Lossy Point Cloud Attribute Compression with Subnode-Based Prediction

Recent years have witnessed that 3D point cloud compression(PCC)has become a research hotspot both in academia and industry.Especially in industry,the Moving Picture Expert Group(MPEG)has actively initiated the development of PCC standards.One of the adopted frameworks called geometry-based PCC(G-PCC)follows the architecture of coding geometry first and then coding attributes,where the region adaptive hierarchical transform(RAHT)method is introduced for the lossy attribute compression.The upsampled transform domain prediction in RAHT does not sufficiently explore the attribute correlations between neighbor nodes and thus fails to further reduce the attribute redundancy between neighbor nodes.In this paper,we propose a subnode-based prediction method,where the spatial position relationship between neighbor nodes is fully considered and prediction precision is further promoted.We utilize some already-encoded neighbor nodes to facilitate the upsampled transform domain prediction in RAHT by means of a weighted average strategy.Experimental results have illustrated that our proposed attribute compression method shows better rate-distortion(R-D)performance than the latest MPEG G-PCC(both on reference software TMC13-v22.0 and GeS-TM-v2.0).

Spatio-Temporal Context-Guided Algorithm for Lossless Point Cloud Geometry Compression

Point cloud compression is critical to deploy 3D representation of the physical world such as 3D immersive telepresence,autonomous driving,and cultural heritage preservation.However,point cloud data are distributed irregularly and discontinuously in spatial and temporal domains,where redundant unoccupied voxels and weak correlations in 3D space make achieving efficient compression a challenging problem.In this paper,we propose a spatio-temporal context-guided algorithm for lossless point cloud geometry compression.The proposed scheme starts with dividing the point cloud into sliced layers of unit thickness along the longest axis.Then,it introduces a prediction method where both intraframe and inter-frame point clouds are available,by determining correspondences between adjacent layers and estimating the shortest path using the travelling salesman algorithm.Finally,the few prediction residual is efficiently compressed with optimal context-guided and adaptive fastmode arithmetic coding techniques.Experiments prove that the proposed method can effectively achieve low bit rate lossless compression of point cloud geometric information,and is suitable for 3D point cloud compression applicable to various types of scenes.

Introduction to Point Cloud Compression

Characterized by geometry and photometry attributes, point cloud has been widely applied in the immersive services of various 3Dobjects and scenes. The development of even more precise capture devices and the increasing requirements for vivid rendering in-evitably induce huge point capacity, thus making the point cloud compression a demanding issue. In this paper, we introduce sev-eral well-known compression algorithms in the research area as well as the boosting industry standardization works. Specifically,based on various applications of this 3D data, we summarize the static and dynamic point cloud compression, both including irreg-ular geometry and photometry information that represent the spatial structure information and corresponding attributes, respective-ly. In the end, we conclude the point cloud compression as a promising topic and discuss trends for future works.

The use of point load test for Dubai weak calcareous sandstones

Intact rock is typically described according to its uniaxial compressive strength （UCS）. The UCS is needed in the design of geotechnical engineering problems including stability of rock slopes and design of shallow and deep foundations resting on and/or in rocks. Accordingly, a correct measure-ment/evaluation of the UCS is essential to a safe and economic design. Typically, the UCS is measured using the unconfined compression tests performed on cylindrical intact specimens with a minimum length to width ratio of 2. In several cases, especially for weak and very weak rocks, it is not possible to extract intact specimens with the needed minimum dimensions. Thus, alternative tests （e.g. point load test, Schmidt hammer） are used to measure rock strength. The UCS is computed based on the results of these tests through empirical correlations. The literature includes a plethora of these correlations that vary widely in estimating rock strength. Thus, it is paramount to validate these correlations to check their suitability for estimating rock strength for a specific location and geology. A review of the available correlations used to estimate the UCS from the point load test results is performed and summarized herein. Results of UCS, point load strength index and Young＇s modulus are gathered for calcareous sandstone specimens extracted from the Dubai area. A correlation for estimating the UCS from the point load strength index is proposed. Furthermore, the Young＇s modulus is correlated to the UCS.

YC地区转换波数据处理及裂隙预测

裂隙介质的横波响应能提供对裂隙走向与密度一种直接测量.为了探测YC地区裂隙型储层特征,在该区进行了纵波源三分量数据采集.经过精细地处理,YC地区转换波成像质量得到了改善.以此为基础,对该区的裂隙特征进行了预测.预测结果与本区的应力场分析和钻井揭示的裂隙特征比较吻合.本文所介绍的一些关键转换波资料处理技术、解释方法和分析结论对今后陆地转换波勘探有一定借鉴作用.

A Q-Enhanced CMOS RF Filter for Multi-Band Wireless Communications

An RF bandpass filter with a Q-enhancement active inductor is presented. The design technique for a tunable Q-enhancement CMOS active inductor operating in the wide RF-band is described. Moreover,issues related to noise and stability of the active inductor are explained. The filter was fabricated in 0.18μm CMOS technolo- gy,and the circuit occupied an active area of only 150μm ×200μm. Measurement results show that the filter centered at 2. 44GHz with about 60MHz bandwidth （3dB） is tunable in center frequency from about 2.07 to 2. 44GHz. The ldB compression point is - 15dBm while consuming 10. 8mW of DC power,and a maximum quality factor of 103 is attained at the center frequency of 2.07GHz.

纵波勘探中的炸药激发方式分析

在野外采集工程中，地震波激发方式是影响地震记录品质和工程成本的主要因素之一。因此，寻找最佳的激发方式是野外施工单位关心的焦点。本文从弹性力学理论出发，结合一些日常生活中的感性认识，对炸药激发技术作了组会激发和长柱激发的具体分析与讨论，最后认为用炸药点源激发是纵波勘探工程的最佳激发方式，并提出梅花图形组合是模拟点源激发的有效方法。

PS转换波共转换点的几种计算方法及实际应用

目前常用的共转换点计算公式是在单层均匀介质模型条件下导出的。Thomsen于 1999年提出多层介质条件下的共转换点计算公式 ,其假设前提与实际情况更为接近 ,对纵横波速度比的定义也更为精细。通过采用上述 2种不同计算方法对实际资料进行共转换点分选及叠加处理并对比 。

A Fast Compression Framework Based on 3D Point Cloud Data for Telepresence

In this paper,a novel compression framework based on 3D point cloud data is proposed for telepresence,which consists of two parts.One is implemented to remove the spatial redundancy,i.e.,a robust Bayesian framework is designed to track the human motion and the 3D point cloud data of the human body is acquired by using the tracking 2D box.The other part is applied to remove the temporal redundancy of the 3D point cloud data.The temporal redundancy between point clouds is removed by using the motion vector,i.e.,the most similar cluster in the previous frame is found for the cluster in the current frame by comparing the cluster feature and the cluster in the current frame is replaced by the motion vector for compressing the current frame.The hrst,the B-SHOT(binary signatures of histograms orientation)descriptor is applied to represent the point feature for matching the corresponding point between two frames.The second,the K-mean algorithm is used to generate the cluster because there are a lot of unsuccessfully matched points in the current frame.The matching operation is exploited to find the corresponding clusters between the point cloud data of two frames.Finally,the cluster information in the current frame is replaced by the motion vector for compressing the current frame and the unsuccessfully matched clusters in the curren t and the motion vectors are transmit ted into the rem ote end.In order to reduce calculation time of the B-SHOT descriptor,we introduce an octree structure into the B-SHOT descriptor.In particular,in order to improve the robustness of the matching operation,we design the cluster feature to estimate the similarity bet ween two clusters.Experimen tai results have shown the bet ter performance of the proposed method due to the lower calculation time and the higher compression ratio.The proposed met hod achieves the compression ratio of 8.42 and the delay time of 1228 ms compared with the compression ratio of 5.99 and the delay time of 2163 ms in the octree-based compression method under conditions of similar distortion rate.

MULTIPLE POSITIVE SOLUTIONS FOR FIRST ORDER IMPULSIVE SINGULAR INTEGRO-DIFFERENTIAL EQUATIONS ON THE HALF LINE

In this paper, the author discusses the multiple positive solutions for an infinite boundary value problem of first order impulsive singular integro-differential equations on the half line by means of the fixed point theorem of cone expansion and compression with norm type.

MULTIPLE POSITIVE SOLUTIONS FOR FIRST ORDER IMPULSIVE SUPERLINEAR INTEGRO-DIFFERENTIAL EQUATIONS ON THE HALF LINE

In this paper, the author discusses the multiple positive solutions for an infinite boundary value problem of first order impulsive superlinear integro-differential equations on the half line by means of the fixed point theorem of cone expansion and compression with norm type.

High linearity AlGaN/GaN HEMT with double-Vth coupling for millimeter-wave applications

We demonstrated an AlGaN/GaN high electron mobility transistor(HEMT)namely double-Vthcoupling HEMT(DVC-HEMT)fabricated by connecting different threshold voltage(Vth)values including the slant recess element and planar element in parallel along the gate width with N;O plasma treatment on the gate region.The comparative studies of DVC-HEMT and Fin-like HEMT fabricated on the same wafer show significantly improved linearity of transconductance(Gm)and radio frequency(RF)output signal characteristics in DVC-HEMT.The fabricated device shows the transconductance plateau larger than 7 V,which yields a flattened fT/fmax-gate bias dependence.At the operating frequency of 30 GHz,the peak power-added efficiency(PAE)of 41%accompanied by the power density(Pout)of 5.3 W/mm.Furthermore,the proposed architecture also features an exceptional linearity performance with 1-d B compression point(P1 d B)of 28 d Bm,whereas that of the Fin-like HEMT is 25.2 d Bm.The device demonstrated in this article has great potential to be a new paradigm for millimeter-wave application where high linearity is essential.

The existence of generalized synchronisation of three bidirectionally coupled chaotic systems

The existence of two types of generalized synchronisation is studied. The model considered here includes three bidirectionally coupled chaotic systems, and two of them denote the driving systems, while the rest stands for the response system. Under certain conditions, the existence of generalised synchronisation can be turned to a problem of compression fixed point in the family of Lipschitz functions. In addition, theoretical proofs are proposed to the exponential attractive property of generalised synchronisation manifold. Numerical simulations validate the theory.

反转构造的运动学分析与形态类型

反转构造是具有重要油气勘探意义的一种复合构造样式。伸展盆地发育的3套层序和控制性断层上的零点是认识反转构造的基本参数；此导出的反转率、位移－距离曲线和生长指数可用于运动学分析。含油气盆地中的2大类4亚类反转构造分别形成于面状断层的扩展褶皱作用和铲状断层的弯曲褶皱作用。构造反转可对油气聚集和油气勘探造成多方面的影响。

Portable Perceptron Network-Based Fast Mode Decision for Video-Based Point Cloud Compression

In Video-based Point Cloud Compression(V-PCC),2D videos to be encoded are generated by 3D point cloud projection,and compressed by High Efficiency Video Coding(HEVC).In the process of 2D video compression,the best mode of Coding Unit(CU)is searched by brute-force strategy,which greatly increases the complexity of the encoding process.To address this issue,we first propose a simple and effective Portable Perceptron Network(PPN)-based fast mode decision method for V-PCC under Random Access(RA)configuration.Second,we extract seven simple hand-extracted features for input into the PPN network.Third,we design an adaptive loss function,which can calculate the loss by allocating different weights according to different Rate-Distortion(RD)costs,to train our PPN network.Finally,experimental results show that the proposed method can save encoding complexity of 43.13%with almost no encoding efficiency loss under RA configuration,which is superior to the state-of-the-art methods.The source code is available at https://github.com/Mesks/PPNforV-PCC.

EXISTENCE AND MULTIPLICITY OF POSITIVE SOLUTIONS TO THIRD-ORDER PERIODIC BOUNDARY VALUE PROBLEM

The existence and multiplicity of positive solutions to a periodic boundary value problem for nonlinear third-order ordinary differential equation are established, based on the zero point theorem concerning cone expansion and compression of order type. Our main approach is different from the previous papers on the existence of multiple positive solutions to the similar problem.