Performance of a scintillation detector array operated with LHAASO-KM2A electronics

A scintillation detector array composed of 115 detectors and covering an area of about 20000 m² was installed at the end of 2016 at the Yangbajing international cosmic ray observatory and has been taking data since then. The array is equipped with electronics from Large High Altitude Air Shower Observatory Square Kilometer Complex Array (LHAASO-KM2A) and, in turn, currently serves as the largest debugging and testing platform for the LHAASO-KM2A. Furthermore, the array was used to study the performance of a wide field-of-view air Cherenkov telescope by providing accurate information on the shower core, direction and energy, etc. This work is mainly dealing with the scintillation detector array. The experimental setup and the offline calibration are described in detail. Then, a thorough comparison between the data and Monte Carlo (MC) simulations is presented and a good agreement is obtained. With the even-odd method, the resolutions of the shower direction and core are measured. Finally, successful observations of the expected Moon’s and Sun’s shadows of cosmic rays (CRs) verify the measured angular resolution.     

Decoupling algorithm for evaluating multiple beam damages in steel moment‐resisting frames

Post‐earthquake safety evaluation of steel moment‐resisting frames mainly relies on the inspection of seismic damage to beam–column connections. Recently, in order to evaluate seismic damage of steel connections in a prompt and precise manner, a local damage evaluation method based on dynamic strain responses has been proposed and receives attention. In the evaluation method where strain responses are measured by piezoelectric strain sensors, a strain‐based damage index has been developed for evaluating individual seismic beam damage in a steel frame. However, for a steel frame suffering multiple beam damages, the damage index deteriorates its performance in identifying small damages with the presence of neighboring severe damages because of the moment redistributions induced by larger damages. This paper presents a decoupling algorithm that removes the issue of damage interaction and improves the performance of the damage index. The decoupling algorithm was derived on the basis of damage‐induced moment release and redistribution mechanism. The effectiveness of the decoupling algorithm was numerically and experimentally investigated using a nine‐story steel frame model and a large scale five‐story steel frame testbed that can simulate multiple fractures at beam ends. Copyright © 2016 John Wiley & Sons, Ltd.     

测氡仪器K值使用中存在的问题讨论

通过对水氡观测资料分析认为,标定测氡仪器时,若按<规范>要求当标定的新-原K值相对偏差大于5%时才能使用新K值来计算水氡浓度,容易产生误差积累,出现水氡测值偏低、观测数据"台阶"、及平行样经常超差等现象.应用"无论新-原K值相对偏差是否大于5%都启用新K值"的方法对以往观测资料进行重新计算,与原来数据对比大大降低误差的...     

海洋微生物技术

海洋生物技术学（ＭａｒｉｎｅＢｉｏｔｅｃｈｎｏｌｏｇｙ,或称海洋生物工程学）兴起于本世纪８０年代。海洋微生物技术是海洋生物技术学的一个组成部分。文中就抗生素、抗心血管化合物、抗病毒及抗肿瘤化合物、海洋生物毒素及酶等海洋生物活性物质,生物粘膜和生物污着,海洋污染的生物治理及水产养殖动物病害诊断与防治等海洋微生物技术的最新进展作了比较全面的综述。     

On the effect of the martian crustal magnetic field on atmospheric erosion

Without the shielding of a strong intrinsic magnetic field, the martian atmosphere directly interacts with the impacting solar wind. The neutral constituents of the atmospheric corona can be ionized, and then picked up and accelerated by the magnetic field and convection electric field in the solar wind. A significant fraction of pickup ions escape Mars’ gravitational pull and are lost to space. This non-thermal escape process of heavy species is an important mechanism responsible for atmospheric erosion. While there is a perception that the martian magnetic anomalies are significant for the ionospheric density distribution and the bow shock standoff location, little is known about the quantitative influence of the martian crustal magnetic field on the global distribution of escaping pickup ions. In this paper, we apply a newly developed Monte Carlo ion transport model to resolve the crustal field effect on the pickup oxygen ion distribution around Mars. The background magnetic and electric fields, in which test particles are followed, are calculated using an independent three-dimensional multispecies MHD model. The effects of the crustal magnetic field on particle escape are quantified by varying the crustal field orientation in the model setup and comparing the corresponding test particle simulation results. The comparison is made by turning on or off the crustal field or changing the local time of the strongest field from the dayside to the dawnside. It is found that without the protection of the crustal magnetic field, the total amount of atmospheric escape through the tail region would be enhanced by more than a factor of two. It is shown that the crustal magnetic field not only regionally deflects the solar wind around the martian atmosphere, but also has an important global effect on atmospheric erosion and thus on long-term atmospheric evolution.     

中全新世以来冲绳海槽氧化还原环境重建及其气候效应

通过对位于冲绳海槽黑潮主轴流经区的GHN056-09柱状沉积物进行粒度、常微量元素、AMS 14C分析,获得了中全新世以来粒度和常微量元素随时间变化的高分辨率曲线。结果表明,6235aBP以来研究区沉积环境稳定,沉积物中MnO/Al2O3、U/Th和V/Cr等3个地球化学指标在近6235aBP以来均发生了数次不同程度的波动,大致可以划分为3个阶段：阶段1(1830aBP至今)的生产力和氧化还原程度强烈波动期、阶段2(4000~1830aBP)的低生产力和弱还原期、阶段3(6235~4000aBP)的高生产力和相对较强还原期。中全新世以来地球化学指标可共同识别出的6次极值揭示了同期的相对高生产力和较强还原状态,分别发生在R1(260aBP)、R2(1200aBP)、R3(2125aBP)、R4(2700aBP)、R5(4250aBP)和R6(5700aBP),且与海水温度和黑潮强度关系密切,揭示了中全新世以来冲绳海槽区海气相互作用的区域性响应特征。     

重力约束反演构建郯庐断裂带泗洪浅覆盖区隐伏基岩地质模型

利用重力异常数据建立覆盖区的基岩地质模型往往需要大量的地质与岩石物性资料,同时受地质先验信息、人为因素等干扰严重。运用重力异常钻孔约束反演的方法尝试构建浅覆盖区基岩地质模型,探讨在人为介入较少的情况下快速高效构建包含基岩面起伏特征、断裂展布、密度分布等要素的地质模型的可行性。在郯庐断裂泗洪地区的地质调查实际应用中,对区内布格重力异常采用小波多尺度分解的方法进行基岩面异常场提取,随后联合运用小波断裂分析、线性回归反演、视密度填图等方法构建了该区域的隐伏基岩地质模型。结果显示,在不需要大量地质先验信息的情况下,该系列方法能够快速高效地构建覆盖区地质模型。结果模型能够较好地反映基岩面构造及物性特征,并且细化郯庐断裂带泗洪地区的区域构造特征,对于郯庐断裂地区的构造演化研究具有一定的参考意义,同时为探索较少人为干预的地球物理数据反演覆盖区隐伏基岩的方法研究提供一定的实践价值。     

基于均匀化理论与上限分析的膨胀土滑坡稳定性分析

在膨胀土和滑坡共同作用下,隧道洞口段施工更容易引发地表开裂甚至滑坡等工程灾害,在隧道内采用微型桩群防治滑坡比抗滑桩具有优势。本文基于均匀化理论与上限分析对某高速公路隧道洞口段膨胀土滑坡的稳定性进行计算,并评价微型桩群和削方卸载不同组合方式的处置效果,计算时将微型桩群及桩周土通过均匀化理论等效为符合摩尔库仑强度准则的等效加固体来,以此提高计算效率,最后通过对现场削方+微型桩群加固处置后的滑坡变形监测来验证计算的合理性,得出如下结论：相较于土的强度参数,等效加固体内摩擦角保持不变,黏聚力从26 kPa提高到85.36 kPa。处置前后的滑坡稳定性评价结果表明,不做处理时,滑坡滑动面从滑坡上方岩土交界面延续到隧道洞口前;仅采用微型桩群加固时,滑坡安全系数在1.17左右,滑动面从岩土交界面延续到隧道洞口后;同时采用微型桩群加固和削方卸载时,滑坡安全系数提高到1.26~1.28,滑动面上缘由土石交界面前移。现场变形监测表明地表变形与深层土体变形均不超过3 mm,该措施能保障滑坡的稳定性,同时也验证了计算方法的合理性,可为同类工程提供参考。     

树轮宽度指示的神农架地区过去172年的冬春季温度变化

利用神龙架林区两个样点的巴山冷杉(Abies fargesii Franch)建立了一条新的可靠的树轮年表。该年表与区域2月、3月、4月和6月的温度呈显著正相关关系(P P <0.01)。基于该年表重建了神农架地区过去172年来的冬春季温度变化, 发现过去170多年来共有6个低温时段, 分别为1848~1859年、1869~1874年、1888~1900年、1927~1932年、1938~1973年和1979~1994年。与研究区周边树轮记录的冬春季温度变化的对比发现, 1870s之前本文树轮记录的低温事件与秦岭山脉东部地区树轮所记录的低温事件较一致, 在1920s以后则与大别山地区及江西湖南地区树轮所记录的低温事件较一致。通过对比3条重建序列的趋势变化发现, 神农架地区的温度开始变暖的时间要早于大别山地区与江西湖南地区, 且升温的幅度也更大。最后通过对区域冷期与暖期500hPa高度场的合成分析得出, 区域低温事件主要受乌拉尔高压的影响。     

高分辨率卫星颤振探测补偿的关键技术方法与应用

卫星平台颤振是高分辨率卫星在轨运行普遍存在的复杂现象,会影响卫星的测图精度和成像质量。本文提出了综合多传感器数据处理的卫星颤振探测与补偿技术方法,根据多光谱影像、三线阵影像、密集地面控制和姿态测量数据进行了颤振探测,采用像方补偿和姿态补偿两种方式进行了颤振补偿。利用本文提出的技术对资源三号卫星的平台颤振问题进行了处理和分析,试验结果验证了所提出的方法用于颤振探测与补偿的有效性与可靠性。颤振变化规律分析表明资源三号卫星颤振的频率保持在0.6~0.7Hz的范围内,而颤振幅值从在轨早期的1个像素下降到0.4个像素以下并趋于平稳。