A Method for Improving Power Distribution Characteristics of Space Time Block Codes

Improving power distribution characteristics of space time block codes(STBCs),namely peak to average power ratio(PAPR),average to minimum power ratio(Ave/min),and probability of transmitting"zero"by antenna,makes easier their practical implementation.To this end,this study proposes to multiply full diversity STB C with a non-singular matrix in multiple input multiple output(MIMO)or multiple input single output(MISO)systems with linear or maximum likelihood(ML)receivers.It is proved that the obtained code achieves full diversity and the order of detection complexity does not change.The proposed method is applied to different types of STBCs.The bit error rate(BER)and power distribution characteristics of the new codes demonstrate the superiority of the introduced method.Further,lower and upper bounds on the BER of the obtained STBCs are derived for all receivers.The proposed method provides trade-off among PAPR,spectral efficiency,energy efficiency,and BER.

Joint DOA and time delay estimation method for space-time coherent distributed signals based on search

Under dense urban fading environment, performance of joint multi-path parameter estimation method based on traditional point signal model degrades seriously. In this paper, a new space and time signal model based on multipath distribution function is given after new space and time manifold is reconstructed. Then joint spacetime signal subspace is obtained by converting acquired channel from time domain to frequency domain .Then space and time spectrum is formulated by the space sub-matrix and time sub-matrix taken out of joint space-time signal subspace, and parameters are estimated by searching the minimum eigenvalues of the space matrix and the time matrix. Lastly, A space and time parameters matching process is performed by using the orthogonal property between joint noise subspace and the space-time manifold. In contrast with tradition MUSIC, the algorithm we present here only need two 1- dimension searching and was not sensitive to different distribution function.

Simulation and Prediction on Space-Time Distribution of Water Quality in Dianchi Lake

It is very important in pollution treatment to clarify the space-time distribution of water quality in Dianchi Lake. Based on the sample data obtained from 10 observation stations every month from 2008 to 2009, it uses space-time semi-variogram and ordinary kriging method to simulate the space-time variance and distribution of water quality indictors (TN, TP, BOD, CODMn, DO, Chlorophyl-α, etc.). Because the space-time semivariogram also has a certain of ex-trapolation function. From the simulation results, the pollution is mainly concentrated at the North (Caohai) and the Southwest area (Haikou), and water pollution has a increase trend.

Space-time Dynamics of Dendroctonus valens Population in China and Spatial Sampling Technique based on Its Spatial Distribution Pattern

Red turpentine beetle （RTB）, Dendroctongs valens LeConte, is a destructive forest invasive species in China, it mainly attacks Pings tabuliformis and P. bungeana. So far it has spread rapidly to the provinces of Shanxi, Hebei, Henan, Shanxi and Beijing since its first outbreak in Shanxi Province in 1998, and has caused extensive tree mortality. Space-time dynamics of D. valens population and spatial sampling technique based on its spatial distribution pattern were ana- lyzed using geostatistical methods in the pure P. tabuliforis forests and mixedwood stands which were at different damage levels. According to the spatial distribu- tion of D. valeas population, the specific spatial sampling technique was also studied, and then was compared with traditional sampling technique. The spatial sam- piing technique combined with sampling theory and the biological characteristics of D. valens population, which not only could calcnlate the error of the sampling, but also could discuss the optimal sampling number and the optimum size of plot according to different damage levels and different stand types. This helps to explain population expansion and colonization mechanism of D. valens, and to provide a good reference for adopting snitable control measures.

SLC Method and Earthquakes' Clustering Features in Time-Space in the Top Area of the Kunlun-Altun-Arc

By using the SLC(Single-Link Cluster)method,this study worked in three respects:(a)set up three-dimensional(3-D)SLC software that can deal with a large catalogue of earthquakes and analyze the characteristics of earthquakes’ clustering and scattering in time-space:(b)defined several parameters to describe the distinguishing feature for the SLC frame and developed a technique to calculate the 3-D SLC frames and these parameters with gradual time-sliding,and inspected their variations with time,especially before large events; and(c)by using these means,treated the earthquake catalogue in the top area of the Kunlun-Altun-Arc as well as some valuable results that had been obtained.

Simulation analysis on microscopic discharge characteristics of the bipolar corona of a floating conductor

A floating conductor exhibits a bipolar corona phenomenon with microscopic discharge characteristics that are still unclear.In this study,a plasma simulation model of the bipolar corona with 108 chemical reaction equations is established by combining hydrodynamics and plasma chemical reactions.The evolution characteristics of electrons,positive ions,negative ions and neutral particles,as well as the distribution characteristics of space charges are analyzed,and the evolutionary flow of microscopic particles is summarized.The results indicate that the positive end of the bipolar corona initiates discharge before the negative end,but the plasma chemistry at the negative end is more vigorous.The electron generation rate can reach 1240 mol(m^(3) s)^(-1),and the dissipation rate can reach 34 mol(m^(3) s)^(-1).The positive ion swarm is dominated by O_(4)^(+),and the maximum generation rate can reach 440 mol((m^(3) s)^(-1).The negative ion swarm is mainly O_(2) and O_(4).The O_(2) content is approximately 1.5-3 times that of O_(4),and the maximum reaction rate can reach 51 mol(m^(3) s)^(-1).The final destination of neutral particles is an accumulation in the form of O_(3) and NO,and the amount of O3 produced is approximately 4-6 times that of NO.The positive end of the bipolar corona is dominated by positive space charges,which continue to develop and spread outwards in the form of a pulse wave.The negative end exhibits a space charge distribution structure of concentrated positive charges and diffused negative charges.The validity of the microscopic simulation analysis is verified by the macroscopic discharge phenomenon.

On analyzing space-time distribution of evaporation duct height over the global ocean

The statistical features of the evaporation duct over the global ocean were comprehensively investigated with reanalysis data sets from the National Centers for Environmental Prediction. These data sets have time and spatial resolutions of 1 h and 0.313°x0.312°, respectively. The efficiency of the analysis was evaluated by processing weather buoy data from the Pacific Ocean and measuring propagation loss in the Yellow Sea of China. The distribution features of evaporation duct height （EDH） and the related meteorological factors for different seas were analyzed. The global EDH is generally high and demonstrates a latitudinal distribution for oceans at low latitudes. The average EDH is approximately 11 m over oceans beside the equator with a latitude of less than 20°. The reasons for the formation of the global EDH features were also analyzed for different sea areas.

Space-time evolution rules of acoustic emission location of unloaded coal sample at different loading rates

By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE ringing counting rate increases largely and the AE energy curves appear an obvious ''step'',which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point.

Land Use Characteristics of Areas Around the Metro Station in the Old City of Chengdu: A Case Study of Sichuan Gymnasium Station

Taking Sichuan Gymnasium Station as the research object, we explore land use characteristics over time of areas around Sichuan Gymnasium Station in terms of time. We extract the basic information of land use in areas around Sichuan Gymnasium Station in 2005, 2011, and 2016 through Google Earth in order to draw the map of land use status in three time nodes. We then analyze the degree of mixing and equilibrium, intensity of development of land, and land use patterns of areas around Sichuan Gymnasium Station with indexes including the area proportion of land use patterns, information entropy, and degree of equilibrium within a 1,000-m radius centered on the station, so as to reveal the spatial distribution characteristics of land around the station in different time nodes. Through comparative analysis, it is found that the development of rail transit has not significantly contributed to the boom of commerce and the development of the old city of Chengdu. We also analyze land use changes in areas around Sichuan Gymnasium Station in terms of space, and find that land use patterns in areas around commuter stations seem to be more complicated than that of the average station, and land use patterns in areas around Huaxiba Station and Nijiaqiao Station on Line 1, which opened first, are more complicated than that of Moziqiao Station and Yiguanmiao Station on Line 3. The original land use patterns formed in the old city often determine the selection of rail transit routes and rail transit stations. Adaptive stations do not play a decisive role in land use patterns in their surrounding areas, but have some impact on the plot ratio and building height of land for commercial use within the core area of the stations.

The Time-Frequency Energy Attenuation Factor and Its Application on the Basis of Gauss Linear Frequency-Modulated Continuous Wavelet Transform

Based on the Gauss linear frequency modulated wavelet transform, a new characteristic index is presented, namely time frequency energy attenuation factor which can reflect the difference features of waveform in earthquake focus mechanism, wave traveling path and its attenuation characteristics in focal area or near field. In order to test its validity, we select the natural earthquakes and explosion or collapse events whose focus mechanisms vary obviously,and some natural earthquakes located at the same site or in a very small area. The study indicates that the time frequency energy attenuation factors of the natural earthquakes are obviously different with that of explosion or collapse events, and the change of the time frequency energy attenuation factors is relatively stable for the earthquakes under the normal seismicity background. Using the above mentioned method, it is expected to offer a useful criterion for strong earthquake prediction by continuous earthquake observation.

Improved scheme with cooperative diversity based on distributed space-time block coding

An improved scheme with cooperative diversity based on distributed space-time block coding （WCD- DSTBC） is proposed, which effectively achieves diversity gains and improves the performance of the system by sharing some single-antenna users＇ antennas to form a virtual antenna array and combining with distributed spacetime block coding （DSTBC） mode. Then the relation between the system BER and the interuser BER for WCDDSTBC scheme is theoretically derived and the closed-form expression of BER for WCD-DSTBC system is obtained. The simulation results show that the proposed WCD-DSTBC scheme achieves distinct gains over the non-cooperative multi-carrier CDMA （MC-CDMA） system. When system BER is le-3 and interuser BER is le-3, about 2.5 dB gain can be gotten. When interuser channel state information （CSI） outgoes the users＇ individual CSI, about 3 dB gain is also achieved.

Distribution of Random Session Key Based on Key-Insulated Public-Key Cryptosystems

Based on the characteristic of key-insulated public-key cryptosystem, wepropose a distributed landora session keys distribution protocol without a key distribution center.The session key is generated by different user and only used one time. So thekey is one-time key. Inaddition, the user who generates the next one-time key, is random selected by the current sessionkey. In the protocol of this paper, the characteristic of time in the key-insulated public-key, adistributed protocol, translates into the characteristic of spaee which every point has differentsecret key in the different period. At the same time, the system is fit for key management in AdHoe, and is a new scheme of key management in Ad Hoc.

Hydrodynamic characteristics of a four-compartment periodic anaerobic baffled reactor

Periodic anaerobic baffled reactor （PABR） is a novel reactor based on the design concept of anaerobic baffled reactor （ABR）. Residence time distribution （RTD） studies on both clean and working reactors at the same hydraulic residence time （HRT） of 2 d were carded out to investigate the dead spaces and mixing patterns in PABRs at different organic loading rates （OLRs） in various switching manners and frequencies. The results showed that the fraction of dead space in PABR was similar to that in ABR, which was low in comparison with other reactor designs. Dead space may be divided into two categories, hydraulic and biological. In RTD studies without biomass, the hydraulic dead space in the PABR run in an ＂every second＂ switching manner with T = 2 d was the lowest whereas that in the PABR run in a T = ∞ （ABR） switching manner was the highest. The same trend was obtained with the total dead space in RTD studies with biomass no matter what the OLR was. Biological dead space was the major contributor to dead space but affected decreasingly at higher OLR whichever switching manner the PABR run in. The flow patterns within the PABRs were intermediate between plug-flow and perfectly mixed under all the conditions tested,

Analysis on the Climate Characteristics of Thunderstorm in Fujian Province during 1960-2007

[Objective] The research aimed to study the activity characteristics and climate rule of thunderstorm in Fujian Province.[Method] Based on the daily thunderstorm data in 67 meteorological stations of Fujian Province during 1960-2007,the spatial and temporal distribution characteristics of thunderstorm in Fujian Province were analyzed by using the climate tendency rate,the trend coefficient and so on.[Result] The distribution of thunderstorm days showed the northeast-southwest direction and increased gradually from the coast to the inland in Fujian Province during 1960-2007.The high value zone was in Longyan,and the thunderstorm days in the coastal islands were the fewest.The thunderstorm days had the obvious decrease trend in Fujian Province in 48 years.The decrease speeds in the central coastal area and most of inland mountain area were 3.5 and 4.5 d/10 a.The decrease speed was 5.5 d/10 a in the north of Ningde,the east of Sanming and some areas in Nanping.The trend coefficient variation of thunderstorm days had the obvious regional characteristic.Especially the decrease trend in the inland mountain area was more obvious than that in the coast.The decrease of thunderstorm day trend coefficient in the north of Nanping was the most,and the trend coefficient was-0.65.But the decrease trend in the central coastal area wasn’t obvious,and the coefficient was only-0.15.The thunderstorm day had the obvious seasonal variation.The multi-occurrence period of thunderstorm was during March-september and reached the maximum value in August.Started from September,the thunderstorm quickly decreased.From October to February in next year,the thunderstorm happened seldom.The average first thunderstorm date in the northwest area was earlier than that in the southeast area.The difference of average final thunderstorm date in the north and south areas wasn’t big.For the first thunderstorm date in the north and west of Fujian was early,and the final thunderstorm date was later,the thunderstorm activity time in the whole year was longer than that in the coast.They differed by nearly one month.[Conclusion] The research provided the scientific basis for the climate feasibility demonstration of major project items,provided the theory basis about the weather climate aspect for the thunder prevention and disaster reduction,and also laid the foundation for further studying the formation mechanism of thunderstorm in Fujian.

Hydraulic modeling of an anaerobic expanded bed reactor for municipal sewage treatment

Anaerobic expanded bed reactor(AEBR) is mostly used for the treatment of fairly low strength wastewaters. Since the performance of AEBR largely depends on its hydraulic characteristics, residence time distribution(RTD) method is commonly used for investigation of the hydraulic characteristics of AEBR under different ascending velocity of mixed liquor. In this paper, a pilot-scale AEBR reactor is investigated for treatment of municipal sewage in which lithium chloride is used as a tracer. The results show that the AEBR could be considered as the superimposition of several constant stirred tank reactors(CSTR) and the increase of hydraulic up-flow velocity could increase the number of the CSTR and decrease the volume rate of the dead zone. The optimal up-flow velocity of the investigated AEBR was approximately 1.9 m/h in the municipal sewage treatment.

Status Quo of Maker Spaces in Main Urban Area of Chengdu

This paper, based on the literature review and field investigation, studied the status quo of maker spaces in main urban district of Chengdu at a time when the development of the maker spaces has received strong support from national and local governments. In addition to introducing the related concepts and policy support of the maker space, it summarized its distribution characteristics, audience characteristics, and status quo as well as problems and presented the direction for the development of the maker space in main urban area of Chengdu grounded on a survey of the status quo of national maker spaces in main urban area of Chengdu.

Spatial and Temporal Distribution of Pine Wood Nematodes in Yiling District Based on GIS

[Objectives]This study was conducted to accurately understand the spatial distribution of the outbreak of pine wood nematode disease,explore its spatial laws,and provide a more scientific and efficient analysis and decision-making basis for the prevention and management of pine wood nematode disease.[Methods]Taking the GIS management of Bursaphelenchus xylophilus tree felling in Yiling District as an example,the spatial positions of epidemic wood in the two years from 2019 to 2020 were collected.The spatial data management function of ArcGIS software was used to collect point and surface layers.Spatial information maps were drawn by spatial visualization,trend surface,spatial autocorrelation,nearest neighbor distance index and spatial-temporal clustering analysis of kernel density,so as to intuitively understand the evolution of spatial pattern trend of pine wood nematode disease,and to explain the variation raw and diffusion characteristics of pine wood nematode disease.[Results](1)Under the control measures,the affected pine forests and epidemic sites(subcompartments)decreased in the following year,the spread of the epidemic was still spreading,which was spreading from the central to the western and northern regions.The distribution of the plane epidemic sites was sparse from high concentration.The new epidemic sites occurred in a jump,and the number of affected pine trees was high.The outbreak was concentrated in a certain area,and the risk was high.The natural transmission and diffusion would coexist for a long time.(2)The epidemic trend of pine nematode in the two years was in the east and west,with a high value in the east,and the trend line was almost straight line.The outbreak of pine nematode showed cone-shaped central point aggregation and spread.(3)The spatial and temporal clustering characteristics of the epidemic show spatial clustering in the overall pattern,high clustering of pine victims caused by the spread of the epidemic source and clustering distribution pattern of epidemic points.(4)In the two years,the damaged pine trees were searched within the range of 5 km by using the distance threshold.The kernel density maps showed that the damaged pine trees in 2019 were more serious than those in 2020.The result of density map was consistent with the nearest neighbor distance index,and the damaged pine forests were mainly concentrated.(5)The epidemic situation of B.xylophilus disease in this region has a certain number of epidemic sites and a wide distribution area,the epidemic situation is difficult to eradicate in a short time.On the comprehensive measures,we should increase the clearing of epidemic trees,block the spread of the epidemic situation in the new areas,reduce the epidemic sites,regulate the density of pine trees by forest management,reduce the density of Monochamus alternatus and establish a broad-leaved forest ecosystem.[Conclusions]The study provides assistive technology support for the prevention and control of pine wood nematode disease.

Genesis and significance of quartz cement in sandstones

Quartz cement as syntaxial overgrowths is one of the most abundant cements in sandstones. Distribution of quartz cement in time and space indicates that the more younger the stratigraphy is, the more smaller the amount of quartz cement, and the amount of quartz cement increases with increasing of depth and basin type also is a factor which controls the amount of quartz cement. The sources of silica for quartz cement have many different opinions, but there is one or more dominant sources. Temperature and pH of fluid are major factors which influence the precipitation of quartz cement. There exist three hypotheses on the flow of pore fluid and transport and precipitation of silica, that is, the hypothesis of cycle of shallow underground water, the hypothesis of high concentration of fluid driven by compaction and the hypothesis of diffusion and recycle of local fluid. The research of quartz cement is significant for the timing of paleotemperature, heterogeneity of reservoir, physical property of reservoir and the timing of oil immersion, etc.

Satellite breakup behaviors and model under the hypervelocity impact and explosion:A review

The primary causes of satellite breakups are hypervelocity impact and explosion,the research on satellite breakup can be used not only to evaluate the influence of breakup event on the space environment,but also to trace whether the satellite has been deliberately attacked.It is of great significance in both civil and military aspects.The study of satellite breakup behaviors and model is reviewed to summarize the research progress and insufficiency in recent decades,including the satellite breakup experiment,measurement and characterization of fragments,distribution characteristics of breakup fragments,satellite breakup model,etc.The classical studies are introduced in detail,and the limitations of the current research are pointed out.According to the current research results,the contemporary challenges and future directions for satellite breakup study are presented.The research on satellite breakup is developing in two directions:the miniaturization of satellite size and the complexity of satellite component.The study on satellite breakup needs to be explored and deepened on improving the experimental launch speed,expanding the model application range and breakup revealing the results under combined effect of impact and explosion.

Space-Time Properties as Quantum Effects. Restrictions Imposed by Grothendieck’s Scheme Theory

In this paper we consider properties of the four-dimensional space-time manifold M caused by the proposition that, according to the scheme theory, the manifold M is locally isomorphic to the spectrum of the algebra A, M ≅Spec (A), where A is the commutative algebra of distributions of quantum-field densities. Points of the manifold M are defined as maximal ideals of density distributions. In order to determine the algebra A, it is necessary to define multiplication on densities and to eliminate those densities, which cannot be multiplied. This leads to essential restrictions imposed on densities and on space-time properties. It is found that the only possible case, when the commutative algebra A exists, is the case, when the quantum fields are in the space-time manifold M with the structure group SO (3, 1) (Lorentz group). The algebra A consists of distributions of densities with singularities in the closed future light cone subset. On account of the local isomorphism M ≅Spec (A) , the quantum fields exist only in the space-time manifold with the one-dimensional arrow of time. In the fermion sector the restrictions caused by the possibility to define the multiplication on the densities of spinor fields can explain the chirality violation. It is found that for bosons in the Higgs sector the charge conjugation symmetry violation on the densities of states can be observed. This symmetry violation can explain the matter-antimatter imbalance. It is found that in theoretical models with non-abelian gauge fields instanton distributions are impossible and tunneling effects between different topological vacua | n> do not occur. Diagram expansion with respect to the -algebra variables is considered.