Uniformity Degree Research Articles

Research on the Arrangement Scheme of Spirally Twisted Tape Inserts in a Grate Furnace

To eliminate the flow dead zone and homogenize the asymmetric flow field of a grate furnace, spirally twisted tape inserts (STTIs) with a pitch ratio of 1.5 were installed in the vertical flues of an SCL1000-13.5/450 grate boiler. The arrangement schemes found to be present inside the chosen 1000 t/d grate furnace, determined using the orthogonal experimental method, included separate installation in chamber II, separate placement in chamber III, and simultaneous arrangement in both chamber II and chamber III. The effects of row spacing H, column spacing W, and mounting angle φ were investigated by means of the practicable and feasible numerical simulation method. With a focus on the uniformity degree of the flue gas, the results showed that temperature distribution is directly correlated with the velocity field. When it comes to the uniformity of the flow field, the exclusive use of STTIs in chamber II was better than that in chamber III. Under the optimal combination scheme of STTIs in both chamber II and chamber III (scheme N323), the exhaust gas temperature reached the minimum value and the uniformity index of temperature increased to the range of 0.994~0.997. The findings in this work could provide a reference for the optimization of the flow field in a grate furnace.

Improving plasma uniformity in the inductively coupled plasma by external magnetic field

To enhance etching efficiency and uniformity in process production, in this work, a two-dimensional fluid model was used to study the modulation effect of an external magnetic field on the argon–oxygen inductively coupled plasma (ICP). The study found that as the magnetic coil current increases, the electron density changes from center-high to uniform to edge-high distribution. The best plasma uniformity degree is 94%, obtained at a magnetic coil current of 10 A, which represents a 39% improvement over the unmagnetized ICP. The electric field reversal occurs during the transition from weak magnetization to strong magnetization. The electron temperature shows a single-peak to dual-peak to single-peak distribution during this period. In addition, we also found that gas pressure and oxygen ratio also impact magnetized plasma, where the effect of gas pressure on magnetized plasma is more significant than that of oxygen ratio. The results show that introducing an external magnetic field can significantly improve the plasma density and radial uniformity. This finding has contributed to enhancing plasma etching uniformity and optimizing etching processes.

Optimizing the Thickness Uniformity of Magnetron Sputtering Deposited Films on a Large-Scale Curved Workpiece Surface

This study prepared magnetron-sputtering deposition film on a large-scale curved workpiece with a favorable thickness uniformity using a rectangular target cathode. For a substrate rotation structure with eccentric rotation/revolution composite motion, the geometrical model of the thickness distribution of the coating film on a large substrate was established in combination with the principle of rectangular cathode magnetron sputtering. The integral formula of the film thickness was derived, and various film thickness distribution patterns under different parameters were simulated. According to the present research results, the film thickness distribution can be optimized by adjusting the revolution-to-rotation radius and eccentric ratios. At an eccentric distance of 400 mm and a radius ratio of 2.78, the most favorable uniformity degree of 0.87 was obtained, which was controlled by the motion path of the fixed point on the substrate. The proposed approach helps to obtain large-scale films with favorable uniformity on the substrate.

Study of the Grinding Process by Friction of Cereal Grains in Stone Mills

The grinding process via friction at the micro-scale in a mill with stones is considered a variable combination of contacts, with two-body (the asperities of lower millstone in direct contact with the asperities of upper millstone) and three-body (micro-particles of ground seeds trapped between the asperities of lower and upper stones of the mill) contacts. Three elements are described: (1) the mechanical contact of the asperities of the lower and upper millstones to predict pressures on asperities by modeling; (2) tests on a millstone sample covered with grinding particles; and (3) tests on a wafer sample formed by the millstones with the grinding particles between them. This paper highlights the combined effects of the micro-scale friction via individual measurements, using an analytical model to sum these effects and validating the model by performing several experiments. An efficiency grind by friction assumes the grain’s movement and interaction between the seeds and solid surfaces, and is highlighted through theoretical and experimental studies. Topography analysis of the surface of the millstones reveals the model of microscopic frictional force. Endpoint measurements (the traces of the surface topography evolution) enable model verification in the grinding process. Thus, the results obtained in the grinding process in the stone mills via friction have practical utility through research benefits. Therefore, they allow for the improvement of quality, reliability, flexible grinding, quality control of the flours, and uniformity degree (fineness/shredding).

Large-scale synthesis of two-dimensional indium telluride films for broadband photodetectors

2D III-VI semiconductors have emerged as promising materials for optoelectronic devices due to their tunable bandgaps, efficient light absorption and high carrier mobility. Among III-VI group, 2D indium telluride (InTe) has been studied very little compared with its well-known congeners such as InSe and GaSe. Although InTe possesses remarkable electrical and optical properties, the investigation of its device applications is greatly hindered due to the shortage of scalable synthesis method. Here, we synthesized centimeter-scale 2D InTe films via a pulsed laser deposition method. The structure of as-grown InTe films was systematically studied, exhibiting good continuity, uniformity and high degree of crystallinity. Meanwhile, layer-dependent bandgaps (1.21∼1.65 eV) were observed from the optical characterization. The InTe based photodetectors show a broadband photoresponse from ultraviolet (370 nm) to near-infrared region (980 nm). The photoresponsivity and detectivity of the InTe photodetectors can achieve 6.35 A/W and 1.55×1011 under 370 nm illumination, respectively, which outperform many photodetectors based on large-area 2D materials. Notably, InTe photodetectors also demonstrate strong layer-dependent photoresponse from 2 L to 10 L upon different wavelength illumination. Our work will inspire the research interests to further develop the practical applications of 2D InTe in the field of photodetection devices.

Broadband microwave absorption effects in 2D nitrogen capacitively coupled plasma under different operating conditions

In recent years, the interaction of electromagnetic waves (EM) with plasma sources under argon and helium discharges has been extensively studied due to its potential applications in plasma stealth. However, nitrogen, as a more economical discharge gas, has been ignored in terms of its absorption of EM waves and stealth effect. In this work, a numerical calculation model combining two-dimensional capacitively coupled plasma (CCP) fluid model and EM wave model was developed to investigate the plasma uniformity degree and broadband microwave absorption effects in helium and nitrogen CCP. It is concluded that the two-dimensional model in this paper has more accurate and reasonable through comparison with the one-dimensional and experimental results in helium CCP. Nitrogen CCP shows better broadband absorption effects than that of helium, and helium plasma has better uniformity than nitrogen under the same discharge parameters. But the uniformity degree of nitrogen plasma is not much different from that of helium under the same electron density, which means that nitrogen can significantly improve its broadband wave absorption properties to some extent without loss of uniformity degree. Based on the above conclusions, the absorption characteristics of nitrogen CCP under different radio frequency (RF) power and pressure are analyzed. The attenuation effect of nitrogen CCP increases with the increasing RF power, and it is interesting that the influence of pressure on the attenuation of EM waves is not monotonically increasing, and the related mechanism is discussed. Finally, discussion of skin depth under different RF power and pressure validates the above conclusions. The absorption band of nitrogen CCP under the best parameters in this work can reach the X-band, which shows great application potential in plasma stealth.

Investigation the Performance Accuracy of Contoured Dual Ring Double Scatterer System for Flat Beam Generation at Proton Therapy

At proton radiotherapy, the extracted beam from accelerator is not initially suitable for tumor treatment and a modification is needed for beam shape and energy due to tumor dimension and site. One clinical strategy is the use of double scattering systems known as passive dose delivery technique to generate proper flattening, transversely. This work aims to design and simulate a new version of double scattering system and compare its performance with another available scatterer system, quantitatively. In this analytical study, Monte Carlo FLUKA code is utilized to simulate the performance of proposed system in generating lateral flat beam. The simulation process is very close to real experimental condition, performed at proton beam irradiation room at Tohoku University in Japan. Moreover, the presence of secondary neutrons, produced due to protons collision with proposed scattering system, is considered as main issue. Final results represent that the proposed scattering system is robust to generate 40 mm flat region with an acceptable uniformity degree. Energy loss caused by current dual scatterer is more than simple ring technique, while the secondary neutrons produced by proposed system are larger than other system. This study simulates the performance of a new dual ring double scattering system. Final results show that there is a close correlation between proposed system and current scattering system. The only concern is about the presence of secondary neutrons mainly at high energy proton particles.

Influence of spatial distribution of fine sand layers on the mechanical behavior of coral reef sand

Fine coral sand commonly distributes in coral sand artificial foundation due to the effect of gravity sorting during hydraulic process and the particle breakage of coarse particle. Considering that the significant impact of the distribution form of fine sand on the strength and deformation properties of coral sand foundation, the effect of spatial distribution of fine sand layers on the mechanical behavior of coral sand was studied. The mechanical behavior of coral sand in the consolidated undrained (CU) shear tests were simulated by discrete element models (DEM) analysis method, and the impact mechanism of fine sand interlayers on mechanical strength was analyzed. The effect of thickness and number of fine sand interlayer on the mechanical behavior and shear deformation of coral sand specimens were analyzed based on the proposed uniformity degree, a parameter that quantify the spatial distribution of fine particle interlayers. The results show that the mechanical behavior of coral sand was simulated well by DEM based on particle scanning results. Under the condition of constant fine particle content, the average coordination number of particles increased and the minimum contact force between particles decreased when fine particles were distributed in the form of interlayer. It indicates that the fine particle interlayer has a diffusion effect on stress transfer, which revealed the mechanism of the macro increasing strength of 10%–20% under the same confining pressure. A linear relationship was found between the proposed parameter uniformity and the peak deviator stress of specimens, and the impact of uniformity on the strength was particularly significant under high confining pressures.

Experimental and numerical study of X-type energy dissipation device under impact loads

To obtain the optimal size and shape of X-type energy dissipation device, 20 specimens were tested using a drop hammer impact test machine, then the finite element model was established by using the software LS-DYNA. The dynamic responses of X-type energy dissipation device including failure mode, impact force, displacement and energy absorption were obtained and analyzed with emphasis on the effect of the height reduction parameter a, length reduction coefficient b and high span ratio c. The effectiveness of the finite element model is verified by comparing the simulation results with the experimental results. The finite element model is then used to optimize the X-type energy dissipation device. The height reduction parameter a and high span ratio c were taken as the optimization parameters, and the strain uniformity was taken as the target for improvement. Through regression analysis, the formulas of height reduction parameter a, height span ratio c and strain uniformity degree are derived. After four levels of optimizations, the optimized shape of the X-type energy dissipation device is obtained, and its energy dissipation performance is significantly improved compared with that of the traditional X-type energy dissipation device.

"The Influence of Uniformity Coefficient and Degree of Soil Saturation on the Injectability of Cement Suspensions - A Mini Review"

"The Influence of Uniformity Coefficient and Degree of Soil Saturation on the Injectability of Cement Suspensions - A Mini Review"

New Differentially 4-Uniform Piecewise Permutations over F22k from the Inverse Function

Permutations with low differential uniformity, high nonlinearity and high algebraic degree over F22k are preferred substitution boxes in modern block ciphers. In this paper, we study the bijectivity and the difference uniformity of piecewise function with the help of permutation group theory. Based on our results, We found many at least differentially 6-uniform and differentially 4-uniform permutations over F22k, which can be chosen as the substitution boxes.

Structural modifications of sinusoidal wavy minichannels cold plates applied in liquid cooling of lithium-ion batteries

In this article, novel configurations of wavy minichannels with both co- and counter-current operation modes are proposed for the thermal management of lithium-ion battery systems, and their performance is investigated by incorporating a 3D conjugative numerical model and an experimental test validation. The structure of each case is specified by variable wavelengths along the flow direction. Three criteria of heat transfer enhancements, temperature uniformity improvements, and flow resistance augmentations are considered to analyze the thermal and hydraulic characteristics of the nonuniform wavy minichannels. The results show that although the Nusselt number of the nonuniform cases is higher than that of the conventional ones (more than15%), they require higher friction factors (between 25.3 % and 93.6 %) to access such Nusselt numbers. At the studied range, a maximum Nu enhancement of 1.18 and a maximum f augmentation of 1.93 are recorded. It is found that the current operation mode is a key factor affecting the temperature uniformity degree. By increasing the coolant velocity from 0.106 to 0.951 m s−1 in the co-current mode, the temperature non-uniformity decreases from 14.79 to 1.10 K, while this range for the counter-current mode is from 6.73 to 0.43 K. It is also found that for a special design of the nonuniform wavy minichannels, the deviations of the temperature non-uniformity at the entire range of the coolant velocity are <0.7 K.

PTFE Crystal Growth in Composites: A Phase-Field Model Simulation Study.

We investigated, via a phase-field model simulation, the effects of a matrix’s properties and a filler’s characters on the polytetrafluoroethylene (PTFE) crystal growth process in composites under various supercooling degrees. The results show that the supercooling degree has a deciding influence on the crystal growth process. The intrinsic properties of PTFE polymer, such as anisotropic strength and phase transition latent heat, affect the growth rate, orientation, and interfacial integrity of the crystal trunk and the branching of the PTFE crystal growth process. The factors of the PTFE crystallization process, such as anisotropic strength and phase translation interface thickness, affect the uniformity and crystallization degree of the PTFE crystal. In the composites, the biphasic interface induces the crystal growth direction via the polymer chain segment migration rate, of which the degree depends on the shapes of the filler and the PTFE crystal nucleus. According to the results, choosing the low molecular weight PTFE and mixture filler with various particle sizes and surface curvatures as the raw materials of PTFE-based composites improves the crystallization of the PTFE matrix.

Establishment and application of grain morphology distribution model for quantitative analysis of titanium alloys with typical microstructures

A novel probability model of grain morphology distribution considering the orientation and size of non-spherical grains, including P01(r),P11(r),P02(r),P33(r),P12(r), is established based on the nearest-surface function, and it is used to reveal the dispersion and uniformity degree of different morphology grains in titanium alloys. Especially, the distribution probability of lamellar α intersection is introduced instead of the distributed relationship of different α lamellae, and the distributed relationship between lamellar and globular grains is transformed into the distribution of globular grains by the equivalent circle method. Then, several corresponding distribution probabilities are selected in terms of describing different microstructure states (equiaxed, basketweave, duplex microstructures). The model is applied to the quantitative analysis of TC4 alloy with different morphology grains. The results show that the distribution of α grains with different morphology in the β matrix becomes more inhomogeneous with increasing height reduction and cooling rate. Moreover, the larger the globular α size is, the greater the aggregation degree and the smaller the uniformity of other α grains around it is. The reliability of probability model is verified by the comparison between the predicted and the measured frequency distributions for the nearest neighbor surface distance r.

Co-composting of kitchen waste with agriculture and forestry residues and characteristics of compost with different particle size: An industrial scale case study

Since the implementation of domestic waste classification in China, the kitchen waste production has increased rapidly. The unique physical and chemical properties of kitchen waste make it impossible for direct composting for composting alone. This study investigated the co-composting of kitchen waste with agriculture and forest residues at an industrial scale at the Nangong Composting Plant (Located in Beijing). Cornstalks, garden waste, and watermelon seedlings were composted with kitchen waste, with the added agriculture and forestry residues comprising 5%, 10% and 20% of the weight. Industrial composting was performed 30 days at a scale of 165–180 tone. The mixed compost products were screened to different particle sizes, and the maturity, humification, and calorific value were analyzed. The kitchen waste mixed with 20% agricultural complementary materials reached hyperthermophilic temperature (82 °C), had reduced moisture content (45%), and resulted in better composting performance at an industrial scale. By adding 20% complementary materials to kitchen waste produced mature compost with a higher germination index (GI) (91%) by adjusting the pH, electrical conductivity (EC), carbon to nitrogen ratio (C/N), and moisture content. The compost in the 5% and 10% complementary materials treatments did not fully mature and had a GI of<10%, influenced by the higher EC and NH4+-N content. The property of final compost with different particle size vary greatly. The small particle size compost (≤45 mm) had higher uniformity, maturity, and humification degree, and it was suitable to use as a fertilizer; the larger particle size (>45 mm) had more material with lower calorific value (8000–10,000 kJ·kg−1), and could be used as refuse-derived fuel. To make better use of kitchen waste compost, 45-mm particle size screening is suggested at an industrial-scale composting plant. These results support industrial-scale kitchen waste composting in China.

Carotid artery vulnerable plaque model for cerebrovascular events by conventional ultrasound &amp; contrast-enhanced ultrasound: A preliminary study

Conventional ultrasound and contrast-enhanced ultrasound play an important role in the application of carotid plaque. To establish carotid artery vulnerable plaques model by conventional ultrasound combined with contrast-enhanced ultrasound, identify high-risk plaques that may lead to cerebrovascular events, and provide clinical risk warning of high-risk plaques of stroke. 205 cases of patients selected in 5053 patients with symptoms from 2018 to 2019 who were verified carotid plaques by conventional ultrasound and contrast-enhanced ultrasound image characteristics, 147 cases as a training set, establishing the carotid artery plaque model, analyzing the characteristic of the plaques and the relationship between cerebrovascular event, with 58 cases as a test set, verify the model. Routine carotid ultrasound and contrast-enhanced carotid ultrasound were performed in all enrolled patients. The gray-level characteristics of conventional ultrasound in the training concentration showed statistical differences in plaque morphology, fibrous cap morphology, uniformity and calcification degree in cerebrovascular events. The contrast enhanced ultrasound characteristics of plaques showed statistical differences in neovascularization and perfusion mode in cerebrovascular events. In the test set, there were statistical differences in the above conventional gray scale features and CEUS features. The vulnerable plaque model established by conventional ultrasound combined with contrast-enhanced ultrasound has good diagnostic value for the characteristic plaque of carotid artery with cerebrovascular events.

Energy utilization and heating uniformity of multiple specimens heated in a domestic microwave oven

To improve the energy utilization and quality of multiple specimens heated in a domestic microwave oven, we developed a theoretical model that considered the electromagnetic, heat, mass and momentum fields and phase change. Specimens with different distances, volumes and shapes were compared and discussed. The state parameter distribution uniformity and concentrative degree were described by the coefficient of variation (COVE, COVT, COVM and COVP), the microwave focusing degree (MFD) and thermal runaway. The energy utilization efficiency was quantified by the specific power absorption efficiency (SPAE). Microwave focusing, hot spots, and dry and wet spots occurred during the process and were influenced by the electric field distribution, mass and heat transfer and certain geometries. When the distance between the two specimens was approximately one wavelength (in free space), the energy utilization was higher, but the uniformity was worse. The SPAE of the specimens with larger volumes was lower due to energy attenuation, which gave rise to a lower average temperature, lower phase change rate, higher average moisture content and better moisture distribution uniformity. The distribution uniformity of the electric field and temperature of the cylindrical specimens were the best.

Effects of process parameters and chamber structure on plasma uniformity in a large-area capacitively coupled discharge

For 13.56 MHz large-area capacitively coupled plasma (CCP) discharges, the increase of plasma enhanced chemical vapor deposition (PECVD) chamber radius to 500 mm is likely to exacerbate the impact of edge effect. In this paper, based on COMSOL Multiphysics, a two-dimensional fluid model combined with the full set of Maxwell's equations is developed and validated. Simulation results indicate that the existence of the edge effect destroys the radial plasma uniformity of large-area discharges. The decrease of the RF voltage amplitude or chamber pressure causes an improvement in plasma radial uniformity, but the plasma density reduces. Only by adjusting the process parameters, the optimization of plasma uniformity degree is not obvious and the edge effect cannot be eliminated. Furthermore, the chamber structure has a significant influence on plasma uniformity. And enlarging the electrode gap or extending the grounded electrode length could help to obtain a uniform deposition by impairing the edge effect. The experiment results show that the film uniformity is improved by optimizing. The results obtained in this work could play a useful role in weakening the edge effect and raising the plasma uniformity of large-area CCP discharge.

Multi-physics simulation of wobbling laser melting injection of aluminum alloy with SiC particles: SiC particles gradient distribution in fusion zone

Laser melting injection (LMI) with SiC particles can strengthen fusion zone of metal alloy. How to improve the distribution uniformity of SiC particles are critical. In this work, a novel process of wobbling laser melting injection (WLMI) is proposed to suppress the gradient distribution of SiC particles in fusion zone of aluminum alloy. Moreover, a multiphase flow model by bi-directionally coupling the discrete element method and computational fluid dynamics is developed to simulate this WLMI process. The exchanges of both momentum and energy between particles and liquid are incorporated. It is the first time that the dynamic behaviors of both the liquid and particles during melting-solidification process under WLMI are reproduced in computational modeling. Both experimental and simulated results indicate that the distribution uniformity degree of SiC particles under WLMI, along depth and width directions, improves significantly compared with LMI. Physical mechanisms accounted for this phenomenon can be more thoroughly understood by the model. Firstly, the wobbling laser can increase the keyhole opening area, and decrease the distance between keyhole and molten pool bottoms, leading to a greater possibility that particles are captured by the liquid-solid interface in the bottom. Secondly, the reflected wobbling laser rays distributed unevenly on keyhole wall and the impact on melt surface caused by injected particles will produce downward drag forces, making the particles float to the center or the middle of molten pool.

Low differentially uniform permutations from the Dobbertin APN function over [formula omitted

Substitution boxes (S-boxes) play a central role in block ciphers. In substitution-permutation networks, the S-boxes should be permutation functions over F2n to realize the invertibility of the encryption. More importantly, the S-boxes should have low differential uniformity, high nonlinearity, and high algebraic degree in order to resist differential attacks, linear attacks, and higher order differential attacks, respectively. In this paper, we construct new classes of differentially 4 and 6-uniform permutations by modifying the image of the Dobbertin APN function xd with d=24k+23k+22k+2k−1 over a subfield of F2n. In addition, the algebraic degree and the lower bound of the nonlinearity of the constructed functions are given.