Distance Calibration Research Articles

Fast time-of-flight camera based surface registration for radiotherapy patient positioning

This work introduces a rigid registration framework for patient positioning in radiotherapy, based on real-time surface acquisition by a time-of-flight (ToF) camera. Dynamic properties of the system are also investigated for future gating/tracking strategies. A novel preregistration algorithm, based on translation and rotation-invariant features representing surface structures, was developed. Using these features, corresponding three-dimensional points were computed in order to determine initial registration parameters. These parameters became a robust input to an accelerated version of the iterative closest point (ICP) algorithm for the fine-tuning of the registration result. Distance calibration and Kalman filtering were used to compensate for ToF-camera dependent noise. Additionally, the advantage of using the feature based preregistration over an "ICP only" strategy was evaluated, as well as the robustness of the rigid-transformation-based method to deformation. The proposed surface registration method was validated using phantom data. A mean target registration error (TRE) for translations and rotations of 1.62 ± 1.08 mm and 0.07° ± 0.05°, respectively, was achieved. There was a temporal delay of about 65 ms in the registration output, which can be seen as negligible considering the dynamics of biological systems. Feature based preregistration allowed for accurate and robust registrations even at very large initial displacements. Deformations affected the accuracy of the results, necessitating particular care in cases of deformed surfaces. The proposed solution is able to solve surface registration problems with an accuracy suitable for radiotherapy cases where external surfaces offer primary or complementary information to patient positioning. The system shows promising dynamic properties for its use in gating/tracking applications. The overall system is competitive with commonly-used surface registration technologies. Its main benefit is the usage of a cost-effective off-the-shelf technology for surface acquisition. Further strategies to improve the registration accuracy are under development.

Pipeline Product Quality Testing Based on Adaptive SIFT Matching Technology

The problem of product quality testing on the assembly line is proposed SIFT-based adaptive algorithm and Harris corner supplementation, achieved through the SIFT matching the product point of view, position, brightness, distance calibration, the product matches the partition testing strategy to ensure that the product accessories The number and quality of the normative. Experimental results show that the detected speed and robustness.

Expanding the Scope of Single Molecule FRET with DNA Origami

Typical dimensions of cellular components are on the order of a few nanometers and their diverse cellular functions often involve conformational changes that require movements ranging from fractions of a nanometer up to tens of nanometers. The current state of the art tool for studying conformational dynamics is single molecule Fluorescence Resonance Energy Transfer (FRET), whereby energy transfer between two fluorescent dyes is correlated to their spatial separation; however, distance predictions made by FRET theory are only accurate in the range of ∼ 3-7 nm, and the working range is limited to below 10 nm. Furthermore, quantitative distance predictions require case-specific calibrations.Here we present a nanoscale device constructed by DNA origami that improves the quantitative accuracy of FRET distance predictions and expands its potential working range. The device integrates 3d structures built from self-assembled DNA, attachment sites for molecules of interest, sites for surface immobilization, and fluorescent markers for the direct visualization of biomolecular dimensions and dynamics by FRET. The device takes advantage of a distance calibration that can be generally applied to any molecule of interest. We have demonstrated that the device can easily achieve 1 nm distance resolution. For the purpose of proof-of-concept studies we specifically integrated a piece of double stranded DNA (dsDNA) containing a recognition sequence for Catabolite Activator Protein (CAP), which is know to bend dsDNA upon binding, between the arms of this device. The bending angle will be evaluated with single particle electron microscopy (EM), and FRET microscopy will be employed in solution to resolve real-time kinetics and deformations of CAP-DNA binding.

조명잡음에 강인한 구조광 영상기반 거리측정 센서

This paper presents an active ranging system based on laser structured-light image. The structured-light image processing is computationally efficient in comparison with the conventional stereo image processing, since the burdensome correspondence problem is avoidable. In order to achieve robustness against environmental illumination noise, an efficient image processing algorithm, i.e., integration of difference images with structured-light modulation is proposed. Distance equation from the measured structured light pixel distance and system parameter calibration are addressed in this paper. Experiments and analysis are carried out to verify performance of the proposed ranging system.

Novel response function resolves by image deconvolution more details of surface nanomorphology

A novel method of image processing is presented which relies on deconvolution of data using the response function of the apparatus. It is revealed that all the surface structures observed by digital imaging are generated by a convolution of the response function of the apparatus with the surfaces’ nanomorphology, which provided images of convoluted physical structures rather than images of real physical structures. In order to restore the genuine physical information on surface structures, a deconvolution using a novel response function of the feedback circuitry is required. At the highest resolution, that is, atomic resolution, the effect of deconvolution is at its maximum, whereas images at lower resolution are sharpened by eliminating smoothing effects and shadow effects. The method is applied to measurements of imaging by in situ scanning tunnelling microscopy (in situ STM) at atomic resolution and to imaging by in situ STM of electrocrystallization of copper on gold in electrolytes containing copper sulfate and sulfuric acid. It is suggested that the observed peaks of the recorded image do not represent atoms, but the atomic structure may be recovered by image deconvolution followed by calibration of distances, correction for drift phenomena and rotation in the plane of the surface. The technology may subsequently reveal more details of molecular adsorbents. The impact of in situ STM at atomic and lower resolution on imaging is discussed in the paper.

Evaluation of ultrasonic sensing of methanol concentration for direct methanol fuel cell

This investigation evaluates the effectiveness of the ultrasonic sensing of methanol concentration and establishes two regression models based on measurements of sound propagation speed against methanol concentration. Uncertainty analysis reveals that propagation distance and equipment sampling rate affect the accuracy of sound speed measurement. An ultrasonic blind region is present because sensitivity declines at a temperature of approximately 63 °C. The accuracy of measurement of the speed of sound is increased by the calibration of transducer distance because of variations in temperature. Increasing the transducer distance to 20 mm reduces the error between the theoretical and experimental speed of sound to 0.59 m/s. If the transducer distance is well calibrated, then the range of temperatures associated with ultrasonic blindness is reduced to 2–6 °C. Frequency shift and attenuation in the blind temperature range are also investigated, indicating that these two parameters are insensitive to methanol concentration.

Robust Calibration for Localization in Clustered Wireless Sensor Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents a robust calibration procedure for clustered wireless sensor networks. Accurate calibration of between-node distances is one crucial step in localizing sensor nodes in an ad-hoc sensor network. The calibration problem is formulated as a parameter estimation problem using a linear calibration model. For reducing or eliminating the unwanted influence of measurement corruptions or outliers on parameter estimation, which may be caused by sensor or communication failures, a robust regression estimator such as the least-trimmed squares (LTS) estimator is a natural choice. Despite the availability of the FAST-LTS routine in several statistical packages (e.g., R, S-PLUS, SAS), applying it to the sensor network calibration is not a simple task. To use the FAST-LTS, one needs to input a trimming parameter, which is a function of the sensor redundancy in a network. Computing the redundancy degree and subsequently solving the LTS estimation both turn out to be computationally demanding. Our research aims at utilizing some cluster structure in a network configuration in order to do robust estimation more efficiently. We present two algorithms that compute the exact value and a lower bound of the redundancy degree, respectively, and an algorithm that computes the LTS estimation. Two examples are presented to illustrate how the proposed methods help alleviate the computational demands associated with robust estimation and thus facilitate robust calibration in a sensor network. </para>

Role of a Texture Gradient in the Perception of Relative Size

Two theories regarding the role of a texture gradient in the perception of the relative size of objects are compared. Relational theory states that relative size is directly specified by the projective ratio of the numbers of texture elements spanned by objects. Distance calibration theory assumes that relative size is a product of visual angle and distance, once the distance is specified by the texture. Experiment 1 involved three variables: background (no texture, texture gradient patterns), the ratio of heights of the comparison stimulus to a standard (three levels), and angular vertical separation of the standard stimulus below the horizon (two levels). The effect of the retinal length of the comparison stimulus was examined in experiment 2. In both experiments, participants judged both the apparent size and distance of a comparison stimulus relative to a standard stimulus. Results suggest that the cues selected by observers to judge relative size were to some degree different from those used to judge relative distance. Relative size was strongly affected by a texture gradient and the retinal length of a comparison stimulus whereas relative distance perception was affected by relative height. When dominant cues that specify size are different from those which specify distance, relational theory might provide a better account of relative size perception than distance calibration theory.

Oxygen and carbon rich cool stars in the Cepheus region: classification of selected objects from KP2001 catalogue. I

We present moderate resolution CCD spectra and R photometry for seven KP2001 stars. We revised the spectral classification of the stars in the range λλ4000−8700A . Our photometric data confirmed the behavior of the light curves downloaded from the NSVS (Northern Sky Variability Survey) database. For KP2001-32, presented as a Mira-type variable in NSVS, we estimated absolute bolometric M b and K-band M K magnitudes as well as the distance using the period-luminosity relations. We also estimated the mass loss rate using the calibration relations between mass loss rate and K - [12] index. From the position in infrared color-color diagrams, we confirmed the photometric classification of KP2001-221 as a semiregular variable, based on the light curve of the NSVS database. For the N-type carbon star KP2001-77 we estimated distance and absolute magnitude M K using different calibration methods. For the remaining four objects we derived the absolute magnitudes and distances using our CCD spectra and published JHK S magnitudes. We discuss the nature of these objects on the basis of the obtained results.

Measurements of local flow structures of conical spouted beds by optical fibre probes

AbstractA new calibration set‐up was designed and assembled, and a comprehensive sensitivity analysis was conducted to investigate factors that may affect the calibration of the effective distance of an optical fibre particle velocity probe. It is shown that the glass window has the most significant impact on the calibration result.The optical fibre probe was then applied to measure local particle velocities and solid fractions inside a half and a full circular conical spouted bed. It is found that the overall particle velocity profiles, as well as the shapes of the spout and fountain are quite similar in both columns.

Real-Time Monitoring Primary Cardiomyocyte Adhesion Based on Electrochemical Impedance Spectroscopy and Electrical Cell−Substrate Impedance Sensing

The cell-substrate distance is a direct indicator of cell adhesion to extracellular matrix which is indispensable in cell culture. A real-time monitoring approach can provide a detailed profile of cell adhesion, so that enables the detecting of adhesion-related cell behavior. In this work, we report a novel real-time impedance-based method to record the adhesion profile of cardiomyocyte, overcoming its inscrutability due to the primary culture. Microfabricated biosensors are applied in cardiomyocyte culture after characterizing the cell-free system. Cyclic frequency scanning data of cell-related impedance are generated and automatically fit into the equivalent circuit model, which is established using electrochemical impedance spectroscopy. The data are displayed as the alteration of normalized cell-substrate distance and the essential parameters for manual electric cell-substrate impedance sensing calibration of absolute distance. The time course displays a significant decline in the equivalent cell-substrate distance, from 155.8 to 60.2 nm in the first 20 h of cardiomyocyte culture. Furthermore, the cardiomyocytes cultured in long-term medium and short-term medium (ACCT) for 10 h exhibit distinct difference in adhesion rate as well as cell-substrate distance (72 vs 68 nm).

Envelope pulsed ultrasonic distance measurement system based upon amplitude modulation and phase modulation

A novel microcomputer-based ultrasonic distance measurement system is presented. This study proposes an efficient algorithm which combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertia delay and amplitude attenuation effect when using the AM and PM envelope square wave form (APESW). The APESW ultrasonic driving wave form causes a phase inversion phenomenon in the relative wave form of the receiver. The phase inversion phenomenon sufficiently identifies the "measurement pulse" in the received wave forms, which can be used for accurate time-of-flight (TOF) measurement. In addition, combining a countertechnique to compute the phase shifts of the last cycle for TOF, the presented system can obtain distance resolution of 0.1% of the wavelength corresponding to the 40 kHz frequency of the ultrasonic wave. The standard uncertainty of the proposed distance measurement system is found to be 0.2 mm at a range of 50-500 mm. The APESW signal generator and phase detector of this measuring system are designed on a complex programmable logic device, which is used to govern the TOF measurement and send the data to a personal computer for distance calibration and examination. The main advantages of this APESW system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation.

SU‐FF‐I‐89: Performance Evaluation of a Unique Transrectal Ultrasound System

Purpose: To present a performance evaluation for a unique transrectal ultrasound probe for use in prostate seed implants. The ultrasound probe transducer moves inside the probe case while the case remains stationary. This allows imaging in different planes without moving the prostate. Sagittal and transverse plane imaging is available. Electronic longitudinal stepping and sagittal plane rotation of the transducer replaces manual/mechanical movement. Method and Materials: The ultrasound probe evaluated was the TargetScan® System from Envisioneering Medical Products (St. Louis, MO). Proper alignment of the needle template and software grid was verified, as well as electronic stepper position accuracy. Image quality was evaluated using a Multipurpose Tissue/Cyst Ultrasound Phantom (Nuclear Associates Model 84‐317). Tests included, maximum scanning depth, axial distance calibration accuracy, spatial resolution, high scatter resolution, low scatter resolution, superficial low scatter resolution, and dead zone region limit. All tests were performed with the probe immersed in a water medium. Both axial and sagittal scanning modes were tested. Results: Needle template/software grid coincidence (axial mode) was within 2mm, with most measurements being less than 1 mm. Longitudinal stepper accuracy was within 1mm. The following results apply to both sagittal and transverse scanning modes. Maximum scanning depth was approximately 60 mm in the medium. Axial distance accuracy was within 1 mm. Spatial resolution was 2mm axial, 3mm lateral. The 4 mm high and low scatter targets could be resolved. The 2 mm low scatter superficial targets could be resolved at the 2.2 cm and 4.4 cm depths for both sagittal and transverse modes. The dead zone limit was 2mm for both sagittal and transverse modes. Conclusion: The TargetScan® System has high image quality and transducer placement accuracy which makes it suitable for both diagnostic scanning as well as image guided prostate brachytherapy.

Ultrawide tuning of photonic microcavities via evanescent field perturbation

Evanescent field perturbation of an integrated microring resonator is examined as a means of achieving high-fidelity reversible tuning of photonic microcavities over large wavelength ranges. A 1.7% wavelength tuning is achieved through the use of a novel silica fiber probe that provides access to the evanescent field of an air-clad high-index-contrast ring resonator. As the microring is perturbed, the probe-ring distance is found through simultaneous nanometric distance calibration and force measurements. Experimental results agree well with theoretical tuning. Possible microelectromechanical systems implementation of this effect is discussed, as well as avenues for improvement of the tuning range.

Calibration of Distance and Size Does Not Calibrate Shape Information: Comparison of Dynamic Monocular and Static and Dynamic Binocular Vision

This study investigated the coupling of distance and size perception as well as the coupling of distance and shape perception. Each was tested in 2 ways using a targeted reaching task that simultaneously yielded measures of distance, size, and shape perception. First, feed-forward reaches were tested without feedback. Errors in size did not covary with errors in distance, but errors in shape did. Second, reaches were tested with visual feedback. Estimated distance and size became more accurate, but shape did not. The evidence indicated that distance and size perception and distance and shape perception are not coupled. These results were replicated 3 times, as we also compared performance using dynamic monocular, static binocular, and dynamic binocular vision. Performance was better with binocular than monocular vision both without and with feedback. The presence of a size gradient did not improve monocular distance perception, yielding additional evidence that distance and size perception are not coupled.

The Universality of Turbulence in the Molecular Interstellar Medium and Its Exploitation as a Distance Estimator

The turbulent energy spectrum of molecular clouds in a variety of environments is measured via principal component analysis (PCA) of spectral line imaging observations at millimeter wavelengths. Molecular clouds with known distances have been previously shown to accurately obey a universal scale dependence of turbulent velocity dispersion over spatial scales of 1-50 pc, via both standard object-based analysis and, more recently, PCA. The PCA-based spectrum is accurately obeyed such that it may be used as a distance estimator for molecular clouds with ~30% accuracy, where the error budget is contributed to strongly by input H II region distances used for the calibration. The use of 13CO spectral line data for distance estimation is examined and compared to the distance calibration established for 12CO observations. We show that distances estimated using 13CO are in good agreement with those obtained using 12CO, with a possible ~10% distance overestimation for 13CO relative to the 12CO calibration. Several molecular clouds with known distances are subjected to PCA, and we demonstrate that the universal spectrum is closely respected by all clouds; PCA-based distances estimated under the assumption of exact adherence to the universal spectrum are derived and are shown to be in excellent agreement with optically estimated distances. We examine the possibility that the PCA distance estimation method may be used to solve the kinematic distance ambiguity in the inner Galaxy. We establish how PCA may be used to diagnose severe blending of near/far emission and, in cases of little or no blending, to accurately establish the near or far distance. The inner Galaxy results provide initial support for the global validity of the universal PCA spectrum previously demonstrated for the outer Galaxy only. In conjunction with the accurate velocity information provided by millimeter wavelength spectral line data, PCA can provide useful information for studies of Galactic structure and kinematics.

CALIBRATION OF A PUSHBROOM HYPERSPECTRAL IMAGING SYSTEM FOR AGRICULTURAL INSPECTION

A method to calibrate a pushbroom hyperspectral imaging system has been demonstrated for use in agriculturalinspection where the imaged object is close to the imaging system. The method consists of a modified geometric control pointcorrection to remove smile and keystone effect from the system, and both wavelength and distance calibrations to reduce thewavelength and distance errors to less than 0.5 nm and 0.01 mm (across entrance slitwidth), respectively. Next, apixelbypixel percent reflectance calibration was performed at all wavelengths with dark current and 99% reflectancecalibrationpanel measurements, and results were verified with measurements on a certified gradient Spectralon panel withnominal values ranging from 12% to 99%. Results indicate that the method is capable of calibrating the hyperspectral systemacross the entire spectral range of the detector, but errors increase below 420 nm and above 840 nm. Further research shouldbe performed to evaluate the stability of the calibration over time, and techniques must be developed to implement thecalibration for realtime analysis.

Magnitude Estimates of Two Large Aftershocks of the 16 December 1811 New Madrid Earthquake

The three principal New Madrid mainshocks of 1811-1812 were followed by extensive aftershock sequences that included numerous felt events. Although no instrumental data are available for either the mainshocks or the aftershocks, available historical accounts do provide information that can be used to estimate magnitudes and locations for the large events. In this article we investigate two of the largest aftershocks: one near dawn following the first mainshock on 16 December 1811, and one near midday on 17 December 1811. We reinterpret original felt reports to obtain a set of 48 and 20 modified Mercalli intensity values of the two aftershocks, respectively. For the dawn aftershock, we infer a M_W of approximately 7.0 based on a comparison of its intensities with those of the smallest New Madrid mainshock. Based on a detailed account that appears to describe near-field ground motions, we further propose a new fault rupture scenario for the dawn aftershock. We suggest that the aftershock had a thrust mechanism and occurred on a southeastern limb of the Reelfoot fault. For the 17 December 1811 aftershock, we infer a M_W of approximately 6.1 ± 0.2. This value is determined using the method of Bakun et al. (2002), which is based on a new calibration of intensity versus distance for earthquakes in central and eastern North America. The location of this event is not well constrained, but the available accounts suggest an epicenter beyond the southern end of the New Madrid Seismic Zone.

Improved Angiographic Measurement Accuracy with a New Calibration System

During transcatheter interventions, correct distance measurements are mandatory for proper device selection. We present a new calibration procedure in which distance calibration is performed with a high contrast metallic rod placed in the esophagus as a scaling device. Distortion related to differences in Calibration and object planes as well as axial angles were analyzed and appropriate correction factors calculated. A cardiac phantom served to test the accuracy and precision of the new measuring system. The mean measurement error was < 1.7% (range 0.1%–4.9%), and the mean measurement variability 1% (range 0.3%–1.9%). The accuracy of angiographic measurements can be significantly improved using a calibration device in the esophagus in combination with appropiate mathematical corrections.

Diagnostic Genetic Markers and Evolutionary Relationships among Invasive Dreissenoid and Corbiculoid Bivalves in North America: Phylogenetic Signal from Mitochondrial 16S rDNA

Diagnostic genetic markers from 486 aligned nucleotide sequences of mitochondrial 16S ribosomal DNA were developed for the four closely related species of dreissenoid and corbiculoid bivalves that have invaded North America; the zebra mussel Dreissena polymorpha, the quagga mussel D. bugensis, and the dark false mussel Mytilopsis leucophaeata of the superfamily Dreissenoidea, and the Asian clam Corbicula fluminea of the sister superfamily Corbiculoidea. Evolutionary relationships were examined among the four genera and comparisons were made with native Eurasian populations of D. polymorpha and D. bugensis. Tests were conducted for gender-specific mitochondrial lineages, which occur in some other bivalves. Genetic variability and divergence rates were tested between stem (paired) and loop (unpaired) regions of secondary structure. There were 251 variable nucleotide sites, of which 99 were phylogenetically informative. Overall transition to transversion ratio was 0.76:1.00 and both accumulated linearly in stem and loop regions, suggesting appropriate phylogenetic signal. Genetic distance calibration with the fossil record estimated the pairwise sequence divergence as 0.0057 ± 0.0004 per million years. Mytilopsis and Dreissena appear to have diverged about 20.7 ± 2.7 million years ago. D. bugensis and D. polymorpha appear separated by about 13.2 ± 2.2 million years. No intraspecific variation was found, including between Eurasian and North American populations, among shallow and deep morphotypes of D. bugensis and between the sexes. Restriction endonuclease markers were developed to distinguish among the species at all life history stages, allowing rapid identification in areas of sympatric distribution.