Model simulation of the large-scale high-latitude F-layer modification by powerful HF waves with different modulation

In this paper, a 3-D numerical model is proposed to investigate the capability of generating high operating temperature for a modified solar cavity receiver in large-scale dish Stirling system. The proposed model aims to evaluate the influence of radiation intensity on the cavity receiver performance. The properties of the heat transfer fluid in the pipe and heat transfer losses of the receiver are investigated by varying the direct normal irradiance from 400W/m2 to 1000W/m2. The temperature of heat transfer fluid, as well as the effect of radiation intensity on the heat transfer losses have been critically presented and discussed. The simulation results reveal that the heat transfer fluid temperature and thermal efficiency of the receiver are significantly influenced by different radiation flux. With the increase of radiation intensity, the efficiency of the receiver will firstly increase, then drops after reaching the highest point. The outlet working fluid temperature of the pipe will be increased consistently. The results of the simulations show that the designed cylindrical receiver used in dish Stirling system is capable to achieve the targeted outlet temperature and heat transfer efficiency, with an acceptable pressure drop.

Download Full-text

Small-scale characteristics of extremely high latitude aurora

Annales Geophysicae ◽

10.5194/angeo-27-3335-2009 ◽

2009 ◽

Vol 27 (9) ◽

pp. 3335-3347 ◽

Cited By ~ 8

Author(s):

J. A. Cumnock ◽

L. G. Blomberg ◽

A. Kullen ◽

T. Karlsson ◽

Keyword(s):

High Latitude ◽

Large Scale ◽

Small Scale ◽

Strong Correlations ◽

Polar Cap ◽

Plasma Flows ◽

Ionospheric Convection ◽

Local Closure ◽

Scale Characteristics

Abstract. We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF By. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.

Download Full-text

Watermasses as a unifying framework for understanding the Southern Ocean carbon cycle

Biogeosciences Discussions ◽

10.5194/bgd-7-3393-2010 ◽

2010 ◽

Vol 7 (3) ◽

pp. 3393-3451 ◽

Cited By ~ 3

Author(s):

D. Iudicone ◽

I. Stendardo ◽

O. Aumont ◽

K. B. Rodgers ◽

G. Madec ◽

...

Keyword(s):

Southern Ocean ◽

Large Scale ◽

Thermohaline Circulation ◽

Model Simulation ◽

Polar Front ◽

Global Ocean ◽

Inversion Method ◽

Co2 Fluxes ◽

Meridional Transport ◽

Regional Patterns

Abstract. A watermass-based framework is presented for a quantitative understanding of the processes controlling the cycling of carbon in the Southern Ocean. The approach is developed using a model simulation of the global carbon transports within the ocean and with the atmosphere. It is shown how the watermass framework sheds light on the interplay between biology, air-sea gas exchange, and internal ocean transport including diapycnal processes, and the way in which this interplay controls the large-scale ocean-atmosphere carbon exchange. The simulated pre-industrial regional patterns of DIC distribution and the global distribution of the pre-industrial air-sea CO2 fluxes compare well with other model results and with results from an ocean inversion method. The main differences are found in the Southern Ocean where the model presents a stronger CO2 outgassing south of the polar front, a result of the upwelling of DIC-rich deep waters into the surface layer. North of the subantarctic front the typical temperature-driven solubility effect produces a net ingassing of CO2. The biological controls on surface CO2 fluxes through primary production is generally smaller than the temperature effect on solubility. Novel to this study is also a Lagrangian trajectory analysis of the meridional transport of DIC. The analysis allows to evaluate the contribution of separate branches of the global thermohaline circulation (identified by watermasses) to the vertical distribution of DIC throughout the Southern Ocean and towards the global ocean. The most important new result is that the overturning associated with Subantarctic Mode Waters sustains a northward net transport of DIC (15.7×107 mol/s across 30° S). This new finding, which has also relevant implications on the prediction of anthropogenic carbon redistribution, results from the specific mechanism of SAMW formation and its source waters whose consequences on tracer transports are analyzed for the first time in this study.

Download Full-text

Group Buying-based Data Transmission in Flying Ad-hoc Networks: A Coalition Game Approach

10.20944/preprints201809.0260.v1 ◽

2018 ◽

Author(s):

Lang Ruan ◽

Jin Chen ◽

Qiuju Guo ◽

Xiaobo Zhang ◽

Yuli Zhang ◽

...

Keyword(s):

Formation Mechanism ◽

Coalition Formation ◽

Data Transmission ◽

Large Scale ◽

Ad Hoc ◽

Model Simulation ◽

System Model ◽

Throughput Maximization ◽

Coalition Game ◽

Group Buying

In scenarios such as natural disasters and military strike, it is common for unmanned aerial vehicles (UAVs) to form groups to execute reconnaissance and surveillance. To ensure the effectiveness of UAV communications, repeated resource acquisition issues and transmission mechanism design need to be addressed urgently. In this paper, we build an information interaction scenario in a Flying Ad-hoc network (FANET). The data transmission problem with the goal of throughput maximization is modeled as a coalition game framework. Then, a novel mechanism of coalition selection and data transmission based on group-buying is investigated. Since large-scale UAVs will generate high transmission overhead due to the overlapping resource requirements, we propose a resource allocation optimization method based on distributed data content. Comparing existing works, a data transmission and coalition formation mechanism is designed. Then the system model is classified into graph game and coalition formation game. Through the design of the utility function, we prove that both games have stable solutions. We also prove the convergence of the proposed approach with coalition order and Pareto order. Binary log-linear learning based coalition selection algorithm (BLL-CSA) is proposed to explore the stable coalition partition of system model. Simulation results show that the proposed data transmission and coalition formation mechanism can achieve higher data throughput than the other contrast algorithms.

Download Full-text

An Interpretation of the Distribution of Metre Wavelength Radio Emission

Australian Journal of Physics ◽

10.1071/ph680167 ◽

1968 ◽

Vol 21 (2) ◽

pp. 167 ◽

Cited By ~ 35

Author(s):

KW Yates

Keyword(s):

High Latitude ◽

Large Scale ◽

Galactic Halo ◽

Galactic Plane ◽

Absolute Calibration ◽

Fundamental Difficulty ◽

The Galaxy ◽

Calibration Accuracy ◽

Limit Estimate ◽

Spiral Arm

A recent 85 MHz survey of the southern sky had an absolute calibration accuracy and resolution comparable with a number of surveys made for the northern skies. By combining the results of these surveys in both hemispheres a complete sky map has been produced, and in this paper an analysis is made of the distribution of the medium and high latitude emission. A fundamental difficulty encountered is the identification and isolation of the spurs of emission projecting from the galactic plane. Two hypotheses are proposed. The first attributes the spurs to a large-scale feature associated with the galactic core and the remaining emission to a galactic halo. The second postulates the origin of the spurs within the local spiral arm, which is itself considered to contribute significantly to the high latitude background. An upper-limit estimate of the emissivity of the local arm is made from currently available independent data. Using this result a model local arm is proposed, which, together with an isotropic component from beyond the Galaxy and a small additional galactic component, explains the observed distribution.

Download Full-text

Expansion and diversification of high-latitude radiolarian assemblages in the late Eocene linked to a cooling event in the Southwest Pacific

Climate of the Past Discussions ◽

10.5194/cpd-11-2977-2015 ◽

2015 ◽

Vol 11 (4) ◽

pp. 2977-3018 ◽

Cited By ~ 1

Author(s):

K. M. Pascher ◽

C. J. Hollis ◽

S. M. Bohaty ◽

G. Cortese ◽

R. M. McKay

Keyword(s):

Oxygen Isotope ◽

High Latitude ◽

Large Scale ◽

Middle Eocene ◽

Late Eocene ◽

Climate History ◽

Southwest Pacific ◽

Early Oligocene ◽

Radiolarian Assemblages

Abstract. The Eocene was characterised by "greenhouse" climate conditions that were gradually terminated by a long-term cooling trend through the middle and late Eocene. This long-term trend was determined by several large-scale climate perturbations that culminated in a shift to "ice-house" climates at the Eocene–Oligocene Transition. Geochemical and micropaleontological proxies suggest that tropical-to-subtropical sea-surface temperatures persisted into the late Eocene in the high-latitude Southwest Pacific Ocean. Here, we present radiolarian microfossil assemblage and foraminiferal oxygen and carbon stable isotope data from Deep Sea Drilling Project (DSDP) Sites 277, 280, 281 and 283 from the middle Eocene to early Oligocene (~ 40–33 Ma) to identify oceanographic changes in the Southwest Pacific across this major transition in Earth's climate history. The Middle Eocene Climatic Optimum at ~ 40 Ma is characterised by a negative shift in foraminiferal oxygen isotope values and a radiolarian assemblage consisting of about 5 % of low latitude taxa Amphicraspedum prolixum group and Amphymenium murrayanum. In the early late Eocene at ~ 37 Ma, a positive oxygen isotope shift can be correlated to the Priabonian Oxygen Isotope Maximum (PrOM) event – a short-lived cooling event recognized throughout the Southern Ocean. Radiolarian abundance, diversity, and preservation increase during the middle of this event at Site 277 at the same time as diatoms. The PrOM and latest Eocene radiolarian assemblages are characterised by abundant high-latitude taxa. These high-latitude taxa also increase in abundance during the late Eocene and early Oligocene at DSDP Sites 280, 281 and 283 and are associated with very high diatom abundance. We therefore infer a~northward expansion of high-latitude radiolarian taxa onto the Campbell Plateau towards the end of the late Eocene. In the early Oligocene (~ 33 Ma) there is an overall decrease in radiolarian abundance and diversity at Site 277, and diatoms are absent. These data indicate that, once the Tasman Gateway was fully open in the early Oligocene, a frontal system similar to the present day was established, with nutrient-depleted subantarctic waters bathing the area around DSDP Site 277, resulting in a more oligotrophic siliceous plankton assemblage.

Download Full-text

Neural Differentiation Dynamics Controlled by Multiple Feedback Loops in a Comprehensive Molecular Interaction Network

Processes ◽

10.3390/pr8020166 ◽

2020 ◽

Vol 8 (2) ◽

pp. 166

Author(s):

Tsuyoshi Iwasaki ◽

Ryo Takiguchi ◽

Takumi Hiraiwa ◽

Takahiro G. Yamada ◽

Kazuto Yamazaki ◽

...

Keyword(s):

Regulatory Network ◽

Neural Differentiation ◽

Large Scale ◽

Model Simulation ◽

Interaction Network ◽

Feedback Loops ◽

Characteristic Change ◽

Large Network ◽

Large Scale Network ◽

Scale Network

Mathematical model simulation is a useful method for understanding the complex behavior of a living system. The construction of mathematical models using comprehensive information is one of the techniques of model construction. Such a comprehensive knowledge-based network tends to become a large-scale network. As a result, the variation of analyses is limited to a particular kind of analysis because of the size and complexity of the model. To analyze a large-scale regulatory network of neural differentiation, we propose a contractive method that preserves the dynamic behavior of a large network. The method consists of the following two steps: comprehensive network building and network reduction. The reduction phase can extract network loop structures from a large-scale regulatory network, and the subnetworks were combined to preserve the dynamics of the original large-scale network. We confirmed that the extracted loop combination reproduced the known dynamics of HES1 and ASCL1 before and after differentiation, including oscillation and equilibrium of their concentrations. The model also reproduced the effects of the overexpression and knockdown of the Id2 gene. Our model suggests that the characteristic change in HES1 and ASCL1 expression in the large-scale regulatory network is controlled by a combination of four feedback loops, including a large loop, which has not been focused on. The model extracted by our method has the potential to reveal the critical mechanisms of neural differentiation. The method is applicable to other biological events.

Download Full-text

Finding the VOICE: organic carbon isotope chemostratigraphy of Late Jurassic – Early Cretaceous Arctic Canada

Geological Magazine ◽

10.1017/s0016756819001316 ◽

2019 ◽

Vol 157 (10) ◽

pp. 1643-1657 ◽

Cited By ~ 2

Author(s):

Jennifer M. Galloway ◽

Madeleine L. Vickers ◽

Gregory D. Price ◽

Terence Poulton ◽

Stephen E. Grasby ◽

...

Keyword(s):

Organic Carbon ◽

Carbon Isotope ◽

High Latitude ◽

Large Scale ◽

The Arctic ◽

Sudden Increase ◽

Arctic Canada ◽

Contributing Factors ◽

Compositional Evolution ◽

Sverdrup Basin

AbstractA new carbon isotope record for two high-latitude sedimentary successions that span the Jurassic–Cretaceous boundary interval in the Sverdrup Basin of Arctic Canada is presented. This study, combined with other published Arctic data, shows a large negative isotopic excursion of organic carbon (δ13Corg) of 4‰ (V-PDB) and to a minimum of −30.7‰ in the probable middle Volgian Stage. This is followed by a return to less negative values of c. −27‰. A smaller positive excursion in the Valanginian Stage of c. 2‰, reaching maximum values of −24.6‰, is related to the Weissert Event. The Volgian isotopic trends are consistent with other high-latitude records but do not appear in δ13Ccarb records of Tethyan Tithonian strata. In the absence of any obvious definitive cause for the depleted δ13Corg anomaly, we suggest several possible contributing factors. The Sverdrup Basin and other Arctic areas may have experienced compositional evolution away from open-marine δ13C values during the Volgian Age due to low global or large-scale regional sea levels, and later become effectively coupled to global oceans by Valanginian time when sea level rose. A geologically sudden increase in volcanism may have caused the large negative δ13Corg values seen in the Arctic Volgian records but the lack of precise geochronological age control for the Jurassic–Cretaceous boundary precludes direct comparison with potentially coincident events, such as the Shatsky Rise. This study offers improved correlation constraints and a refined C-isotope curve for the Boreal region throughout latest Jurassic and earliest Cretaceous time.

Download Full-text

Statistical study of high-latitude plasma flow during magnetospheric substorms

Annales Geophysicae ◽

10.5194/angeo-22-3607-2004 ◽

2004 ◽

Vol 22 (10) ◽

pp. 3607-3624 ◽

Cited By ~ 41

Author(s):

G. Provan ◽

M. Lester ◽

S. B. Mende ◽

S. E. Milan

Keyword(s):

Plasma Flow ◽

Growth Phase ◽

High Latitude ◽

Large Scale ◽

Flow Region ◽

Substorm Onset ◽

Return Flow ◽

Polar Cap ◽

Magnetospheric Substorms ◽

Superposed Epoch Analysis

Abstract. We have utilised the near-global imaging capabilities of the Northern Hemisphere SuperDARN radars, to perform a statistical superposed epoch analysis of high-latitude plasma flows during magnetospheric substorms. The study involved 67 substorms, identified using the IMAGE FUV space-borne auroral imager. A substorm co-ordinate system was developed, centred on the magnetic local time and magnetic latitude of substorm onset determined from the auroral images. The plasma flow vectors from all 67 intervals were combined, creating global statistical plasma flow patterns and backscatter occurrence statistics during the substorm growth and expansion phases. The commencement of the substorm growth phase was clearly observed in the radar data 18-20min before substorm onset, with an increase in the anti-sunward component of the plasma velocity flowing across dawn sector of the polar cap and a peak in the dawn-to-dusk transpolar voltage. Nightside backscatter moved to lower latitudes as the growth phase progressed. At substorm onset a flow suppression region was observed on the nightside, with fast flows surrounding the suppressed flow region. The dawn-to-dusk transpolar voltage increased from ~40kV just before substorm onset to ~75kV 12min after onset. The low-latitude return flow started to increase at substorm onset and continued to increase until 8min after onset. The velocity flowing across the polar-cap peaked 12-14min after onset. This increase in the flux of the polar cap and the excitation of large-scale plasma flow occurred even though the IMF Bz component was increasing (becoming less negative) during most of this time. This study is the first to statistically prove that nightside reconnection creates magnetic flux and excites high-latitude plasma flow in a similar way to dayside reconnection and that dayside and nightside reconnection, are two separate time-dependent processes.

Download Full-text