The increasing occurrence of sinkholes caused by water main bursts has attracted significant research attention in recent years.This study addresses the gap in evaluating soil blowout stability resulting from water ma...The increasing occurrence of sinkholes caused by water main bursts has attracted significant research attention in recent years.This study addresses the gap in evaluating soil blowout stability resulting from water main failures by investigating the three-dimensional stability of blowouts with circular,hemispherical,and spherical openings.Advanced finite element limit analysis(FELA)combined with adaptive meshing is employed to analyze critical factors,including soil cover depth,surcharge pressure,and internal water pressure,that contribute to blowout failure.In addition,dimensionless ratios are used throughout the paper to assess the influence of these factors.Numerical findings are rigorously validated,ensuring reliability and accuracy.Practical design charts are provided to accommodate a wide range of design scenarios,offering valuable guidance for engineers.This study introduces a pioneering sinkhole simulation methodology,leading to the understanding of three-dimensional blowout stability mechanisms.展开更多
●AIM:To explore the combined application of surgical navigation nasal endoscopy(NNE)and three-dimensional printing technology(3DPT)for the adjunctive treatment of orbital blowout fractures(OBF).●METHODS:Retrospectiv...●AIM:To explore the combined application of surgical navigation nasal endoscopy(NNE)and three-dimensional printing technology(3DPT)for the adjunctive treatment of orbital blowout fractures(OBF).●METHODS:Retrospective analysis was conducted on the data of patients with OBF who underwent surgical treatment at the Affiliated Eye Hospital of Nanchang University between July 2012 and November 2022.The control group consisted of patients who received traditional surgical treatment(n=43),while the new surgical group(n=52)consisted of patients who received NNE with 3DPT.The difference in therapeutic effects between the two groups was evaluated by comparing the duration of the operation,best corrected visual acuity(BCVA),enophthalmos difference,recovery rate of eye movement disorder,recovery rate of diplopia,and incidence of postoperative complications.●RESULTS:The study included 95 cases(95 eyes),with 63 men and 32 women.The patients’age ranged from 5 to 67y(35.21±15.75y).The new surgical group and the control group exhibited no statistically significant differences in the duration of the operation,BCVA and enophthalmos difference.The recovery rates of diplopia in the new surgical group were significantly higher than those in the control group at 1mo[OR=0.03,95%CI(0.01–0.15),P<0.0000]and 3mo[OR=0.11,95%CI(0.03–0.36),P<0.0000]postoperation.Additionally,the recovery rates of eye movement disorders at 1 and 3mo after surgery were OR=0.08,95%CI(0.03–0.24),P<0.0000;and OR=0.01,95%CI(0.00–0.18),P<0.0000.The incidence of postoperative complications was lower in the new surgical group compared to the control group[OR=4.86,95%CI(0.95–24.78),P<0.05].●CONCLUSION:The combination of NNE and 3DPT can shorten the recovery time of diplopia and eye movement disorder in patients with OBF.展开更多
Gas blowout occurred during drilling may cause catastrophic environmental hazards and economic losses.It is thus one of the important tasks to accurately determine the gas blowout volume so that an effective rescue pl...Gas blowout occurred during drilling may cause catastrophic environmental hazards and economic losses.It is thus one of the important tasks to accurately determine the gas blowout volume so that an effective rescue plan can be worked out in case of gas blowout.In this paper,a numerical method for estimating the gas blowout volume was presented based on the Bernoulli Equation and the corresponding software was programmed.In the process of numerical estimation,the velocity distribution of the blowoutflame characterized by the axisymmetric laminarflow was investigated through an analysis of the dynamicflowing features of the gas gusher,and the relationship between the gas production of a well and the height of the blowoutflame was then analyzed with the Bernoulli Equation to obtain the numerical results of the gas blowout volume.The results were then compared with those laboratory measurements,and the software was revised based on the comparisons.Some conclusions were drawn.First,when the spout shape of a gusher is constant,the gas production is proportional to the height of the blowoutflame,and inversely proportional to the gas kinematic viscosity,the stoichiometric ratio factor and the oxygen concentration.Second,the errors be-tween the results estimated using the revised software and the laboratory measurements are within the allowable range,and the software can automatically generate a report.In a word,the method and software presented in this paper can be an effective technique for preparing a sound and safe rescue plan in case of gas blowout,and is of great significance in relieving the hazards of a well with uncontrolled blowout.展开更多
This paper establishes an evaluation model of the customer satisfaction index for the wellhead blowout preventers of China＇s petroleum industry based on evaluation models of the customer satisfaction index at home an...This paper establishes an evaluation model of the customer satisfaction index for the wellhead blowout preventers of China＇s petroleum industry based on evaluation models of the customer satisfaction index at home and aboard, and by considering the consuming situation in China and the features of the China＇s petroleum industry. For the existence of： （1） multiple correlations among the factors in the model; （2） the variables need to be explained, but that are hard to observe; （3） the customer satisfaction degree of observation variables appears the shape of skewness or two or three peaks, the correlations between the satisfaction index and its factors cannot be described by common multiple regression. This paper uses a partial least squares （PLS） method based on principal components and typical correlative analysis to solve the problem. When PLS is used in the model of the customer satisfaction index of the wellhead blowout preventers, the latent variables and the explanation degree coefficient of the manifest variable to the corresponding latent variables are estimated by PLS path analysis, and the influencing coefficient among the latent variables in the model is estimated by PLS regression analysis. PLS is also be used to calculate and analyze the model and disclose the correlations among the structural variables as well as the correlation between structural variables and its corresponding observation variables, evaluating results of which provide useful information for petroleum industry to improve the product quality and to the enhancement of the customer satisfaction to the product.展开更多
In this study, we applied a two-phase flow model to simulate water and sand blowout processes when penetrating shallow water flow(SWF) formations during deepwater drilling. We define ‘sand' as a pseudo-component ...In this study, we applied a two-phase flow model to simulate water and sand blowout processes when penetrating shallow water flow(SWF) formations during deepwater drilling. We define ‘sand' as a pseudo-component with high density and viscosity, which can begin to flow with water when a critical pressure difference is attained. We calculated the water and sand blowout rates and analyzed the influencing factors from them, including overpressure of the SWF formation, as well as its zone size, porosity and permeability, and drilling speed(penetration rate). The obtained data can be used for the quantitative assessment of the potential severity of SWF hazards. The results indicate that overpressure of the SWF formation and its zone size have significant effects on SWF blowout. A 10% increase in the SWF formation overpressure can result in a more than 90% increase in the cumulative water blowout and a 150% increase in the sand blowout when a typical SWF sediment is drilled. Along with the conventional methods of well flow and pressure control, chemical plugging, and the application of multi-layer casing, water and sand blowouts can be effectively reduced by increasing the penetration rate. As such, increasing the penetration rate can be a useful measure for controlling SWF hazards during deepwater drilling.展开更多
AIM: To investigate the effect of repair materials for orbital blowout fractures on the occurrence of postoperative complications. METHODS: The clinical data and follow-up data of 54 subjects with orbital blowout frac...AIM: To investigate the effect of repair materials for orbital blowout fractures on the occurrence of postoperative complications. METHODS: The clinical data and follow-up data of 54 subjects with orbital blowout fractures were retrospectively analyzed. The study was divided into three groups according to the used repair materials: titanium mesh(16 cases), Medpor(12 cases), and Medpor titanium mesh(26 cases). All test data were analyzed using the SPSS version 23.0 statistical software. The mean age and duration of disease between the groups were compared through oneway analysis of variance. The Chi-square(χ~2) test was used to compare the number of males and females, different fracture types, and different surgical approaches among groups. The χ~2 test was used to compare the frequencies for complications in each group.RESULTS: The baseline characteristics of age and gender in each group were matched(F=1.763, P=0.172;χ~2=0.026, P=0.987). In addition, there was no difference in the type of fracture and surgical approach(χ~2=0.460, P=0.977;χ~2=0.691, P=0.952), or the incidence of complications(χ~2=0.081, P=0.960) between the three groups. CONCLUSION: Although there is no difference in effect of various repair materials on the incidence of complications, the effect of repair materials on postoperative complications of orbital blowout fractures should not be ignored.展开更多
The land coverage pattern changes for the past 50 years in a typical region of the Hulun Buir Sandy Grassland were interpreted and analyzed based on a series of remote sensing images in 1959, 2002, 2004 and 2009. The ...The land coverage pattern changes for the past 50 years in a typical region of the Hulun Buir Sandy Grassland were interpreted and analyzed based on a series of remote sensing images in 1959, 2002, 2004 and 2009. The temporal and spatial changes of landscape patterns were revealed and the driving forces were analyzed. The results show that all land coverage types had large variable amplitudes. The grassland area decreased, whereas other areas incleased. Owing to implementation of artificial sand fixation from 2004 to 2009, the areas of flowing blowouts and depositional area decreased by 71,369 and 128,835 m2, respectively. The average patch area reduced, but the number of blowouts increased, fractal dimension increased, and blowout structure became complex. The fragmentation index increased, whereas contagion index decreased. Driving force analysis shows that human factors such as overglazing are slightly larger than natural factors of increased temperature and decreased precipitation展开更多
The Lean Blowout(LBO)limit is crucial for the aircraft engines.The semi-empirical(such as Lefebvre’s LBO model and Flame Volume(FV)model),numerical and hybrid methods are widely utilized for the LBO limit quick predi...The Lean Blowout(LBO)limit is crucial for the aircraft engines.The semi-empirical(such as Lefebvre’s LBO model and Flame Volume(FV)model),numerical and hybrid methods are widely utilized for the LBO limit quick prediction.An innovative hybrid method based on the FV concept is proposed.This method can be classified as a semi-empirical/physical based hybrid prediction method.In this hybrid method,it is assumed that the flame volume varies nearly linearly with the fuel/air ratio near the LBO.The flame volume is obtained directly by the numerical simulation using the threshold value of the visible flame boundary as 900 K.Then the final LBO limits is determined by the FV model.On the premise of keeping the good generality of prediction,the hybrid method based on the FV concept can further improve the prediction accuracy.The comparison with the prediction of the existing available methods on fifteen combustors shows that the hybrid method based on the FV concept achieves better prediction accuracy.The prediction uncertainties between the experimental results and the predicted values by the hybrid method based on the FV concept are within about±10%.展开更多
The occurrence of Lean Blowout(LBO)is a disadvantage that endangers a stable operation of gas turbines.A determination of LBO limits is essential in the design of gas turbine combustors.A semiempirical model is one of...The occurrence of Lean Blowout(LBO)is a disadvantage that endangers a stable operation of gas turbines.A determination of LBO limits is essential in the design of gas turbine combustors.A semiempirical model is one of the most widely used methods to predict LBO limits.Among the existing semiempirical models for predicting LBO limits,Lefebvre’s LBO model and the Flame Volume(FV)model are particularly suitable for gas turbine combustors.On the basis of Lefebvre’s and FV models,the concept of effective evaporation efficiency is introduced in this paper,and a Flame Volume-Evaporation Efficiency(FV-EE)model is derived and validated.LBO experiments are carried out in a model combustor with 23 different structures and 10 different sprays.The prediction uncertainty of the FV-EE model is less than±13%for all of these 33 structures and sprays,compared with±50%for the FV model and±60%for Lefebvre’s model.Furthermore,the prediction uncertainty of the FV-EE model is also less than±13%for other combustors from available literature.展开更多
AIM:To assess the role of orthoptics in referring patients with orbital floor blowout fracture(OFBF)for conservative or surgical treatment and based on the results,to propose a scoring system for such decision making....AIM:To assess the role of orthoptics in referring patients with orbital floor blowout fracture(OFBF)for conservative or surgical treatment and based on the results,to propose a scoring system for such decision making.METHODS:A retrospective analysis of 69 patients with OFBF was performed(35 treated conservatively,34 surgically).The role of orthoptics in referring to surgery or conservative treatment was retrospectively evaluated,the factors with the highest significance for decision making were identified,and a scoring system proposed using Logistic regression.RESULTS:According to defined criteria,the treatment was unsuccessful in 2(6%)surgically treated and only in one(3%)conservatively treated patient.The proposed scoring system includes the defect size and several values resulting from the orthoptic examination,the elevation of the eyebulb measured on Lancaster screen being the most significant.CONCLUSION:The study demonstrates the benefits of orthoptic examination when making decisions on conservative or surgical treatment and for diagnosing ocular motility disorder(with or without binocular diplopia)in OFBF patients.The proposed scoring system could,following verification in a prospective study,become a valuable adjunctive tool.展开更多
The tire blowout or severe leakage real-time monitoring is one of key technologies for developing a tire blowout automatic braking system.An indirect real-time monitoring method to fuse analyses of tire vibration and ...The tire blowout or severe leakage real-time monitoring is one of key technologies for developing a tire blowout automatic braking system.An indirect real-time monitoring method to fuse analyses of tire vibration and effective radius is provided in this paper,and a monitoring system is developed.The calibration and related test results showthat the system can detect the tire blowout in low and middle vehicle speeds and the severe leakage in all speeds timely and accurately.展开更多
Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative ...Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation.The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multiswirl staged combustor equipped with an airblast injector.A set of hardware and control system was developed to realize a user-defined fuel supply law.High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow.Partical Image Velocimetry(PIV)and Planar Mie(PMie)scattering were used to acquire the flow fields and spray fields under non-reacting conditions.Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases.With an increase of the fuel decreasing rate,the exhaust temperature before flame extinction increases,and the LBO Fuel-to-Air-Ratio(FAR)decreases.The time evolution of the integral CH*intensity conforms to a linear function during the LBO process.Proper Orthogonal Decomposition(POD)was used to analyze the dynamic characteristics of lean-burn flames.Under different fuel decreasing rates and pressure drops of the injector,flames close to LBO present similar modal spatial distributions,alternately appearing axial,radial,high-order axial,and high-order radial oscillations.展开更多
Gas blowout is one of the major hazard in petroleum field which normally damages the gas bearing geologic formation, structure, local tectonic setting, environment and so on. In Bangladesh, there have been three well ...Gas blowout is one of the major hazard in petroleum field which normally damages the gas bearing geologic formation, structure, local tectonic setting, environment and so on. In Bangladesh, there have been three well known gas blowouts. Among them, the most dangerous gas well blowout took place on 8 January 2005 in Sunamganj district when chattak-2 (also known as Tengratila) gas field was drilled. As a result, the surrounding area is facing various problems among them water is the top of the list. From this point of view, the present study has been considered to find the impact of blowout on water around the gas blowout area. In this regard, the water samples (some are very near and some are away from the well) are collected and analyzed in the laboratory following the standard method. Some physical and chemical parameters of water such as pH, turbidity, EC, total solids, dissolved solids, suspended solids, manganese ion, calcium ion, magnesium, iron, chloride and total hardness have measured where without turbidity, manganese and iron, all are still in tolerable state for all purposes and ranging within standard limit based on WHO, EU and EQS for Bangladesh. The quality of the near well tube wells water is much decreased than far away tube wells water which might be the direct or indirect influence of the blowout incident around the area.展开更多
Fractured carbonate reservoirs are susceptible to blowout and lost circulation during drilling,which not only restricts drilling speed,but also poses big threat to well control.Moreover,there are few technical means a...Fractured carbonate reservoirs are susceptible to blowout and lost circulation during drilling,which not only restricts drilling speed,but also poses big threat to well control.Moreover,there are few technical means available to reconstruct pressure balance in the borehole.Accordingly,the fine managed pressure drilling was used in the drilling of Well GS19 in the Qixia Formation with super-high pressure and narrow density window,which is a success:①back pressure in the annular spaces will be adjusted to maintain a slightly over-balanced bottom-hole hydraulic pressure,and fluid level in the circulation tank will be kept in a slight dropping state to ensure that natural gas in the formation would not invade into the borehole in a massive volume;②inlet drilling fluid density will be controlled at around 2.35 g/cm^(3),back pressures in the annular be maintained at 2-5 MPa,and bottom-hole pressure equivalent circulation density be controlled at 2.46-2.52 g/cm^(3);③during managed pressure drilling operations,if wellhead pressure exceeds or expects to exceed 7 MPa,semi-blind rams will be closed.Fluids will pass through the choke manifold of the rig to the choke manifold specifically for pressure control before entering gas/liquid separators to discharge gas;④during tripping back pressure will be kept at less than 5 MPa,volume of injected drilling fluid will be higher than the theoretical volume during tripping out,whereas the volume of returned drilling fluid will be higher than the theoretical volume during the out-tripping.This technique has been applied successfully in the drilling of the Qixia Formation,Liangshan Formation and Longmaxi Formation with a total footage of 216.60 m,as a good attempt in complicated wells with both blowout and lost circulation risks,which can provide valuable experiences and guidance for handling similar complexities in the future.展开更多
BACKGROUND Carotid blowout syndrome(CBS)refers to rupture of the extracranial carotid artery and its branches;as a severe complication,it usually occurs after surgery or radiotherapy for malignant tumours of the head ...BACKGROUND Carotid blowout syndrome(CBS)refers to rupture of the extracranial carotid artery and its branches;as a severe complication,it usually occurs after surgery or radiotherapy for malignant tumours of the head and neck.We present a case of CBS caused by chronic infection of the external carotid artery(ECA).In this case,we did not find any evidence of head and neck tumours.CASE SUMMARY A 42-year-old man was referred to the Emergency Department with a complaint of a lump found on the left side of his neck with pain and fever for 4 d.We diagnosed the condition as neck infection with abscess formation based on physical examination,routine blood examination,ultrasound examination and plain computed tomography(CT)and decided to perform emergency surgery.During the operation,30 mL of grey and smelly pus was drained from the deep surface of the sternocleidomastoid muscle.The second day after the operation,the patient suddenly exhibited a large amount of haemoptysis and incision bleeding.The enhanced CT showed distal occlusion of the left ECA and irregular thickening of the broken ends of the artery encased in an uneven enhancement of soft tissue density.Infected ECA occlusion and rupture were considered.The patient was transferred to a vascular unit for transcatheter ECA embolization and recovered well.CONCLUSION Surgeons need to pay attention to vascular lesions caused by chronic infection that may develop into acute CBS.展开更多
A left ventricular (LV) free wall rupture is a highly lethal condition. A 75-year-old female who experienced chest pain was diagnosed as having an acute aortic dissection Stanford type A and underwent emergent surgery...A left ventricular (LV) free wall rupture is a highly lethal condition. A 75-year-old female who experienced chest pain was diagnosed as having an acute aortic dissection Stanford type A and underwent emergent surgery. Under cardiopulmonary bypass with LV venting through the right superior pulmonary vein, a proximal aortic stamp was formed. The patient was cooled, selective antegrade brain perfusion was performed, and a hemiarch repair was performed. After the patient was transferred to the intensive care unit, her blood pressure suddenly fell to 50 mmHg. She had a blowout rupture in the left ventricular anterolateral free wall. Since the bleeding hall was not large and the damage to the surrounding left ventricular tissue was not very wide, an off-pump multilayered sutureless repair was performed by using three layers of collagen fleece squares with fibrinogen-based impregnation (TachoComb;CSL Behring, Tokyo, Japan) and three layers of gelatin-resorcin-formalin glue reinforced by an equine pericardial patch (Xenomedica;Edwards Lifesciences, LLC, Irvine, CA). The blow-out rupture seemed to be caused by perioperative myocardial infarction generated by the compression of the left ventricular vent to the LV lateral wall. The patient was free from re-rupture or aneurysm enlargement. The thickness of the hemostatic material seemed to help control the bulging of the aneurysm and to prevent further LV aneurysm enlargement and re-rupture.展开更多
A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the ba...A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the basic motion law of the shear ram,combined its structural and operating parameters comprehensively,a model for solving the stress on the cutting edge was established corresponding to three stages(i.e.,shear point contact,cutting and penetrating the drill pipe)according to the wedge stress theory.Then,based on the novel shear ram,the numerical simulation and indoor shear experiment were carried out on CT90 coiled tubing to understand the variation laws of ram stress and shear point stress in the shearing process.And the following research results were obtained.First,when the shear point doesn't contact with the CT90 coiled tubing,the stress at the V-shaped angular center of the ram is the largest,and that at the shear point is extremely small.Second,when the shear point just touches the CT90 coiled tubing,the phenomenon of stress concentration occurs in the vicinity of the shear point of the ram cutting edge.Third,when the shear point cuts into the CT90 coiled tubing,the stress on the shear point and on both wedge edges is the largest,reaching the strength limit of the ram(1050MPa).Fourth,when the shear point enters the annulus after penetrating the CT90 coiled tubing,the ram stress on both sides of the junction between the cutting edge chamfer and the vertical plane is the largest.Fifth,After the CT90 coiled tubing is cut,crack damage occurs in the vicinity of the shear point of the ram cutting edge.In conclusion,the research results can better reflect the stress state of the ram cutting edge and its interaction with the drill pipe in the shearing process,and can provide an important reference for the design,manufacturing and the correct field application of shear rams.展开更多
The impact of turbine guide vanes on a three-dome combustor's lean blowout limit and blowout process was experimentally investigated.The parameters studied include the presence of the turbine guide vanes or not an...The impact of turbine guide vanes on a three-dome combustor's lean blowout limit and blowout process was experimentally investigated.The parameters studied include the presence of the turbine guide vanes or not and the blockage ratio of turbine guide vanes.It is shown that the presence of turbine guide vanes and an increase in the blockage ratio increase the lean blowout fuel-to-air ratio.From the images of flame spontaneous emission captured by the high-speed camera,the coupling of the combustor with turbine guide vanes can alter the sequence of the blowout among the three domes,and localized tiny flame lumps have been observed to develop into larger flames during lean blowout.However,flames within the combustor are established independently near blowout,and no reignition is observed.Furthermore,the turbine guide vanes have been found to shorten the duration of the blowout process and enhance the likelihood of blowout by increasing the lean fuel-to-air ratio.展开更多
The flame stability limit and propagation characteristics of a reverse-flow combustor without any flame-stabilized device were experimentally investigated under room temperature and pressure.The results indicate that ...The flame stability limit and propagation characteristics of a reverse-flow combustor without any flame-stabilized device were experimentally investigated under room temperature and pressure.The results indicate that it is feasible to stabilize the flame in the recirculation zones constructed by the impact jet flow from the primary holes and dilution holes.The flame projected area is mainly distributed in the recirculation zone upstream of the primary holes,whose presence and absence mark the ignition and extinction.During the ignition process,the growth rate and value of the flame projected area first increase and then decrease with the inlet velocity increasing from 9.4 m/s to 42.1 m/s.A rapid reduction followed by a slow reduction of ignition and lean blowout equivalence ratios is achieved by the increased inlet velocity.Then the non-reacting fluid structure in three sections was measured,and detailed velocity profiles were analyzed to improve the understanding of the flame stabilization mechanism.The results are conducive to the design of an ultra-compact combustor.展开更多
Lean combustion is environment friendly with low NO_(x)emissions providing better fuel efficiency in a combustion system.However,approaching towards lean combustion can make engines more susceptible to an undesirable ...Lean combustion is environment friendly with low NO_(x)emissions providing better fuel efficiency in a combustion system.However,approaching towards lean combustion can make engines more susceptible to an undesirable phenomenon called lean blowout(LBO)that can cause flame extinction leading to sudden loss of power.During the design stage,it is quite challenging for the scientists to accurately determine the optimal operating limits to avoid sudden LBO occurrences.Therefore,it is crucial to develop accurate and computationally tractable frameworks for online LBO prediction in low NO_(x)emission engines.To the best of our knowledge,for the first time,we propose a deep learning approach to detect the transition to LBO in combustion systems.In this work,we utilize a laboratory-scale swirl-stabilized combustor to collect acoustic data for different protocols.For each protocol,starting far from LBO,we gradually move towards the LBO regime,capturing a quasi-static time series dataset at different conditions.Using one of the protocols in our dataset as the reference protocol,we find a transition state metric for our trained deep learning model to detect the imminent LBO in other test protocols.We find that our proposed approach is more precise and computationally faster than other baseline models to detect the transition to LBO.Therefore,we endorse this technique for monitoring the operation of lean combustion engines in real time.展开更多
文摘The increasing occurrence of sinkholes caused by water main bursts has attracted significant research attention in recent years.This study addresses the gap in evaluating soil blowout stability resulting from water main failures by investigating the three-dimensional stability of blowouts with circular,hemispherical,and spherical openings.Advanced finite element limit analysis(FELA)combined with adaptive meshing is employed to analyze critical factors,including soil cover depth,surcharge pressure,and internal water pressure,that contribute to blowout failure.In addition,dimensionless ratios are used throughout the paper to assess the influence of these factors.Numerical findings are rigorously validated,ensuring reliability and accuracy.Practical design charts are provided to accommodate a wide range of design scenarios,offering valuable guidance for engineers.This study introduces a pioneering sinkhole simulation methodology,leading to the understanding of three-dimensional blowout stability mechanisms.
基金Supported by the Jiangxi Provincial Natural Science Foundation(No.20232ACB206030)。
文摘●AIM:To explore the combined application of surgical navigation nasal endoscopy(NNE)and three-dimensional printing technology(3DPT)for the adjunctive treatment of orbital blowout fractures(OBF).●METHODS:Retrospective analysis was conducted on the data of patients with OBF who underwent surgical treatment at the Affiliated Eye Hospital of Nanchang University between July 2012 and November 2022.The control group consisted of patients who received traditional surgical treatment(n=43),while the new surgical group(n=52)consisted of patients who received NNE with 3DPT.The difference in therapeutic effects between the two groups was evaluated by comparing the duration of the operation,best corrected visual acuity(BCVA),enophthalmos difference,recovery rate of eye movement disorder,recovery rate of diplopia,and incidence of postoperative complications.●RESULTS:The study included 95 cases(95 eyes),with 63 men and 32 women.The patients’age ranged from 5 to 67y(35.21±15.75y).The new surgical group and the control group exhibited no statistically significant differences in the duration of the operation,BCVA and enophthalmos difference.The recovery rates of diplopia in the new surgical group were significantly higher than those in the control group at 1mo[OR=0.03,95%CI(0.01–0.15),P<0.0000]and 3mo[OR=0.11,95%CI(0.03–0.36),P<0.0000]postoperation.Additionally,the recovery rates of eye movement disorders at 1 and 3mo after surgery were OR=0.08,95%CI(0.03–0.24),P<0.0000;and OR=0.01,95%CI(0.00–0.18),P<0.0000.The incidence of postoperative complications was lower in the new surgical group compared to the control group[OR=4.86,95%CI(0.95–24.78),P<0.05].●CONCLUSION:The combination of NNE and 3DPT can shorten the recovery time of diplopia and eye movement disorder in patients with OBF.
文摘Gas blowout occurred during drilling may cause catastrophic environmental hazards and economic losses.It is thus one of the important tasks to accurately determine the gas blowout volume so that an effective rescue plan can be worked out in case of gas blowout.In this paper,a numerical method for estimating the gas blowout volume was presented based on the Bernoulli Equation and the corresponding software was programmed.In the process of numerical estimation,the velocity distribution of the blowoutflame characterized by the axisymmetric laminarflow was investigated through an analysis of the dynamicflowing features of the gas gusher,and the relationship between the gas production of a well and the height of the blowoutflame was then analyzed with the Bernoulli Equation to obtain the numerical results of the gas blowout volume.The results were then compared with those laboratory measurements,and the software was revised based on the comparisons.Some conclusions were drawn.First,when the spout shape of a gusher is constant,the gas production is proportional to the height of the blowoutflame,and inversely proportional to the gas kinematic viscosity,the stoichiometric ratio factor and the oxygen concentration.Second,the errors be-tween the results estimated using the revised software and the laboratory measurements are within the allowable range,and the software can automatically generate a report.In a word,the method and software presented in this paper can be an effective technique for preparing a sound and safe rescue plan in case of gas blowout,and is of great significance in relieving the hazards of a well with uncontrolled blowout.
文摘This paper establishes an evaluation model of the customer satisfaction index for the wellhead blowout preventers of China＇s petroleum industry based on evaluation models of the customer satisfaction index at home and aboard, and by considering the consuming situation in China and the features of the China＇s petroleum industry. For the existence of： （1） multiple correlations among the factors in the model; （2） the variables need to be explained, but that are hard to observe; （3） the customer satisfaction degree of observation variables appears the shape of skewness or two or three peaks, the correlations between the satisfaction index and its factors cannot be described by common multiple regression. This paper uses a partial least squares （PLS） method based on principal components and typical correlative analysis to solve the problem. When PLS is used in the model of the customer satisfaction index of the wellhead blowout preventers, the latent variables and the explanation degree coefficient of the manifest variable to the corresponding latent variables are estimated by PLS path analysis, and the influencing coefficient among the latent variables in the model is estimated by PLS regression analysis. PLS is also be used to calculate and analyze the model and disclose the correlations among the structural variables as well as the correlation between structural variables and its corresponding observation variables, evaluating results of which provide useful information for petroleum industry to improve the product quality and to the enhancement of the customer satisfaction to the product.
基金Financial supports by the 973 National Research Project of China (No. 2015CB251201)the program for Changjiang Scholars and Innovative Research Team in University (‘PCSIRT’) (IRT_14R58)the Fundamental Research Funds for the Central Universities (No. 15CX0 5036A)
文摘In this study, we applied a two-phase flow model to simulate water and sand blowout processes when penetrating shallow water flow(SWF) formations during deepwater drilling. We define ‘sand' as a pseudo-component with high density and viscosity, which can begin to flow with water when a critical pressure difference is attained. We calculated the water and sand blowout rates and analyzed the influencing factors from them, including overpressure of the SWF formation, as well as its zone size, porosity and permeability, and drilling speed(penetration rate). The obtained data can be used for the quantitative assessment of the potential severity of SWF hazards. The results indicate that overpressure of the SWF formation and its zone size have significant effects on SWF blowout. A 10% increase in the SWF formation overpressure can result in a more than 90% increase in the cumulative water blowout and a 150% increase in the sand blowout when a typical SWF sediment is drilled. Along with the conventional methods of well flow and pressure control, chemical plugging, and the application of multi-layer casing, water and sand blowouts can be effectively reduced by increasing the penetration rate. As such, increasing the penetration rate can be a useful measure for controlling SWF hazards during deepwater drilling.
基金Supported by Jiangxi Provincial Science and Technology Department Key Research and Development Program Fund (No.20171BBG70096, No.20181BBG70007)
文摘AIM: To investigate the effect of repair materials for orbital blowout fractures on the occurrence of postoperative complications. METHODS: The clinical data and follow-up data of 54 subjects with orbital blowout fractures were retrospectively analyzed. The study was divided into three groups according to the used repair materials: titanium mesh(16 cases), Medpor(12 cases), and Medpor titanium mesh(26 cases). All test data were analyzed using the SPSS version 23.0 statistical software. The mean age and duration of disease between the groups were compared through oneway analysis of variance. The Chi-square(χ~2) test was used to compare the number of males and females, different fracture types, and different surgical approaches among groups. The χ~2 test was used to compare the frequencies for complications in each group.RESULTS: The baseline characteristics of age and gender in each group were matched(F=1.763, P=0.172;χ~2=0.026, P=0.987). In addition, there was no difference in the type of fracture and surgical approach(χ~2=0.460, P=0.977;χ~2=0.691, P=0.952), or the incidence of complications(χ~2=0.081, P=0.960) between the three groups. CONCLUSION: Although there is no difference in effect of various repair materials on the incidence of complications, the effect of repair materials on postoperative complications of orbital blowout fractures should not be ignored.
基金supported by the National Natural Science Foundation of China(No.41171002)National Science and Technology Research during the 12th Five-Year Plan Period(No.2012BAD16B02)the Fundamental Research Funds for the Central Universities
文摘The land coverage pattern changes for the past 50 years in a typical region of the Hulun Buir Sandy Grassland were interpreted and analyzed based on a series of remote sensing images in 1959, 2002, 2004 and 2009. The temporal and spatial changes of landscape patterns were revealed and the driving forces were analyzed. The results show that all land coverage types had large variable amplitudes. The grassland area decreased, whereas other areas incleased. Owing to implementation of artificial sand fixation from 2004 to 2009, the areas of flowing blowouts and depositional area decreased by 71,369 and 128,835 m2, respectively. The average patch area reduced, but the number of blowouts increased, fractal dimension increased, and blowout structure became complex. The fragmentation index increased, whereas contagion index decreased. Driving force analysis shows that human factors such as overglazing are slightly larger than natural factors of increased temperature and decreased precipitation
基金co-supported by National Science and Technology Major Project(No.2017-III-0007-0032)Key Laboratory Fund(No.6142702180306)。
文摘The Lean Blowout(LBO)limit is crucial for the aircraft engines.The semi-empirical(such as Lefebvre’s LBO model and Flame Volume(FV)model),numerical and hybrid methods are widely utilized for the LBO limit quick prediction.An innovative hybrid method based on the FV concept is proposed.This method can be classified as a semi-empirical/physical based hybrid prediction method.In this hybrid method,it is assumed that the flame volume varies nearly linearly with the fuel/air ratio near the LBO.The flame volume is obtained directly by the numerical simulation using the threshold value of the visible flame boundary as 900 K.Then the final LBO limits is determined by the FV model.On the premise of keeping the good generality of prediction,the hybrid method based on the FV concept can further improve the prediction accuracy.The comparison with the prediction of the existing available methods on fifteen combustors shows that the hybrid method based on the FV concept achieves better prediction accuracy.The prediction uncertainties between the experimental results and the predicted values by the hybrid method based on the FV concept are within about±10%.
基金co-supported by the National Science and Technology Major Project,China(No.2017-III-0007-0032)the Key Laboratory Fund,China(No.6142702180306).
文摘The occurrence of Lean Blowout(LBO)is a disadvantage that endangers a stable operation of gas turbines.A determination of LBO limits is essential in the design of gas turbine combustors.A semiempirical model is one of the most widely used methods to predict LBO limits.Among the existing semiempirical models for predicting LBO limits,Lefebvre’s LBO model and the Flame Volume(FV)model are particularly suitable for gas turbine combustors.On the basis of Lefebvre’s and FV models,the concept of effective evaporation efficiency is introduced in this paper,and a Flame Volume-Evaporation Efficiency(FV-EE)model is derived and validated.LBO experiments are carried out in a model combustor with 23 different structures and 10 different sprays.The prediction uncertainty of the FV-EE model is less than±13%for all of these 33 structures and sprays,compared with±50%for the FV model and±60%for Lefebvre’s model.Furthermore,the prediction uncertainty of the FV-EE model is also less than±13%for other combustors from available literature.
基金the Ministry of Health,Czech Republic Conceptual Development of Research Organization(FNOs/2017).
文摘AIM:To assess the role of orthoptics in referring patients with orbital floor blowout fracture(OFBF)for conservative or surgical treatment and based on the results,to propose a scoring system for such decision making.METHODS:A retrospective analysis of 69 patients with OFBF was performed(35 treated conservatively,34 surgically).The role of orthoptics in referring to surgery or conservative treatment was retrospectively evaluated,the factors with the highest significance for decision making were identified,and a scoring system proposed using Logistic regression.RESULTS:According to defined criteria,the treatment was unsuccessful in 2(6%)surgically treated and only in one(3%)conservatively treated patient.The proposed scoring system includes the defect size and several values resulting from the orthoptic examination,the elevation of the eyebulb measured on Lancaster screen being the most significant.CONCLUSION:The study demonstrates the benefits of orthoptic examination when making decisions on conservative or surgical treatment and for diagnosing ocular motility disorder(with or without binocular diplopia)in OFBF patients.The proposed scoring system could,following verification in a prospective study,become a valuable adjunctive tool.
基金Sponsored by the Applied Foundation Research Project of Suzhou(SYFG0932)
文摘The tire blowout or severe leakage real-time monitoring is one of key technologies for developing a tire blowout automatic braking system.An indirect real-time monitoring method to fuse analyses of tire vibration and effective radius is provided in this paper,and a monitoring system is developed.The calibration and related test results showthat the system can detect the tire blowout in low and middle vehicle speeds and the severe leakage in all speeds timely and accurately.
基金supported by National Science and Technology Major Project (Nos. 2017-Ⅲ-0007-0032 and J2019-Ⅲ-00020045)
文摘Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation.The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multiswirl staged combustor equipped with an airblast injector.A set of hardware and control system was developed to realize a user-defined fuel supply law.High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow.Partical Image Velocimetry(PIV)and Planar Mie(PMie)scattering were used to acquire the flow fields and spray fields under non-reacting conditions.Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases.With an increase of the fuel decreasing rate,the exhaust temperature before flame extinction increases,and the LBO Fuel-to-Air-Ratio(FAR)decreases.The time evolution of the integral CH*intensity conforms to a linear function during the LBO process.Proper Orthogonal Decomposition(POD)was used to analyze the dynamic characteristics of lean-burn flames.Under different fuel decreasing rates and pressure drops of the injector,flames close to LBO present similar modal spatial distributions,alternately appearing axial,radial,high-order axial,and high-order radial oscillations.
文摘Gas blowout is one of the major hazard in petroleum field which normally damages the gas bearing geologic formation, structure, local tectonic setting, environment and so on. In Bangladesh, there have been three well known gas blowouts. Among them, the most dangerous gas well blowout took place on 8 January 2005 in Sunamganj district when chattak-2 (also known as Tengratila) gas field was drilled. As a result, the surrounding area is facing various problems among them water is the top of the list. From this point of view, the present study has been considered to find the impact of blowout on water around the gas blowout area. In this regard, the water samples (some are very near and some are away from the well) are collected and analyzed in the laboratory following the standard method. Some physical and chemical parameters of water such as pH, turbidity, EC, total solids, dissolved solids, suspended solids, manganese ion, calcium ion, magnesium, iron, chloride and total hardness have measured where without turbidity, manganese and iron, all are still in tolerable state for all purposes and ranging within standard limit based on WHO, EU and EQS for Bangladesh. The quality of the near well tube wells water is much decreased than far away tube wells water which might be the direct or indirect influence of the blowout incident around the area.
文摘Fractured carbonate reservoirs are susceptible to blowout and lost circulation during drilling,which not only restricts drilling speed,but also poses big threat to well control.Moreover,there are few technical means available to reconstruct pressure balance in the borehole.Accordingly,the fine managed pressure drilling was used in the drilling of Well GS19 in the Qixia Formation with super-high pressure and narrow density window,which is a success:①back pressure in the annular spaces will be adjusted to maintain a slightly over-balanced bottom-hole hydraulic pressure,and fluid level in the circulation tank will be kept in a slight dropping state to ensure that natural gas in the formation would not invade into the borehole in a massive volume;②inlet drilling fluid density will be controlled at around 2.35 g/cm^(3),back pressures in the annular be maintained at 2-5 MPa,and bottom-hole pressure equivalent circulation density be controlled at 2.46-2.52 g/cm^(3);③during managed pressure drilling operations,if wellhead pressure exceeds or expects to exceed 7 MPa,semi-blind rams will be closed.Fluids will pass through the choke manifold of the rig to the choke manifold specifically for pressure control before entering gas/liquid separators to discharge gas;④during tripping back pressure will be kept at less than 5 MPa,volume of injected drilling fluid will be higher than the theoretical volume during tripping out,whereas the volume of returned drilling fluid will be higher than the theoretical volume during the out-tripping.This technique has been applied successfully in the drilling of the Qixia Formation,Liangshan Formation and Longmaxi Formation with a total footage of 216.60 m,as a good attempt in complicated wells with both blowout and lost circulation risks,which can provide valuable experiences and guidance for handling similar complexities in the future.
基金Supported by Medical Science Research Project of Hebei Provincial Health Commission,No.20211642.
文摘BACKGROUND Carotid blowout syndrome(CBS)refers to rupture of the extracranial carotid artery and its branches;as a severe complication,it usually occurs after surgery or radiotherapy for malignant tumours of the head and neck.We present a case of CBS caused by chronic infection of the external carotid artery(ECA).In this case,we did not find any evidence of head and neck tumours.CASE SUMMARY A 42-year-old man was referred to the Emergency Department with a complaint of a lump found on the left side of his neck with pain and fever for 4 d.We diagnosed the condition as neck infection with abscess formation based on physical examination,routine blood examination,ultrasound examination and plain computed tomography(CT)and decided to perform emergency surgery.During the operation,30 mL of grey and smelly pus was drained from the deep surface of the sternocleidomastoid muscle.The second day after the operation,the patient suddenly exhibited a large amount of haemoptysis and incision bleeding.The enhanced CT showed distal occlusion of the left ECA and irregular thickening of the broken ends of the artery encased in an uneven enhancement of soft tissue density.Infected ECA occlusion and rupture were considered.The patient was transferred to a vascular unit for transcatheter ECA embolization and recovered well.CONCLUSION Surgeons need to pay attention to vascular lesions caused by chronic infection that may develop into acute CBS.
文摘A left ventricular (LV) free wall rupture is a highly lethal condition. A 75-year-old female who experienced chest pain was diagnosed as having an acute aortic dissection Stanford type A and underwent emergent surgery. Under cardiopulmonary bypass with LV venting through the right superior pulmonary vein, a proximal aortic stamp was formed. The patient was cooled, selective antegrade brain perfusion was performed, and a hemiarch repair was performed. After the patient was transferred to the intensive care unit, her blood pressure suddenly fell to 50 mmHg. She had a blowout rupture in the left ventricular anterolateral free wall. Since the bleeding hall was not large and the damage to the surrounding left ventricular tissue was not very wide, an off-pump multilayered sutureless repair was performed by using three layers of collagen fleece squares with fibrinogen-based impregnation (TachoComb;CSL Behring, Tokyo, Japan) and three layers of gelatin-resorcin-formalin glue reinforced by an equine pericardial patch (Xenomedica;Edwards Lifesciences, LLC, Irvine, CA). The blow-out rupture seemed to be caused by perioperative myocardial infarction generated by the compression of the left ventricular vent to the LV lateral wall. The patient was free from re-rupture or aneurysm enlargement. The thickness of the hemostatic material seemed to help control the bulging of the aneurysm and to prevent further LV aneurysm enlargement and re-rupture.
基金supported by the National Major Special Project of Oil and Gas(No.2016ZX05042003-001,2016ZX05066004-002)the Scientific and Technological Research Guidance Project(No.MTKJ2016-279)by the China National Coal Association,and the Jiangsu Provincial Postdoctoral Scientific and Technological Funding Program(No.1601053C).
文摘A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the basic motion law of the shear ram,combined its structural and operating parameters comprehensively,a model for solving the stress on the cutting edge was established corresponding to three stages(i.e.,shear point contact,cutting and penetrating the drill pipe)according to the wedge stress theory.Then,based on the novel shear ram,the numerical simulation and indoor shear experiment were carried out on CT90 coiled tubing to understand the variation laws of ram stress and shear point stress in the shearing process.And the following research results were obtained.First,when the shear point doesn't contact with the CT90 coiled tubing,the stress at the V-shaped angular center of the ram is the largest,and that at the shear point is extremely small.Second,when the shear point just touches the CT90 coiled tubing,the phenomenon of stress concentration occurs in the vicinity of the shear point of the ram cutting edge.Third,when the shear point cuts into the CT90 coiled tubing,the stress on the shear point and on both wedge edges is the largest,reaching the strength limit of the ram(1050MPa).Fourth,when the shear point enters the annulus after penetrating the CT90 coiled tubing,the ram stress on both sides of the junction between the cutting edge chamfer and the vertical plane is the largest.Fifth,After the CT90 coiled tubing is cut,crack damage occurs in the vicinity of the shear point of the ram cutting edge.In conclusion,the research results can better reflect the stress state of the ram cutting edge and its interaction with the drill pipe in the shearing process,and can provide an important reference for the design,manufacturing and the correct field application of shear rams.
基金supported by National Natural Science Foundation of China(No.52276141)the National Science and Technology Major Project(No.J2019-Ⅲ-0006-0049)+1 种基金the Taishan Scholars Program and Youth Innovation Promotion Association,Chinese Academy of Science(No.Y2023043)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDC0142002).
文摘The impact of turbine guide vanes on a three-dome combustor's lean blowout limit and blowout process was experimentally investigated.The parameters studied include the presence of the turbine guide vanes or not and the blockage ratio of turbine guide vanes.It is shown that the presence of turbine guide vanes and an increase in the blockage ratio increase the lean blowout fuel-to-air ratio.From the images of flame spontaneous emission captured by the high-speed camera,the coupling of the combustor with turbine guide vanes can alter the sequence of the blowout among the three domes,and localized tiny flame lumps have been observed to develop into larger flames during lean blowout.However,flames within the combustor are established independently near blowout,and no reignition is observed.Furthermore,the turbine guide vanes have been found to shorten the duration of the blowout process and enhance the likelihood of blowout by increasing the lean fuel-to-air ratio.
基金supported by the National Nature Science Foundation of China through Grant No.51506086the Jiangsu Funding Program for Excellent Postdoctoral Talent(No.316958)+3 种基金the Natural Science Foundation of Jiangsu Province,China(BK20230932)the China Postdoctoral Science Foundation(No.2023M741697)the Fundamental Research Funds for the Central Universities(No.30923010306)the financial support from Low-carbon Aerospace Power Engineering Research Center of Ministry of Education(CEPE2020018)。
文摘The flame stability limit and propagation characteristics of a reverse-flow combustor without any flame-stabilized device were experimentally investigated under room temperature and pressure.The results indicate that it is feasible to stabilize the flame in the recirculation zones constructed by the impact jet flow from the primary holes and dilution holes.The flame projected area is mainly distributed in the recirculation zone upstream of the primary holes,whose presence and absence mark the ignition and extinction.During the ignition process,the growth rate and value of the flame projected area first increase and then decrease with the inlet velocity increasing from 9.4 m/s to 42.1 m/s.A rapid reduction followed by a slow reduction of ignition and lean blowout equivalence ratios is achieved by the increased inlet velocity.Then the non-reacting fluid structure in three sections was measured,and detailed velocity profiles were analyzed to improve the understanding of the flame stabilization mechanism.The results are conducive to the design of an ultra-compact combustor.
基金supported in part by National Science Foundation, USA grants CNS1954556 and CNS 1932033.
文摘Lean combustion is environment friendly with low NO_(x)emissions providing better fuel efficiency in a combustion system.However,approaching towards lean combustion can make engines more susceptible to an undesirable phenomenon called lean blowout(LBO)that can cause flame extinction leading to sudden loss of power.During the design stage,it is quite challenging for the scientists to accurately determine the optimal operating limits to avoid sudden LBO occurrences.Therefore,it is crucial to develop accurate and computationally tractable frameworks for online LBO prediction in low NO_(x)emission engines.To the best of our knowledge,for the first time,we propose a deep learning approach to detect the transition to LBO in combustion systems.In this work,we utilize a laboratory-scale swirl-stabilized combustor to collect acoustic data for different protocols.For each protocol,starting far from LBO,we gradually move towards the LBO regime,capturing a quasi-static time series dataset at different conditions.Using one of the protocols in our dataset as the reference protocol,we find a transition state metric for our trained deep learning model to detect the imminent LBO in other test protocols.We find that our proposed approach is more precise and computationally faster than other baseline models to detect the transition to LBO.Therefore,we endorse this technique for monitoring the operation of lean combustion engines in real time.
