The Impact of Model Based Offset Scaling Technique on the Amplitude Variation with Offset Responses from 3D Seismic Data Acquired from the Tano Basin, Offshore Ghana

Amplitudes have been found to be a function of incident angle and offset. Hence data required to test for amplitude variation with angle or offset needs to have its amplitudes for all offsets preserved and not stacked. Amplitude Variation with Offset (AVO)/Amplitude Variation with Angle (AVA) is necessary to account for information in the offset/angle parameter (mode converted S-wave and P-wave velocities). Since amplitudes are a function of the converted S- and P-waves, it is important to investigate the dependence of amplitudes on the elastic (P- and S-waves) parameters from the seismic data. By modelling these effects for different reservoir fluids via fluid substitution, various AVO geobody classes present along the well and in the entire seismic cube can be observed. AVO analysis was performed on one test well (Well_1) and 3D pre-stack angle gathers from the Tano Basin. The analysis involves creating a synthetic model to infer the effect of offset scaling techniques on amplitude responses in the Tano basin as compared to the effect of unscaled seismic data. The spectral balance process was performed to match the amplitude spectra of all angle stacks to that of the mid (26°) stack on the test lines. The process had an effect primarily on the far (34° - 40°) stacks. The frequency content of these stacks slightly increased to match that of the near and mid stacks. In offset scaling process, the root mean square (RMS) amplitude comparison between the synthetic and seismic suggests that the amplitude of the far traces should be reduced relative to the nears by up to 16%. However, the exact scaler values depend on the time window considered. This suggests that the amplitude scaling with offset delivered from seismic processing is only approximately correct and needs to be checked with well synthetics and adjusted accordingly prior to use for AVO studies. The AVO attribute volumes generated were better at resolving anomalies on spectrally balanced and offset scaled data than data delivered from conventional processing. A typical class II AVO anomaly is seen along the test well from the cross-plot analysis and AVO attribute cube which indicates an oil filled reservoir.

基于SBAS-InSAR与Offset-Tracking的色东普流域灾前形变探究

利用SAR偏移量追踪(offset-tracking)技术获取冰川形变作为SBAS-InSAR的补充,采用2种技术计算2018-01~10色东普流域灾前形变,联合分析灾前形变特征及影响因素。结果表明,色东普流域冰川与沟道在2018-10-17冰崩灾害发生前已出现形变;冰川主要形变区形变趋势表现为加速-平缓-加速,7~9月形变量达到-7.69 m;沟道内堆积物长期呈下滑趋势,7月后与冰川均加速形变;气温升高是冰崩碎屑流灾害发生的主导因素。联合SBAS-InSAR与offset-tracking技术能够满足不同形变量级的监测需求,可用于冰崩灾害的早期识别与形变反演,为青藏高原地区冰崩灾害防治提供参考。

Permanent Magnet Temperature Estimation for PMSMs Using Virtual Position-offset Injection

This paper proposes a virtual position-offset injection based permanent magnet temperature estimation approach for permanent magnet synchronous machines(PMSMs). The concept of virtual position-offset injection is mathematically transforming the machine model to a virtual frame with a position-offset. The virtual frame temperature estimation model is derived to calculate the permanent magnet temperature(PMT) directly from the measurements with computation efficiency. The estimation model involves a combined inductance term, which can simplify the establishment of saturation compensation model with less measurements. Moreover, resistance and inverter distorted terms are cancelled in the estimation model, which can improve the robustness to the winding temperature rise and inverter distortion. The proposed approach can achieve simplified computation in temperature estimation and reduced memory usage in saturation compensation. While existing model-based approaches could be affected by either the need of resistance and inverter information or complex saturation compensation. Experiments are conducted on the test machine to verify the proposed approach under various operating conditions.

Analytical Determination of Size and Location of Roadside Horizontal Sightline Offsets for Compound Curves

AASHTO’s guideline for geometric design of highways and similar guidelines require that roadside areas on the inside of horizontal curves be cleared of high objects to provide stopping sight distance. The guidelines have analytical models for determining the extent of clearance, known as the horizontal sightline offset or clearance offset, for simple curves. Researchers in the past have developed analytical models for clearance offsets for spiraled and reverse curves. Very few researchers developed analytical models for available sight distances for compound curves. Still missing are models for horizontal sightline offsets and locations of the offsets for compound curves. The objective of this paper is to present development of analytical models and charts for determining horizontal sightline offsets and their locations for compound curves. The paper considers curves whose component arcs are individually shorter than stopping sight distance. The resulting models and the charts have been verified with accurate values determined using graphical methods. The models and the charts will find application in geometric design of highway compound curves.

Offset restoration in total hip arthroplasty:Important:A current review

Normal vertical and horizontal offset is essential for hip biomechanics,muscle functioning and gait pattern.Total hip arthroplasty(THA)should aim to restore normal offset with implantation of femoral and acetabular components.This would be possible with proper preoperative planning,templating and ensuring implant options are available for offset restoration.Templating is essential for understanding the vertical and horizontal offset change,especially in hip arthritis presenting late with significant limb length discrepancy at THA.Planning should include appropriate soft tissue releases and the use of ideal implants to achieve restoration of horizontal and vertical offset.Under correction of horizontal offset at THA for fracture neck of femur could result in abductor fatigue,limp and increased wear.Restoration of horizontal offset is imperative at THA for a fractured neck of the femur to achieve optimal abductor function.Horizontal offset is necessary for optimal abductor muscle tension and function.Revision THA for acetabular bone loss would require hip center restoration with the acetabular and femoral offset correction to achieve limb length correction and abductor length.The inability to achieve vertical and horizontal offset correction could lead to dislocation or signs of abductor fatigue.Careful vertical and horizontal femur offset restoration is required for normal hip biomechanics,decreased wear and increased longevity.

Near resonance vibration isolation on a levered-dual response(LEDAR)Coulomb-damped system by differential preloads/offsets in linear springs

The levered-dual response(LEDAR)Coulomb-damped system attains near resonant vibration isolation by differential preloads/offsets in linear springs.It takes the advantages of both the preloads/offsets in linear springs and the guiderail friction for realizing different levels of vibration isolation.The isolation capacities are investigated on the strategies with both the horizontal and vertical guiderails,with the horizontal rail only,and without guiderails.The compressive preloads generally result in the consumption of most of the initial excitation energy so as to overcome the potential threshold.The isolation onsets at the frequency ratio of 1∓0.095 on the left-hand side(LHS)and the right-hand side(RHS)of the lever are relative to the load plate connector.The observed near resonant isolation thus makes the LEDAR system a candidate for the isolation of the mechanical systems about resonance while opening a path for simultaneous harvesterisolation functions and passive functions at extreme frequencies.

The Effect of Lateral Offset Distance on the Aerodynamics and Fuel Economy of Vehicle Queues

The vehicle industry is always in search of breakthrough energy-saving and emission-reduction technologies.In recent years,vehicle intelligence has progressed considerably,and researchers are currently trying to take advantage of these developments.Here we consider the case of many vehicles forming a queue,i.e.,vehicles traveling at a predetermined speed and distance apart.While the majority of existing studies on this subject have focused on the influence of the longitudinal vehicle spacing,vehicle speed,and the number of vehicles on aerodynamic drag and fuel economy,this study considers the lateral offset distance of the vehicle queue.The group fuel consumption savings rate is calculated and analyzed.As also demonstrated by experimental results,some aerodynamic benefits exist.Moreover,the fuel consumption saving rate of the vehicle queue decreases as the lateral offset distance increases.

A Residual Frequency Offset Estimation Method Based on Range Migration Fitting

Recently,researchers have proposed an emitter localization method based on passive synthetic aperture.However,the unknown residual frequency offset(RFO)between the transmit-ter and the receiver causes the received Doppler signal to shift,which affects the localization accu-racy.To solve this issue,this paper proposes a RFO estimation method based on range migration fitting.Due to the high frequency modulation slope of the linear frequency modulation(LFM)-mod-ulation radar signal,it is not affected by RFO in range compression.Therefore,the azimuth time can be estimated by fitting the peak value position of the pulse compression in range direction.Then,the matched filters are designed under different RFOs.When the zero-Doppler time obtained by the matched filters is consistent with the estimated azimuth time,the given RFO is the real RFO between the transceivers.The simulation results show that the estimation error of azimuth distance does not exceed 20 m when the received signal duration is not less than 3 s,the pulse repe-tition frequency(PRF)of the transmitter radar signal is not less than 1 kHz,the range detection is not larger than 1000 km,and the signal noise ratio(SNR)is not less than-5 dB.

Modulation Recognition with Frequency Offset and Phase Offset over Multipath Channels

Modulation recognition becomes unreliable at low signal-to-noise ratio(SNR)over fading channel.A novel method is proposed to recognize the digital modulated signals with frequency and phase offsets over multi-path fading channels in this paper.This method can overcome the effects of phase offset,Gaussian noise and multi-path fading.To achieve this,firstly,the characteristic parameters search is constructed based on the cyclostationarity of received signals,to overcome the phase offset,Gaussian white noise,and influence caused by multi-path fading.Then,the carrier frequency of the received signal is estimated,and the maximum characteristic parameter is searched around the integer multiple carriers and their vicinities.Finally,the modulation types of the received signal with frequency and phase offsets are classified using decision thresholds.Simulation results demonstrate that the performance of the proposed method is better than the traditional methods when SNR is over 5dB,and that the proposed method is robust to frequency and phase offsets over multipath channels.

A new method for coseismic offset detection from GPS coordinate time series

Currently,the extraction of coseismic offset signals primarily relies on earthquake catalog data to determine the occurrence time of earthquakes.This is followed by the process of differencing the average GPS coordinate time series data,with a time interval of 3 to 5 days before and after the earthquake.In the face of the huge amount of GPS coordinate time series data today,the conventional approach of relying on earthquake catalog data to assist in obtaining coseismic offset signals has become increasingly burdensome.To address this problem,we propose a new method for automatically detecting coseismic offset signals in GPS coordinate time series without an extra earthquake catalog for reference.Firstly,we pre-process the GPS coordinate time series data for filtering out stations with significant observations missing and detecting and removing outliers.Secondly,we eliminate other signals and errors in the GPS coordinate time series,such as trend and seasonal signals,leaving the coseismic offset signals as the primary signal.The resulting coordinate time series is then modeled using the first-order difference and data stacking method.The modeling method enables automatic detection of the coseismic offset signals in the GPS coordinate time series.The aforementioned method is applied to automatically detect coseismic offset signals using simulated data and the Searles Valley GPS data in California,USA.The results demonstrate the efficacy of our proposed method,successfully detecting coseismic offsets from vast amounts of GPS coordinate time series data.

Reconstructing in vivo spatially offset Raman spectroscopy of human skin tissue using a GPU-accelerated Monte Carlo platform

As one type of spatially offset Raman spectroscopy(SORS), inverse SORS is particularly suited to in vivo biomedical measurements due to its ring-shaped illumination scheme. To explain inhomogeneous Raman scattering during in vivo inverse SORS measurements, the light–tissue interactions when excitation and regenerated Raman photons propagate in skin tissue were studied using Monte Carlo simulation. An eight-layered skin model was first built based on the latest transmission parameters. Then, an open-source platform, Monte Carlo e Xtreme(MCX), was adapted to study the distribution of 785 nm excitation photons inside the model with an inverse spatially shifted annular beam. The excitation photons were converted to emission photons by an inverse distribution method based on excitation flux with spatial offsets Δs of 1 mm, 2 mm, 3 mm and 5 mm. The intrinsic Raman spectra from separated skin layers were measured by continuous linear scanning to improve the simulation accuracy. The obtained results explain why the spectral detection depth gradually increases with increasing spatial offset, and address how the intrinsic Raman spectrum from deep skin layers is distorted by the reabsorption and scattering of the superficial tissue constituents. Meanwhile, it is demonstrated that the spectral contribution from subcutaneous fat will be improved when the offset increases to 5 mm, and the highest detection efficiency for dermal layer spectral detection could be achieved when Δs = 2 mm. Reasonably good matching between the calculated spectrum and the measured in vivo inverse SORS was achieved, thus demonstrating great utility of our modeling method and an approach to help understand the clinical measurements.

Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of loading.Moreover,the explicit solver was run in Abaqus to create the finite element model.The numerically obtained test results were compared with the experimental to check the accuracy of the modelling.The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus.Furthermore,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was examined.The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading.Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance.Also,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption.However,inscribe circle diameter had a negative influence on the ballistic resistance.Also,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions.The energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.

Massive Unsourced Random Access Under Carrier Frequency Offset

Unsourced random access(URA)is a new perspective of massive access which aims at supporting numerous machine-type users.With the appearance of carrier frequency offset(CFO),joint activity detection and channel estimation,which is vital for multiple-input and multiple-output URA,is a challenging task.To handle the phase corruption of channel measurements under CFO,a novel compressed sensing algorithm is proposed,leveraging the parametric bilinear generalized approximate message passing framework with a Markov chain support model that captures the block sparsity structure of the considered angular domain channel.An uncoupled transmission scheme is proposed to reduce system complexity,where slot-emitted messages are reorganized relying on clustering unique user channels.Simulation results reveal that the proposed transmission design for URA under CFO outperforms other potential methods.

Shaped Offset Quadrature Phase Shift Keying Based Waveform for Fifth Generation Communication

Fifth generation(5G)wireless networks must meet the needs of emerging technologies like the Internet of Things(IoT),Vehicle-to-everything(V2X),Video on Demand(VoD)services,Device to Device communication(D2D)and many other bandwidth-hungry multimedia applications that connect a huge number of devices.5G wireless networks demand better bandwidth efficiency,high data rates,low latency,and reduced spectral leakage.To meet these requirements,a suitable 5G waveform must be designed.In this work,a waveform namely Shaped Offset Quadrature Phase Shift Keying based Orthogonal Frequency Division Multiplexing(SOQPSK-OFDM)is proposed for 5G to provide bandwidth efficiency,reduced spectral leakage,and Bit Error Rate(BER).The proposed work is evaluated using a real-time Software Defined Radio(SDR)testbed-Wireless open Access Research Platform(WARP).Experimental and simulation results show that the proposed 5G waveform exhibits better BER performance and reduced Out of Band(OOB)radia-tion when compared with other waveforms like Offset Quadrature Phase Shift Key-ing(OQPSK)and Quadrature Phase Shift Keying(QPSK)based OFDM and a 5G waveform candidate Generalized Frequency Division Multiplexing(GFDM).BER analysis shows that the proposed SOQPSK-OFDM waveform attains a Signal to Noise Ratio(SNR)gain of 7.2 dB at a BER of 10�3,when compared with GFDM in a real-time indoor environment.An SNR gain of 8 and 6 dB is achieved by the proposed work for a BER of 10�4 when compared with QPSK-OFDM and OQPSK-OFDM signals,respectively.A significant reduction in OOB of nearly 15 dB is achieved by the proposed work SOQPSK-OFDM when compared to 16 Quadrature Amplitude Modulation(QAM)mapped OFDM.

高速列车尾车垂向偏置对列车气动性能影响

在长期的高速列车运营过程中,极易形成前后车辆的不同形式偏置,造成列车气动性能改变,甚至可能引发行车平稳性问题,极大影响乘坐舒适性和安全性。以高速列车尾车作为研究对象,探究尾车上下偏置时,高速列车尾部流场变化以及气动特性。基于SST k-ω双方程湍流模型,采用数值仿真方法研究了350 km/h高速列车尾车无偏置、尾车下降20 mm、尾车下降40 mm、尾车下降60 mm、尾车上升20 mm、尾车上升40 mm以及尾车上升60 mm 7种工况下列车的气动性能,分析高速列车气动阻力的变化规律,揭示了不同垂向位移下高速列车尾部流场特性以及列车表面压力分布情况。研究结果表明:高速列车尾部垂向位移对列车整体气动阻力影响较小,但对高速列车气动阻力分布以及流场特性造成一定影响。当尾车偏置位移达到60 mm时,列车车体气动阻力相对于无偏置工况分别降低了-1.11%和2.64%,转向架气动阻力相对无偏置情况下分别降低了11.35%和-17.43%。此外,尾车偏置对列车近尾流区域流场结构有一定影响,尾车鼻锥下方排障器周围漩涡结构由双漩涡结构向单漩涡结构转变;鼻尖处漩涡结构随着尾车高度下降而增大,随着尾车高度上升而逐渐变小。本研究结果丰富了列车尾部偏置情况下的相关研究,对列车检修以及CR450高速列车设计等具有重要指导意义。

考虑风电爬坡灵活调节的碳捕集电厂低碳经济调度

为实现“双碳”目标,风电等可再生能源的使用是减少碳排放的根本途径,而碳捕集电厂是降低碳排放的直接手段。但风电具有与生俱来的波动性,风电的骤升骤降会影响碳捕集电厂“电碳耦合”特性,从而对碳捕集效果带来不利影响。而储液罐通过增减自身溶液量可近似地存储释放能量,为解决上述问题提供了可能。该文首先搭建碳捕集电厂数学模型,分析储液罐通过增减溶液量带来的储放能量与碳捕集设备能耗之间的关联,研究储液罐的双向调节能力;然后,提出上爬坡碳超前补偿和下爬坡碳滞后补偿调度策略,双向调节储液罐使碳捕集电厂电碳解耦;接着,构建跟随风电爬坡进行调节的低碳经济调度模型;最后,对含碳捕集电厂、高碳电厂和风电场的电力系统进行仿真,证明所提方法的有效性。

基于MEMS陀螺的高温随钻定向测斜仪研究

针对油气井测量时所面临的小孔径、超深井、温度范围广、温度变化率高、工作时间长等挑战,研究了基于MEMS陀螺仪的定向测斜仪,设计了MEMS陀螺定向测斜仪软硬件系统.为确保该环境下的测量精度提出了一种动态温度补偿方案,并采用基于小波滤波多尺度分析的方法对动态温变环境下陀螺输出信号进行去噪滤波处理,以实现定向测斜仪系统的测量精度.论文给出了定向测斜仪硬件系统方案、定向测斜算法、小波多尺度滤波算法.测试结果表明:该系统在常温和动态温变环境下井斜方位角精度优于±2°,井斜角精度优于±0.1°,工作温度最高150℃,可适应我国深层油气井勘探开发的应用场景需求.

孤岛微电网多虚拟同步发电机频率无差协调控制策略

传统虚拟同步发电机的频率控制为有差控制,且虚拟惯量的引入使得虚拟同步发电机呈现二阶振荡特性,导致孤岛微电网多虚拟同步发电机并联系统在受到负荷扰动时面临频率偏移和有功超调的问题。针对此,提出了一种多虚拟同步发电机频率无差协调控制方法。该方法包含了兼具有功精确分配的频率无差调节控制和阻尼改进控制两部分,通过利用母线频率全局一致的“通信”效果,以分散式的形式协调系统内各台虚拟同步发电机,可主动消除微电网频率稳态偏差且实现各台虚拟同步发电机按照容量承担负荷有功功率,并抑制系统的有功超调。最后,通过仿真和实验验证了所提控制方法的有效性。

基于智能化管理的压力传感器计量检测方法

由于压力传感器的计量检测数据处理工作量大、流程繁琐,提出一种基于智能化管理的压力传感器计量检测方法。首先以互联网为基础核心,构建计量检测智能化管理系统;去除被检压力传感器与压力标准器间的高度差,记录压力传感器的零点漂移;通过计算正、反行程的校准曲线与工作曲线,得到压力传感器的计量检测结果。通过检测实验证明,所提方法得出的压力传感器在不同温度点的正、反行程的3个循环测量值拟合度高,检测得出的压力传感器的灵敏度偏移与零点漂移极小,计量检测结果符合测试能力指数要求,具有非常高的检测精度。

主轴热偏移特性检测与影响分析

主轴的热偏移误差直接影响数控机床的定位精度及加工质量。针对数控机床主轴温升及热偏移误差的测试问题,利用磁吸式温度传感器、激光测试仪对主轴温度变化与各方向热偏移误差进行测量,了解机床主轴实际工况,收集主轴温升数据及热平衡时间、主轴热偏移空间状态,分析主轴温升与热偏移误差随测试组数的变化关系。实验结果表明:主轴温升与测试组数的增加呈正比例关系,高转速最大温升12.65℃,明显高于低转速温升8.55℃;主轴各方向热偏移误差随温升而变大,其中高转速下误差变化更剧烈,高、低转速下的最大热偏移分别为35.37μm和15.26μm。本研究成果为以后探寻误差成因及优化补偿设计提供了数据支撑。