Oblique Angle Research Articles

Oblique view imaging analysis of a hypothetical earth observation satellite enabled with metamaterial-based image sensors

This study presents the image quality estimates of a hypothetical earth observation satellite (EOS) equipped with metaxel-based image sensors for the oblique viewing angle of the pitch manoeuvre scenario. Oblique-view image estimation methods are proposed and demonstrated for the optical and detector images. Owing to the small detector period (p) of the metaxel supercells ( p = 1.32 μ m ), the optical system image is optics limited. For oblique angle of θ p = 15 ∘ , 30 ∘ , 45 ∘ , 60 ∘ , image quality degradation owing to the aberration remained minor and average signal to noise ratio (SNR) for nadir view was SNR = 64 because of the local field enhancement of the metaxels. However, changes in the viewing angle reduced the image quality. Correlation coefficient between synthetic ground truth and oblique viewing cases was corr = 0.833, 0.818, 0.793 and 0.745 for the viewing angles of interest listed above.

Greater pelvic obliquity in adolescent idiopathic scoliosis combined with hip dysplasia

BackgroundAdolescent idiopathic scoliosis (AIS) is a spinal deformity that affects adolescents and poses a challenging public health problem. Compared to the general population, adolescents with AIS have a higher prevalence of hip dysplasia. However, the mechanisms underlying the impact of hip dysplasia on the coronal balance of the spine remain poorly understood. We hypothesized that the combination of AIS with hip dysplasia would exacerbate coronal imbalance.MethodsWe retrospectively analyzed the medical records and radiographs of adolescents diagnosed with AIS between 2015 and 2020. Participants were divided into two groups: those with hip dysplasia and those without. We recorded parameters related to the coronal deformity of the spine, sacral and pelvic obliquity, and center edge angle (CEA). We investigated differences in these parameters in those with and without hip dysplasia and analyzed their relationships in those with combined AIS and hip dysplasia.ResultsA total of 103 adolescents were included, 36 with hip dysplasia and 67 without. Those with hip dysplasia had significantly higher sacroiliac discrepancy (SID) compared to those without (t = − 2.438, P = 0.017). In adolescents with hip dysplasia, only iliac obliquity angle (IOA) was significantly correlated with SID (r = − 0.803, P < 0.001), with a linear relationship between them (r2 = 0.645, P < 0.001).ConclusionsThe incidence of hip dysplasia is higher in the AIS population. In adolescents with combined AIS and hip dysplasia, pelvic obliquity is greater, potentially contributing to the increased prevalence of low back pain.

Structure of rotating detonation in mixtures of natural gas and oxygen

The rotating detonation combustor is investigated as a potential implementation of pressure-gain combustion. Achieving net pressure-gain has proven to be extremely challenging in most combustors reported in the literature, regardless of their operating parameters. The performance losses observed in rotating detonation, compared to ideal predictions, can be attributed to mechanisms such as vitiation by residual burnt gases, partial detonation, and pre-combustion of reactants. The literature frequently discusses the impact of these mechanisms on measurable properties such as thrust and wave speed, but their effects on the front structure have not been fully understood. This study proposes using the rotating detonation structure for the first time to evaluate the vitiation quantitatively. The front structure of a compressed natural gas — oxygen-fueled rotating detonation is characterized using broadband chemiluminescence, and properties such as oblique shock angle, expansion angle, and front height are reported. The experimental values are then compared to the ideal predictions derived based on mass flow rates. The experimental front heights are found to be much higher than their ideal predicted counterparts. Analytical calculations that include pre-burning and vitiation show an increase in front height and a reduction in expansion angle, consistent with the chemiluminescence levels observed. The vitiated mass fraction is then deduced from the experimental front height, and the remaining velocity deficit is then used to evaluate the partial detonation mass fraction. Vitiated front angles compare favorably to the predicted values.Novelty and SignificanceThis study reports high-quality chemiluminescence imaging of natural gas/oxygen rotating detonation front enabling the measurement of critical geometrical front features such as the front height, oblique shock angle, and expansion angle. The conventional front mass flow rate balance is extended to account for the re-circulation of burnt gases effects and is used to estimate the experimental vitiation. Most notably, vitiation of the fresh mixture, which was already known to reduce front speed and pressure rise, is also shown to strongly decrease the expansion angle resulting in further losses of axial thrust.

Nanoporous antireflection coating for high-temperature applications in the infrared

Antireflection (AR) coatings are essential to the performance of optical systems; without them, surface reflections increase significantly at steep angles and become detrimental to the functionality. AR coatings apply to a wide range of applications from solar cells and laser optics to optical windows. Many times, operational conditions include high temperatures and steep angles of incidence (AOIs). The implementation of AR coatings is extremely challenging in these conditions. Nanoporous coatings made from high-temperature-tolerant materials offer a solution to this problem. The careful selection of materials is needed to prevent delamination when exposed to high temperatures, and an optimal optical design is needed to lower surface reflections at both the normal incidence and steep AOIs. This paper presents nanoporous silicon dioxide and hafnium dioxide coatings deposited on a sapphire substrate using oblique angle deposition by electron beam evaporation, a highly accurate deposition technique for thin films. Developed coatings were tested in a controlled temperature environment and demonstrated thermal stability at temperatures up to 800°C. Additional testing at room temperature demonstrated the reduction of power reflections near optimal for AOIs up to 70° for a design wavelength of 1550 nm. These findings are promising to help extend the operation of technology at extreme temperatures and steep angles.

Analysis of radiographic factors affecting the significant differences in knee alignment between hip-to-talus and hip-to-calcaneus radiographs after opening-wedge high tibial osteotomy

BackgroundOptimal alignment after opening-wedge high tibial osteotomy (OWHTO) is crucial for obtaining good clinical results. A hip-to-calcaneus radiograph (HCR) appears to reflect the true mechanical axis. However, no study has been reported using the HCR in patients who underwent OWHTO. We aimed to analyze the radiographic factors affecting the significant difference in the weight-bearing line (WBL) ratio between two radiographs after opening-wedge high tibial osteotomy (OWHTO).MethodsThis retrospective study included 51 patients who underwent both hip-to-talus radiographs (HTR) and HCR after OWHTO. The patients were divided into two groups; a consistent group (WBL ratio difference between postoperative HTR and HCR < 5%; N = 35) and an inconsistent group (> 5%; N = 16). Radiographic variables for lower extremity alignment, knee and ankle joints, and clinical scores were evaluated. The receiver operating characteristic curve was used to determine the threshold of radiographic variables that induced inconsistencies between the two radiographs.ResultsThe mean postoperative WBL ratio in the HCR of the inconsistent group was significantly higher than that of the consistent group (57.7 ± 13.2% and 49.1 ± 11.6%, respectively) (P = 0.02). The preoperative and postoperative ankle joint line obliquity (AJLO) and preoperative lateral distal tibia ground surface angle (LDTGA) were significantly different between the two groups (P < 0.05). The preoperative AJLO (odds ratio 0.784, confidence interval 0.655–0.939, P = 0.008) significantly affected WBL ratio inconsistency. The cutoff value of the preoperative AJLO was 3.16°. However, clinical scores did not differ significantly between the two groups.ConclusionThe pre-and postoperative AJLO and the preoperative LDTGA were significantly different between the two groups. Among these variables, only preoperative AJLO negatively affected the inconsistency in WBL ratios between the two radiographs (HTT and HTC). Therefore, it should be considered to prevent postoperative overcorrection of the true mechanical axis after OWHTO, even though we corrected it properly.Level of evidence Level IV.

Multipole solution with nonlinear pressure loss for oblique waves action on a submerged partially perforated semi-circular breakwater

This study is an extension of the research on semi-circular breakwater based on Lyu et al. (2020). This time, we focus on the changes in the flow field when waves obliquely interact with the axis of the partially perforated semi-circular breakwater, as well as the nonlinear effects resulting from variations in wave height to some extent. The analytical solution of the flow field is still obtained using the multipole expansion method based on potential flow theory and the method of separation of variables. The analytical solution for oblique incidence is primarily achieved through the cylindrical form of the Bessel equation. Separately considering viscous effects and potential flow, we estimate the impact of wave height variation on the perforated boundary through the quadratic pressure loss term. By employing an iterative solving approach, we comprehensively discuss the influence of wave height, water depth, perforation form, and oblique incidence angle on the flow field and the forces acting on the breakwater.

Spectroscopic Ellipsometry: Advancements, Applications and Future Prospects in Optical Characterization

Spectroscopic ellipsometry (SE), a non-invasive optical technique, is a powerful tool for characterizing surfaces, interfaces, and thin films. By analyzing the change in the polarization state of light upon reflection or transmission through a sample, ellipsometry provides essential parameters such as thin film thickness (t) and optical constants (n, k). This review article discusses the principles of ellipsometry, including the measurement of key values ∆ and Ψ, and the complex quantity ρ. The article also presents the Fresnel equations for s and p polarizations and the importance of oblique angles of incidence in ellipsometry. Data analysis in ellipsometry is explored, including the determination of bandgap and data referencing the electrical properties of materials. The article emphasizes the importance of choosing the appropriate models to fit ellipsometric data accurately, with examples of the Cauchy and Lorentz models. Additionally, the Kramers–Kronig relations are introduced, illustrating the connection between real and imaginary components of optical constants. The review underscores the significance of ellipsometry as a non-destructive and versatile technique for material characterization across a wide range of applications.

A Dual Band 28/38 GHz Metamaterial Absorber for 5G Applications

A dual-band metamaterial absorber (MMA) for fifth-generation (5G) applications is discussed in this work. The suggested absorber works at frequency bands of 28 GHz and 38 GHz. The suggested MMA unit cell with a size of 5.8 mm × 5.8 mm (0.54 λ0 × 0.54 λ0 at 28 GHz) is designed on 1.5 mm (0.14 λ0) low-cost FR4 substrate and composed of two metallic ring resonators. The suggested MMA is investigated to validate its performance for different polarization for transverse electric (TE) and transverse magnetic (TM). Both normal and oblique angles are studied. The MMA has a simple structure with a compact size. Different parameters such as the currents, electric field distributions, and normalized impedance are studied. The array of 10 × 10 unit cells is utilized to verify the simulated outcomes. The suggested MMA is fabricated and tested, and its outcomes are compared to the simulated outcomes. The MMA is operated at dual bands 28/38 GHz with high absorption rates of 98 and 98.4%, respectively, under the normal incidence for both outcomes. A good matching between the two outcomes is observed, which supports the MMA for 5G applications.

TOI-1670 c, a 40 day Orbital Period Warm Jupiter in a Compact System, Is Well Aligned

We report the measurement of the sky-projected obliquity angle λ of the warm Jovian exoplanet TOI-1670 c via the Rossiter–McLaughlin effect. We observed the transit window during UT 2023 April 20 for 7 continuous hours with NEID on the 3.5 m WIYN Telescope at Kitt Peak National Observatory. TOI-1670 hosts a sub-Neptune (P ∼ 11 days; planet b) interior to the warm Jovian (P ∼ 40 days; planet c), which presents an opportunity to investigate the dynamics of a warm Jupiter with an inner companion. Additionally, TOI-1670 c is now among the longest-period planets to date to have its sky-projected obliquity angle measured. We find planet c is well aligned to the host star, with λ = − 0.°3 ± 2.°2. TOI-1670 c joins a growing census of aligned warm Jupiters around single stars and aligned planets in multiplanet systems.

MetaVision: enabling independent wavefront control for diverse/oblique illumination angles

The potential of metasurface holography holds significant promise for revolutionary breakthroughs and groundbreaking advancements in imaging, chip-integrated AR/VR technology, and flat optical displays. Traditional diffractive systems, including metasurfaces, display fixed angular behavior due to the grating period defining incidence angles and diffraction limited response. To break this limit, we offer spin-encoded spatially multiplexed metaholograms designing technique facilitating efficient modulation of geometric phases. The proposed technique gives independent control over polarization states, permitting separate optical modifications for different oblique incident angles. Our suggested metasurface illustrates a multifunctional design method using traditional single-resonator geometry, effectively generating three high-fidelity far-field holographic images. Due to simple geometry and dense information multiplexing proposed approach holds potential for different applications, such as holographic optical elements (HOEs), enhanced optical storage, and anti-counterfeiting techniques.

Study on High-Velocity Impact Perforation Performance of CFRP Laminates for Rail Vehicles: Experiment and Simulation.

To study the perforation performance of CFRP laminates for rail vehicles under high-velocity impact from foreign objects, impact tests on CFRP laminates at a velocity of 163 m/s were carried out, and a corresponding finite element model was established using ABAQUS and verified. The user-defined material subroutine combined the material strain rate hardening effect and the 3D-Hashin damage criterion. The effects of impact velocity, impact object shape, and oblique angle on the perforation performance of CFRP laminates are discussed. Results show that impact velocity positively correlates with impact peak force and residual velocity. Laminates can be perforated by projectiles with a velocity above 120 m/s, and impact velocity greatly influences delamination below 140 m/s. Three shapes of projectile impacting laminates are considered: spherical, cylindrical, and conical. The conical projectile penetrates the laminate most easily, with the largest delamination area. The cylindrical projectile with a flat end suffers the most resistance, and the delaminated area is between the impact conditions of the conical and spherical projectiles. Increasing the angle of inclination increases the impacted area of the laminate and the extent of damage, thus dissipating more energy. The projectile fails to penetrate the laminate when the oblique angle reaches 60°. CFRP composite structures penetrated by high-speed impacts pose a significant threat to the safety of train operations, providing an opportunity for the application of bio-inspired composite structures.

A low-profile metamaterial absorber with ultrawideband reflectionless and wide-angular stability

An ultrawideband reflectionless metamaterial absorber (MA) is proposed by replacing the metallic ground with the complementary split-ring resonator (CSRR) structure. The proposed MA exhibits −10 dB reflectivity spectrum from 1 GHz to 20 GHz, which maintains more than 90% absorption from 1.5 GHz to 20 GHz. Furthermore, it achieves angle stability for TE and TM polarization at oblique incident angles up to 40° and 65°, respectively. To achieve broadband absorption spectrum, we have adopted a single-layer high-impedance surface (HIS) loaded with a double-layer magnetic material (MM) structure. To further realize the RCS reduction into a lower frequency range, we have employed the scattering cancellation technology into the traditional metallic ground. Finally, we have fabricated a sample exhibiting the 10 dB RCS reduction from 1 GHz to 20 GHz with a thickness of 10 mm. Measurement and simulation results confirm that the proposed MA exhibits excellent comprehensive performance, making it suitable for many practical applications.

Hydrodynamic characteristics and particle tracking of 90° lateral intakes at an inclined river slope

Lateral intakes are common in rivers. The pump efficiency and sediment deposition are determined by the local hydrodynamic characteristics and mainstream division width. The hydraulic characteristics of lateral withdrawal from inclined river slopes at different intake elevations should be investigated. Meanwhile, the division width exhibits significant vertical non-uniformity at an inclined river slope, which should be clarified. Hence, a three-dimensional (3-D) hydrodynamic and particle-tracking model was developed with the Open Source Field Operation and Manipulation (OpenFOAM), and the model was validated with physical model tests for 90° lateral withdrawal from an inclined side bank. The flow fields, withdrawal sources, and division widths were investigated with different intake bottom elevations, withdrawal discharges, and main channel velocities. This study showed that under inclined side bank conditions, water entered the intake at an oblique angle, causing significant 3-D spiral flows in the intake rather than two-dimensional closed recirculation. A lower withdrawal discharge, a lower bottom elevation of the intake, or a higher main channel velocity could further strengthen this phenomenon. The average division width and turbulent kinetic energy were smaller under inclined side bank conditions than under vertical bank conditions. With a low intake bottom elevation, a low withdrawal discharge, or a high main channel velocity, the sources of lateral withdrawal were in similar ranges near the local inclined bank in the vertical direction. Under inclined slope conditions, sediment deposition near the intake entrance could be reduced, compared to that under vertical slope conditions. The results provide hydrodynamic and sediment references for engineering designs for natural rivers with inclined terrains.

A Tunable Dual‐Band Flexible Polarization Converter Based on Vanadium Dioxide Reflective Metasurface

A flexible dual‐band efficient polarization converter is realized by both coupled mode theory (CMT) analysis and numerical simulation in the microwave regime. The proposed structure can convert linearly polarized electromagnetic waves into their orthogonal components in the two sidebands. Moreover, a specular reflection performance is obtained in the central frequency band. The polarization conversion ratio (PCR) and operating bandwidth of dual band is dynamically modulated by vanadium dioxide (VO2). In the simulation results, it is shown that the proposed metasurface can achieve linear polarization conversion in 8.17–12.87 and 14.63–18.92 GHz in the insulating phase. PCRs of the dual band are 97.06% and 98.13%, the corresponding relative bandwidths (RBs) are 44.68% and 25.58%. In the metallic phase, the PCRs in 6.81–13.95 and 16.23–18.16 GHz are 91.12% (RB = 68.79%) and 96.92% (RB = 11.22%). The analyses of the phase difference (u–v coordinate system) and the surface current are given to explain the mechanisms of dual‐band and high PCR. The simulation results are in good agreement with those of CMT. Furthermore, the structure has a robust response to the oblique incidence angle (up to 30°) and has polarization insensitivity. The proposed metasurface has great potential applications in antenna radiation, biosensing, and stealth technology.

Petrogenesis of Jurassic granitic plutons in the Yanbian area, NE China: Implications for the subduction history of the Paleo-Pacific Plate

It is widely accepted that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent began during the early Mesozoic; however, the details of the subduction process remain uncertain. This paper presents new zircon U–Pb–Hf and whole-rock geochemical data for Jurassic intrusive rocks from the Yanbian area of NE China to provide a better understanding of the subduction history of the Paleo-Pacific Plate. Zircon U–Pb dating results reveal that three stages of Jurassic magmatism are recorded in the Yanbian area, namely, Early Jurassic (188–179 Ma), Middle Jurassic (172–163 Ma), and Late Jurassic (158–156 Ma). Early Jurassic intrusive rocks from the Yanbian area are predominantly calc-alkaline gabbro, gabbro-diorite, quartz monzonite, granodiorite, and syenogranite. These geochemical features and rock associations are indicative of formation in an active continental margin setting related to the initial subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The Early Jurassic granitoids were formed mainly by the partial melting of heterogeneous lower crust. The Middle Jurassic granitoids are geochemically similar to adakites and have εHf(t) values of + 2.0 to + 10.1. These rocks are inferred to have been derived from magmas generated by the partial melting of thickened juvenile lower-crustal material. Their formation was related to the subduction of the Paleo-Pacific Plate. Late Jurassic adakites in the Yanbian area formed in a compressional tectonic setting. Their negative εHf(t) values (−17.2 to − 8.6) and TDM2 ages (2025–1552 Ma) indicate that the primary magma was derived from the partial melting of ancient continental crust. Combining our data with the distribution of Late Jurassic igneous rocks in the NE Asian continental margin and the northward migration of Jurassic accretionary complexes along the margin, we conclude that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent during the Late Jurassic–earliest Early Cretaceous had a low angle of obliquity.

Associations between femoral 3D curvature and sagittal imbalance of spine.

The sagittal imbalance (SI) of spine triggers compensatory mechanisms (CMs) of lower extremity (LE) to restore trunk balance. These CMs can cause long-period stress on the femur and may possibly alter the femoral morphology. This cross-sectional observational study aimed to answer the following questions: (a) Do SI subjects exhibit greater femoral bowing compared to subjects with sagittal balance? (b) Are there associations between femoral bowing and CMs of LE in SI subjects? Subjects who underwent biplanar full body radiographs with the EOS imaging system between January 2016 and September 2021 were recruited. Sagittal parameters included T1-pelvic angle (TPA), pelvic incidence (PI), pelvic tilt (PT), sacral slope, lumbar lordosis (LL), PI-LL, and PT/PI ratio. LE parameters were femoral obliquity angle (FOA), knee flexion angle (KA), and ankle dorsiflexion angle. Femoral bowing was quantified as 3D radius of femoral curvature (RFC). Associations between 3D RFC and the radiographic parameters were analyzed. A total of 105 subjects were included, classified into balance group (TPA < 14°, n = 40), SI group (TPA ≥ 14° and KA <5°, n = 30), and SI with knee flexion group (TPA ≥ 14° and KA ≥ 5°, n = 35). 3D RFC was significantly lower in SI with knee flexion group compared to the other two groups (both p < 0.001). Stepwise linear regression showed that age, SI and knee flexion, femoral length (FL), FOA, and KA were independent predictors for 3D RFC. Greater femoral bowing is observed in subjects with SI and knee flexion compared to the balanced population. CM parameters, including KA and FOA, are associated with 3D RFC. Further longitudinal study is needed to investigate the cause-and-effect relationship between SI, CMs of LE, and femoral bowing.

Development and Investigation of the Hysteretic Behavior of an X-Shaped Metal Damper with an Oblique Angle

To investigate the hysteretic behavior of an X-shaped metal damper (XMD) with an oblique angle, cyclic loading tests were carried out on nine specimens, including two XMDs without buckling-restrained devices, four XMDs with stiffening ribs, and three XMDs with cover plates as references. The test results showed that the oblique angle could effectively increase the stiffness, strength, and energy dissipation of the XMD. When the oblique angle of an XMD with stiffening ribs increased from 0° to 30° at the applied displacement of 8.4 mm, the mean strengths and cumulative energy dissipation of specimens increased by about 80.77% and 80.57%, respectively. Although asymmetric hysteretic loops were also observed in specimens with an oblique angle and buckling-restrained devices, stable hysteretic curves were obtained. This indicated that the stiffening ribs and cover plates can effectively constrain the buckling behavior of XMDs. Additionally, the mean strengths of specimens with stiffening ribs were a little higher than those of specimens with cover plates. Subsequently, the finite element analysis models of the XMDs were proposed, in which the metal plasticity model considering isotropic and kinematical hardening was used to model the material properties of steel, and the simulation results matched well with the test results. Finally, the theoretical calculation method was proposed to predict the elastic stiffness of specimens, and the theoretical elastic stiffness matched well with the test results.

Methodology for modeling spray cooling of a cylindrical tube heated in the film boiling regime

This study examines spray cooling of horizontal, circular tubes when the surface temperature exceeds the Leidenfrost point, and the individual drop impacts are in the film boiling regime. Although film boiling is not an optimal condition for heat transfer, it is encountered in transient cooling processes or when high temperatures persist along the tube. The goal of the study is to apply existing models for drop impact and heat transfer to surfaces more complex than flat plates and to determine the overall steady state heat removal rate as an essential parameter for heat exchanger design. The spray characteristics are prescribed by a local number flux and drop size, assuming a random distribution in space and a uniform velocity of all drops. The angle of individual drop impingement on the cylindrical tube is accounted for through the maximum spreading diameter of the drop on the surface and the normal component of impact velocity. Furthermore, drop-drop interaction on the heated surface is accounted for at high local number flux values through an effective coverage area coefficient.The results are expressed in the form of a local heat transfer coefficient. These results confirm that the most influential parameters regarding heat transfer are the liquid mass flow rate in the nozzle and the drop diameter; however, they also indicate that the non-normal impact of drops over portions of the cylindrical tube leads to a highly reduced number flux; hence heat transfer. This oblique impact angle arises for one from the local spray angle, but more drastically from the curved, cylindrical surface; the latter leading to a dramatic sharp decrease in heat transfer. This is important information when considering the use of multiple spray nozzles, either circumferentially or longitudinally along the tube, since it dictates the optimal spacing between neighbouring nozzles.

Diffraction efficiency analysis of dual-layer diffractive elements with oblique incident angles.

This paper proposes a method that combines the effective area method and the oblique factors to analyze and design dual-layer diffractive optical elements at large incident angles. The method considers the effects of shadow and shield on the diffraction efficiency, as well as the correction of phase delay due to oblique incidence. The relationships among the diffraction efficiency, incident wavelengths, incident angles and period widths were analyzed with our method. A detailed comparison of the proposed method with the scalar diffraction theory is presented. The method was validated by numerical simulations of vector diffraction theory and showed similar diffraction efficiency distributions at different wavelengths and incident angles. The method provides a simple and efficient way to design and apply DLDOEs.

Femoral cartilage ultrasound echo-intensity is a valid measure of cartilage composition.

This study aimed to create a conversion equation that accurately predicts cartilage magnetic resonance imaging (MRI) T2 relaxation times using ultrasound echo-intensity and common participant demographics. We recruited 15 participants with a primary anterior cruciate ligament reconstruction between the ages of 18 and 35 years at 1-5 years after surgery. A single investigator completed a transverse suprapatellar scan with the ACLR limb in max knee flexion to image the femoral trochlea cartilage. A single reader manually segmented the femoral cartilage cross-sectional area to assess the echo-intensity (i.e., mean gray-scale pixel value). At a separate visit, a T2 mapping sequence with the MRI beam set to an oblique angle was used to image the femoral trochlea cartilage. A single reader manually segmented the cartilage cross-sectional area on a single MRI slice to assess the T2 relaxation time. A stepwise, multiple linear regression was used to predict T2 relaxation time from cartilage echo-intensity and common demographic variables. We created a conversion equation using the regression betas and then used an ICC and Bland-Altman plot to assess agreement between the estimated and true T2 relaxation time. Cartilage ultrasound echo-intensity and age significantly predicted T2 relaxation time (F = 7.33, p = 0.008, R2 = 0.55). When using the new conversion equation to estimate T2 relaxation time from cartilage echo-intensity and age, there was strong agreement between the estimated and true T2 relaxation time (ICC2,k = 0.84). This study provides promising preliminary data that cartilage echo-intensity combined with age can be used as a clinically accessible tool for evaluating cartilage composition.