Wall Conditions Research Articles

Air contamination and its effect on deuterium desorption in liquid lithium

The clean wall condition in tokamak devices can be achieved by utilizing the active chemical property of lithium (Li). This also exposes Li to air contamination even when protected by inert gas. To determine whether air contamination affects the retention of hydrogen isotopes in Li, the desorption performances of deuterium (D2) in liquid Li with D/Li ratios of 4.1 mol.%, 2.5 mol.%, and 0.6 mol.% were compared. At a D/Li ratio as low as 0.6 mol.%, the results revealed a significant change in the desorption temperature of D2 by Li contaminants. The ratio of contaminants to D2 in Li was discovered to be important. In this regard, the influence of N2, O2, and H2O (accounting for 15 mol.% of D2) on the desorption performance of D2 in liquid Li was discussed. Both H2O and N2 preabsorbed in liquid Li could react with D2, leading to the changed desorption temperature of D2. Notably, the H2O present in Li consumed all of D2 via reaction, whereas the same amount of N2 as H2O could only react with a part of D2. However, the effect of O2 on the desorption temperature and the effect of impurities on the desorption amount of D2 were not obvious. The impacts of the findings of this work on the retention and extraction of hydrogen isotopes in Li may be further explored to prompt the application of Li in fusion devices.

Heat transfer analysis of the baking system for EAST

Before long-pulse plasma operation, wall conditioning is addressed as a key element to achieve steady state long-pulse operation with high performance, which is one of the major challenges for EAST (Experimental Advanced Superconducting Tokamak). The vacuum vessel and in-vessel components are continuously heated with hot nitrogen for a few weeks, namely the baking process, and the beginning of wall conditioning. It is difficult to accurately predict the specific temperature distribution of the baking system in the baking process under the current analysis and experimental conditions. Therefore, a simplified calculation model has been established in this paper, which is helpful to reveal the dynamic response mechanism and the heat loss to guide the input power of the baking system. The heat transfer relationship has been given by the theoretical method, and the calculation results of two cases are obtained by using Matlab/Simulink. The results gained by the heat transfer model were compared with the actual experimental data, which verified the correctness of the model. This heat transfer calculation model can be used in the future EAST experiment to predict the baking system operation behavior.

Wall conditioning effects and boron migration during boron powder injection in ASDEX Upgrade

The efficacy of boron powder injection as a wall conditioning tool method in terms of its ability to create a sufficiently uniform boron layer on plasma-facing surfaces has been studied in ASDEX Upgrade. Boron powder was injected in two series of dedicated plasma discharges at varied injection rates and total amount injected. The resulting boron deposition was determined quantitatively by exposure of witness samples followed by ex-situ surface analysis of the retrieved samples. In both experiments, isotopically enriched boron was used to distinguish the deposition of the newly injected material from the residual boron fraction in the machine originating from previous glow discharge boronisations. It could be confirmed that the injected boron is migrating and re-deposited across plasma-facing wall surfaces already within one discharge. At erosion dominated divertor areas, the boron influx from the main chamber results in formation of a mixed tungsten-boron surface layer with a boron area density of O(1nm) whereas at deposition dominated areas closed boron layers grow with ongoing boron injection to a thickness of up to O(1μm). Extrapolating the radial boron deposition profile on the samples exposed in the main chamber to the limiter front yields a similar boron coverage of O(1μm), which is about ten times higher than typical values for glow discharge boronisation. Together with the observed reduction of oxygen level and improved wall pumping, the surface analysis results demonstrate that boron powder injection provides a suitable means to refresh the wall conditioning effect of a preceding glow discharge boronisation.

First feedback-controlled divertor detachment in W7-X: Experience from TDU operation and prospects for operation with actively cooled divertor

In the last experimental campaign (OP1.2b) of the stellarator Wendelstein 7-X (W7-X), boronisation as a mean for first wall conditioning was applied for the first time which led to strongly reduced impurity fluxes from plasma-facing components. Thermal detachment at the uncooled target plates of the test divertor unit (TDU) was reached at higher plasma densities and was accompanied by high recycling of neutrals at the target plate (Feng et al., 2021), (Jakubowski et al., 2021) [1] . A feedback control system was established in W7-X to actively control the gas injection (actuator) for plasma fuelling and impurity seeding (Effenberg et al., 2019) [2] through the divertors. It allowed very successful stabilisation of the detached plasma condition state as well as mitigation of thermal overloads to some baffle tiles. Different routinely available diagnostic signals were used as input parameters (sensors). We describe the setup of the feedback control system, its performance and provide some example results with the main focus on the development of the control scheme which led to the detachment stabilisation over the entire longest (30 s) high-power discharge at W7-X so far. In view of the achieved very successful detachment stabilisation and the necessity to include simultaneous optimisation of the core performance in the future, the feedback control system is being upgraded for the upcoming campaign (OP2.1) in which the water cooled and hereby inherently steady-state capable divertor has been currently installed. The prospects and some experiment ideas for active detachment control are discussed.

Active wall conditioning through boron powder injection compatible ELM control in EAST

Active wall conditioning through boron powder injection compatible ELM control in EAST

Evaluating the length, diameter, and stenosis of deep circumflex iliac artery and neighboring arteries based on digital subtraction angiography.

The vascularized iliac bone crest flap offers excellent usable bone in terms of volume and quality. Its nourishing vessel, the deep circumflex iliac artery (DCIA), although relatively short, is reliable vessel. Digital subtraction angiography presents still the gold standard for diagnostic purpose. However, computed tomography (CT) and magnetic resonance imaging (MRI) angiography is used for preoperative planning with low morbidity. The purpose of this study is to evaluate the gainable information using digital subtraction angiography (DSA) as compared to other imaging modalities. We evaluated information gainable from standard DSA of 130 consecutive patients (average age was 69.5 years [range 18-90 years]) concerning topography, dimension, and condition of the vessel wall. We looked for differences considering gender and side. DCIA could not be followed in the periphery constantly in all cases due to the small, illustrated field. Arteriosclerotic changes showed to be very low in DCIA as compared to the neighboring vessels. Diabetes mellitus and smoking had a significant impact on vessel condition. DCIA branched off into its main two branches early after 40 mm (11%), after 40-60 mm (30%), or late after 60 mm (59%). DCIA showed to be least affected by different risk factors that reported to affect the vessel condition. We present additional detailed topographic anatomy of DCIA and its variation that can be used intraoperative guide to harvest the flap and teaching purpose. Standard DSA delivers valuable preoperative data regarding stenosis in addition to the topographic anatomy of the flap pedicle. However, imaging of the distal parts of the DCIA, nourishing the skin paddle is limited by the detector field used. For a full imaging of both DCIAs from the origin to the perforators, the intraarterial injection of contrast medium, as applied in DSA, could be combined with different imaging modalities like CT-angiography.

Recognition of Damage Types of Chinese Gray-Brick Ancient Buildings Based on Machine Learning—Taking the Macau World Heritage Buffer Zone as an Example

As a result of environmental and human influences, several types of surface deterioration emerge on historic buildings, resulting in a decline in the quality of these structures and even threats to their safety. In the conventional approach, assessing the surface damage on a structure involves the time-consuming and labor-intensive judgment and evaluation of trained professionals. In this study, it is suggested that the YOLOv4 machine learning model be used to automatically find five types of damage to historical gray-brick buildings. This would make the job go more quickly. This study uses the gray-brick wall buildings in the buffer zone of the global cultural heritage in Macau as an example. In total, 1355 photographs were taken on-site of the gray-brick walls, and the five most common types of damage were identified. By slicing and labeling the photos, a training set of 1000 images was created, and through 200-generation model training, the model can accurately identify and effectively identify the damage state of the gray bricks and enhance the quality judgment and evaluation of the exterior walls of historical buildings. Experiments allow us to reach the following conclusions: (1) The damage to the gray-brick ancient buildings in Macau is affected by the subtropical maritime climate. Missing paint, stains, and cracks are the main contributors to gray-brick wall damage. (2) Machine learning can help determine the type of damage to old gray-brick buildings, which is useful for managing and protecting historical buildings. (3) The model in this study can identify five types of damage: missing, cracking, plant or microbial erosion, yellowing, and pollution on the exterior walls of ancient gray-brick buildings. It is helpful to accurately identify and evaluate the damaged condition of the gray-brick wall and formulate corresponding protection schemes.

Particle transport in a turbulent pipe flow: direct numerical simulations, phenomenological modelling and physical mechanisms

In particle-laden turbulent wall flows, transport of particles towards solid walls is phenomenologically thought to be governed by the wall-normal turbulence intensity supporting the underlying particle–eddy interactions that are usually modelled by a combination of turbophoresis and turbulent diffusion. We estimate the turbophoretic and turbulent diffusive coefficients as a function of wall-normal coordinate directly from a generated direct numerical simulation (DNS) database of low volume fraction point particles in a turbulent pipe flow. These coefficients are then used in an advection–diffusion equation to estimate the particle concentration as a function of wall-normal distance and time, with favourable comparison against DNS for smaller Stokes number ( $St^+$ ) particles suggesting a limitation of the common gradient diffusion hypothesis for larger $St^+$ particles. Using DNS we explore the non-trivial effects of $St^+$ , pipe wall condition (particle absorbing or elastic) as well as the influence of drag and lift force on the velocity and particle statistics giving rise to different particle concentrations. We then appraise various Eulerian-based models of turbophoretic and turbulent diffusive coefficients and, finally, use physical insights from Lagrangian correlation times, conditional quadrant analysis and flow topology to shed further light on the particle transport as a function of various parameters and the limits of gradient diffusion hypothesis.

Analysis of heat transfer phenomenon in hydromagnetic micropolar nanoliquid over a vertical stretching material featuring convective and isothermal heating conditions

This article evaluates the heat transfer mechanism in an incompressible hydromagnetic micropolar nanofluid enclosed in a two-dimensional vertically stretchable material surface in a porous device. In the current study, the developed model features the significant contributions of nonlinear radiative flux, viscous dissipation, Brownian movement together with thermophoresis effects in the transport region. An approach of similarity transformations is employed to transmute the transport equations from partial into ordinary differential equations. The translated equations are then integrated numerically via Runge–Kutta Fehlberg scheme plus shooting technique. From the analysis, it is found that there is an improvement in the mechanism of heat transfer for large magnitude of temperature ratio and radiation parameters due to the application of Convective Heating Condition (CHC) whereas the case of Isothermal Wall Condition (IWC) reveals an opposite direction for these parameters. Besides, an improvement in the magnitudes of the material micropolar term, Eckert number together with thermophoresis and Brownian movement parameters creates a decline in the surface heat transfer for both heating conditions.

Effects of thermal boundary conditions on the performance of spray dryers

In this paper, three kinds of wall conditions are numerically simulated to investigate deposition, powder recovery and energy aspects of spray dryers. A co-current dryer with a pressure nozzle is chosen as a base dryer and two dryers with fully insulated, and cooled walls are compared with the base one. Governing equations of a transient flow field are solved through the Eulerian approach, while Lagrangian particle tracking predicts particles’ motion. The sticky point curve is employed as a criterion of bouncing or stickiness to model the deposition pattern of skim milk particles on the surfaces. Results show that the spray dryer with cooled walls has better deposition characteristics, while the dryer with insulated surfaces works with higher drying efficiency. Overall, it is observed that the wall conditions can be changed to improve the drying efficiency and wall deposition. However, changing the thermal boundary conditions does not seem to be effective in improving the powder recovery. • The performance of dryers was investigated in three different dryers. • The sticky point curve was considered on the walls. • Maximum powder recovery obtained in the base dryer. • Significant deposition reduction observed in the cooled-walls dryer.

Finite element analysis of bending waves in Mindlin plates with Perfectly Matched Layers

It is important to determine the boundary conditions of walls and floors precisely when simulating the building acoustics. For a certain room, the extension of the spans can be considered as infinite edges. The Perfect Matched Layer(PML) is an artificial absorbing domain for the wave propagations and is widely used in finite element analysis to simulate the acoustical free field conditions right now. In this paper, an effective PML technique for the plate structure will be presented. The PML formulation will be derived based on the Mindlin plate theory and the implementation method will be introduced. This technique will be validated through the numerical experiments. The accuracy and limits of the presented technique will be discussed based on the numerical results compared with the analytical results. The results show that the presented PML technique is effective and accurate to simulate the plate as an infinite large plate. It is expected to implement the technique in the further research of the structure borne sound, such as floor impact sounds.

MEPhIST-0 Tokamak for Education and Research

An overview of the MEPhIST-0 educational and research small-scale spherical tokamak project is presented including the vacuum vessel, magnetic field systems, and diagnostics. In contrast to other small machines, it is an advanced tokamak with D-shaped plasma equipped with an electron-cyclotron resonance pre-ionization system for plasma startup and an ion-cyclotron resonance system for plasma heating and wall conditioning. The design choices taken are discussed from the perspective of a primarily educational installation. The machine design is simplified while remaining relevant to larger devices. First plasma results obtained in 2021 are presented.

Resistance risk assessment of Fusarium pseudograminearum from wheat to prothioconazole

Fusarium crown rot (FCR), primarily caused by Fusarium pseudograminearum, poses significant threats to cereal crops worldwide. Prothioconazole is a demethylation inhibitor (DMI) fungicide used to control FCR. However, the risk of resistance in F. pseudograminearum to prothioconazole has not yet been evaluated. In this study, the sensitivity of a total of 255 F. pseudograminearum strains obtained from Henan Province, China to prothioconazole were determined by the mycelial growth inhibition. The results showed that the effective concentration to 50% growth inhibition (EC50) of these strains ranged from 0.4228 μg/mL to 2.5284 μg/mL, with a mean EC50 value of 1.0692 ± 0.4527 μg/mL (mean ± SD). Thirty prothioconazole-resistant mutants were obtained out of six selected sensitive parental strains by means of fungicide taming. The resistant mutants exhibited defects in vegetative growth, conidia production, and pathogenicity on wheat seedlings compared to their parental strains. Under ion, cell wall, and temperature stress conditions but not osmotic stress, all the mutants exhibited decreased growth rates compared with their parental strains, which was consistent with the control treatment. Cross-resistance test showed that there was a cross-resistance relationship between prothioconazole and four DMI fungicides, including prochloraz, metconazole, tebuconazole and hexaconazole, but no cross-resistance was observed between prothioconazole and carbendazim, phenamacril, fludioxonil, or azoxystrobin. Although no site mutation occurred on Cyp51a and Cyp51b genes, the constitutive expression level of the Cyp51a gene was significantly increased in all mutants. After being treated with prothioconazole, the Cyp51a and Cyp51b genes were significantly increased in both the resistant mutants and their parents. These results suggested that the resistance to prothioconazole of the mutants may be attributed to the changes of the relative expression level of Cyp51a and Cyp51b genes. Taken together, these results could provide a theoretical basis for the scientific use of prothioconazole in the field and fungicide resistance management strategies.

Freezing process of nanomaterial inside thermal storage tank with amelioration in geometry utilizing Galerkin modeling

In the current attempt, the numerical technique (Galerkin method) has been implemented to scrutinize the solidification within the sustainable energy unit involving elliptic and sigma shaped cylinders. The domain is full of water and due to the cold condition of complex walls, the liquid water converts to solid and the rate of process was enhanced with addition alumina nanomaterial. The concentration and shapes of additives have been assumed as variables in this study. Mesh has been adopted with a position of solid front and validation test proved the correctness of modeling. The period for water is 1.36 times superior than that of NEPCM. The required time changes form 1144.04 s to 837.44 s with loading nanoparticles. As particles with greater shape factor have been utilized, the needed time declines around 6.98 %.

Study on flow and heat transfer characteristics of 3D molten aluminum droplet printing process

The molten metal droplet printing technology can effectively realize a precise preparation of complex electronic devices at the micro scale by relying on the metallurgical bonding among the tiny molten metal droplets, which can improve the metallographic structure and mechanical properties of the fabricated parts. In this paper, the interaction process between metal droplets and movable substrates during the preparation of electronic devices is studied based on the coupled level set volume of fluid method (CLSVOF) and equivalent heat capacity method. The influence of the micro-bubbles and wall infiltration characteristics on the impingement spreading flow of metal droplets and their heat transfer cooling process is also investigated. The evolution mechanisms of droplet geometry and the distribution characteristics of droplet internal temperature and heat flow density during the impingement spreading process are discussed. The mechanism of high-temperature region formation under superhydrophobic wall conditions is analyzed. Results show that the microbubbles inhibit the spread of molten metal droplet. Under the same conditions, the spreading radius of hollow metal droplet is smaller than that of solid droplet, and their spreading height is higher than that of solid droplet. Different wall infiltration characteristics have similar degrees of influence on the spread of solid and hollow droplets. A larger wall contact angle for the same impingement mode at the same moment corresponds to a smaller droplet spreading radius and the higher the spreading height. With the participation of microbubbles, the heat transfer cooling process inside metal droplet becomes slow and demonstrates a less uniform temperature and heat flow density distribution. A high-temperature region is easily formed inside droplet under superlyophobic wall conditions, which triggers an uneven heat transfer cooling process at the bottom of the droplet. The results benefit to reveal the law of metal microdroplet impingement molding on different working surfaces and provide a theoretical reference for the preparation of electronics-related devices.

Numerical Study of Mixed Convection and Heat Transfer in Arc-Shaped Cavity with Inner Heat Sources

The mixed convection and heat transfer in enclosures with inner heat sources widely exist in building ventilation, cooling of nuclear reactors and cooling of electronic components. In this study, the heat transfer characteristics of mixed convection in an open arc-shaped cavity with double heat sources under the condition of bottom heating and top wall cooling are studied by two-dimensional numerical simulation using ANSYS FLUENT. The influence of the Reynolds number on flow structures, transient characteristics and heat transfer characteristics in the arc cavity was studied by changing inlet wind speed. As the Reynolds number changes from 2.19 × 105 to 4.38 × 107, the flow in the fully developed stage will evolve from turbulent flow to periodic flow and then to steady state flow. In this study, the critical Reynolds number intervals for three different flow states are given. The increase in the Reynolds number enhances the heat convection in the cavity. The difference between heat convection and heat conduction is increased, which has a linear relationship with the Reynolds number. As the Reynolds number increases, the heat removal capacity in the middle region of the double heat sources is not always enhanced, which is due to the sudden change in flow structure and flow state around Re = 1.18 × 107.

Nano-ferrofluid (Mn–Zn, CoFe2O4, Fe3O4) flow in a permeable channel with induced magnetic field

This article deals with the magnetohydrodynamics (MHD) transportation of water-based nano-ferrofluid in a channel. Three different types of ferrofluid suspensions, to be specific, water-containing magnetite, cobalt ferrite, and manganese-zinc ferro particles (, , ) are taken to observe flow field, induced magnetic field, and temperature field. The non-dimensional mathematical model is solved numerically under the specified wall and free stream conditions. The key parameters emerging in the present model are Prandtl number, porosity, the reciprocal of magnetic Prandtl number and magnetic parameter. The impact of these parameters on the flow field, velocity, temperature, and gradient of magnetic stream function for various ferrofluid suspensions is discussed graphically. Altogether, a more prominent velocity of fluid is noticed for magnetite ferro particles as contrasted with cobalt or manganese-zinc ferro particles due to the lower density of magnetite ferro particles. It is observed that when the volume fraction of nanoparticle rises from 0.1 to 0.6, heat transfer at the lower wall of channel is increased by 11 and decreased by 36 at the upper wall of the channel.

Experimental, numerical and theoretical study on heat transfer in paper honeycomb structure

The fabrication of most current thermal insulation materials from polymeric foams has created an unfavorable impact on the environment. With the aim of reducing the use of foam plastic, this paper focuses on honeycomb paperboard, an alternative thermal insulation material which is recyclable and cost-effective, and evaluates its heat transfer performance under different conditions. The experimental results show the effective thermal conductivity of honeycomb paperboard increases as the honeycomb height or the side length increases. This paper also establishes a novel theoretical model based on a newly developed convective heat transfer correlation to predict the effective thermal conductivity under different conditions. The model's results conform well to the experimental results, and the effect of convective heat transfer is investigated quantitatively using this model. As the vertical adiabatic boundary surfaces are replaced by honeycomb walls, the convection heat transfer strictly depends on the thermal boundary condition of the honeycomb walls and highly depends on honeycomb height and side length.

Realization of T e0 > 10 keV long pulse operation over 100 s on EAST

In 2021, EAST realized a steady-state long pulse with a duration over 100 s and a core electron temperature over 10 keV. This is an integrated operation that resolves several key issues, including active control of wall conditioning, long-lasting fully noninductive current and divertor heat/particle flux. The fully noninductive current is driven by pure radio frequency (RF) waves with a lower hybrid current drive power of 2.5 MW and electron cyclotron resonance heating of 1.4 MW. This is an excellent experimental platform on the timescale of hundreds of seconds for studying multiscale instabilities, electron-dominant transport and particle recycling (plasma-wall interactions) under weak collisionality.

Thoracic cavity remodeling and pulmonary function change after chest wall resection.

Chest wall resection (CWR) is an essential procedure for treating malignancies and infectious conditions of the chest wall. However, there are few studies on the pulmonary function and changes in thoracic cavity volume (TCV) related to CWR. This study aims to investigate the effects of CWR on long-term changes in TCV and pulmonary function. Data of patients who underwent CWR between 2001 and 2021 were retrospectively reviewed. Patients who underwent single rib or lung resection rather than wedge resection were excluded. TCV (liter) was defined as the sum of the right and left TCVs (RCV and LCV) and was measured using computed tomography image reconstruction software. Changes in pulmonary function and TCV 1 year postoperatively were analyzed. A total of 45 patients were included. The number of resected ribs was 2 in 16 (35.6%) and ≥3 in 29 (64.4%) patients. Thirty patients underwent reconstruction. Long-term post-CWR decreased in forced vital capacity (FVC) (-7.9%, P=0.004) and forced expiratory volume in 1 second (FEV1) (-7.0%, P=0.002) were significant. There was no significant decrease in FEV1/FVC ratio (-3.0%, P=0.06), diffusing capacity of the lung for carbon monoxide (DLCO) (-5.9%, P=0.18) and TCV (-3.1%, P=0.10). There was no correlation between changes in TCV and decreases in FVC (r=0.12, P=0.56) or FEV1 (r=0.15, P=0.45). After right-side CWR (n=27), RCV (-7.8%, P=0.01) decreased significantly, whereas LCV (+2.1%, P=0.58) did not. The left-side CWR exhibited an identical pattern. (LCV: -8.5%, P=0.004; RCV: +1.3%, P=0.85). In the ≥3 rib-resection group, FVC (-9.5%, P=0.02), FEV1 (-7.9%, P=0.02) and TCV (-6.4%, P=0.04) decreased significantly. No significant changes were noted in the 2 rib-resection group. There were no significant differences in the changes in pulmonary function nor TCV between the reconstruction and no-reconstruction groups. The long-term decrease in pulmonary function after CWR was significant, especially after ≥3-rib resection.