一种面向环境扫描的彩色点云流实时压缩算法

随着数字孪生技术的不断发展,人们面临将大规模、高维度的点云数据进行压缩编码的问题,以提高传输效率。然而大多点云编码方式存在压缩实时性不强、压缩效率低、点云格式要求过高等问题。针对解决这些问题,提出了一种基于谷歌Draco几何压缩库的实时彩色点云流压缩(Real-time Color Stream Draco,RCS-Draco)算法。将算法集成到ROS框架内,借助ROS消息流,对点云流实时地进行编码和解码,提高了算法的实时性;通过建立优化裁剪模型,对点云进行裁剪和滤波,去除了漂移和离群点云,提高了压缩算法的压缩效率。建立量化预测模型,对点云的RGB颜色信息进行编码,解决了大多数点云压缩算法无法处理颜色信息的问题。对比试验通过调整压缩等级和量化参数,证明RCS-Draco算法的平均压缩率最高能够达到77%、平均压缩和解压时间小于0.035 s、位置平均误差小于0.05 m、属性平均误差小于35;并通过相融试验证明RCS-Draco算法在各项指标上优于Draco算法。试验结果表明,RCS-Draco压缩算法在压缩实时性、效率、点云格式方面均表现良好,能够有效地提升传输效率。

山到九峰静 云流一派闲——重庆缙云山诗话

宋代冯时行《温泉寺》诗云:“借问禅林景若何,半天楼殿冠嵯峨.莫言暑气此中少,自是清风高处多.岌岌九峰晴有雾,(氵弥)(氵弥)一水远无波.我来游览便归去,不必吟成证道歌.”此诗作者冯时行,字当可,是缙云山下梁滩坝人,自号“缙云先生”.宋徽宗宣和六年(1124)中状元.

真挚性情的书写——论郝建生散文集《纤云流月去无声》

郝建生的散文集《纤云流月去无声》,是不可多得的佳作之一。在他笔下,处处透着真诚豁达和对生命的敬畏,以及对历史与现实的厚重思考和深切追问,使作品带着一种强烈的艺术震撼,而这一切都源于作家身上所特有的良知和风骨。

基于兴趣簇的云流媒体系统模型的研究

当今,随着科技和网络技术的不断发展,网络运用更加广泛,遍及了各行各业,使整个世界都充满了网络。把网络按照不同的功能等分成不同的节点,每个节点都具有不同的兴趣,多个节点连接在一起,就形成了兴趣簇。在兴趣簇的基础上,云流媒体系统需要进行不断的创新,对传统的模型进行改进,形成新的模型,这样才能更加适应网络的发展,才能为不同的用户提供更加优质的服务。这篇文章从以下几个方面探索如何在兴趣簇的基础上建立云流媒体系统模型,从而让更多的用户感受到网络的魅力。

舞韵

舞韵挹云任光的薄雾裹围凭歌的雨丝淋注无言的对视里遥远而清晰的你渐渐走来心灵的空间被占据我们迈开了多姿的舞步急促的是秦汉边塞的战鼓凝重的是三峡巨澜在奔突刚劲的是骏马是雄鹰轻盈的象飘飞的烟花柳絮优雅的如白云流水也有慌乱的则是险滩峡谷……我和你走一程独特的...

《宛珠撷珍》序

《宛珠撷珍》——这部精选当今海内外有关南阳古今作家作品研究评论的结集出版了。主编嘱我这个名不见报纸杂志、声不入广播电视、迹不涉官场文场、心不系浮云流水的人,写个开场白,一来搜索枯肠,难成门外文谈,二来人以文传,不免攀附之嫌,却之再三,不获宥可,只好勉为其难。 大凡说到一个地方,不单是灵山秀水,天宝物华,更在于光辉历史,名家哲人。古申吕之国的南阳,以其西掩秦岭、北依伏牛、东接淮泗、南通江汉,扼关中而蔽瓯越,屏中州而握荆蛮,地理位置的重要,使其在周秦汉唐千余年间成为经济、政治。

投资热点——海南旅游业

热潮腾起 旅游业称雄的泰国、美国,境外投资热的日本、韩国,稳健的西欧,还有印尼、俄罗斯等国的商人、企业家都瞄准了海南省的旅游业,把它看成投资获利率最稳而高、见效最快的一个行业。更有趣的是:过去投资旅游集中在省会海口和闻名于世的“天涯海角”的三亚市区的风景点,而今视海南全岛都是旅游业开发的宝地,且由单项开发变为成片开发;投资类型由旅馆、度假村发展到空中型、海底型、田园型、会议型、风情型、名胜型……类型繁多,且都配套齐全。到1996年年底,海南外商投资企业7800家,实际利用外资5.2亿美元。其中旅游企业1000余家,占全部企业1/8强。

GRIDLESS METHOD FOR UNSTEADY VISCOUS FLOWS

Gridless method is developed for unsteady viscous flows involving moving boundaries. The point distri- bution of gridless method is implemented in an isotropic or anisotropic way according to the features of viscous flows. In the area far away from the body, the traditional cloud of isotropic points is used, while in the adjacent area, the cloud of anisotropic points is distributed. In this way, the point spacing normal to the wall can be small enough for simulating the boundary layer, and meanwhile, the total number of points in the computational do- main can be controlled due to large spacing in other tangential direction through the anisotropic way. A fast mov- ing technique of clouds of points at each time-step is presented based on the attenuation law of disturbed motion for unsteady flows involving moving boundaries. In the mentioned cloud of points, a uniform weighted least- square curve fit method is utilized to discretize the spatial derivatives of the Navier-Stokes equations. The pro- posed gridless method, coupled with a dual time-stepping method and the Spalart-Allmaras turbulence model, is implemented for the Navier-Stokes equations. The computational results of unsteady viscous flows around a NLR7301 airfoil with an oscillating flap and a pitching NACA0012 airfoil are presented in a good agreement with the available experimental data.

Broadening of cloud droplet size distributions and warm rain initiation associated with turbulence: an overview

In the study of warm clouds,there are many outstanding questions.Cloud droplet size distributions are much wider,and warm rain is initiated in a shorter time and with a shallower cloud depth than theoretical expectations.This review summarizes the studies related to the effects of turbulent fluctuations and turbulent entrainment-mixing on the broadening of droplet size distributions and warm rain initiation,including observational,laboratorial,numerical,and theoretical achievements.Particular attention is paid to studies by Chinese scientists since the 1950s,since most results have been published in Chinese.The review reveals that high-resolution observations and simulations,and laboratory experiments,are needed because knowledge of the detailed physical processes involved in the effects of turbulence and entrainment-mixing on cloud microphysics still remains elusive.The effects of turbulent fluctuations and entrainment-mixing processes have been unrealistically separated in most theoretical studies.They could be unified by further advancement of a systems theory into a predictive theory.Developing parameterizations for the effects of fluctuations and entrainment-mixing processes is still in its infancy,and more studies are warranted.

Soil Erosion under Different Land Use Types and Zones of Jinsha River Basin in Yunnan Province,China

Severe soil erosion in the middle and upper reaches of Yangtze River has been regarded as a major environmental problem. The on-site impact of soil erosion on agricultural production and the off-site impact on floods and sedimentation in Yangtze Rive are well known. A quantitative assessment of soil erosion intensity is still scanty for developing appropriate soil erosion control measures for different land use types and zones in this region. This article constructs a localized USLE and estimates the average soil loss in the Jinsha River Region in Yunnan Province, one of the priority areas for soil erosion control in the middle and upper reaches of Yangtze River. The estimation is done under different land uses and zones in this basin. The estimation shows that while soil erosion in the cultivated land is the most severe, 36～40% of the garden and forest land suffers from soil erosion of various degrees due to lack of ground cover and other factors. Soil erosion in the pasture is modest when the ground cover is well maintained. It also confirmed that terracing can reduce soil erosion intensity significantly on the cultivated land. Research findings suggest that sufficient attention must be paid to regeneration of the ground cover in reforestation programs. In addition to mass reforestation efforts, restoration of grassland and terracing of the cultivated land should also play an important role in erosion control.

Validation for a tropical belt version of WRF: sensitivity tests on radiation and cumulus convection parameterizations

Version 3.9 of WRF-ARW is run with a tropical belt configuration for a period from 2012 to 2016 in this study. The domain covers the entire tropics between 45°S and 45°N with a spatial resolution of about 45 km. In order to verify two radiation schemes and four cumulus convection schemes, eight experiments are performed with different combinations of physics parameterization schemes. The results show that eight experiments present reasonable spatial patterns of surface air temperature and precipitation in boreal summer, with the spatial correlation coefficient (COR) between simulated and observed temperature exceeding 0.95, and that between simulated and observed precipitation ranges from 0.65 to 0.82. The four experiments with the RRTMG radiation scheme show a better performance than the other four experiments with the CAM radiation scheme. In the four experiments with the RRTMG radiation scheme, the COR between simulated and observed surface air temperature is about 0.98, and that between simulated and observed precipitation ranges from 0.76 to 0.82. Comparatively, the two experiments using the new Tiedtke cumulus parameterization scheme can simulate better diurnal variation of precipitation in boreal summer than the other six experiments. In particular, for the diurnal cycle of precipitation over land and ocean, the experiment using the RRTMG radiation scheme and the new Tiedtke cumulus convection scheme shows that the peaks of precipitation rate appear at 0400 LST and 1600 LST, in agreement with observation.

A COMPREHENSIVE ANALYSIS OF INTERACTIONS BETWEEN MESO-SCALE CONVECTIVE CLOUD CLUSTERS IN TYPHOONS AND MESOSCALE HEAVY RAINS

In this paper, time and space distribution regularity of meso-scale heavy rains in five selected typhoons which landed at Fujian from 1996 to 1998 has been analyzed. Besides, with hourly digitized satellite infrared imagery, the features of the mesoscale are revealed for the genesis and evolution of mesoscale convective systems in typhoons. It indicates that the intensity of mesoscale storms is closely connected with the temperature and the area of the coldest cloud cluster. The heavy rainfall usually emerges on the eastern side of the mesoscale convective cloud clusters, where the cloud mass is developing and with a dense gradient and big curvature of isoline of the cloud top temperature.

Two-dimensional Numerical Model for Debris Flows in the Jiangjia Gully,Yunnan Province

Debris flows are recurrent natural hazards in many mountainous regions.This paper presents a numerical study on the propagation of debris flows in natural erodible open channels,in which the bed erosion and sedimentation processes are important.Based on the Bingham fluid theory,a mathematical model of the two-dimensional non-constant debris flow is developed.The governing equations include the continuity and momentum conservation equations of debris flow,the sediment convection-diffusion equation,the bed erosion-deposition equation and the bed-sediment size gradation adjustment equation.The yield stress and shear stress components are included to describe the dynamic rheological properties.The upwind control-volume Finite Volume Method (FVM) is applied to discretize the convection terms.The improved SIMPLE algorithm with velocity-free-surface coupled correction is developed to solve the equations on non-orthogonal,quadrilateral grids.The model is applied to simulate a debris flow event in Jiangjia Gully,Yunnan Province and to predict the flow pattern and bed erosion-deposition processes.The results show the effectiveness of the proposed numercial model in debris flow simulation and potential hazard analysis.

Using Satellite Data to Analyze the Initiation and Evolution of Deep Convective Clouds

In this study, two deep convective cloud cases were analyzed in detail to study their initiation and evolution. In both cases, all deep convective clouds were positioned at the rear of the cold front cloud bands and propagated backward. Satellite data showed that prior to initiation of the deep convective clouds, thermodynamic and moist conditions were favorable for their formation. In the morning, a deep convective cloud at the rear of cold front cloud band propagated backward, the outflow boundary of which created favorable conditions for initiation. An additional deep convective cloud cluster moved in from the west and interacted with the outflow boundary to develop a mesoscale convective system(MCS) with large, ellipse-shaped deep convective clouds that brought strong rainfall. The initiation and evolution of these clouds are shown clearly in satellite data and provide significant information for nowcasting and short-term forecasting.

Exploring the relationship between the cloud-top and tropopause height in boreal summer over the Tibetan Plateau and its adjacent region

The distribution characteristics of cloud-top and tropopause height in the tropics and subtropics in boreal summer are analyzed based on CALIPSO data for the period 2008-2012.The maximum values of cloud-top vertical cumulative frequency above the tropopause （CTAT） are concentrated in three tropical regions：the Asian summer monsoon region,Central America,and western Africa.The contributions to the area-weighted CTAT frequency in the three regions from the Northern Hemisphere are 49.0%,13.5%,and 12.4%,respectively.Moreover,the contribution of troposphere-to-stratosphere transport （TST） in the Asian monsoon region to global TST can be far greater than 50%,according to analysis of the continuous equation,velocity potential,and divergent wind from ERA-Interim data.Furthermore,the Asian summer monsoon circulation system controls the distribution of the cloud top.On the south side of the Tibetan Plateau,the maximum frequency of the cloud top,more than 10% per 500 m vertically,is most likely to appear in the core of the high-level easterlyjet near the tropopause height （16.5 km）.Over the Tibetan Plateau,the maximum frequency of the cloud top,greater than 3% per 500 m vertically,is suppressed below 11 km,far away from the thermodynamic tropopause height but close to the dynamic tropopause height of 2 PVU （potential vorticity units）.

Leaching and Redistribution of Nutrients in Surface Layer of Red Soils in Southeast China

The leaching and redistribution of nutrients in the surface layer of 4 types of red soils in SoutheastChina were studied with a lysimeter experiment under field conditions. Results showed that the leachingconcentrated in the rainy season (from April to June). Generaily, the leaching of soil nutrients from thesurface layer of red soils was in the order of Ca > Mg > K > NO3-N. In fertilization treatment, the totalamount of soil nutrients leached out of the surface layer in a red soil derived from granite was the highest inall soils. The uptake by grass decreased the leaching of fertilizer ions in surface layer, particularly for NO3-N.Soil total N and exchangeable K, Ca and Mg in the surface layer decreased with leaching and grass uptakeduring the 2 years without new fertilization of urea, Ca(H2PO4)2, KCl, CaCO3 and MgCO3. Ca movedfrom the application layer (0~5 cm) of fertilizer and accumulated in the 10~30 cm depth in the soils studiedexcept that derived from Quaternary red clay. The deficiency of soil exchangeable K will become a seriousdegradation process facing the Southeast China.

OBSERVATIONAL STUDY OF LIGHTNING CHARACTERISTICS IN HAIL-PRODUCING CLOUDS

1 INTRODUCTION Lightning is a phenomenon of atmospheric electricity with convective storms. Since the 1960＇s, its characteristics during weather processes of torrential rain, hails and tornadoes have been widely studied and a lot of attempts made to probe into the mechanisms responsible for the formation of lightningIll, giving rise to two theories explaining the lightning genesis, from the points of convection and ice-phase precipitation, respectively, In addition, some studies show, from various aspects, that lightning of severe convective weather. indicates the occurrence There has been lack of concrete indices to identify lightning features and determine hail-producing clouds. Apart from diagnostic . analysis based on conventional data , this work studies the evolution of lightning in 11 hails using relevant records and Doppler radar information and sums up a number of lightning features for hail weather in the sub-plateau area of Gansu province by taking as the criterion whether convective clouds cause hails in determining hail-producing clouds. In Gansu, hailproducing clouds usually originate from mountainous areas, follow fixed routes of movement and are often accompanied with heavy rainfall as they produce hails in more than a spot in the life cycle. To mitigate losses, it is essential to use scientific detectors to warn of hail weather in advance and conduct weather modification to check the growth of hails. The weather radar is an efficient tool to watch and forecast severe convective weather like hails, for it not only detects the structure but also tracks down the generation and evolution of hail-producing clouds to aid in isolating where the hail falls. It is, however, not realistic to perform real-time radar watch in Northwest China and existing radars are not capable of observing thunderstorms. Costing relatively low to purchase and maintain, the lightning locator has wide range of measurement and works nonstop without human attendance, making it easier to watch large-scale convective clouds in the region. With hails, heavy rains and tornadoes isolated and warned of based on features captured by the locator, operations of weather modification can be made more efficient with further identification from radar echoes and observed facts of electric mechanisms can be better understood for convective weather.

Focused fluid flow in the Baiyun Sag, northern South China Sea: implications for the source of gas in hydrate reservoirs

The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three environments of focused fluid flow： gas chimneys, mud diapirs and active faults have been identified. Widespread gas chimneys that act as important conduits for fluid flow are located below bottom simulating reflections and above basal uplifts. The occurrence and evolution of gas chimneys can be divided into a violent eruptive stage and a quiet seepage stage. For most gas chimneys, the strong eruptions are deduced to have happened during the Dongsha Movement in the latest Miocene, which are observed below Pliocene strata and few active faults develop above the top of the Miocene. The formation pressures of the Baiyun Sag currently are considered to be normal, based on these terms： 1） Borehole pressure tests with pressure coefficients of 1.043-l.047; 2） The distribution of gas chimneys is limited to strata older than the Pliocene; 3） Disseminated methane hydrates, rather than fractured hydrates, are found in the hydrate samples; 4） The gas hydrate is mainly charged with biogenic gas rather than thermogenic gas based on the chemical tests from gas hydrates cores. However, periods of quiet focused fluid flow also enable the establishment of good conduits for the migration of abundant biogenic gas and lesser volumes ofthermogenic gas. A geological model goveming fluid flow has been proposed to interpret the release of overpressure, the migration of fluids and the formation of gas hydrates, in an integrated manner. This model suggests that gas chimneys positioned above basal uplifts were caused by the Dongsha Movement at about 5.5 Ma. Biogenic gas occupies the strata above the base of the middle Miocene and migrates slowly into the gas chimney columns. Some of the biogenic gas and small volumes ofthermogenic gas eventually contribute to the formation of the gas hydrates.

IMPACTS OF TWO TROPICAL CYCLONES EXPERIENCING EXTRATROPICAL TRANSITION DURING NORTHWARD PROGRESSION ON THE RAINFALL OF LIAODONG PENINSULA

Both of Typhoon Winnie (9711) and Matsa (0509) underwent an extratropical transition (ET) process when they moved northward after landfall and affected Liaodong Peninsula. However, Matsa produced half as much rainfall as Winnie, although it struck Liaodong Peninsula directly while Winnie passed through the Bohai Sea. The relations between the ET processes and the precipitation over Liaodong Peninsula are examined. The result shows that the precipitation difference between Winnie and Matsa was closely related to the interactions between the westerly systems and typhoons during their ET processes. Winnie was captured by the upper westerly trough and then coupled with it when moving to the mid-latitudes, and the positive anomaly of moist potential vorticity (MPV) was transported downward from the upper troposphere over the remnant circulation of the tropical cyclone (TC). It was favorable to the interaction between tropical warm and wet air and westerly cold air, causing convective cloud clusters to form and develop. The rain belt composed of several meso-β cloud clusters over the Liaodong Peninsula, resulting in heavy rainfall. On the other hand, Matsa did not couple with any upper trough during its ET process and the positive anomaly of MPV in the upper troposphere and its downward transfer were weak. Only one meso-β cloud cluster occurred in Matsa’s rain belt during its ET process that tended to lessen rainfall over Liaodong Peninsula.