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"雪龙"号破冰船是我国目前唯一的极地考察船,破冰航行是极地船舶的重要特征之一。以"雪龙"号破冰船的GPS数据为基础,通过建立模型算法识别冲击式破冰这一特殊的航行状态,在整个中国第28次南极考察航次的数据分析中,整体识别率超过86.1%,识别正确率达到98%以上。利用此算法,在中国第27次南极考察航次的破冰识别率也超过85%,识别正确率达到93.5%。雪龙船两个航次实测GPS数据验证了本文算法的可用性,而破冰识别统计结果表明,不同航次的破冰模式具有较大的差异。 相似文献
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Both deep zonal winds, if they exist, and the basic rotational distortion of Jupiter contribute to its zonal gravity coefficients Jn for n ? 2. In order to capture the gravitational signature of Jupiter that is caused solely by its deep zonal winds, one must take into account the full effect of rotational distortion by computing the coefficients Jn in non-spherical geometry. This represents a difficult and challenging problem because the widely-used spherical-harmonic-expansion method becomes no longer suitable. Based on the model of a polytropic Jupiter with index unity, we compute Jupiter’s gravity coefficients J2, J4, J6, … , J12 taking into account the full effect of rotational distortion of the gaseous planet using a finite element method. For the model of deep zonal winds on cylinders parallel to the rotation axis, we also compute the variation of the gravity coefficients ΔJ2, ΔJ4, ΔJ6, … , ΔJ12 caused solely by the effect of the winds in non-spherical geometry. It is found that the effect of the zonal winds on lower-order coefficients is weak, ∣ΔJn/Jn∣ < 1%, for n = 2, 4, 6, but it is substantial for the high-degree coefficients with n ? 8. 相似文献
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运用质谱技术 ,测定了南极中山站至 Dome A剖面 1 998/1 999年度表面雪样氧同位素组成。结果表明 ,表面雪样氧同位素组成变化范围相当大 (- 2 2 .5 1‰ - - 5 0 .6 7‰ ) ,且具有随距中山站距离逐渐增大、海拔高度逐渐增加而逐渐减小的趋势。线性回归分析显示表面雪样氧同位素组成与距中山站距离、海拔高度和纬度存在着很好的相关性 ,这实际上反映出稳定同位素组成和温度之间的密切联系 相似文献
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于1988年8月和1989年11月在巢湖西部的南淝河下游、河口及湖区采集水样,用GC/MS法分析,检出了酚类、农药、氯代烃类、脂肪烃、苯系物,以及多环芳烃等多种有机污染物,表明巢湖部分水域已受到污染。河水中检出的多环芳烃的浓度要比湖水中的高得多。实验室藻培养液的分析说明,湖水中存在的α-蒎烯、薁、二甲基二硫化物、6-甲基-2-庚酮是来源于生物的;湖水中存在的正十七烷也部分地来源于藻类活动。用富营养化水体作为水源经氯化处理生产自来水,会增加自来水中潜在致突变物质的含量。 相似文献
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We investigate, through both asymptotic analysis and direct numerical simulation, precessionally driven flow of a homogeneous fluid confined in a fluid-filled circular cylinder that rotates rapidly about its symmetry axis and precesses about a different axis that is fixed in space. A particular emphasis is placed on a spherical-like cylinder whose diameter is nearly the same as its length. At this special aspect ratio, the strongest direct resonance occurs between the spatially simplest inertial mode and the precessional Poincaré forcing. An asymptotic analytical solution in closed form describing weakly precessing flow is derived in the mantle frame of reference for asymptotically small Ekman numbers. We also construct a nonlinear three-dimensional finite element model – which is validated against both the asymptotic solution and a constructed exact solution – for elucidating the nonlinear transition leading to disordered flow in the precessing spherical-like cylinder. Properties of both weakly and strongly precessing flows are investigated with the aid of a complete inertial-mode decomposition of the fully nonlinear solution. Despite a large effort being made, the well-known triadic resonance is not found in the precessing spherical-like cylinder. The energy contained in the precessionally forced inertial mode is primarily transferred, through nonlinear effects in the viscous boundary layers, to the geostrophic flow that becomes predominant when the precessional Poincaré force is sufficiently large. It is found that the nonlinear flow evolutes gradually and progressively from the laminar to disordered as the precessional force increases. 相似文献