Internal auditors hold a unique position in their organizations to prevent, deter, and detect corporate wrongdoings. However, the role of this profession in investigating their ethical decision-making behaviors toward...Internal auditors hold a unique position in their organizations to prevent, deter, and detect corporate wrongdoings. However, the role of this profession in investigating their ethical decision-making behaviors towards internal whistle-blowing intentions has been very often neglected. Furthermore, although extensive researches have been undertaken on the issue of whistle blowing globally, empirical studies on this area are still scarce in Malaysia. This paper examines internal whistle-blowing intentions among internal auditors in Malaysia by utilizing three independent vignettes. A mail survey was conducted to investigate demographic and individual factors that could influence internal auditors' ethical decision-making processes. The likelihood for internal whistle-blowing intentions was significant among internal auditors' ethical judgments for all the three vignettes. Demographic factors (gender, age, and tenure) and other individual factors (locus of control and organizational commitment) failed to explain the likelihood of internal auditors' internal whistle-blowing intentions. Findings should aid researchers in their understandings of the determinants of individuals' internal whistle-blowing behaviors.展开更多
Lyrics is a special type of text which is more stiring and vivid due to the combination of beautiful melody. SFG is widelyadopted in text analysis as it is very effective in explaining the ideational, interpersonal an...Lyrics is a special type of text which is more stiring and vivid due to the combination of beautiful melody. SFG is widelyadopted in text analysis as it is very effective in explaining the ideational, interpersonal and textual functions served by a particulartext. This paper is an analysis of the lyrics of Blowing in The Wind in terms of SFG, aiming at providing a new perspective on the in-terpretation of the song.展开更多
The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based ...The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error±300 m^(3)is 96.67%;determination coefficient (R^(2)) and root mean square error (RMSE) are0.6984 and 150.03 m^(3), respectively. The oxygen blow time prediction hit ratio within the error±0.6 min is 89.50%;R2and RMSE are0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.展开更多
This article discusses and analyzes the law of nitrogen increase in liquid steel and the main factors affect-ing the nitrogen increasing of molten steel,through the way of adding nitrogen to molten steel by bottom blo...This article discusses and analyzes the law of nitrogen increase in liquid steel and the main factors affect-ing the nitrogen increasing of molten steel,through the way of adding nitrogen to molten steel by bottom blowing nitrogen gas in LF refining process.It is considered that the main factors affecting the nitrogen increasing instability of molten steel are the initial temperature of LF refining,nitrogen relative element,surface active elements[O]and[S]of steel liquid,and bottom blowing rate of ladle.The large-scale production practice shows that T[O]not more than 50×10-6 and[S]is not more than 0.020 in LF refining at the initial temperature of not less than 1570.The liquid steel nitrogen enrichment test is carried out by ladle bottom blowing nitrogen gas after 20 min of refining,the flow rate is set as(6.0~7.0)NL/min per ton,and it is turned to 2 NL/min at 6 min before the end of refining,the nitrogen increasing rate of liquid steel is basically stable at(5~6)×10-6 per minute.展开更多
A three-dimensional mathematical model was developed to investigate the effect of gas blowing nozzle angles on multiphase flow,circulation flow rate,and mixing time during Ruhrstahl-Heraeus(RH) refining process.Also,a...A three-dimensional mathematical model was developed to investigate the effect of gas blowing nozzle angles on multiphase flow,circulation flow rate,and mixing time during Ruhrstahl-Heraeus(RH) refining process.Also,a water model with a geometric scale of 1:4 from an industrial RH furnace of 260 t was built up,and measurements were carried out to validate the mathematical model.The results show that,with a conventional gas blowing nozzle and the total gas flow rate of 40 L·min^(-1),the mixing time predicted by the mathematical model agrees well with the measured values.The deviations between the model predictions and the measured values are in the range of about 1.3%–7.3% at the selected three monitoring locations,where the mixing time was defined as the required time when the dimensionless concentration is within 3% deviation from the bath averaged value.In addition,the circulation flow rate was 9 kg·s^(-1).When the gas blowing nozzle was horizontally rotated by either 30° or 45°,the circulation flow rate was found to be increased by about 15% compared to a conventional nozzle,due to the rotational flow formed in the up-snorkel.Furthermore,the mixing time at the monitoring point 1,2,and 3 was shortened by around 21.3%,28.2%,and 12.3%,respectively.With the nozzle angle of 30° and 45°,the averaged residence time of 128 bubbles in liquid was increased by around 33.3%.展开更多
A numerical model of an iron bath smelting reduction furnace with side-bottom combined blowing was established to study the influence of blowing arrangements on the stirring effect of the molten pool,and the accuracy ...A numerical model of an iron bath smelting reduction furnace with side-bottom combined blowing was established to study the influence of blowing arrangements on the stirring effect of the molten pool,and the accuracy of numerical simulation was verified by water model experiment.By comparing the flow field of molten pool with single nozzle,double nozzles(symmetrical and asymmetrical),and four nozzles(symmetrical and asymmetrical),the proportion of dead zone,average turbulent kinetic energy,and mixing time,the results show that asymmetrical bottom blowing is better than symmetrical bottom blowing,and the effect of double nozzles bottom blowing was better than that of four nozzles bottom blowing.The mixing effect is the worst under the condition of single nozzle.When the bottom blowing is asymmetrical with double nozzles,the mixing time is the shortest.Under the condition of double nozzles asymmetrical bottom blowing,when the insertion angle and depth of side lance are larger and deeper,the velocity streamline of molten slag layer is denser and the value is larger;meanwhile,the reflux of molten iron layer is larger,the proportion of dead zone is smaller,and the whole molten pool is fully stirred.When the insertion depth of the side lance is deeper,the gas holdup in the molten pool is greater and the stirring of the molten pool is more intense,while the insertion angle has little effect on the gas holdup.By comparing the influence of different side blowing conditions on the slag layer,it is found that the slag layer is divided into two layers by double-layer side lance,with the critical surface of the slag layer at about 200-260 mm from the bottom,and the insertion depth of the lower side lance has a greater influence on the layering of the slag.展开更多
Through systematical experiment design, the physical blowing agent(PBA) mass loss of bio-based polyurethane rigid foam(PURF)in the foaming process was measured and calculated in this study, and different eco-friendly ...Through systematical experiment design, the physical blowing agent(PBA) mass loss of bio-based polyurethane rigid foam(PURF)in the foaming process was measured and calculated in this study, and different eco-friendly PBA mass losses were measured quantitatively for the first time. The core of the proposed method is to add water to replace the difference, and this method has a high fault tolerance rate for different foaming forms of foams. The method was proved to be stable and reliable through the standard deviations σ1and σ2for R1(ratio of the PBA mass loss to the material total mass except the PBA) and R2(ratio of the PBA mass loss to the PBA mass in the material total mass) in parallel experiments. It can be used to measure and calculate the actual PBA mass loss in the foaming process of both bio-based and petroleumbased PURF. The results show that the PBA mass loss in PURF with different PBA systems is controlled by its initial mass content of PBA in PU materials ω. The main way for PBA to dissipate into the air is evaporation/escape along the upper surface of foam. This study further reveals the mechanism of PBA mass loss: the evaporation/escape of PBA along the upper surface of foam is a typical diffusion behavior. Its spread power comes from the difference between the chemical potential of PBA in the interface layer and that in the outside air. For a certain PURF system, R1has approximately linear relationship with the initial mass content of PBA in PU materials ω, which can be expressed by the functional relationship R1= kω, where k is a variable related to PBA’s own attributes.展开更多
Cryogenic insulation material rigid polyurethane(PU)foams were developed using bio-based and recycled feedstock.Polyols obtained from tall oil fatty acids produced as a side stream of wood biomass pulping and recycled...Cryogenic insulation material rigid polyurethane(PU)foams were developed using bio-based and recycled feedstock.Polyols obtained from tall oil fatty acids produced as a side stream of wood biomass pulping and recycled polyethylene terephthalate were used to develop rigid PU foam formulations.The 4th generation physical blowing agents with low global warming potential and low ozone depletion potential were used to develop rigid PU foam cryogenic insulation with excellent mechanical and thermal properties.Obtained rigid PU foams had a thermal conductivity coefficient as low as 0.0171 W/m·K and an apparent density of 37-40 kg/m^(3).The developed rigid PU foams had anisotropic compression strength properties,which were higher parallel to the foaming direction.Moreover,the compression strength was also influenced by the type of applied bio-based polyol.The bio-based polyols with higher OH group functionality delivered higher crosslinking density of polymer matrix;thus,the mechanical properties were also higher.The mechanical strength of the foams increased when materials were tested at liquid nitrogen temperature due to the stiffening of the polymer matrix.The thermal properties of the developed materials were determined using differential scanning calorimetry,dynamic mechanical analysis,and thermogravimetric analysis methods.Lastly,the developed rigid PU foams had good adhesion to the aluminium substrate before and after applying cyroshock and an excellent safety coefficient of 4-5.Rigid PU foams developed using Solstice LBA delivered adhesion strength of~0.5 MPa and may be considered for application as cryogenic insulation in the aerospace industry.展开更多
Unusual head trauma is rare with various mechanisms of occurrence. The injuries can be similar to those of road accidents but sometimes with significant complexities. The objective was to determine the frequency of th...Unusual head trauma is rare with various mechanisms of occurrence. The injuries can be similar to those of road accidents but sometimes with significant complexities. The objective was to determine the frequency of this pathology in our practice, describe the different mechanisms and report the craniocerebral lesions caused by this type of trauma. Materials and Method: This was a descriptive study with retrospective collection spread over a period of 3 years. After selecting the files, the patients and/or their companions were contacted by telephone to inquire about them and then returned to the consultation for reassessment. Disease history and information were obtained from patients’ medical records. Result: The frequency of this pathology was 1.78% and his incidence was 0.4 cases per month. The average age of the patients was 13.47 years. All the victims were male. 41.17% of patients were in school. The mechanisms of trauma were the hoof blow 47.1%, the horn blow 29.4% and the stone blow 11.7% respectively. 23.5% of patients were confused and 11.7% children were in coma. One patient presented an anisocoria. The motor deficit was present in 5 cases. CT-scan made it possible to highlight a skull depressing fracture 58.8% and confirm a craniocerebral wound in 35.3%. The average time between patient admission to hospital and completion of surgery was 24.5 hours. The surgery had consisted of the trimming of cranio-cerebral wounds, exploration, duroplasty and lifting of skull depressing fracture. After 15 months of follow-up, the evolution was favorable in 53.3%, the morbidity was 33.4% and the mortality 17.6%. Conclusion: These are rare but serious conditions because they are fatal and disabling. An early and multidisciplinary management can hope to have a good favorable.展开更多
Gas blowing is a valid method to remove the impurities from metallurgical grade silicon(MG-Si) melt.The thermodynamic behavior of impurities Fe,Al,Ca,Ti,Cu,C,B and P in MG-Si was studied in the process of O2 blowing...Gas blowing is a valid method to remove the impurities from metallurgical grade silicon(MG-Si) melt.The thermodynamic behavior of impurities Fe,Al,Ca,Ti,Cu,C,B and P in MG-Si was studied in the process of O2 blowing.The removal efficiencies of impurities in MG-Si were investigated using O2 blowing in ladle.It is found that the removal efficiencies are higher than 90% for Ca and Al and nearly 50% for B and Ti.The morphology of inclusions was analyzed and the phases Al3Ni,NiSi2 and Al3Ni were confirmed in MG-Si by X-ray diffraction.It was found that SiB4 exists in Si?B binary system.The chemical composition of inclusions in MG-Si before and after refining was analyzed by SEM-EDS.It is found that the amount of white inclusion reduces for the removal of most Al and Ca in the forms of molten slag inclusion and the contents of Fe,Ni and Mn in inclusion increase for their inertia in silicon melt with O2 blowing.展开更多
Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments.It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulenc...Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments.It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence inhibitor.It dramatically increases the peak concentration time,and greatly decreases the dead volume,and reduces the minimum residence time.The gas blowing location,gas flow rate,and porous plug area greatly influence the flow characteristics in the tundish; the gas blowing location near the baffle,smaller gas flow rate,and smaller porous plug area are better for improving the fluid flow characteristics.Using gas blowing can reduce the difference of flows at the middle outlets and side outlets for the multi-strand tundish.Bubbles produced by gas blowing can absorb small inclusions and provide the condition for inclusion collision and aggregation.Therefore,introducing gas blowing into a tundish and combining the turbulence inhibitor can improve inclusion floating and removal,and the cleanness of molten steel can be advanced.展开更多
The bubble growth and detachment behavior in the bottom blowing process were investigated. Four multi-hole nozzle configurations with different opening ratios were assessed experimentally using high-speed photography ...The bubble growth and detachment behavior in the bottom blowing process were investigated. Four multi-hole nozzle configurations with different opening ratios were assessed experimentally using high-speed photography and digital image processing. For these configurations, the experiments reveal that the bubble growth consists of a petal-like stage, an expansion stage and a detachment stage. The petal-like shape is qualitatively described through the captured images, while the non-spherical bubbles are analyzed by the aspect ratio. The bubble size at the detachment is quantified by the maximum caliper distance and the bubble equivalent diameter. Considering the dependence on the opening ratio, different prediction models for the ratio of maximum caliper distance to hydraulic diameter of the nozzle outlet and the dimensionless bubble diameter are established. The comparative analysis results show that the proposed prediction model can accurately predict the bubble detachment size under the condition of multi-hole nozzles.展开更多
The effects of operation parameters of combined blowing converter on the volumetric mass transfer coefficient between slag and steel are studied with a cold model with water simulating steel, oil simulating slag and b...The effects of operation parameters of combined blowing converter on the volumetric mass transfer coefficient between slag and steel are studied with a cold model with water simulating steel, oil simulating slag and benzoic acid as the transferred substance between water and oil. The results show that, with lance level of 2.1m and the top blowing rate of 25000Nm3/h, the volumetric mass transfer coefficient changes most significantly when the bottom blowing rate ranges from 384 to 540Nm3/h. The volumetric mass transfer coefficient reaches its maximum when the lance level is 2.1m, the top blowing rates is 30000Nm3/h, and the bottom blowing rate is 384Nm3/h with tuyeres located symmetrically at 0.66D of the converter bottom.展开更多
Currently, many studies have been made for years on dimensions of pneumatic nozzle, which influence the flow characteristic of blowing system. For the purpose of outputting the same blowing force, the supply pressure ...Currently, many studies have been made for years on dimensions of pneumatic nozzle, which influence the flow characteristic of blowing system. For the purpose of outputting the same blowing force, the supply pressure could be reduced by decreasing the ratio of length to diameter of nozzle. The friction between high speed air and pipe wall would be reduced if the nozzle is designed to be converging shape comparing with straight shape. But the volume flow and pressure, discussed in these studies, do not describe energy loss of the blowing system directly. Pneumatic power is an innovative principle to estimate pneumatic system’s energy consumption directly. Based on the above principle, a pulse blowing method is put forward for saving energy. A flow experiment is carried out, in which the high speed air flows from the pulse blowing system and continuous blowing system respectively to a plate with grease on top. Supply pressure and the volume of air used for removing the grease are measured to calculate energy consumption. From the experiment result, the pulse blowing system performs to conserve energy comparing with the continuous blowing system. The frequency and duty ratio of pulse flow influence the blowing characteristic. The pulse blowing system performs to be the most efficient at the specified frequency and duty ratio. Then a pneumatic self-oscillated method based on air operated valve is put forward to generate pulse flow. A simulation is made about dynamic modeling the air operated valve and calculating the motion of the valve core and output pressure. The simulation result verifies the system to be able to generate pulse flow, and predicts the key parameters of the frequency and duty ratio measured by experiment well. Finally, on the basis of simplifying and solution of the pulse blowing system’s mathematic model, the relationship between system’s frequency duty ratio and the dimensions of components is simply described with four algebraic equations. The system could be designed with specified frequency and duty ratio according to the four equations. This study provides theoretical basis for designing energy-saving air blowing system.展开更多
Blowing snow is an important part of snow hydrologic processes in mountainous region, however the related researches were rare for the Qilian mountainous region where blowing snow is frequent. Using the observation da...Blowing snow is an important part of snow hydrologic processes in mountainous region, however the related researches were rare for the Qilian mountainous region where blowing snow is frequent. Using the observation dataset in 2008 snow season in Binggou wa- tershed in Qilian mountainous region, we systematically studied the energy and mass processes of blowing snow by field observation and model simulation. The results include the analysis of snow observation, the occurrence probability of blowing snow, blowing snow transport and blowing snow sublimation. It was found that blowing snow was obvious in high altitude region (4,146 m), the snow redislribution phenomena was remarkable. In Yakou station in the study region, blowing snow was easily occurred in midwinter and early spring when no snowmelt, the blowing snow transport was dominated in this period; when snowmelt beginning, the occur- rence probability of blowing snow decreased heavily because of the increasing air temperature, melt, and refrozen phenomena. The blowing snow sublimation accounted for 41.5% of total snow sublimation at Yakou station in 2008 snow season.展开更多
A vorticity-velocity method was used to study the incompressible viscous fluid flow around a circular cylinder with surface suction or blowing. The resulted high order implicit difference equations were effeciently so...A vorticity-velocity method was used to study the incompressible viscous fluid flow around a circular cylinder with surface suction or blowing. The resulted high order implicit difference equations were effeciently solved by the modified incomplete LU decomposition conjugate gradient scheme ( MILU-CG). The effects of surface suction or blowing' s position and strength on the vortex structures in the cylinder wake, as well as on the drag and lift forces at Reynoldes number Re = 100 were investigated numerically. The results show that the suction on the shoulder of the cylinder or the blowing on the rear of the cylinder can effeciently suppress the asymmetry of the vortex wake in the transverse direction and greatly reduce the lift force; the suction on the shoulder of the cylinder, when its strength is properly chosen, can reduce the drag force significantly, too.展开更多
The theoretical model of the flow field of the dual slot die in melt blowing process is founded. The model is solved numerically with finite difference method. The distributions of the air velocity component in x dire...The theoretical model of the flow field of the dual slot die in melt blowing process is founded. The model is solved numerically with finite difference method. The distributions of the air velocity component in x direction along x-axis and y-axis and the air temperature distributions along x-axis and y-axis are obtained via numerical computation. The computation results coincide with the experimental data given by Harphain and Shambaugh. The distributions of the air velocity and air temperature are introduced into the air drag model of melt blowing. The model prediction of the fiber diameter agrees with the experimental data well.展开更多
Nowadays, in China, the bottom-blowing technique plays an important role in accelerating the molten bath stirring and promoting the metallurgical reactions in electric arc furnace (EAF) steelmaking. The innovations of...Nowadays, in China, the bottom-blowing technique plays an important role in accelerating the molten bath stirring and promoting the metallurgical reactions in electric arc furnace (EAF) steelmaking. The innovations of bottom-blowing technologies in EAF steelmaking were reviewed. The optimized bottom-blowing arrangement in EAF based on the furnace structure and the position of electrodes was introduced, and the fluid flow characteristics of EAF molten bath with bottomblowing were analyzed. Furthermore, bottom-blowing CO2 in EAF can facilitate the carbon-oxygen reaction reaching equilibrium and decrease the content of nitrogen in molten steel due to its special metallurgical properties. Pulsating bottom-blowing in EAF can effectively improve the molten bath stirring through the action of the unsteady bottom blowing gas streams, which could make the fluid flow field more disorderly than the steady bottom-blowing. And submerged O2 injection with CO2 in EAF can noticeably strengthen the EAF molten bath stirring, increase the production efficiency and improve the molten steel quality.展开更多
Biocomposite films prepared with melt compounding and film blowing have become a new trend in plastic research to deliver more eco-friendly packages.Polylactic acid(PLA)was melt compounded with minimally processed dat...Biocomposite films prepared with melt compounding and film blowing have become a new trend in plastic research to deliver more eco-friendly packages.Polylactic acid(PLA)was melt compounded with minimally processed date palm leaf fiber(DPLF)and converted into films by blown film extrusion.The compounding was done in order to enhance the film mechanical properties in one hand,and to decrease the film production cost in the other hand.In this present study,a reference PLA film and films with 1%,2%,and 5%of DPLF(weight%)were produced with different process parameters.The spatial variations in films thickness and lay flat width indicate that the addition of DPLF up to 2%enhances the bubble stability for the tested process parameters.However,the composite with 5%DPLF shows nearly the same processability window as the neat PLA.The structural and mechanical characterizations of films suggest a reinforcing effect of the PLA matrix up to 2%of fiber(with an optimum at 1%).Larger DPLF loading leads to depressed and more anisotropic mechanical properties,related to an increased density of defects at the fiber-PLA fragile interface and to a DPLF-induced enhanced PLA thermal degradation and amorphous phase orientation.展开更多
We have tried to prepare the microcapsules containing water droplets stabilized with solid powder by utilizing the (W/O)/W emulsion. The water droplets as core material were stabilized in the monomer droplets with tit...We have tried to prepare the microcapsules containing water droplets stabilized with solid powder by utilizing the (W/O)/W emulsion. The water droplets as core material were stabilized in the monomer droplets with titanium dioxide (TiO2) as a particulate surfactant. Before adding the TiO2 powder into the monomer phase, the powder was modified with triethoxyvinylsilane to adjust the degree of hydrophobicity and to promote adhesion on the interface between the inner water phase and the monomer phase in the (W/O) emulsion. It was investigated how the degree of hydrophobicity of the TiO2 powder affected the stability of water droplets in the (W/O) emulsion and the (W/O) droplets in the (W/O)/W emulsion. Moreover, the microcapsule diameters were measured before and after the expansion operation where the water droplets microencapsulated were applied as a blowing agent. The expansion ratio was increased with increase in the stability of the water droplets and the amount of water microencapsulated.展开更多
文摘Internal auditors hold a unique position in their organizations to prevent, deter, and detect corporate wrongdoings. However, the role of this profession in investigating their ethical decision-making behaviors towards internal whistle-blowing intentions has been very often neglected. Furthermore, although extensive researches have been undertaken on the issue of whistle blowing globally, empirical studies on this area are still scarce in Malaysia. This paper examines internal whistle-blowing intentions among internal auditors in Malaysia by utilizing three independent vignettes. A mail survey was conducted to investigate demographic and individual factors that could influence internal auditors' ethical decision-making processes. The likelihood for internal whistle-blowing intentions was significant among internal auditors' ethical judgments for all the three vignettes. Demographic factors (gender, age, and tenure) and other individual factors (locus of control and organizational commitment) failed to explain the likelihood of internal auditors' internal whistle-blowing intentions. Findings should aid researchers in their understandings of the determinants of individuals' internal whistle-blowing behaviors.
文摘Lyrics is a special type of text which is more stiring and vivid due to the combination of beautiful melody. SFG is widelyadopted in text analysis as it is very effective in explaining the ideational, interpersonal and textual functions served by a particulartext. This paper is an analysis of the lyrics of Blowing in The Wind in terms of SFG, aiming at providing a new perspective on the in-terpretation of the song.
基金financially supported by the National Natural Science Foundation of China (Nos.51974023 and52374321)the funding of State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing,China (No.41620007)。
文摘The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error±300 m^(3)is 96.67%;determination coefficient (R^(2)) and root mean square error (RMSE) are0.6984 and 150.03 m^(3), respectively. The oxygen blow time prediction hit ratio within the error±0.6 min is 89.50%;R2and RMSE are0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.
文摘This article discusses and analyzes the law of nitrogen increase in liquid steel and the main factors affect-ing the nitrogen increasing of molten steel,through the way of adding nitrogen to molten steel by bottom blowing nitrogen gas in LF refining process.It is considered that the main factors affecting the nitrogen increasing instability of molten steel are the initial temperature of LF refining,nitrogen relative element,surface active elements[O]and[S]of steel liquid,and bottom blowing rate of ladle.The large-scale production practice shows that T[O]not more than 50×10-6 and[S]is not more than 0.020 in LF refining at the initial temperature of not less than 1570.The liquid steel nitrogen enrichment test is carried out by ladle bottom blowing nitrogen gas after 20 min of refining,the flow rate is set as(6.0~7.0)NL/min per ton,and it is turned to 2 NL/min at 6 min before the end of refining,the nitrogen increasing rate of liquid steel is basically stable at(5~6)×10-6 per minute.
基金financially supported by the National Natural Science Foundation of China(No.51704062)the Fundamental Research Funds for the Central Universities,China(No.N2025019)。
文摘A three-dimensional mathematical model was developed to investigate the effect of gas blowing nozzle angles on multiphase flow,circulation flow rate,and mixing time during Ruhrstahl-Heraeus(RH) refining process.Also,a water model with a geometric scale of 1:4 from an industrial RH furnace of 260 t was built up,and measurements were carried out to validate the mathematical model.The results show that,with a conventional gas blowing nozzle and the total gas flow rate of 40 L·min^(-1),the mixing time predicted by the mathematical model agrees well with the measured values.The deviations between the model predictions and the measured values are in the range of about 1.3%–7.3% at the selected three monitoring locations,where the mixing time was defined as the required time when the dimensionless concentration is within 3% deviation from the bath averaged value.In addition,the circulation flow rate was 9 kg·s^(-1).When the gas blowing nozzle was horizontally rotated by either 30° or 45°,the circulation flow rate was found to be increased by about 15% compared to a conventional nozzle,due to the rotational flow formed in the up-snorkel.Furthermore,the mixing time at the monitoring point 1,2,and 3 was shortened by around 21.3%,28.2%,and 12.3%,respectively.With the nozzle angle of 30° and 45°,the averaged residence time of 128 bubbles in liquid was increased by around 33.3%.
基金The authors wish to express thanks to the National Natural Science Foundation of China(51904278)Shanxi Province Key R&D Program High-tech Project(201903D121093)+1 种基金Major Science and Technology Projects of Shanxi Province(20181101002)General Project of Natural Science Foundation of Shanxi Province(20210302123218)for supporting this work.
文摘A numerical model of an iron bath smelting reduction furnace with side-bottom combined blowing was established to study the influence of blowing arrangements on the stirring effect of the molten pool,and the accuracy of numerical simulation was verified by water model experiment.By comparing the flow field of molten pool with single nozzle,double nozzles(symmetrical and asymmetrical),and four nozzles(symmetrical and asymmetrical),the proportion of dead zone,average turbulent kinetic energy,and mixing time,the results show that asymmetrical bottom blowing is better than symmetrical bottom blowing,and the effect of double nozzles bottom blowing was better than that of four nozzles bottom blowing.The mixing effect is the worst under the condition of single nozzle.When the bottom blowing is asymmetrical with double nozzles,the mixing time is the shortest.Under the condition of double nozzles asymmetrical bottom blowing,when the insertion angle and depth of side lance are larger and deeper,the velocity streamline of molten slag layer is denser and the value is larger;meanwhile,the reflux of molten iron layer is larger,the proportion of dead zone is smaller,and the whole molten pool is fully stirred.When the insertion depth of the side lance is deeper,the gas holdup in the molten pool is greater and the stirring of the molten pool is more intense,while the insertion angle has little effect on the gas holdup.By comparing the influence of different side blowing conditions on the slag layer,it is found that the slag layer is divided into two layers by double-layer side lance,with the critical surface of the slag layer at about 200-260 mm from the bottom,and the insertion depth of the lower side lance has a greater influence on the layering of the slag.
文摘Through systematical experiment design, the physical blowing agent(PBA) mass loss of bio-based polyurethane rigid foam(PURF)in the foaming process was measured and calculated in this study, and different eco-friendly PBA mass losses were measured quantitatively for the first time. The core of the proposed method is to add water to replace the difference, and this method has a high fault tolerance rate for different foaming forms of foams. The method was proved to be stable and reliable through the standard deviations σ1and σ2for R1(ratio of the PBA mass loss to the material total mass except the PBA) and R2(ratio of the PBA mass loss to the PBA mass in the material total mass) in parallel experiments. It can be used to measure and calculate the actual PBA mass loss in the foaming process of both bio-based and petroleumbased PURF. The results show that the PBA mass loss in PURF with different PBA systems is controlled by its initial mass content of PBA in PU materials ω. The main way for PBA to dissipate into the air is evaporation/escape along the upper surface of foam. This study further reveals the mechanism of PBA mass loss: the evaporation/escape of PBA along the upper surface of foam is a typical diffusion behavior. Its spread power comes from the difference between the chemical potential of PBA in the interface layer and that in the outside air. For a certain PURF system, R1has approximately linear relationship with the initial mass content of PBA in PU materials ω, which can be expressed by the functional relationship R1= kω, where k is a variable related to PBA’s own attributes.
基金funded by projects“Smart Materials,Photonics,Technologies and Engineering Ecosystem(MOTE)”(Contract No.VPP-EM-FOTONIKA-2022/1-0001)“Bio-Based Cryogenic Insulation for Aerospace Application(BioSpace)”(Contract No.4000135271/21/NL/SC).
文摘Cryogenic insulation material rigid polyurethane(PU)foams were developed using bio-based and recycled feedstock.Polyols obtained from tall oil fatty acids produced as a side stream of wood biomass pulping and recycled polyethylene terephthalate were used to develop rigid PU foam formulations.The 4th generation physical blowing agents with low global warming potential and low ozone depletion potential were used to develop rigid PU foam cryogenic insulation with excellent mechanical and thermal properties.Obtained rigid PU foams had a thermal conductivity coefficient as low as 0.0171 W/m·K and an apparent density of 37-40 kg/m^(3).The developed rigid PU foams had anisotropic compression strength properties,which were higher parallel to the foaming direction.Moreover,the compression strength was also influenced by the type of applied bio-based polyol.The bio-based polyols with higher OH group functionality delivered higher crosslinking density of polymer matrix;thus,the mechanical properties were also higher.The mechanical strength of the foams increased when materials were tested at liquid nitrogen temperature due to the stiffening of the polymer matrix.The thermal properties of the developed materials were determined using differential scanning calorimetry,dynamic mechanical analysis,and thermogravimetric analysis methods.Lastly,the developed rigid PU foams had good adhesion to the aluminium substrate before and after applying cyroshock and an excellent safety coefficient of 4-5.Rigid PU foams developed using Solstice LBA delivered adhesion strength of~0.5 MPa and may be considered for application as cryogenic insulation in the aerospace industry.
文摘Unusual head trauma is rare with various mechanisms of occurrence. The injuries can be similar to those of road accidents but sometimes with significant complexities. The objective was to determine the frequency of this pathology in our practice, describe the different mechanisms and report the craniocerebral lesions caused by this type of trauma. Materials and Method: This was a descriptive study with retrospective collection spread over a period of 3 years. After selecting the files, the patients and/or their companions were contacted by telephone to inquire about them and then returned to the consultation for reassessment. Disease history and information were obtained from patients’ medical records. Result: The frequency of this pathology was 1.78% and his incidence was 0.4 cases per month. The average age of the patients was 13.47 years. All the victims were male. 41.17% of patients were in school. The mechanisms of trauma were the hoof blow 47.1%, the horn blow 29.4% and the stone blow 11.7% respectively. 23.5% of patients were confused and 11.7% children were in coma. One patient presented an anisocoria. The motor deficit was present in 5 cases. CT-scan made it possible to highlight a skull depressing fracture 58.8% and confirm a craniocerebral wound in 35.3%. The average time between patient admission to hospital and completion of surgery was 24.5 hours. The surgery had consisted of the trimming of cranio-cerebral wounds, exploration, duroplasty and lifting of skull depressing fracture. After 15 months of follow-up, the evolution was favorable in 53.3%, the morbidity was 33.4% and the mortality 17.6%. Conclusion: These are rare but serious conditions because they are fatal and disabling. An early and multidisciplinary management can hope to have a good favorable.
基金Projects(51104080,u1137601) supported by the National Natural Science Foundation of ChinaProject(2009CD027) supported by the Natural Science Foundation of Yunnan Province,ChinaProject(14118557) supported by the Personnel Training Foundation of Kunming University of Science and Technology,China
文摘Gas blowing is a valid method to remove the impurities from metallurgical grade silicon(MG-Si) melt.The thermodynamic behavior of impurities Fe,Al,Ca,Ti,Cu,C,B and P in MG-Si was studied in the process of O2 blowing.The removal efficiencies of impurities in MG-Si were investigated using O2 blowing in ladle.It is found that the removal efficiencies are higher than 90% for Ca and Al and nearly 50% for B and Ti.The morphology of inclusions was analyzed and the phases Al3Ni,NiSi2 and Al3Ni were confirmed in MG-Si by X-ray diffraction.It was found that SiB4 exists in Si?B binary system.The chemical composition of inclusions in MG-Si before and after refining was analyzed by SEM-EDS.It is found that the amount of white inclusion reduces for the removal of most Al and Ca in the forms of molten slag inclusion and the contents of Fe,Ni and Mn in inclusion increase for their inertia in silicon melt with O2 blowing.
文摘Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments.It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence inhibitor.It dramatically increases the peak concentration time,and greatly decreases the dead volume,and reduces the minimum residence time.The gas blowing location,gas flow rate,and porous plug area greatly influence the flow characteristics in the tundish; the gas blowing location near the baffle,smaller gas flow rate,and smaller porous plug area are better for improving the fluid flow characteristics.Using gas blowing can reduce the difference of flows at the middle outlets and side outlets for the multi-strand tundish.Bubbles produced by gas blowing can absorb small inclusions and provide the condition for inclusion collision and aggregation.Therefore,introducing gas blowing into a tundish and combining the turbulence inhibitor can improve inclusion floating and removal,and the cleanness of molten steel can be advanced.
基金Project(51676211)supported by the National Natural Science Foundation of ChinaProject(2015zzts044)supported by Innovation Foundation for Postgraduate of Central South University,ChinaProject(2017SK2253)supported by the Key R&D Plan of Hunan Province,China
文摘The bubble growth and detachment behavior in the bottom blowing process were investigated. Four multi-hole nozzle configurations with different opening ratios were assessed experimentally using high-speed photography and digital image processing. For these configurations, the experiments reveal that the bubble growth consists of a petal-like stage, an expansion stage and a detachment stage. The petal-like shape is qualitatively described through the captured images, while the non-spherical bubbles are analyzed by the aspect ratio. The bubble size at the detachment is quantified by the maximum caliper distance and the bubble equivalent diameter. Considering the dependence on the opening ratio, different prediction models for the ratio of maximum caliper distance to hydraulic diameter of the nozzle outlet and the dimensionless bubble diameter are established. The comparative analysis results show that the proposed prediction model can accurately predict the bubble detachment size under the condition of multi-hole nozzles.
文摘The effects of operation parameters of combined blowing converter on the volumetric mass transfer coefficient between slag and steel are studied with a cold model with water simulating steel, oil simulating slag and benzoic acid as the transferred substance between water and oil. The results show that, with lance level of 2.1m and the top blowing rate of 25000Nm3/h, the volumetric mass transfer coefficient changes most significantly when the bottom blowing rate ranges from 384 to 540Nm3/h. The volumetric mass transfer coefficient reaches its maximum when the lance level is 2.1m, the top blowing rates is 30000Nm3/h, and the bottom blowing rate is 384Nm3/h with tuyeres located symmetrically at 0.66D of the converter bottom.
文摘Currently, many studies have been made for years on dimensions of pneumatic nozzle, which influence the flow characteristic of blowing system. For the purpose of outputting the same blowing force, the supply pressure could be reduced by decreasing the ratio of length to diameter of nozzle. The friction between high speed air and pipe wall would be reduced if the nozzle is designed to be converging shape comparing with straight shape. But the volume flow and pressure, discussed in these studies, do not describe energy loss of the blowing system directly. Pneumatic power is an innovative principle to estimate pneumatic system’s energy consumption directly. Based on the above principle, a pulse blowing method is put forward for saving energy. A flow experiment is carried out, in which the high speed air flows from the pulse blowing system and continuous blowing system respectively to a plate with grease on top. Supply pressure and the volume of air used for removing the grease are measured to calculate energy consumption. From the experiment result, the pulse blowing system performs to conserve energy comparing with the continuous blowing system. The frequency and duty ratio of pulse flow influence the blowing characteristic. The pulse blowing system performs to be the most efficient at the specified frequency and duty ratio. Then a pneumatic self-oscillated method based on air operated valve is put forward to generate pulse flow. A simulation is made about dynamic modeling the air operated valve and calculating the motion of the valve core and output pressure. The simulation result verifies the system to be able to generate pulse flow, and predicts the key parameters of the frequency and duty ratio measured by experiment well. Finally, on the basis of simplifying and solution of the pulse blowing system’s mathematic model, the relationship between system’s frequency duty ratio and the dimensions of components is simply described with four algebraic equations. The system could be designed with specified frequency and duty ratio according to the four equations. This study provides theoretical basis for designing energy-saving air blowing system.
基金funded by the National Natural Science Foundation of China(Grant Nos.913252034100124041071227)
文摘Blowing snow is an important part of snow hydrologic processes in mountainous region, however the related researches were rare for the Qilian mountainous region where blowing snow is frequent. Using the observation dataset in 2008 snow season in Binggou wa- tershed in Qilian mountainous region, we systematically studied the energy and mass processes of blowing snow by field observation and model simulation. The results include the analysis of snow observation, the occurrence probability of blowing snow, blowing snow transport and blowing snow sublimation. It was found that blowing snow was obvious in high altitude region (4,146 m), the snow redislribution phenomena was remarkable. In Yakou station in the study region, blowing snow was easily occurred in midwinter and early spring when no snowmelt, the blowing snow transport was dominated in this period; when snowmelt beginning, the occur- rence probability of blowing snow decreased heavily because of the increasing air temperature, melt, and refrozen phenomena. The blowing snow sublimation accounted for 41.5% of total snow sublimation at Yakou station in 2008 snow season.
基金Foundation item:the Natural Science Foundation of Jiangsu Province(BK97056109)
文摘A vorticity-velocity method was used to study the incompressible viscous fluid flow around a circular cylinder with surface suction or blowing. The resulted high order implicit difference equations were effeciently solved by the modified incomplete LU decomposition conjugate gradient scheme ( MILU-CG). The effects of surface suction or blowing' s position and strength on the vortex structures in the cylinder wake, as well as on the drag and lift forces at Reynoldes number Re = 100 were investigated numerically. The results show that the suction on the shoulder of the cylinder or the blowing on the rear of the cylinder can effeciently suppress the asymmetry of the vortex wake in the transverse direction and greatly reduce the lift force; the suction on the shoulder of the cylinder, when its strength is properly chosen, can reduce the drag force significantly, too.
基金the National Natural Science Foundation(Granted Number 50276010)
文摘The theoretical model of the flow field of the dual slot die in melt blowing process is founded. The model is solved numerically with finite difference method. The distributions of the air velocity component in x direction along x-axis and y-axis and the air temperature distributions along x-axis and y-axis are obtained via numerical computation. The computation results coincide with the experimental data given by Harphain and Shambaugh. The distributions of the air velocity and air temperature are introduced into the air drag model of melt blowing. The model prediction of the fiber diameter agrees with the experimental data well.
基金The authors would like to express their thanks for the support by the National Natural Science Foundation of China (No.51734003).
文摘Nowadays, in China, the bottom-blowing technique plays an important role in accelerating the molten bath stirring and promoting the metallurgical reactions in electric arc furnace (EAF) steelmaking. The innovations of bottom-blowing technologies in EAF steelmaking were reviewed. The optimized bottom-blowing arrangement in EAF based on the furnace structure and the position of electrodes was introduced, and the fluid flow characteristics of EAF molten bath with bottomblowing were analyzed. Furthermore, bottom-blowing CO2 in EAF can facilitate the carbon-oxygen reaction reaching equilibrium and decrease the content of nitrogen in molten steel due to its special metallurgical properties. Pulsating bottom-blowing in EAF can effectively improve the molten bath stirring through the action of the unsteady bottom blowing gas streams, which could make the fluid flow field more disorderly than the steady bottom-blowing. And submerged O2 injection with CO2 in EAF can noticeably strengthen the EAF molten bath stirring, increase the production efficiency and improve the molten steel quality.
文摘Biocomposite films prepared with melt compounding and film blowing have become a new trend in plastic research to deliver more eco-friendly packages.Polylactic acid(PLA)was melt compounded with minimally processed date palm leaf fiber(DPLF)and converted into films by blown film extrusion.The compounding was done in order to enhance the film mechanical properties in one hand,and to decrease the film production cost in the other hand.In this present study,a reference PLA film and films with 1%,2%,and 5%of DPLF(weight%)were produced with different process parameters.The spatial variations in films thickness and lay flat width indicate that the addition of DPLF up to 2%enhances the bubble stability for the tested process parameters.However,the composite with 5%DPLF shows nearly the same processability window as the neat PLA.The structural and mechanical characterizations of films suggest a reinforcing effect of the PLA matrix up to 2%of fiber(with an optimum at 1%).Larger DPLF loading leads to depressed and more anisotropic mechanical properties,related to an increased density of defects at the fiber-PLA fragile interface and to a DPLF-induced enhanced PLA thermal degradation and amorphous phase orientation.
文摘We have tried to prepare the microcapsules containing water droplets stabilized with solid powder by utilizing the (W/O)/W emulsion. The water droplets as core material were stabilized in the monomer droplets with titanium dioxide (TiO2) as a particulate surfactant. Before adding the TiO2 powder into the monomer phase, the powder was modified with triethoxyvinylsilane to adjust the degree of hydrophobicity and to promote adhesion on the interface between the inner water phase and the monomer phase in the (W/O) emulsion. It was investigated how the degree of hydrophobicity of the TiO2 powder affected the stability of water droplets in the (W/O) emulsion and the (W/O) droplets in the (W/O)/W emulsion. Moreover, the microcapsule diameters were measured before and after the expansion operation where the water droplets microencapsulated were applied as a blowing agent. The expansion ratio was increased with increase in the stability of the water droplets and the amount of water microencapsulated.