Final Location Research Articles

An accurate fault location method for distribution network based on active transfer arc-suppression device

Active transfer arc-suppression device is a kind of arc suppression device which has been widely used in the distribution network. When a single-phase grounding fault occurs, the bus of faulty phase is actively grounded metallicity in the substation to limit the voltage of faulty phase, so as to realize arc extinction. In this paper, an accurate fault location method is proposed for the distribution network equipped with active transfer arc-suppression device. According to the variation characteristics of the fault traveling wave signals before and after arc-suppression device operation, the fault location formula based on the traveling wave velocity difference of different modes and the fault location formula based on the mutation of aerial-mode traveling wave are combined to obtain the final fault location method that is not affected by ground-mode wave velocity. The proposed method expands the function of active transfer arc-suppression device, makes it have additional fault location ability, and greatly improves the economy of the device. Simulation verifies that the proposed method is not affected by fault conditions, soil resistivity and extreme fault. The absolute error is within 50 m in all cases, which has high reliability.

Research on the Controlling Process in Autonomous Driving

With the development of science and technology, self-driving automobile will become increasingly available in the future, and our lives will become more convenient with them. Autocar is in an area of robotics, belonging to the service field. It can be used to make our lives better and reduce the cost of human driving the car, thus will have a great effect on human’s life. However, people do not understand the mechanism of self-driving quite clearly, it is necessary to present some basic operating process and related algorithms of the automatic cars. Meanwhile, in order to show how a self-driving car could control itself using various sensors and algorithms, which is also the basic idea of the automobile company to make a new autocar. Different sensors that are able to detect the behavior of the self-driving cars are used in this paper to fit in different algorithm that follows the principles of motion and robotics. It is concluded that the car could theoretically drive safely, and could avoid crashing to other cars, people or barriers with the safety algorithm. Also, the car could follow the traffic rules properly and plan the most efficient route to get to the final location.

Multi-algorithm UWB-based localization method for mixed LOS/NLOS environments

Ultra-wideband (UWB) is considered the most promising radio technology for high-accuracy indoor localization because of its many desirable properties, including a sub-decimeter level ranging accuracy under line-of-sight (LOS) conditions, resilience to multipath fading, and low duty cycles. However, the accuracy of UWB localization deteriorates significantly in complex indoor environments due to the presence of non-light-of-sight (NLOS) propagation that may introduce a considerable positive bias in range measurements. In this paper, we present a localization method that improves the accuracy of UWB localization in mixed LOS/NLOS indoor environments by using multiple localization algorithms optimized for different localization scenarios distinguished by the number of LOS-measured distances. The method adopts a fingerprinting-based algorithm to obtain location results under NLOS-only conditions and uses the conventional multilateration algorithm when at least three LOS-measured distances are available. Additionally, the algorithm set includes two novel hybrid localization algorithms for scenarios with one or two LOS distances. These algorithms use the LOS-measured distances to limit geometrically possible locations and then employ fingerprinting to perform the final location selection. We test our approach in a realistic indoor environment over numerous experimental scenarios. The experimental results show that the proposed localization strategy reduces the mean distance error by 3 to 20 cm compared with the traditional fingerprinting-based approach.

NTFS Data Tracker: Tracking file data history based on $LogFile

The $LogFile is a file system metafile that stores NTFS (New Technology File System) transaction data. It is used to restore the file system to its normal state in the event of a file system error, such as one caused by sudden power outages. The transaction data recorded in $LogFile contain changes in the metadata of files and directories in the $MFT. By analyzing it, all file operations performed in the file system during a specific period can be identified. Existing research on the $LogFile has focused on finding file-level events including create, delete, move and rename. Research has also been conducted on file data in $LogFile to acquire data location information (data runs) that is initially stored at the time of file creation, or to reconstruct only the final location information of the data. No research, however, has been conducted to date on tracking the entire history of changes in the file data. In this paper, we develop a technique that reproduces changes in the metadata within the $MFT on a file-by-file basis by using transaction data recorded in the $LogFile to overcome the limitations of existing research in the area. We use this technique to track all data on the history of a given file according to changes in it over time from its creation to deletion. An NTFS Data Tracker is also developed based on the results and various example use cases are discussed.

Application of an explainable AI method in classification of functional foot conditions

In human motion analysis predictive or functional methods are used to estimate the location of the hip joint centre (HJC). It has been shown that the Harrington regression equations (HRE) and geometric sphere fit (GSF) method are the most accurate predictive and functional methods, respectively. To date, the comparative reliability of both approaches has not been assessed. The aims of this study were to (1) compare the reliability of the HRE and the GSF methods, (2) analyse the impact of the number of thigh markers used in the GSF method on the reliability, (3) evaluate how alterations to the movements that comprise the functional trials impact HJC estimations using the GSF method, and (4) assess the influence of the initial guess in the GSF method on the HJC estimation. Fourteen healthy adults were tested on two occasions using a three-dimensional motion capturing system. Skin surface marker positions were acquired while participants performed quite stance, perturbed and non-perturbed functional trials, and walking trials. Results showed that the HRE were more reliable in locating the HJC than the GSF method. However, comparison of inter-session hip kinematics during gait did not show any significant difference between the approaches. Different initial guesses in the GSF method did not result in significant differences in the final HJC location. The GSF method was sensitive to the functional trial performance and therefore it is important to standardize the functional trial performance to ensure a repeatable estimate of the HJC when using the GSF method.

Utilization of 3D MRI for the Evaluation of Sphincter Pharyngoplasty Insertion Site in Patients With Velopharyngeal Dysfunction.

Sphincter pharyngoplasty is a surgical method to treat velopharyngeal dysfunction. However, surgical failure is often noted and postoperative assessment frequently reveals low-set pharyngoplasties. Past studies have not quantified pharyngoplasty tissue changes that occur postoperatively and gaps remain related to the patient-specific variables that influence postoperative change. The purpose of this study was to utilize advanced three-dimensional imaging and volumetric magnetic resonance imaging (MRI) data to visualize and quantify pharyngoplasty insertion site and postsurgical tissue changes over time. A prospective, repeated measures design was used for the assessment of craniometric and velopharyngeal variables postsurgically. Imaging was completed across two postoperative time points. Tissue migration, pharyngoplasty dimensions, and predictors of change were analyzed across imaging time points. Significant differences were present between the initial location of pharyngoplasty tissue and the pharyngoplasty location 2 to 4 months postoperatively. The average postoperative inferior movement of pharyngoplasty tissue was 6.82 mm, although notable variability was present across participants. The pharyngoplasty volume decreased by 30%, on average. Inferior migration of the pharyngoplasty tissue was present in all patients. Gravity, scar contracture, and patient-specific variables likely interact, impacting final postoperative pharyngoplasty location. The use of advanced imaging modalities, such as 3D MRI, allows for the quantification and visualization of tissue change. There is a need for continued identification of patient-specific factors that may impact the amount of inferior tissue migration and scar contracture postoperatively.

New Constraints on Pluto’s Sputnik Planitia Ice Sheet from a Coupled Reorientation–Climate Model

Abstract We present a coupled reorientation and climate model, to understand how true polar wander (TPW) and atmospheric condensation worked together to create the Sputnik Planitia (SP) ice sheet and reorient it to its present-day location on Pluto. SP is located at 18°N, 178°E, very close to the anti-Charon point, and it has been previously shown that this location can be explained by TPW reorientation of an impact basin as it fills with N2 ice. We readdress that hypothesis while including a more accurate treatment of Pluto’s climate and orbital obliquity cycle. Our model again finds that TPW is a viable mechanism for the formation and present-day location of SP. We find that the initial impact basin could have been located north of the present-day location, at latitudes between 35°N and 50°N. The empty basin is constrained to be 2.5–3 km deep, with enough N2 available to form at most a 1–2 km thick ice sheet. Larger N2 inventories reorient too close to the anti-Charon point. After reaching the final location, the ice sheet undergoes short periods of sublimation and recondensation on the order of 10 m of ice, due to Pluto’s variable obliquity cycle, which drives short periods of reorientation of a few kilometers. The obliquity cycle also has a role in the onset of infilling; some initial basin locations are only able to begin accumulating N2 ice at certain points during the obliquity cycle. We also explore the sensitivity of the coupled model to albedo, initial obliquity, and Pluto’s orbit.

Accuracy of electroanatomical mapping-guided cardiac radiotherapy for ventricular tachycardia: pitfalls and solutions.

To analyse and optimize the interobserver agreement for gross target volume (GTV) delineation on cardiac computed tomography (CCT) based on electroanatomical mapping (EAM) data acquired to guide radiotherapy for ventricular tachycardia (VT). Electroanatomical mapping data were exported and merged with the segmented CCT using manual registration by two observers. A GTV was created by both observers for predefined left ventricular (LV) areas based on preselected endocardial EAM points indicating a two-dimensional (2D) surface area of interest. The influence of (interobserver) registration accuracy and availability of EAM data on the final GTV and 2D surface location within each LV area was evaluated. The median distance between the CCT and EAM after registration was 2.7 mm, 95th percentile 6.2 mm for observer #1 and 3.0 mm, 95th percentile 7.6 mm for observer #2 (P = 0.9). Created GTVs were significantly different (8 vs. 19 mL) with lowest GTV overlap (35%) for lateral wall target areas. Similarly, the highest shift between 2D surfaces was observed for the septal LV (6.4 mm). The optimal surface registration accuracy (2.6 mm) and interobserver agreement (Δ interobserver EAM surface registration 1.3 mm) was achieved if at least three cardiac chambers were mapped, including high-quality endocardial LV EAM. Detailed EAM of at least three chambers allows for accurate co-registration of EAM data with CCT and high interobserver agreement to guide radiotherapy of VT. However, the substrate location should be taken in consideration when creating a treatment volume margin.

Trajectory Design for Throughput Maximization in UAV-Assisted Communication System

In this paper, we study an unmanned aerial vehicle (UAV) assisted communication system to provide service to the ground users. We address the problem of UAV deployment in three-dimensional (3D) space to provide on-demand coverage to the users such that their sum rate is maximized. First, we find the optimal UAV location in 3D space where the sum rate is maximized for all ground users. Thereafter an optimal trajectory is designed for the UAV to travel from the initial to the optimal location, such that the overall average sum rate during the flight is maximized while meeting the on-board energy availability and flight duration constraints. The problem formulated is non-convex. To obtain the optimal location, we approximate the rate expression to obtain the concave regions and apply alternating optimization. An iterative scheme is proposed to obtain the optimal UAV trajectory, which computes the optimal location in each time slot sequentially, followed by a greedy approach to reach the final location. Simulation results provide useful insights into the optimal location and the UAV trajectory problem and show on an average 16.5% improvement over the benchmark schemes.

Deliberative Decision-Making in Macaques Removes Reward-Driven Response Vigor.

Most of our daily decisions are governed by one of two systems: an impulsive system driving instantaneous decisions and a deliberative system driving thoughtful ones. The impulsive system reacts to immediately available concrete rewards. In contrast, the deliberative system reacts to more delayed rewards and/or punishments, which imposes consideration of longer-term choice consequences. Contingency management for addiction treatment is hypothesized to engage deliberative processes. Ultimately, in both decision-making situations, an action is needed to enact the decision. Whether those actions differ in implementation is an open question whose answer could inform as to whether distinct neural systems are engaged. To explore whether there is evidence of separate mechanisms between deliberated and immediate choices, we trained monkeys to perform a decision-making task where they made a choice on a touch screen between two visual cues predicting different amounts of reward. In immediate choice (IC) trials, the cues appeared at the final response locations where subjects could immediately touch the chosen cue. In deliberated choice (DC) trials, compound cues appeared orthogonally to the response locations. After a delay, allowing for decision formation, an identifying cue component was displaced to the randomly assigned response locations, permitting subjects to reach for the chosen cue. Both trial types showed an effect of cue value on cue selection time. However, only IC trials showed an effect of the competing cue on response vigor (measured by movement duration) and a reach trajectory that deviated in the direction of the competing cue, suggesting a decision reexamination process. Reward modulation of response vigor implicates dopaminergic mechanisms. In DC trials, reach trajectories revealed a commitment to the chosen choice target, and reach vigor was not modulated by the value of the competing cue. Our results suggest that choice–action dynamics are shaped by competing offers only during instantaneous, impulsive choice. After a deliberated decision, choice–action dynamics are unaffected by the alternative offer cue, demonstrating a commitment to the choice. The potential relevance to contingency management is discussed.

Assessing Potential Stock Structure of Adult Coho Salmon in a Small Alaska Watershed: Quantifying Run Timing, Spawning Locations, and Holding Areas with Radiotelemetry

AbstractRun timing and spatial locations of spawning habitats are often used to identify stocks for conservation planning or management of salmonid fishes. Although complex stock structure is most common within large watersheds with diverse habitats, even small drainages can produce multiple co‐occurring spatially or temporally isolated populations or “stocks.” This project sought to address the potential existence of stock structure of Coho Salmon Oncorhynchus kisutch in a small coastal watershed on Kodiak, Alaska that supports vital subsistence and recreational fisheries and is currently managed as a single stock. We radio‐tagged a total of 348 adult Coho Salmon upon freshwater entry into the Buskin River across three spawning seasons (2015–2017) and tracked in‐river movements to the final locations where mortality signals were recorded. We identified two primary spawning habitats within the system: main‐stem and lake tributaries, with 54% (range of 47% to 61%) of tagged fish with determined fates tracked to main‐stem river spawning areas and 46% (range 39% to 53%) presumably spawning in small tributaries of the 1‐km2 Buskin Lake at the headwater of the watershed. Despite distinct spatial differences in spawning locations, main‐stem and tributary spawners did not differ in migration timing into freshwater (difference in run timing of main‐stem versus tributary spawners = 1 d) nor body size (main‐stem mean body length, mideye to tail fork = 625 mm, tributary mean = 613 mm). Unexpectedly, we determined nearly 70% of all Coho Salmon spent at least some time in Buskin Lake, including 54% of main‐stem spawners, suggesting a potential role of Buskin Lake as an important staging habitat for premature migrating adult Coho Salmon who enter freshwater in advance of final maturation. We also identified areas consistently used for holding prior to spawning that could be used in spatial management planning and during times of necessary conservation to ensure integrity of the stock for the future.

Kajian Landing Station Alat Deteksi Dini Tsunami Berbasis Kabel Serat Optik Bawah Laut di Kabupaten Pasangkayu, Sulawesi Barat

The construction of an underwater fiber-optic cable-based tsunami early detection system is planned to be installed in the Makassar Strait with a landing point in West Sulawesi. Land infrastructure such as a Power House (PH), a communication tower, and a Beach Manhole (BMH) is needed to sustain the system's power in order to survive. Therefore, the aim of this scientific paper is to study several alternative landing station locations in Pasangkayu, West Sulawesi and then determine the priority locations. The methods used to achieve these objectives are field observation methods and secondary data analysis based on parameters of land area conditions, environmental conditions, supporting infrastructure, social conditions and licensing systems, and marine activities. These aspects are then assessed to determine the priority of the selected location. The location selected based on the assessment carried out is ALT-02B. In succession, the three priority locations selected from the order of most priority to least priority are ALT-02B, ALT-02A, and ALT-06. This selected priority location is not necessarily the final choice location to be used in the construction of a tsunami early detection system land infrastructure because in the process there are still things to be considered and aspects that are made the main priority for consideration in making decisions.

Localization of cementoenamel junction in intraoral ultrasonographs with machine learning

ObjectiveOur goal was to automatically identify the cementoenamel junction (CEJ) location in ultrasound images using deep convolution neural networks (CNNs). MethodsThree CNNs were evaluated using 1400 images and data augmentation. The training and validation were performed by an experienced nonclinical rater with 1000 and 200 images, respectively. Four clinical raters with different levels of experience with ultrasound tested the networks using the other 200 images. In addition to the comparison of the best approach with each rater, we also employed the simultaneous truth and performance level estimation (STAPLE) algorithm to estimate a ground truth based on all labelings by four clinical raters. The final CEJ location estimate was obtained by taking the first moment of the posterior probability computed using the STAPLE algorithm. The study also computed the machine learning-measured CEJ–alveolar bone crest distance. ResultsQuantitative evaluations of the 200 images showed that the comparison of the best approach with the STAPLE-estimate yielded a mean difference (MD) of 0.26 mm, which is close to the comparison with the most experienced nonclinical rater (MD=0.25 mm) but far better than the comparison with clinical raters (MD=0.27–0.33 mm). The machine learning-measured CEJ–alveolar bone crest distances correlated strongly (R = 0.933, p < 0.001) with the manual clinical labeling and the measurements were in good agreement with the 95% Bland–Altman's lines of agreement between −0.68 and 0.57 mm. ConclusionsThe study demonstrated the feasible use of machine learning methodology to localize CEJ in ultrasound images with clinically acceptable accuracy and reliability. Likelihood-weighted ground truth by combining multiple labels by the clinical experts compared favorably with the predictions by the best deep CNN approach. Clinical significanceIdentification of CEJ and its distance from the alveolar bone crest play an important role in the evaluation of periodontal status. Machine learning algorithms can learn from complex features in ultrasound images and have potential to provide a reliable and accurate identification in subsecond. This will greatly assist dental practitioners to provide better point-of-care to patients and enhance the throughput of dental care.

Scheduling heterogeneous delivery tasks on a mixed logistics platform

Large e-commerce retailers usually establish their own logistics systems. Such systems make use of their own dedicated fleets but will also use a crowdsourced delivery mode by hiring occasional fleets. These mixed logistics systems with both dedicated and occasional fleets serve both retailers’ internal delivery tasks and external tasks requested by local businesses. This paper studies the problem of scheduling heterogeneous (internal and external) delivery tasks on a mixed logistics platform with multiple depots and two types of vehicles (dedicated and occasional). A delivery task is executed by either a dedicated vehicle or an occasional vehicle. The dedicated vehicles depart from and return to the platform's depots; the occasional vehicles depart from their original location and pick up goods from depots or external pickup locations, fulfill the delivery tasks, and finish their route at the final delivery location. We propose mixed integer programming models and column generation-based solution methods to solve the problem. A computational study is conducted based on a series of randomly generated instances and real-world instances involving 15 depots, 120 internal customers, 15 external delivery tasks, and 38 dedicated and occasional vehicles. The results obtained demonstrate the efficiency of the column generation-based solution methods. Moreover, the effectiveness of the proposed models is validated by a significant cost saving in comparison to intuitive decision rules. A sensitivity analysis is also conducted to derive a number of managerial implications.

Effects of Cowl-Induced Expansion on the Wave Complex Induced by Oblique Detonation Wave Reflection

Oblique detonation wave (ODW) reflection on the upper wall leads to a sophisticated wave complex, whose stability is critical to the application of oblique detonation engines. The unstable wave complex characterized with a continuous moving Mach stem has been observed, but the corresponding re-stability adjusting method is still unclear so far. In this study, the cowl-induced expansion wave based on the model with an upper-side expansion wall is introduced, and the ODW dynamics have been analyzed using the reactive Euler equations with a two-step induction–reaction kinetic model. With the addition of a cowl-induced expansion wave, the re-stabilized Mach stem has been distinguished. This re-stability is determined by the weakened secondary reflection wave of lower wall, while the final location of Mach stem is not sensitive to the position of the expansion corner. The re-stabilized ODW structure is also basically irrelevant to the expansion angle, while it may shift to unstable due to the merging of subsonic zones. Transient phenomena for the unstable state have been also discussed, clarifying fine wave structures further.

Relocating microseismicity from downhole monitoring of the Decatur CCS site using a modified double-difference algorithm

SUMMARYThe injection of CO2 at the Decatur carbon capture and storage site has generated significant microseismic activity, which occurs in distinct spatial clusters up to approximately 2.2 km from the primary injection well. Accurate and precise event locations are vital for the characterization of the microseismicity to help understand the reservoir response to the CO2 injection, whilst enabling the identification of minor faults and fractures below the resolution of conventional active seismic imaging. However, microseismic monitoring of fluid injection sites, such as Decatur, is often performed using a network of borehole sensors often from a single well. While these downhole sensors have excellent detection capabilities, their poor azimuthal coverage limits the ability to precisely determine event locations. We have developed a modified double-difference relocation algorithm suitable for both 1-D and 3-D velocity models, and which incorporates differential back azimuth observations to allow the benefits of the original double-difference algorithm to be applicable to a downhole microseismic monitoring setting. Applying the modified double-difference algorithm to the microseismicity at Decatur, we have successfully relocated 4293 events. The relocation included over 59 million observations for 757 285 event pairs, split across seven geographic regions. Despite the majority of observations being recorded in only two boreholes, with an almost identical azimuthal coverage, the results have shown to be reliable with significantly reduced residuals and low uncertainties associated with the final locations. We have analysed the residuals in terms of their association with each geographic region, data type, station and individual events, to fully appreciate their influence in the inversion and the fit of the data to the final set of event locations. For each region, the relocated seismicity has become less diffuse with improved clustering, and with newly visible linear features often orientated in a NE–SW direction. These results show the potential improvements that can be made to microseismic event locations recorded by a borehole network with a limited and variable azimuthal distribution.

The CATP-8/P5A-type ATPase functions in multiple pathways during neuronal patterning.

The assembly of neuronal circuits involves the migrations of neurons from their place of birth to their final location in the nervous system, as well as the coordinated growth and patterning of axons and dendrites. In screens for genes required for patterning of the nervous system, we identified the catp-8/P5A-ATPase as an important regulator of neural patterning. P5A-ATPases are part of the P-type ATPases, a family of proteins known to serve a conserved function as transporters of ions, lipids and polyamines in unicellular eukaryotes, plants, and humans. While the function of many P-type ATPases is relatively well understood, the function of P5A-ATPases in metazoans remained elusive. We show here, that the Caenorhabditis elegans ortholog catp-8/P5A-ATPase is required for defined aspects of nervous system development. Specifically, the catp-8/P5A-ATPase serves functions in shaping the elaborately sculpted dendritic trees of somatosensory PVD neurons. Moreover, catp-8/P5A-ATPase is required for axonal guidance and repulsion at the midline, as well as embryonic and postembryonic neuronal migrations. Interestingly, not all axons at the midline require catp-8/P5A-ATPase, although the axons run in the same fascicles and navigate the same space. Similarly, not all neuronal migrations require catp-8/P5A-ATPase. A CATP-8/P5A-ATPase reporter is localized to the ER in most, if not all, tissues and catp-8/P5A-ATPase can function both cell-autonomously and non-autonomously to regulate neuronal development. Genetic analyses establish that catp-8/P5A-ATPase can function in multiple pathways, including the Menorin pathway, previously shown to control dendritic patterning in PVD, and Wnt signaling, which functions to control neuronal migrations. Lastly, we show that catp-8/P5A-ATPase is required for localizing select transmembrane proteins necessary for dendrite morphogenesis. Collectively, our studies suggest that catp-8/P5A-ATPase serves diverse, yet specific, roles in different genetic pathways and may be involved in the regulation or localization of transmembrane and secreted proteins to specific subcellular compartments.

Ten years of time-lapse seismic on Atlantis Field

In 2019, the fourth ocean-bottom-node survey was acquired over Atlantis Field. This survey was quickly processed to provide useful time-lapse (4D) observations two months after the end of the acquisition. The time-lapse observations were immediately valuable in placing wells, refining final drilling target locations, updating well prioritization, and sequencing production and water-injection wells. These data are indispensable pieces of information that bring geophysicists and reservoir engineers together and focus the conversation on key remaining uncertainties such as fault transmissibilities and drainage areas. Time-lapse observations can confirm the key conceptional models already in place but are even more valuable when they highlight alternative models that have not yet been considered. The lessons learned from the acquisition, processing, analysis, interpretation, and integration of the data are shared. Some of these lessons are reiterations of previous work, but several new lessons originated from the latest 2019 acquisition. This was the first survey in which independent simultaneous sources were successfully deployed to collect a time-lapse survey. This resulted in a much faster and less expensive acquisition. In addition, full-waveform inversion was used as the main tool to update the velocity model, enabling a much faster turnaround in processing. The fast turnaround enabled incorporation of the latest acquisition to better constrain the velocity model update. The updated velocity model was used for the final time-lapse migration. In the integration part, the 4D-assisted history-match workflow was engaged to update the reservoir model history match. All of the upgrades led to an overall faster, less expensive, and better way to incorporate the acquired data in the final business decisions.

Pre-clinical estimation of the intraocular lens A-constant, and its relationship to power, shape factor, and asphericity.

Calculating the intraocular lens power for a particular patient requires an empirical "lens constant" to estimate the final axial location after surgery. This is normally calculated from clinical results for each new lens style, but it can also be estimated without clinical data by comparing a new style to an existing style. The lenses are axially positioned in a model eye at comparable locations, and image distances are used to estimate the change in lens constant. The A-constant used by the SRK/T calculation method is evaluated here, but this can be easily converted for other calculations using an average eye. Raytrace calculations demonstrate the method, and also illustrate the effects that refractive index, shape factor, and asphericity have on the refractive error. Actual lens measurements at 35°C in saline are preferable if details of the reference lens are uncertain.

A CFD study of the transport and fate of airborne droplets in a ventilated office: The role of droplet-droplet interactions.

Previous studies reported that specially designed ventilation systems provide good air quality and safe environment by removing airborne droplets that contain viruses expelled by infected people. These water droplets can be stable in the environment and remain suspended in air for prolonged periods. Encounters between droplets may occur and droplet interactions should be considered. However, the previous studies focused on other physical phenomena (air flow, drag force, evaporation) for droplet transport and neglected droplet interactions. In this work, we used computational fluid dynamics (CFD) to simulate the transport and fate of airborne droplets expelled by an asymptomatic person and considered droplet interactions. Droplet drag with turbulence for prediction of transport and fate of droplets indicated that the turbulence increased the transport of 1 µm droplets, whereas it decreased the transport of 50 µm droplets. In contrast to only considering drag and turbulence, consideration of droplet interactions tended to increase both the transport and fate. Although the length scale of the office is much larger than the droplet sizes, the droplet interactions, which occurred at the initial stages of release when droplet separation distances were shorter, had a significant effect in droplet fate by considerably manipulating the final locations on surfaces where droplets adhered. Therefore, it is proposed that when an exact prediction of transport and fate is required, especially for high droplet concentrations, the effects of droplet interactions should not be ignored.Electronic Supplementary MaterialSupplementary material is available in the online version of this article at 10.1007/s11783-021-1465-8 and is accessible for authorized users.