Bearing splitting and near-surface source ranging in the direct zone of deep water

Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.

Active source seismic imaging on near-surface granite body:case study of siting a geological disposal repository for high-level radioactive nuclear waste

In order to research whether it is suitable to set a geological disposal repository for high-level radioactive nuclear waste into one target granite body,two active source seismic profles were arranged near a small town named Tamusu,Western China.The study area is with complex surface conditions,thus the seismic exploration encountered a variettraveltimey of technical difculties such as crossing obstacles,de-noising harmful scattered waves,and building complex near-surface velocity models.In order to address those problems,techniques including cross-obstacle seismic geometry design,angle-domain harmful scattered noise removal,and an acoustic wave equation-based inversion method jointly utilizing both the and waveform of frst arrival waves were adopted.The fnal seismic images clearly exhibit the target rock’s unconformable contact boundary and its top interface beneath the sedimentary and weathered layers.On this basis,it could be confrmed that the target rock is not thin or has been transported by geological process from somewhere else,but a native and massive rock.There are a few small size fractures whose space distribution could be revealed by seismic images within the rock.The fractures should be kept away.Based on current research,it could be considered that active source seismic exploration is demanded during the sitting process of the geological disposal repository for nuclear waste.The seismic acquisition and processing techniques proposed in the present paper would ofer a good reference value for similar researches in the future.

Spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River during the period 2002–2011 based on the Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E) data

Detecting near-surface soil freeze-thaw cycles in high-altitude cold regions is important for understanding the Earth＇s surface system, but such studies are rare. In this study, we detected the spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River（SRYR） during the period 2002–2011 based on data from the Advanced Microwave Scanning Radiometer for the Earth Observing System（AMSR-E）. Moreover, the trends of onset dates and durations of the soil freeze-thaw cycles under different stages were also analyzed. Results showed that the thresholds of daytime and nighttime brightness temperatures of the freeze-thaw algorithm for the SRYR were 257.59 and 261.28 K, respectively. At the spatial scale, the daily frozen surface（DFS） area and the daily surface freeze-thaw cycle surface（DFTS） area decreased by 0.08% and 0.25%, respectively, and the daily thawed surface（DTS） area increased by 0.36%. At the temporal scale, the dates of the onset of thawing and complete thawing advanced by 3.10（±1.4） and 2.46（±1.4） days, respectively; and the dates of the onset of freezing and complete freezing were delayed by 0.9（±1.4） and 1.6（±1.1） days, respectively. The duration of thawing increased by 0.72（±0.21） day/a and the duration of freezing decreased by 0.52（±0.26） day/a. In conclusion, increases in the annual minimum temperature and winter air temperature are the main factors for the advanced thawing and delayed freezing and for the increase in the duration of thawing and the decrease in the duration of freezing in the SRYR.

Seismoelectric waves in a borehole excited by an external explosive source

The conversion of energy between seismic and electromagnetic wave fields has been described by Pride's coupled equations in porous media. In this paper, the seismoelectric field excited by the explosive point source located at the outside of the borehole is studied. The scattering fields inside and outside a borehole are analyzed and deduced under the boundary conditions at the interface between fluid and porous media. The influences of the distance of the point source, multipole components of the eccentric explosive source, and the receiving position along the axis of vertical borehole, on the converted waves inside the borehole are all investigated. When the distance from the acoustic source to the axis of a borehole is far enough, the longitudinal and coseismic longitudinal wave packets dominate the acoustic and electric field, respectively. The three components of both electric field and magnetic field can be detected, and the radial electric field is mainly excited and converted by the dipole component. Owing to the existence of borehole, the electric fields and magnetic fields in the borehole are azimuthal. The distance from the point where the maximum amplitude of the axial components of electric field is recorded, to the origin of coordinate indicates the horizontal distance from the explosive source to the axis of vertical borehole.

Major hazard sources analysis and prevention measures of packaging emulsion explosive production line

Emulsion explosive with favorable water-resistance performance,storage performance and detonation stability has been widely used in all over the world.The development actuality and production technique characteristics of emulsion explosive in China were introduced firstly.Taken the technique characteristics of packaging emulsion explosive into account,major hazard sources of emulsion explosive production line were analyzed.Finally,prevention measures based on inherent safety of emulsion explosive production were put forward.

3D near-surface P-wave velocity structure imaging with Distributed Acoustic Sensing and electric hammer source

Distributed Acoustic Sensing(DAS) is an emerging technique for ultra-dense seismic observation, which provides a new method for high-resolution sub-surface seismic imaging. Recently a large number of linear DAS arrays have been used for two-dimensional S-wave near-surface imaging in urban areas. In order to explore the feasibility of three-dimensional(3D) structure imaging using a DAS array, we carried out an active source experiment at the Beijing National Earth Observatory. We deployed a 1 km optical cable in a rectangular shape, and the optical cable was recast into 250 sensors with a channel spacing of 4 m. The DAS array clearly recorded the P, S and surface waves generated by a hammer source. The first-arrival P wave travel times were first picked with a ShortTerm Average/Long-Term Average(STA/LTA) method and further manually checked. The P-wave signals recorded by the DAS are consistent with those recorded by the horizontal components of short-period seismometers. At shorter source-receiver distances, the picked P-wave arrivals from the DAS recording are consistent with vertical component recordings of seismometers, but they clearly lag behind the latter at greater distances.This is likely due to a combination of the signal-to-noise ratio and the polarization of the incoming wave. Then,we used the Tomo DD software to invert the 3D P-wave velocity structure for the uppermost 50 m with a resolution of 10 m. The inverted P-wave velocity structures agree well with the S-wave velocity structure previously obtained through ambient noise tomography. Our study indicates the feasibility of 3D near-surface imaging with the active source and DAS array. However, the inverted absolute velocity values at large depths may be biased due to potential time shifts between the DAS recording and seismometer at large source-receiver distances.

Seismic Geothermal Resource Exploration based on CPU/GPU Collaborative Parallel Prestack Time Migration

Geothermal resources exist in complex and comprehensive geological settings. In the current study, we proposed a CPU/GPU collaborative parallel prestack time migration methodology for geothermal resource exploration. First, seismic geological conditions in Xian County were obtained based on an analysis of drill cores for further seismic evaluation. Then,combined with the analysis of two-dimensional seismic data in the adjacent area, a test section with three seismic survey lines were designed to explore the geological structure of the study area. In the study area, the seismic data were derived through the multiple coverage reflection wave exploration method with explosive ignition in deep wells and high coverage frequency observations. Finally, we employed CPU/GPU collaborative parallel prestack time migration technology to analyze the obtained seismic data for geothermal resource evaluation. The favorable areas of karst fissure heat storage in Middle–Upper Proterozoic Jixianian and Paleozoic Cambrian–Ordovician rocks were inferred together with two preferred recommended exploration holes.

Evaluation Cases of Hazardous Article Explosion Risk of Methylal Construction Project

Along with development of economy in China, industrial production accidents continued to occur, which caused huge losses to people＇s lives and property safety, and also caused serious pollution to the environment. Organic chemical industry products, by-products and most of the raw material were flammable, explosive or toxic hazardous articles, which had major accident risk potentially. So it was necessary to evaluate the fire and explosion risk of organic chemical projects. Combining with the evaluation cases of some organic chemical construction project, the relevant contents of the evaluation of hazardous articles explosion risk of the industry was discussed.

Sources of IR Radiation in the Earth’s Atmosphere in Connection with the PeTa Effect

The PeTa (Perelman-Tatartchenko) effect is the radiation of the energy of a first-order phase transition during the transition from a less condensed phase to a more condensed one. The effect was independently discovered by M. Perelman and the author of this paper. Six papers on the PeTa effect have been published in this journal over the past nine years. They are devoted to the development of PeTa models to explain the following phenomena: IR radiation from cold surfaces, cavitation luminescence/sonoluminescence (CL/SL), laser-induced bubble luminescence (LIBL), and vapor bubble luminescence (VBL) in underwater geysers. This paper describes the sources of PeTa radiation in the Earth’s atmosphere. These sources of infrared radiation have been investigated by numerous research groups, but their interpretation either does not exist at all, or it is erroneous. The following phenomena are specifically considered: PeTa radiation during the formation of clouds and fog;a pulse laser based on the PeTa radiation;condensation explosions as sources of PaTa radiation;measurement of the concentration of water vapor in the atmosphere using PeTa radiation;atmospheric scintillation of infrared radiation in the atmosphere due to the PeTa effect;PeTa radiation as a source of comfort for the igloo;the influence of PeTa radiation on living organisms;PeTa radiation due to characteristics of tropical storms;PeTa radiation as a possible precursor to earthquakes. The problem of global warming, which worries everyone, as it turns out, is also associated with the PeTa effect.

Safety research in the gasification process of novel multi-thermal-source coal gasifier

In order to collect the gas safely produced in the gasification process of the novel multi-thermal-source coal gasifier,based on its gasification skill and the characteristics of the products,this paper analyzes the possible dangers in the gasification process,devises the gasifier eruption and explosion experiments,explores the conditions of gasifier eruption and gas explosion,studies their effects on the gasification process and establishes safe operation measures.Gasifier eruption hazard occurs easily in the gasification process of one-thermal-source coal gasifier when MSiO2 is far higher than that in the normal adjuvant.The gas permeability in the gasifier is not the same and the power supply is too large.However,similar conditions in the gasification of multi-thermal-source coal gasifier do not produce a gasifier eruption accident so easily.When it erupts,the gasifier should be stopped and then cooled down naturally or inert gas can be sprayed on the gasifier to cool it off,and thus gas explosion can be avoided.There is a possibility of direct gas explosion,but it can be avoided when the gas in the gas collecting space is replaced slowly by supplying a small amount of power or the inert gas fills the space in the previous gasification.The time a fire is lit is strictly controlled,the gas is drawn in by using the aspirator pump,and the gasifier pressure is kept in the state of micro-positive pressure in the middle and later gasification process.The conclusion is that the gasification process of the novel multi-thermalsource coal gasifier is safe according to normal operation rules.

户内燃气爆炸事故技术调查内容探讨及案例

近年来户内燃气爆炸事故多发。迅速查明事故发生的技术原因是科学定责及事故防范的主要依据。基于户内燃气爆炸事故灾害演化过程及调查经验,总结提出如下6项技术调查内容:确定泄漏燃气类型、明确泄漏源位置、分析泄漏原因、计算泄漏至周围空间内的燃气浓度、判断点火源(爆源)、评估爆炸威力及灾害。该文分别叙述各技术内容的调查、分析、计算及评估方法,并基于真实事故案例,给出各技术内容的具体实施情况。研究结果可为户内燃气爆炸事故调查及防控提供参考。

基于BP神经网络的水中双爆源爆炸冲击波峰值压力预测模型研究

为了获得水中等质量两爆源同步爆炸时冲击波耦合中心的峰值压力计算模型,利用Autodyn计算得到不同药量和爆距下的峰值压力数据.一方面根据量纲分析确定的函数形式拟合数据从而获得峰值压力的计算公式;另一方面对药量、爆距及峰值压力三类数据进行对数变换和归一化,并将其分为训练集和测试集,然后将训练集代入BP神经网络进行训练,得到结构相对简单、均方误差最小的BP神经网络预测模型.结果表明:公式计算结果和BP神经网络模型计算得到的峰值压力与实际值吻合较好,公式计算值与实际值的平均相对误差为1.08%,BP神经网络预测值与实际值的平均相对误差为0.52%,与公式计算相比,BP神经网络能够以更少的数据样本容量实现更高的精度预测.

基于FPGA的主动声源控制系统

随着水下潜艇隐身技术的迅速发展,水面舰艇面临的挑战日益严峻,对水下目标的主动探测提出了新的要求和挑战。将爆炸声源作为发射声源,设计了一套基于FPGA的主动声源控制系统。该系统以FPGA作为控制核心,采用RS232串口通信,收到上位机发送的起爆指令后进行引爆。与传统的主动声纳发射换能器相比,除了成本、功耗与体积降低以外,声源级更高,具有爆炸声源的全指向性,更便于小平台搭载。仿真与水下实验结果表明,该系统在接收到上位机发送的起爆指令后可实现水下爆炸声源有序可控的引爆,同时通过MEMS矢量水听器进行爆炸声源数据采集,经计算可得爆炸声源级为193.93 dB。

退役锂电池带电破碎安全风险研究进展

随着新能源行业的快速发展,锂电池需求量急剧增加,同时退役锂电池产生量也越来越大,从保护环境和资源再利用的角度考虑,对退役锂电池的安全稳定回收极具现实意义。基于此,介绍了湿式破碎、低温破碎、气体保护破碎等带电破碎工艺路线的原理和优缺点,从燃烧和爆炸必须具备的三要素(可燃物、助燃剂、点火源)出发,总结了带电破碎过程中燃烧爆炸的影响因素及规律,并探讨了安全控制策略。

双爆源水下爆炸对圆柱壳结构的毁伤特性研究

[目的]旨在充分研究多种毁伤元对目标毁伤的模式,分析双爆源水下爆炸对圆柱壳结构的毁伤效应。[方法]首先,建立圆柱壳有限元模型,采用任意拉格朗日-欧拉(ALE)方法对单/双爆源水下爆炸下圆柱壳的毁伤特性展开研究;然后,从破口面积、最大垂向位移和塑性应变区域面积等特征参数方面评价结构的毁伤效果,并以500 kg TNT装药为例进行计算分析。[结果]结果显示,对于间距为1 m的双爆源水下爆炸,同等当量的双爆源相比单爆源的爆炸会对圆柱壳外板造成更严重的毁伤,但对圆柱壳内板的毁伤不如单爆源;对于间距大于3 m的双爆源水下爆炸,随着间距的增加,爆炸对圆柱壳结构的毁伤效果逐渐减弱。[结论]通过计算不同初始参数下水下爆炸对圆柱壳结构的毁伤,所获取的单/双爆源水下爆炸对圆柱壳结构的毁伤规律结果可为增强水下作战武器威力提供参考。