Offset Configuration Research Articles

A Ku-Band Compact Offset Cylindrical Reflector Antenna with High Gain for Low-Earth Orbit Sensing Applications

The rise of CubeSats has unlocked opportunities for cutting-edge space missions with reduced costs and accelerated development timelines. CubeSats necessitate a high-gain antenna that can fit within a tightly confined space. This paper is primarily concerned with designing a compact Ku-band offset cylindrical reflector antenna for a CubeSat-based Earth Observation mission, with the goal of monitoring Arctic snow and sea ice. The development of a Ku-band offset cylindrical reflector, with a compact aperture of 110 × 149 mm2 (6.3λ × 8.5λ), is described alongside a patch array feed consisting of 2 × 8 elements. The patch array feed is designed using a lightweight Rogers substrate and is utilized to test the reflector. Adopting an offset configuration helped prevent gain loss due to feed blockage. Analyzing the reflector antenna, including the feed, thorough simulations and measurements indicates that achieving a gain of 25 dBi and an aperture efficiency of 52% at 17.2 GHz is attainable. The reflector’s cylindrical shape and compact size facilitate the design of a simple mechanism for reflector deployment, enabling the antenna to be stored within 1U. The array feed and reflector antenna have been fabricated and tested, demonstrating good consistency between the simulation and measurement outcomes.

On the interaction between a rising bubble and a settling particle

This study investigates the interaction between a freely rising, deformable bubble and a freely settling particle of the same size due to gravity. Initially, an in-line configuration is considered while varying the Bond, Galilei and Archimedes numbers. The study shows that as the bubble and particle approach each other, a liquid film forms between them that undergoes drainage. The formation of the liquid film leads to dissipation of kinetic energy, and for sufficiently large bubble velocities, particle flotation takes place. Increasing the Bond number causes the bubble to deform more severely, which may allow the particle to pass through the bubble as it ruptures. This work also considers an offset configuration, which shows that the bubble slides away from the particle, affecting its settling trajectory.

Generation of 10 kT axial magnetic fields using multiple conventional laser beams: A sensitivity study for kJ PW-class laser facilities

Strong multi-kilotesla magnetic fields have various applications in high-energy density science and laboratory astrophysics, but they are not readily available. In our previous work [Y. Shi et al., Phys. Rev. Lett. 130, 155101 (2023)], we developed a novel approach for generating such fields using multiple conventional laser beams with a twist in the pointing direction. This method is particularly well-suited for multi-kilojoule petawatt-class laser systems like SG-II UP, which are designed with multiple linearly polarized beamlets. Utilizing three-dimensional kinetic particle-in-cell simulations, we examine critical factors for a proof-of-principle experiment, such as laser polarization, relative pulse delay, phase offset, pointing stability, and target configuration, and their impact on magnetic field generation. Our general conclusion is that the approach is very robust and can be realized under a wide range of laser parameters and plasma conditions. We also provide an in-depth analysis of the axial magnetic field configuration, azimuthal electron current, and electron and ion orbital angular momentum densities. Supported by a simple model, our analysis shows that the axial magnetic field decays owing to the expansion of hot electrons.

Time-gated photon counting in both confocal and offset configurations for cost-effective enhancement of functional near-infrared spectroscopy

Time-gated photon counting in both confocal and offset configurations for cost-effective enhancement of functional near-infrared spectroscopy

Design and multi-body dynamic analysis of inline and offset track configuration in deep-sea mining vehicles for enhanced traction in soft seabed

The deep sea polymetallic nodule mining vehicle maneuverability depends on the vehicle track parameters and track configuration. The traction force offered by the deep sea soil is very limited for the mining vehicle during dynamic operating conditions on the seabed and it is very critical to maneuver against the external resistances. The present study strives to arrive at optimum track parameters for enhancing the traction of the vehicle for the pre-determined seabed conditions. The efficacy of the four tracks in Inline and Offset track configurations on the soft soil has been compared. To improve the traction force estimation, the existing mathematical model was modified with the inclusion of dynamic variation of shear stress-shear displacement characteristics and variation in shear residual displacement concerning the track parameters. The modified mathematical model was solved in a well-established mathematical tool and found that there are 30 percent improvements in the traction force generation for the offset configuration over inline track configuration. The optimum track length to width ratio (L/b) was also estimated for the given contact area to configure the vehicle track for improvement of the traction. Further, a Multi-Body Dynamic (MBD) analysis has been carried out in commercially available soil-machine interaction tool for the inline and offset track configurations with actual measured seabed soil parameters. The MBD analysis proved that the sinkage and vehicle gradient is significantly increased in the inline track configuration due to disturbance created by the front tracks. The simulation results confirm that the offset track configuration is suitable for the deep sea soil conditions for handling the higher payload of a deep sea mining vehicle.

Kinematic models for Cable-driven Continuum Robots with multiple segments and varying cable offsets

Cable-driven Continuum Robots (CCRs) represent a subset of flexible robotic systems with diverse applications encompassing medical, quality control, and search and rescue. Multi-segmented CCRs can independently actuate different CCR segments and deform into a series of connected circular arcs. While this method generates constant-curvature profiles, CCRs with varying radial cable offsets can generate shapes with varying curvatures. However, there are no kinematic models for such robots in the literature. This paper introduces optimization-based formulations to accurately estimate the deformed profile of CCRs, considering both variable cable offset and multi-segment configurations. The presented kinematic approach can predict the deformed profiles with an RMS error less than 5% of the total length of the robot. The application of the proposed method to determine the inverse kinematics of multi-segmented CCRs is demonstrated—even considering obstacles in the robot’s workspace. Practical implementation of the formulation is illustrated using a 3-segmented CCR with a cable-driven soft gripper that imitates biological grippers such as an elephant’s trunk or creeper vine to grasp objects.

Numerical study on wake recovery of vertical-axis wind turbines through fixed blade pitch offsets: H vs X rotors

This study assesses the wake recovery mechanism between an H-type Darrieus and an X-type vertical-axis wind turbine, named H-Rotor and X-Rotor respectively for different blade pitch offset configurations. The analysis is conducted in OpenFOAM using the actuator line method to model the turbines to present qualitative (velocity and vorticity contours) and quantitative (available power) studies for three different fixed blade pitch offsets. The results demonstrate that the H-Rotor recovers the wake much faster than the X-Rotor at positive pitch offsets. Overall, applying fixed pitch offsets to VAWT blades helps recover the wake faster than having no blade pitch offset.

EHD gas pump as a cooling device for electronic components in a horizontal channel

Previous studies have shown that electrohydrodynamic (EHD) gas pumps are a viable alternative for traditional fans. In this study, it further demonstrates that an EHD gas pump is a device particularly ideal for cooling electronic components. To this end, four electronic components which are individually mounted on each wall of a horizontal channel are cooled by a two-stage EHD gas pump. To evaluate the effectiveness of EHD gas pump, two electrode configurations are considered; aligned and offset. Three heat dissipation rates are considered: 100 W/m2, 200 W/m2 and 500 W/m2. The average surface temperature and the maximum temperature (i.e., the hot spot) of each electronic component are carefully examined. The results are compared with those obtained without using an EHD pump. It shows that an EHD pump with offset electrode configuration produces the best cooling effect as it generates more mixing of flow inside the channel. The average surface temperature and the maximum temperature on the electronic components cooled by EHD gas pump with offset configuration are lower than those cooled by EHD pump with aligned electrodes. More importantly, the results show that the performance of EHD pumps in terms of energy efficiency may be further improved when the two stages are operated in uneven voltages.

Influence of offset on osseointegration in cementless total hip arthroplasty: A finite element study.

Early aseptic loosening is caused by deficient osteointegration of the femoral stem due to increased micromotions and represents a common mode of failure in uncemented total hip arthroplasty (THA). This study hypothesized that a higher femoral offset, a smaller stem size and obesity increase femoral micromotion, potentially resulting in early aseptic loosening. A finite element analysis was conducted based on computed tomography segmented model of four patients who received a THA with a triple-tapered straight stem (Size 1, 3, 6). The influence of femoral stem offset (short neck, standard, lateral), head length (S to XXL), femoral anteversion and obesity during daily activities of fast walking and stair climbing was analyzed. The micromotions for the femoral stem zones were compared to a threshold representing a value above which only partial osseointegration is expected. The minimum femoral offset configuration compared to the maximum offset configuration (short neck stem, S head vs. lateral stem, XXL head) leads to a relative mean micromotion increase of 24% for the upper stem zone. Increasing the body weight (body mass index 30-35 kg/m2 ) increases the micromotion by 20% for all stem zones. The obese population recorded threshold-exceeding micromotions for stem sizes 1 and 3 for all offset configurations during stair climbing. Higher femoral offset, a smaller stem size, and higher loading due to obesity lead to an increase in micromotion between the prosthesis and proximal femur and represent a risk configuration for impaired osseointegration of a triple-tapered straight stem, especially when these three factors are present simultaneously.

PIV measurements of coherent vortices and turbulence production inside acoustic liner cavity with offset slit

This paper reports an experimental investigation into the vortex dynamics purely excited by periodic acoustic waves within a slit–cavity structure, which is a typical unit element of an acoustic liner for aeroengine applications. Particle image velocimetry (PIV) was used to measure the instantaneous, time-averaged and phase-dependent flow dynamics inside the slit–cavity, which is exposed to high-intensity incident acoustic waves. Different with traditional literature mainly focusing on the acoustic characteristics, we primarily analyze the coherent vortex structures and turbulence production mechanism, accompanying with the variable of slit offset ratio being taken into consideration. The results demonstrate that the acoustic waves can excite the hydrodynamic velocities exceeding almost tens of times than the acoustic particle velocity, yielding multi-scale vortex structures appearing within the enclosed volume. Comparatively, in configuration with offset slit, the maximum hydrodynamic velocities were gradually intensified by wall confinement effect. Subsequent proper orthogonal decomposition analysis revealed the coherent vortex structures and demonstrated the offset configuration will increase their energy proportions and enhance their temporal correlations. However, the phase-dependent flow results revealed that the offset slit can oppositely attenuate the kinematics of the coherent vortices, which were represented by the convection trajectories and convection speeds, especially during the initial acceleration stage. Finally, analysis on turbulence production mechanism confirmed the attenuated turbulent kinetic energy by the offset slit, which was attributed to the less generation of shear stresses.

Vortex-Breakdown Efficiency of Planar Regular Grid Structures—Towards the Development of Design Guidelines

The work presented here aims to provide design guidelines to create vortex-damping structures. A design of experiment was developed to investigate the individual and combined effects of the geometrical properties of planar regular grid structures, i.e., the wire diameter, the porosity, and the inter-grid spacing, on their vortex-breakdown performance. The simulations were carried out using a commercial unsteady RANS solver. The model relies on the Von Karman street effect to generate vortices in a pipe which are convected downstream, where they interact with an array of grids. The vortex-breakdown efficiency is characterized by the pressure drop, the residual turbulent kinetic energy, the flow homogeneity, and the size of the transmitted vortices. The wire diameter is shown to be an important design lever as it affects the level of distortion of the transmitted vortices. Increasing the number of grids augments the pressure loss, but their contribution to vortex breakdown is otherwise limited when the wire diameter is small. The influence of grid spacing strongly depends on the wire diameter and grid alignment. For instance, minimizing this gap reduces the pressure drop for the inline configurations, but increases the pressure drop for the offset configurations.

Comparison of two advanced bipolar tissue sealer/dividers for laparoscopic ovariectomy in dogs: articulating enseal G2 versus Ligasure Maryland device

BackgroundAdvanced bipolar tissue sealer/dividers provide the most reliable and efficient means of tissue dissection and blood vessel sealing in laparoscopic surgery and the techniques are continuously improved. In veterinary practice, cost-effectiveness is of major impact, leading to re-use of instruments designed and sold for single use. Two high-end devices were evaluated and compared in a highly standardized laparoscopic ovariectomy procedure in dogs: The new generation Ligasure Maryland Sealer/Divider (LMSD) with improved atraumatic curved jaw shape for delicate tissue handling and dissection and non-stick nanocoating, and the new-generation Articulating Enseal G2 (AENG2) with several proclaimed features improving surgical performance, including articulation of the forceps tip; improved tissue compression during sealing; unique offset electrode configuration; and specific nanoparticle coating minimizing thermal spread and tissue sticking. Twenty-one client-owned dogs admitted for elective laparoscopic ovariectomy were randomly assigned to one of two groups: ovariectomy using AENG2 on the left ovary and LMSD in the right ovary or vice-versa. Procedural video recordings were used to assess ovarian ligament fat score, smoke formation, occurrence of bleeding, and excision duration. Excised tissues were examined histopathologically and collateral thermal damage was scored in three anatomic zones: suspensory ligament, vascular pedicle, and uterine junction. Tissue sealers were used repeatedly following standardized cleaning protocol with instrument washing machine and ethylene oxide gas sterilization and the number of uses until device failure was recorded.ResultsExcision times were significantly increased for AENG2 (median 01:35 min) compared to LMSD (median 01:00 min). Minor hemorrhage from incomplete sealing occurred in 3 sites in 2 patients (2x AENG2, 1x LMSD) and was not significantly different between groups. Smoke production as scored on videos and thermal tissue damage scores on histopathology also did not differ between AENG2 and LMSD. Both vessel sealers could be re-used repeatedly.ConclusionAENG2 provides a good alternative to LMSD in laparoscopic ovariectomy, with only minor differences in measured variables. Subjectively, the articulating feature of AENG2 did not improve surgical performance in laparoscopic ovariectomy and the use of LMSD appeared more straight-forward for this specific procedure. However, differences in operating these devices may be subject to personal preference.

The potential of signalized offset T-intersections to accommodate new developments

An offset T-intersection splits a conventional four leg intersection into two three-leg T-intersections to reduce the number of conflicts. While the safety benefits of offset T-intersections have been widely documented, the effects on operations are not well understood. To fix that, this paper employed microsimulation modeling to investigate the differences in operational performance between offset T-intersections and four-leg standard intersections under various traffic demands, intersection spacings, and signal timing schemes for three development types: superstore, hybrid gas station, and residential area. Queue length and delay were employed as measurements of effectiveness. Based on microsimulation modeling, we found that under most of the tested scenarios, offset T-intersections were superior to four-leg intersections in terms of reducing delay for the main street traffic. In addition, we found that the left–right (L-R) offset T-intersection configuration outperformed the right-left (R-L) offset configuration in terms of preventing main-street left turn queue spillback. Based on the simulation results, the paper provided practice-ready guidelines on selecting an optimum intersection configuration for each specific development type given the volume demands and known geometric constraints for a given site.

Development of a spatially offset Raman spectroscopy probe for monitoring pharmaceutical drying

Spatially offset Raman spectroscopy (SORS) is a subset of Raman spectroscopy devised for probing subsurface compositions in non-homogenous media. An example of such media is the wet filter cake during pharmaceutical drying. This non-homogeneity poses a challenge for process monitoring as it could render the determined solvent content during drying, and the end point, inaccurate. In this study, a SORS probe was developed for the monitoring of pharmaceutical drying. The probe includes a 45° illumination point and 0–5 mm equidistant collection offsets. Using the SORS probe, solvent signal detection through variable thicknesses of dry paracetamol was examined. The solvent content during the drying of paracetamol in anisole was then monitored using the SORS probe. Partial least squares regression (PLSR) analysis was applied to evaluate the performance of offset configurations in monitoring the solvent content during drying. The results showed that the solvent signal is detected through thicknesses beyond 6 mm of paracetamol from the larger offsets of 4–5 mm. A more accurate prediction of the solvent content was obtained from larger offsets. PLSR models using offset spectra showed a decrease in estimation error up to 50 % compared to backscattering spectra, with a further decrease upon using standard normal variate pre-processing. This suggests that SORS could offer improved monitoring of pharmaceutical drying processes.

Aeroacoustic characteristics of supersonic offset jets

The offset jet configuration is one where the jet is discharged at some distance from a solid surface. Although the geometric configuration may look simple, the flow may involve several complexities. In propulsion systems, the high-speed jet generated from the rear engine of an aircraft, flowing nearby the fuselage, can be treated as an offset jet. In this work, an experimental investigation of the interaction noise due to circular high-speed offset jets is performed in an anechoic environment at different nozzle pressure ratios and offset ratios (height of the jet centerline above the plate per nozzle width). A large horizontal plate placed over a height-adjustable stand is used as the offset plate. Acoustic characteristics such as overall sound pressure level and the directivity pattern of free and offset jets are compared for different nozzle pressure ratios. The effect of offset ratio on noise characteristics is also investigated. Flow visualization is also carried out to understand the shock structure and its noise generation mechanism. Acoustic characteristics reveal that noise levels are higher for an offset jet compared to a free jet. Sound pressure levels for offset ratio 0.5 are lower than those for other offset ratios. The noise levels are higher for offset ratio 1.0 due to the presence of feedback tone. Schlieren visualization studies also corroborate the above characteristics.

Improving the gravity-rotation-excited vibration energy harvesting in offset configurations

The self-powered sensing technology based on gravity-rotation-excited vibration energy harvesting (GRE-VEH) enables information acquisition directly from rotatory machines online. However, the centrifugal effect due to the distance between the mass centroid of the energy harvester and the rotating axis (i.e., offset distance) seriously limits its broad engineering applications. To address this issue, we propose methods of using a tensile force provided by pre-deformed springs to counter the constant centrifugal force around the target rotation speed for improving the performance of the energy harvester affected by offset configurations. The GRE-VEH system with a linear spring is first studied by experiments and simulations, where a distributed-parameter model is developed and experimentally validated. The results well validate the proposed mechanism, where the performance of the harvester prototype significantly increases (by up to 1225%). A parametric study is also performed theoretically. The results indicate that the best performance improvement can be obtained by tuning the parameters related to the tensile length, the stiffness, and the damping of the spring. To enable the proposed mechanism in large centrifugal force cases, a pair of negative springs is introduced to the system for constructing a quasi-zero stiffness (QZS) structure together with the linear spring. The new GRE-VEH system is theoretically studied by an updated model, where the system's main characteristics are revealed. The simulation results well indicate the feasibility of the method using the QZS mechanism. This work paves a new way of solving the offset distance problem for the application of the GRE-VEH and also provides new insight into the application of the QZS mechanism.

Augmentation of Plate-Fin Heat Exchanger Performance with Support of Various Types of Fin Configurations

A plate fin heat exchanger PFHE is a form of compact heat exchanger CHE containing of a block of alternating layers of fins and flat separators known as parting sheets. In this paper, 3-dimensional incompressible laminar flow and heat transfer in a (PFHE) has been investigated numerically. The influences using different fin configurations and the effect of the offset of these fins, on thermal and hydro-dynamic fields are presented. The cases of study for the PFHE are established, by using the fins with different configurations (plain rectangular (PR) and it's offset (OR), plain triangular (PT) and it's offset (OT) which is a novel shape, and a novel combination of a two fin shapes, between rectangular and triangular (ORT)). The upper and lower plates are exposed to a constant heat flux and the working fluid is air where chosen under a laminar range of (Re) number (600 to 1400). The laminar flow and heat transfer is governed by continuity, momentum and energy equations. ANSYS FLUENT (2021 R1) is used to get the numerical results, based on finite volume method. One of the most utilized fins for a PFHE is the offset fin arrangement due to its higher heat change amount, adjustable structure, and enhances flow turbulence and heat transfer coefficient by interrupting the thermal boundary layer. The obtained results of using of the offset configuration increases the Nusselt number by 20.32% and 17.82% for OSF rectangular and OSF triangular, respectively as compared with the with plain configurations, as a result, a significant heat transfer enhancement is observed. And significant increase in the friction-factor is found to be 79.8% and 48.7% for OT and ORT, as compared with the PT. It can be observed that use of the OSF configuration leads to greater f-factor for triangular configuration values. In addition, the temperature fields for the primary and secondary flows were showed in a contour diagram.

Stress Distribution with Different Angulation of Implant with or without Cantilever Extension: A Systematic Review

Introduction: To systematically review the literature on stress distribution of implants with different angulation and the effect of cantilever prosthesis. Study Design: The three major electronic databases were screened: MEDLINE (via PubMed), and Scopus and Elsevier. Review: Methodological quality assessment showed sample size calculation to be reported by only one study, and follow-up did not include a large number of participants - a fact that may introduce bias and lead to misleading interpretations of the study results. Conclusions: A systematic review of the current literature showed only in vitro evidence that there is no consensus on the advantage of using an offset configuration implant compared to those in straight-line configuration, well some studies shows significant improvement of bone stress distribution when an angulated implant is under oblique loading.

Finite Element Analysis of Zirconia Dental Implant

Titanium dental implants have had new competitors in recent years, such as fixtures made of zirconia, which promise better aesthetics. The purpose of this study is to evaluate their mechanical performance in silico (Finite Element Analysis). The investigation was performed on a single tooth Patent™ Dental Implant (Zircon Medical®, Altendorf, Switzerland) in two configurations: without offset (Test I) and with offset (Test II, 1.5 mm within the cortical bone). The Patent Implant system consists of two components: the implant with integrated abutment and the fibreglass post. The components of the dental implants were tested using a compression load of 400 N along the implant axis. The results showed that the chewing load generates stress distribution on the bone, therefore, the offset configuration should be avoided.

Polarization-Insensitive Metalens and Its Applications to Reflectarrays With Polarization Diversity

A synthesized strategy for achieving polarization-insensitive metalens is proposed by imposing identical parabolic phase patterns individually on two decoupled left-handed (spin up, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma +$ </tex-math></inline-formula> ) and right-handed (spin down, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma -$ </tex-math></inline-formula> ) circular polarization (CP) channels of an anisotropic scheme. This is enabled by synergizing dynamic phases and local geometric phases within 0° and 90° rotations. As a consequence, similar focusing behavior is expected when it is illuminated by a plane wave of arbitrary polarization since any incoming wave is a superposition of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma +$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma -$ </tex-math></inline-formula> wave. Such an intriguing feature can be utilized to engineer a polarization-insensitive reflectarray/transmitarray in a shared aperture by placing a feeding source of different polarizations at its focal spot without altering the array aperture. Therein, the polarization of the meta-array is determined by its feeding which is readily to be changed in practice. For demonstration and possible applications, two reflectarrays composed of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50\times50$ </tex-math></inline-formula> elements at Ku band with one in normal and the other in offset configuration were designed and experimentally characterized. Numerical and experimental results illustrate that both reflectarrays are able to work in Dual linear polarization (LP) and Dual CP states by utilizing LP and CP horns of different orientations. Moreover, the versatile polarization-agile property does not pose a significant penalty on its radiation performance and both reflectarrays exhibit a measured peak aperture efficiency of 63.8% and 39.6%, respectively, near 14 GHz, and a 1 dB gain bandwidth more than 11.8%.