Increase In Area Ratio Research Articles

Numerical Simulation of the Slag Splashing Process in A 120 Ton Top-Blown Converter

Slag splashing operations at the end of the converter blow process can improve the furnace liner life and the converter operation rate. However, the effect of factors on slag splashing at actual dimensions is yet to be fully understood. A three-dimensional transient mathematical model coupled with the response surface analysis has been established to investigate the effects of the amount of remaining slag, oxygen lance height, and top-blowing nitrogen flowrate on the slag splashing process in a 120 ton top-blown converter. The predicted splashing density is validated by the experimental data. The numerical simulation results show that the splashing density and the splashing area ratio increase with the amount of remaining slag, which has the greatest effect on slag splashing. As the oxygen lance height decreases, the splashing density and the splashing area ratio first increase and then decrease. The top-blowing nitrogen flowrate is positively correlated with the splashing area ratio. When the oxygen lance height is high, the impact of the top-blowing nitrogen flowrate on the splashing density is not significant. The splashing density increases with increasing top-blowing nitrogen flowrate as the oxygen lance height is low.

Experimental investigation on microstructure and surface morphology deterioration of limestone exposed on acidic environment

Understanding evolution of microstructure and surface morphology is essential for studying the strength of building material in acidic enviorment. In this study, the microstructure of limestone samples immersed in acidic solutions of varying pH values was evaluated by nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM), while the joint surface morphology evolution process was determined by three-dimensional (3D) scanning experiments. Further, direct shear tests on the immersed jointed samples were conducted for shear properties analysis. It is found that the pore size distribution gradually changes from nanopore to micropore with the decrease in pH value, while the single pore area and perimeter increased and the fractal dimension decreased. Therefore, the increased pore distribution, enlarging in area, and change in the shape of the pores altered the microstructure and caused the increase in porosity. Also, with the decrease in pH value, the decrease rate of 3D relative fluctuation height, angle, and 3D area ratio increase. The 3D average fluctuation angle decreases the most, whereas the 3D area ratio decreases the least. In an acidic environment, the 3D surface morphology is significantly influenced by the 3D average fluctuation angle, which eventually changes joint roughness. Under the condition of acidic underground water, the microstructure of the joint wall and surface morphology of the joint degraded, thereby affecting the joint shear behavior. Therefore, the degradation of joint roughness coefficient and joint wall compressive strength should be considered for evaluating the joint mechanical properties in an acidic environment.

Quantitative assessment of computational efficiency of numerical models for surface flow simulation

Abstract To improve computational efficiency without accuracy losses for surface flow simulation, a dynamic bidirectional coupling model based on multigrid was applied. The flood-prone areas, where the inundation conditions were needed to detail, were discretized using finer grids, while the rest of the domains were assigned coarser grids to reduce computation time. Different time steps were adopted in coarse and fine grids. This paper presented an approach to quantitatively assess the computational efficiency under different domain discretization and grid generation conditions. Three test cases were considered to demonstrate the performance of the applied model. The results showed that the model had high computational efficiency while maintaining satisfactory simulation accuracy. The computational efficiency of the model was not only related to the size ratio of coarse to fine grids, but the area ratio of coarse grids to the entire computational domain. If the area ratio of coarse grids to the computational domain was constant, the computational efficiency improved exponentially with the increasing size ratio. If the size ratio of coarse to fine grids was constant, the computational efficiency improved linearly with the increasing area ratio. The proposed method offers a promising option for quantitatively assessing the computational efficiency of models.

Numerical study on calculation model of airflow temperature and humidity prediction in humid airway

AbstractIn deep coal mining, the high temperature and humidity environment are one of the main disasters threatening workers and equipment. To predict the temperature and humidity of airflow in the airway accurately, this study establishes a numerical calculation model of the surrounding rock temperature, airflow temperature, and humidity under the conditions of considering the moisture evaporation and heat absorption of the airway wall, the condensation and heat release of supersaturated water vapor in the airflow, and the influence of air compression or expansion. Combined with the two‐dimensional (2D) heat conduction model (considering the influence of the axial surrounding rock heat conduction of the airway), the axial strip partial moisture calculation model of the airway is proposed, and then the uniform moist wall model and the axial strip partial moist wall model are established. The influence of different parameters on the temperature and humidity of airflow is discussed by analyzing the results of numerical simulation of the uniform wet surface model (UWSM) and partly wet surface model (PWSM) of the airway wall. The results show that the surrounding rock temperature, especially the temperature distribution of the airway wall, calculated by using the 2D heat conduction model under the local humid airway conditions, is more realistic. The increment of airflow temperature decreases with the increase of wet area ratio, airflow temperature at the entrance and airway radius, and increases with relative humidity at the entrance. The calculation accuracy of temperature and humidity prediction for large ventilation networks can be further improved by using the equivalent humidity of the UWSM to replace the correction coefficient of the wet area ratio of the PWSM.

Numerical Simulation on Structural Integrity of Grain with Large Increased Area Ratio for Solid Rocket Motor

To evaluate the structural integrity of a type of solid rocket motor grain with a largely increased area ratio using free-loading modified double-base grain, the Schapery integral nonlinear viscoelastic constitutive equation with damage is derived, and the numerical simulation model of solid rocket motor grain is constructed. According to the mission profile of the grain during the equipment period, the numerical simulation research on the mechanical response characteristics of the grain under three typical working conditions, namely, platform vibration, underwater explosion impact, and ignition pressurization during the launch is carried out. The simulation results show that under the three typical working conditions, the grain will not produce structural damage and defects, and the mechanical response of the grain under the platform vibration and explosion impact load is far less than that under the launch ignition pressurization. The ignition pressurization should be considered in the grain structural integrity design of this type or similar structure solid rocket motor.

노후 1기 신도시 재정비 방안 연구

Since the 1960s, Korea announced the Housing 2 million Construction Plan (1988-1992) in May 1988, due to the rapid industrialization and high economic growth of around 10% in Seoul and other metropolitan areas. Since then, the first new town has been built in Bundang, Ilsan, Pyeongchon, Sanbon, and Jung-dong, Gyeonggi-do, supplying 294,000 houses to solve urban problems such as overcrowding in Seoul, About 30 years later, social problems such as the increase of old houses and intensifying traffic congestion emerged, and each candidate made various pledges to solve the problem of the first new town in the last presidential and local elections, and the National Assembly proposed legislation on the first new town reorganization, but no effective legislation has been prepared yet. Therefore, this study aims to identify the legislation related to the reorganization of the first new city proposed by the National Assembly, analyze related problems, and present major matters to be considered in legislation. As a result of the study, the main problems related to the 1st new city reorganization project were 1) excessive safety diagnosis regulations and unrealistic standards, 2) excessively long business period, and 3) floor area rate incentive limitations, Major improvements to be considered in the reorganization project include 1) rational improvement of safety diagnosis regulations, 2) integration of project procedures, simplification 3) increase of floor area ratio by applying new and renewable energy, 4) increase of floor area ratio for developting the smart town, 5) special application for additional floor area ratio, and 6) rational setting of old new city reorganization projects.

A combined inverse prediction and experimental analysis for the frozen ground heat transfer in a structure foundation

This paper takes the representative buried structure in permafrost regions, a transmission line tower foundation, as the research object. An inverse prediction is conducted in a scaled-down experimental system mimicking actual heat conduction of the frozen ground in a tower foundation. In permafrost regions, global warming and the heat transfer through the buried structures bring significantly adverse thermal effects on the stability of the infrastructures. In modeling the thermal effects, it has been a challenge to determine the ground surface boundary condition and heat source strength from the buried structures due to the complex climate and environmental conditions. In this work, based on the improved model predictive inverse method with an adaptive strategy, an inverse scheme is successfully implemented to simultaneously identify the time-varying surface temperature and the time-space-dependent heat source representing the buried structures. In this scheme, an adaptive time-varying predictive model is established by the rolling update of the sensitivity response coefficients according to the predicted temperature field to overcome the influence of nonlinear characteristics in the heat transfer process. The inverse method is verified by simulation and experimental data. According to the experimental inversion results, the reconstructed temperature distribution efficiently predicts the thermal state evolution of the permafrost foundation under seasonal freezing and thawing. It is found that, under the experimental conditions, the intensified thawing and freezing are significantly severe, e.g., the increased area ratio of active layer thickness is as high as 28% after building a tower, and the depth of permafrost table ranges from about 14 mm to about 38 mm, which could be detrimental to the stability and safety of the tower foundation. This study will provide valuable guidance for risk assessments or optimizing the design and maintenance of the real tower foundation and similar buried structures.

Biofunctionalization of polyetheretherketone implant material by bone-forming peptide-2 immobilization

Polyetheretherketone (PEEK) has favorable biomechanical properties to be used as an implant material. Unfortunately, it is hydrophobic and does not promote cellular adhesion, which could result in poor integration with bone tissue. Bio-functionalization of PEEK surface with osteogenic peptides derived from bone extracellular matrix proteins is an excit-ing approach to encourage bone formation around the implant. In the current study, bone-forming peptide-2 was immo-bilized on PEEK surface using two different methods, using dopamine and a diglycidyl ether as conjugate compounds, respectively. Peptide quantification test revealed that the two strategies resulted in the most amount of peptides were attached with 0.5 mM concentration and no further peptides were grafted with a higher peptide concentration. Both methods showed good peptide stability after agitation in aqueous solution. Peptide grafting was confirmed with ATR-FTIR. Surface characterizations with AFM and wettability tests resulted in a significant increase in surface roughness and surface area ratio for the peptide-grafted PEEK compared to unmodified PEEK, which led to a signifi-cant enhancement in the wettability of the modified PEEK surface

Examining the association between the built environment and active travel using GPS data: A study of a large residential area (Daju) in Shanghai.

Automobile dependence and physical inactivity have become common health challenges for residents in large suburban residential areas. Limited literature has examined the associations between the built environment and active travel in such residential areas and the differences in these associations among residents from different neighborhoods. To avoid inaccurate results potentially derived from residence-based measures, we adopt a mobility-based approach for environmental exposure assessment. Using GPS data from 530 trips made by 98 participants in a large residential area in Shanghai, we investigate the relationships between neighborhood types, pollution perceptions, built environment features and active travel. The results indicate that residents in affordable and relocation housing make fewer active trips than those in market-rate housing, while the built environment seems to mitigate this difference. Sports facilities promote active travel while commercial facilities and road intersections discourage it. We identify significant interactions between the percentage of green space and neighborhood type, as well as floor area ratio and air pollution perception. Interventions promoting active travel include active-travel-friendly design for commercial facilities and road intersections, the provision of more sports facilities, a careful increase in floor area ratio, and the provision of more green space that is attractive to residents from different neighborhoods.

Cognitive Impairment in Chronic Kidney Disease Is Associated with Glymphatic System Dysfunction

Introduction: This study was designed to explore the associations between impaired cognition in chronic kidney disease (CKD) patients and the dysfunction of the glymphatic system. Method: Data were obtained from 77 CKD patients and 50 age-matched healthy control individuals from the First Affiliated Hospital of Zhengzhou University. CKD patients were stratified into with and without impaired cognitive function. T2-weighted magnetic resonance imaging results were used to assess area ratios for the perivascular space and ventricles in participants, while the Montreal Cognitive Assessment and the Mini-Mental State Examination were employed to measure cognitive function. Correlations between the perivascular space or ventricle area ratios and cognitive impairment were assessed in CKD patients. Results: Significant increases in the burden of enlarged perivascular spaces in the frontal cortex and basal ganglia were observed in CKD patients with cognitive impairment relative to those without such impairment, with a concomitant increase in analyzed ventricle area ratios. Enlarged perivascular spaces in the frontal cortex, basal ganglia and increased area ratios of lateral ventricles and 4th ventricle exhibited relatively high sensitivity and specificity as means of differing between the CKD patients with and without cognitive impairment. Conclusion: These results indicate that the burden of enlarged perivascular spaces in the frontal cortex and basal ganglia and increases in ventricle area ratio values may offer utility as biomarkers that can aid in detection of even mild cognitive decline in individuals with CKD. The dysfunction of the glymphatic system may play a key role in the pathogenesis of CKD-related cognitive impairment.

Using multi-sourced big data to correlate sleep deprivation and road traffic noise: A US county-level ecological study

BackgroundRoad traffic noise is a serious public health problem globally as it has adverse psychological and physiologic effects (i.e., sleep). Since previous studies mainly focused on individual levels, we aim to examine associations between road traffic noise and sleep deprivation on a large scale; namely, the US at county level. MethodsInformation from a large-scale sleep survey and national traffic noise map, both obtained from government's open data, were utilized and processed with Geographic Information System (GIS) techniques. To examine the associations between traffic noise and sleep deprivation, we used a hierarchical Bayesian spatial modelling framework to simultaneously adjust for multiple socioeconomic factors while accounting for spatial correlation. FindingsWith 62.90% of people not getting enough sleep, a 10 dBA increase in average sound-pressure level (SPL) or Ls10 (SPL of the relatively noisy area) in a county, was associated with a 49% (OR: 1.49; 95% CrIs:1.19–1.86) or 8% (1.08; 1.00–1.16) increase in the odds of a person in a particular county not getting enough sleep. No significant association was observed for Ls90 (SPL of the relatively quiet area). A 10% increase in noise exposure area or population ratio was associated with a 3% (1.03; 1.01–1.06) or 4% (1.04; 1.02–1.06) increase in the odds of a person within a county not getting enough sleep. InterpretationTraffic noise can contribute to variations in sleep deprivation among counties. This study suggests that policymakers could set up different noise-management strategies for relatively quiet and noisy areas and incorporate geospatial noise indicators, such as exposure population or area ratio. Furthermore, urban planners should consider urban sprawl patterns differently in terms of noise-induced sleep problems.

Study of Tensile Strength of Aluminum Alloy Caused by Pulsed Laser Drilling

In the process of pulsed laser drilling, the material properties in the heat-affected zone will change due to the thermal effect of the laser. To study the effect of this change on the material tensile strength, two lasers were used to punch the standard 6061 aluminum alloy specimens with millisecond and nanosecond pulse widths, and then the tensile test was carried out on the standard specimens with a tensile tester to measure the ultimate tensile strength of the aluminum alloy. Finally, the micro-morphology of the fracture was photographed by scanning electron microscopy (SEM), and the fracture mechanism of the aluminum alloy was analyzed. The experimental results show that the relationship between the rate of intensity change induced by the millisecond laser and the ablation area ratio is more linear than that of the nanosecond laser; with the increase of ablation area ratio, the rate of intensity changes induced by the nanosecond and millisecond lasers becomes increasingly closer; three types of fractures are produced with two types of laser ablation; the plasticity of the material rapidly decreases with laser drilling, and the main reason for decrease in plasticity was stress concentration. This study provides an important point of reference for how to ensure the strength and plasticity of the components after laser drilling.

Optimization of Urban Block Form by Adding New Volumes for Capacity Improvement and Solar Performance Using A Multi-Objective Genetic Algorithm: A Case Study of Nanjing

During urban renewal, multi-story residential blocks face a contradiction of balancing residential capacity improvement and solar constraint. This paper constructed a set of automatic workflows for adding new volumes to existing buildings, and a multi-objective optimization was applied with a Wallacei plug-in in Grasshopper to optimize the solar radiation, solar hours, and block capacity. First, this study established three building addition modes of existing blocks in the horizontal direction, vertical direction, and mixed direction, respectively. Three optimization objectives—maximum floor area ratio, maximum average radiation amount, and minimum solar shade—were defined. Second, the net increase in the floor area ratio of the block was calculated to balance capacity improvement and solar constraint. Third, the advantages of the three addition modes under different orientations were discussed. Among all three modes, the mixed addition mode had the best capacity improvement effect, with a 70% increase in floor area ratio. The vertical addition mode had the least impact on the solar shade of existing buildings. The horizontal addition mode could further improve the floor area ratio in areas where building height was strictly limited. The results can provide insights and inspiring guidelines for the renewal of the existing residential blocks to solve the floor area ratio constraint from solar radiation, as well as achieve urban function reconstruction and vitality regeneration.

Experimental Study on Shear Strengths of Ice-Roof Interface Aiming the Study of Roof Snow Sliding

Snow sliding of roofs is a threat to the structural safety of roof structures by causing a surcharge of local snow load on the lower roof and may pose a serious threat to pedestrians and vehicles on the ground. Therefore, it is of great significance to study the mechanism of snow sliding on roofs. Under the action of ambient temperature, solar radiation, internal heating of the building, etc., the bottom layer of roof snow is often presented in the form of porous ice after a complicated phase transition of the snow particles. Under this circumstance, the interface between roof snow and the roof can be seen as the contact between porous ice and the roofing material. In order to investigate the initialization of roof snow sliding from the material point of view, the shear performance of the interface between different roofing materials and ice with different porosities was carried out in this study. The effects of different ambient temperatures (−4, −6, and −8°C), different normal stress (0, 50, and 100 kPa), and different ice porosities (represented by the contact area ratio of 1.0, 0.8, and 0.6) on this shear performance were analyzed by direct shear tests. The test results showed that the shear failure between the ice and the roofing material was brittle, and the interface shear strength was affected by the ambient temperature, normal stress, contact area ratio, as well as the material type: the strength increases with the decrease of ambient temperature, the increase of normal stress, the increase of contact area ratio, and the increase of surface roughness of the material. Based on the test results, a quantitative relationship between the interface shear strength and the related factors was given in the article, which provides a useful reference for future experimental or simulation studies on roof snow sliding.

유리렌즈 성형 금형에서 방열블록 형상에 따른 금형 가열부의 열전달 특성 연구

The purpose of this study is to propose a better contact surface pattern of a heat radiating block in a progressive GMP (Glass Molding Process) heating assembly. In this study, a simulation model based on FEM was developed to perform a thermal analysis for the heating assembly. It was verified by comparing experimental results. The temperature distribution on the heating block surface and heating energy consumption was analyzed with the change of contact surface pattern and area of a heat radiating block. The considered pattern on the contact surface was cross (+) and straight (-) shape. The contact area ratio was changed from 16 to 100%. The simulation results show that the heating energy consumption increased to reach a target temperature with the increase of contact area ratio. The straight-shaped patterns on a heat radiating block presented more uniform temperature distribution on the mold heating surface than the cross shaped surface, whereas it resulted in a slightly higher energy consumption of up to 9%. This study shows that the contact surface pattern on a heat dissipating block can control the temperature distribution on the mold heating surface.

Effect of piston texture at inclination and eccentricity work conditions on damping characteristics of a hydraulic shock absorber

In order to accurately predict the damping characteristics of a hydraulic shock absorber under piston inclination and eccentricity conditions, especially, considering effects of piston surface construction. In present work, taking account of piston slight inclination and eccentricity, a more detailed mathematical model was developed to estimate effects of piston texture on damping characteristics. Based on the mathematical models of reservoir and compression stroke coupled with Reynolds equation, a new damping force model was developed, which analyzed effects of piston structure on damping characteristics. The mathematical models of piston texture, piston slight inclination, piston eccentricity and combinations of three cases are developed to analyzed in detailed effects of piston texture at different work conditions on damping characteristics. The results shown that the friction force of piston increases parabolically with increasing depth ratio, and that of piston increases linearly with increasing area ratio. Piston textures have little effects on damping characteristics at specific structural parameters conditions when piston normal operation, however, textures of slight inclined and eccentric piston have great effects. As a result, piston textures might cause high damping force, destroyed comfort and safety. Therefore, it is necessary that effects of piston surface construction were precisely predicted on damping characteristics under different work conditions. The results might provide a new insight for the design of hydraulic shock absorber and investigation of vehicle system dynamics.

Changes in sizes of mesophyll cells underlies the adaptation of Betula platyphylla Sukacz. leaf to increased climate aridity

Climate changes in Central Asia attract increasing attention to studies in successions, ecosystem transformations and plant adaptation. Functional mechanisms of plant adaptation are related to the changes in leaf structure, first of all, the architecture of carbon-assimilating tissues. We studied leaf mesophyll structure of Betula platyphylla Sukacz. from geographical regions in the southern part of East Siberia and Mongolia with different climate aridity. Birch populations represented a latitudinal range from the middle taiga to the forest-steppe. According our results changes in mesophyll structure occurred along the aridity gradient, which manifested in a significant decrease (by 38-40 %) in cell sizes and an increase in surface area and volume ratio of mesophyll. Such rearrangement of mesophyll structure provides a higher rate of intraleaf diffusion of CO2 and the maintenance of high level of photosynthesis under water deficiency. We concluded that changes in the sizes of carbon-assimilating cells which underlies the restructuring of leaf three-dimensional organization provides regulation of gas exchange, and is a key mechanism for the adaptation of the photosynthetic function of Betula platyphylla to increased aridity of the climate.

Effects on Film Cooling Performance in the Showerhead From Geometric Parameterization of Shaped Hole Designs

Abstract The high heat loads at the leading-edge regions of turbine vanes and blades necessitate the most robust thermal protection, typically accomplished via a dense array of film cooling holes, nicknamed the “showerhead.” Although research has shown that film cooling using shaped holes provides more reliable thermal protection than that using cylindrical holes, the effects on cooling performance from varying the geometric details of the shaped hole design are not well characterized. In this study, adiabatic effectiveness and off-the-wall thermal field measurements were conducted for two shaped hole geometries designed as successors to a baseline hole geometry presented in a previous study. One geometry with a 40% increase in area ratio exhibited only a marginal improvement in adiabatic effectiveness (∼10%). A second design with a 12 deg forward and lateral expansion angle with a breakout area 40% larger performed marginally worse than its matched area ratio counterpart (∼15% lower), suggesting a negative sensitivity to breakout area. Such changes in performance for different shaped hole designs were small compared to the boost in performance gained by switching from a cylindrical hole to a shaped hole, which suggests cooling performance is insensitive to specific shaped hole details provided the exterior coolant flow is well-attached.

Strength deterioration mechanism of bentonite modified loess after wetting\u2013drying cycles

The employment of bentonite modified loess (BML) is a common method of constructing the anti-seepage lining of landfills in the loess region of China, and its long-term secure performance is threatened by wetting–drying (W–D) cycles. Taking the remolded loess (RL) and BML with 15% in mass of bentonite as research objects, the W–D cycles test, scanning electron microscope test and direct shear test were carried out to analyze the effects of W–D cycles on the microstructure and shear strength of samples. The regression equations between strength and micro-pore structure parameters were established by the multivariate linear stepwise regression method. The damage mechanism of BML after W–D cycles was studied by establishing damage degree models based on pore area ratio and cohesion. Results indicate that the water absorption and expansion of bentonite effectively block the intergranular pores, resulting in more medium and small pores and more pronounced surface contact of particles. After W–D cycles, the particle arrangement of samples before and after bentonite modification tends to be loose. Both the pore area ratio and fractal dimension increase and tend to stabilize after five cycles. The BML exhibits lower pore area ratio and greater fractal dimension while its cohesion and internal friction angle show more significant decrease after W–D cycles than those of RL. The damage variables based on pore area ratio and cohesion well describe the W–D induced damage of loess before and after modification from macro- and micro-scale perspectives. The damage degree of samples increases with W–D cycles, but the increment decreases.

A simulation study on stress-seepage characteristics of 3D rough single fracture based on fluid-structure interaction

This paper expounds on the process of deformation and seepage field change of single coarse fracture under normal stress and puts forward a numerical simulation framework based on fluid-structure coupling method to reasonably link contact deformation of fracture surface with seepage field change. The geometric model of a three-dimensional rough single fracture surface with controllable JRC is established based on the random surface generation method. The numerical test model of radiation flow of single fracture in rough rock is constructed, which is consistent with the laboratory test. Through carrying out numerical simulation tests of different JRC and normal stress conditions, this paper discusses the phenomenon and intrinsic nature of the influence of JRC on fracture seepage characteristics. The increase in eddy current intensity and eddy current area ratio is the inherent characteristics of the seepage field characteristics after JRC increases. With the rise of energy loss, the macroscopic seepage flow decreases. In addition, with the advantage of the fluid-structure interaction method, the fracture deformation characteristics under different normal stresses are reflected by the ratio of the contact area. The correlation among fracture surface deformation, velocity vector, and seepage pressure are analyzed. Finally, the cubic polynomial correlation between gap width ratio and contact area ratio is established and verified. It is of positive significance to quantify the influence of coarse single fracture contact ratio on deformation-seepage coupling characteristics under normal stress.