Resistive Wall Research Articles

Models and scalings for the disruption forces in tokamaks

The study is devoted to theoretical analysis of some models for calculating the disruption forces in tokamaks and scalings for these forces which can be proposed for ITER. It is motivated by the necessity of reliable predictions for ITER. The task includes the evaluation of the existing models, resolution of the conflicts between them, elimination of contradictions by proper improvements, elaboration of recommendations for dedicated studies. Better qualities of the modelling and higher accuracy are the ultimate theoretical goals. In recent years, there was a steady progress in developing a physics basis for calculating the forces, which gave rise to new trends and ideas. It was discovered, in particular, that the wall resistivity, penetration of the magnetic perturbation through the wall, the poloidal current induced in the wall, the kink-mode coupling, plasma position in the vacuum vessel must be the elements essentially affecting the disruption forces. These and related predictions along with earlier less sophisticated concepts and results are analysed here.

A Study on Computational Analysis for Natural Convection in Tall Building – A Macroscopic Approach

The development of convective heat transfer in buildings are found to be due to the movement of air with respect to the turbulence in air to the temperature. The heat transferred is observed in 3 levels ‐ the roof exposed floor, the seventh floor and the lower floor of the 14 storey naturally ventilated tall building. This paper discusses the eulerian approach which is a macroscopic approach to understand the temperature in the building since the density stratification occurs in the indoor volume of the building. The volume averaged data is considered to be in eularian approach. The CFD analysis is used to artificially create the environment with the different temperatures and velocities. Heat transfer happens due to convection, hence the boundary conditions ‐ initial outdoor temperature has been kept constant at 30°C and 23°C. The change in the outdoor temperature at the air velocities 10 m/sec at 12 noon were observed as 29.37°C, 29.49°C, 29.89°C at constant temperature 30 with respect to 1st floor, 7th floor and roof. Finally, it is noted that, as the air velocity increases, the outdoor temperature also increases. Conjugate heat transfer analysis is followed in CFD analysis to include the resistance of the exterior concrete wall to transfer the temperature to the control volume. K‐omega model is used to resolve the turbulence and to analyse the interior domain with Boussinesq hypothesis in the momentum equation to include the effect of the density difference in heat transfer. It is observed the velocity helps to take the temperature from the exterior domain to the interior part of the building. Hence the results clearly indicate that when the outdoor temperature is higher and the outdoor velocity is also higher, the temperature which enters the indoor environment is also high.

Photothermal-healing, and record thermal stability and fire safety black phosphorus–boron hybrid nanocomposites: mechanism of phosphorus fixation effects and charring inspired by cell walls

Inspired by the structure and good thermal resistance of cell walls in plants, we herein develop a life-cycle safe multifunctional nanocomposite of PC/BP–B, achieving record fire safety and thermal stability via phosphorus fixation effects.

Determination of the stress-strain relationship as a function of temperature for the design of AAC masonry panels subject to fire according to Eurocodes

At the current status, the European Standard provides only tabulated data as a reliable method to assess the structural fire resistance of masonry walls. In the version in force, Annex C and D are mostly considered not reliable for design since an adequate validation by experimental results is missing. For this reason, this paper proposes an advance of the input parameters adopted by the models for the thermo-mechanical response of AAC. In addition, new stress-strain curves as a function of temperature are then proposed and compared with the stress-strain curves currently available in the Annex D of the European Standard. The comparison of results points out that the current curves do not fit properly to the behaviour of AAC masonry in a range of temperatures equal to 500°C-700°C.

Effect of confluence length on the heat transport capability of ultra-thin multiport minichannel thermosyphon

Effect of confluence lengths (Colen = 0 mm, 5 mm and 10 mm), heat loads (10–90 W), filling ratios (FR = 40% to 60%) and inclination angles (IA = 30°, 45°, 60° and 90°) on the heat transport capability of a multiport minichannel (MPMC) thermosyphon with hydraulic diameter of 1.18 mm and having Acetone as the working fluid is experimentally investigated. Enhancement of 33% in the heat transport capability (up to 90 W) was observed for MPMC thermosyphon with optimum Colen = 5 mm, whereas it was only 60 W at Colen = 0 mm. Reduction of 42.4% and 18.3% in thermal resistance (Rt) and evaporator wall temperature (Te,w) and enhancement of 19.5% in evaporator heat transfer coefficient (heva) are respectively observed for MPMC thermosyphon with optimum Colen = 5 mm and inclination angle (IA = 90°) when compared with Colen = 0 mm. Combination of reduced entrainment effect causing faster circulation of working fluid at optimum Colen, surface tension effect which pulls the bulk condensate to the corners and the thin film at flat sides of multiports are found to be the major reasons for enhancement in the heat transport capability of MPMC thermosyphon.

Metallurgical Processing for Impregnated Thermionic Cathodes Manufacturing

A metallurgical process using a very high temperature Mo-Ru brazing filler alloy to join a controlled porous tungsten cathode button and a single-crystalline molybdenum cathode body for microwave tubes manufacture was developed†. The Mo-Ru brazing alloy was obtained by mixing and milling powders in the eutectic composition with a binder, and a braze paste was applied on the surface cathode parts. Brazing was performed in two temperatures by using a resistive dry hydrogen cold wall furnace for 10 minutes: at 1890 °C and 1967 °C. It was observed a fillability by the Mo-Ru system only in the tests performed in temperatures above 1967°C. The brazed samples were analyzed by Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy. It was observed absence of microstructural defects in the interface between the tungsten porous and dense molybdenum joint. Stress-strain tests, followed by SEM analysis were performed to determine the mechanical behavior of the brazing joining. The results indicate the origin region of the cracking and show an intergranular propagation; some evidence as grain cleavage indicates a brittle failure behavior.

Формування оптимальних енергетичних та теплотехнічних характеристик огороджувальних конструкцій будівель

The purpose of the work is to study of options for thermal modernization of enclosing structures with a justification of the optimal composition of energy-saving measures to achieve maximum energy efficiency of buildings. Ukraine's energy balance shows that more than 30% of the total energy is consumed by the residential sector, of which up to 80% goes to heating. This is due to the low level of energy efficiency of the enclosing structures of residential buildings, as well as the unsatisfactory technical condition of utilities, due to physical wear and tear and obsolescence. The peculiarities of the influence of the type of thermal insulation materials and their characteristics on the thermal and energy performance of the building are investigated. It was found that the increase in the density of insulation affects the thermal resistance of walls in different ways - the density of mineral wool and extruded polystyrene have the opposite effect of foamed polystyrene, ie insulation of mineral wool or extruded polystyrene should be chosen with the lowest density Element-by-element analysis of the components of enclosing structures proved that their impact differs significantly, in the case of separate implementation of measures can reduce heat consumption by 0.07… 23%, and the priority is to modernize the walls of building facades (provided that the glazing ratio K ≤ 0 , 25). Measures of complex thermal modernization of enclosing structures are substantiated by the method of expert assessments according to technical-energy, financial and ecological criteria. Calculations confirm that the complex thermal modernization will reduce the value of specific energy consumption and specific greenhouse gas emissions by 1.5 times, specific heat consumption - by 1.9 times, increase the energy efficiency class of the building from G to D. It is shown that the normative values of heat transfer resistances of external enclosing structures will provide only the class D energy efficiency of the building. It is not possible to achieve the recommended class "C" and higher by further increasing the thermal resistance of the enclosing structures - it is necessary to modernize the engineering systems of the building.

Fracture resistance of thin wall endodontically treated teeth without ferrules restored with various techniques.

To evaluate the fracture resistance and failure characteristics of simulated thin wall endodontically treated teeth without ferrules restored with various techniques. Forty-eight human mandibular single-root canal premolars were decoronated and endodontically treated. The 1 mm thick remaining root canal dentin was prepared. The roots were randomly divided into four groups of 12 roots according to the following post and core reconstruction techniques: direct resin composite post and core (CP), multiple fiber posts and resin composite core (FP), CAD/CAM anatomical post and core (AP), and metal cast post and core (MP). Full metal crowns were cemented to the cores. All specimens were subjected to thermocycling for 5000 cycles and submitted to axial compression until failure at a 45°angle using a universal testing machine. The failures were classified into one of the followings: post and/or core fractures, root fractures, and root fractures combined with post and/or core fractures. Average failure loads of groups CP, FP, AP, and MP were 360.0, 655.2, 402.7, and 856.1N, respectively. MP provided the highest failure load, which was significantly higher than those of the other groups (p < 0.05). FP was second, being inferior to MP with a significance level of p=0.039. CP exhibited the least failure load, and it was not significantly different from the AP group (p > 0.05). Root fractures were the major failure mode for most of the specimens except the CP group, in which composite fractures at the cervical level were commonly observed. Metal cast post and core provided the highest fracture resistance for reconstruction of a thin wall in endodontically treated teeth without ferrules, followed by multiple fiber posts and resin composite core. The milled anatomical post and core and a direct resin composite post and core provided significantly lower fracture resistance. Metal cast posts and core and multiple fiber posts with resin composite core techniques were effective for restoring severely compromised endodontically treated teeth.

Investigation of a new kind of in-situ measurement method of thermal resistance of building envelope

Accurate and effective in-situ measurements of the thermal performance of the building envelope are important for determining the energy use and thermal comfort of buildings. This study proposes a new method, i.e. removing the heat storage effect and heat flow meter method (RHS-HFM) that can eliminate the effects of thermal inertia. And verifies its feasibility by means of the temperature-controlled box method (TCB-HFM) and in-situ measurements of the thermal resistance of walls under four different conditions. The measurement results show that the new method gives reasonable results compared with the TCB-HFM, with a deviation of only 6%; moreover, the error between the thermal resistance obtained with the new method and the design value is only about 7% under any test conditions, it is a good proof of the reliability of the method and its ability to overcome seasonal limitations. It can also be found that the RHS-HFM can effectively shorten about 24 h test period, the new method can greatly improve the measurement efficiency compared to the heat flow meter method. In addition, to further investigate the applicability of the RHS-HFM, the effect of air conditioning is also analyzed in this paper. In summary, the new method proposed in this study can effectively solve the problems of poor accuracy, seasonal limitations and long test cycles in the heat flow meter method, and can provide a better research basis for related studies.

Crack resistance of masonry walls

Computer models used in the design calculation of masonry buildings sometimes fail to correctly take into account the stress-strain state of walls and assess the likelihood of cracks caused by the deformation differences of interacting walls.Following the construction of a building, cracks can develop at wall intersections for several years. However, their repair is mostly ineffective until the total damping of masonry creep deformation.Drawing on the analysis of conducted research and field data, the authors give recommendations on ensuring the crack resistance of internal masonry walls.

A pressure drop prediction model for hydrate slurry based on energy dissipation under turbulent flow condition

In the development of natural gas hydrates (NGHs) in deep-water environment, gas hydrates will form in the water-drainage line of the wellbore due to low-temperature and high-pressure environment. The flow pattern in the water drainage line is hydrate slurry bubbly flow (HSBF). Thinking that no proper model has been built yet, a novel model is proposed for predicting the pressure drop of HSBF based on the energy dissipation theory. The model considers the influences of the wall resistance, the collision of hydrate particles, the collision of hydrate particle-pipe wall and the friction of carry liquid-hydrate particle on the energy dissipation caused by hydrate slurry flowing. The wall resistance and the collision of hydrate particles are main reasons inducing the pressure drop during hydrate slurry flowing under turbulent flow, which their contributions to the total energy dissipations are from 49% to 64% and from 35% to 49% correspondingly with hydrate concentrations increasing. The sum of energy dissipations for the other two factors are only within 1.35%. The reliability of the proposed model is validated by the published data. Most of discrepancies are within ±10% and all discrepancies are less than ±20%.

Differential diagnosis of changes in the area of the large duodenal nipple in postcholecystectomy syndrome by the method of parietal impedancemetry

Purpose of the study. To carry out differential diagnostics of organic and functional changes in the area of the large duodenal papilla (LDP) by the method of parietal impedancemetry in patients with PCES.&#x0D; Materials and methods. Duodenoscopy with parietal impedance LDP was performed in 47 patients. A history of 38 patients underwent laparoscopic cholecystectomy, and 9 patients underwent laparotomic cholecystectomy. In 31 patients, the study was performed against the background of signs of obstructive jaundice, in 16 – the study was performed against the background of dilatation of the common bile duct without visualization of calculi in it. All patients underwent endoscopic retrograde cholangiopancreatography with determination of parietal impedance prior to endoscopic papillosphincterotomy. The control group consisted of 8 patients without manifestations of PCES, who underwent duodenoscopy with parietal impedancemetry during a routine examination.&#x0D; Results. The parameters of the parietal impedance of patients with PCES against the background of benign obstructive jaundice in the presence of papillitis were 605–703 Ohm. In the absence of visual signs of inflammation, the resistance of the LDP wall varied within 760–820 Ohm and coincided with the values of the control group.&#x0D; Conclusion. Parietal impedancemetry is an informative method for detecting inflammatory changes in the LDP, which can be performed routinely during duodenoscopy and allows differential diagnosis between the organic pathology of the LDP zone and its absence.

Shielding Effectiveness and Impact Resistance of Concrete Walls Strengthened by High-Strength High-Ductility Concrete.

Following the fourth Industrial Revolution, electronic and data-based technology is becoming increasingly developed. However, current research on enhancing electromagnetic interference (EMI) shielding and the physical protection performance of structures incorporating these technologies is insufficient. Therefore, in this study aiming for the improvement of EMI shielding and structural performance of structures, twelve concrete walls were fabricated and tested to determine their shielding effectiveness and drop-weight impact resistance. Concrete walls strengthened by three thickness types of high-strength, high-ductility concrete (HSDC) have been considered. The test results showed that the shielding effectiveness with strengthening thickness increased by approximately 35.6–46.2%. Specimens strengthened by more than 40% and 10% of the strengthening area ratio of single- and double-layer, respectively, exhibited more than 20 dB of shielding effectiveness. Moreover, the relationship between the damaged area ratio and shielding effectiveness was evaluated by means of the drop-weight impact test. The structural performance and EMI shielding effectiveness improved as the HSDC thickness increased.

Controlling base movement of MSE walls using recycled plastic pins

Sliding failure of Mechanically Stabilized Earth (MSE) retaining walls is a common problem when the shearing resistance developed between the wall base and foundation soil is insufficient. Highway MSE wall base failures can cause significant maintenance, repair, and cost implications for the state department of transportation. Controlling base movement using Recycled Plastic Pins (RPP) can be a potentially cost-effective and sustainable solution. RPPs are primarily manufactured from recycled plastics and have been successfully used for stabilizing shallow slope failures. The objective of the current study is to demonstrate the effectiveness of using RPPs for increasing the sliding resistance of an MSE wall. Four field test sections were constructed, out of which three were reinforced with different combinations of RPP sizes and spacings, while one was left unreinforced as a control section. Regular performance monitoring of the test sections was conducted using vertical inclinometers along with earth pressure plates. More than a year of results indicated a 75–88% reduction in lateral displacement of the reinforced wall base when compared with the control section. Additionally, the lateral earth pressure on the wall facing was decreased by 55–72% in the reinforced sections compared to the control section.

Spin transfer torque bias (STTB) due to domain wall resistance in an infinitely long ferromagnetic nanowire

The shift of a magnetization loop along the magnetic field axis for a ferromagnetic (FM)/anti-ferromagnetic (AFM) system when it is cooled through Néel temperature of AFM layer is called exchange anisotropy or exchange bias. Here, using micromagnetic simulations we propose that spin transfer torque (STT) mechanism would indeed be helpful in realizing the shift of the magnetization loop along magnetic field axis through domain wall (DW) resistance for an infinitely long FM nanowire without having AFM layer, which we call as spin transfer torque bias (STTB). Essentially, STTB is realized on both positive and negative magnetic field axes by varying the angle between spin polarized current and Zeeman field from 0° to 180° respectively and the origin is attributed to helical motion of the DW. However, we do not see STTB at 90° due to coherent rotation of domain. We also ascertain that STTB is also a function of magnetic anisotropy, current density, polarization strength and non-adiabatic STT term. Variation in STTB for different FM systems such as Fe2CoSi, Ni80Fe20 and Fe is attributed to a change in DW width. We believe that present results would lead to a new dimension in the field of spintronics.

Impact response and endurance of unreinforced masonry walls strengthened with cement-based composites

Unreinforced Masonry (URM) walls are construction elements that have been found to resist in-plane forces, which proved beneficial for wind and earthquake resistant design. The out-of-plane resistance of URM walls, however, is very minimal, if any. Strengthening the walls in the out-of-plane direction is an ongoing research topic. This study aims at conducting laboratory experiments on the impact resistance of strengthened and unstrengthened URM walls. Impact tests are carried out to measure the failure resistance of structural members to suddenly applied load. The developed strengthening techniques consist of the application of fiber reinforcement cement-based composites using shotcrete technology. Two types of fibers are considered, polypropylene macro-fibers for FRC (Fiber Reinforced Concrete) and polyethylene micro-fibers for the ECC (Engineered Cementitious Composites). The FRC mixes were prepared with two dosage rates of polypropylene fibers (4.6 and 6 kg/m3) while the ECC, one dosage of polyethylene fibers (16 kg/m3) was used. A total of 12 URM walls were constructed with precast reinforced concrete frame and then infilled with hollow concrete blocks. The walls were strengthened and then tested under drop weight with a mass of 52 kg from a height of 3.8 m resulting in a kinetic energy of about 2000 J. Multiple drops were performed on each wall until failure. Test results revealed that the walls strengthened with the ECC Shotcrete (ECCS) endured ten drops, the largest number, without visible failure. The FRC Shotcrete (FRS) with 6 kg/m3 fibers ranked as the second-best strengthening technique; the FRS-6 walls endured more than six drops without major failure. In addition, the performance of each wall is evaluated in terms of endurance, impact force, energy absorption, flexural stiffness, and impact duration.

OPTIMIZATION OF HEAT PROTECTION CHARACTERISTICS OF COUNTRY COTTAGE ENCLOSURES

The article presents a method for determining the minimum permissible value of the heat transfer resistance of the outer wall, at which the minimum energy consumption is achieved during the operation of buildings with variable thermal conditions. A review of the sources devoted to this problem showed the presence of high costs of thermal energy during the heating of premises. On the basis of studies of all components of energy consumption in the operation of premises with intermitt ent heating systems, the authors of the article propose a method for determining the minimum permissible resistance to heat transfer, which provides minimum energy consumption. According to the described method, the calculation was made for external walls made of various materials. The analysis of the obtained results showed that a signifi cant infl uence on the minimum permissible value of the heat transfer resistance is exerted by a complex of thermophysical values cρλ. The presented graphical dependence R0 усл on the complex cρλ allows the designer to rationally choose a wall material that provides a minimum of energy consumption during the operation of the building. In the context of rising energy tariff s, such optimization of thermal protection characteristics is especially important for country cott ages operated in intermitt ent heating conditions.

Capillary Endothelial Insulin Transport: The Rate-limiting Step for Insulin-stimulated Glucose Uptake.

The rate-limiting step for skeletal muscle glucose uptake is transport from microcirculation to muscle interstitium. Capillary endothelium poses a barrier that delays the onset of muscle insulin action. Defining physiological barriers that control insulin access to interstitial space is difficult because of technical challenges that confront study of microscopic events in an integrated physiological system. Two physiological variables determine muscle insulin access. These are the number of perfused capillaries and the permeability of capillary walls to insulin. Disease states associated with capillary rarefaction are closely linked to insulin resistance. Insulin permeability through highly resistant capillary walls of muscle poses a significant barrier to insulin access. Insulin may traverse the endothelium through narrow intercellular junctions or vesicular trafficking across the endothelial cell. Insulin is large compared with intercellular junctions, making this an unlikely route. Transport by endothelial vesicular trafficking is likely the primary route of transit. Studies in vivo show movement of insulin is not insulin receptor dependent. This aligns with single-cell transcriptomics that show the insulin receptor is not expressed in muscle capillaries. Work in cultured endothelial cell lines suggest that insulin receptor activation is necessary for endothelial insulin transit. Controversies remain in the understanding of transendothelial insulin transit to muscle. These controversies closely align with experimental approaches. Control of circulating insulin accessibility to skeletal muscle is an area that remains ripe for discovery. Factors that impede insulin access to muscle may contribute to disease and factors that accelerate access may be of therapeutic value for insulin resistance.

Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls.

Identification of the actual thermal properties of the partitions of building enclosures has a significant meaning in determining the actual energy consumption in buildings and in their thermal comfort parameters. In this context, the total thermal resistance of the exterior walls (and therefore their thermal transmittance) in the building is a major factor which influences its heat losses. There are many methods to determine the total thermal resistance of existing walls, including the quantitative thermography method (also used in this study). This paper presents a comparison of the calculated total thermal resistance values and the measured ones for three kinds of masonry walls without thermal insulation and the same walls insulated with expanded polystyrene boards. The measurements were carried out in quasi-stationary conditions in climate chambers. The following three test methods were used: the temperature-based method (TBM), the heat flow meter method (HFM) and the infrared thermography method (ITM). The measurement results have been found to be in good agreement with the theoretically calculated values: 61% of the measured values were within 10% difference from the mean value of total thermal resistance for a given external wall and 79% of the results were within 20% difference. All of the used measuring methods (TBM, HFM and ITM) have proven to be similarly approximate in obtained total thermal resistances, on average between 6% and 11% difference from the mean values. It has also been noted that, while performing measurements, close attention should be paid to certain aspects, because they can have a major influence on the quality of the result.

On the synergy manipulation between the activation temperature, surface resistance and secondary electron yield of NEG thin films

The operation of the modern accelerators has long been challenged with the problems associated with distributed vacuum profile and electron multipacting. Applying a Ti-Zr-V based non-evaporable getter (NEG) film provides an ideal solution to these problems, except that TiZrV thin film may deteriorate the wakefield effect because of the increased wall resistivity. To deal with the trade-offs between those effects, an innovative quaternary TiZrVCu NEG film was prepared using magnetron sputtering technique in the present study. Through comparative study on the activation behavior, secondary electron yields and the surface resistivity of the novel TiZrVCu getter film with that of the conventional TiZrV film, it is found that alloying Cu into the TiZrV film would encouragingly eliminate the secondary electron yield and the d.c. resistivity of the NEG films, with a minor deterioration on the activation kinetics. The present study provides insights for optimizing the composition of NEG films from the aspect of realizing synergy manipulation of the activation kinetics, SEY and d.c resistivity.