Upper gastrointestinal bleeding remains a significant cause of hospital admissions. Even though the incidence of peptic ulcer disease and gastritis is decreasing, the incidence rates in neoplasm, Dieulafoy’s lesions,...Upper gastrointestinal bleeding remains a significant cause of hospital admissions. Even though the incidence of peptic ulcer disease and gastritis is decreasing, the incidence rates in neoplasm, Dieulafoy’s lesions, angiodysplasia, and esophagitis are trending up, which necessities physicians to be aware of those pathologies and their specifics. Here, we represent a case of a 62-year-old male on dual antiplatelet therapy who was transferred to our hospital due to severe melena with suspicion of upper gastrointestinal bleeding. Due to hemodynamic instability, the patient was intubated and started on vasopressors. However, several repeated EGDs and CTs of the abdomen with GI bleeding protocol did not reveal the location of active bleeding to stop it. At the same time, clinically, the patient was hemodynamically unstable with continued melena. On the last EGD, a small area of concern resembling gastric varix was clipped for identification purposes, and the patient underwent a selective angiogram with further diagnosis of Dieulafoy’s lesion, which was successfully embolized. Our case demonstrates that Dieulafoy’s lesions can present as severe life-threatening hemorrhage, hard to diagnose with traditional methods such as EGD or CTs, in which case it is recommended to proceed with an angiogram sooner rather than later for further diagnosis and treatment if needed.展开更多
Dieulafoy’s lesions are rare vascular malformations of the gastrointestinal tract. A Dieulafoy’s lesion is an aberrant vessel that does not reduce in caliber when it extends from the submucosa to the mucosa. Damage ...Dieulafoy’s lesions are rare vascular malformations of the gastrointestinal tract. A Dieulafoy’s lesion is an aberrant vessel that does not reduce in caliber when it extends from the submucosa to the mucosa. Damage to this artery can cause severe and intermittent arterial bleeding from small vascular stumps that are difficult to visualize. Furthermore, these catastrophic bleeding episodes frequently result in hemodynamic instability and the need for transfusion of multiple blood products. Recently, uremic syndrome has been identified as a risk factor for gastric mucosal lesions. We present two clinical cases of acute digestive bleeding due to Dielafoy lesion with chronic kidney disease as the main cause, where two different therapies were performed endoscopically. We concluded with the results of our patients that the best therapy was the application of the hemostatic hemoclip on the injury vs the injection with adrenaline on the wound site. Uremia is identified as a risk factor for upper gastrointestinal bleeding in patients with pre-existing Dieulafoy’s lesion, as well as a higher incidence of new bleeding.展开更多
The qualitative solutions of dynamical system expressed with nonlinear differential equation can be divided into two categories. One is that the motion of phase point may approach infinite or stable equilibrium point ...The qualitative solutions of dynamical system expressed with nonlinear differential equation can be divided into two categories. One is that the motion of phase point may approach infinite or stable equilibrium point eventually. Neither periodic excited source nor self-excited oscillation exists in such nonlinear dynamic circuits, so its solution cannot be treated as the synthesis of multiharmonic. And the other is that the endless vibration of phase point is limited within certain range, moreover possesses character of sustained oscillation, namely the bounded nonlinear oscillation. It can persistently and repeatedly vibration after dynamic variable entering into steady state;moreover the motion of phase point will not approach infinite at last;system has not stable equilibrium point. The motional trajectory can be described by a bounded space curve. So far, the curve cannot be represented by concretely explicit parametric form in math. It cannot be expressed analytically by human. The chaos is a most universally common form of bounded nonlinear oscillation. A number of chaotic systems, such as Lorenz equation, Chua’s circuit and lossless system in modern times are some examples among thousands of chaotic equations. In this work, basic properties related to the bounded space curve will be comprehensively summarized by analyzing these examples.展开更多
The algorithms for feedrate profile generation,such as linear and S-curve profiles,have been widely used in machinery controllers,and these algorithms can greatly improve the smoothness of motion.However,most of the a...The algorithms for feedrate profile generation,such as linear and S-curve profiles,have been widely used in machinery controllers,and these algorithms can greatly improve the smoothness of motion.However,most of the algorithms lead to the discontinuous acceleration/deceleration and jerk,or high jerk levels,which is very harmful to machine tool or robot in most occasions. This paper presents a smooth S-curve feedrate profiling generation algorithm that produces continuous feedrate,acceleration,and jerk profiles.Smooth jerk is obtained by imposing limits on the first and second time derivatives of acceleration,resulting in trapezoidal jerk profiles along the tool path.The discretization of smooth S-curve feedrate is realized with a novel approach that improves the efficiency without calculating the deceleration point in each sampled time.To ensure that the interpolation time is a multiple of the value of sampled time,the feedrate,acceleration,jerk,and jerk derivative are recalculated.Meantime,to improve the efficiency,the interpolation steps of all regions are computed before interpolation.According to the distance of trajectory,the smooth S-curve acceleration and decelerations are divided into three blocks：normal block,short block type-Ⅰ,and short block type-Ⅱ.Finally feedrate discretization of short block type-Ⅰand type-Ⅱis obtained with considering the efficiency.The proposed generation algorithm is tested in machining a part on a five axis milling machine,which is controlled with the CNC system for newly developed high-speed machine tools.The test result shows that the smooth S-curve approach has the smoother feedrate,acceleration,deceleration,and jerk profiles than S-curve.The proposed algorithm ensures the automated machinery motion smoothness,and improves the quality and efficiency of the automated machinery motion planning.展开更多
A novel type curve is presented for oil recovery factor prediction suitable for gas flooding by innovatively introducing the equivalent water-gas cut to replace the water cut,comprehensively considering the impact of ...A novel type curve is presented for oil recovery factor prediction suitable for gas flooding by innovatively introducing the equivalent water-gas cut to replace the water cut,comprehensively considering the impact of three-phase flow(oil,gas,water),and deriving the theoretical equations of gas flooding type curve based on Tong’s type curve.The equivalent water-gas cut is the ratio of the cumulative underground volume of gas and water production to the total underground volume of produced fluids.Field production data and the numerical simulation results are used to demonstrate the feasibility of the new type curve and verify the accuracy of the prediction results with field cases.The new type curve is suitable for oil recovery factor prediction of both water flooding and gas flooding.When a reservoir has no gas injected or produced,the gas phase can be ignored and only the oil and water phases need to be considered,in this case,this gas flooding type curve returns to the Tong’s type curve,which can evaluate the oil recovery factor of water flooding.For reservoirs with equivalent water-gas cuts of 60%-80%,the regression method of the new type curve works well in predicting the oil recovery factor.For reservoirs with equivalent water-gas cuts higher than 80%,both the regression and assignment methods of the new type curve can accurately predict the oil recovery factor of gas flooding.展开更多
This is a case of a 5-month-old infant who experienced repeated episodes of hematemesis and no known underlying health conditions. It was subsequently diagnosed as Dieulafoy’s lesion localized in the lesser curvature...This is a case of a 5-month-old infant who experienced repeated episodes of hematemesis and no known underlying health conditions. It was subsequently diagnosed as Dieulafoy’s lesion localized in the lesser curvature of the stomach. Endoscopic diagnosis and treatment were done by angiographic embolization. Dieulafoy’s lesion is considered rare even for adult cases, much more for pediatric patients and usually underdiagnosed. Hence, patients presenting with gastrointestinal bleeding should be managed in a multidisciplinary approach. Spreading awareness about this lesion by including it in the considerations, may help improve early detection and treatment.展开更多
Scattering of SH wave from an interface cylindrical elastic inclusion with a semicircular disconnected curve is investigated. The solution of dynamic stress concentration factor is given using the Green＇s function an...Scattering of SH wave from an interface cylindrical elastic inclusion with a semicircular disconnected curve is investigated. The solution of dynamic stress concentration factor is given using the Green＇s function and the method of complex variable functions. First, the space is divided into upper and lower parts along the interface. In the lower half space, a suitable Green＇s function for the problem is constructed. It is an essential solution of the displacement field for an elastic half space with a semi-cylindrical hill of cylindrical elastic inclusion while bearing out-plane harmonic line source load at the horizontal surface. Thus, the semicircular disconnected curve can be constructed when the two parts are bonded and continuous on the interface loading the undetermined anti-plane forces on the horizontal surfaces. Also, the expressions of displacement and stress fields are obtained in this situation. Finally, examples and results of dynamic stress concentration factor are given. Influences of the cylindrical inclusion and the difference parameters of the two mediators are discussed.展开更多
Based on probabilistic fracture mechanics approach, a new concept of material initial fatigue quality （MIFQ） is developed. Then, the relation between S-N curve and crack propagation curve is studied. From the study,...Based on probabilistic fracture mechanics approach, a new concept of material initial fatigue quality （MIFQ） is developed. Then, the relation between S-N curve and crack propagation curve is studied. From the study, a new durability analysis method is presented. In this method, S-N curve is used to determine crack growth rate under constant amplitude loading and evaluate the effects of different factors on durability and then the structural durability is analyzed. The tests and analyses indicate that this method has lower dependence on testing, and higher accuracy, reliability and generality and is convenient for application.展开更多
When the historic probabilistic S-N curves are given under special survival probability and confidence levels and there is no possible to re-test, fatigue reliability analysis at other levels can not be done except fo...When the historic probabilistic S-N curves are given under special survival probability and confidence levels and there is no possible to re-test, fatigue reliability analysis at other levels can not be done except for the special levels. Therefore, the wide applied curves are expected. Monte Carlo reconstruction methods of the test data and the curves are investigated under fatigue life following lognormal distribution. To overcome the non-conservative assessment of existent man-made enlarging the sample size up to thousands, a simulation policy is employed to address the true production where the sample size is controlled less than 20 for material specimens, 10 for structural component specimens and the errors matching the statistical parameters are less than 5 percent. Availability and feasibility of the present methods have been indicated by the reconstruction practice of the test data and curves for 60Si2Mn high strength spring steel of railway industry.展开更多
A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used ...A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.展开更多
文摘Upper gastrointestinal bleeding remains a significant cause of hospital admissions. Even though the incidence of peptic ulcer disease and gastritis is decreasing, the incidence rates in neoplasm, Dieulafoy’s lesions, angiodysplasia, and esophagitis are trending up, which necessities physicians to be aware of those pathologies and their specifics. Here, we represent a case of a 62-year-old male on dual antiplatelet therapy who was transferred to our hospital due to severe melena with suspicion of upper gastrointestinal bleeding. Due to hemodynamic instability, the patient was intubated and started on vasopressors. However, several repeated EGDs and CTs of the abdomen with GI bleeding protocol did not reveal the location of active bleeding to stop it. At the same time, clinically, the patient was hemodynamically unstable with continued melena. On the last EGD, a small area of concern resembling gastric varix was clipped for identification purposes, and the patient underwent a selective angiogram with further diagnosis of Dieulafoy’s lesion, which was successfully embolized. Our case demonstrates that Dieulafoy’s lesions can present as severe life-threatening hemorrhage, hard to diagnose with traditional methods such as EGD or CTs, in which case it is recommended to proceed with an angiogram sooner rather than later for further diagnosis and treatment if needed.
文摘Dieulafoy’s lesions are rare vascular malformations of the gastrointestinal tract. A Dieulafoy’s lesion is an aberrant vessel that does not reduce in caliber when it extends from the submucosa to the mucosa. Damage to this artery can cause severe and intermittent arterial bleeding from small vascular stumps that are difficult to visualize. Furthermore, these catastrophic bleeding episodes frequently result in hemodynamic instability and the need for transfusion of multiple blood products. Recently, uremic syndrome has been identified as a risk factor for gastric mucosal lesions. We present two clinical cases of acute digestive bleeding due to Dielafoy lesion with chronic kidney disease as the main cause, where two different therapies were performed endoscopically. We concluded with the results of our patients that the best therapy was the application of the hemostatic hemoclip on the injury vs the injection with adrenaline on the wound site. Uremia is identified as a risk factor for upper gastrointestinal bleeding in patients with pre-existing Dieulafoy’s lesion, as well as a higher incidence of new bleeding.
文摘The qualitative solutions of dynamical system expressed with nonlinear differential equation can be divided into two categories. One is that the motion of phase point may approach infinite or stable equilibrium point eventually. Neither periodic excited source nor self-excited oscillation exists in such nonlinear dynamic circuits, so its solution cannot be treated as the synthesis of multiharmonic. And the other is that the endless vibration of phase point is limited within certain range, moreover possesses character of sustained oscillation, namely the bounded nonlinear oscillation. It can persistently and repeatedly vibration after dynamic variable entering into steady state;moreover the motion of phase point will not approach infinite at last;system has not stable equilibrium point. The motional trajectory can be described by a bounded space curve. So far, the curve cannot be represented by concretely explicit parametric form in math. It cannot be expressed analytically by human. The chaos is a most universally common form of bounded nonlinear oscillation. A number of chaotic systems, such as Lorenz equation, Chua’s circuit and lossless system in modern times are some examples among thousands of chaotic equations. In this work, basic properties related to the bounded space curve will be comprehensively summarized by analyzing these examples.
基金supported by Major National S&T Program of China (Grant No.2009ZX04009-014-02)National Hi-tech Research and Development Program of China(863 Program,Grant No. 2009AA043901)
文摘The algorithms for feedrate profile generation,such as linear and S-curve profiles,have been widely used in machinery controllers,and these algorithms can greatly improve the smoothness of motion.However,most of the algorithms lead to the discontinuous acceleration/deceleration and jerk,or high jerk levels,which is very harmful to machine tool or robot in most occasions. This paper presents a smooth S-curve feedrate profiling generation algorithm that produces continuous feedrate,acceleration,and jerk profiles.Smooth jerk is obtained by imposing limits on the first and second time derivatives of acceleration,resulting in trapezoidal jerk profiles along the tool path.The discretization of smooth S-curve feedrate is realized with a novel approach that improves the efficiency without calculating the deceleration point in each sampled time.To ensure that the interpolation time is a multiple of the value of sampled time,the feedrate,acceleration,jerk,and jerk derivative are recalculated.Meantime,to improve the efficiency,the interpolation steps of all regions are computed before interpolation.According to the distance of trajectory,the smooth S-curve acceleration and decelerations are divided into three blocks：normal block,short block type-Ⅰ,and short block type-Ⅱ.Finally feedrate discretization of short block type-Ⅰand type-Ⅱis obtained with considering the efficiency.The proposed generation algorithm is tested in machining a part on a five axis milling machine,which is controlled with the CNC system for newly developed high-speed machine tools.The test result shows that the smooth S-curve approach has the smoother feedrate,acceleration,deceleration,and jerk profiles than S-curve.The proposed algorithm ensures the automated machinery motion smoothness,and improves the quality and efficiency of the automated machinery motion planning.
基金Supported by the National Natural Science Foundation of China(51974268)the Sichuan Province Science and Technology Program(2019YJ0423)。
文摘A novel type curve is presented for oil recovery factor prediction suitable for gas flooding by innovatively introducing the equivalent water-gas cut to replace the water cut,comprehensively considering the impact of three-phase flow(oil,gas,water),and deriving the theoretical equations of gas flooding type curve based on Tong’s type curve.The equivalent water-gas cut is the ratio of the cumulative underground volume of gas and water production to the total underground volume of produced fluids.Field production data and the numerical simulation results are used to demonstrate the feasibility of the new type curve and verify the accuracy of the prediction results with field cases.The new type curve is suitable for oil recovery factor prediction of both water flooding and gas flooding.When a reservoir has no gas injected or produced,the gas phase can be ignored and only the oil and water phases need to be considered,in this case,this gas flooding type curve returns to the Tong’s type curve,which can evaluate the oil recovery factor of water flooding.For reservoirs with equivalent water-gas cuts of 60%-80%,the regression method of the new type curve works well in predicting the oil recovery factor.For reservoirs with equivalent water-gas cuts higher than 80%,both the regression and assignment methods of the new type curve can accurately predict the oil recovery factor of gas flooding.
文摘This is a case of a 5-month-old infant who experienced repeated episodes of hematemesis and no known underlying health conditions. It was subsequently diagnosed as Dieulafoy’s lesion localized in the lesser curvature of the stomach. Endoscopic diagnosis and treatment were done by angiographic embolization. Dieulafoy’s lesion is considered rare even for adult cases, much more for pediatric patients and usually underdiagnosed. Hence, patients presenting with gastrointestinal bleeding should be managed in a multidisciplinary approach. Spreading awareness about this lesion by including it in the considerations, may help improve early detection and treatment.
基金Project supported by the Natural Science Foundation of Heilongjiang Province (No.A0206)
文摘Scattering of SH wave from an interface cylindrical elastic inclusion with a semicircular disconnected curve is investigated. The solution of dynamic stress concentration factor is given using the Green＇s function and the method of complex variable functions. First, the space is divided into upper and lower parts along the interface. In the lower half space, a suitable Green＇s function for the problem is constructed. It is an essential solution of the displacement field for an elastic half space with a semi-cylindrical hill of cylindrical elastic inclusion while bearing out-plane harmonic line source load at the horizontal surface. Thus, the semicircular disconnected curve can be constructed when the two parts are bonded and continuous on the interface loading the undetermined anti-plane forces on the horizontal surfaces. Also, the expressions of displacement and stress fields are obtained in this situation. Finally, examples and results of dynamic stress concentration factor are given. Influences of the cylindrical inclusion and the difference parameters of the two mediators are discussed.
基金National Natural Science Foundation of China (60472118) High-tech Research Project of Jiangsu Province (BG2004008)
文摘Based on probabilistic fracture mechanics approach, a new concept of material initial fatigue quality （MIFQ） is developed. Then, the relation between S-N curve and crack propagation curve is studied. From the study, a new durability analysis method is presented. In this method, S-N curve is used to determine crack growth rate under constant amplitude loading and evaluate the effects of different factors on durability and then the structural durability is analyzed. The tests and analyses indicate that this method has lower dependence on testing, and higher accuracy, reliability and generality and is convenient for application.
基金Project supported by the National High Technology Research and Development Program of China(863 Program) (No.2006AA04Z406)the National Natural Science Foundation of China (Nos.50375130, 50323003 and 50575189)+1 种基金the Special Foundation for the Authors of National Excellent Doctoral Dissertations (No.200234)the Program for New Century Excellent Talents in University(No.NCET040890)
文摘When the historic probabilistic S-N curves are given under special survival probability and confidence levels and there is no possible to re-test, fatigue reliability analysis at other levels can not be done except for the special levels. Therefore, the wide applied curves are expected. Monte Carlo reconstruction methods of the test data and the curves are investigated under fatigue life following lognormal distribution. To overcome the non-conservative assessment of existent man-made enlarging the sample size up to thousands, a simulation policy is employed to address the true production where the sample size is controlled less than 20 for material specimens, 10 for structural component specimens and the errors matching the statistical parameters are less than 5 percent. Availability and feasibility of the present methods have been indicated by the reconstruction practice of the test data and curves for 60Si2Mn high strength spring steel of railway industry.
文摘A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.
