Modeling air gun signatures in marine seismic exploration considering multiple physical factors

Based on analyzing the limit of Ziolkowski＇s bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects of physical factors,such as heat transfe across the bubble wall,air gun port throttling,vertical rise of the bubble,fluid viscosity,and the existence of the air gun body were all taken into account in the new model.Compared with Ziolkowski＇s model,the signatures simulated by the new model,with small peak amplitude and rapid decay of bubble oscillation,are more consistent with actual signatures The experiment analysis indicates：（1）gun port throttling controls the peak amplitude of ai gun pulse;（2）since the hydrostatic pressure decreases when the bubble rises,the bubble oscillation period changes;（3）heat transfer and fluid viscosity are the main factors tha explain the bubble oscillation damping.

Facial Features of an Air Gun Array Wavelet in the Time-Frequency Domain Based on Marine Vertical Cables

Air gun arrays are often used in marine energy exploration and marine geological surveys.The study of the single bubble dynamics and multibubbles produced by air guns interacting with each other is helpful in understanding pressure signals.We used the van der Waals air gun model to simulate the wavelets of a sleeve gun of various offsets and arrival angles.Several factors were taken into account,such as heat transfer,the thermodynamically open quasi-static system,the vertical rise of the bubble,and air gun post throttling.Marine vertical cables are located on the seafloor,but hydrophones are located in seawater and are far away from the air gun array vertically.This situation conforms to the acquisition conditions of the air gun far-field wavelet and thus avoids the problems of ship noise,ocean surges,and coupling.High-quality 3D wavelet data of air gun arrays were collected during a vertical cable test in the South China Sea in 2017.We proposed an evaluation method of multidimensional facial features,including zeropeak amplitude,peak-peak amplitude,bubble period,primary-to-bubble ratio,frequency spectrum,instantaneous amplitude,instantaneous phase,and instantaneous frequency,to characterize the 3D air gun wave field.The match between the facial features in the field and simulated data provides confidence for the use of the van der Waals air gun model to predict air gun wavelet and facial features to evaluate air gun array.

Post-Traumatic Necrohemorragic Pancreatitis Caused by an Air Gun

Penetrating abdominal trauma is the main cause of pancreatic lesions and delay in diagnosis or treatment can increase morbimortality. We present a case of acute necrohemorrhagic pancreatitis (ANHP) secondary to airgun injury associated with pulmonary embolism caused by the projectile in a 36 year old man. He underwent urgent surgery, appreciating pancreatic contusion but not visualizing the projectile, located by CT scan 3mm from the inferior vena cava. The patient underwent further surgery 48 hours later for necrosectomy and the insertion of an irrigation tube, due to ANHP after the migration of the projectile into the lung. This case underlines the clinical relevance of pancreatic lesion in patients with a penetrating abdominal trauma, the diagnostic difficulty and the surgical strategy, as well as the repercussions of the migration of a foreign body through the blood stream, crossing the right heart chambers and becoming lodged in the lung.

Phase Characteristic Analysis of Continuous Depth Air-Gun Source Wavelet

Air guns are important sources for marine seismic exploration. Far-field wavelet of air gun arrays, as a necessary parameter for pre-stack processing and source models, plays an important role during marine seismic data processing and interpretation. When an air gun fires, it generates a series of air bubbles. Similar to onshore seismic exploration, the water forms a plastic fluid near the bubble; the farther the air gun is located from the measurement, the more steady and more accurately represented the wavelet will be. In practice, hydrophones should be placed more than 100 m from the air gun; however, traditional seismic cables cannot meet this requirement. On the other hand, vertical cables provide a viable solution to this problem. This study uses a vertical cable to receive wavelets from 38 air guns and data are collected offshore Southeast Qiong, where the water depth is over 1000 m. In this study, the wavelets measured using this technique coincide very well with the simulated wavelets and can therefore represent the real shape of the wavelets. This experiment fills a technology gap in China.

Case Report: Air Gun Pellet Injury to the Cribriform Plate of a Young Male

Air guns and rifles are usually considered to be harmless. Even though these firearms are categorized as toys, injuries with these are quite common in children and adolescents. The most common reason for these types of injuries is accidents and negligence. In this case report we present a 17-year-old male, admitted to the emergency department with a 5 mm incision below his left eye. In the CT imaging a pellet was seen lodged in the cribriform plate. It pierced through the ethmoid sinus. The patient was admitted to the inpatient clinic and managed conservatively with antibiotherapy. A review of literature was performed to find out the best strategy to reach an optimized outcome and evaluate probable complications.

Fire Distribution of Integrated Missile-gun Air Defense System Based on Earlier Damage Criterion

The fire distribution can be divided into weapon assignment and firing time scheduling. The criterion of weapon allocation is that a target with greater threat has higher priority. And the criterion of firing time scheduling is that a target can be damaged with the expected probability before a specific time. A fire distribution scheme and a program for the integrated missile-gun air defense system based on a criterion of earlier damage were presented. An example was taken to illustrate its effectiveness.

Multi-port cavity model and low-level RF systems design for VHF gun

Very high frequency(VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavity, the VHF gun requires high stability in the amplitude and phase of the cavity field. However, the gun is microwave powered by two solid-state power sources through two separate power couplers. The input difference between the two power couplers will influence the stability of the cavity field. To systematically study this influence and obtain measurement formulae, a multi-port VHF gun LCR circuit model is built and analyzed. During the warm-up condition, the cavity structure will be deformed due to the large-scale change in the cavity temperature. Then, the deformation will result in cavity resonant frequency changes. To prevent the mechanic tuner from suffering damages due to the frequent and long-distance movement for correcting the cavity resonant frequency, a self-excited loop(SEL) control system is considered for changing the loop phase and make the loop frequency follow the resonant frequency. In this study, a steady-state model of the VHF gun cavity is built for obtaining the optimal input coupler coefficient and the stability requirement of the forward voltage. Then, the generator-driven resonator and SEL control system, which combine with the VHF multiport modeling, are modeled and simulated. The simulated results show that the SEL system can perfectly operate in the process of condition and warm-up.

Research on arc root stagnation when small current is interrupted in self-excited circuit breaker

The self-excited DC air circuit breaker(SE-DCCB)has been widely used in urban rail transit due to its excellent stability.It can realize forward and reverse interruption,but has difficulty interrupting small currents due to the phenomenon of arc root sticking at the entrance of the arc chamber in the splitting process,which is known as arc root stagnation.A coupling model of the self-excited magnetic field and magnetohydrodynamics is established for the SE-DCCB with the traditional structure.The magnetic field,temperature and airflow distribution in the arc chamber are investigated with an interrupting current of 150 A.The simulation results show that the direction and magnitude of the magnetic blowout force are the dominant factors in the arc root stagnation.The local high temperature of the arc chamber due to arc root stagnation increases the obstruction effect of the airflow vortex on the arc root movement,which significantly increases the arc duration time of small current interruption.Based on the research,the structure of the magnetic conductance plate of the actual product is improved,which can improve the direction and magnitude of the magnetic blowout force at the arc root so as to restrain the development of the airflow vortex effectively and solve the problem of arc root stagnation when the small current is interrupted.The simulation results show that the circuit breaker with improved structure has a better performance for a small current interruption range from 100 A to 350 A.

Test Apparatus for Performance Evaluation of Compressed Air End-Use Applications

Compressed air is an integral utility part of industrial utility systems. Any improvement in compressed air system will lead to reduction in utility cost. The effectiveness of utilization side of compressed air is usually dependent upon operator’s discretion. There are no performance testing methods available for testing existing end use equipments. A test apparatus for estimation of compressed air flow based on measurement of pressure reduction in a fixed volume cylinder in a given time is developed. The test apparatus is easy to build and simple to operate in an industrial environment. This can be used for measuring performance of any pneumatic end-use equipment and for benchmarking the performance. The test apparatus was used in a foundry for quantifying the performance of the old and new blow guns.

Gunlink 4000气枪控制器水下单元的组成及UTM的现场维护

Gunlink 4000是全新一代气枪控制器,通过近场检波器和激发传感器进行监测,提高了放炮精度和气枪自激的监控。它的水下部分主要由GFSM单元和UTM单元组成,这两个单元将深度、压力、近场子波等重要参数传输到控制系统。恶劣的海上勘探条件容易造成水下控制端故障频发,对UTM进行现场维护,能有效提高生产效率。

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。

基于能量守恒的气枪主动震源激发实验震级计算

分别运用Baker公式、Kinney公式、Broad公式计算甘肃刘家峡气枪主动源一次常规实验激发所释放的能量,并利用能量与震级之间的经验公式,估算一次常规实验产生地震的震级。通过分析刘家峡主动源实验场附近固定数字测震台站记录的单次激发数据发现,气枪激发时所释放的能量并未完全转换为地震波,如气枪主气室在爆破瞬间并非完全绝热,有部分能量随着热量传递而散失,故通过能量守恒方法计算的震级略大。实验结论与Kinney公式计算结果的一致性较好,符合实验实际工况条件。

浅海地震采集缆—源空间组合对激发子波特性的影响分析

地震资料分辨率低是当前渤海油田深层地震勘探面临的突出问题,而改善该问题首先须在地震采集尤其是震源设计方面寻求突破,但鲜有针对渤海浅水条件下的拖缆与震源空间组合研究的报道。为此,首先分析了渤海浅水条件下气枪脉冲的传播特征,确定了影响气枪脉冲传播的主要因素;再基于非理想气体条件气枪子波模型对浅水条件下单枪子波进行模拟,研究了考虑缆鬼波时子波及其频谱特征,提出采用考虑缆鬼波的子波对震源性能进行评价的方法;然后以渤海油田渤中地区实际地理和地质条件为基础,设计了不同缆—源沉放深度组合、震源平面展布的模拟试验,系统分析了渤海浅水条件下拖缆、震源空间组合对子波及其频谱的影响规律;最后将文中总结的规律认识和震源设计技术应用于渤中二次数据采集,并对比该区新、老三维拖缆单炮数据,验证了所提方法的正确性,对渤海浅水区气枪震源的优化设计及评价具有指导意义。

海洋气枪远场子波模拟技术及应用

在海洋地震勘探中,获取精确气枪震源子波对地震数据提高分辨率处理和震源质量监控等具有重要意义。针对已有的气枪震源子波模拟算法不能充分考虑气枪实时状态,模拟的子波和实际情况差异较大的问题,提出了基于近场水听器信号,考虑通过单枪激发试验测量的水听器相对灵敏度、通过气泡上浮计时试验和枪阵实时导航数据计算的气泡相对运动,以及考虑海面虚反射等因素,在频率域模拟气枪震源远场子波的方法。并测试了这几种因素对模拟结果的影响程度和适用条件。与常规基于震源设计参数理论模拟方法进行了实际数据应用对比,结果表明,所提出的远场子波模拟方法模拟出的远场子波能反映气枪震源真实激发状态和条件,具有高保真性,用于地震数据子波处理后能更好地压制气泡效应,大幅提高地震资料的分辨率,具有重要的实用意义。

软式内镜活检管腔干燥方法及时间研究

目的探讨软式内镜活检管腔的干燥方法和干燥时间。方法将临床诊疗使用过的胃镜随机分为5组,结肠镜随机分为6组,每组均进行60次实验。所有胃镜和结肠镜经规范清洗和消毒后,第1组活检管腔常规使用压力气枪持续吹气30 s进行干燥;剩余各组先用内镜干燥机干燥5 min,再使用压力气枪对活检管腔持续吹气30、40、50、60 s(胃镜)或30、40、50、60、70 s(结肠镜)。干燥时间结束时,使用氯化钴试纸判断内镜管腔的干燥程度。结果胃镜常规吹气30 s的干燥合格率为20.0%,结肠镜为18.3%;胃镜干燥机干燥5 min+吹气60 s,结肠镜干燥机干燥5 min+吹气70 s,干燥合格率均为100%;胃镜、结肠镜各组组内干燥合格率比较,差异有统计学意义(均P<0.05)。结论软式内镜用内镜干燥机干燥5 min的基础上,胃镜活检管腔吹气时间60 s,肠镜活检管腔吹气时间70 s,可以保证内镜活检管腔的干燥效果。

涡扇发动机吞雹试验

为研究某型涡扇发动机吞雹能力,按照CCAR-33R2标准33.78(a)条开展了整机吞雹试验方法研究及验证。梳理了试验流程,确定了试验条件,对发动机、试车台等进行了分析,开展了防护装置、摄影装置、投射装置设计,并对冰雹的制作方法进行了研究。通过投射装置实现了冰雹向发动机的投射,同时设计了试验前的校靶试验和空炮试验,通过校靶试验保证了投射的速度和准确性,通过空炮试验测试了投射装置对发动机进气的影响,又通过高速摄影验证了冰雹投射的速度和撞击位置的准确性。发动机吞入冰雹过程中推力出现短时减小,随后恢复了稳定工作,吞雹后发动机排气温度下降约2%~3%,转差变化约-0.6%~0.2%,推力下降约0.1%~1.6%;其余参数无明显变化,通过低压测点时域信号采集了风扇部分的冲击响应;试验后分解检查5片风扇叶片进气边变形,未出现掉块情况,未发现可能危及飞行安全的结构损坏,验证了某型涡扇发动机的吞雹适航符合性。

循环流化床锅炉SNCR脱硝技术浅析

锅炉脱硝装置采用“选择性非催化还原(SNCR)”技术,脱硝还原剂采用9.5%浓度氨水(原先为20%尿素溶液)。每台机组脱硝出口都设有一套CEMS测量装置,并在三台机组的净烟道汇合后设有一套CEMS测量装置作为烟囱排放监测。本文对锅炉SNCR脱硝系统注意要点做了简介,并简述了在调试过程中出现的问题。

高压气枪在实验室条件下的同步性能测试方法

针对高压气枪在阵列中使用时的同步性能要求,介绍了气枪震源系统的组成原理、同步控制原理和影响同步性能的因素;详细阐述了气枪阵列中激发电路对电磁阀激发时刻的控制,及在可变延时控制电路的干预下实现高压气枪阵列的同步控制方法;提出了在实验室条件下开展同步性能测试的方法,并以容积150 in 3高压气枪为例,组建了实验室条件下的高压气枪同步性能测试系统,得到连续20组测试数据,通过分析得到其激发的时间偏差在±0.498 ms内,符合勘探同步性需求,激发一致性较好,气枪工作稳定,可用于气枪阵列的组建。

气枪震源在地球深部结构探测中的应用研究进展

介绍了气枪震源的发展历史、工作原理、激发参数、性能指标,及气枪震源的最新发展动态.由于气枪震源的优越性,使得气枪震源成为新兴的、环保的、绿色的人工震源,在地球物理学中得到迅速推广和广泛应用,如国外的LARSE和SIGHT计划,及国内的南海东北部海陆联合勘探计划,都是利用气枪震源进行深部地球物理探测的成功实例.通过对气枪震源的容积能量、激发频率、沉放深度等的分析和讨论,探讨气枪震源在地球深部结构探测中的进一步应用.

气枪阵列子波数值模拟

气枪阵列作为震源具有很多优点,在海上地震勘探领域应用已久。国内对气枪的理论研究不多,认识不足。本文探讨了国际上主要的几种气枪单枪理论模型,同时对于气枪相干特性进行了较为深入的研究,提出了气枪阵列子波的算法。结合现场实际资料,进行了对比和验证,得到了较为接近实际情况的结果。