Direct Distance Measurements Research Articles

FAKTOR RISIKO COMPUTER VISION SYNDROME PADA MAHASISWA JURUSAN ILMU KOMPUTER FAKULTAS MATEMATIKA DAN ILMU PENGETAHUAN ALAM UNIVERSITAS LAMPUNG

ABSTRACT
 
 Introduction: Computer vision syndrome (CVS) is a syndrome that occur due to excessive interaction with computers. Individual, environmental, and computer related risk factors increase CVS prevalence and cause eyes, visual, and extraocular related symptoms. This research aims to observe the relation between risk factors and CVS prevalence in students of Computer Science Major of Mathematics and Natural Sciences Faculty of Lampung University. Method: This research was an analitic survey with cross sectional study. Samples consisted of 56 students of 2014-2016 class year using proportional stratified random sampling techniques. This research used questionnaires and direct measurement of eyes distance and angle gaze of respondents. Collected datas then were analyzed by using univariate and bivariate analysis. Result: The prevalence of CVS obtained from samples was 39 students (69,6%). Statistic tests between risk factors and CVS are listed as follow, gender (p=0,909 OR=1,069), working years (p=0,007 OR=6,188), daily duration of computer exposures (p=0,022 OR=7,708), wearing spectacles (p=0,043 OR=8,000), taking a break (p=0,111 OR=2,786), eyes distance (p=0,028 OR=3,750), and angle gaze (p=0,047 OR=5,000). Conclusion: The significantly related risk factors to CVS were working years, daily duration of exposures, wearing spectacles, eyes distance, and angle gaze towards computer monitors.
 
 Keywords: computer vision syndrome, risk factors

A Uniform Intelligent Prioritisation for Solving Diverse and Big Data Generated From Multiple Chronic Diseases Patients Based on Hybrid Decision-Making and Voting Method

Telemedicine is increasingly used in the modern health care system because it provides health care services to patients amidst distant locations. However, the prioritisation process for patients with multiple chronic diseases (MCDs) over telemedicine is becoming increasingly complex due to diverse and big data generated from multiple disease conditions. To solve such a problem, massive datasets must be collected, and high velocity must be acquired, specifically in real-time processing. This process requires decision-making (DM) regarding the emergency degree of each chronic disease for every patient. Multi-criteria decision-making (MCDM) approaches (i.e. direct aggregation, distance measurement and compromise ranking) are the main solutions for dealing with this complex situation. However, each MCDM approach provides a unique rank from those of other methods. By far, the preferred DM approach that can provide an ideal rank better than other approaches has not been established. This study proposes an extension of the technique for reorganising opinion order to interval levels (TROOIL). Such an extension is called Hybrid DM and Voting Method (HDMVM) which is based on different DM approaches (i.e. direct aggregation, distance measurement and compromise ranking). HDMVM is used to prioritise big data of patients with MCDs in real-time through the remote health-monitoring procedure. In this paper, we propose a methodology that is based on three sequential stages. The first stage illustrates how the big data of patients with MCDs can be recognised in the telemedicine environment and identifies the target telemedicine tier in this study. The second stage describes the steps of the proposed HDMVM sequentially. The third stage applies the proposed method by prioritising the case study of big data of patients with MCDs based on the above DM approaches. Moreover, dataset of remote patients with MCDs (n = 500 ) is adopted, which contains three diseases, namely, chronic heart diseases and high and low blood pressures. The prioritisation results vary among direct aggregation, distance measurement and compromise approaches. The proposed HDMVM effectively provides a uniform and final ranking result for big data of patients with MCDs. A statistical method (i.e. mean) is performed to objectively validate the ranking results. Significant differences between the scores of the groups are identified in the objective validation, signifying identical ranking results. The evaluation of the proposed work with the benchmark study indicates that this study has tackled issues relevant to big data and diversity of MCDM approaches in the prioritisation of patients with MCDs.

Local resolution of the Hubble tension: The impact of screened fifth forces on the cosmic distance ladder

The discrepancy between the values of the Hubble constant $H_0$ derived from the local distance ladder and the cosmic microwave background provides a tantalising hint of new physics. We explore a potential resolution involving screened fifth forces in the local Universe, which alter the Cepheid calibration of supernova distances. In particular, if the Cepheids with direct distance measurements from parallax or water masers are screened but a significant fraction of those in other galaxies are not, neglecting the difference between their underlying period--luminosity relations biases the local $H_0$ measurement high. This difference derives from a reduction in the Cepheid pulsation period and possible increase in luminosity under a fifth force. We quantify the internal and environmental gravitational properties of the Riess et al. distance ladder galaxies to assess their degrees of screening under a range of phenomenological models, and propagate this information into the $H_0$ posterior as a function of fifth force strength. We consider well-studied screening models in scalar--tensor gravity theories such as chameleon, K-mouflage and Vainshtein, along with a recently-proposed mechanism based on baryon--dark matter interactions in which screening is governed by local dark matter density. We find that a fifth force strength $\sim5-30\%$ that of gravity can alleviate (though not resolve) the $H_0$ tension in some scenarios, around the sensitivity level at which tests based on other distance ladder data can constrain this strength. Although our analysis is exploratory and based on screening models not necessarily realised in full theories, our results demonstrate that new physics-based local resolutions of the $H_0$ tension are possible, supplementing those already known in the pre-recombination era.

Inter-leg Distance Measurement as a Tool for Accurate Step Counting in Patients with Multiple Sclerosis.

Step detection is commonly performed using wearable inertial devices. However, methods based on the extraction of signals features may deteriorate their accuracy when applied to very slow walkers with abnormal gait patterns. The aim of this study is to test and validate an innovative step counter method (DiSC) based on the direct measurement of inter-leg distance. Data were recorded using an innovative wearable system which integrates a magneto-inertial unit and multiple distance sensors (DSs) attached to the shank. The method allowed for the detection of both left and right steps using a single device and was validated on thirteen people affected by multiple sclerosis (0 <; EDSS <; 6.5) while performing a six-minute walking test. Two different measurement ranges for the distance sensor were tested (DS200: 0-200 mm; DS400: 0-400 mm). Accuracy was evaluated by comparing the estimates of the DiSC method against video recordings used as gold standard. Preliminary results showed a good accuracy in detecting steps with half the errors in detecting the step of the instrumented side compared to the non-instrumented (mean absolute percentage error 2.4% vs 4.8% for DS200; mean absolute percentage error 2% vs 5.4% for DS400). When averaging errors across patients, over and under estimation errors were compensated, and very high accuracy was achieved (E%<; 1.2% for DS200; E%<; 0.7% for DS400). DS400 is the suggested configuration for patients walking with a large base of support.

Cosmological inference from standard sirens without redshift measurements

The purpose of this work is to investigate the prospects of using the future standard siren data without redshift measurements to constrain cosmological parameters. With successful detections of gravitational wave (GW) signals an era of GW astronomy has begun. Unlike the electromagnetic domain, GW signals allow direct measurements of luminosity distances to the sources, while their redshifts remain to be measured by identifying electromagnetic counterparts. This leads to significant technical problems for almost all possible BH-BH systems. It is the major obstacle to cosmological applications of GW standard sirens. In this paper, we introduce the general framework of using luminosity distances alone for cosmological inference. The idea is to use the prior knowledge of the redshift probability distribution for coalescing sources from the intrinsic merger rates assessed with population synthesis codes. Then the posterior probability distributions for cosmological parameters can be calculated. We demonstrate the performance of our method on the simulated mock data and show that the luminosity distance measurement would enable an accurate determination of cosmological parameters up to 20% uncertainty level. We also find that in order to infer H0 to 1% level with flat ΛCDM model, we need about 105 events.

Feedback-Based Target Localization in Underwater Sensor Networks: A Multisensor Fusion Approach

This paper investigates the problem of target localization in underwater sensor networks, subjected to limited measurement range and accuracy. The localization process is mainly divided into two phases, i.e., distance estimation and position solving. In the first phase, some sensor nodes cannot acquire the direct distance measurements of target, due to the high-dynamic and strong-noise characteristics of underwater environment. Based on this, we formulate the distance measurement as a closed-loop control problem, and then a proportional-integral estimator is designed for sensors to acquire the distance information through indirect measurements. With the estimated distance information, a consensus-based unscented Kalman filtering (UKF) algorithm is proposed in the second phase to localize the target, where direct and indirect measurements are fused to reduce the influence of malicious data. Moreover, stability conditions are provided to show that the distance estimator can stabilize the closed-loop system, while the boundedness analyses are demonstrated to guarantee the localization accuracy. Finally, simulation results reveal that the proposed distance estimator can extend the measurement range of sensors by comparing with the single direct measurement. Meanwhile, the consensus-based UKF algorithm can effectively improve the localization accuracy.

A wearable solution for accurate step detection based on the direct measurement of the inter-foot distance

Accurate step detection is crucial for the estimation of gait spatio-temporal parameters. Although several step detection methods based on the use of inertial measurement units (IMUs) have been successfully proposed, they may not perform adequately when the foot is dragged while walking, when walking aids are used, or when walking at low speed. The aim of this study was to test an original step-detection method, the inter-foot distance step counter (IFOD), based on the direct measurement of the distance between feet. Gait data were recorded using a wearable prototype system (SWING2DS), which integrates an IMU and two time-of-flight distance sensors (DSs). The system was attached to the medial side of the right foot with one DS positioned close to the forefoot (FOREDS) and the other close to the rearfoot (REARDS). Sixteen healthy adults were asked to walk over ground for two minutes along a loop, including both rectilinear and curvilinear portions, during two experimental sessions. The accuracy of the IFOD step counter was assessed using a stereo-photogrammetric system as gold standard. The best performance was obtained for REARDS with an accuracy higher than 99.8% for the instrumented foot step and 88.8% for the non-instrumented foot step during both rectilinear and curvilinear walks. Key features of the IFOD step counter are that it is possible to detect both right and left steps by instrumenting one foot only and that it does not rely on foot impact dynamics. The IFOD step counter can be combined with existing IMU-based methods for increasing step-detection accuracy.

Evaluating flow management as a strategy to recover an endangered sturgeon species in the Upper Missouri River, USA

AbstractIn the Upper Missouri River, Fort Peck and Garrison Dams limit the length of free‐flowing river available to the endangered pallid sturgeon. These barriers restrict the upstream migration of adults and downstream larval dispersal. A one‐dimensional (1D) modelling framework is currently in use to evaluate reservoir operation alternatives and to simulate drift of dispersing free embryos for different flow regimes and reservoir stages. This paper presents the results of a large‐scale tracer experiment conducted in 2016 and associated modelling performed to evaluate flow management scenarios that might aid species recovery. Breakthrough curves from the tracer experiment were used to infer the 1D longitudinal dispersion coefficient from a parameter optimization procedure. Simulations generated using the calibrated 1D advection–dispersion model were compared with field observations of the passive tracer and with larval fish collected during a previous experiment in 2007. When used with the appropriate range of dispersion coefficients, the 1D modelling framework agrees well with the available direct measurements of larval drift distances. Although we cannot unequivocally state whether insufficient length of free‐flowing river alone is causing recruitment failure, given the current thermal regime and our understanding of pallid sturgeon development, the time required for pallid sturgeon to transition to the benthos and initiate feeding might exceed the duration of drift available given constraints of reservoir operations.

Flight behavior of targeted fishes depends on variables other than fishing

Behavioral changes due to human predation can affect the functional role of targeted fishes and has implications for ecosystem and fisheries management. Wariness of targeted fishes towards divers, often measured as flight initiation distance (FID), has been shown to increase in areas where spear fishing pressure is higher. Additional research is required to understand how these patterns vary among different species and places. To support such studies, there is a need to explore the relationship of approach starting distance (SD) and other variables that influence measures of fish wariness. We used stereo video to record FID, a new direct measure of minimum approach distance (dMAD), and escape responses of targeted reef fishes in a marine reserve and heavily fished area in Hawai’i. We investigated the role of SD and 15 other variables in influencing FID and dMAD and tested differences between the reserve and fished area. SD explained a large portion of the variability in FID and somewhat less variability in dMAD. FID and dMAD were higher when fishes were travelling (vs feeding), increased with fish body length, and decreased with depth. When including these co-variates in models of FID and dMAD of targeted reef fishes, we found significant differences between study sites for dMAD, though not for FID. We also found differences in escape responses between sites. Based on these results, we recommend using stereo video to conduct measures of dMAD as a complement or alternative to FID, while simultaneously measuring SD and collecting additional data such as escape response. Relative effect sizes of SD and, to a lesser extent, other co-variates were large in comparison to site. Studies that use similar methods and do not control for or incorporate SD may produce biased results with regard to the effects of fishing pressure on flight behavior of targeted fishes.

Distributed Circular Formation Control of Nonholonomic Vehicles Without Direct Distance Measurements

This note presents a static distributed formation control law for nonholonomic vehicles subject to velocity constraints, such that the controlled vehicles travel along a common circle with the given center and radius, while maintaining a desired spaced formation. The center is assumed to be known to only some vehicles. The proposed controller does not require any communication and only uses local measurements based on a sensor graph of which the topology is modeled by a directed graph satisfying a certain acyclic condition. Moreover, direct distance measurements are not needed. Finally, the simulation results of an example verify the effectiveness of the proposed controller.

Revealing two radio-active galactic nuclei extremely near PSR J0437−4715

Newton's gravitational constant $G$ may vary with time at an extremely low level. The time variability of $G$ will affect the orbital motion of a millisecond pulsar in a binary system and cause a tiny difference between the orbital period-dependent measurement of the kinematic distance and the direct measurement of the annual parallax distance. PSR J0437$-$4715 is the nearest millisecond pulsar and the brightest at radio. To explore the feasibility of achieving a parallax distance accuracy of one light-year, comparable to the recent timing result, with the technique of differential astrometry, we searched for compact radio sources quite close to PSR J0437$-$4715. Using existing data from the Very Large Array and the Australia Telescope Compact Array, we detected two sources with flat spectra, relatively stable flux densities of 0.9 and 1.0 mJy at 8.4 GHz and separations of 13 and 45 arcsec. With a network consisting of the Long Baseline Array and the Kunming 40-m radio telescope, we found that both sources have a point-like structure and a brightness temperature of $\geq$10$^7$ K. According to these radio inputs and the absence of counterparts in the other bands, we argue that they are most likely the compact radio cores of extragalactic active galactic nuclei rather than Galactic radio stars. The finding of these two radio active galactic nuclei will enable us to achieve a sub-pc distance accuracy with the in-beam phase-referencing very-long-baseline interferometric observations and provide one of the most stringent constraints on the time variability of $G$ in the near future.

Spline-Based Initialization of Monocular Visual–Inertial State Estimators at High Altitude

Due to the lack of direct distance measurements, robust and accurate state estimation at high altitude but GPS-denied environments is a challenging task. A possible solution is monocular visual–inertial estimators, in which visual and inertial measurements are properly fused to recover the metric estimates. However, these estimators suffer from initialization under poor numerical conditioning or even degeneration, due to difficulties in retrieving observations of visual features with sufficient parallax, and the excessive period of inertial measurement integration. In this letter, we introduce the joint formulation into the spline-based high altitude estimator initialization method for monocular visual–inertial navigation system, in which the fitting of the spline and the alignment of visual measurements and inertial measurements are jointly optimized to recover metric estimates. The method ensures that sufficient excitation is contained in the inertial measurements when initialized, which eliminates the numerical issues. Compared with the work of Liu and Shen, the joint formulation makes our initialization method insensitive to the choice of spline parameters. Thus, the adaptivity to various environments and motions is obtained, as well as higher accuracy. The method is applicable for both loosely coupled and tightly coupled visual–inertial estimators. Extensive experiments are conducted to validate our approach.

VINS-Mono: A Robust and Versatile Monocular Visual-Inertial State Estimator

A monocular visual-inertial system (VINS), consisting of a camera and a low-cost inertial measurement unit (IMU), forms the minimum sensor suite for metric six degrees-of-freedom (DOF) state estimation. However, the lack of direct distance measurement poses significant challenges in terms of IMU processing, estimator initialization, extrinsic calibration, and nonlinear optimization. In this work, we present VINS-Mono: a robust and versatile monocular visual-inertial state estimator.Our approach starts with a robust procedure for estimator initialization and failure recovery. A tightly-coupled, nonlinear optimization-based method is used to obtain high accuracy visual-inertial odometry by fusing pre-integrated IMU measurements and feature observations. A loop detection module, in combination with our tightly-coupled formulation, enables relocalization with minimum computation overhead.We additionally perform four degrees-of-freedom pose graph optimization to enforce global consistency. We validate the performance of our system on public datasets and real-world experiments and compare against other state-of-the-art algorithms. We also perform onboard closed-loop autonomous flight on the MAV platform and port the algorithm to an iOS-based demonstration. We highlight that the proposed work is a reliable, complete, and versatile system that is applicable for different applications that require high accuracy localization. We open source our implementations for both PCs and iOS mobile devices.

H0LiCOW – IV. Lens mass model of HE 0435−1223 and blind measurement of its time-delay distance for cosmology

Strong gravitational lenses with measured time delays between the multiple images allow a direct measurement of the time-delay distance to the lens, and thus a measure of cosmological parameters, particularly the Hubble constant, $H_{0}$. We present a blind lens model analysis of the quadruply-imaged quasar lens HE 0435-1223 using deep Hubble Space Telescope imaging, updated time-delay measurements from the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL), a measurement of the velocity dispersion of the lens galaxy based on Keck data, and a characterization of the mass distribution along the line of sight. HE 0435-1223 is the third lens analyzed as a part of the $H_{0}$ Lenses in COSMOGRAIL's Wellspring (H0LiCOW) project. We account for various sources of systematic uncertainty, including the detailed treatment of nearby perturbers, the parameterization of the galaxy light and mass profile, and the regions used for lens modeling. We constrain the effective time-delay distance to be $D_{\Delta t} = 2612_{-191}^{+208}~\mathrm{Mpc}$, a precision of 7.6%. From HE 0435-1223 alone, we infer a Hubble constant of $H_{0} = 73.1_{-6.0}^{+5.7}~\mathrm{km~s^{-1}~Mpc^{-1}}$ assuming a flat $\Lambda$CDM cosmology. The cosmographic inference based on the three lenses analyzed by H0LiCOW to date is presented in a companion paper (H0LiCOW Paper V).

CLUSTERING OF LOCAL GROUP DISTANCES: PUBLICATION BIAS OR CORRELATED MEASUREMENTS? IV. THE GALACTIC CENTER

ABSTRACT Aiming at deriving a statistically well-justified Galactic Center distance, R 0, and reducing any occurrence of publication bias, we compiled the most comprehensive and most complete database of Galactic Center distances available to date, containing 273 new or revised R 0 estimates published since records began in 1918 October until 2016 June. We separate our R 0 compilation into direct and indirect distance measurements. The latter include a large body of estimates that rely on centroid determinations for a range of tracer populations, as well as measurements based on kinematic observations of objects at the solar circle, combined with a mass and/or rotational model of the Milky Way. Careful assessment of the Galactic Center distances resulting from orbital modeling and statistical parallax measurements in the Galactic nucleus yields our final Galactic Center distance recommendation of . The centroid-based distances are in good agreement with this recommendation. Neither the direct measurements nor the post-1990 centroid-based distance determinations suggest that publication bias may be important. The kinematics-based distance estimates are affected by significantly larger uncertainties, but they can be used to constrain the Galaxy’s rotation velocity at the solar galactocentric distance, . Our results imply that the International-Astronomical-Union-recommended Galactic Center distance ( ) needs a downward adjustment, while its recommendation ( km s−1) requires a substantial upward revision.

What can VLBI astrometry tell us about AR Sco?

AbstractWe proposed to carry out high precision very long baseline interferometry (VLBI) observations of AR Sco, a pulsing white dwarf (WD) - M dwarf (MD) binary, to provide a direct distance measurement with the e-EVN (European VLBI Network) at 5 GHz. By the proposed parallax measurement on AR Sco, not only the precise distance will be determined, but also some physical parameters, such as the luminosity, the mass and the magnetic field will be significantly tightened accordingly, even the gravitational wave amplitude from this unique binary system can be tightly constrained. In addition, the EVN observations will allow us to answer that whether there is an extended emission structure associated with AR Sco, which will help us to explain the stable continuum radio emission observed during the pulse-off state.

Shrinkage of freeze-dried cryosections of cells: Investigations by EFTEM and cryo-CLEM

Freeze-drying of cryosections of cells or tissues is considered to be the most efficient preparation for microanalysis purpose related to transmission electron microscopy. It allows the measurements of ions and water contents at the ultrastructural level. However an important drawback is associated to freeze-drying: the shrinkage of the cryosections. The aim of this paper is the investigation of this phenomenon by means of three different methods applied to both hydrated and dehydrated cryosections: direct distance measurements on fiducial points, thickness measurements by energy filtered transmission microscopy (EFTEM) and cryo-correlative light electron microscopy (cryo-CLEM). Measurements in our experimental conditions reveal a lateral shrinkage around 10% but the most important result concerns the lack of differential shrinkage between most of the cellular compartments.

Directional Clustering Through Matrix Factorization.

This paper deals with a clustering problem where feature vectors are clustered depending on the angle between feature vectors, that is, feature vectors are grouped together if they point roughly in the same direction. This directional distance measure arises in several applications, including document classification and human brain imaging. Using ideas from the field of constrained low-rank matrix factorization and sparse approximation, a novel approach is presented that differs from classical clustering methods, such as seminonnegative matrix factorization, K -EVD, or k -means clustering, yet combines some aspects of all these. As in nonnegative matrix factorization and K -EVD, the matrix decomposition is iteratively refined to optimize a data fidelity term; however, no positivity constraint is enforced directly nor do we need to explicitly compute eigenvectors. As in k -means and K -EVD, each optimization step is followed by a hard cluster assignment. This leads to an efficient algorithm that is shown here to outperform common competitors in terms of clustering performance and/or computation speed. In addition to a detailed theoretical analysis of some of the algorithm's main properties, the approach is empirically evaluated on a range of toy problems, several standard text clustering data sets, and a high-dimensional problem in brain imaging, where functional magnetic resonance imaging data are used to partition the human cerebral cortex into distinct functional regions.

High-Throughput Live-Cell Microscopy Analysis of Association Between Chromosome Domains and the Nucleolus in S. cerevisiae.

Spatial organization of the genome has important impacts on all aspects of chromosome biology, including transcription, replication, and DNA repair. Frequent interactions of some chromosome domains with specific nuclear compartments, such as the nucleolus, are now well documented using genome-scale methods. However, direct measurement of distance and interaction frequency between loci requires microscopic observation of specific genomic domains and the nucleolus, followed by image analysis to allow quantification. The fluorescent repressor operator system (FROS) is an invaluable method to fluorescently tag DNA sequences and investigate chromosome position and dynamics in living cells. This chapter describes a combination of methods to define motion and region of confinement of a locus relative to the nucleolus in cell's nucleus, from fluorescence acquisition to automated image analysis using two dedicated pipelines.

Mean-value at risk portfolio efficiency: approaches based on data envelopment analysis models with negative data and their empirical behaviour

We deal with the problem of an investor who is using a mean-risk model for accessing efficiency of investment opportunities. Our investor employs value at risk on several risk levels at the same time which corresponds to the approach called risk shaping. We review several data envelopment analysis (DEA) models which can deal with negative data. We show that a diversification–consistent extension of the DEA models based on a directional distance measure can be used to identify the Pareto–Koopmans efficient investment opportunities. We derive reformulations as chance constrained, nonlinear and mixed-integer problems under particular assumptions. In the numerical study, we access efficiency of US industry representative portfolios based on empirical distribution of random returns. We employ bootstrap and jackknife to investigate the empirical properties of the efficiency estimators.