Sea Floor Sediment and Its Acouso-Physical Properties in the Southeast Open Sea Area of Hainan Island in China

Acouso-physical properties of sea floor sediments in the southeast offshore sea area of Hainan Island on the northern continental shelf of the South China Sea are analyzed. In many cruises, conductivity-temperature-depth measurements of seawater, measurements of shallow stratum and side-scan sonar have been made. Acoustic parameters, basic sedimentary parameters, physical-mechanical parameters and ¹⁴C age, etc., have been measured. The sediment elastic parameters, including Young's modulus, bulk modulus, constrained modulus, rigidity modulus, Poisson's ratio, Lames constant, etc., have been calculated. Results show that the compression wave velocity of the seafloor sediment in the sea area ranges from 1474–1700 m/s, and there are high and low sound velocity sediment types in the different sea areas; the shear wave velocity is 150–600 m/s; at 100 kHz the sediment sound attenuation is 35–260 dB/m, the sediment density is 1.4–2.0 g/cm³; the sediment porosity is 42–88%. Sound field parameters and describing sound reciprocity between sea and seafloor are described.     

Experimental Studies of Sound Attenuation in Seabed Sediments on Column Sample Length Scale

Seabed sediment microstructure has an influence on its acousto-physical properties, and the properties in a length of the sediment column reflect an aspect of the macroscopic behavior of the microstructure. An original measurement method of the sound attenuation within small distance cross sections in a sediment column, and the corresponding approach in data processing to attain an attenuation factor are detailed in the paper. This method was used to measure the compressional wave in series of points with a small distance in the sediment column, and it is shown that exponential attenuation is a type of compressional wave attenuation model for a sediment column in its full length. It indicates that there are various models of compressional wave attenuation in seabed sediments in the South China Sea after comparison of data from other literature. The method of measuring sound attenuation satisfies the sampling space interval in the acoustical forward and inverse problems in seabed sediments, and the original method provides a new approach for finding out sound attenuation mechanism in seabed sediments on small length scale.     

周期性循环载荷作用下岩石声发射规律试验研究

声发射是岩石等脆性材料内部损伤的伴生现象。在周期性循环载荷作用下通过改变不同应力幅度和不同加载速率对细粒砂岩进行声发射试验研究,探讨了声发射在周期性载荷作用下的声发射规律。研究结果表明,改变上限应力对声发射现象的影响显著,而改变下限应力的影响主要在循环末期,提早了每个循环声发射产生时间;加载速率的增加提高了声发射率,特别是循环过程中主裂纹的形成和扩展阶段,加快了岩石破坏进程;不同应力幅度和加载速率下声发射表现出不同的发展模式,不同模式预示着不同的岩石变形破坏速率。     

汶川8.0级地震前高碑店和宁晋台超低频电磁辐射异常特征分析

2008年5月12日四川省汶川县发生8.0级强烈地震.地震发生前后的几个月,河北省高碑店和宁晋超低频地震电磁观测台记录到高值电磁辐射异常信息,本文对两台记录的异常信息特征进行了分析.     

Subaqueous geothermal activity revealed by lacustrine sediments of the acidic Nakadake crater lake, Aso Volcano, Japan

Lacustrine sediments were sampled from the inaccessible acidic (pH = 0.43) Nakadake crater lake of Aso Volcano, Japan by a simple method. The sediments contain an extremely high content (74 wt.%) of sulfur, which exits as elemental sulfur, gypsum and anhydrite. The abundant elemental sulfur is likely formed by the reaction of SO₂ and H₂S gases and by the SO₂ disproportionation reaction in magmatic hydrothermal system below the crater lake. Based on the sulfur content of sediments and measurements of elevation change of the crater bottom, the sulfur accumulation rate at the Nakadake crater lake was calculated as 250 tonne/day, which is comparable with the SO₂ emission rate (200–600 tonne/day) from the Nakadake crater. The sediments include a small amount (9%) of clear glass shards that are apparently not altered in spite of the high reactivity of hyperacid lake water. This finding suggests that the clear glass shards are fragments of recently emitted magmas from fumaroles on the bottom of the crater lake and the magma emissions continuously occur even in quiescent periods.     

PET/CT新技术应用

PET/CT将PET与CT整合为一体化,是功能显像和解剖显像的有机结合.为了获取经济效益,PET/CT必须在不增加治疗费用的同时具有精确的诊断性,并对患者的治疗方案作出有效的指导.PET/CT由于采用了3D采集与单纯PET相比缩短了图像采集时间,从而使病人的要求得到更大程度的满足,同时也增加了病人的舒适程度,减少了由于采集过程中病人活动导致的出错机率.PET/CT在临床上主要应用于肿瘤学、心脏病学及神经精神医学等领域,在上述领域的中其诊断精确性优势是其他显像方法不可比拟的.在指导肿瘤治疗方面,PET/CT可以通过改善患者的治疗决策而具有重要的卫生经济学价值.     

全球长期减排目标与碳排放权分配原则

全球长期减排目标将对世界未来的碳排放形成严重制约,减排义务的分担原则涉及各国的发展空间,事关根本利益。部分发达国家倡导人均排放趋同原则,回避发达国家的历史责任,中国等发展中国家提出人均累积排放趋同原则,强调公平性。按人均累积排放量计算,发达国家自工业革命以来的CO₂排放量已远超出其到2050年前应有的限额,其当前和今后相当长时期的高人均排放都将继续挤占发展中国家的排放空间。因此,发达国家在哥本哈根会议的中近期减排承诺中必须深度减排,以实现全球长期减排目标下的排放轨迹,并为发展中国家留有必要的发展空间。同时必须对发展中国家给予充足的资金和技术支持,作为对其过度挤占发展中国家发展空间的补偿,使发展中国家能够在可持续发展框架下,提高应对气候变化的能力。我国在对外坚持公平原则,努力争取合理的排放空间的同时,对内要加强向低碳经济转型,努力实现保护全球气候和国内可持续发展的双赢。     

Comparison of the Anthropogenic Emission Inventory for CMIP6 Models with a Country-Level Inventory over China and the Simulations of the Aerosol Properties

Anthropogenic emission inventory for aerosols and reactive gases is crucial to the estimation of aerosol radiative forcing and climate effects.Here,the anthropogenic emission inventory for AerChemMIP,endorsed by CMIP6,is briefly introduced.The CMIP6 inventory is compared with a country-level inventory(i.e.,MEIC)over China from 1986 to 2015.Discrepancies are found in the yearly trends of the two inventories,especially after 2006.The yearly trends of the aerosol burdens simulated by CESM2 using the two inventories follow their emission trends and deviate after the mid-2000s,while the simulated aerosol optical depths(AODs)show similar trends.The difference between the simulated AODs is much smaller than the difference between model and observation.Although the simulated AODs agree with the MODIS satellite retrievals for country-wide average,the good agreement is an offset between the underestimation in eastern China and the overestimation in western China.Low-biased precursor gas of SO₂,overly strong convergence of the wind field,overly strong dilution and transport by summer monsoon circulation,too much wet scavenging by precipitation,and overly weak aerosol swelling due to low-biased relative humidity are suggested to be responsible for the underestimated AOD in eastern China.This indicates that the influence of the emission inventory uncertainties on simulated aerosol properties can be overwhelmed by model biases of meteorology and aerosol processes.It is necessary for climate models to perform reasonably well in the dynamical,physical,and chemical processes that would influence aerosol simulations.     

碳税和碳交易机制的行业减排成本比较优势研究

碳税和碳交易机制是控制温室气体排放的环境管理工具,对工业行业的减排成本造成不同的影响。以污染控制政策的稳态总期望社会成本函数为基础构建碳减排成本函数,比较碳税和碳交易机制下水泥行业减排成本,发现影响两种环境管理工具成本的要素。以广东和山东水泥行业的实证数据进行模拟分析,得到如下结论：当碳价和碳税税率差距不大时,由于碳交易机制需要较高的建设成本,碳税更具成本优势;短期内,由于减排技术投入成本较高,与强制性的行政管理手段相比,碳交易机制更具成本效益;碳价、碳税税率、最佳可获得技术的价格、企业预期、碳交易建设与管理成本都会影响碳交易机制和碳税在减排成本上的比较优势。建议设计互补型碳排放管理政策组合,使碳税和碳交易机制发挥各自的制度优势。     

源自多个大电流源的华东地区地电场空间变化特征

在地震电磁学研究中,电流在地下流动特征与构造关系是一个非常重要的问题.多个强电流源的存在和大范围地电场观测站的分布格局为我们研究这个问题提供了更好的机会.本文通过利用上海及其周边地区4个地点不同的高压换流站接地极向地下注入的大电流(1200~4780A)信号,研究了华东地区8个台站组成的地电场观测台网接收到的附加地电场信号,推进了对地电流在地下传播特征的认识.研究显示:1从幅度特征而言,对于源自不同的大电流信号,各台站观测到的附加地电场信号幅度特征有很大不同,而近处的浦东台只能观测到南桥大电流源的信号而观测不到其他3个大电流源发出的信号,存在着所谓的"敏感点"效应;2对于上海地区4个接地极大电流而言,能够观测到源自它们的附加地电场的台站最远为350km,在更远的台站则观测不到.3从均匀度方面而言,在每个台站对于不同的信号源,记录到的附加地电场信号在各方向上的长极距和短极距信号幅度之比可以有很大变化;4在方位特征上,只有崇明台站接收到的同里接地极和华新接地极大电流信号的计算方位度数与实际方位度数误差最小,分别为0.2°和0.8°.而在距离各个信号源最近的青浦台,这种误差要比崇明台站的大;5极化方向特征显示,在青浦台和崇明台所观测到的附加地电场信号中,存在着同一方向上长、短极距信号极化方向是反向的现象,这与常理相悖,怎样解释该现象有待于今后进一步研究.本文从点电流源与台站测线布局构成的装置系统、大区域介质非均匀性、台站测区以及附近地区的介质细结构的影响三个方面,对上述特征进行了较深入的分析和解释.