Slowdown In Speed Research Articles

Translation speed slowdown and poleward migration of western North Pacific tropical cyclones

Detecting and interpreting long-term changes in typhoon translation speed in observations remains challenging, contrasting with increased confidence in the poleward migration of typhoons. Here, I show a significant relationship between the basin-wide translation speed and the latitudinal position of tropical cyclones in the western North Pacific over 1980–2023. First, because tropical cyclones move faster at higher latitudes, the significant poleward migration (80 km/decade) increases the yearly basin-wide translation speed by 5% over the period. This effect reduces the detectability of a slowing trend. Second, the basin-wide translation speed solely contributed by regional translation speed has slowed by 18%, mostly in the late stage of the cyclone lifecycle. The translation speed slowdown and the poleward migration are likely caused by the same climate drivers through the interconnected large-scale atmospheric circulation between the tropics and subtropics. My findings suggest exacerbated tropical cyclone-related risk in the subtropical regions in a changing climate.

Statistical and Dynamical Characteristics of Extreme Wave Crests Assessed with Field Measurements from the North Sea

Abstract Wave crests of unexpected height and steepness pose a danger to activities at sea, and long-term field measurements provide important clues for understanding the environmental conditions that are conducive to their generation and behavior. We present a novel dataset of high-frequency laser altimeter measurements of the sea surface elevation gathered over a period of 18 years from 2003 to 2020 on an offshore platform in the central North Sea. Our analysis of crest height distributions in the dataset shows that mature, high sea states with high spectral steepness and narrow directional spreading exhibit crest height statistics that significantly deviate from standard second-order models. Conversely, crest heights in developing sea states with similarly high steepness but wide directional spread correspond well to second-order theory adjusted for broad frequency bandwidth. The long-term point time series measurements are complemented with space–time stereo video observations from the same location, collected during five separate storm events during the 2019/20 winter season. An examination of the crest dynamics of the space–time extreme wave crests in the stereo video dataset reveals that the crest speeds exhibit a slowdown localized around the moment of maximum crest elevation, in line with prevailing theory on nonlinear wave group dynamics. Extending on previously published observations focused on breaking crests, our results are consistent for both breaking and nonbreaking extreme crests. We show that wave crest steepness estimated from time series using the linear dispersion relation may overestimate the geometrically measured crest steepness by up to 25% if the crest speed slowdown is not taken into account. Significance Statement Better understanding of the statistics and dynamical behavior of extreme ocean surface wave crests is crucial for improving the safety of various operations at sea. Our study provides new, long-term field evidence of the combined effects of wave field steepness and directionality on the statistical distributions of crest heights in storm conditions. Moreover, we show that the dynamical characteristics of extreme wave crests are well described by recently identified nonlinear wave group dynamics. This finding has implications, for example, for wave force calculations and the treatment of wave breaking in numerical wave models.

Microstructural Gray Matter Integrity Deteriorates After an Ischemic Stroke and Is Associated with Processing Speed.

Microstructural changes after an ischemic stroke (IS) have mainly been described in white matter. Data evaluating microstructural changes in gray matter (GM) remain scarce. The aim of the present study was to evaluate the integrity of GM on longitudinal data using mean diffusivity (MD), and its influence on post-IS cognitive performances. A prospective study was conducted, including supra-tentorial IS patients without pre-stroke disability. A cognitive assessment was performed at baseline and 1year, including a Montreal Cognitive Assessment, an Isaacs set test, and a Zazzo cancelation task (ZCT): completion time and number of errors. A 3-T brain MRI was performed at the same two time-points, including diffusion tensor imaging for the assessment of GM MD. GM volume was also computed, and changes in GM volume and GM MD were evaluated, followed by the assessment of the relationship between these structural changes and changes in cognitive performances. One hundred and four patients were included (age 68.5 ± 21.5, 38.5% female). While no GM volume loss was observed, GM MD increased between baseline and 1year. The increase of GM MD in left fronto-temporal regions (dorsolateral prefrontal cortex, superior and medial temporal gyrus, p < 0.05, Threshold-Free Cluster Enhancement, 5000 permutations) was associated with an increase time to complete ZCT, regardless of demographic confounders, IS volume and location, GM, and white matter hyperintensity volume. GM integrity deterioration was thus associated with processing speed slowdown, and appears to be a biomarker of cognitive frailty. This broadens the knowledge of post-IS cognitive impairment mechanisms.

Using Swimming Speed as an Indicator of Malformation: A Practical Approach for Identification and Removal of Juvenile Seabass (Dicentrarchus labrax L., 1758) with Skeletal Deformity

Skeletal abnormalities in farmed fish are one of the main problems that negatively affect the production enterprises in terms of economic, biological and animal health. Fish with skeletal deformities in hatcheries are considered as non-economic individuals and are therefore detected and removed manually from the production tanks, which is a time consuming and laborious work for the facilities. Since the formation of abnormalities in the skeletal structure of the fish during the early growth period cause reduced swimming ability or speed that prevent fish to compete during feeding. Further, since deformed fish has no market value, even the share of a small amount of feed among deformed fish will reduce the feed conversion for the market targeted individuals within the culture tank that in terms may increase the production cost per fish. Therefore, in culture conditions it is important to remove the deformed fish from the tank environment by quickly determining those fellows at the early stage of growth. The present study evaluates the effects of water velocity on swimming behavior of juvenile seabass (Dicentrarchus labrax) and provides a solution for a rapid identification -and mechanical removal of deformed fish from the culture environment by using swimming speed slowdown -and behavioral differences as an indicator of deformation.

The development of healthcare mobile robot for helping medical personnel in dealing with COVID-19 patients

&lt;span lang="EN-US"&gt;Coronavirus disease (COVID-19) pandemic has succeeded in shaking the whole world. This situation requires medical personnel to work extraordinarily to treat COVID-19 patients with very high risk of transmission. For this reason, this study aimed to helping medical personnel handle COVID-19 patients through robotic technology. The development method in this study is proposed as a way to develop robots to serve patients in isolation rooms controlled at a distance away from other rooms. From technical testing, the movement of the robot with a load of 12.59 kg only experienced a speed slowdown which was not too significant, namely at 0.43s with an average percentage of slowdown of 8.96%. The accuracy of the proximity sensor testing is close to perfect with an accuracy percentage of 99.62%. The robot control distance was monitored and running well. Also, the increase in motor temperature is not too large, supported by measurement results of 32.13%. From non-technical testing, based on the test results of the feasibility test of all respondents with 25 indicators reached a feasibility level of 91.46%. In other words, healthcare mobile robots developed for helping medical personnel in dealing with COVID-19 patients are very feasible to be applied in hospitals.&lt;/span&gt;

Design and Test of Double-Cutterbar Structure on Wide Header for Main Crop Rice Harvesting

Harvesting main crop rice with a wide header at a required height can increase its ratoon crop yield by decreasing the stubble rolling rate. However, an increased harvest width brings in more input material in a specific time, causing the size enlargement or working speed slowdown of harvesters. To solve this issue, a double-cutterbar structure was proposed. To provide a design baseline for the structure, the cutterbar configuration methods based on rice plant deformation were developed and verified, stalk shearing tests were conducted, and a double-cutterbar prototype was fabricated and tested. The results indicated that the methods developed for the configuration of the upper and lower cutterbars could considerably implement their functions of lowering the straw-grain ratio and keeping stubble height as required. The shearing tests indicated that the bevel angle significantly influenced the total shearing energy on each cutting point in Internode 2 and 3 (p &lt; 0.05) due to the increased stalk cross sectional area. The stubble rolling rate, panicle straw length and stubble height of the developed harvester were 26.9 %, 125 ± 80 mm and 332 ± 22 mm, respectively, which could meet the requirements of main crop rice harvesting. The outcomes indicated the functionality and practicability of the double-cutterbar structure developed based on rice plant deformation and shearing properties.

Risk Reduction Assessment for Installing RCP Shutdown Seal

As one of the lessons learned from the Fukushima Daiichi accident, long-term station blackout (SBO) and subsequent loss of ultimate heat sinks have prompted discussion on this topic in the nuclear industry. The SBO sequences for a Westinghouse three-loop pressurized water reactor (PWR) have been under investigation for a long period. To cope with the long-term SBO issue, many nuclear power plants have decided to replace the reactor coolant pump (RCP) seal by the new passive thermal shutdown seal (PSDS). The PSDS is a fail-safe protection device that will significantly reduce leakage from the RCP seal in case of loss of cooling. This makes a seal loss-of-coolant accident no longer a risk-significant event, and the relevant probabilistic risk assessment (PRA) models need to be modified to reflect the associated plant change. The PRA model of a Westinghouse PWR plant has been reviewed to reflect this more strongly; i.e. loss of component cooling water (CCW), loss of 4-kV vital alternating-current power, and loss of off-site power are revised for their sequences. According to the Westinghouse analysis, the PSDS temperature must be maintained below 104°C, and the operators have to control the RCP speed. In this paper, those factors are incorporated into the event tree structure revision of the loss of CCW event (TC) and loss of power either off-site (TP) or vital power A train (TAPB). In another case, LOOP initiating events need to consider the time span that the blackout conditions would affect the RCP seal integrity. Because the RCP will be tripped automatically, the limitation associated with RCP speed will not be applicable. Compared with the TC, TP, and TAPB event tree base cases, RCP speed slowdown or available time span is introduced into the PSDS model. The relevant part in the PRA model is subject to review and modification. The risk reduction associated with the PSDS is found to be significant.

Slowdown of Typhoon Translation Speeds in Mid-latitudes in September Influenced by the Pacific Decadal Oscillation and Global Warming

Global warming already affects weather and climate worldwide; accordingly, various studies have been conducted to understand the effects of climate change on tropical cyclones. The translation speed of a tropical cyclone is a particularly important feature, as a slower translation speed lengthens the duration of a cyclone's impact. Here, on the basis of observational data, we report that tropical cyclone translation speeds in the middle latitudes of the western North Pacific basin have significantly decreased during September over the last 40 years. Historical model simulations with and without observational global warming trends reveal two main factors responsible for the translation speed slowdown: natural decadal climate variabilities (such as the Pacific Decadal Oscillation) and global warming. Both factors produce an anticyclonic anomaly in the westerly jet over western Japan; this anomaly relaxes the latitudinal geopotential height gradient, weakening the environmental synoptic winds by which tropical cyclones are steered. Furthermore, model simulations for a future warmer climate show that global warming further reduces the steering flows, leading to more slowly-moving tropical cyclones in autumn in the future.

Sensing Margin Enhancement Technique Utilizing Boosted Reference Voltage for Low-Voltage and High-Density DRAM

In the case of dynamic random access memory (DRAM) using a voltage latched sense amplifier, various offset voltage cancellation techniques have been studied to secure the sensing margin. However, as coupling noise and process variations increase with technology scaling, it is impossible to obtain a sufficient sensing margin only by using an offset voltage cancellation technique. In addition, offset voltage cancellation techniques have several problems, such as area overhead and sensing speed slowdown at a low supply voltage. In this paper, we propose a sense amplifier that maximizes the sensing margin by boosting the reference bitline voltage during the charge sharing operation and adopting the offset voltage cancellation technique. The sensing voltage difference of the proposed sense amplifier increases by 50% or more than that of the conventional offset cancellation (OC) sense amplifier at the low supply voltage of 0.9 V, which can improve not only the sensing speed by 2 ns but also the sensing yield by 11.8%. In addition, the proposed sense amplifier achieves a stable sensing yield with a larger cell array height and thus can compensate the area overhead of 44% caused by the OC technique by decreasing the overall cell array height.

Characteristics of boreal winter cluster extreme events of low temperature during recent 35 years and its future projection under different RCP emission scenarios

Cluster extreme event (CEE), which is characterized by large affected area and long duration of extreme weather, has been arousing the worldwide serious concerns due to its severe impact on society. The winter cluster extreme events of low temperature (LT_CEEs) in the northern hemisphere from 1979 to 2013 are identified with a simplified objective method based on ERA-Interim and JRA-25 daily minimum surface air temperature. The probability density function (PDF) distributions of most indices in the winter LT_CEEs derived from the two datasets are well consistent with each other, especially in the occurrence frequency, duration, and affected area. As expected, the downward trend of all indices in recent 35 years under global warming is congruously revealed from both reanalysis. Nevertheless, the various indices of the winter LT_CEEs after 1998 are generally stable accompanied with slight upward trend, which might be closely related to the speed slowdown of global warming but require further investigation. Similar analysis was carried out with the simulated results of BCC_CSM1.1 model under four scenarios of RCP2.6, RCP4.5, RCP6.0, and RCP8.5. The occurrence frequency of the winter LT_CEEs under RCP2.6 remains stable after 2050, but significantly decreases under RCP4.5 and RCP6.0, and disappears under RCP8.5 scenario. Overall, the descent rate of the winter LT_CEEs accelerates with the emission rise.

Cross-Vendor and Cross-State Analysis of GPS Probe Data Latency

Crowd sourced GPS probe data have become a major source of real-time traffic information applications. In addition to traditional traveler advisory systems such as dynamic message signs (DMS) and 511 systems, probe data are being used for automatic incident detection, integrated corridor management (ICM), end of queue warning systems, and mobility-related smartphone applications. Several private sector vendors offer minute by minute network-wide travel time and speed probe data. The quality of such data in terms of deviation of the reported travel time and speeds from ground-truth has been extensively studied in recent years, and as a result concerns over the accuracy of probe data have mostly faded away. However, the latency of probe data—defined as the lag between the time at which disturbance in traffic speed is reported in the outsourced data feed, and the time at which the traffic is perturbed—has become a subject of interest. The extent of latency of probe data for real-time applications is critical, so it is important to have a good understanding of the amount of latency and its influencing factors. This paper uses high-quality independent Bluetooth/Wi-Fi re-identification data collected on multiple freeway segments in three different states, to measure the latency of the vehicle probe data provided by three major vendors. The statistical distribution of the latency and its sensitivity to speed slowdown and recovery periods are discussed.

Recent recovery of surface wind speed in northwest China

Previous studies have reported that much of the surface wind speed (SWS) over the mid‐latitudes of the northern hemisphere has declined. However, very few studies have investigated the relatively recent phenomenon of wind recovery. Based on 68 wind data series, this paper examines changes in wind speed in northwest China between 1969 and 2015. In 1992, following a decade of sharply decreasing at a rate of 0.036 m s−1 a−1 (p &lt; .05), the SWS began to significant increase at a rate of 0.004 m s−1 a−1. The specific reasons for this increase are as follows: (a) The decrease in SWS during the pre‐1992 slowdown period is the result of declining wind speeds in spring and summer, whereas increases in wind speed during the post‐1992 recovery period are caused by increased wind in winter. (b) The number of days featuring strongly varying wind speeds has changed. Specifically, the number of days above 2 m s−1 all show a significant decreasing trend from 1969 to 1992, whereas the number of days of 1–3 m s−1 shows a significant upward trend from 1993 to 2015. (c) Stations located between 1,000 and 1,500 m.a.s.l. (meter above sea level) are more sensitive to climate change than those at other altitudes, which shows the biggest decline (increase) trend during wind speed slowdown (recovery) period. These stations could potentially act as climatic indicators to predict future wind speed changes. SWS in northwest China have been affected by changes both in large‐scale atmospheric circulation and in regional warming. Surface pressure gradient variations between high‐ and low‐latitude regions may be important contributors to wind speed changes under asymmetric warming. However, urbanization is only moderately responsible for trend changes in SWS.

Compensatory rearrangements in the cortical control of movement in elderly patients with chronic cerebral ischemia

Dynamic praxis was tested in three groups of elderly subjects, including control respondents with mild cognitive impairment, respondents with moderate cognitive impairment, and patients with vascular dementia. The groups were compared with one another. This comparison was methodologically based on Luria’s theory of systemic and dynamic localization of higher mental functions. The elderly subjects manifested disorders in praxis. Locomotor actions become slow in elderly subjects with mild cognitive impairment. These subjects compensated for difficulties in mastering a dynamic program by verbalizing this program and delaying the orientation phase of the action. Respondents with moderate cognitive impairment and clear manifestations of cerebrovascular pathology had stereotypies in the motor sphere and a speed slowdown in motor actions, which were more expressed in patients with vascular dementia. These subjects could only in part compensate for these disorders. But some of them could master a motor program after a cue or education.

Fast computer generated hologram calculation with a mini look-up table incorporated with radial symmetric interpolation.

The amount of heavy computation in Computer Generated Hologram (CGH) can be significantly reduced by pre-computing look-up tables. However, the huge memory usage of look-up tables is a major challenge. To address this problem, the Look-up tables can be efficiently compressed by methods such as radial symmetric interpolation. In this paper, we notice that there is still data redundancy in the look-up table of radial symmetric interpolation method and the table size can be further compressed to 5%-10% or even less of original, by our proposed mini look-up table approach based on Principal Component Analysis (PCA). The compressed look-up table in our scheme only occupies a memory size of around 200-300 KB or even less. Moreover, the proposed scheme will introduce almost no extra cost of computation speed slowdown and reconstructed image quality degradation, compared to conventional method.

Tribo-films control in adaptive TiAlCrSiYN/TiAlCrN multilayer PVD coating by accelerating the initial machining conditions

Abstract A nano- multilayer TiAlCrSiYN/TiAlCrN was deposited by Physical Vapor Deposition (PVD) on cemented carbide turning inserts. Assessment of the performance of the coated inserts in machining of DA718 Inconel was made at various cutting speeds during the initial, running-in stage of wear. Three types of machining conditions were used: i. Regular cutting speed (40 m/min) used in industrial practice; ii. Higher cutting speed of 60 m/min, and iii. Accelerated (higher speed followed by regular cutting speed). Comprehensive characterization of the tribofilms formed on the surface of the worn cutting tools was made using Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy analyses. SEM/EDS elemental mapping was used for evaluation of the wear patterns. It was shown that an initial short-term increase in the cutting speed during the running-in stage (condition iii) noticeably improves tool life. This is because during initial cutting at high speed, enhanced formation of protective/lubricious tribo-ceramic films on the friction surface takes place, with the subsequent slowdown in speed preventing total wearing out of the beneficial tribofilms. In this way, the tribofilm formation process can be enhanced at the start of the process and the benefits of these films can be realized over the life of the tool.

Antifouling Compounds Endangering Marine Invertebrates Reproduction

Reproduction and embryo development of marine animals occur in the sea water and are processes very sensitive to substances present in the environment that come from industrial and agricultural activities. These compounds are collectively known as xenobiotics due to their extraenvironmental origin. Among xenobiotics present in the sea water, a relevant role is played by the anti-fouling compounds. These are used to prevent settlement and growth of organisms on submerged structures of vessels and ships that otherwise should create serious problems of speed slow down.

Design and Analysis of an MPPT Technique for Small-Scale Wind Energy Conversion Systems

This paper proposes a maximum power point tracking (MPPT) algorithm for small-scale wind energy conversion systems. The proposed algorithm uses the dc current as the perturbing variable. The algorithm detects sudden wind speed changes indirectly through the dc-link voltage slope. The voltage slope is also used to enhance the tracking speed of the algorithm and to prevent the generator from stalling under rapid wind speed slowdown conditions. The proposed method uses two modes of operation: A perturb and observe (P&O) mode with adaptive step size under slow wind speed fluctuation conditions, and a prediction mode employed under fast wind speed change conditions. The dc-link capacitor voltage slope reflects the acceleration information of the generator, which is then used to predict the next step size and direction of the current command. The proposed algorithm shows enhanced stability and fast tracking capability under both high and low rate of change wind speed conditions and is verified using a 1.5 kW prototype hardware setup.

Finite Element Computation of KPP Front Speeds in Cellular and Cat’s Eye Flows

We compute the front speeds of the Kolmogorov-Petrovsky-Piskunov (KPP) reactive fronts in two prototypes of periodic incompressible flows (the cellular flows and the cat's eye flows). The computation is based on adaptive streamline diffusion methods for the advection-diffusion type principal eigenvalue problem associated with the KPP front speeds. In the large amplitude regime, internal layers form in eigenfunctions. Besides recovering known speed growth law for the cellular flow, we found larger growth rates of front speeds in cat's eye flows due to the presence of open channels, and the front speed slowdown due to either zero Neumann boundary condition at domain boundaries or frequency increase of cat's eye flows.

Optimal construction of a fast and accurate polarisable water potential based on multipole moments trained by machine learning

To model liquid water correctly and to reproduce its structural, dynamic and thermodynamic properties warrants models that account accurately for electronic polarisation. We have previously demonstrated that polarisation can be represented by fluctuating multipole moments (derived by quantum chemical topology) predicted by multilayer perceptrons (MLPs) in response to the local structure of the cluster. Here we further develop this methodology of modeling polarisation enabling control of the balance between accuracy, in terms of errors in Coulomb energy and computing time. First, the predictive ability and speed of two additional machine learning methods, radial basis function neural networks (RBFNN) and Kriging, are assessed with respect to our previous MLP based polarisable water models, for water dimer, trimer, tetramer, pentamer and hexamer clusters. Compared to MLPs, we find that RBFNNs achieve a 14-26% decrease in median Coulomb energy error, with a factor 2.5-3 slowdown in speed, whilst Kriging achieves a 40-67% decrease in median energy error with a 6.5-8.5 factor slowdown in speed. Then, these compromises between accuracy and speed are improved upon through a simple multi-objective optimisation to identify Pareto-optimal combinations. Compared to the Kriging results, combinations are found that are no less accurate (at the 90th energy error percentile), yet are 58% faster for the dimer, and 26% faster for the pentamer.

Reaction-Diffusion Front Speeds in Spatially-Temporally Periodic Shear Flows

We study the asymptotics of two space dimensional reaction-diffusion front speeds through mean zero space-time periodic shears using both analytical and numerical methods. The analysis hinges on traveling fronts and their estimates based on qualitative properties such as monotonicity and a priori integral inequalities. The computation uses an explicit second order upwind finite difference method to provide more quantitative information. At small shear amplitudes, front speeds are enhanced by an amount proportional to shear amplitude squared. The proportionality constant has a closed form expression. It decreases with increasing shear temporal frequency and is independent of the form of the known reaction nonlinearities. At large shear amplitudes and for all reaction nonlinearities, the enhanced speeds grow proportional to shear amplitude and are again decreasing with increasing shear temporal frequencies. The results extend previous ones in the literature on front speeds through spatially periodic shears and show front speed slowdown due to shear direction switching in time.