the reanalysis data, and depend largely on the success of the soil moisture simulations in the models. Improving the hydrological process simulations in the land-surface models in seasonally frozen ground and in the active frozen soil layer may be an effective way of enhancing the reliability of the surface heat fluxes from the reanalysis data over the Tibetan Plateau.