Power Decay Research Articles

Type-I ELM power loads on the closed outer divertor targets in the HL-2A tokamak

The HL-2A tokamak has a very closed divertor geometry, and a new infrared camera has been installed for high resolution studies of edge-localized mode (ELM) heat load onto the outer divertor targets. The characteristics of power deposition patterns on the lower outer divertor target plates during ELMs are systematically analysed with infrared thermography. The ELM energy loss is in the range of 3%–8% of the total plasma stored energy. The peak heat flux on the outer divertor targets during ELMs currently achieved in HL-2A is about 1.5–3.2 MW m−2, the wetted area is about 0.5–0.7 m2, and the corresponding integrated power decay length at the midplane is about 25–40 mm. The rise time of the ELM power deposition is in the range of about 100 μs to 400 μs, and the decay time is typically 1.5 to 4 times longer than the corresponding rise time. Convective transport along open field lines during the ELM rise phase from the midplane towards the divertor targets is implied due to the correlation of parallel transport time in the scrape-off layer (SOL) and ELM power rise time. The peak ELM energy fluence is compared with those predicted by models and with experimental data from JET, ASDEX Upgrade, MAST, and COMPASS. The results, as a whole, show a good agreement.

Aeolian sand transport over a wet, sandy beach

• Substantial transport occurs below Belly’s (1964) fluid threshold. • Particles in transport exhibit high moisture contents. • Vertical flux profiles deviate from those observed over dry beds. • Transport flux models predict motion below the fluid threshold for wet beds. Quantifying aeolian transport within the intertidal zone is critical to understanding feedbacks between aeolian and nearshore processes in coastal environments. Here, we report a field study of aeolian transport over a wet bed in the intertidal zone. Predominate winds and beach orientation were aligned during all field observations. Mean grain size of bed samples were 0.18 mm and moisture content ranged from 16 to 17%. Velocity profiles were measured with a vertical array of cup anemometers. Sustained wind velocities were 9.5 m/s at 93 cm above the bed with gusts reaching 13.5 m/s. Five saltation traps captured particles in transport from the bed to a height of 15 cm. Particles in transport were wet and the highest moisture content of trapped sediments was found in the lowest saltation trap. Vertical flux profiles show a higher concentration of flux closer to the bed (81 to 89% below 5 cm) than those measured over dry beds. Power and exponential decay functions were fit to our vertical flux profiles; the exponential decay function best fit flux profiles with larger β coefficients and smaller α estimates than those fit to dry bed profiles. Total flux models predict transport below Belly’s (1964) fluid threshold of motion for moist beds and model performance improves when using a threshold for dry sand. Our results suggest transport over wet beds is fundamentally different from transport over dry beds. However, more research is needed to discern the mechanics driving deviations in flux profiles over wet beds in field environments.

Exponential distribution of velocities and power distribution of quiescent periods in the spontaneous movement patterns of three hunting spiders

Abstract Here, we investigate the spontaneous locomotor patterns in three spiders with different hunting strategies. The locomotor activity of adult wolf spiders Pardosa amentata, with a sit-and-move hunting strategy, has previously been demonstrated to follow strictly mathematical rules, with most time spent at lower velocities and exponentially decreasing time spent at increasing velocities. Likewise, they have an abundance of short quiescent (resting) periods following a power decay function towards longer quiescent periods. In the present study, we explored whether similar distributions were expressed in juveniles of P. amentata and in two other spider species with different hunting strategies: the sit-and-wait spider Xysticus cristatus and the actively searching sac spider Clubiona phragmitis. We found that all three spider species followed the same two general rules of movement. However, there were differences among the three species. On a logarithmic scale of exponential velocities and a double-logarithmic scale of the rest power decay function, the slopes of the lines for the three species differed. We propose that these differences reflect the behavioural and locomotor differences of the three hunting strategies. Furthermore, we compare our results with similar movement distributions in single cells, fruit flies, mice and even humans.

Comparative analysis of the efficiency of manual adjustable pitch propeller and fixed pitch propeller based on dual-scale coupling

In order to solve the problem of ship, engine, and propeller mismatch between the first manufacturing of a new type of ship and the long-term service of the ship, the idea of dual-scale coupling simulation is used to establish the meso-scale and macro-scale mathematical model of a manually adjustable pitch propeller. The thrust coefficient and the torque coefficient are the coupling points. A comparison calculation between the manual adjustable pitch propeller and the fixed pitch propeller is carried out on a small ship as an example. The results show that the manual adjustable pitch propeller could compensate for the efficiency deviation caused by the fixed pitch propeller design; When the ship’s resistance increases or the ship’s main engine power decays, the measures of adjusting the pitch and turning angle of the blades could effectively improve the efficiency of the propeller and the ship’s speed, which indicates that the manual adjustable propeller has better adaptability than the fixed pitch propeller.

Laser Spot Micro-Welding of Ultra-Thin Steel Sheet.

This paper reports a mechanism understanding how to reduce the solder joint failure phenomenon in the laser spot micro-welding process of ultra-thin steel sheets. An optimization method to improve solder joint service life is proposed. In this study, the time-dependent dynamic behaviors of the keyhole and the weld pool are simulated, and the temperatures in the keyhole of two different laser pulse waveforms are compared. The results show that laser energy attenuation mode (LEAM) can only obtain shallow weld depth because of the premature decay of the laser power of waveform, resulting in the laser beam that cannot be concentrated in the keyhole. The temperature inside the keyhole of LEAM fluctuates significantly, which shows a downward trend. Due to the existence of the peak power of waveform in laser energy continuous mode (LECM), the large angle of inclination of the wall of the keyhole inside the melt pool is more conducive to the multiple reflections of the laser beam in the keyhole and increases the absorption rate of the laser energy by the base material, resulting in the “keyhole effect”. But the temperature in the keyhole gradually rises, close to the evaporation temperature. A method combining LEAM and LECM to improve the solder joint service life by optimizing the temperature in the keyhole indirectly by adjusting the peak power of the laser pulse waveform is proposed in this study. The experimental results show that the weld depth can be optimized from 0.135 mm to 0.291 mm, and the tensile strength can be optimized from 88 MPa to 288 MPa. The bonding performance between the upper and lower plates is effectively improved. It can reach the required weld depth in a short time and improve the welding efficiency of the laser spot micro-welding process. The simulation results show that the temperature inside the keyhole is well optimized below the evaporation temperature of the material, which can avoid the violent evaporation of the welding process and keep the whole welding process in a stable state. By optimizing the laser pulse waveform, the temperature inside the keyhole can reach 3300 K, and it is always in a stable state than before optimization. The stable temperature inside the keyhole can help to reduce violent oscillation and spattering of the molten pool and improve welding efficiency and joint life. The research can help provide effective process guidance for the optimization of different laser pulse waveforms in the micro-welding process.

Process-oriented estimation of column-integrated algal biomass in eutrophic lakes by MODIS/Aqua

Algal blooms happen widely in eutrophic lakes. The satellite-derived surface algal bloom area and chlorophyll-a (Chl-a) concentration are commonly used as indicators to judge the water quality. However, vertical migration of phytoplankton may seriously affect the assessment accuracy of water quality with the surface status as an indicator. In fact, the water column-integrated algal biomass is better for describing the water quality. To remotely estimate the algal biomass considering the vertical Chl-a profile (uniform or otherwise), this paper proposed a novel process-oriented algorithm applied successfully in Lake Chaohu, China. First, we built a decision tree to identify the pixel-based Chl-a profile types using the floating algae index, surface Chl-a concentration, and wind speed. Then, the nonuniform profile was expressed as a power decay function (Chl-a(z)=n1×zn2) and parameterized using the surface Chl-a concentration. Finally, the algal biomass was derived from MODIS/Aqua satellite data. The estimation results were acceptable and the bias was −19.95%. The monthly mean algal biomass varied significantly and exhibited two peaks in spring and summer. The annual mean algal biomass increased from 2003 to 2010 (Pearson r = 0.82; p < 0.05) and then decreased from 2012 to 2018 (r = −0.71; p = 0.07). Monthly variations were determined by the air temperature (77.09%), but annual variations were primarily influenced by ammonia nitrogen level (44.61%). With known algal biomass and wind speed, the pixel-based algal bloom probability could be forecasted. The developed process-oriented algorithm was also applicable to eutrophic Lake Taihu, China. This study is of great significance for scientifically assessing water quality and effectively managing aquatic environmental disasters.

On two extensions of the canonical Feller\u2013Spitzer distribution

We introduce two extensions of the canonical Feller–Spitzer distribution from the class of Bessel densities, which comprise two distinct stochastically decreasing one-parameter families of positive absolutely continuous infinitely divisible distributions with monotone densities, whose upper tails exhibit a power decay. The densities of the members of the first class are expressed in terms of the modified Bessel function of the first kind, whereas the members of the second class have the densities of their Lévy measure given by virtue of the same function. The Laplace transforms for both these families possess closed–form representations in terms of specific hypergeometric functions. We obtain the explicit expressions by virtue of the particular parameter value for the moments of the distributions considered and establish the monotonicity of the mean, variance, skewness and excess kurtosis within the families. We derive numerous properties of members of these classes by employing both new and previously known properties of the special functions involved and determine the variance function for the natural exponential family generated by a member of the second class.

Asymmetric vortex sheet

We present a steady analytical solution of the incompressible Navier–Stokes equation for arbitrary viscosity in an arbitrary dimension d of space. It represents a d − 1 dimensional vortex “sheet” with an asymmetric profile of vorticity as a function of the normal coordinate z. This profile is related to the Hermite polynomials Hμ(z), which are analytically continued to the negative fractional index μ=−dd−1. In d = 2 dimensions, the solution degenerates to a constant vorticity flow. In d≥3 dimensions, the vorticity is confined to the thin layer around the hyperplane with Gaussian decay on one side of the hyperplane and the power decay on another side. One can adjust the common scale of velocity so that the dissipation will stay finite at vanishing viscosity. In this limit, the width w of the viscous lawyer will shrink to zero as ν35 for arbitrary dimension d &amp;gt;3. In d = 3 dimensions, this power law is also accompanied by powers of the logarithm.

Calculation and Analysis of Critical Heat Flux at LWR Passive Safety Design

Critical heat flux (MDNBR) is one parameter for safe nuclear reactor operation. The magnitude of MDNBR is determined by local heat flux. When it is sufficiently high, it will cause a change in heat equilibrium and deteriorate nuclear fuel structure. To obtain assurance for nuclear reactor safety in safe criteria, Calculation and analysis of Critical heat flux of 630 MWe passive LWR was carried out at steady state and transient condition. The study used COBRA IV-I sub channel program coupled with critical heat flux correlation of EPRI-Columbia and W-3. The program models the core into 1/8 sections, each of which is divided into 83 sub-channels in radial direction and 40 nodes in axial direction, including 8 sub-channels of the hottest assembly. Normalized coast down flow and reactor power decay at initial phase is 10 second after loss of flow accident (LOFA) caused by anticipated primary pump failure. The effects of all input parameters, such as radial nodes, axial nodes, mix coefficient, velocity of coolant mass entering the core and power variation, have been identified. Evaluation of the results of safety calculation indicates that MDNBR, cladding temperature, and hot channel temperature are 1.83, 349°C and 2033°C, respectively. As the licensing limits for those parameters are 1.3, 1850°C, and 2840°C, it is concluded that the design of 630 MWe passive LWR has met the licensing criteria of safety. Modelling for safety analysis of passive LWR employs COBRA IV-I program. The results show that this program can be used to calculate hydraulic safety parameters with sub-channel model.

Development of megawatt radiofrequency ion source for the neutral beam injector on HL-2A tokamak

A radiofrequency (RF) ion source with a megawatt power extraction, thunder I, has been developed for the neutral beam injector (NBI) on HL-2A tokamak. A full solid-state RF generator with output power of 80 kW and frequency of 2 MHz was built by an RF combiner using 8 modules of solid-state RF generator with power of P RF = 10 kW. The line electric efficiency of whole RF generator reaches 92% and its voltage standing wave ratio (VSWR) is 1.01, thus no water-cooling system is supplied. A quartz vessel with the inner diameter of 250 mm is directly adopted for resisting atmospheric pressure, which can dramatically simplify source structure. Nowadays, the extracted beam parameters of RF hydrogen ion source are 32 kV/20 A/0.1 s on a test bed, while the design parameters are 50 kV/20 A/3 s. The beam density profile measured by the infrared imaging technique at 1.3 m downstream from the grounded grid obeys a Gaussian distribution, and the corresponding half width of 1/e power decay at the matched condition is about 80 mm. Plasma homogeneity is over 90% at low RF power. The beam divergence angle meets the requirement of NBI system on HL-2A tokamak. The extractable current density increases almost linearly with the RF power. It reaches 2400 A m−2 at P RF = 32 kW. The ion density in front of plasma grid is about 1 × 1018 m−3, corresponding to an ionized fraction of about 1% at the gas pressure of 0.5 Pa. Single hydrogen ion fraction reaches 79% at the beam current of 12.4 A. Some improvements have been considered for optimizing ion source performance on next experimental campaign. One smaller auxiliary RF discharge chamber equipped with a gas feed path, driven by 13.56 MHz/3.5 kW generator, is connected to main discharge chamber driven by 2 MHz/40 kW generator. By this dual-driven configuration, the innovative RF plasma source with high-pressure density gradient solves the initial ignition problem of powerful RF ion source even if the gas pressure below 0.1 Pa. In addition, the RF negative hydrogen ion source of 200 kV/20 A/3600 s is also developed at SWIP for the China fusion engineering test reactor.

Travelling wave solutions on a non-zero background for the generalized Korteweg–de Vries equation

For the generalized p-power Korteweg–de Vries equation, all non-periodic travelling wave solutions with non-zero boundary conditions are explicitly classified for all integer powers p ⩾ 1. These solutions are shown to consist of: bright solitary waves and static humps on a non-zero background for odd p; dark solitary waves on a non-zero background and kink (shock) waves for even p in the defocusing case; pairs of bright/dark solitary waves on a non-zero background, and also bright and dark heavy-tail waves (with power decay) on a non-zero background, for even p in the focussing case. An explicit physical parameterization is given for each type of solution in terms of the wave speed c, background size b, and wave height/depth h. The allowed kinematic region for existence of the solutions is derived, and other main kinematic features are discussed. Analytical formulas are presented in the higher power cases p = 3, 4, which are compared to the integrable cases p = 1, 2.

Towards assessment of plasma edge transport in Neon seeded plasmas in disconnected double null configuration in EAST with SOLPS-ITER

Energy dissipation in the plasma edge is key for future tokamaks. The potential of neon as radiating seeding species in disconnected double null (DDN) configuration is assessed in EAST discharges in high confinement mode (H-mode). As the separation between the two separatrices in the studied DDN discharges is minimum 1.5 cm, the configuration is effectively a single null configuration, and the benefits of the double null topology are minimal. Neon seeding, on the other hand, has a favourable effect: both the target heat flux and the divertor temperature decrease more than five-fold with increased seeding rate in high-recycling conditions. Interpretive edge plasma simulations with SOLPS-ITER in support of ongoing transport analysis are presented. For the unseeded case the numerical results agree with the experimental data within a factor two for the target temperature conditions and measured neutral pressures in the active divertor. The key for achieving good agreement is a suitable selection of coefficients for anomalous transport and neutral conductances between the upper cryopump and the main chamber. • Neon was used to increase the level of dissipation in the EAST low-field side upper divertor • Due to Neon, a high-recycling regime was established • A full detached regime was not achieved due to the limitations on input power. • No clear advantages of DDN configuration were observed as the minimal dr sep was larger than the power decay length. • SOLPS-ITER simulations are set up to study performed discharges.

Empirically constrained network models for contrast-dependent modulation of gamma rhythm in V1

Gamma oscillations are thought to play a key role in neuronal network function and neuronal communication, yet the underlying generating mechanisms have not been fully elucidated to date. At least partly, this may be due to the fact that even in simple network models of interconnected inhibitory (I) and excitatory (E) neurons, many parameters remain unknown and are set based on practical considerations or by convention. Here, we mitigate this problem by requiring PING (Pyramidal Interneuron Network Gamma) models to simultaneously satisfy a broad set of criteria for realistic behaviour based on empirical data spanning both the single unit (spikes) and local population (LFP) levels while unknown parameters are varied. By doing so, we were able to constrain the parameter ranges and select empirically valid models. The derived model constraints implied weak rather than strong PING as the generating mechanism for gamma, connectivity between E and I neurons within specific bounds, and variations of the external input to E but not I neurons. Constrained models showed valid behaviours, including gamma frequency increases with contrast and power saturation or decay at high contrasts. Using an empirically-validated model we studied the route to gamma instability at high contrasts. This involved increased heterogeneity of E neurons with increasing input triggering a breakdown of I neuron pacemaker function. Further, we illustrate the model's capacity to resolve disputes in the literature concerning gamma oscillation properties and GABA conductance proxies. We propose that the models derived in our study will be useful for other modelling studies, and that our approach to the empirical constraining of PING models can be expanded when richer empirical datasets become available. As local gamma networks are the building blocks of larger networks that aim to understand complex cognition through their interactions, there is considerable value in improving our models of these building blocks.

Study of novel high-density solar panels based on small space interconnection technology

Small space interconnection technology (SSIT) has been utilized in solar panels recently. The application of this technology can further increase the module efficiency. However, higher power decay after long-time operation may occur due to additional risk. Therefore, in this paper, damp heat (DH), thermal cycle (TC), UV irradiation and humidity freezing (HF) tests were utilized to study the weatherability performance of SSIT-based high-density solar panels fabricated with cells cut by two different techniques. The achieved data suggest that the novel high-density modules with small space between cells have good reliability in various weather conditions. The novel low-damage laser-induced cutting technique is beneficial for the improvement of module reliability.

Intelligent Indoor Positioning Based on Artificial Neural Networks

LBS has become an integral part of people's life nowadays. However, the GPS restricted by the shielding effect is unavailable for indoor environments. Therefore, accurately locating an electronic device indoors has become a challenging issue in recent years. This work employs the CSi combined with neural networks to achieve an accurate indoor positioning. The CSi refers to known channel properties of a communication link in wireless communications. This information describes how a signal propagates from the transmitter to the receiver and represents the combined effects of, for example, scattering, fading, and power decay with distance. This work will evaluate several neural networks for the positioning, including the FCNN, CNN, and GCNN. in multi-carrier communication systems, the CSi of adjacent subcarriers has a high correlation, and hence, the CNN is promising to learn and extract the features of this input information corresponding to the location of radio devices. Beyond that, we also investigate an improved CNN, that is, the GCNN, which has more talent to locate in indoor environments than traditional CNNs. Experimental results show that the proposed GCNN can achieve a root-mean-square error (RMSE) of less than 0.08m and 0.3m for 16 and two antennas, respectively. in addition, the computational complexities and required numbers of parameters of compared deep neural networks have been analyzed as well.

Glomalin contribution to soil organic carbon under different pasture managements in a saline soil environment

ABSTRACT The glomalin produced by arbuscular mycorrhizal fungi has beneficial effects on soils. We studied the vertical profile of glomalin-related soil protein (GRSP) in pasturelands grown under saline soils and exposed to different management practices. Treatments included haying and grazing of Chloris gayana subject to either N-fertilization or not. We measured mycorrhizal colonization, spores, root biomass, total GRSP, GRSP-carbon (GRSP-C), organic carbon (OC) and total nitrogen (TN). In the meanwhile, we also developed a mathematical procedure to fit continuous power functions to binned soil data. Power decay functions adjusted excellently well the measured data across the 1-meter soil profile. Meaningful increases of root biomass, OC, TN, GRSP and GRSP-C values were associated with grazing and fertilization. Particularly, GRSP-C averaged 1,134 kg C ha−1 at the beginning experiments and increased significantly up to 1,261 kg C ha−1 in grazed and fertilized pastures at the end of the study period. Carbon accounted for between 17% and 50% of GRSP, representing in turn 0.52–1.62% of SOC stock. So, a tropical perennial grass can contribute to the carbon stock in saline soils by promoting production of GRSP. This contribution increases when inputs and cycling of nutrients are enhanced (grazing and N-fertilization).

Revolution and revitalization: Karoline von Günderrode’s political philosophy and its metaphysical foundations

ABSTRACT This paper adds to efforts to retrieve the long-neglected philosophical contributions of Karoline von Günderrode (1780–1806), and is one of the first to seriously address the political commitments in Günderrode’s work, especially regarding revolution. This idea gains an unusual status in the context of Günderrode’s metaphysics, and is key to understanding the connections between Günderrode’s more obviously philosophical writings and her literary work. I argue that Günderrode’s concept of revolution resembles, in some respects, the ideas of other thinkers of her time, but has ramifications for conceiving of human individuals and their relationships to society and nature that are unique to Günderrode. First, I use a comparison with the work of contemporaries on revolution to justify interpreting Günderrode’s metaphysics in relation to her thought on politics. Günderrode often masks her political thought in the form of plays, and the paper next considers the theme of revolution in her plays Muhammad, the Prophet of Mecca, and Udohla. Lastly, the paper contrasts Günderrode’s position on revolution to claims by Herder and Fichte, arguing that Günderrode’s conception of a cycle of enhancement and decay of natural forces, political power and social cohesion differs from androcentric models that emphasize the development of consciousness.

Fourier transform of self-affine measures

Suppose F is a self-affine set on Rd, d≥2, which is not a singleton, associated to affine contractions fj=Aj+bj, Aj∈GL(d,R), bj∈Rd, j∈A, for some finite A. We prove that if the group Γ generated by the matrices Aj, j∈A, forms a proximal and totally irreducible subgroup of GL(d,R), then any self-affine measure μ=∑pjfjμ, ∑pj=1, 0<pj<1, j∈A, on F is a Rajchman measure: the Fourier transform μˆ(ξ)→0 as |ξ|→∞. As an application this shows that self-affine sets with proximal and totally irreducible linear parts are sets of rectangular multiplicity for multiple trigonometric series. Moreover, if the Zariski closure of Γ is connected real split Lie group in the Zariski topology, then μˆ(ξ) has a power decay at infinity. Hence μ is Lp improving for all 1<p<∞ and F has positive Fourier dimension. In dimension d=2,3 the irreducibility of Γ and non-compactness of the image of Γ in PGL(d,R) is enough for power decay of μˆ. The proof is based on quantitative renewal theorems for random walks on the sphere Sd−1.

Understanding baffle overloads observed in high-mirror configuration on Wendelstein 7-X

The operational regimes in the first divertor campaign of W7-X were limited by unexpectedly high heat loads on certain baffle tiles. In the high-mirror configuration, a permanent hotspot on the baffle plate was detected by the thermographic system, which was further confirmed during the post-campaign inspections of the plasma-facing components. The maximum heat load on three baffle tiles reached about 4.5 MW m−2, which was almost an order of magnitude above its designed value of 0.5 MW m−2. The paper presents a detailed analysis to understand how the baffle plate, which is originally designed to screen the recycling neutrals and is therefore hidden from the hot plasma, can receive such a high heat load - a level that is expected for target plates. Three main causes have been identified: 1) the three baffle tiles are radially only about 5 mm away from a main heat channel towards a target, which is much shorter than the radial power decay length of several centimeters derived from the thermographic measurements in this region; 2) the three baffle tiles are intersected with field-lines of about 30 m length, which are long enough to collect considerable amount of heat via cross-field transport; 3) the baffle tiles have locally large grazing angles. In addition, the analysis method shown in this paper is of general use to estimate the heat flows in shadow areas of targets and thus to evaluate heat loads on the potentially critical components occurring in these areas, especially required for the design of complex 3D divertors like the one in W7-X.

Microstructures of high-strength steel welding consumables from directed thermal cycles by shaped laser pulses

Filler wire metallurgy was modified through temporally shaped laser pulses, controlling cooling cycles in a recently developed method. Trends were identified through efficient mapping while maintaining representative thermal cycles of welding processes. A primary pulse melted preplaced filler wires while a secondary, linearly ramped-down pulse elevated the nugget to re-austenization temperatures. Ramped-down pulses resulted in linear cooling rates comparable with and exceeding furnace-based methods, between 50 and 300∘C/s. The linear decay of laser output power guided the temperature through a regime to obtain desired microstructures. For three very high-strength steel filler wire chemistries, quenching resulted in smaller plates with cross-hatched microstructures, accompanied by grain boundary ferrite. Finer bainite microstructures started forming for fast linear temperature decay, about 250∘C/s. Slower decay or a weaker third cycle formed coarser microstructures with coalescent sheaves and less cross-hatching.