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 ...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.展开更多
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...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.展开更多
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 math...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.展开更多
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 ...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.展开更多
The Mw 9.0 Tohoku-Oki earthquake that hit the mainland Japan on 11 th March, 2011 had resulted a devastating Tsunami due to an active thrusting between the Pacific and the North American Plates. Static and kinematic o...The Mw 9.0 Tohoku-Oki earthquake that hit the mainland Japan on 11 th March, 2011 had resulted a devastating Tsunami due to an active thrusting between the Pacific and the North American Plates. Static and kinematic offsets at the offshore epicentre of the Mw 9.0 event remain unanswered and being investigated along with their near and far field limiting distances from the epicentre. Accordingly, offset measurements from 60 continuously operating IGS and GEONET GNSS stations were radially classified from the epicentre and interpreted with analytical models to find their linear offset decay rates. Co-and post-seismic static positional anomaly offsets of sixty days show almost all near field stations had strong or appreciable eastward or south eastward static shifts. Near stations(<250 km) showed both kinematic and static offsets. GEONET station ’0175’ showed maximum resultant static offset of-4.5 m, which diminishes approximately 1-2 cm at far sites like SMST and AIRA. Characteristic decay duration(’b’) of the mean kinematic co-seismic shift(’a’)of near field stations was 17.28 s during earthquake hours with an EW component shift >1.5 m. Spatial models of projected N-S static and kinematic offsets show their asymmetrical distributions around the epicentre with maximum model offset of-1.84 m displaced towards south at-45 km north of the epicentre. The Tohoku-Oki earthquake produced a resultant kinematic offset of-10.2 m towards East at its offshore epicentre;while the estimated near field static offset is ~9.82 m. However, both estimates are bigger than double the resultant offset measured value(~4.3 m) in the Japanese mainland using GPS. The difference in the kinematic and static near field offsets highlight that the near surface had elastic or in-elastic kinematic strain dissipation as against the lithospheric level viscoelastic static response, which resulted rapid kinematic strain release(1.12 cm/km)within the limiting radius of ~220 km from the Tohoku-Oki epicentre.展开更多
Lateral clearance on the inside of horizontal curves is required by all geometric design guidelines in order to provide at least stopping sight distance. There already exist graphical models, analytical models, and de...Lateral clearance on the inside of horizontal curves is required by all geometric design guidelines in order to provide at least stopping sight distance. There already exist graphical models, analytical models, and design charts for determining minimum clearance offsets to meet the requirement. Some of these models determine the offsets based on constant design sight distance values on the assumption that drivers negotiate horizontal curves at constant speed. Therefore, those models are suitable for sites where there is no difference in speeds between tangent and curved sections. Past studies have reported that there are sites where drivers decelerate on entering horizontal curves and accelerate on departing from the curves. At those sites stopping sight distance for a given driver varies with driver location due to variable speed. This paper presents an analytical model and a chart for determining minimum offsets needed to provide desired sight distances at horizontal curves with variable operating speeds. At those sites the offsets yield roadside clearance boundaries that have transition arcs with performances that are similar to those of elliptical arcs. Therefore, practitioners may choose to use elliptical equations or equations and the chart developed herein. Results of this study will be of value to practitioners in the area of roadside design.展开更多
The aim of this study is the geomorphological analysis of neotectonic deformation in the Avaj region in the NW part of the Iranian Plateau. We use observations from detailed field surveys and the analysis of digital e...The aim of this study is the geomorphological analysis of neotectonic deformation in the Avaj region in the NW part of the Iranian Plateau. We use observations from detailed field surveys and the analysis of digital elevation model(DEM) and satellite images(Landsat-7 ETM+, 30-m resolution) to explore a new E-W trending strike-slip fault system in the study area. The major active faults of the Avaj region are the NW-SE trending Avaj and Hassanabad fault zones. The Avaj Fault is a SWdipping reverse fault with a transport toward NE and the Hassanabad Fault is a NE-dipping reverse fault that has moved Paleozoic rocks over Cenozoic sedimentary units. Moreover, there are some E-W trending left-lateral strike-slip faults which cut Late Quaternary deposits. The relationship between the NW-SE and E-W faults indicates that the slip at the termination of the NW-SE faults changes from reverse to left-lateral strike-slip faults. The activity of the left-lateral faults has formed a series of offsets and displacements in drainage paths. These left-lateral faults probably initiated in 5±2 Ma because of the convergence between the Central Iran and the South Caspian blocks.展开更多
Emissions trading schemes(ETSs)have been a central component of international climate change policies,as a carbon pricing tool to achieve emissions reduction targets.Forest carbon offset credits have been leveraged in...Emissions trading schemes(ETSs)have been a central component of international climate change policies,as a carbon pricing tool to achieve emissions reduction targets.Forest carbon offset credits have been leveraged in many ETSs to efficiently meet emission reduction targets,yet there is little knowledge about the perceptions,experiences,and challenges associated with the forest carbon offsetting in existing and pilot ETS.Given that the future inclusion of forest carbon offset in ETS management activities and policies will require strong support and acceptability among the institutions and experts involved in ETS,this study explores the experiences and lessons learned with 16 globally engaging experts representing major existing ETSs(North America,Europe,and New Zealand)and Chinese pilot ETSs towards the inclusion of forestry offsets,major concerns and challenges with existing implementation models.Findings revealed that many respondents particularly from North America,New Zealand,and Chinese pilot systems portrayed positive attitudes toward the inclusion of forestry carbon offsets and its role in contributing to a viable ETS,while European experts were not supportive.Respondents cited leakage,permanence,additionality,and monitoring design features as the major challenges and concerns that inhibit the expansion and inclusion of forest carbon offsetting.Respondents from Chinese pilot schemes referenced a unique set of challenges related to implementation,including the increasing cost of afforestation and reforestation projects,the uncertainty in the future supply and demand for their national Certified Emissions Reduction(CER)scheme and landowner engagement.Existing and future ETSs should learn from and address the challenges experienced by global experts and carbon pricing mechanisms to design,evaluate,or enhance their forest carbon offset programs for an effective and viable system that successfully contributes to GHG mitigation practices globally.We recommend inclusion of forest carbon offsets at the early stages of ETS improves the perceptions and experience of policy makers and practitioners toward the success and potential of forestry offsets in ETS ensuring familiarity and confidence in the mechanism.展开更多
The correction for antenna phase center is considered in processing Global Positioning System(GPS)data collected from a network of GPS ultra-short baselines.Compared with the leveling measurements,the GPS results show...The correction for antenna phase center is considered in processing Global Positioning System(GPS)data collected from a network of GPS ultra-short baselines.Compared with the leveling measurements,the GPS results show that the relative vertical offsets for the pairs of GPS receiver antenna phase centers still exist,although absolute calibration of the antenna phase center variations(PCVs)has been considered.With respect to the TPS CR.G3antenna,the relative vertical offset for the LEI AT504 antenna is-8.4 mm,the offset for the ASH701945C_M antenna is 5.5 mm,and those for the ASH700936E_C and ASH701945B_M antennas are approximately between-2 mm and-3 mm.The relative offsets for the same type of antennas are approximately 1 mm.By correcting the absolute PCVs,the existing relative offset becomes negligible for horizontal positioning.展开更多
Design guidelines require that high objects on the inside of horizontal curves be cleared so as to provide sufficient sight distance. An example of the guidelines that require such clearance is the AASHTO’s Green Boo...Design guidelines require that high objects on the inside of horizontal curves be cleared so as to provide sufficient sight distance. An example of the guidelines that require such clearance is the AASHTO’s Green Book. The Green Book has an analytical model for determining minimum clearance for a given design sight distance. The model is well suited for middle sections of long curves. Applying such clearance to sections near beginnings and ends of the curves and to sections where there is reverse of curvature will result in over-clearance. Over-clearance implies extra cost of earthwork where highways pass in cut zones. To avoid such extra costs the guideline suggests using the graphical method to determine exact clearance offsets. The graphical method is accurate but it is also tedious and time consuming. This study developed analytical models for efficiently determining clearance offsets that match the offsets determined with the graphical method. The offsets are ordinates from driver paths to flat roadside spirals that make the boundary of the roadside area to clear. Mathematical equations for the spirals comprise of terms related to highway speed (in the form of design sight distance), curve features, and driver locations. In turn, these terms define magnitudes of the offsets to the spirals. Combination of the terms results in many parameters to the extent of making difficult development of design charts for offsets. However, examining suitability of published offset charts for simple curves as estimates of offsets for sites with reverse curves leads to finding that the charts are suitable as long as the reverse curves have common tangents that are at least as long as 25% of design sight distance. For reverse curves with no common tangents, offset charts have been developed and presented in this paper. Practitioners can use these charts or the derived equations to determine clearance offsets for new sites as well as for existing sites that are deficient in design sight distance.展开更多
As one of the most important geometric parameters for a PC-type fiber connector end face, apex offset can contribute to high insertion loss and high back-reflection reading. A novel measurement method for the paramete...As one of the most important geometric parameters for a PC-type fiber connector end face, apex offset can contribute to high insertion loss and high back-reflection reading. A novel measurement method for the parameter, connector rotating-π method, is proposed. With the method, the apex offset of a common connector end face is measured. The result is compared with that measured by a Norland 3000 fiber connector end face interferometer. It is found that the difference between two results is 1.8μm. Meantime, the influences of relevant error resources on apex offset measurement under rotating-π method and apex-core method are respectively analyzed, and two error equations are derived. The analytical result shows that, compared with apex-core method, if two additional sub-tilts of axis within and in the direction perpendicular to principal plane caused by its rotation are not bigger than the original axis tilt angle, the max. measurement error will then be reduced by at least 22.5% with rotating-π method. The practicability of the method is confirmed by the experiments.展开更多
The magnetic levitation transportation system is one of the potential applications of high-Tc superconducting (HTS) maglev system. The prototype HTS magnetic levitation system is composed of one HTS bulk and a permane...The magnetic levitation transportation system is one of the potential applications of high-Tc superconducting (HTS) maglev system. The prototype HTS magnetic levitation system is composed of one HTS bulk and a permanent magnet railway (PMR). The maglev transportation system performance is influenced by the maximum levitation force, the maximum guidance force and the maximum of external applied magnetic flux density. The applied magnetic field distribution also needs to be considered carefully. In the paper, the magnetic levitation force of cylindrical HTS bulk over PMR is experimentally studied. During the experiment, symmetrical PMR and Halbach PMR are used separately. The levitation force-gap loops of different lateral offset of the HTS bulk above PMRs are obtained experimentally. The results show that the HTS bulk levitation performance is tightly relative to the external applied magnetic field distribution. The maximum magnetic levitation forces of HTS bulk above symmetrical PMR decrease linearly with the lateral offset increasing. When the lateral offset changes from 0 mm to 25 mm, the maximum magnetic levitation forces of HTS bulk above Halbach PMR increase with the lateral offset increasing. When the lateral offset exceeds the center of the Halbach PMR by 25 mm, the maximum force decreases rapidly with the increase of the lateral offset of the bulk sample.展开更多
Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the la...Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces.Here,we proposed a modified method to calculate band offsets for such systems,in which the core energy level shifts caused by heterovalent effects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as transitions,respectively.Taking the Si and III-V systems as examples,the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems,and are much closer to the experimental values for the large-lattice-mismatched and heterovalent systems.Furthermore,by systematically studying the heterojunctions of Si and III-V semiconductors along different directions,it is found that the band offsets of Si/InAs and Si/InSb systems in[100],[110]and[111]directions belong to the type I,and could be beneficial for silicon-based luminescence performance.Our study offers a more reliable and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors,and could provide theoretical support for the design of the high-performance silicon-based light sources.展开更多
The problem of estimating the carrier frequency offsets in Multiple-Input Multiple-Output (MIMO) systems with distributed transmit antennas is addressed. It is supposed that the transmit antennas are distributed while...The problem of estimating the carrier frequency offsets in Multiple-Input Multiple-Output (MIMO) systems with distributed transmit antennas is addressed. It is supposed that the transmit antennas are distributed while the receive antennas are still centralized, and the general case where both the time delays and the frequency offsets are possibly different for each transmit antenna is considered. The channel is supposed to be frequency flat, and the macroscopic fading is also taken into consideration. A carrier frequency offset estimator based on Maximum Likelihood (ML) is proposed, which can separately estimate the frequency offset for each transmit antenna and exploit the spatial diversity. The Cramer-Rao Bound (CRB) for synchronous MIMO (i.e., the time delays for each transmit antenna are all equal) is also derived. Simulation results are given to illustrate the per- formance of the estimator and compare it with the CRB. It is shown that the estimator can provide satisfactory frequency offset estimates and its performance is close to the CRB for the Signal-to-Noise Ratio (SNR) below 20dB.展开更多
Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS)-based thin film solar cells usually use Cd S as a buffer layer, but due to its smaller band gap(2.4 e V), Cd S film has been replaced with higher band gap materials. The cadmium zinc s...Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS)-based thin film solar cells usually use Cd S as a buffer layer, but due to its smaller band gap(2.4 e V), Cd S film has been replaced with higher band gap materials. The cadmium zinc sulfide(Cd Zn S) ternary compound has a higher band gap than other compounds, which leads to a decrease in window absorption loss. In this paper, the band offsets at Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS) heterointerface are calculated by the first-principles, densityfunctional and pseudopotential method. The band offsets at Cd_(1-x)Zn_x S/CZTS heterointerface are tuned by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy, the calculated valence band offsets are small, which is consistent with the commonanion rule. The favorable heterointerface of type-I with a moderate barrier height(< 0.3 e V) can be obtained by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy between 0.25 and 0.375.展开更多
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 coordina...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.展开更多
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 fad...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.展开更多
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 du...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.展开更多
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 gu...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.展开更多
文摘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.
文摘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.
基金supported in part by the National Natural Science Foundation of China under Grant 52105079 and 62103455。
文摘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.
基金This study was financially supported by the National Natural Science Foundation of China(52072156)the Postdoctoral Foundation of China(2020M682269).
文摘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.
文摘The Mw 9.0 Tohoku-Oki earthquake that hit the mainland Japan on 11 th March, 2011 had resulted a devastating Tsunami due to an active thrusting between the Pacific and the North American Plates. Static and kinematic offsets at the offshore epicentre of the Mw 9.0 event remain unanswered and being investigated along with their near and far field limiting distances from the epicentre. Accordingly, offset measurements from 60 continuously operating IGS and GEONET GNSS stations were radially classified from the epicentre and interpreted with analytical models to find their linear offset decay rates. Co-and post-seismic static positional anomaly offsets of sixty days show almost all near field stations had strong or appreciable eastward or south eastward static shifts. Near stations(<250 km) showed both kinematic and static offsets. GEONET station ’0175’ showed maximum resultant static offset of-4.5 m, which diminishes approximately 1-2 cm at far sites like SMST and AIRA. Characteristic decay duration(’b’) of the mean kinematic co-seismic shift(’a’)of near field stations was 17.28 s during earthquake hours with an EW component shift >1.5 m. Spatial models of projected N-S static and kinematic offsets show their asymmetrical distributions around the epicentre with maximum model offset of-1.84 m displaced towards south at-45 km north of the epicentre. The Tohoku-Oki earthquake produced a resultant kinematic offset of-10.2 m towards East at its offshore epicentre;while the estimated near field static offset is ~9.82 m. However, both estimates are bigger than double the resultant offset measured value(~4.3 m) in the Japanese mainland using GPS. The difference in the kinematic and static near field offsets highlight that the near surface had elastic or in-elastic kinematic strain dissipation as against the lithospheric level viscoelastic static response, which resulted rapid kinematic strain release(1.12 cm/km)within the limiting radius of ~220 km from the Tohoku-Oki epicentre.
文摘Lateral clearance on the inside of horizontal curves is required by all geometric design guidelines in order to provide at least stopping sight distance. There already exist graphical models, analytical models, and design charts for determining minimum clearance offsets to meet the requirement. Some of these models determine the offsets based on constant design sight distance values on the assumption that drivers negotiate horizontal curves at constant speed. Therefore, those models are suitable for sites where there is no difference in speeds between tangent and curved sections. Past studies have reported that there are sites where drivers decelerate on entering horizontal curves and accelerate on departing from the curves. At those sites stopping sight distance for a given driver varies with driver location due to variable speed. This paper presents an analytical model and a chart for determining minimum offsets needed to provide desired sight distances at horizontal curves with variable operating speeds. At those sites the offsets yield roadside clearance boundaries that have transition arcs with performances that are similar to those of elliptical arcs. Therefore, practitioners may choose to use elliptical equations or equations and the chart developed herein. Results of this study will be of value to practitioners in the area of roadside design.
文摘The aim of this study is the geomorphological analysis of neotectonic deformation in the Avaj region in the NW part of the Iranian Plateau. We use observations from detailed field surveys and the analysis of digital elevation model(DEM) and satellite images(Landsat-7 ETM+, 30-m resolution) to explore a new E-W trending strike-slip fault system in the study area. The major active faults of the Avaj region are the NW-SE trending Avaj and Hassanabad fault zones. The Avaj Fault is a SWdipping reverse fault with a transport toward NE and the Hassanabad Fault is a NE-dipping reverse fault that has moved Paleozoic rocks over Cenozoic sedimentary units. Moreover, there are some E-W trending left-lateral strike-slip faults which cut Late Quaternary deposits. The relationship between the NW-SE and E-W faults indicates that the slip at the termination of the NW-SE faults changes from reverse to left-lateral strike-slip faults. The activity of the left-lateral faults has formed a series of offsets and displacements in drainage paths. These left-lateral faults probably initiated in 5±2 Ma because of the convergence between the Central Iran and the South Caspian blocks.
基金funded by the China Green Carbon Foundation and the Faculty of Forestry,University of British Columbia。
文摘Emissions trading schemes(ETSs)have been a central component of international climate change policies,as a carbon pricing tool to achieve emissions reduction targets.Forest carbon offset credits have been leveraged in many ETSs to efficiently meet emission reduction targets,yet there is little knowledge about the perceptions,experiences,and challenges associated with the forest carbon offsetting in existing and pilot ETS.Given that the future inclusion of forest carbon offset in ETS management activities and policies will require strong support and acceptability among the institutions and experts involved in ETS,this study explores the experiences and lessons learned with 16 globally engaging experts representing major existing ETSs(North America,Europe,and New Zealand)and Chinese pilot ETSs towards the inclusion of forestry offsets,major concerns and challenges with existing implementation models.Findings revealed that many respondents particularly from North America,New Zealand,and Chinese pilot systems portrayed positive attitudes toward the inclusion of forestry carbon offsets and its role in contributing to a viable ETS,while European experts were not supportive.Respondents cited leakage,permanence,additionality,and monitoring design features as the major challenges and concerns that inhibit the expansion and inclusion of forest carbon offsetting.Respondents from Chinese pilot schemes referenced a unique set of challenges related to implementation,including the increasing cost of afforestation and reforestation projects,the uncertainty in the future supply and demand for their national Certified Emissions Reduction(CER)scheme and landowner engagement.Existing and future ETSs should learn from and address the challenges experienced by global experts and carbon pricing mechanisms to design,evaluate,or enhance their forest carbon offset programs for an effective and viable system that successfully contributes to GHG mitigation practices globally.We recommend inclusion of forest carbon offsets at the early stages of ETS improves the perceptions and experience of policy makers and practitioners toward the success and potential of forestry offsets in ETS ensuring familiarity and confidence in the mechanism.
基金supported by the Science for Earthquake Resilience(XH14070Y,XH15064Y)the China NationalSpecial Fund for Earthquake Scientific Research in Public Interest(201208009)
文摘The correction for antenna phase center is considered in processing Global Positioning System(GPS)data collected from a network of GPS ultra-short baselines.Compared with the leveling measurements,the GPS results show that the relative vertical offsets for the pairs of GPS receiver antenna phase centers still exist,although absolute calibration of the antenna phase center variations(PCVs)has been considered.With respect to the TPS CR.G3antenna,the relative vertical offset for the LEI AT504 antenna is-8.4 mm,the offset for the ASH701945C_M antenna is 5.5 mm,and those for the ASH700936E_C and ASH701945B_M antennas are approximately between-2 mm and-3 mm.The relative offsets for the same type of antennas are approximately 1 mm.By correcting the absolute PCVs,the existing relative offset becomes negligible for horizontal positioning.
文摘Design guidelines require that high objects on the inside of horizontal curves be cleared so as to provide sufficient sight distance. An example of the guidelines that require such clearance is the AASHTO’s Green Book. The Green Book has an analytical model for determining minimum clearance for a given design sight distance. The model is well suited for middle sections of long curves. Applying such clearance to sections near beginnings and ends of the curves and to sections where there is reverse of curvature will result in over-clearance. Over-clearance implies extra cost of earthwork where highways pass in cut zones. To avoid such extra costs the guideline suggests using the graphical method to determine exact clearance offsets. The graphical method is accurate but it is also tedious and time consuming. This study developed analytical models for efficiently determining clearance offsets that match the offsets determined with the graphical method. The offsets are ordinates from driver paths to flat roadside spirals that make the boundary of the roadside area to clear. Mathematical equations for the spirals comprise of terms related to highway speed (in the form of design sight distance), curve features, and driver locations. In turn, these terms define magnitudes of the offsets to the spirals. Combination of the terms results in many parameters to the extent of making difficult development of design charts for offsets. However, examining suitability of published offset charts for simple curves as estimates of offsets for sites with reverse curves leads to finding that the charts are suitable as long as the reverse curves have common tangents that are at least as long as 25% of design sight distance. For reverse curves with no common tangents, offset charts have been developed and presented in this paper. Practitioners can use these charts or the derived equations to determine clearance offsets for new sites as well as for existing sites that are deficient in design sight distance.
基金Research Projects of Nanjing University of Science and Technology
文摘As one of the most important geometric parameters for a PC-type fiber connector end face, apex offset can contribute to high insertion loss and high back-reflection reading. A novel measurement method for the parameter, connector rotating-π method, is proposed. With the method, the apex offset of a common connector end face is measured. The result is compared with that measured by a Norland 3000 fiber connector end face interferometer. It is found that the difference between two results is 1.8μm. Meantime, the influences of relevant error resources on apex offset measurement under rotating-π method and apex-core method are respectively analyzed, and two error equations are derived. The analytical result shows that, compared with apex-core method, if two additional sub-tilts of axis within and in the direction perpendicular to principal plane caused by its rotation are not bigger than the original axis tilt angle, the max. measurement error will then be reduced by at least 22.5% with rotating-π method. The practicability of the method is confirmed by the experiments.
文摘The magnetic levitation transportation system is one of the potential applications of high-Tc superconducting (HTS) maglev system. The prototype HTS magnetic levitation system is composed of one HTS bulk and a permanent magnet railway (PMR). The maglev transportation system performance is influenced by the maximum levitation force, the maximum guidance force and the maximum of external applied magnetic flux density. The applied magnetic field distribution also needs to be considered carefully. In the paper, the magnetic levitation force of cylindrical HTS bulk over PMR is experimentally studied. During the experiment, symmetrical PMR and Halbach PMR are used separately. The levitation force-gap loops of different lateral offset of the HTS bulk above PMRs are obtained experimentally. The results show that the HTS bulk levitation performance is tightly relative to the external applied magnetic field distribution. The maximum magnetic levitation forces of HTS bulk above symmetrical PMR decrease linearly with the lateral offset increasing. When the lateral offset changes from 0 mm to 25 mm, the maximum magnetic levitation forces of HTS bulk above Halbach PMR increase with the lateral offset increasing. When the lateral offset exceeds the center of the Halbach PMR by 25 mm, the maximum force decreases rapidly with the increase of the lateral offset of the bulk sample.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2018YFB2200100)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB22)+1 种基金the National Natural Science Foundation of China(Grant No.118764347,11614003,11804333)H.X.D.was also supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2017154).
文摘Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces.Here,we proposed a modified method to calculate band offsets for such systems,in which the core energy level shifts caused by heterovalent effects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as transitions,respectively.Taking the Si and III-V systems as examples,the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems,and are much closer to the experimental values for the large-lattice-mismatched and heterovalent systems.Furthermore,by systematically studying the heterojunctions of Si and III-V semiconductors along different directions,it is found that the band offsets of Si/InAs and Si/InSb systems in[100],[110]and[111]directions belong to the type I,and could be beneficial for silicon-based luminescence performance.Our study offers a more reliable and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors,and could provide theoretical support for the design of the high-performance silicon-based light sources.
基金the National Natural Science Foundation of China (No. 60272009, No. 60572090, No. 60472045, No. 60496313 and No. 60602009).
文摘The problem of estimating the carrier frequency offsets in Multiple-Input Multiple-Output (MIMO) systems with distributed transmit antennas is addressed. It is supposed that the transmit antennas are distributed while the receive antennas are still centralized, and the general case where both the time delays and the frequency offsets are possibly different for each transmit antenna is considered. The channel is supposed to be frequency flat, and the macroscopic fading is also taken into consideration. A carrier frequency offset estimator based on Maximum Likelihood (ML) is proposed, which can separately estimate the frequency offset for each transmit antenna and exploit the spatial diversity. The Cramer-Rao Bound (CRB) for synchronous MIMO (i.e., the time delays for each transmit antenna are all equal) is also derived. Simulation results are given to illustrate the per- formance of the estimator and compare it with the CRB. It is shown that the estimator can provide satisfactory frequency offset estimates and its performance is close to the CRB for the Signal-to-Noise Ratio (SNR) below 20dB.
基金Project supported by the Special Funds of the National Natural Science Foundation of China(Grant Nos.11547226 and 11547180)
文摘Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS)-based thin film solar cells usually use Cd S as a buffer layer, but due to its smaller band gap(2.4 e V), Cd S film has been replaced with higher band gap materials. The cadmium zinc sulfide(Cd Zn S) ternary compound has a higher band gap than other compounds, which leads to a decrease in window absorption loss. In this paper, the band offsets at Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS) heterointerface are calculated by the first-principles, densityfunctional and pseudopotential method. The band offsets at Cd_(1-x)Zn_x S/CZTS heterointerface are tuned by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy, the calculated valence band offsets are small, which is consistent with the commonanion rule. The favorable heterointerface of type-I with a moderate barrier height(< 0.3 e V) can be obtained by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy between 0.25 and 0.375.
基金supported by the National Natural Science Foundation of China(No.42104008,42204006,41904031)the Jiangxi Provincial Natural Science Foundation(20232BAB213075)+1 种基金the Key Laboratory for Digital Land and Resources of Jiangxi Province,East China University of Technology(DLLJ202016)Open Fund of Hubei Luojia Laboratory(No.230100020,230100019)。
文摘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.
基金supported by the National Natural Science Foundation of China under Grant 62071364 and 62231027in part by the Key Research and Development Program of Shaanxi under Grant 2023-YBGY-249+1 种基金in part by the Key Research and Development Program of Guangxi under Grant 2022AB46002in part by the Fundamental Research Funds for the Central Universities under Grant KYFZ23001.
文摘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.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61911530695)the Key Research and Development Project of Shaanxi Province, China (Grant No. 2023-YBSF-671)。
文摘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.
文摘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.