Constraints on Characteristics and Distribution of Gas Hydrate and Free Gas Using Broad-Band Processing of Three-Dimensional Seismic Data

Gas hydrate drilling expeditions in the Pearl River Mouth Basin,South China Sea,have identified concentrated gas hydrates with variable thickness.Moreover,free gas and the coexistence of gas hydrate and free gas have been confirmed by logging,coring,and production tests in the foraminifera-rich silty sediments with complex bottom-simulating reflectors(BSRs).The broad-band processing is conducted on conventional three-dimensional(3D)seismic data to improve the image and detection accuracy of gas hydratebearing layers and delineate the saturation and thickness of gas hydrate-and free gas-bearing sediments.Several geophysical attributes extracted along the base of the gas hydrate stability zone are used to demonstrate the variable distribution and the controlling factors for the differential enrichment of gas hydrate.The inverted gas hydrate saturation at the production zone is over 40% with a thickness of 90 m,showing the interbedded distribution with different boundaries between gas hydrate-and free gas-bearing layers.However,the gas hydrate saturation value at the adjacent canyon is 70%,with 30-m-thick patches and linear features.The lithological and fault controls on gas hydrate and free gas distributions are demonstrated by tracing each gas hydrate-bearing layer.Moreover,the BSR depths based on broad-band reprocessed 3D seismic data not only exhibit variations due to small-scale topographic changes caused by seafloor sedimentation and erosion but also show the upward shift of BSR and the blocky distribution of the coexistence of gas hydrate and free gas in the Pearl River Mouth Basin.

A broad-band sub-harmonic mixer for W-band applications

In order to improve the bandwidth of the conventional sub-harmonic mixer, a broad-band, high intermediate frequency（IF） sub-harmonic mixer for W-band applications is proposed. Replacing the open and short stubs that are used in the convertional sub-harmonic mixer with a broad-band band-pass filter and a low-pass filter, respectively, a wide operating frequency band is achieved. Furthermore, without the use of the edge-coupled band-pass filter at radio frequency（RF） port, the proposed structure can be realized by common hybrid microwave integrated circuit technology at W- band. The measured results show that the proposed subharmonic mixer can operate from 80 to 107.5 GHz for RF frequency and support up to 18 GHz for the IF bandwidth. Also, the measured results show that the single-sideband conversion loss is less than 13. 7 dB over the available RF frequency band, while the minimum conversion loss is about 9 dB at an RF of 92. 5 GHz and an 1F of 3 GHz. Thus, a large operating bandwidth performance at W-band can be achieved by the orooosed mixer.

Broad-Band All-Optical Wavelength Conversion of Differential Phase-Shift Keyed Signal Using an SOA-Based Nonlinear Polarization Switch

Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a semiconductor optical amplifier （SOA） based nonlinear polarization switch. A wavelength converter for the 10 G b/s DPSK signal is presented, which has a wide wavelength range of more than 30 nm. The converted signals experience small power penalties less than 1.4 dB compared with the original signal, at a bit error rate of 10-9. Additionally, the optical spectra, the measured waveforms and the open eye diagrams of the converted signals show a high quality wavelength conversion performance.

Broad-Band FMR Linewidth of Co_2MnSi Thin Films with Low Damping Factor:The Role of Two-Magnon Scattering

The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonMity of the ferromagnetic resonance mode and other degenerate spin wave modes was broken by magnetic anisotropy, voids, second phase, surface defects, etc., which is important in analysis of ferromagnetic resonance linewidth. Direct fitting to linewidth with Gilbert damping is advisable only when the measured linewidth is a linear function of measuring frequency in a broad band measurement. We observe the nonlinear ferromagnetic resonance linewidth of Co2MnSi thin films with respect to measuring frequency in broad band measurement. Experimental data could be well fitted with the model including two-magnon scattering with no fixed parameters. The fitting results show that two-magnon scattering results in the nonlinear linewidth behavior, and the Gilbert damping factor is much smaller than reported ones, indicating that our Co2MnSi films are more suitable for the applications of spin transfer torque.

Study of characteristics of long-period ground motion response spectra by using broad-band records of the Chinese Digital Seismograph Network

Broad band and very broad band (BB and VBB) records of Chinese Digital Seismograph Network (CDSN) from 65 earthquakes are used to calculate the horizontal relative displacement, relative velocity and absolute acceleration response spectra with critical damping ratio ζ =0.005, 0.01, 0.02, 0.05 and 0.10, respectively. The results show that it is insufficient to obtain the credible characteristics of long-period ground motion response spectra only with the common ground acceleration records in engineering, while the broad band records of CDSN, as an important supplementary to ground acceleration records, can be used to study the characteristics of long-period ground motion response spectra.

Plasmon-enhanced broad-band quantum-cutting of NaBaPO4:Eu^2+,Er^3+phosphors with silver nano-particles

NaBaPO4:Eu^2+,Er^3+phosphors and Ag nano-particles(NPs)were prepared by the solid-state reaction and chemical reduction method,respectively.The fluorescence spectra and decay curves demonstrate the effective energy transfer from Eu^2+to Er^3+and the existence of three-photon quantum-cutting through two-step cross-relaxation of Er^3+.The quantum-cutting emission is peaked at 1534 nm with a broad excitation band centered at 352 nm,Plasmon-enhanced quantum-cutting of NaBaPO4:Eu^2+,Er^3+phosphors was realized by decorating Ag NPs.The largest enhancement factor is 1.395.It is hopeful to improve the photovoltaic conversion efficiency of Ge solar cells by using this phosphor.

Implementation of the Broad-band User Access Network and the Study of the Key Algorithm for Improving the Performance of Asymmetrical Networks

This thesis is based on the design and development of ADSL access networks. We have completed the hardware and software functions in two main ADSL equipments: ATU C and ATU R. With the system design, we carry out researches to find out effective methods to improved performance in the following aspects: (a) how to allocate limited bandwith among services with different QoS requirements and (b) what is the effect of asymmetric links on TCP end to end flow control mechanism. We make detailed analyses and propose useful solutions to those problems we find. The main contents of this thesis are as follows: (1) the design and realization of ADSL access system. This part includes the principles of ADSL access technology, ADSL broadband access network architecture, and ATM over ADSL protocol models that we use in our system. We give detailed hardware and software design steps in this part, and list system testing results to show the system performance. In our hardware, the CPU is a RISC microprocessor. Combined with a high speed digital signal processor, the whole system can hold high reliability. Our software design platform is a pSOS multi task real time operation system. We have developed a series of hardware drivers besides other tasks for high level control and interruption processing. Currently, our system has reached the expected performance under test environment. Our next step is the development of DSLAM and in this part we give a feasible design scheme. (2) Packet scheduling policy in ADSL system. In order to optimize ATU R performance, we need a scheduling policy to regulate the order and number of packet output to the uplink. For this purpose, we study the scheduling algorithm design methods in a single network node and their performance. After studying the existing algorithms carefully, we first conclude certain important design principles and criterions for scheduling policy evaluation. And then by using service curve function, we make detailed performance analysis of a typical scheduling policy — the earliest deadline first. The advantage of characterizing service by using a function is that the service curve can provide a wide spectrum of service characterization. With this method, we first develop a generalized algorithm for calculating the deadlines used in the service curve based on the earliest deadline first policy, and then design a simplified computing program for an important curve. After that, holding fair bandwidth allocation and packet deadline guarantee as policy evaluation standards, we analyze this scheduling policy performance and propose solutions to those problems that we find. Finally, we, in theory, prove these improving algorithms. All these solutions and algorithms we design in this part are now under development in real systems and will enhance system performance. (3) Effects of asymmetric links on TCP performance and solutions. TCP is a widely used transmission control protocol. It regulates its forward data sending through reverse ACKs. What are the new problems to its flow control mechanism on asymmetric links and how to solve them are the two main points of this part. We first study the relationship between normalized bandwidth ratio, link buffer capacity and TCP link throughput under asymmetric link models. We find that TCP ack transportation on slow backward link is a key reason that causes the problems in TCP asymmetric links. Serving this as a start point, we present several improving solutions to TCP flow control algorithm and test them through simulation. Besides, TCP has been widely implemented in many networks. To give compatibility with current TCP end users, we use scheduling solutions to regulate data packet and ack packet transmission ratio onto uplinks. In the theoretical analysis of several typical scheduling policies, we find a feasible algorithm to control TCP data efficiency on asymmetric links. Finally, we prove those analyses and propose algorithm through simulation.

网络基础设施建设对包容性绿色增长的影响——基于“宽带中国”战略的准自然实验

推动包容性绿色增长是解决我国低碳发展目标与经济增长矛盾的重要途径。本文基于2010~2022年我国地级市层面数据,利用熵权TOPSIS法从多个维度测算了289个地级市的包容性绿色增长水平,采用多期双重差分模型探究网络基础设施建设对包容性绿色增长的影响及传导机制。研究结果表明:(1)网络基础设施建设能够有效促进包容性绿色增长水平的提升;(2)网络基础设施建设对于非资源型城市包容性绿色增长效应显著高于资源型城市;(3)网络基础设施建设能够通过提高制造业集聚水平、促进产业结构升级、鼓励技术创新进一步提升包容性绿色增长水平。本文在进一步完善包容性绿色增长的现有分析框架基础上,为政府推进“宽带中国”战略实施、缩小区域发展差距以及促进经济高质量发展提供政策启示。

Co^(2+)掺杂W型铁氧体的制备和吸波性能研究

为解决单一铁氧体吸波材料吸波频带窄的问题,采用固相法制备了Co^(2+)掺杂的W型钡铁氧体Ba(Zn_(1-x)Co_(x))_(2)Fe_(16)O_(27)(x=0、0.2、0.4、0.6、0.8、1.0)铁氧体,研究了Co^(2+)掺杂对W型钡铁氧体晶体结构、微观形貌、电磁性能和吸收性能的影响。结果表明,随着Co^(2+)掺杂量的增加,铁氧体晶体结构保持不变,掺杂Co^(2+)的W型钡铁氧体具有六角片状结构。随着金属离子的加入,粒径有不同程度减小。当Co^(2+)掺杂的摩尔分数x为0.4时,铁氧体的磁损耗最高。含量为70%的Ba(Zn_(0.6)Co_(0.4))2Fe_(16)O_(27)铁氧体吸收涂层的最大反射损耗为-22 dB,峰值位置在12.5 GHz,反射损耗RL<-10 dB的带宽约为8 GHz(8~16 GHz),实现了宽频带强吸收。

一种双简支―悬臂梁反共振隔振器设计分析与试验

[目的]为探究三元件型反共振隔振器的实现形式,提出一种由一根悬臂端含质量块的双简支-悬臂梁与一根双支撑梁所组成的机械装置(BAVI)。[方法]首先,分析双简支-悬臂梁的动态特性,推导其阻抗方程;然后,根据驱动点阻抗函数综合其低阶模型是单惯容与单弹簧二元件的串联结构,并解析低阶模型的等效参数;最后,通过装置试件设计与试验,验证其反共振特性和理论方法有效性,并在此基础上分析装置刚度特性及不同阻尼形式的效果。[结果]结果表明,当跨度比共振隔振器结构,具有“高静低动”刚度特性;在双简支-悬臂梁上采取阻尼措施后,可实现隔振区传递率以最大速率衰减的同时抑制共振峰的效果。[结论]所提机械装置证明了三元件型反共振隔振器的可实现性,提供了一种简易可行的工程结构。

一种S波段雷达通信电子战多功能宽带DAM的设计

本文创新性地提出了一种S波段多功能宽带DAM,首先介绍了该型DAM的顶层架构设计,接着介绍了各个功能组成模块的设计过程,最后给出了该型DAM的指标实现情况。该型DAM可以分时实现雷达、通信及电子战功能,最大瞬时带宽可达200MHz,支持任意波形产生,在多功能综合射频系统中具有良好的应用前景。

一种宽带宽波束圆极化微带天线的设计

本文设计了一款宽带宽波束圆极化微带天线。天线采用堆叠的双层圆贴片结构,结合四点顺序旋转馈电方式,实现了宽带圆极化辐射性能;在叠层圆贴片周边加载垂直接地金属柱环形阵,利用波束引向作用和等效零模谐振特性,在大带宽范围内实现了半功率波束宽度(HPBW)的有效展宽,并保证宽带宽波束内的圆极化辐射性能。对天线进行了加工、测试。实测结果表明,S 11小于-10 dB的阻抗带宽(4.54 GHz~11.50 GHz)为87%,覆盖了期望的应用工作频带6 GHz~10 GHz;轴比小于3 dB的带宽达到了33.1%(6.71 GHz~9.36 GHz);HPBW在6 GHz~8 GHz范围内接近100°,在整个带宽内均超过75°;除了9.5 GHz以上频段,工作频带内的6 dB轴比波束宽度覆盖范围都接近200°,表明天线在宽带和宽波束内具有良好的圆极化性能。

基于尖脉冲子波的高分辨率气枪震源设计

高分辨率气枪震源的设计是海上油气资源勘探的关键环节之一。分析震源子波形态与分辨率的关系,确定以尖脉冲子波作为震源优化的依据。基于非理想气体条件气枪子波模型对不同容量气枪的子波进行模拟,定量分析了不同容量气枪的主脉冲峰值及达到峰值的时间。提出通过调整阵列中不同容量气枪延迟激发时间和沉放深度,使阵列中各气枪主脉冲峰值同相叠加以构建尖脉冲子波的方法。在常规阵列的基础上设计了两种尖脉冲气枪阵列,并与常规阵列进行子波和频谱对比,结果表明:水深为20 m的条件下,基于尖脉冲子波设计的阵列较常规阵列虚反射效应和陷波点效应的压制效果更好;主峰值、峰-峰值和初泡比分别增大11.6%,12.4%,16.4%;兼顾了高频和低频,有效频宽增大14.5%;能谱展布范围更广,能量下传能力更强,提高了信噪比和分辨率。

基于人工表面等离子激元的宽带谐振天线

针对传统微带和介质谐振天线(DRA)带宽较窄和尺寸较大的问题,提出了一种基于人工表面等离子激元波导谐振腔的宽带天线。该天线人工表面等离子激元(SSPPs)波导由对称的H型单元结构组成,谐振腔由同轴探针馈电,利用波导单元偶模和奇模两种模式的色散特性,实现了天线带宽的显著增大。该天线工作频段为8.8~12.4 GHz,相对带宽为33.9%。在工作频带内,天线的辐射效率大于92%,最大增益达到了6.8 dBi。此外,天线为低剖面结构,整体尺寸较小,结构简单,利于各种无线通信和传感系统的集成。

基于改进T-B法的宽带高斯过程疲劳损伤分析

针对宽带高斯随机应力过程造成的疲劳损伤问题,本文提出一种基于改进Tovo-Benasciutti(T-B)法的疲劳损伤频域分析方法。通过不同参数形式的功率谱进行时域的疲劳损伤分析,针对T-B法中的关键参数bTB提出一个新的非线性函数模型。与原T-B法相比,新提出的函数模型bMTB可以考虑S-N曲线斜率参数m的影响,并以此为基础提出基于改进T-B法的疲劳损伤分析方法。以时域的雨流计数法结果作为基准,分别采用参数化功率谱和真实响应谱进行数值试验,并与现有的多种宽带高斯疲劳损伤分析方法进行对比,验证本文所提出的改进T-B法的准确性和适用性。

铁路5G-R系统的QoS测试方法

考虑到5G-R在铁路通信领域的引入,介绍铁路移动通信系统发展,研究5G-R核心网络架构和铁路三大应用场景,并针对铁路特定场景下的业务传输链路的服务质量(QoS)需求,设定QoS指标性能测试方法,从而前瞻性地布局,保障5G-R通信和列控系统等关键核心业务的传输速率、可靠性和安全性。

Cr3+掺杂的宽带近红外荧光粉及其研究进展

具有非损伤、快速检测特点的近红外光谱技术与近红外成像技术在食品成分检测、癌症早期诊断、脑科学等领域获得了越来越多应用,其面临的技术瓶颈之一就是缺乏一种具有小型化、快速响应特点的宽带近红外光源。为解决该问题,荧光粉转化的宽带近红外LED(pc-LED)逐渐在众多技术方案中脱颖而出。本综述重点总结了宽带近红外pc-LED核心材料Cr 3+掺杂的宽带近红外荧光粉的研究进展,并详细介绍了宽带近红外光源的应用背景及光源种类,总结了Cr 3+的发光特性。本综述针对Cr 3+掺杂的宽带近红外荧光粉需要解决的重要问题展开讨论,包含了效率提升、发射谱带展宽、电声耦合问题和应用探索四个方面,以帮助读者了解该研究课题的现状、面临问题及未来发展趋势。

BSR-2宽频带地震记录仪的研制

介绍了一种完全自主研发的新型数字地震记录仪,系统采用双CPU结构、GPS授时同步与高精度恒温晶振相结合的时钟机制、新型24位A/D、完全超大容量电子固态存储以及内建自测试(BIST)等新技术,非常适合于天然地震的野外流动观测,也可应用在人工源反射、折射地震勘探等其他领域,是一种数据可靠、使用方便、具有较高性能价格比的宽频带地震数据采集系统.

一种基于多层电阻膜的超宽带超材料吸波体

本文提出了一种基于多层电阻膜的超带宽超材料吸波体的设计模型.该吸波体的结构单元由一种环形电阻膜片在含导体底面的平面分层介质基板上多层叠加而成,各层电阻膜片的外形相同,但表面阻值不同.一件四层吸波体的仿真分析结果表明:该吸波体对6.8GHz^59.6GHz频段之间的垂直入射波吸波率均大于90%;同时对入射角为45度的TE和TM斜入射波仍能保持超宽带吸波,具有极化不敏感和宽入射角特性.另外,对不同层次吸波体的分析表明:随着电阻膜片层次的增加,其吸波效果更好,吸波频带变宽,带内吸波效果更稳定.

单层雷达吸波材料研究

通过数值分析确定了单层电损耗吸波材料理想电磁参数,探讨了单层吸波材料的吸波机理。分析表明:单层吸波材料要实现宽频吸收,其电磁参数必须具有频散效应,即随电磁波频率的升高电磁参数有规律的降低,其中ε′.μ′与f2成反比。以羰基铁粉/聚氯乙烯吸波贴片为实例验证了理论分析结果,讨论了常规单层吸波材料性能的影响因素。