There is still significant debate regarding the best surgical treatment for malignant left-sided large bowel obstruction.Primary resection and anastomosis offers the advantages of a definite procedure without need for...There is still significant debate regarding the best surgical treatment for malignant left-sided large bowel obstruction.Primary resection and anastomosis offers the advantages of a definite procedure without need for further surgery.Its main disadvantages are related to the increased technical challenge and to the potential higher risk of anastomotic leakage that occurs in the emergency setting.Primary resection with end colostomy(Hartmann's procedure) is considered the safer option.Tan et al compared in a systematic review and meta-analysis the use of self-expanding metallic stents(SEMS) as a bridge to surgery vs emergency surgery in the management of acute malignant left-sided large bowel obstruction.The authors concluded that the technical and clinical success rates for stenting were lower than expected.SEMS was associated with a high incidence of clinical and silent perforation.Stenting instead of loop colostomy can be recommended only if the appropriate expertise is available in the hospital.The goal of stenting,a decrease of the stoma rate,may be advocated only if the complication rates of stenting are lower than those of stoma creation in the emergency situation.Until now,this was not demonstrated in a prospective randomized trial.展开更多
AIM To outline the physiochemical properties and specific clinical uses of Plasma-Lyte 148 as choice of solution for fluid intervention in critical illness, surgery and perioperative medicine.METHODS We performed an e...AIM To outline the physiochemical properties and specific clinical uses of Plasma-Lyte 148 as choice of solution for fluid intervention in critical illness, surgery and perioperative medicine.METHODS We performed an electronic literature search from Medline and Pub Med(via Ovid), anesthesia and pharmacology textbooks, and online sources including studies that compared Plasma-Lyte 148 to other crystalloid solutions. The following keywords were used: "surgery", "anaesthesia", "anesthesia", "anesthesiology", "anaesthesiology", "fluids", "fluid therapy", "crystalloid", "saline", "plasma-Lyte", "plasmalyte", "hartmann's", "ringers" "acetate", "gluconate", "malate", "lactate". All relevant articles were accessed in full. We summarized the data and reported the data in tables and text. RESULTS We retrieved 104 articles relevant to the choice of Plasma-Lyte 148 for fluid intervention in critical illness, surgery and perioperative medicine. We analyzed the data and reported the results in tables and text.CONCLUSION Plasma-Lyte 148 is an isotonic, buffered intravenous crystalloid solution with a physiochemical composition that closely reflects human plasma. Emerging data supports the use of buffered crystalloid solutions in preference to saline in improving physicochemical outcomes. Further large randomized controlled trials assessing the comparative effectiveness of PlasmaLyte 148 and other crystalloid solutions in measuring clinically important outcomes such as morbidity and mortality are needed.展开更多
This article shows that in spherical polar coordinates, some noncentral separable potentials have super-symmetry and shape invariance in the r and θ dimensions, we choose Hartmann potential and ring-shaped oscillator...This article shows that in spherical polar coordinates, some noncentral separable potentials have super-symmetry and shape invariance in the r and θ dimensions, we choose Hartmann potential and ring-shaped oscillator astwo important examples, thus in principle the energy eigenvalues and energy eigenfunctions of such the potentials in ther and θ dimensions can be obtained by the method of supersymmetric quantum mechanics. Here we use an alternativemethod to get the required results.展开更多
A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat ...A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved with the finite element differential equation solver COMSOL Multiphysics.The magnetic field was aligned perpendicularly to the welding direction.The main objective of these simulations was to estimate the critical value of the magnetic field needed to suppress convective flows in the weld pool during high-power(up to 20 kW)laser beam welding of aluminum alloys with up to 20 mm deep weld pool.It reveals that steady magnetic fields with corresponding Hartmann numbers Ha2-104 based on the half-width of the weld pool can effectively suppress convective flows in the weld pool.Moreover,the typically occurring wineglass-shape of the weld cross section caused by thermo-capillary flow is weakened.展开更多
Mirizzi syndrome(MS)is a rare complication of gallstone disease in which the common hepatic duct is obstructed by a stone impacted at Hartmann's pouch or cystic duct.
A conservative TVD scheme is adopted to solve the equations governing the three-dimensional flow of a nonideal compressible conducting fluid in a magnetic field.The eight-wave equations for magnetohydrodynamics(MHD) a...A conservative TVD scheme is adopted to solve the equations governing the three-dimensional flow of a nonideal compressible conducting fluid in a magnetic field.The eight-wave equations for magnetohydrodynamics(MHD) are proved to be a non-strict hyperbolic system,therefore it is difficult to develop its eigenstructure.Powell developed a new set of equations which cannot be numerically simulated by conservative TVD scheme directly due to its non-conservative form.A conservative TVD scheme augmented with a new set of eigenvectors is proposed in the paper.To validate this scheme,1-D MHD shock tube,unsteady MHD Rayleigh problem and steady MHD Hartmann problem for different flow conditions are simulated.The simulated results are in good agreement with the existing analytical results.So this scheme can be used to effectively simulate high-conductivity fluids such as cosmic MHD problem and hypersonic MHD flow over a blunt body,etc.展开更多
The real-time measurement of the polarization and phase information of light is very important and desirable in optics.Metasurfaces can be used to achieve flexible wavefront control and can therefore be used to replac...The real-time measurement of the polarization and phase information of light is very important and desirable in optics.Metasurfaces can be used to achieve flexible wavefront control and can therefore be used to replace traditional optical elements to produce a highly integrated and extremely compact optical system.Here,we propose an efficient and compact optical multiparameter detection system based on a Hartmann–Shack array with 2×2subarray metalenses.This system not only enables the efficient and accurate measurement of the spatial polarization profiles of optical beams via the inspection of foci amplitudes,but also measures the phase and phasegradient profiles by analyzing foci displacements.In this work,details of the design of the elliptical silicon pillars for the metalens are described,and we achieve a high average focusing efficiency of 48%and a high spatial resolution.The performance of the system is validated by the experimental measurement of 22 scalar polarized beams,an azimuthally polarized beam,a radially polarized beam,and a vortex beam.The experimental results are in good agreement with theoretical predictions.展开更多
A numerical procedure based on a five-wave model associated with non-ideal,low magnetic Reynolds number magnetohydrodynamic(MHD)flows was developed.It is composed of an entropy conditioned scheme for solving the non-h...A numerical procedure based on a five-wave model associated with non-ideal,low magnetic Reynolds number magnetohydrodynamic(MHD)flows was developed.It is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations,in conjunction with an SOR method for solving the elliptic equation governing the electrical potential of flow field.To validate the developed procedure,two different test cases were used which included MHD Rayleigh problem and MHD Hartmann problem.The simulations were performed under the assumption of low magnetic Reynolds number.The simulated results were found to be in good agreement with the closed form analytical solutions deduced in the present study,showing that the present algorithm could simulate engineering MHD flow at low magnetic Reynolds number effectively.In the end,a flow field between a pair of segmented electrodes in a three dimensional MHD channel was simulated using the present algorithm with and without including Hall effects.Without the introduction of Hall effects,no distortion was observed in the current and potential lines.By taking the Hall effects into account,the potential lines distorted and clustered at the upstream and downstream edges of the cathode and anode,respectively.展开更多
In this paper,the basic equations of two-phase liquid metal flow in a magnetic field are de- rived,and specifically,two-phase liquid metal MHD flow in a rectangular channel is studied,and the expres- sions of velocity...In this paper,the basic equations of two-phase liquid metal flow in a magnetic field are de- rived,and specifically,two-phase liquid metal MHD flow in a rectangular channel is studied,and the expres- sions of velocity distribution of liquid and gas phases and the ratio K_0 of the pressure drop in two-phase MHD flow to that in single-phase are derived.Results of calculation show that the ratio K_0 is smaller than unity and decreases with increasing void fraction and Hartmann number because the effective electrical conduc- tivity in the two-phase case decreases.展开更多
This paper presents the effect of magnetic field, indicated by Hartmann number (Ha), on the free convective flow of Magneto-hydro-dynamic (MHD) fluid in a square cavity with a heated cone of different orientation. Alt...This paper presents the effect of magnetic field, indicated by Hartmann number (Ha), on the free convective flow of Magneto-hydro-dynamic (MHD) fluid in a square cavity with a heated cone of different orientation. Although similar studies abound, the novelty of this work lies in the presence of the heated cone, whose orientation is varied at different angles. The mathematical model includes the system of governing mass, momentum and energy equations. The system is solved by finite element method. The calculations are performed for Prandtl number Pr = 0.71;the Rayleigh number Ra = 10, 1000, 100,000;and for Hartmann number Ha = 0, 20, 50, 100. The results are illustrated with streamlines, velocity profiles and isotherms. From the results, it is found that for the present configuration, magnetic field (Hartmann number) has no effect on the shape of the streamlines for low Rayleigh numbers. However, for high values of Ra, the effect of Ha becomes quite visible. Magnetic field affects the flow by retarding the fluid movement, and thus affects convective heat transfer. At low Ra, the fluid movement and heat transfer rate are already slowing, thus impressing a magnetic field does not produce much effect. At high Ra, fluid particles move at high velocity and change the stream lines, in absence of any magnetic force. Impressing magnetic field in this situation produced noticeable effect by slowing down the fluid movement and changing the streamlines back to low Ra situations. It is noted that a combination of low Ra with zero or low Ha produces similar effects with the combination of high Ra and high Ha. It can be concluded that with increasing Ha, heat transfer mode in MHD fluid gradually changes toward conduction from convection. It can be surmised that sufficiently large Ha can potentially stop the fluid movement altogether. In that case, heat transfer would be fully by conduction.展开更多
The gas flow in the Hartmann resonance tube is numerically investigated by the finite volume method based on the Roe solver. The oscillation of the flow is studied with the presence of a needle actuator set along the ...The gas flow in the Hartmann resonance tube is numerically investigated by the finite volume method based on the Roe solver. The oscillation of the flow is studied with the presence of a needle actuator set along the nozzle axis. Numerical results agree well with the theoretical and experimental results available. Numerical results indicate that the resonance mode of the resonance tube will switch by means of removing or adding the actuator. The gas flow in the ultrasonic gas atomization （USGA） nozzle is also studied by the same numerical methods. Oscillation caused by the Hartmann resonance tube structure, coupled with a secondary resonator, in the USGA nozzle is investigated. Effects of the variation of parameters on the oscillation are studied. The mechanism of the transition of subsonic flow to supersonic flow in the USGA nozzle is also discussed based on numerical results.展开更多
In this paper, the flow fields of three types of nozzles （ Hartmann, Laval and Laminar nozzles ） under the same conditions are simulated, and the corresponding to pressure, temperature, velocity and turbulence inten...In this paper, the flow fields of three types of nozzles （ Hartmann, Laval and Laminar nozzles ） under the same conditions are simulated, and the corresponding to pressure, temperature, velocity and turbulence intensity are obtained. The results suggest that two crushing presents in the atomization process using Hartmann nozzle, but only one crushing presents in the atomization process using the other nozzles, through the comparative research on the flow field features of three types of nozzle. Furthermore, the shockwave plays a more important role in crushing of liquid metal than velocity.展开更多
We report a case of sigmoid colon perforation in a patient with Crohn's disease undergoing computed-tomographic (CT) colonography. A 70-year-old patient with Crohn's disease with terminal ileitis and sigmoid s...We report a case of sigmoid colon perforation in a patient with Crohn's disease undergoing computed-tomographic (CT) colonography. A 70-year-old patient with Crohn's disease with terminal ileitis and sigmoid stricture underwent CT colonography after incomplete conventional colonoscopy. During the procedure, the colon was inflated by air insufflation and the patient developed abdominal pain with radiological evidence of retroperitoneal and intraperitoneal free gas. Hartmann's operation was performed. This case highlights that CT colonography is not risk-free. The risk of perforation may be higher in patients with inflammatory bowel disease.展开更多
AIM: To compare the open and laparoscopic Hartmann’s reversal in patients first treated for complicated diverticulitis.METHODS: Forty-six consecutive patients with diverticular disease were included in this retrospe... AIM: To compare the open and laparoscopic Hartmann’s reversal in patients first treated for complicated diverticulitis.METHODS: Forty-six consecutive patients with diverticular disease were included in this retrospective,singlecenter study of a prospectively maintained colorectal surgery database.All patients underwent conventional Hartmann’s procedures for acute complicated diverticulitis.Other indications for Hartmann’s procedures were excluded.Patients underwent open(OHR) or laparoscopic Hartmann’s reversal(LHR) between 2000 and 2010,and received the same pre-and post-operative protocols of cares.Operative variables,length of stay,short-(at 1 mo) and long-term(at 1 and 3 years) postoperative complications,and surgery-related costs were compared between groups.RESULTS: The OHR group consisted of 18 patients(13 males,mean age ± SD,61.4 ± 12.8 years),and the LHR group comprised 28 patients(16 males,mean age 54.9 ± 14.4 years).The mean operative time and the estimated blood loss were higher in the OHR group(235.8 ± 43.6 min vs 171.1 ± 27.4 min;and 301.1 ± 54.6 mL vs 225 ± 38.6 mL respectively,P = 0.001).Bowel function returned in an average of 4.3 ± 1.7 d in the OHR group,and 3 ± 1.3 d in the LHR group(P = 0.01).The length of hospital stay was significantly longer in the OHR group(11.2 ± 5.3 d vs 6.7 ± 1.9 d,P 【 0.001).The 1 mo complication rate was 33.3% in the OHR(6 wound infections) and 3.6% in the LHR group(1 hemorrhage)(P = 0.004).At 12 mo,the complication rate remained significantly higher in the OHR group(27.8% vs 10.7%,P = 0.03).The anastomotic leak and mortality rates were nil.At 3 years,no patient required re-intervention for surgical complications.The OHR procedure had significantly higher costs(+56%) compared to the LHR procedure,when combining the surgery-related costs and the length of hospital stay.CONCLUSION: LHR appears to be a safe and feasible procedure that is associated with reduced hospitality stays,complication rates,and costs compared to OHR.展开更多
The present work is devoted to investigating heat transfer and fluid flow in a two dimensional square open cavity containing a heated circular cylinder at the centre. A constant heat flux is set at the left sidewall;h...The present work is devoted to investigating heat transfer and fluid flow in a two dimensional square open cavity containing a heated circular cylinder at the centre. A constant heat flux is set at the left sidewall;high and low temperatures are fixed at the bottom and top walls of the cavity respectively. The right side of the cavity is open. Galerkin Weighted Residual Finite Element Analysis is used to visualize the heat transfer and fluid flow solving two-dimensional governing mass, momentum and energy equations for steady state, heat transfer and fluid flow in presence of magnetic field in side an open square cavity. A uniformly heated circular cylinder is placed at the centre of the cavity as a heat source. To find the effects of Rayleigh number (Ra) on the thermal fields and fluid flow in presence of magnetic field and a heated circular cylinder as heat source by visualization and line graphs is the objective of this study. Numerical results are presented in graphical and tabular form. The study is conducted for different values of Rayleigh number, some fixed Hartmann numbers (Ha) and heat flux (q). In the conclusion it has been observed that the temperature field and fluid flow pattern are functions of the parameters Rayleigh number and Hartmann number.展开更多
文摘There is still significant debate regarding the best surgical treatment for malignant left-sided large bowel obstruction.Primary resection and anastomosis offers the advantages of a definite procedure without need for further surgery.Its main disadvantages are related to the increased technical challenge and to the potential higher risk of anastomotic leakage that occurs in the emergency setting.Primary resection with end colostomy(Hartmann's procedure) is considered the safer option.Tan et al compared in a systematic review and meta-analysis the use of self-expanding metallic stents(SEMS) as a bridge to surgery vs emergency surgery in the management of acute malignant left-sided large bowel obstruction.The authors concluded that the technical and clinical success rates for stenting were lower than expected.SEMS was associated with a high incidence of clinical and silent perforation.Stenting instead of loop colostomy can be recommended only if the appropriate expertise is available in the hospital.The goal of stenting,a decrease of the stoma rate,may be advocated only if the complication rates of stenting are lower than those of stoma creation in the emergency situation.Until now,this was not demonstrated in a prospective randomized trial.
文摘AIM To outline the physiochemical properties and specific clinical uses of Plasma-Lyte 148 as choice of solution for fluid intervention in critical illness, surgery and perioperative medicine.METHODS We performed an electronic literature search from Medline and Pub Med(via Ovid), anesthesia and pharmacology textbooks, and online sources including studies that compared Plasma-Lyte 148 to other crystalloid solutions. The following keywords were used: "surgery", "anaesthesia", "anesthesia", "anesthesiology", "anaesthesiology", "fluids", "fluid therapy", "crystalloid", "saline", "plasma-Lyte", "plasmalyte", "hartmann's", "ringers" "acetate", "gluconate", "malate", "lactate". All relevant articles were accessed in full. We summarized the data and reported the data in tables and text. RESULTS We retrieved 104 articles relevant to the choice of Plasma-Lyte 148 for fluid intervention in critical illness, surgery and perioperative medicine. We analyzed the data and reported the results in tables and text.CONCLUSION Plasma-Lyte 148 is an isotonic, buffered intravenous crystalloid solution with a physiochemical composition that closely reflects human plasma. Emerging data supports the use of buffered crystalloid solutions in preference to saline in improving physicochemical outcomes. Further large randomized controlled trials assessing the comparative effectiveness of PlasmaLyte 148 and other crystalloid solutions in measuring clinically important outcomes such as morbidity and mortality are needed.
文摘This article shows that in spherical polar coordinates, some noncentral separable potentials have super-symmetry and shape invariance in the r and θ dimensions, we choose Hartmann potential and ring-shaped oscillator astwo important examples, thus in principle the energy eigenvalues and energy eigenfunctions of such the potentials in ther and θ dimensions can be obtained by the method of supersymmetric quantum mechanics. Here we use an alternativemethod to get the required results.
基金Item Sponsored by the Deutsche Forschungsgemeinschaft (BonnGermany) Under Grant No.DFG GU 1211/2-1
文摘A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved with the finite element differential equation solver COMSOL Multiphysics.The magnetic field was aligned perpendicularly to the welding direction.The main objective of these simulations was to estimate the critical value of the magnetic field needed to suppress convective flows in the weld pool during high-power(up to 20 kW)laser beam welding of aluminum alloys with up to 20 mm deep weld pool.It reveals that steady magnetic fields with corresponding Hartmann numbers Ha2-104 based on the half-width of the weld pool can effectively suppress convective flows in the weld pool.Moreover,the typically occurring wineglass-shape of the weld cross section caused by thermo-capillary flow is weakened.
文摘Mirizzi syndrome(MS)is a rare complication of gallstone disease in which the common hepatic duct is obstructed by a stone impacted at Hartmann's pouch or cystic duct.
文摘A conservative TVD scheme is adopted to solve the equations governing the three-dimensional flow of a nonideal compressible conducting fluid in a magnetic field.The eight-wave equations for magnetohydrodynamics(MHD) are proved to be a non-strict hyperbolic system,therefore it is difficult to develop its eigenstructure.Powell developed a new set of equations which cannot be numerically simulated by conservative TVD scheme directly due to its non-conservative form.A conservative TVD scheme augmented with a new set of eigenvectors is proposed in the paper.To validate this scheme,1-D MHD shock tube,unsteady MHD Rayleigh problem and steady MHD Hartmann problem for different flow conditions are simulated.The simulated results are in good agreement with the existing analytical results.So this scheme can be used to effectively simulate high-conductivity fluids such as cosmic MHD problem and hypersonic MHD flow over a blunt body,etc.
基金State Key Laboratory of Advanced Optical Communication Systems and Networks(2019GZKF03001)Fundamental Research Funds for the Central Universities(2019kfy XKJC038)National Natural Science Foundation of China(11574102,61475009,61835008)。
文摘The real-time measurement of the polarization and phase information of light is very important and desirable in optics.Metasurfaces can be used to achieve flexible wavefront control and can therefore be used to replace traditional optical elements to produce a highly integrated and extremely compact optical system.Here,we propose an efficient and compact optical multiparameter detection system based on a Hartmann–Shack array with 2×2subarray metalenses.This system not only enables the efficient and accurate measurement of the spatial polarization profiles of optical beams via the inspection of foci amplitudes,but also measures the phase and phasegradient profiles by analyzing foci displacements.In this work,details of the design of the elliptical silicon pillars for the metalens are described,and we achieve a high average focusing efficiency of 48%and a high spatial resolution.The performance of the system is validated by the experimental measurement of 22 scalar polarized beams,an azimuthally polarized beam,a radially polarized beam,and a vortex beam.The experimental results are in good agreement with theoretical predictions.
文摘A numerical procedure based on a five-wave model associated with non-ideal,low magnetic Reynolds number magnetohydrodynamic(MHD)flows was developed.It is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations,in conjunction with an SOR method for solving the elliptic equation governing the electrical potential of flow field.To validate the developed procedure,two different test cases were used which included MHD Rayleigh problem and MHD Hartmann problem.The simulations were performed under the assumption of low magnetic Reynolds number.The simulated results were found to be in good agreement with the closed form analytical solutions deduced in the present study,showing that the present algorithm could simulate engineering MHD flow at low magnetic Reynolds number effectively.In the end,a flow field between a pair of segmented electrodes in a three dimensional MHD channel was simulated using the present algorithm with and without including Hall effects.Without the introduction of Hall effects,no distortion was observed in the current and potential lines.By taking the Hall effects into account,the potential lines distorted and clustered at the upstream and downstream edges of the cathode and anode,respectively.
基金The Project is supported by the National Natural Science Foundation of China
文摘In this paper,the basic equations of two-phase liquid metal flow in a magnetic field are de- rived,and specifically,two-phase liquid metal MHD flow in a rectangular channel is studied,and the expres- sions of velocity distribution of liquid and gas phases and the ratio K_0 of the pressure drop in two-phase MHD flow to that in single-phase are derived.Results of calculation show that the ratio K_0 is smaller than unity and decreases with increasing void fraction and Hartmann number because the effective electrical conduc- tivity in the two-phase case decreases.
文摘This paper presents the effect of magnetic field, indicated by Hartmann number (Ha), on the free convective flow of Magneto-hydro-dynamic (MHD) fluid in a square cavity with a heated cone of different orientation. Although similar studies abound, the novelty of this work lies in the presence of the heated cone, whose orientation is varied at different angles. The mathematical model includes the system of governing mass, momentum and energy equations. The system is solved by finite element method. The calculations are performed for Prandtl number Pr = 0.71;the Rayleigh number Ra = 10, 1000, 100,000;and for Hartmann number Ha = 0, 20, 50, 100. The results are illustrated with streamlines, velocity profiles and isotherms. From the results, it is found that for the present configuration, magnetic field (Hartmann number) has no effect on the shape of the streamlines for low Rayleigh numbers. However, for high values of Ra, the effect of Ha becomes quite visible. Magnetic field affects the flow by retarding the fluid movement, and thus affects convective heat transfer. At low Ra, the fluid movement and heat transfer rate are already slowing, thus impressing a magnetic field does not produce much effect. At high Ra, fluid particles move at high velocity and change the stream lines, in absence of any magnetic force. Impressing magnetic field in this situation produced noticeable effect by slowing down the fluid movement and changing the streamlines back to low Ra situations. It is noted that a combination of low Ra with zero or low Ha produces similar effects with the combination of high Ra and high Ha. It can be concluded that with increasing Ha, heat transfer mode in MHD fluid gradually changes toward conduction from convection. It can be surmised that sufficiently large Ha can potentially stop the fluid movement altogether. In that case, heat transfer would be fully by conduction.
文摘The gas flow in the Hartmann resonance tube is numerically investigated by the finite volume method based on the Roe solver. The oscillation of the flow is studied with the presence of a needle actuator set along the nozzle axis. Numerical results agree well with the theoretical and experimental results available. Numerical results indicate that the resonance mode of the resonance tube will switch by means of removing or adding the actuator. The gas flow in the ultrasonic gas atomization （USGA） nozzle is also studied by the same numerical methods. Oscillation caused by the Hartmann resonance tube structure, coupled with a secondary resonator, in the USGA nozzle is investigated. Effects of the variation of parameters on the oscillation are studied. The mechanism of the transition of subsonic flow to supersonic flow in the USGA nozzle is also discussed based on numerical results.
文摘In this paper, the flow fields of three types of nozzles （ Hartmann, Laval and Laminar nozzles ） under the same conditions are simulated, and the corresponding to pressure, temperature, velocity and turbulence intensity are obtained. The results suggest that two crushing presents in the atomization process using Hartmann nozzle, but only one crushing presents in the atomization process using the other nozzles, through the comparative research on the flow field features of three types of nozzle. Furthermore, the shockwave plays a more important role in crushing of liquid metal than velocity.
文摘We report a case of sigmoid colon perforation in a patient with Crohn's disease undergoing computed-tomographic (CT) colonography. A 70-year-old patient with Crohn's disease with terminal ileitis and sigmoid stricture underwent CT colonography after incomplete conventional colonoscopy. During the procedure, the colon was inflated by air insufflation and the patient developed abdominal pain with radiological evidence of retroperitoneal and intraperitoneal free gas. Hartmann's operation was performed. This case highlights that CT colonography is not risk-free. The risk of perforation may be higher in patients with inflammatory bowel disease.
文摘 AIM: To compare the open and laparoscopic Hartmann’s reversal in patients first treated for complicated diverticulitis.METHODS: Forty-six consecutive patients with diverticular disease were included in this retrospective,singlecenter study of a prospectively maintained colorectal surgery database.All patients underwent conventional Hartmann’s procedures for acute complicated diverticulitis.Other indications for Hartmann’s procedures were excluded.Patients underwent open(OHR) or laparoscopic Hartmann’s reversal(LHR) between 2000 and 2010,and received the same pre-and post-operative protocols of cares.Operative variables,length of stay,short-(at 1 mo) and long-term(at 1 and 3 years) postoperative complications,and surgery-related costs were compared between groups.RESULTS: The OHR group consisted of 18 patients(13 males,mean age ± SD,61.4 ± 12.8 years),and the LHR group comprised 28 patients(16 males,mean age 54.9 ± 14.4 years).The mean operative time and the estimated blood loss were higher in the OHR group(235.8 ± 43.6 min vs 171.1 ± 27.4 min;and 301.1 ± 54.6 mL vs 225 ± 38.6 mL respectively,P = 0.001).Bowel function returned in an average of 4.3 ± 1.7 d in the OHR group,and 3 ± 1.3 d in the LHR group(P = 0.01).The length of hospital stay was significantly longer in the OHR group(11.2 ± 5.3 d vs 6.7 ± 1.9 d,P 【 0.001).The 1 mo complication rate was 33.3% in the OHR(6 wound infections) and 3.6% in the LHR group(1 hemorrhage)(P = 0.004).At 12 mo,the complication rate remained significantly higher in the OHR group(27.8% vs 10.7%,P = 0.03).The anastomotic leak and mortality rates were nil.At 3 years,no patient required re-intervention for surgical complications.The OHR procedure had significantly higher costs(+56%) compared to the LHR procedure,when combining the surgery-related costs and the length of hospital stay.CONCLUSION: LHR appears to be a safe and feasible procedure that is associated with reduced hospitality stays,complication rates,and costs compared to OHR.
文摘The present work is devoted to investigating heat transfer and fluid flow in a two dimensional square open cavity containing a heated circular cylinder at the centre. A constant heat flux is set at the left sidewall;high and low temperatures are fixed at the bottom and top walls of the cavity respectively. The right side of the cavity is open. Galerkin Weighted Residual Finite Element Analysis is used to visualize the heat transfer and fluid flow solving two-dimensional governing mass, momentum and energy equations for steady state, heat transfer and fluid flow in presence of magnetic field in side an open square cavity. A uniformly heated circular cylinder is placed at the centre of the cavity as a heat source. To find the effects of Rayleigh number (Ra) on the thermal fields and fluid flow in presence of magnetic field and a heated circular cylinder as heat source by visualization and line graphs is the objective of this study. Numerical results are presented in graphical and tabular form. The study is conducted for different values of Rayleigh number, some fixed Hartmann numbers (Ha) and heat flux (q). In the conclusion it has been observed that the temperature field and fluid flow pattern are functions of the parameters Rayleigh number and Hartmann number.
