Frontal Structure Research Articles

ДИАГНОСТИКА ФРОНТАЛЬНЫХ КОНСТРУКЦИЙ НА ОСНОВЕ МЕХАТРОННЫХ СИСТЕМ

The article considers the use of a mechatronic system for monitoring and diagnostics of frontal structures of buildings. Structural and functional diagram of the mechatronic control and diagnostics system of the frontal structure is presented. Calculation of frontal structure element based on finite element method is considered. The results of the theoretical calculation of the thermal flow of the frontal structure are presented. Recommendations are given on the use of the finite element method for calculating frontal structures according to various parameters.

Automotive frontal body structure optimisation in the Upper Legform to Bonnet Leading Edge test with the aim of reducing the pedestrian injuries

Automotive frontal body structure design and optimisation are absolutely essential towards reducing the risk of pedestrian injuries in road accidents. In this paper, a two-step optimisation process in combination with the finite element method (FEM) is utilized to enhance pedestrian protection for a class-B passenger car. In this way, the finite element (FE) model of the Upper Legform Impactor has been developed and verified according to the European Commission (EC) Regulation No 631/2009. The Upper Legform to Bonnet Leading Edge test has been numerically simulated using LS-DYNA software. Material and geometry of the frontal body structure components are considered as the design variables and optimum design points are identified using the Taguchi method through a two-step framework. The Analysis of variance (ANOVA) is also used to determine the percentage effect of each controllable factors on the desired output. The obtained results revealed that in the optimum design point in comparison with the base vehicle, more than 45% improvement in the pedestrian protection criterion is observed, while selected components experienced mass reduction about 9%.

Memory complaints are associated with impaired working memory and reduced frontal cortical thickness in mid‐life surgically menopausal women

AbstractBackgroundAlzheimer’s disease (AD)‐related brain pathology is observed in participants within the normal ranges of cognitive assessments (Delacourte et al., 1999). Consequently, there is increased interest in subjective cognitive decline (SCD), a self‐experienced decline in cognition, as an early risk factor (Jessen et al., 2014). SCD is associated with earlier conversion to mild cognitive impairment (MCI) and AD (Jessen et al., 2010; Reisberg et al., 2010), poorer performance on cognitive tasks, and cortical thinning in AD‐related regions (Schultz et al., 2015; Sánchez‐Benavides et al., 2018). Women with surgical menopause prior to age 50 have an increased risk of AD (Rocca et al., 2007). Women with bilateral salpingo‐oophorectomy (BSO) without estradiol (E2) therapy in mid‐life show decreases in WM performance and volumetric declines in the frontal cortex and hippocampus compared to controls (Almey et al., 2018; Gervais et al., 2018).MethodThe current study evaluated the association of memory complaints with WM performance and frontal cortical thickness in a mid‐life cohort of at‐risk women with BSO. Participants with memory complaints (n = 42) and without (n = 30) completed demographics and neuropsychological tasks to assess WM. A subset of these participants with memory complaints (n = 11) and without (n = 14) were scanned using a 3T Siemens scanner, and cortical thickness was obtained from T1‐weighted scans using CIVET 2.1.1 (Ad‐Dab’bagh et al., 2005). Analyses were performed using R 1.1.4 (R Core Team, 2018).ResultOur analyses revealed participants with memory complaints performed significantly worse on WM tasks than those without. Furthermore, we found participants with memory complaints had significantly thinner cortices within the left ventrolateral prefrontal cortex (vlPFC), a region associated with WM (Badre & Wagner, 2007).ConclusionOur preliminary results demonstrate memory complaints are associated with impaired WM performance and frontal cortical thinning in women with BSO. The results suggest that women with surgical menopause and memory complaints show differences associated with SCD in WM function and frontal cortical structure at an early age (Wang et al., 2004). Ongoing research is evaluating effects of memory complaints on cognition and brain structure within spontaneously menopausal women in the COMPASS‐ND database (CCNA, 2020).

Theoretical and experimental possibilities to set up some sensors systems involved in active safety process

The safety systems present in the construction of modern motor vehicles fully benefit from all development research efforts in the field of autonomous motor vehicles. In this paper, we have analyzed, theoretically and experimentally, for three distinct types of passenger cars, the following active safety systems: 1. Autonomous Emergency Braking system, designed as an automatic braking process of the vehicle, in response to the detection of a probable collision, to reduce the speed of the vehicle; 2. Forward Collision Warning, implemented as an audiovisual warning that is present on board a motor vehicle, to alert the driver; 3. Dynamic Brake support, which further amplifies the braking force to detect the imminent collision to achieve a higher deceleration than in the situation of a normal speed reduction. As a following were study three states such as: Car-to-Car Rear Stationary as a possible collision in which a vehicle travels forwards towards another stationary vehicle and the front structure of the vehicle strikes the rear structure of the other, Car-to-Car Rear Moving as a probable collision in which a vehicle travels forwards towards another vehicle that is travelling at constant speed and the front structure of the vehicle strikes the rear structure of the other and possible collisions named Car-to-Car Rear Braking in which a vehicle travels forwards towards another vehicle that is travelling at constant speed and then decelerates, and the frontal structure of the vehicle strikes the rear structure of the other. The three situations have been examined, experimentally and theoretic, in order to obtain important information about the configurations of sensor systems that compose safety systems. The work allowed to obtain configuration information, experimentally confirmed, with an impact on the improvement of future autonomous vehicles system.

High-Resolution Sea Surface Temperatures Derived from Landsat 8: A Study of Submesoscale Frontal Structures on the Pacific Shelf off the Hokkaido Coast, Japan

Coastal and offshore waters are generally separated by a barrier or “ocean front” on the continental shelf. A basic question arises as to what the representative spatial scale across the front may be. To answer this question, we simply corrected skin sea surface temperatures (SSTs) estimated from Landsat 8 imagery with a resolution of 100 m using skin SSTs estimated from geostationary meteorological satellite Himawari 8 with a resolution of 2 km. We analyzed snapshot images of skin SSTs on 13 October 2016, when we performed a simultaneous ship survey. We focused in particular on submesoscale thermal fronts on the Pacific shelf off the southeastern coast of Hokkaido, Japan. The overall spatial distribution of skin SSTs was consistent between Landsat 8 and Himawari 8; however, the spatial distribution of horizontal gradients of skin SSTs differed greatly between the two datasets. Some parts of strong fronts on the order of 1 °C km−1 were underestimated with Himawari 8, mainly because of low resolution, whereas weak fronts on the order of 0.1 °C km−1 were obscured in the Landsat 8 imagery because the signal-to-noise ratios were low. The widths of the strong fronts were estimated to be 114–461 m via Landsat 8 imagery and 539–1050 m via in situ ship survey. The difference was probably attributable to the difference in measurement depth of the SST, i.e., about 10-μm skin layer by satellite and a few dozen centimeters below the sea surface by the in situ survey. Our results indicated that an ocean model with a grid size of no more than ≤100–200 m is essential for realistic simulation of the frontal structure on the shelf.

Исследование и контроль циркуляции вод и структуры термохалинного поля в бухте Омега (Крым) в летне-осенний период 2019 года

Based on the data of two expeditions carried out in August and November 2019, the water circulation and the structure of the thermohaline field in Omega Bay are analyzed. A well-known idea on the predominantly wind nature of currents in the Sevastopol bays is confirmed. In August, under the influence of the north wind, a south-west oriented coastal wind current was observed in the Sevastopol seaside adjacent to the bay. Its speed in the upper and middle layers varied from 15 to 40 cm /s and from 10 to 15 cm /sec – at the bottom. The branch of this stream directed to the bay, interacting with the bottom rising located in its central part, contributed to the formation of an anticyclone water circulation cell. A similar dynamic situation in Omega Bay, but under conditions of a weaker and oppositely directed alongshore current, was also observed in November. It is shown that the anticyclone topographic eddy, found in the central part of Omega Bay is quasi stationary and has a topographic nature. In the structure of the thermohaline field, signs have been revealed that confirm the anticyclone nature of the local water circulation in Omega Bay, as well as the typical coastal current system generated by the wind surge, which was recorded in the August survey. In November, under the influence of convective mixing, the thermohaline field in the studied water area was more uniform. It is shown that, in contrast to relatively homogeneous waters of the most part of the bay water area, vertical stratification and frontal horizontal structure of the thermohaline field are characteristic of its kut region.

FEATURES OF THE INITIAL STAGE OF FORMATION OF FAST CORONAL MASS EJECTION ON FEBRUARY 25, 2014

We have analyzed the fast coronal mass ejection (CME) that occurred on February 25, 2014. The analysis is based on images taken in the 131, 211, 304, and 1700 Å UV channels of the SDO/AIA instrument and from observations obtained in the Hα line (6562.8 Å) with the telescopes of the Teide and Big Bear Observatories.
 The February 25, 2014 CME is associated with the ejection and subsequent explosive expansion of the magnetic flux rope, which appeared near the solar surface presumably due to the tether-cutting magnetic reconnection.
 The impulse of full pressure (thermal plus magnetic) resulting from such an “explosion” acts on the overlying coronal arcades, causing them to merge and form an accelerated moving frontal structure of the CME. This pressure impulse also generates a blast collisional shock wave ahead of the CME, whose velocity decreases rapidly with distance. At large distances R>7R₀ (R₀ is the solar radius) from the center of the Sun in front of the CME, a shock wave of another type is formed — a “piston” collisional shock wave whose velocity varies little with distance.
 At R≥15R₀, there is a transition from a collisional to a collisionless shock wave.

Особенности начальной стадии формирования быстрого коронального выброса массы 25 февраля 2014 г.

We have analyzed the fast coronal mass ejection (CME) that occurred on February 25, 2014. The analysis is based on images taken in the 131, 211, 304, and 1700 Å UV channels of the SDO/AIA instrument and from observations obtained in the Hα line (6562.8 Å) with the telescopes of the Teide and Big Bear Observatories.
 The February 25, 2014 CME is associated with the ejection and subsequent explosive expansion of the magnetic flux rope, which appeared near the solar surface presumably due to the tether-cutting magnetic reconnection.
 The impulse of full pressure (thermal plus magnetic) resulting from such an “explosion” acts on the overlying coronal arcades, causing them to merge and form an accelerated moving frontal structure of the CME. This pressure impulse also generates a blast collisional shock wave ahead of the CME, whose velocity decreases rapidly with distance. At large distances R>7R₀ (R₀ is the solar radius) from the center of the Sun in front of the CME, a shock wave of another type is formed — a “piston” collisional shock wave whose velocity varies little with distance.
 At R≥15R₀, there is a transition from a collisional to a collisionless shock wave.

Multisatellite-Based Feeding Habitat Suitability Modeling of Albacore Tuna in the Southern Atlantic Ocean

Decision strategies in fisheries management are often directed by the geographic distribution and habitat preferences of target species. This study used remote sensing data to identify the optimal feeding habitat of albacore tuna in the Southern Atlantic Ocean (SAO) using an empirical habitat suitability model applying longline fisheries data during 2009–2015. An arithmetic mean model with sea surface temperature (SST) and sea surface chlorophyll-a concentration (SSC) was determined to be suitable for defining the albacore habitat in the SAO. The optimal ranges of SST and SSC for the habitat were approximately 16.5 °C–19.5 °C and 0.11–0.33 mg/m3, respectively. The study revealed a considerable positive trend between the suitable habitat area and standardized catch per unit effort (r = 0.97; p < 0.05); due to the west-to-east and northward development of the suitable habitat, albacore schools moved to the northeast of the SAO, thus increasing catch probability in April to August in that region. Overall, the frontal structure of SST and SSC plays an essential role in the formation of potential albacore habitats in the SAO. Our findings could contribute to the establishment of regional ecosystem-based fisheries management in the SAO.

Study on the influence of coal dust concentration on flame propagation characteristics of gas explosion in semiclosed tube

ABSTRACT In order to deeply study the influence of the addition of coal dust on the propagation characteristics of gas explosion flame, in this paper, the frontal structure, front position, propagation velocity, propagation form, and duration of explosion flame produced by single-phase gas explosion and different concentration coal dust-gas coupling explosion are studied systematically. The results show that: when coal dust with different concentrations of 25~200 g/m3 is added, the time required for the complete development of the flame front of gas-coal dust coupling explosion is 50%~78.3% of that of single-phase gas explosion. In terms of propagation time, when coal dust with different concentrations of 25~200 g/m3 is added, compared with single-phase gas explosion, the time required for gas-coal dust coupling explosion flame to propagate from the ignition point to the outlet of the propagation tube will be shortened to varying degrees, with a range of 3.3%–28.6%. The addition of coal dust can greatly stimulate the development trend of explosion flame in the propagation tube. When coal dust with different concentrations of 25~200 g/m3 is added, the speed of explosion flame in the propagation tube will be increased in varying degrees, and the range of increase is 188% to 314.3%. After adding a certain amount of coal dust into the single-phase gas system, the overall duration of the explosion flame is greatly prolonged, and the flame oscillation phenomenon appears in the experimental tube.

Source region identification and geophysical effects of stealth coronal mass ejections

We use the example of two Stealth-type coronal mass ejections (stealth CMEs) registered by LASCO C2 on the quiescent Sun on 16 June 2010 and in the active region NOAA 11520 7 July 2012 to demonstrate that these mass ejections emerged in a lower-coronal area where an intense short-term radiation burst was registered in several extreme ultraviolet channels. It is established for the first time that the stealth CME emergence is accompanied by an eruption of small-scale loop-like structures, and the frontal structure (FS) formation is detected. The time dependences of the velocity of these FSs are discussed. The conclusion is made that having reached Earth orbit and impacting on the Earth magnetosphere, the stealth CMEs can lead to magnetic substorm generation.

Time‐Lapse Seismic Imaging of Oceanic Fronts and Transient Lenses Within South Atlantic Ocean

AbstractOceanic fronts play a pivotal role in controlling water mass transfer, although little is known about deep frontal structure on appropriate temporal and spatial scales. Here, we present a sequence of calibrated time‐lapse images from a three‐dimensional seismic survey that straddles the Brazil‐Malvinas Confluence—a significant feature of the meridional overturning circulation. Eight vertical transects reveal the evolution of a major front. It is manifest as a discrete planar surface that dips at less than 2° and is traceable to 1.5–2 km depth. Its shape and surface expression are consistent with sloping isopycnal surfaces of the calculated potential density field and with coeval sea surface temperature measurements, respectively. Within the top ∼1 km, where cold fresh water subducts beneath warm salty water, a series of tilted lenses are banked up against the sharply defined front. The largest of these structures is centered at 700 m depth and is cored by cold fresh water. Time‐lapse imagery demonstrates that this tilted lens grows and decays over 9 days. It has a maximum diameter of <34±0.13 km and a maximum height of <750±10 m. Beneath 1 km, where horizontal density gradients are negligible, numerous deforming lenses and filaments on length scales of 10–100 km are being swept toward the advecting front.

Rate of active shortening across the southern thrust front of the Greater Caucasus in western Georgia from kinematic modeling of folded river terraces above a listric thrust

Although the Greater Caucasus (GC) Mountains accommodate a significant fraction of orogen-perpendicular Arabia-Eurasia convergence at their longitude, the locations and slip rates of the active structures absorbing this shortening are poorly known. Here we report the first late Quaternary shortening rate for an active thrust in the GC determined from dating and reconstructing a deformed landform. In the Rioni basin along the southwestern flank of the GC, terraces along the Enguri River have been folded by the south-vergent Tsaishi anticline and record Quaternary shortening along the southernmost exposed frontal structure. Terrace surfaces are well preserved and together with underlying Mesozoic-to-Neogene strata clearly record folding. We use high-resolution topographic data from differential GPS surveys and bedding attitudes across the fold to construct a kinematic model that describes both the terrace deformation and finite shortening across the anticline recorded by the folded strata. We calculate that a deformed terrace records 106.1 +38.7/-36.4 m of slip since abandonment. Optically stimulated luminescence dating of quartz in a loess cap on this terrace indicates it was abandoned before 94.1 ± 12.8 ka, implying a geologic shortening rate of 1.09 +0.62/-0.43 mm/yr since ∼100 ka. This work confirms that the frontal structure of the Rioni fold-thrust belt is Quaternary-active, but has a rate that falls short of the regional geodetic shortening rate of 3-5 mm/yr. We infer that the missing late Quaternary shortening is accommodated by additional structures within the GC to the north. Folding of late Quaternary terraces and a possible coseismic scarp along the frontal structure of the GC together imply that structures in the western GC may be capable of coseismic rupture within and beneath the adjacent basin, in addition to blind ruptures within the main range such as the 1991 Racha earthquake. Thus, the GC system appears to be broadly analogous to the Himalaya, where the foreland fold-thrust belt connects by a shallow seismogenic detachment to structures beneath the main range. The geometry of this detachment may influence earthquake rupture initiation and propagation, potentially playing a significant role in the seismic hazard of the GC.

Optimisation of crash dynamics for bus cabin structure based on attained intrusion and deceleration during a frontal collision

This work presents an evaluation of bus structure during a frontal collision. A finite element (FE) model of a bus frontal structure has been simulated under ANSYS/explicit dynamics. Simulation investigated both front-end deformation and generated deceleration was attained byusing two different impact velocities. Lagrangian function has been used to validate the obtained energy absorption. A lumped mass model in MATLAB/Simulink has been constructed to estimate the design parameters for the proposed zones. Multi-objective function optimization strategy used Genetic Algorithm based on both acceptable deformation and deceleration limits. The experimental tests have been carried out to investigate design parameters on four different samples. Simulation results concluded that both deceleration and deformation deviated from the acceptable limits of occupant safety exceeding the first zone. According to the optimization results, the investigated bus structure produces insufficient behaviour during the first crash zone. It is recommended to increase the front zone length.

Multiobjective discrete optimization using the TOPSIS and entropy method for protection of pedestrian lower extremity

Design of vehicle frontal structures signifies an important topic of studies on protection of pedestrian lower extremity. Conventional optimization has been largely focused on continuous variable problems without involving complexity of human model. Nevertheless, design of frontal structures is commonly discrete from a manufacturing perspective and the responses of the lower extremity of pedestrian are highly nonlinear in nature. For this reason, this study aimed to develop a multiobjective discrete optimization (MODO) algorithm for design of frontal structures involving a pedestrian model. In the proposed MODO method, the order preference by similarity to ideal solution (TOPSIS) was coupled with the entropy algorithm to develop a multiple attribute decision making (MADM) model for converting multiple conflicting objectives into a unified single cost function. The presented optimization procedure is iterated using the successive orthogonal experiment to deal with a large number of design variables and design levels. In this study, the proposed method was first verified by two benchmark examples; and then was applied to a more sophisticated real-life design case of vehicle frontal structure to better protect pedestrian lower extremity from impacting injury. The finite element model was validated via experimental tests first and the optimized design was then prototyped for the further physical tests. The results showed that the algorithm is able to achieve an optimal design in a fairly efficient manner. The proposed algorithm exhibits considerable potential to solve other complex engineering design problems.

Plastic frontal pole cortex structure related to individual persistence for goal achievement

Persistent goal-directed behaviours result in achievements in many fields. However, the underlying neural mechanisms of persistence and the methods that enhance the neuroplasticity underlying persistence, remain unclear. We here demonstrate that the structural properties of the frontal pole cortex (FPC) before tasks contain information that can classify Achievers and Non-achievers (goal-directed persistence) participating in three tasks that differ in time scale (hours to months) and task domains (cognitive, language, and motor learning). We also found that most Achievers exhibit experience-dependent neuroplastic changes in the FPC after completing language and motor learning tasks. Moreover, we confirmed that a coaching strategy that used subgoals modified goal-directed persistence and increased the likelihood of becoming an Achiever. Notably, we discovered that neuroplastic changes in the FPC were facilitated by the subgoal strategy, suggesting that goal-striving, using effective coaching, optimizes the FPC for goal persistence.

Observations of Turbulence at a Near‐Surface Temperature Front in the Arctic Ocean

AbstractHigh‐resolution ocean temperature, salinity, current, and turbulence data were collected at an Arctic thermohaline front in the Nansen Basin. The front was close to the sea ice edge and separated the cold and fresh surface melt water from the warm and saline mixed layer. Measurements were made on 18 September 2018, in the upper 100 m, from a research vessel and an autonomous underwater vehicle. Destabilizing surface buoyancy fluxes from a combination of heat loss to the atmosphere and cross‐front Ekman transport by down‐front winds reduced the potential vorticity in the upper ocean. Turbulence structure in the mixed layer was generally consistent with turbulence production through convection by heat loss to atmosphere and mechanical forcing by moderate winds. Conditions at the front were favorable for forced symmetric instability, a mechanism drawing energy from the frontal geostrophic current. A clear signature of increased dissipation from symmetric instability could not be identified; however, this instability could potentially account for the increased dissipation rates at the front location down to 40 m depth that could not be explained by the atmospheric forcing. This turbulence was associated with turbulent heat fluxes of up to 10 W m−2, eroding the warm and cold intrusions observed between 30 and 60 m depth. A Seaglider sampled across a similar frontal structure in the same region 10 days after our survey. The submesoscale‐to‐turbulence‐scale transitions and resulting mixing can be widespread and important in the Atlantic sector of the Arctic Ocean.

Observations of the warm-tongue circulation in the northern East China Sea

A subsurface thermohaline front semi-permanently formed in association with near-bottom cyclonic circulation in the northern East China Sea was newly found from detailed hydrographic data collected during two cruises in February 2017 (winter) and April 2018 (spring) along with supplementary satellite remote sensing and historical hydrographic data. An alternate intruding frontal structure in water properties was observed across the cyclonic circulation in both seasons as formed by two contrasting water masses—low-temperature and low-salinity (i.e., low spiciness) water transported by the East China Sea Current and high-temperature and high-salinity (i.e., high spiciness) water transported by the Tsushima Warm Current. Consistent structures were confirmed from current observations during the two cruises, historical hydrographic observations, and satellite altimetry-derived sea surface height and surface frontal structure, indicative of retroflection of the Cheju Warm Current as deemed by the seasonal development of thermal stratification in spring. Our results reveal significant heat and material exchanges between the open Pacific and the broad shelf, particularly via diapycnal mixing and cross-front transports associated with across-front flow and cyclonic circulation, in the northern East China Sea.

Structure of Cyclonic Precipitation in the Northern Pacific Storm Track Measured by GPM DPR

AbstractDespite the long existence of theoretical studies, few statistical studies of precipitation characteristics on the northern Pacific storm track have been reported due to lack of observation. Using data from GPM DPR and ERA-Interim, we examined the precipitation features of extratropical cyclones in the northern Pacific storm-track region. Extratropical cyclones were classified into four categories including developing, mature, dissipating, and short-term based on their life stages. Our results show that extratropical cyclones of all categories had a “comma” rainband and precipitation mostly occurred to the east of the cyclonic center. The extratropical cyclones promote precipitation to the east of their centers, but suppress precipitation to the west. Precipitation to the east of the extratropical cyclones had larger and more condensed droplets, a stronger intensity, and a higher rain top than the local seasonal average, while the opposite characteristics were seen to the west. Our results suggest that the different types of vertical air motion and moisture content in these two regions induced by the frontal structure of extratropical cyclones play important roles in the different impact of extratropical cyclones. Furthermore, the different life stages of extratropical cyclones had different degrees of impact on precipitation: the highest impact in the developing stage, followed by the mature stage, and the weakest impact in the dissipating stage.

The Arctic Front and its variability in the Norwegian Sea

Abstract. The Arctic Front (AF) in the Norwegian Sea is an important biologically productive region which is well-known for its large feeding schools of pelagic fish. A suite of satellite data, a regional coupled ocean–sea ice data assimilation system (the TOPAZ reanalysis) and atmospheric reanalysis data are used to investigate the variability in the lateral and vertical structure of the AF. A method, known as “singularity analysis”, is applied on the satellite and reanalysis data for 2-D spatial analysis of the front, whereas for the vertical structure, a horizontal gradient method is used. We present new evidence of active air–sea interaction along the AF due to enhanced momentum mixing near the frontal region. The frontal structure of the AF is found to be most distinct near the Faroe Current in the south-west Norwegian Sea and along the Mohn Ridge. Coincidentally, these are the two locations along the AF where the air–sea interactions are most intense. This study investigates in particular the frontal structure and its variability along the Mohn Ridge. The seasonal variability in the strength of the AF is found to be limited to the surface. The study also provides new insights into the influence of the three dominant modes of the Norwegian Sea atmospheric circulation on the AF along the Mohn Ridge. The analyses show a weakened AF during the negative phase of the North Atlantic Oscillation (NAO−), even though the geographical location of the front does not vary. The weakening of AF during NAO− is attributed to the variability in the strength of the Norwegian Atlantic Front Current over the Mohn Ridge associated with the changes in the wind field.