Similar Velocity Research Articles

Quasi-waveform seismic tomography of crustal structures in the capital circle region of China

Seismic tomography is one of the main tools to explore the interior of the earth. In this study, the quasi-waveform seismic tomographic method is used for the first time to reveal the crustal structures in the capital region of China. 3-D high-resolution VP, VS and the Poisson’s ratio models are generated by inverting 29839 direct P- and 29972 direct S-wave traveltimes selected from 3231 local earthquakes. The results reveal strong crustal heterogeneities. The velocity anomalies at shallow depths are well consistent with surface geologic structures. The relatively low-velocity anomaly layer in the middle crust may be the result of multiple phases of tectonic activity. Earthquakes generally occurred on the boundaries of high- and low-velocity and Poisson’s ratio anomalies. There are obvious low-velocity anomalies below the hypocenters of the Tangshan earthquake and the historical Sanhe-Pinggu earthquake, implying the existence of fluids. The similar velocity structures around the hypocenters of the two earthquakes indicate that the occurrences of the two earthquakes may be related to the same mechanism. The highresolution velocity models provide important observational constraints on the small-scale heterogeneities and dynamic mechanism of the crust in the capital region of China.

Direct numerical simulations of turbulent periodic-hill flows with mass-conserving lattice Boltzmann method

The multi-relaxation time lattice Boltzmann method is used to perform direct numerical simulations of laminar and turbulent pressure-driven flows within a channel with hill-shape periodic constriction for the first time. The simulations are conducted on a graphics processing unit cluster with two-dimensional domain decomposition to accelerate the computation. The hill-shape boundary is represented using the interpolated bounce back scheme. However, the scheme generates mass leakage across the boundary, which is more pronounced in the turbulent flow regime, and this may produce diverging solutions for turbulent flows. The mass leakage due to the local mass imbalance along the curved boundary is solved by modifying the distribution functions locally or globally, and both predict similar velocity distributions. Since the global correction method is more computing time-consuming, the local correction method is adopted. The present numerical implementation’s capability is first validated by performing direct numerical simulations of turbulent channel flow at Reτ = 180, and the current predicted results agree well with the benchmark solutions. Direct numerical simulations are further conducted for the turbulent flow over the periodic hill at Reh = 2800. Both the mean velocity and turbulent stress compare favorably with the benchmark solutions. The present simulation also correctly predicts the turbulence splatting effect near the windward hill. Both phenomena are in good accordance with the benchmark solutions.

B mode ultrasonography and elastography in the evaluation of the pectineus muscle in dogs with hip dysplasia

The goal of this study was to describe and compare B mode and elastographic characteristics of the pectineus muscle of healthy dogs with dysplastic dogs. Thirty-one dogs (62 limbs) with hip dysplasia and 17 nondysplastic dogs (34 limbs) were evaluated. The hip dysplasia score was defined according to the Fédération Cynologique Internationale. Using B mode, echotexture and echogenicity of different regions of the pectineus muscle were evaluated. By means of ARFI elastography, qualitative (elastogram) and quantitative (shear wave velocity) tissue stiffness was assessed. B mode findings demonstrated a hyperechoic and heterogeneous pattern of the pectineus tissue in dogs with hip dysplasia, with compromised muscular delimitation and loss of its normal sonographic appearance, indicating the disease (P < 0.001). In the elastogram, it was observed that dogs with hip dysplasia showed less deformable pectineus muscle, with red colors (rigid). In quantitative evaluation, the different regions evaluated presented similar shear wave velocities; in dysplastic patients, shear wave velocities were higher compared to nondysplastic animals, with values higher than 2.85 m/s being strong indicators of the disease. Values of shear wave velocity were also influenced by the grade of dysplasia and age of the patients; however, there was no correlation with the depth of the evaluated area or body weight. It was concluded that pectineus muscle in dogs with hip dysplasia presents B mode and elastographic changes when compared to normal animals, demonstrating that these techniques might aid the evaluation of diseased dogs.

The influence of inlet velocity profile on predicted flow in type B aortic dissection

In order for computational fluid dynamics to provide quantitative parameters to aid in the clinical assessment of type B aortic dissection, the results must accurately mimic the hemodynamic environment within the aorta. The choice of inlet velocity profile (IVP) therefore is crucial; however, idealised profiles are often adopted, and the effect of IVP on hemodynamics in a dissected aorta is unclear. This study examined two scenarios with respect to the influence of IVP—using (a) patient-specific data in the form of a three-directional (3D), through-plane (TP) or flat IVP; and (b) non-patient-specific flow waveform. The results obtained from nine simulations using patient-specific data showed that all forms of IVP were able to reproduce global flow patterns as observed with 4D flow magnetic resonance imaging. Differences in maximum velocity and time-averaged wall shear stress near the primary entry tear were up to 3% and 6%, respectively, while pressure differences across the true and false lumen differed by up to 6%. More notable variations were found in regions of low wall shear stress when the primary entry tear was close to the left subclavian artery. The results obtained with non-patient-specific waveforms were markedly different. Throughout the aorta, a 25% reduction in stroke volume resulted in up to 28% and 35% reduction in velocity and wall shear stress, respectively, while the shape of flow waveform had a profound influence on the predicted pressure. The results of this study suggest that 3D, TP and flat IVPs all yield reasonably similar velocity and time-averaged wall shear stress results, but TP IVPs should be used where possible for better prediction of pressure. In the absence of patient-specific velocity data, effort should be made to acquire patient’s stroke volume and adjust the applied IVP accordingly.

Time-resolved size, velocity, and temperature statistics of aluminum combustion in solid rocket propellants

The study of time-resolved aluminum combustion mechanisms is essential for understanding the deflagration of ammonium perchlorate-based metalized solid rocket propellants. In order to gain further insight into the performance of solid propellants, spatially and temporally resolved aluminum agglomerate particle dynamics are obtained by combining digital in-line holography (DIH) and two-color imaging pyrometry with high-speed acquisition at up to 20 kHz. Holography is used to find the size, three-dimensional position, and three-dimensional velocity evolution of agglomerates over time. Then, the temperature of individual particles is extracted from the high-speed imaging pyrometry. This diagnostic technique not only produces joint size, position, velocity, and temperature statistics over time, but also captures the combustion histories for thousands of particles per experiment. For the first time, these spatial and temporal dynamics of individual aluminum particulates are examined while they travel away from the propellant surface. Initial results demonstrate how aluminum agglomerates of similar size exhibit varying initial acceleration but similar steady-state velocities. Average velocity also decreases as particle size increases, which is consistent with viscous flow dynamics of small particles in convective flow. As they move further away from the propellant surface, large agglomerates also show a convergence to an average projected temperature between the melting point of aluminum oxide and the boiling point of aluminum. The average projected particle surface temperatures were measured to be 2494 ± 231 K. The method outlined in this work demonstrates a new capability for gathering the evolution of joint statistics for aluminum agglomerates in solid-rocket propellants. Future applications of this technique can be used to evaluate the detailed combustion mechanisms of existing or new propellant formulations.

Analysis of Operating Principles and Flow Field Characteristics for a Diving Ballast Tank

Operating principle and flow field characteristics of a diving ballast tank for application in submerged vehicles were investigated in the present study. As understanding the complex changes in the interior air-water two-phase flow field of the ballast tank during the diving process is difficult, this study specifically performed a ballast tank diving experiment. Experimental and numerical simulations to analyse the diving motions of the ballast tank were conducted. Authors comprehensively evaluated the flow field changes in the ballast tank and its surroundings. The experimental and numerical results were compared in terms of the observed displacements and velocities during diving. Both the results indicated similar motion trajectories and velocities. Authors effectively observed the air-water two-phase flow field change inside the ballast tank using this numerical method. Therefore, the numerical model constructed in this study can be useful for analysing the diving motions of ballast tanks and can effectively predict the interior flow field characteristics of a ballast tank.

Nascent Flux Rope Observations at Earth's Dayside Magnetopause

AbstractTwo THEMIS satellites, separated by only 0.38 Earth radii (RE), traversed two consecutive dayside magnetopause (MP) current sheets at 3.5 < ZGSM < 3.8 RE on 15 November 2010. An early‐stage crater‐like flux transfer event (FTE) with weakly enhanced total pressure is sampled at the first, complete outbound MP crossing. A mature FTE flux rope is observed just 70 s later across the second, inbound crossing of the MP current sheet. Two counterstreaming magnetosheath ion beams at the interface of two converging reconnection exhausts earthward of the MP current sheet provide direct evidence of two X‐lines across the early‐stage crater FTE. A D‐shaped ion beam observed along the southward magnetic field in the magnetosheath boundary layer and northward exhausts observed earthward of the MP provide evidence of two X‐lines across the mature FTE flux rope. Tripolar out‐of‐plane magnetic field perturbations (ΔBM) of substantial magnitudes were sampled across the MP current sheet in both stages of the FTE flux rope evolution. These dayside observations suggest an association between a tripolar ΔBM perturbation with two magnetic reconnection X‐lines and FTE flux rope formation. A dedicated particle‐in‐cell numerical simulation of magnetic reconnection reproduces similar ion velocity distributions and out‐of‐plane magnetic field perturbations at an asymmetric current sheet as those observed across a nascent flux rope between two X‐lines at the dayside asymmetric MP.

ANALYSIS OF PRESSURE AND VELOCITY EFFECTS OF ACOUSTIC WAVES ON DIFFERENT AMBIENT SURFACES USING FDTD METHOD

Bu çalışmada ses dalgalarının farklı ortam yüzeylerinde meydana getirdiği basınç ve hız değişimleri ele alınmıştır. Ultrason dalgalarına benzerliği nedeniyle çalışmada ses dalgaları kullanılmıştır. Dalga modeli olarak, gauss nabız dalga modeli kullanılmıştır. Ortam yüzeyleri olarak hava, su, metal, s-oil, polietilen gibi cansız yüzeyler, doku türleri da olarak bağ doku ve kas dokusu yüzeyleri analizlerde kullanılmıştır. Seçilen bu ortam yüzeylerinde, akustik dalgalarının oluşturduğu basınç etkileri, zamanda sonlu farklar (FDTD) metodu kullanılarak incelenmiştir. Örneklenen gauss ses dalgasının analizinde, iterasyon sayısı arttıkça yayılım değeri de artmaktadır. Polietilen yapılı katmanlarda ise sesin oluşturduğu basıncın etkisinin düşük olduğu (Pplastik=39,5 µPa ve Vplastik=13,17 µm/sn ) tespit edilmiştir. Canlı dokulardan bağ dokusu ve kas dokusu üzerinde yapılan incelemede ise bir ses dalgasının bu iki doku üzerinde benzer basınç (Pbağ=1,295 Pa, Pkas=1,282 Pa) ve hız (Vbağ=0,63 µm/sn, Vkas= 0,58 µm/sn) değerleri oluşturduğu gözlenmektedir.

Three‐dimensional Hiemenz stagnation‐point flows

AbstractA modification of Hiemenz's two‐dimensional outer potential stagnation‐point flow of strain rate a is obtained by adding periodic radial and azimuthal velocities of the form and , respectively, where b is a shear rate. This leads to the discovery of a new family of three‐dimensional viscous stagnation‐point flows depending on the shear‐to‐strain‐rate ratio that exist over the range with reflectional symmetry about . Numerical solutions for the wall shear stress parameters and the displacement thicknesses are given and compared with their large‐γ asymptotic behaviors. Sample similarity velocity profiles are also presented. It is noted that the results presented here are in many ways similar to the results reported for non‐axisymmetric Homann stagnation‐point flow.

FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). VIII. Possible evidence of cloud–cloud collisions triggering high-mass star formation in the giant molecular cloud M 16 (Eagle Nebula)

Abstract M 16, the Eagle Nebula, is an outstanding H ii region which exhibits extensive high-mass star formation and hosts remarkable “pillars.” We herein obtained new 12COJ = 1–0 data for the region observed with NANTEN2, which were combined with the 12COJ = 1–0 data obtained using the FOREST unbiased galactic plane imaging with Nobeyama 45 m telescope (FUGIN) survey. These observations revealed that a giant molecular cloud (GMC) of ∼1.3 × 105 M⊙ is associated with M 16, which extends for 30 pc perpendicularly to the galactic plane, at a distance of 1.8 kpc. This GMC can be divided into the northern (N) cloud, the eastern (E) filament, the southeastern (SE) cloud, the southeastern (SE) filament, and the southern (S) cloud. We also found two velocity components (blueshifted and redshifted components) in the N cloud. The blueshifted component shows a ring-like structure, and the redshifted one coincides with the intensity depression of the ring-like structure. The position–velocity diagram of the components showed a V-shaped velocity feature. The spatial and velocity structures of the cloud indicated that two different velocity components collided with each other at a relative velocity of 11.6 km s−1. The timescale of the collision was estimated to be ∼4 × 105 yr. The collision event reasonably explains the formation of the O9V star ALS 15348, as well as the shape of the Spitzer bubble N19. A similar velocity structure was found in the SE cloud, which is associated with the O7.5V star HD 168504. In addition, the complementary distributions of the two velocity components found in the entire GMC suggested that the collision event occurred globally. On the basis of the above results, we herein propose a hypothesis that the collision between the two components occurred sequentially over the last several 106 yr and triggered the formation of O-type stars in the NGC 6611 cluster in M 16.

The validity of floating chambers in quantifying CO2 flux from headwater streams

AbstractThe amount of CO2 exiting headwater streams through degassing plays an important role in the global carbon cycle, yet quantification of CO2 degassing remains challenging because of the morphology of headwater streams and because of uncertainty about whether floating or suspended chambers provide valid measurements in moving water. We show that experiments using large and small floating chambers in flowing water over a moderate range of water velocities (0.13–0.23 m s−1) in a laboratory flume resulted in similar k600s to published field measurements with similar water velocities. We confirmed the flume experiments with paired stirred-still beaker experiments, where resulting k600s fell within the extrapolated trend of the flume experiments. We propose that the floating chambers can provide good estimates of CO2 degassing, particularly in shallow, low-velocity, morphologically complex headwater streams, permitting quantification of this important contributor to the global carbon cycle.

Three-Dimensional Simulations of Solar Wind Preconditioning and the 23 July 2012 Interplanetary Coronal Mass Ejection

Predicting the large-scale eruptions from the solar corona and their propagation through interplanetary space remains an outstanding challenge in solar- and helio-physics research. In this article, we describe three-dimensional magnetohydrodynamic simulations of the inner heliosphere leading up to and including the extreme interplanetary coronal mass ejection (ICME) of 23 July 2012, developed using the code PLUTO. The simulations are driven using the output of coronal models for Carrington rotations 2125 and 2126 and, given the uncertainties in the initial conditions, are able to reproduce an event of comparable magnitude to the 23 July ICME, with similar velocity and density profiles at 1 au. The launch time of this event is then varied with regards to an initial 19 July ICME and the effects of solar wind preconditioning are found to be significant for an event of this magnitude and to decrease over a time-window consistent with the ballistic refilling of the depleted heliospheric sector. These results indicate that the 23 July ICME was mostly unaffected by events prior, but would have traveled even faster had it erupted closer in time to the 19 July event where it would have experienced even lower drag forces. We discuss this systematic study of solar wind preconditioning in the context of space weather forecasting.

Performance and reference data in the jump squat at different relative loads in elite sprinters, rugby players, and soccer players.

The aims of this study were to compare the outcomes and provide reference data for a set of barbell mechanical parameters collected via a linear velocity transducer in 126 male sprinters (n = 62), rugby players (n = 32), and soccer players (n = 32). Bar-velocity, bar-force, and bar-power outputs were assessed in the jump-squat exercise with jump-squat height determined from bar-peak velocity. The test started at a load of 40% of the athletes’ body mass (BM), and a load of 10% of BM was gradually added until a clear decrement in the bar power was observed. Comparisons of bar variables among the three sports were performed using a one-way analysis of variance. Relative measures of bar velocity, force, and power, and jump-squat height were significantly higher in sprinters than in rugby (difference ranging between 5 and 35%) and soccer (difference ranging between 5 and 60%) players across all loads (40–110% of BM). Rugby players exhibited higher absolute bar-power (mean difference = 22%) and bar-force (mean difference = 16%) values than soccer players, but these differences no longer existed when the data were adjusted for BM (mean difference = 2.5%). Sprinters optimized their bar-power production at significantly greater relative loads (%BM) than rugby (mean difference = 22%) and soccer players (mean difference = 25%); nonetheless, all groups generated their maximum bar-power outputs at similar bar velocities. For the first time, we provided reference values for the jump-squat exercise for three different bar-velocity measures (i.e., mean, mean propulsive, and peak velocity) for sprinters, rugby players, and soccer players, over a wide range of relative loads. Practitioners can use these reference values to monitor their athletes and compare them with top-level sprinters and team-sport players.

Super-Resolution Microscopy and Single-Molecule Tracking Reveal Distinct Adaptive Dynamics of MreB and of Cell Wall-Synthesis Enzymes.

The movement of filamentous, actin-like MreB and of enzymes synthesizing the bacterial cell wall has been proposed to be highly coordinated. We have investigated the motion of MreB and of RodA and PbpH cell wall synthesis enzymes at 500 ms and at 20 ms time scales, allowing us to compare the motion of entire MreB filaments as well as of single molecules with that of the two synthesis proteins. While all three proteins formed assemblies that move with very similar trajectory orientation and with similar velocities, their trajectory lengths differed considerably, with PbpH showing shortest and MreB longest trajectories. These experiments suggest different on/off rates for RodA and PbpH at the putative peptidoglycan-extending machinery (PGEM), and during interaction with MreB filaments. Single molecule tracking revealed distinct slow-moving and freely diffusing populations of PbpH and RodA, indicating that they change between free diffusion and slow motion, indicating a dynamic interaction with the PGEM complex. Dynamics of MreB molecules and the orientation and speed of filaments changed markedly after induction of salt stress, while there was little change for RodA and PbpH single molecule dynamics. During the stress adaptation phase, cells continued to grow and extended the cell wall, while MreB formed fewer and more static filaments. Our results show that cell wall synthesis during stress adaptation occurs in a mode involving adaptation of MreB dynamics, and indicate that Bacillus subtilis cell wall extension involves an interplay of enzymes with distinct binding kinetics to sites of active synthesis.

Stable hooks: biomechanics of heteromorph ammonoids with U-shaped body chambers

ABSTRACTThe biomechanics of uncoiled heteromorph ammonoids with body chambers that terminate in U-shaped hooks (ancylocones) were investigated with virtual and physical models of Audouliceras renauxianum. Virtual models were used to compute the hydrostatic properties of this morphotype. Audouliceras has the capacity for neutral buoyancy and this suggests that other taxa with similar proportions had this ability as well. Hydrostatic stability gradually increases during ontogeny, coincident with the larger degree of uncoiling. The juvenile planispiral stage has a similar stability and apertural orientation to the extant Nautilus. The adult stage, however, undergoes an increase in stability by a factor of over 3, while assuming an upward-facing posture. Counterintuitively, the stage during the formation of the shaft (before the growth of the U-shaped hook) is oriented horizontally. This intermediate stage would have had poor horizontal mobility due to the positioning of the hyponome below the centre of mass. The juvenile planispiral stage and mature stage, however, would have been well suited to horizontal backward movement with minimal rocking. Ancylocones are generally thought of as quasiplanktic vertical migrants. Thus, their relative horizontal swimming ability has been largely disregarded. Experiments on 3D printed, neutrally buoyant physical models reveal that hydrodynamic drag is indeed larger compared to Nautilus. However, Audouliceras could reach similar maximum horizontal velocities depending on the available thrust. Sepia-like thrusts yield velocities similar to equivalently sized Nautilus (c. 15 cm/s), while Nautilus-like thrusts yield velocities not much lower (c. 11 cm/s). Due to the hydrostatic properties of the ancylocone, the adult model undergoes less rocking (±4.5°) during movement than Nautilus (±10°). The minimal hydrodynamic consequences for ancylocones suggest that stability, orientation and directional efficiency are key selective pressures for some heteromorph shells, which may have primarily served as hydrostatic devices.

The effect of cement material properties on the fracture patterns developing within cement-covered brittle sphere under impact

Dynamic loading experiments of single glass bead cement-covered by epoxy resins of different compositions demonstrate the existence of diverse fracture patterns under similar impact velocities and high strain rates. A comparison of these fracture patterns between different resin compositions highlights two distinctive fracture mechanisms, namely cement-focused fracture and grain-focused fracture mechanisms, which is affected by the interface adhesion toughness. The transition between those patterns is characterised by the damage of the cement/grain interface adhesion. Using Fourier transform of the X-ray micro-computed tomography images, the details of the locality of the damage within the cemented bead are then quantitatively analysed, as well as the preferential crack orientation. Several sporadic curved cracks are observed near the cement/grain interface region in the cement-focused fracture cases, roughly along the interface. However, for grain-focused fracture cases, damage is most likely to occur along the central loading axis area of the cemented bead and prevailingly forms diametric cracks along the impact direction. The results of this study are expected to help advancing the development of models that predict the deterioration of brittle cemented geomaterials under impact.

First 3D morpho-kinematic model of supernova remnants. The case of VRO 42.05.01 (G166.0+4.3)

ABSTRACTWe present the first three-dimensional (3D) morpho-kinematic (MK) model of a supernova remnant (SNR), using as a case study the Galactic SNR VRO 42.05.01. We employed the astrophysical code SHAPE in which wide field imaging and high-resolution spectroscopic data were utilized, to reconstruct its 3D morphology and kinematics. We found that the remnant consists of three basic distinctive components that we call: a ‘shell’, a ‘wing’, and a ‘hat’. With respect to their kinematical behaviour, we found that the ‘wing’ and the ‘shell’ have similar expansion velocities (Vexp = 115 ± 5 km s−1). The ‘hat’ presents the lowest expansion velocity of the remnant (Vexp = 90 ± 20 km s−1), while the upper part of the ‘shell’ presents the highest velocity with respect to the rest of the remnant (Vexp = 155 ± 15 km s−1). Furthermore, the whole nebula has an inclination of ∼3°–5° with respect to the plane of the sky and a systemic velocity of Vsys = −17 ± 3 km s−1. We discuss the interpretation of our model results regarding the origin and evolution of the SNR and we suggest that VRO 42.05.01 had an interaction history with an inhomogeneous ambient medium most likely shaped by the mass outflows of its progenitor star.

Properties of the Hot Ambient Medium of Early-type Galaxies Hosting Powerful Radio Sources

Abstract We present an archival analysis of Chandra X-ray observations for 12 nearby early-type galaxies hosting radio sources with radio power >1023 W Hz−1 at 1.4 GHz, similar to the radio power of the radio source in NGC 4261. Previously, in a similar analysis of eight nearby X-ray and optically bright elliptical galaxies, Werner et al. found that NGC 4261 exhibited unusually low central gas entropy compared to the full sample. In the central 0.3 kpc of NGC 4261, the ratio of cooling time to freefall time (t cool/t ff) is less than 10, indicating that cold clouds may be precipitating out of the hot ambient medium and providing fuel for accretion in the central region. NGC 4261 also hosts the most powerful radio source in the original sample. Because NGC 4261 may represent an important phase during which powerful feedback from a central active galactic nucleus (AGN) is fueled by multiphase condensation in the central kiloparsec, we searched the Chandra archive for analogs to NGC 4261. We present entropy profiles of those galaxies, as well as profiles of t cool/t ff. We find that one of them, IC 4296, exhibits properties similar to NGC 4261, including the presence of only single-phase gas outside of r ∼ 2 kpc and a similar central velocity dispersion. We compare the properties of NGC 4261 and IC 4296 to hydrodynamic simulations of AGN feedback fueled by precipitation. Over the course of those simulations, the single-phase galaxy has an entropy gradient that remains similar to the entropy profiles inferred from our observations.

Laser-driven collisionless shock acceleration of ions from near-critical plasmas

This paper overviews experimental and numerical results on acceleration of narrow energy spread ion beams by an electrostatic collisionless shockwave driven by 1 μm (Omega EP) and 10 μm (UCLA Neptune Laboratory) lasers in near critical density CH and He plasmas, respectively. Shock waves in CH targets produced high-energy ∼50 MeV protons (ΔE/E of ≤30%) and 314 MeV C6+ ions (ΔE/E of ≤10%). Observation of acceleration of both protons and carbon ions to similar velocities is consistent with reflection of particles off the moving potential of a shock front. For shocks driven by CO2 laser in a gas jet, ∼30 MeV peak in He ion spectrum was detected. Particle-in-cell simulations indicate that regardless of the target further control over its density profile is needed for optimization of accelerated ion beams in part of energy spread, yield and maximum kinetic energy.

Low-thrust transfer to the Earth-Moon triangular libration point via horseshoe orbit

This paper proposes a novel method for the low-thrust transfer to the triangular libration points in the Earth-Moon system. Horseshoe orbit is explored as the coasting arc in this transfer scenario. By tangential thrust control strategy, the low-thrust transfer from the Earth to the short-period orbit around L4 point is realized. The pseudospectral method is used to obtain another Earth-L4 transfer trajectory by solving an energy-optimal low-thrust trajectory optimization problem. Interestingly, these two kinds of Earth-L4 low-thrust transfer trajectories both share similar geometric configuration and velocity trend with a natural Horseshoe orbit, which evokes the main contributions of this paper that leveraging Horseshoe orbit as the coasting arc. The complete transfer trajectory is divided into three phases: Earth spiral phase, Horseshoe coasting phase and L4 point insertion phase, where the first and the third are powered phases. The tangential thrust control strategy is used in the first phase to generate the transfer from the Earth to the Horseshoe orbit, and the pseudospectral method is utilized in the third phase to enable the transfer from the Horseshoe coasting arc to the L4 point by solving a time-optimal transfer problem. Then, by patching these two powered segments with the unpowered Horseshoe coasting arc, the Earth-L4 low-thrust transfer is constructed.