Offset Measurements Research Articles

Comparison of Scheimpflug tomography, Placido disc, and combined Placido Scheimpflug in the measurement of pupil offset in myopic population.

This study aimed to compare the consistency of pupil offset measurements obtained using the Pentacam, Keratron Scout, and Sirius devices. This retrospective cross-sectional study included 146 young myopic individuals (292 eyes) scheduled for refractive surgery at Dalian Third People's Hospital between January 2023 and December 2023. Three devices were utilized to measure the chord mu of the pupil deviation along with the Cartesian distances of the X and Y coordinates (Px, Py) associated with the pupil offset. Repeated-measures analysis of variance was used to compare differences in pupil offset acquisition across various devices. Additionally, the intraclass correlation coefficient (ICC) and Bland-Altman plot were utilized to assess the consistency among the three devices. Chord mu, measured using the Pentacam, Keratron Scout, and Sirius devices, were 0.18 ± 0.10, 0.21 ± 0.11, and 0.18 ± 0.11, respectively. The Px values were 0.00 ± 0.14, -0.02 ± 0.16, and -0.01 ± 0.13, respectively, while the Py values were 0.09 ± 0.13, 0.10 ± 0.15, and 0.10 ± 0.13. The ICCs for the three device measurements, chord mu, Px, and Py, were 0.817, 0.900, and 0.855, respectively. When comparing the three devices, the 95% limits of agreement (LoA) for mu and Px measured using the Sirius and Keratron Scout were the narrowest, ranging from -0.15 to 0.08 and -0.11 to 0.13, respectively. Additionally, the 95% LoA for Py measured using the Sirius and Pentacam was the narrowest, ranging from -0.13 to 0.15. The pupil centers in both eyes were predominantly located above the apex of the cornea. Sirius, Keratron Scout, and Pentacam have good consistency in pupil shift measurement in young myopic patients, and the three devices can be used as references in clinical practice.

Limited Preservation of Strike‐Slip Surface Displacement in the Geomorphic Record

AbstractOffset geomorphic markers are commonly used to interpret slip history of strike‐slip faults and have played an important role in forming earthquake recurrence models. These data sets are typically analyzed using cumulative probability methods to interpret average amounts of slip in past earthquakes. However, interpretation of the geomorphic record to infer surface slip history is complicated by slip variability, measurement uncertainty, and modification of offset features in the landscape. To investigate how well geomorphic data record surface slip, we use offset measurements from recent strike‐slip surface ruptures (n = 39), faults with geomorphic evidence of multiple strike‐slip earthquakes (n = 29), and synthetic slip distributions with added noise (n10,000) to examine the constraints of the geomorphic record and the underlying assumptions of the cumulative offset probability distribution analysis method. We find that the geomorphic record is unlikely to resolve more than two paleo‐slip distributions, except in specific cases with low slip variability, high slip‐per‐event, and semiarid climate. In cases where site‐specific conditions allow for interpretation of more than two earthquakes, lateral extrapolation along a fault is not straightforward because on‐fault displacement and distributed deformation may be spatially variable in each earthquake. We also find that average slip in modern earthquakes is adequately recovered by probability methods, but the reported prevalence of strike‐slip faults with characteristic slip history is not supported by geomorphic data. We also propose updated methods to interpret slip history and construct uncertainty bounds for paleo‐slip distributions.

Two-Way Single-Photon Laser Time Transfer for High-Speed Moving Platforms

The two-way laser time transfer technology, based on single-photon detection, is among the techniques requiring the least weight and power consumption for ultra-long-distance clock synchronization. It holds promise as the most viable technology for high-accuracy inter-satellite clock synchronization, particularly for small satellites that are highly sensitive to weight and power consumption. In this study, we analyze laser time transfer in fast-moving platforms and find that not only does the relative motion speed between platforms significantly impact the clock offset measurement, but also the components of each platform’s relative motion velocity are critical. We introduce a lightweight scenario for laser time transfer, capable of achieving high-precision and high-accuracy interstellar clock offset measurements within a 5000 km range using high repetition rate microchip lasers and single-pixel single-photon detectors. With a speed accuracy of ±0.06 m/s, the precision of clock offset measurement surpasses 3 ps at full width at half maximum (FWHM), making it suitable for high-speed and high-precision clock synchronization between near-Earth satellites.

Theoretical framework for calibrating the depth-dependent optical scattering in layered human skin using spatially offset measurements.

Spatially offset spectroscopy offers an alternative non-invasive method for enabling deep probing of structures and chemical molecules, which is clinically significant for the characterization of chemical and physical alterations in human skin. However, a more precise depth-resolved quantification using the spatially offset measurements still remains a challenge due to the mixed inhomogeneous scattering. Herein, we report a Monte-Carlo-based quantification modeling platform combined with a novel, to the best of our knowledge, scattering spectrum decomposition method to explore the depth-dependent optical scattering contributions in human skin. In the simplified modeling, human skin was empirically set to be composed of multiple layers, and each layer possessed different photon weights for the spatially offset scattering intensity measurements. The modeling results of photon transportation in-and-out of the layered skin substantially discovered that the layer-dependent scattering contribution was compositely encoded into the spatially offset measurements and varied with the illumination incidence angle. For calibrating the layer-dependent scattering contribution, a modified nonlinear independent component processing algorithm was applied to the spatially offset measurements by decomposing the photon weights of each layer. The calibration results figured out the major scattering contribution of each layer along the offset axis under different incidence angles, which were consistent with previous experimental observations. The proposed theoretical framework establishes a feasible approach for spatially offset optical spectroscopies enabling non-invasive quantitative A-line characterization of the concentrations of skin components.

Accuracy of Cup Placement Angle, Leg Lengthening, and Offset Measurement Using an AR-Based Portable Navigation System: Validation in Supine and Lateral Decubitus Positions for Total Hip Arthroplasty

Background and Objectives: Total hip arthroplasty (THA) requires accurate implant placement to ensure optimal outcomes. In this study, the AR Hip navigation system, an imageless portable navigation tool using augmented reality (AR), was evaluated for measuring radiographic inclination (RI), anteversion (RA), leg lengthening (LL), and offset (OS) changes in supine and lateral decubitus THA. Notably, this is the first report to assess the accuracy of LL and OS measurements using AR technology. Methods: We analyzed 48 hips from primary THA patients: 17 in the supine (S) group and 31 in the lateral (L) group. RI, RA, LL, and OS were measured intraoperatively using AR Hip and postoperatively using Zed Hip 3D software (Version 18.0.0.0). The absolute errors and outlier rates (≥5° for RI/RA and ≥5 mm for LL/OS) were compared between groups. Results: The mean intraoperative RI values with AR Hip were 40.1 ± 0.6° (S), 40.2 ± 1.2° (L), and 40.1 ± 1.0° (total), while the postoperative RI values with Zed Hip were 39.7 ± 2.9° (S), 39.5 ± 2.5° (L), and 39.6 ± 2.6° (total). The absolute errors were 1.8 ± 1.7° (total), with no significant group differences (p = 0.957). For RA, the errors were 2.0 ± 1.2° (total) (p = 0.771). The LL errors were 2.3 ± 2.2 mm (total) (p = 0.271), and the OS errors were 3.5 ± 2.8 mm (total) (p = 0.620). The outlier rates for RI were 11.8% (S) and 3.2% (L); for RA, 0% (S) and 3.2% (L); for LL, 29.4% (S) and 6.5% (L) with a significant difference (p = 0.031); and for OS, 23.5% (S) and 25.8% (L). No significant differences were observed for RI, RA, or OS. Conclusions: AR Hip provided accurate measurements of cup orientation, LL, and OS in both supine and lateral THA. Importantly, this study is the first to report the accuracy of LL and OS measurements using AR technology, demonstrating the potential of AR Hip for improving THA precision.

Change in grounding line location on the Antarctic Peninsula measured using a tidal motion offset correlation method

Abstract. The grounding line position of glaciers and ice shelves is an essential observation for the study of the Earth's ice sheets. However, in some locations, such as the Antarctic Peninsula, where many grounding lines have not been mapped since the 1990s, remote sensing of grounding line position remains challenging. Here we present a tidal motion offset correlation (TMOC) method for measuring the grounding line position of tidewater glaciers and ice shelves, based on the correlation between tide amplitude and synthetic aperture radar offset tracking measurements. We apply this method to the Antarctic Peninsula Ice Sheet to automatically delineate a new grounding line position for 2019–2020, with near complete coverage along 9300 km of coastline, updating the 20-year-old record. A comparison of the TMOC grounding line to contemporaneous interferometrically measured grounding line position shows the method has a mean seaward offset compared to interferometry of 185 m and a standard deviation of 295 m. Our results show that over the last 24 years there has been grounding line retreat at a number of fast-flowing ice streams on the Antarctic Peninsula, with the most retreat concentrated in the north-eastern sector, where grounding lines have retreated following the collapse of ice shelves. We observe a maximum grounding line retreat since 1996 of 16.3 ± 0.5 km on Hektoria Glacier, with other notable glaciers retreating by 9.3 ± 0.5, 9.1 ± 0.5 and 3.6 ± 0.5 km. Our results document dynamic change on Antarctic Peninsula glaciers and show the importance of using an updated grounding line location to delineate the boundary between floating and grounded ice.

Quantum state exclusion through offset measurement

Quantum state exclusion through offset measurement

High-Precision Bi-Directional Beam-Pointing Measurement Method Based on Space Solar Power Station System.

In the process of wireless energy transmission from a Space Solar Power Station (SSPS) to a satellite, the efficiency of energy transmission is closely related to the accuracy of beam control. The existing methods commonly ignore the impact of array position, structural deviation of the transmitting antenna, and modulation errors, which leads to the deviation error in actual energy transmission beams and the reduction of energy transmission efficiency. This paper innovatively proposes a high-precision bi-directional beam-pointing measurement method, which provides a technical basis for advancing the beam-pointing control accuracy from the perspective of improving the beam-pointing measurement accuracy. The method consists of (1) the interferometer goniometry method to realize high-precision guiding beam pointing measurement; and (2) the power field reconstruction method to realize offset angle measurement of the energy-transmitting beam. Simulation results demonstrate that under dynamic conditions, the guiding beam-pointing measurement accuracy of this method reaches 0.05°, which is better than the traditional 0.1° measurement accuracy based on the guiding beam. The measurement accuracy of the offset distance of the energy center is better than 0.11 m, and the measurement accuracy of the offset angle is better than 0.012°.

Reliability of the Sundsvall Method for Femoral Offset Evaluation.

Acetabular and femoral offset (FO) play an important role in total hip arthroplasty (THA). The Sundsvall method has been proposed to account for both FO and cup offset in one global hip offset measurement. In this study, we examine the agreement and inter-observer reliability of the Sundsvall method of hip offset measurement. Four hundred and ninety-nine THA patients at a single tertiary academic institution were retrospectively reviewed. Preoperative hip offset was measured on anteroposterior radiographs of the pelvis on the operative and contralateral side. Hip offset was also measured postoperatively on the operative side. Hip offset was measured using the Sundsvall method as the distance between the femoral axis and midline of the pelvis at the height of the lateral most point of the greater trochanter. All measurements were completed by two raters. Intra-class correlation coefficients (ICC) and Pearson's correlation coefficients were used to evaluate agreement and inter-observer reliability between two raters. There was excellent agreement between raters for preoperative hip offset measurement with an ICC of 0.91 (confidence interval [CI] 0.90-0.93, P<0.01) and R=0.92. There was excellent agreement between raters for postoperative hip offset with an ICC of 0.93 (CI 0.92-0.94, P<0.01) and R=0.93. This study confirms the inter-observer agreement and reliability of the Sundsvall method of hip offset measurement. With its high agreement and reliability, the Sundsvall method is an easy and reliable way to measure hip offset that can be applied in future clinical and research settings.

Forest conservation as a CO2 offset measure: a case of an urban development project in Finland

Forest conservation as a CO2 offset measure: a case of an urban development project in Finland

Active elimination of DC bias current of a SiC based dual active bridge by controlling the dead time period

AbstractDual active bridge (DAB) is an isolated DC‐DC converter gaining wider attention in power electronics applications. The high frequency (HF) transformer is an integral part of the DAB which is prone to saturation. Silicon carbide (SiC) based DAB are generally preferred for highly efficient power conversions, calling for an extremely low DC resistance of the transformer. This aggravates the DC bias issue significantly. The DC bias current generally flows due to the mismatch in static and transient switching of active devices, leading to eventual saturation of the transformer. This paper proposes an active method to precisely control the dead time of the devices (8–100 ns) without sacrificing the voltage utilization of the converter. This method does not require a sophisticated DC offset current measurement technique. The field programmable gate array (FPGA) based control platform on the gate driver side executes the proposed algorithm. The proposed control is experimentally verified in a 5 kW SiC based converter. The control implementation methodology is discussed with the support of necessary experimental results.

Brightest Cluster Galaxy Offsets in Cold Dark Matter

The distribution of offsets between the brightest cluster galaxies of galaxy clusters and the centroid of their dark matter distributions is a promising probe of the underlying dark matter physics. In particular, since this distribution is sensitive to the shape of the potential in galaxy cluster cores, it constitutes a test of dark matter self-interaction on the largest mass scales in the universe. We examine these offsets in three suites of modern cosmological simulations; IllustrisTNG, MillenniumTNG and BAHAMAS. For clusters above , we examine the dependence of the offset distribution on gravitational softening length, the method used to identify centroids, redshift, mass, baryonic physics, and establish the stability of our results with respect to various nuisance parameter choices. We find that offsets are overwhelmingly measured to be smaller than the minimum converged length scale in each simulation, with a median offset of in the highest resolution simulation considered, TNG300-1, which uses a gravitational softening length of . We also find that centroids identified via source extraction on smoothed dark matter and stellar particle data are consistent with the potential minimum, but that observationally relevant methods sensitive to cluster strong gravitational lensing scales, or those using the the “light traces mass” approach, in this context meaning gas is used as a tracer for the potential, can overestimate offsets by factors of ∼10 and ∼30, respectively. This has the potential to reduce tensions with existing offset measurements which have served as evidence for a nonzero dark matter self-interaction cross section.

Next generation gravel road profiling – The potential of advanced UAV drone in comparison with road surface tester and rotary laser levels

Over the last decades, significant progress has been made and new approaches have been proposed for efficient collection of road condition data. Gravel roads are crucial for connecting urban and rural areas in Sweden, constituting a significant portion of the road network. Therefore, this study addresses the use of a developed Unmanned Aerial Vehicle (UAV)-based digital imaging system focusing on efficient collection of surface condition data over gravel roads.The study focuses on in-situ profile measurements of a gravel road located in Trosa, Sweden, using three different profiling methods: UAV drone with RTK technology, Road Surface Tester (RST), and Rotary Laser Level (RLL) to explore the agreement between these methods.The UAV drone, equipped with Real-Time Kinematic (RTK) technology, captures high-resolution images to produce detailed 3D surface models, overcoming the challenges posed by adverse weather conditions. Notable outcomes reveal RTK technology's stability, maintaining a steady 3D position accuracy below 2 cm. To enhance synchronization and comparison between different profiling methods, efforts should be made to standardize coordinate systems and measurement analysis software.Minimum average absolute differences of 1.1 cm, 1 cm, and 0.7 cm were recorded for all profiles (from 1 m left to 1 m right of the road centerline) in the comparisons between UAV drone – RST, UAV drone – RLL, and RST – RLL methods, respectively. This underlines the significant advancement in UAV drone technology, enabling remarkably accurate measurements of vertical offsets for profiling the tested gravel road despite the high altitude at which the UAV drone operates.

Decreasing Hip Offset in Total Hip Arthroplasty Results in Decreased Physical Function Scores

BackgroundAcetabular and femoral offset play an important role in total hip arthroplasty (THA) for postoperative stability and biomechanical function. However, it is unknown whether offset impacts patient-reported outcomes (PROs). This study evaluated patients undergoing direct anterior (DA) THA with the hypothesis that patients who have a decrease in hip offset postoperatively would have lower physical function scores and higher pain interference. MethodsThere were 499 patients who underwent DA THA at a single tertiary academic institution who were retrospectively evaluated. Preoperative and postoperative hip offset was measured by 2 reviewers using the Sundsvall method on standing anteroposterior pelvis radiographs. Postoperative changes in hip offset were categorized as increased (> 5 mm), matched (within 5 mm of the preoperative offset measurement), or decreased ( >5 mm). Postoperative PROs with a minimum 1-year follow-up were recorded. A one-way analysis of variance was utilized to compare postoperative pain and PROs between groups. ResultsPatients who had decreased offset had the lowest mean postoperative physical function scores at 39.4 (8.0), followed by the increased offset group at 42.2 (10.4) and the matched offset group at 42.8 (9.8) (P < .01). There were significant differences in postoperative physical function scores between matched offset (42.8) and decreased offset (39.4) groups (P < .01), as well as between increased offset (42.2) and decreased offset (39.4) groups (P = .04). There was no difference between matched and increased offset cohorts. ConclusionsOur data suggests that reducing hip offset may result in worse physical function scores compared to those who have matched or increased hip offset. This should be considered intraoperatively, and efforts should be made to avoid reduced offset even in the presence of hip stability.

Beverage Deterioration Monitoring Based on Surface Tension Dynamics and Absorption Spectrum Analysis

Biochemical information sensing has always been one of the challenges in ubiquitous sensing research for mobile computing. Microorganisms will cause undetectable deterioration in drink production, such as wine and beverage, and microbial contamination is highly susceptible during storage like some liquors can be bottled for sometimes over ten years. Microbial culture methods are common for quality monitoring but unsuitable for real-time beverage quality monitoring. As far as we know, we are the first to use ubiquitous sensing for real-time microbial contamination detection. We designed a lightweight monitoring system called Microbe-Radar, which uses light signals to monitor real-time beverage quality. Microbe-Radar uses eight LEDs and a photodiode to detect fine-grained surface tension and absorption spectrum changes caused by microbial metabolites and growth during deterioration. Characteristic offset degree measurement and absorption spectrum dimension expansion are two critical technologies. Moreover, we implemented countermeasures against ambient light noise and sloshing interference. Microbe-Radar's surface tension and absorption spectrum measurement errors are only 0.89 mN/m and 2.4%, respectively, making identifying the contamination duration, microorganism content, and microorganism composition worthwhile. Experiments showed Microbe-Radar could determine potential issues with liquor quality when the liquid becomes health-threatening or even just contaminated, with an accuracy of 97.5%. Microbe-Radar can also be extended to beverage deterioration warning, with deterioration prediction accuracy of more than 90.6% for five beverages (milk, apple juice, etc.).

Evaluation of the methodical framework for the management of uncertainty in the context of the integration of sensory functions

AbstractAs digitalization progresses, the development and integration of sensory functions in technical systems become increasingly important. Managing uncertainty, especially in the early phase of this process, is crucial to ensure the reliability of the data provided. Therefore, a methodical framework for the identification, analysis and consideration of uncertainty was presented in prior works. In this contribution, the effectivity of the framework is evaluated by applying it to a sensory function for rotational speed and offset measurement of a disk pack coupling using sensor integrating bolts.

Single-shot frequency offset measurement with HASTE using the selective parity approach.

Measurements of frequency offset are commonly required in MRI. The standard method measures the signal phase as a function of evolution time. Here we use a single shot turbo-spin-echo acquisition method to measure frequency offset at a single evolution time. After excitation the transverse magnetisation evolves during the evolution time, and is then repeatedly refocused. The phase is conjugated between alternate echoes. Using partial parallel acquisition techniques we obtain separate odd- and even- echo images. An iterative procedure ensures self-consistency between them. The difference in phase between the two images yields frequency offset maps. The technique was implemented at 3 Tesla and tested on a healthy human volunteer for a range of evolution times between 6 and 42ms. A standard method using a similar readout train and multiple evolution times was used as a gold-standard measure. In a statistical comparison with the gold standard no evidence for bias or offset was found. There was no systematic variation in precision or accuracy as a function of evolution time. We conclude that the presented approach represents a viable method for the rapid generation of frequency offset maps with a high image quality and minimal distortion.

Preoperative surgical planning in total hip arthroplasty: pitfalls and pearls for femoral offset measurements

Preoperative surgical planning in total hip arthroplasty: pitfalls and pearls for femoral offset measurements

Big Cities, Big Impacts? A spatial analysis of 3,335 ecological offsets in France since 2012

This paper assesses the French policy of mitigation hierarchy, with the aim of no net loss of biodiversity, by studying the geographical aspects of the application of the concept of ecological offsets in equivalence between losses and gains using spatialized data. We seek to know whether the dynamics of urban and interurban development (notably built-up and transport infrastructures) lead to a spatially integrated implementation of biodiversity offsets taking into account local characteristics and areas under pressure from land artificialization. Our main finding reveals that the majority of ecological offsets are generated by projects related to transport infrastructures (38%) and urban planning and construction projects (23%). However, if there are fewer, the ecological offsets of projects such as waste storage or energy development are mostly located in natural preserved areas, revealing a potential risk of non additionnality of offset measures and a risk that the private sector (through ecological offsets) will gradually replace the state in the protection of biodiversity. Our analysis also points out that despite the diversity of projects, habitats and protected species across France, there is a typical spatial layout profile of ecological offsets, pleading for a “one size fits all” offsetting in the French policy context of tenuous regulators’ availability in time and competence level due to weakness of refresh training and downsizing of public services in the environment. This last result argues for a stronger control from environmental agencies between two tremendously tricky concepts of offsetting, the equivalence valuation methods and the adjustments coefficients (time delay and ecological risk), to drive ecological offsetting future decisions at local but above all regional- and national-level planning documents.

High-resolution co-seismic fault offsets of the 2023 Türkiye earthquake ruptures using satellite imagery

On February 6, 2023, southern Türkiye was struck by two large earthquakes at 01:17 UTC (Mw=7.8, Pazarcık, Kahramanmaraş) and 10:30 UTC (Mw = 7.6, Elbistan, Kahramanmaraş), causing severe damage at the complex junction of the Dead Sea Fault (DSF), the Cyprus Arc and the East Anatolian Fault Zone (EAFZ). The ruptures propagated along several known strands of the southwestern termination of the EAFZ, the main Pazarcık and Karasu valley faults, and the Çardak-Sürgü fault. Here we present the high-resolution mapping of the entire coseismic surface rupture and an estimate of the rupture width, total and on-fault offset, and diffuse deformation obtained a few days to three months after the two mainshocks. The mapping is derived from image correlation of Sentinel-2 optical satellite imagery and validated with offset measurements collected on the ground. We find that the ruptures extend over lengths of 310 km and 140 km for the Mw 7.8 and Mw 7.6 mainshocks, respectively. The maximum offsets reach 7.5 ± 0.8 m and 8.7 ± 0.8 m near the epicenters of the Mw 7.8 and Mw 7.6 events, respectively. We propose a segmentation of the two ruptures based on these observations, and further discuss the location of the potential supershear rupture. The use of optical image correlation, complemented by field investigations along earthquake faults, provides new insights into seismic hazard assessment.