Meridional Direction Research Articles

Characteristics of convections associated with the Tibetan Plateau vortices based on geostationary satellite data

AbstractTibetan Plateau vortices (TPVs) are major rain producers over the Tibetan Plateau, some of which can move eastward off the plateau and trigger heavy rainfall over southwestern and eastern China. The infrared black body temperature (TBB) data, derived from geostationary meteorological satellite FY‐2E in the period of May–August of 2010–2014, is utilized to investigate the characteristics of convections associated with the moving‐off TPVs. During May–August, negative TBB anomalies appear over the tracks of the TPVs, but are located further north of the tracks in May and June than in July and August. Relative to the centre of TPVs, low TBB appears in the southeast and extends from southwest to northeast, whose values are smaller and ranges are larger before the TPVs move off than after moving off. Distributions of TBB at different evolution times show a close relationship with the characteristics of TPVs. The intensity, scales and shape of the convections linked to the TPVs are explored in the coordinates whose origin is the composite centre of the convections. Generally, convections associated with the TPVs are elliptic and stretch from southwest to northeast, with average spatial scales of approximately 3° in the zonal and 2° in the meridional direction. Convections in July and August are more intensive and lie southwest‐northeast, and those in May and June are weaker with a quasi‐zonal orientation. The horizontal scales of convections are much larger in May and July than those in June and August. Convections are usually larger and more intense before the TPVs move off than after moving off, corresponding to the changes of TPVs.

Dispersion in the Open Ocean Seasonal Pycnocline at Scales of 1–10 km and 1–6 days

AbstractResults are presented from two dye release experiments conducted in the seasonal thermocline of the Sargasso Sea, one in a region of low horizontal strain rate (~10−6 s−1), the second in a region of intermediate horizontal strain rate (~10−5 s−1). Both experiments lasted ~6 days, covering spatial scales of 1–10 and 1–50 km for the low and intermediate strain rate regimes, respectively. Diapycnal diffusivities estimated from the two experiments were κz = (2–5) × 10−6 m2 s−1, while isopycnal diffusivities were κH = (0.2–3) m2 s−1, with the range in κH being less a reflection of site-to-site variability, and more due to uncertainties in the background strain rate acting on the patch combined with uncertain time dependence. The Site I (low strain) experiment exhibited minimal stretching, elongating to approximately 10 km over 6 days while maintaining a width of ~5 km, and with a notable vertical tilt in the meridional direction. By contrast, the Site II (intermediate strain) experiment exhibited significant stretching, elongating to more than 50 km in length and advecting more than 150 km while still maintaining a width of order 3–5 km. Early surveys from both experiments showed patchy distributions indicative of small-scale stirring at scales of order a few hundred meters. Later surveys show relatively smooth, coherent distributions with only occasional patchiness, suggestive of a diffusive rather than stirring process at the scales of the now larger patches. Together the two experiments provide important clues as to the rates and underlying processes driving diapycnal and isopycnal mixing at these scales.

Experimental and Numerical Investigation of Residual Stresses in Incremental Forming

Double Sided Incremental Forming (DSIF) is gaining importance over Single Point Incremental Forming (SPIF) due to its ability to form complex geometries and the capability to obtain better accuracies. In the present work, residual stresses are measured in pyramidal components formed using SPIF, DSIF using X-ray diffraction technique. Residual stress development mechanism during SPIF and DSIF is studied using Finite Element Analysis (FEA). Stress development along circumferential and meridional directions are explained using bending and unbending of sheet material taking place around forming tool. It is observed that the residual stresses are compressive on the outer surface and tensile on the inner surface of sheet in both circumferential and meridional directions. In DSIF, supporting tool restricts the unbending of sheet causing the residual stresses to be less compressive on the outer surface and less tensile on the inner surface compared to SPIF. It is also observed that with an increase in tool diameter, spring back increased, hence, meridional residual stress on the outer surface became more compressive and circumferential residual stress on the inner surface became more tensile. Residual stresses in ISF are compared with FEA predictions of conventional stamping process.

MOMSO 1.0 – an eddying Southern Ocean model configuration with fairly equilibrated natural carbon

Abstract. We present a new near-global coupled biogeochemical ocean-circulation model configuration. The configuration features a horizontal discretization with a grid spacing of less than 11 km in the Southern Ocean and gradually coarsens in meridional direction to more than 200 km at 64∘ N, where the model is bounded by a solid wall. The underlying code framework is the Geophysical Fluid Dynamics Laboratory (GFDL)'s Modular Ocean Model coupled to the Biogeochemistry with Light, Iron, Nutrients and Gases (BLING) ecosystem model of Galbraith et al. (2010). The configuration is unique in that it features both a relatively equilibrated oceanic carbon inventory and an eddying ocean circulation based on a realistic model geometry/bathymetry – a combination that has been precluded by prohibitive computational cost in the past. Results from a simulation with climatological forcing and a sensitivity experiment with increasing winds suggest that the configuration is sufficiently equilibrated to explore Southern Ocean carbon uptake dynamics on decadal timescales. The configuration is dubbed MOMSO, a Modular Ocean Model Southern Ocean configuration.

Eddies and currents in the Bay of Bengal during summer monsoons

The Southwest Monsoon Current (SMC) in the Bay of Bengal (BoB) and prominent eddies surrounding it, in particular, an anticyclonic eddy (AE) to the southeast and a cyclonic eddy (Sri Lanka Dome, SLD) to the east of Sri Lanka, were investigated using field observations, numerical simulations, satellite imagery, laboratory experiments and theoretical studies. The field campaigns were conducted in 2015 and 2018, respectively, in conjunction with the Air-Sea Interactions in the Northern Indian Ocean (ASIRI) and Monsoon Intra-Seasonal Oscillations in Bay of Bengal (MISO-BoB) research initiatives. Ship observations confirmed the presence of a annually recurring AE about 500 km southeast of Sri Lanka, with surface velocities up to ~1 m s−1, size in the meridional direction ~200 km, and penetration approximately to the depth of the thermocline ~150 m. Satellite observations and COAMPS® model simulations show that the AE and the SLD are formed following the appearance of the SMC in early summer, and both evolve during July/August and disappear in September. This result is at odds with the prevailing notion that the AE is a result of the interaction between the SMC and Rossby waves arriving from the southeast of the BoB, carrying energy of a blocked Wyrtki jet at the Sumatra coast; such waves do not arrive in the southwestern BoB until August/September. Simultaneous appearance of AE and SLD is inconsistent with a recently proposed mechanism in which SLD is formed due to separation of the SMC from the Sri Lanka coast. A new hypothesis is proposed wherein the AE and the SLD are generated by topographically trapped Rossby wave response of the SMC to perturbations by the Sri Lankan coast. Observations of the size, location and origins of the AE were broadly consistent with this hypothesis, so were the results of a laboratory experiment designed to mimic natural flow in the BoB by creating an eastward jet (SMC) on a simulated β plane. Sea surface temperature (SST) observations show that the SMC carries colder upwelled water from the southern Sri Lankan and Indian coasts and distributes it within the surface waters of the AE and beyond. Thus, the surface waters of the AE are colder than that of the SLD, notwithstanding perceived local upwelling in the SLD, suggesting that SMC may play a controlling role in the air-sea interactions of the southern BoB.

Features of the formation of the St. Petersburg agglomeration by the beginning of the XX century

The study of the Russian historical St. Petersburg agglomeration at all stages from its foundation (from 1703) until the final imperial stage (1917) required the use of complex functional, urban-planning and landscape, socio-economic, environmental, transport and communication analysis on the basis of data from archives, historical cartography and iconography. The main results were the conclusions that during the XVIII - early XX centuries, there was a crystallization of a huge agglomeration around the city of St. Petersburg, which included three belts: “external”, “middle”, “nearby”, which spatially extended from Yaroslavl (in Central Russia) to Riga (in the Baltic). The paper discusses the features of the formation of the “nearby belt” of agglomeration in the initial (1703 - January 1725) and in the final (1901-1916) development periods. The study revealed a significant role of special types of objects in these processes - estates of the aristocratic society and “garden cities” that provided a belt (around St. Petersburg and the largest settlements and complexes), linear (along radial and ring highways), and nodal (around individual large settlements) construction, spreading in the latitudinal direction from Narva and Ivangorod to the mouth of the Syas river, and in the meridian direction - from Vyborg to the city of Luga. Within the boundaries of this agglomeration zone, four sub-agglomerations had begun to emerge since the 1710s and have fully formed by the 1910s. The materials of the paper can be useful both for historians of urban planning and for modern urbanists.

The Relationship Between Abnormal Meiyu and Medium-Term Scale Wave Perturbation Energy Propagation Along the East Asian Subtropical Westerly Jet

The East Asian subtropical westerly jet (EASWJ) is one of the most important factors modulating the Meiyu rainfall in the Yangtze-Huaihe River Basin, China. This article analyzed periods of the medium-term EASWJ variation, wave packet distribution and energy propagation of Rossby waves along the EASWJ during Meiyu season, and investigated their possible influence on abnormal Meiyu rain. The results showed that during the medium-term scale atmospheric dynamic process, the evolution of the EASWJ in Meiyu season was mainly characterized by the changes of 3-8 d synoptic-scale and 10-15 d low-frequency Rossby waves. The strong perturbation wave packet and energy propagation of the 3-8 d synoptic-scale and 10-15 d low-frequency Rossby waves are mostly concentrated in the East Asian region of 90°-150°E, where the two wave trains of perturbation wave packets and wave-activity flux divergence coexist in zonal and meridional directions, and converge on the EASWJ. Besides, the wave trains of perturbation wave packet and wave-activity flux divergence in wet Meiyu years are more systematically westward than those in dry Meiyu years, and they are shown in the inverse phases between each other. In wet (dry) Meiyu year, the perturbation wave packet high-value area of the 10-15 d low-frequency variability is located between the Aral Sea and the Lake Balkhash (in the northeastern part of China), while over eastern China the wave-activity flux is convergent and strong (divergent and weak), and the high-level jets are strong and southward (weak and northward). Because of the coupling of high and low level atmosphere and high-level strong (weak) divergence on the south side of the jet over the Yangtze-Huaihe River Basin, the low-level southwest wind and vertically ascending motion are strengthened (weakened), which is (is not) conducive to precipitation increase in the Yangtze-Huaihe River Basin. These findings would help to better understand the impact mechanisms of the EASWJ activities on abnormal Meiyu from the perspective of medium-term scale Rossby wave energy propagation.

Lead-zinc mineralization of fluoriton-bearing areas of the Middle Transnistria

The territory of Middle Transnistria within the Podolsk tectonic zone is a fluorite-bearing province. Together with fluorite manifestations, sulfide mineralization is developed. The research is based on the original stone material, which has been studied using chemical, spectral and microprobe analysis, as well as the results of previous studies of fluorite-polymetallic ore occurrences in the Podolsk tectonic zone (reports of geological works, published and stock literature). Polymetallic (Pb-Zn) mineralization is represented by cement, dissemination and thin veinlets of galena and sphalerite in fluorite-bearing sandstones of the Upper Proterozoic (Olchedaev and Yampol layers), and also rocks of the crystalline basement (in calcite and calcite-fluorite veinlets). Mostly, sandstones consist of quartz — 35—75%, feldspar — 15—45%, rock fragments — up to 20%, altered biotite (up to 5%), as well as accessory minerals, which are represented by single grains of garnet, cordierite, apatite, tourmaline, zircon, monazite. Fluorite-bearing areas with signs of lead-zinc mineralization (galena, sphalerite) have been analyzed, the mineral composition and textural features of sandstones with Pb, Zn contents in the most promising ore occurrences of fluorite have been determined. On this basis, fluorite-polymetallic ore occurrences were identified, a catalog was compiled indicating the content of fluorite, lead and zinc in them. It is shown that most of the polymetallic ore occurrences of the Podolsk tectonic zone are located in the zones of intersection with tectonic faults of the northeastern and meridional directions. The most promising areas for the integrated extraction of fluorite and polymetals (Pb-Zn) were identified: the content of fluorite, the area of deposits and their thickness were taken into account; the content of polymetals and the availability of extraction of the useful component. These criteria are most consistent with the areas – Bakhtyn-Zolotogorsk, Yaryshev-Voevodchin and Vinozh.

'Physical Geography of the Malayan Peninsula'

'Physical Geography of the Malayan Peninsula' J. E. Tenison-Woods Source: Nature, December 18, 1884, pp. 152-4 As some remarks of mine on the mountain system of the Malayan peninsula have already appeared in NATURE, perhaps the following summary of the results of ten months' explorations in the State of Perak will be interesting. The State of Perak is comprised between the sea (Straits of Malacca) and the main central chain which runs along the centre of the peninsula. Its boundaries are, roughly: north, the River Krian; south, River Bernam; west, the ocean; east, the main central chain. The geology may be briefly described as consisting of — (1). an immense granite formation, rising into extremely sharp and precipitous parallel ridges having nearly a meridional direction. This granite passes frequently into slates and schists. The prevailing colour is blue. (2). A Palaeozoic formation of slates, mottled sandstones, and clays, forming outliers or detached portions. It is found most abundantly at the foot of the ranges, whence it usually dips away conformably to the slopes of the hills and mountains. It has evidently been subject to great denudation. (3). Limestone in detached outliers, or isolated hills of precipitous character, showing much denudation. It is stratified or crystalline. No fossils have been found yet, but is probably of Palaeozoic age. From its wide extension throughout Perak, where it crops out in so many places, it may have once covered the whole of the granite and Palaeozoic clays. (4). Drifts and alluvium from the ancient streams and river beds. These are formed of the material from all the preceding deposits. All the tin deposits in the country are in these drifts. The ore occurs in a manner very similar to the alluvial gold in Australia, that is to say, in "leads," which are the ancient or modern river beds. Above these alluvial deposits there is the usual alluvial surface soil, for the most part supporting a very dense vegetation. The tin deposits hitherto formed are all stream tin. No lodes have yet been worked, though there are some in the mountains round the sources of the Perak River. The ore is almost always cassiterite in small abraded crystals. It is of a peculiar blackish-gray or brown aspect. Any person with a little experience would be able to distinguish between tin sand from Australia and that of Perak. The former is rather rich in gems, such as sapphires, rubies, hyacinths, garnets, topazes, and zircons. I [End Page 137] have never seen any in Perak; but there is a good deal of fluorspar, tourmaline, and less frequently wolfram. The most of the workings are on the western slopes at the foot of the mountains. I cannot recall any instances of mines on the eastern slopes, but the wash or drift seems to have been greater on that side. The matrix of the tin seems to be in the upper part of the granite at its junction with the Palaeozoic clays. In the lower part of the clay there is also a small quantity of tin. In the drift the tin is always found in nearly the lowest levels, lying in one or two strata from one foot to five feet thick. It is mingled with fine drift sand and gravel. Its position is, I think, due to the repeated sifting and washing it has been subject to in the stream bed. But as it is generally covered by from ten to thirty feet of material destitute of tin, the inference is that only one part of the granite was very rich in the metal. The stream tin deposits lie upon (1) kaolin clay, or partly decomposed granite; (2) granite; (3) Palaeozoic sandstones and clays. In the latter case the stream has come from the denudation of a portion of the same strata on the tipper slopes of the hills. On the highest granite ridges, or those above 5000 feet, there is found a distinct vegetation. Three or four of the genera are Australian (Melalenca, Leptospermum, podocarpus, Leucopogon), and two of the species (Leptospremum and Leucopogon) are common Australian forms. Similar facts have been observed in Borneo, but I have not heard that they had...

Resistive accretion flows around a Kerr black hole

AbstractIn this paper, we present the stationary axisymmetric configuration of a resistive magnetised thick accretion disc in the vicinity of external gravity and intrinsic dipolar magnetic field of a slowly rotating black hole. The plasma is described by the equations of fully general relativistic magnetohydrodynamics (MHD) along with the Ohm’s law and in the absence of the effects of radiation fields. We try to solve these two-dimensional MHD equations analytically as much as possible. However, we sometimes inevitably refer to numerical methods as well. To fully understand the relativistic geometrically thick accretion disc structure, we consider all three components of the fluid velocity to be non-zero. This implies that the magnetofluid can flow in all three directions surrounding the central black hole. As we get radially closer to the hole, the fluid flows faster in all those directions. However, as we move towards the equator along the meridional direction, the radial inflow becomes stronger from both the speed and the mass accretion rate points of view. Nonetheless, the vertical (meridional) speed and the rotation of the plasma disc become slower in that direction. Due to the presence of pressure gradient forces, a sub-Keplerian angular momentum distribution throughout the thick disc is expected as well. To get a concise analytical form of the rate of accretion, we assume that the radial dependency of radial and meridional fluid velocities is the same. This simplifying assumption leads to radial independency of mass accretion rate. The motion of the accreting plasma produces an azimuthal current whose strength is specified based on the strength of the external dipolar magnetic field. This current generates a poloidal magnetic field in the disc which is continuous across the disc boundary surface due to the presence of the finite resistivity for the plasma. The gas in the disc is vertically supported not only by the gas pressure but also by the magnetic pressure.

Тяжелые металлы в почвах геохимически сопряженных ландшафтов Красноуральского промышленного узла

The results of a study of the gross content of heavy metals in soils in the area of operation of the Svyatogor copper smelter located in the Sverdlovsk region are presented. In the course of the research, sections were laid at different distances and directions from the emission source. The gross concentration of Zn, Cd, Pb, and Cu was measured in the selected soil samples. According to the results of the analysis, a ranking was carried out with the calculations of the total pollution coefficient, lateral and radial differentiation of heavy metals, and the technogenicity index. In order to confirm the routes of the arrival of heavy metals with airport emissions, the maximum single surface concentration in atmospheric air was calculated with the calculation of the distance at which this concentration reaches its maximum value. In the calculation of the total pollution coefficient, it follows that areas located in the immediate vicinity of the emission source have an extremely dangerous category of soil pollution. Also, in these areas, the proportion of technogenic involvement of the element is more than 90%. The obtained values of the coefficient of radial differentiation of heavy metals in the meridional and latitudinal directions, indicates the presence of a number of physical and chemical geochemical geochemical barriers. The migration of heavy metals between conjugated systems is confirmed by the lateral differentiation coefficients. In the course of the work, the main sources of heavy metals entering the soil were identified, such aero-industrial emissions of the plant and aeolian transfer from technogenic disturbed lands. Among the identified patterns of distribution of heavy metals, the main ones are the presence of a high degree of relations of disturbed lands with autonomous natural areas and periodic changes in the direction and power of aero-technogenic flows of the plant.

Tropospheric circulation response to sudden stratospheric warming observed in January 2013

Analysis of the dynamical regime changes in the stratosphere during different phases of the Sudden Stratospheric Warming (SSW) that has been observed in January 2013 is presented. The different mechanisms of SSW influence on the tropospheric circulation through the stationary planetary waves (SPWs) reflection and/or increase in SPWs activity due to nonlinear interaction with the mean flow and their subsequent propagation into the troposphere are discussed. Three-dimensional wave activity flux and its divergence are determined using the UK Met Office data; the synoptic situation and its changes during the SSW events are analyzed. The wave activity penetrates downward from stratosphere into the troposphere and can affect weather processes during the SSW and right afterwards. It is this time that polar anticyclones can be formed at high latitudes, which quickly go southward along meridional directions and then deviate to the East at middle latitudes. Interestingly, the locations of polar anticyclone formations and subsequent displacements correspond to the regions of maximal horizontal wave activity fluxes connected with stratospheric processes. The results obtained allow us to suggest that accounting of stratospheric processes and their influence on the troposphere in winter season can improve the middle-range forecast of anticyclone formation and cold weather events at middle latitudes.

CHERTOMLYK AND KOZEL: BARROWS, HORSES AND CROSSING

According to Dr. Yu. Boltrik’s works the Scythian royal barrows were situated on the high places (watersheds) as well as along the roads. One of the biggest roads marked by Oguz, Solokha, Kozel, Chertomlyk and Alexandropol barrows run in meridional direction and crossed the Dnieper. The Dnieper crossing was a start point in barrow creation: the later is a barrow, the more distant from the Dnieper crossing it is placed. Kozel and Chertomlyk barrows situated across the Dnieper (Kozel on the left coast, Chertomlyk — on the right one), both dated to the second half of the 4th century BC, are similar in planigraphy, quantity of buried horses and some details of their arrangement.
 In both barrows the horses were buried in special tombs situated to the West of the central tomb. Each horse tomb consisted of three large rectangular separate pits formed a line situated North-South.
 In both cases 11 horses were buried. Their bridles were made of two metals: of silver and gold in Chertomlyk and of bronze and silver — in Kozel. Some had also saddles with golden plates and some had bronze breast (neck) dressings.
 We compared the arrangement of horses in the tombs of Kozel and Chertomlyk concerning the Dnieper crossing and observed a kind of bilateral symmetry in it. So we may suppose they had in mind this crossing not only constructing barrows but burying horses too.
 River crossing in archaic cultures is a border dangerous to overcome. Because of that some rituals should be performed and some constructions installed at that place. Near the Dnieper crossing a group of Scythian barrows is known. The Dnieper direction in this place is latitudinal and the direction of road — meridional, so the place of crossing looks like a center of sacred space, and the way to it is also sacred.
 So we do not except the Dnieper crossing was significant for arranging horses’ tombs in Kozel and Chertomlyk barrows.

Фізико-географічна характеристика Лемківщини

The article presents the physical-geographical characteristics of the Lemkos’ ethnic territory, the farthest western ethnographic group of Ukrainians who have long inhabited the slopes of the Carpathians Eastern Beskids. Lemkivshchyna is located on both slopes of the Carpathian Beskids between the Borzhava and San rivers in the east and Poprad and Dunajec in the west, located in three countries. The total area is about 9 000 km2. Lemkivschyna occupies the largest area within the mountainous part of South-Eastern Poland (48 %), less in the mountainous part of north-eastern Slovakia (41 %), the least in the Trans¬carpathian region of Ukraine (11 %). Most of the territory of Lemkivshchyna is located in the Carpathian lowlands of the Eastern Beskids. Only some peaks have a height of more than 1 000 m. The highest peak is Tarnitsa (1 346 m a.s.l.) on the Bukovo Berdo ridge. Lemkivshchyna is located in the temperate climate zone of Europe, which is formed under the influence of the western transfer of the Atlantic air masses. In addition, the climatic characteristics are influenced by the terrain, altitude, exposure of the slopes, the direction of extension of the mountain valleys. The territory of Lemkivshchyna lies on the Main European Watershed. The rivers that originate in the northern macro-slope of the Low Beskid are tributaries of the Vistula (the Baltic Sea basin). The rivers of the southern macro-slope are tributaries of the Tisza River, which flows into the Danube (the Black Sea basin). The largest river in the Lemky region is the San (444 km in length). Another tributary of the Vistula is the Vislok (165 km). The mountain rivers that originate on the southern slopes of the Low Beskid River flow in a meridional direction to the south and belong to the Tisza basin. The largest among them are Gorand (286 km), Poprad (169 km), Laborets (129 km), Ondava (112 km in length). The rivers of Lemkivshchyna are characterized by mixed food dominated by snow. Boundaries are observed in winter and during the dry season in summer. Floods can occur at any time of the year during heavy rainfall. The mountain-forest soils of Lemkivshchyna are formed on flysch rocks under beech and fir forests. Soils of low power (up to 75 cm), often stony, characterized by high acidity, poor in calcium, magnesium, phosphorus, iron. Mountain-meadow soils were formed in the subalpine meadows. The processes of accumulation of peat and organic material are observed on the watersheds and sites of poor runoff. The geographical location of Lemkivshchyna causes the vertical extent of the vegetation cover, which differs from the other mountain ranges of the Carpathians. Belt of deciduous forests, rising to an altitude of 1 156 m. is mainly represented with beech forests. The belt of the Polonynian subalpine meadows that developed under the influence of a long pasture farm is above the beech forests. About 1 000 species of vascular plants, more than 600 species of mosses and lichens, and many algae and fungi have been found in the Lemky region. A modern feature of the vegetation cover of Lemkivshchyna is the natural regeneration of forests, which occurred after the expulsion of the ethnic population from these territories. More than 200 species of vertebrates have been found in the Lemky region. Key words: Lemkivshchyna, physical and geographical conditions, relief of the Eastern Beskids, hydrography, vegetation.

Analysis of the Spatial Vibrations of Coaxial Cylindrical Shells Partially Filled with a Fluid

This paper is devoted to a numerical study of the natural vibrations of horizontally oriented elastic coaxial shells the annular gap between which is completely or partially filled with a compressible viscous fluid. The problem is solved in a three-dimensional formulation using the finite element method. The fluid motion is described in the acoustic approximation in terms of the velocity potential. The relevant equations together with the boundary conditions corresponding to complete contact on the wetted surfaces are transformed using the Bubnov-Galerkin method. The hydrodynamic forces are found from the viscous stress tensor. The mathematical formulation of the problem of thin-walled structure dynamics is based on the variational principle of virtual displacements that includes the normal and tangential components of the forces exerted by the fluid on the wetted parts of elastic bodies. The shells are modeled by assuming that their curvilinear surfaces are approximated quite accurately by a set of plane elements whose strains are determined according to the classical theory of thin plates. The results obtained have been validated by comparing them with the known published data for the case where the entire volume of the annular gap is filled with an ideal fluid. The influence of the fluid level and gap size on the natural frequencies and the corresponding vibration modes of coaxial shells with a variety of boundary conditions is estimated. It is demonstrated that partial filling leads to a splitting of the natural vibration frequencies, with a decrease in the fluid volume promoting the growth of their minimum values. It is shown that at some gap size mixed vibration modes can appear not only in the meridional direction, but also in the circumferential one.

Simulation study of mitigation of plasma bubble effects on GBAS using a VHF radar

Plasma bubbles can affect ground-based augmentation system (GBAS) performance by posing large spatial ionospheric gradients between the aircraft and the airport, which makes it important to detect plasma bubbles effectively. In this study, we investigate the use of VHF radar to detect plasma bubbles and mitigate their potential impact on GBAS through a simulation. When the line-of-sight of a certain GPS satellite is determined to be passing through an area of plasma bubbles as detected by EAR, such GPS satellite shall be removed from the positioning calculation on board the aircraft. We set up different simulation scenarios by varying the satellite geometry, and airport coordinate. Results are described in the form of vertical protection level (VPL) and vertical position error (VPE), which we then analyse as a function of zonal and meridional distance. The results show that such a radar-based monitoring system can be used to mitigate the effects of plasma bubbles on GBAS to cover surrounding airports within a certain range, especially in the meridional direction.

A semi-analytical approach on the effect of external lateral pressure on free vibration of joined sandwich aerospace composite conical-conical shells

This paper investigates the free vibrational behaviors of joined composite sandwich conical-conical shells under external lateral pressure. The corresponding equations are derived based on the first order shear deformation theory (FSDT). Herewith, free vibration equations are extracted via applying Hamilton's principle and considering initial mechanical stresses solved by static equilibrium equations. To establish the continuity of two conical shells, compatibility of displacements and stress resultants are satisfied at the junctions. The generalized differential quadrature (GDQ) method is adopted to discretize the governing equations for each conical segment, together with related boundary and continuity conditions in a meridian direction. In order to verify the results as well as representing the convergence of the presented approach, some pieces of case studies are accomplished. These studies provide a better exhibition of lateral pressure, cone angles and shell thickness influences on the free vibration of joined composite sandwich conical shells with various boundary conditions. Then, the effect of four different types of materials which are more applicable in pressurized environments such as underwater and submarine structures, i.e. polyetheretherketon (PEEK), polycarbonate (PC), solid propylene (SPP), and high density polyimide foam (HDPF) are investigated for the core layer. Critical buckling pressure in the present approach is obtained when the natural frequency takes the value of zero for the lowest pressure. Finally, the values of lateral pressure are selected considering the critical buckling pressure to avoid buckling occurrence.

A unified formulation for dynamic behavior analysis of spherical cap with uniform and stepped thickness distribution under different edge constraints

Abstract The research introduces a unified method to investigate the dynamic behavior of spherical caps with uniform and stepped thickness under different edge constraints. In the framework of thin shell theory, the mathematical model of spherical cap is proposed. By combining the multi-section partition technique and Rayleigh-Ritz method, the vibration characteristics of spherical caps can be obtained. The spherical cap is partitioned into sections along the meridian direction, in which the displacement components of spherical caps along meridian and circumferential direction are respectively represented by Jacobi polynomials and Fourier series. Based on the virtual boundary spring stiffness technique, different edge conditions can be easily simulated. The comparison with FEM, modal test and published literatures prove the accuracy and dependability of current method. The impacts of geometric parameters and edge constraints on the vibration characteristics of spherical cap are also discussed.

Spatio-temporal variability of surface water pCO2 and nutrients in the tropical Pacific from 1981 to 2015

This study presents a synthesis of surface water partial pressure of CO2 (pCO2) and nutrient observations in the tropical Pacific (20°S–20°N) from 1981 to 2015 and characterizes the spatio-temporal variability. We used data from the Surface Ocean CO2 Atlas version 5, which include about 2 million pCO2 measurements in the tropical Pacific. Unlike many previous studies that estimated pCO2 fields from relationships with other variables like sea surface temperature, we developed gridded products of monthly means using a technique to interpolate measured pCO2 values. Large seasonal variation of pCO2 appears in the cold tongue region (EQ–20°S, east of 120°W) corresponding to the seasonal variation of coastal upwelling, and in the off-equatorial region where the thermodynamic effect on pCO2 dominates. Consistent with previous findings, pCO2 along the equator declines during El Niño due to weakening of the easterly winds and therefore reduced upwelling of CO2 rich subsurface water. We also quantified the spatial distribution of the long-term pCO2 trend beyond the area-averaged trend presented previously. The long-term trend of pCO2 is positive in all regions with an area average of 1.8 ± 0.1 μatm yr−1. However, along the equator the trend is > 2 μatm yr−1 linked to the Pacific Decadal Oscillation forcing. Using the same methodology, we also analyzed about 20,000 surface nutrient measurements from the Global Ocean Data Analysis Project version 2, World Ocean Database 2013, and ship-of-opportunity sampling by the National Institute for Environmental Studies, Japan. We present the spatial patterns of reduced surface nutrient concentration in the central to eastern tropics along the equator during El Niño, but there are not enough data to characterize the trends of nutrients in the tropical Pacific.Decorrelation analyses are also applied using covariance between pCO2 anomalies separated by a lag increment for zonal, meridional, and temporal directions. The e-folding scale of pCO2 is estimated to be 6° in latitude, 13° in longitude, and 2 months with a signal-to-noise ratio of 4, which are used as input for the interpolation as well as an assessment of ideal observation density and frequency. Decorrelation analyses such as this are critical for evaluating existing observing system design and informing future sampling strategies.

Design of Compressed Natural Gas Pressure Vessel (Type II) to Improve Storage Efficiency and Structural Reliability

Abstract Type II storage vessel, which consists of a metallic liner hoop wrapped with a carbon fiber-resin composite to work at high pressure, has been widely adopted as the fuel container for compressed natural gas (CNG) vehicles. The general vessel, manufactured by welding enclosures to an open-end cylinder, shows uniform thickness throughout the whole liner, while the high pressure vessel, fabricated by the deep drawing and ironing (D.D.I) and spinning processes, has the integral junction part of cylinder with increased end thickness along the meridian direction. This study established a design method for improvement of failure resistance and inner capacity of the seamless CNG pressure vessel (Type II) through finite element analysis with consideration of thickness variation. Autofrettage pressure is used to enhance fracture performance and fatigue life of the vessel, and variations of stress behaviors in the liner and composite were analyzed during the autofrettage process. The influence of the composite on generation of compressive residual stress was investigated. In order to verify advantages of the D. D. I. and the spinning processes for structural safety at the end closure, the stress distribution considering thickness variation was compared with that with uniform thickness, and the maximum inner capacity objective satisfying structural reliability was obtained. The inner capacity of the proposed model with the ratio of major axis to minor axis, 2.2, was expanded by 4.5. Theoretical equivalent stresses were compared with those from the simulations, and the technique of FEM was verified.