Bleeding from esophageal varices is a life threatening complication of portal hypertension.Primary prevention of bleeding in patients at risk for a first bleeding episode is therefore a major goal.Medical prophylaxis ...Bleeding from esophageal varices is a life threatening complication of portal hypertension.Primary prevention of bleeding in patients at risk for a first bleeding episode is therefore a major goal.Medical prophylaxis consists of non-selective beta-blockers like propranolol or carvedilol.Variceal endoscopic band ligation is equally effective but procedure related morbidity is a drawback of the method.Therapy of acute bleeding is based on three strategies:vasopressor drugs like terlipressin,antibiotics and endoscopic therapy.In refractory bleeding,self-expandable stents offer an option for bridging to definite treatments like transjugular intrahepatic portosystemic shunt(TIPS).Treatment of bleeding from gastric varices depends on vasopressor drugs and on injection of varices with cyanoacrylate.Strategies for primary or secondary prevention are based on non-selective beta-blockers but data from large clinical trials is lacking.Therapy of refractory bleeding relies on shuntprocedures like TIPS.Bleeding from ectopic varices,portal hypertensive gastropathy and gastric antral vascular ectasia-syndrome is less common.Possible medical and endoscopic treatment options are discussed.展开更多
Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving ar...Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving arc have been developed to increase heating effect of arc to the sidewalls. In this work, a new approach Without weaving arc is attempted to ensure the penetration of sidewall, and ultra-narrow gap welding with the gap of less than 5 mm was executed successfully. In this approach, the width of gap is decreased further, so that the sidewalls are made within range of arc heating to obtain the enough heat. In order to prevent the arc from being attracted by sidewall and going up along the sidewalls, two pieces of flux bands consisting of the specified aggregates are adhered to the sidewalls to constrain the arc. In addition, when flux band being heated by the arc, slag and gases are formed to shield the arc and the weld pool. This technique was tested on the welding experiment of pipeline steel with thickness of 20 mm. The involved welding parameters were obtained, that is, the width of gap is 4 mm, the welding current 250 A, and the heat input 0. 5 kJ/mm, the width of heat-affected zone is 1 -2 mm.展开更多
The performance of the Mel-Frequency Cepstrum Coefficients (MFCC) may be affected by (1) the number of filters, (2) the shape of filters, (3) the way in which filters are spaced, and (4) the way in which the power spe...The performance of the Mel-Frequency Cepstrum Coefficients (MFCC) may be affected by (1) the number of filters, (2) the shape of filters, (3) the way in which filters are spaced, and (4) the way in which the power spectrum is warped. In this paper, several compar- ison experiments are done to find a best implementation. The traditional MFCC calculation excludes the 0th coefficient for the reason that it is regarded as somewhat unreliable. According to the analysis and experiments, the authors find that it can be regarded as the generalized frequency band energy (FBE) and is hence useful, which results in the FBE-MFCC. The au- thors also propose a better analysis, namely the auto-regressive analysis, on the frame energy, which outperforms its 1st and/or 2nd order differential derivatives. Experiments with the '863' Speech Database show that, compared with the traditional MFCC with its corresponding auto- regressive analysis coefficients, the FBE-MFCC and the frame energy with their corresponding auto-regressive analysis coefficients form the best combination, reducing the Chinese syllable er- ror rate (CSER) by about 10%, while the FBE-MFCC with the corresponding auto-regressive analysis coefficients reduces CSER by 2.5%. Comparison experiments are also done with a quite casual Chinese speech database, named Chinese Annotated Spontaneous Speech (CASS) corpus. The FBE-MFCC can reduce the error rate by about 2.9% on an average.展开更多
Rubber band ligation is one of the most important, costeffective and commonly used treatments for internal hemorrhoids. Different technical approaches were developed mainly to improve efficacy and safety. The techniqu...Rubber band ligation is one of the most important, costeffective and commonly used treatments for internal hemorrhoids. Different technical approaches were developed mainly to improve efficacy and safety. The technique can be employed using an endoscope with forward-view or retroflexion or without an endoscope, using a suction elastic band ligator or a forceps ligator. Single or multiple ligations can be performed in a single session. Local anaesthetic after ligation can also be used to reduce the post-procedure pain. Mild bleeding, pain, vasovagal symptoms, slippage of bands, priapism, difficulty in urination, anal fissure, and chronic longitudinal ulcers are normally considered minor complications, more frequently encountered. Massive bleeding, thrombosed hemorrhoids, severe pain, urinary retention needing catheterization, pelvic sepsis and death are uncommon major complications. Mild pain after rubber band ligation is the most common complication with a high frequency in some studies. Secondary bleeding normally occurs 10 to 14 d after banding and patients taking anti-platelet and/or anti-coagulant medication have a higher risk, with some reports of massive life-threatening haemorrhage. Several infectious complications have also been reported including pelvic sepsis, Fournier's gangrene, liver abscesses, tetanus and bacterial endocarditis. To date, seven deaths due to these infectious complications were described. Early recognition and immediate treatment of complications are fundamental for a favourable prognosis.展开更多
In grey system theory,the studies in the field of grey prediction model are focused on real number sequences,rather than grey number ones.Hereby,a prediction model based on interval grey number sequences is proposed.B...In grey system theory,the studies in the field of grey prediction model are focused on real number sequences,rather than grey number ones.Hereby,a prediction model based on interval grey number sequences is proposed.By mining the geometric features of interval grey number sequences on a two-dimensional surface,all the interval grey numbers are converted into real numbers by means of certain algorithm,and then the prediction model is established based on those real number sequences.The entire process avoids the algebraic operations of grey number,and the prediction problem of interval grey number is usefully solved.Ultimately,through an example＇s program simulation,the validity and practicability of this novel model are verified.展开更多
Rapid industrialization has accordingly increased the demand for energy.This has resulted in the increasingly severe energy and environmental crises.Hydrogen production,based on the photocatalytic water splitting driv...Rapid industrialization has accordingly increased the demand for energy.This has resulted in the increasingly severe energy and environmental crises.Hydrogen production,based on the photocatalytic water splitting driven by sunlight,is able to directly convert solar energy into a usable or storable energy resource,which is considered to be an ideal alternative energy source to assist in solving the energy crisis and environmental pollution.Unfortunately,the hydrogen production efficiency of single phase photocatalysts is too low to meet the practical requirements.The construction of heterostructured photocatalyst systems,which are comprised of multiple components or multiple phases,is an efficient method to facilitate the separation of electron‐hole pairs to minimize the energy‐waste,provide more electrons,enhance their redox ability,and hence improve the photocatalytic activity.We summarize the recent progress in the rational design and fabrication of nanoheterostructured photocatalysts.The heterojunction photocatalytic hydrogen generation systems can be divided into type‐I,type‐II,pn‐junction and Z‐scheme junction,according to the differences in the transfer of the photogenerated electrons and holes.Finally,a summary and some of the challenges and prospects for the future development of heterojunction photocatalytic systems are discussed.展开更多
A solution is given for the word problem for free idempotent distributive semirings. Using this solution the lattice L(ID) of subvarieties of the variety ID of idempotent distributive semirings is determined. It turns...A solution is given for the word problem for free idempotent distributive semirings. Using this solution the lattice L(ID) of subvarieties of the variety ID of idempotent distributive semirings is determined. It turns out that L(ID) is isomorphic to the direct product of a four-element lattice and a lattice which is itself a subdirect product of four copies of the lattice L (B) of all band varieties. Therefore L(ID) is countably infinite and distributive. Every subvariety of ID is finitely based.展开更多
The nitrogen and fluorine co doped TiO 2 polycrystalline powder was synthesized by calcinations of the hydrolysis product of tetra butyl titanate with ammonium fluoride. Nitrogen and fluorine co doping causes the abso...The nitrogen and fluorine co doped TiO 2 polycrystalline powder was synthesized by calcinations of the hydrolysis product of tetra butyl titanate with ammonium fluoride. Nitrogen and fluorine co doping causes the absorption edge of TiO 2 to shift to a lower energy region. The photocatalytic activity of co doped TiO 2 with anatase phases was found to be 2 4 times higher than that of the commercial TiO 2 photocatalyst Degussa P25 for phenol decomposition under visible light irradiation. The co doped TiO 2 powders only contain anatase phases even at 1000℃. Apparently, ammonium fluoride added retarded phase transformation of the TiO 2 powders from anatase to rutile. The substitutional fluorine and interstitial nitrogen atoms in co doped TiO 2 polycrystalline powder were responsible for the vis light response and caused the absorption edge of TiO 2 to shift to a lower energy region.展开更多
The aim of this paper is to investigate abundant semigroups with a multiplicative adequate transversal.Some properties and characterizations for such semigroups are obtained.In particular. we establish the structure o...The aim of this paper is to investigate abundant semigroups with a multiplicative adequate transversal.Some properties and characterizations for such semigroups are obtained.In particular. we establish the structure of this class of abundant semigroups in terms of left normal bands,right normal braids and adequate semigroups with some simple Compatibility conditions.Finally.we apply this structure to some special cases.展开更多
AIM: To compare the hemostatic efficacy and safety of two mechanical endoscopic methods: endoscopic band ligation (EBL) and endoscopic hemoclip placement (EHP) in patients with actively bleeding Mallory-Weiss syndrome...AIM: To compare the hemostatic efficacy and safety of two mechanical endoscopic methods: endoscopic band ligation (EBL) and endoscopic hemoclip placement (EHP) in patients with actively bleeding Mallory-Weiss syndrome (MWS). METHODS: A prospective randomized study to compare the efficacy and safety of EHP with EBL was performed from January 2002 to August 2005. Forty-one patients with active bleeding from MWS were treated with EHP (n = 21) or EBL (n = 20). RESULTS: There were no significant differences between groups with respect to clinical and endoscopic characteristics. The mean number of hemoclips applied was 3.2 ± 1.5 and the mean number of bands applied was 1.2 ± 0.4. Primary hemostasis was achieved in all patients. Recurrent bleeding was observed in one patient from the EHP group and two from the EBL group. Patients with recurrent bleeding were treated by the same modality as at randomization and secondary hemostasis was achieved in all. There were no significant differences between the two groups in total transfusion amount or duration of hospital stay. No complications or bleeding-related death resulted. CONCLUSION: EHP and EBL are equally effective and safe for the management of active bleeding in patients with Mallory-Weiss syndrome, even in those with shock or comorbid diseases.展开更多
Based on the variational theory, a wavelet-based numerical method is developed to calculate the defect states of acoustic waves in two-dimensional phononic crystals with point and line defects. The supercell technique...Based on the variational theory, a wavelet-based numerical method is developed to calculate the defect states of acoustic waves in two-dimensional phononic crystals with point and line defects. The supercell technique is applied. By expanding the displacement field and the material constants （mass density and elastic stiffness） in periodic wavelets, the explicit formulations of an eigenvalue problem for the plane harmonic bulk waves in such a phononic structure are derived. The point and line defect states in solid-liquid and solid-solid systems are calculated. Comparisons of the present results with those measured experimentally or those from the plane wave expansion method show that the present method can yield accurate results with faster convergence and less computing time.展开更多
Fault rockburst is treated as a strain localization problem under dynamicloading condition considering strain gradient and strain rate. As a kind of dynamic fracturephenomena, rockburst has characteristics of strain l...Fault rockburst is treated as a strain localization problem under dynamicloading condition considering strain gradient and strain rate. As a kind of dynamic fracturephenomena, rockburst has characteristics of strain localization, which is considered as aone-dimensional shear problem subjected to normal compressive stress and tangential shear stress.The constitutive relation of rock material is bilinear (elastic and strain softening) and sensitiveto shear strain rate. The solutions proposed based on gradient-dependent plasticity show thatintense plastic strain is concentrated in fault band and the thickness of the band depends on thecharacteristic length of rock material. The post-peak stiffness of the fault band was determinedaccording to the constitutive parameters of rock material and shear strain rate. Fault bandundergoing strain softening and elastic rock mass outside the band constitute a system and theinstability criterion of the system was proposed based on energy theory. The criterion depends onthe constitutive relation of rock material, the structural size and the strain rate. The staticresult regardless of the strain rate is the special case of the present analytical solution. Highstrain rate can lead to instability of the system.展开更多
文摘Bleeding from esophageal varices is a life threatening complication of portal hypertension.Primary prevention of bleeding in patients at risk for a first bleeding episode is therefore a major goal.Medical prophylaxis consists of non-selective beta-blockers like propranolol or carvedilol.Variceal endoscopic band ligation is equally effective but procedure related morbidity is a drawback of the method.Therapy of acute bleeding is based on three strategies:vasopressor drugs like terlipressin,antibiotics and endoscopic therapy.In refractory bleeding,self-expandable stents offer an option for bridging to definite treatments like transjugular intrahepatic portosystemic shunt(TIPS).Treatment of bleeding from gastric varices depends on vasopressor drugs and on injection of varices with cyanoacrylate.Strategies for primary or secondary prevention are based on non-selective beta-blockers but data from large clinical trials is lacking.Therapy of refractory bleeding relies on shuntprocedures like TIPS.Bleeding from ectopic varices,portal hypertensive gastropathy and gastric antral vascular ectasia-syndrome is less common.Possible medical and endoscopic treatment options are discussed.
文摘Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving arc have been developed to increase heating effect of arc to the sidewalls. In this work, a new approach Without weaving arc is attempted to ensure the penetration of sidewall, and ultra-narrow gap welding with the gap of less than 5 mm was executed successfully. In this approach, the width of gap is decreased further, so that the sidewalls are made within range of arc heating to obtain the enough heat. In order to prevent the arc from being attracted by sidewall and going up along the sidewalls, two pieces of flux bands consisting of the specified aggregates are adhered to the sidewalls to constrain the arc. In addition, when flux band being heated by the arc, slag and gases are formed to shield the arc and the weld pool. This technique was tested on the welding experiment of pipeline steel with thickness of 20 mm. The involved welding parameters were obtained, that is, the width of gap is 4 mm, the welding current 250 A, and the heat input 0. 5 kJ/mm, the width of heat-affected zone is 1 -2 mm.
文摘The performance of the Mel-Frequency Cepstrum Coefficients (MFCC) may be affected by (1) the number of filters, (2) the shape of filters, (3) the way in which filters are spaced, and (4) the way in which the power spectrum is warped. In this paper, several compar- ison experiments are done to find a best implementation. The traditional MFCC calculation excludes the 0th coefficient for the reason that it is regarded as somewhat unreliable. According to the analysis and experiments, the authors find that it can be regarded as the generalized frequency band energy (FBE) and is hence useful, which results in the FBE-MFCC. The au- thors also propose a better analysis, namely the auto-regressive analysis, on the frame energy, which outperforms its 1st and/or 2nd order differential derivatives. Experiments with the '863' Speech Database show that, compared with the traditional MFCC with its corresponding auto- regressive analysis coefficients, the FBE-MFCC and the frame energy with their corresponding auto-regressive analysis coefficients form the best combination, reducing the Chinese syllable er- ror rate (CSER) by about 10%, while the FBE-MFCC with the corresponding auto-regressive analysis coefficients reduces CSER by 2.5%. Comparison experiments are also done with a quite casual Chinese speech database, named Chinese Annotated Spontaneous Speech (CASS) corpus. The FBE-MFCC can reduce the error rate by about 2.9% on an average.
文摘Rubber band ligation is one of the most important, costeffective and commonly used treatments for internal hemorrhoids. Different technical approaches were developed mainly to improve efficacy and safety. The technique can be employed using an endoscope with forward-view or retroflexion or without an endoscope, using a suction elastic band ligator or a forceps ligator. Single or multiple ligations can be performed in a single session. Local anaesthetic after ligation can also be used to reduce the post-procedure pain. Mild bleeding, pain, vasovagal symptoms, slippage of bands, priapism, difficulty in urination, anal fissure, and chronic longitudinal ulcers are normally considered minor complications, more frequently encountered. Massive bleeding, thrombosed hemorrhoids, severe pain, urinary retention needing catheterization, pelvic sepsis and death are uncommon major complications. Mild pain after rubber band ligation is the most common complication with a high frequency in some studies. Secondary bleeding normally occurs 10 to 14 d after banding and patients taking anti-platelet and/or anti-coagulant medication have a higher risk, with some reports of massive life-threatening haemorrhage. Several infectious complications have also been reported including pelvic sepsis, Fournier's gangrene, liver abscesses, tetanus and bacterial endocarditis. To date, seven deaths due to these infectious complications were described. Early recognition and immediate treatment of complications are fundamental for a favourable prognosis.
基金supported by the National Natural Science Foundation of China(7084001290924022)the Ph.D.Thesis Innovation and Excellent Foundation of Nanjing University of Aeronautics and Astronautics(2010)
文摘In grey system theory,the studies in the field of grey prediction model are focused on real number sequences,rather than grey number ones.Hereby,a prediction model based on interval grey number sequences is proposed.By mining the geometric features of interval grey number sequences on a two-dimensional surface,all the interval grey numbers are converted into real numbers by means of certain algorithm,and then the prediction model is established based on those real number sequences.The entire process avoids the algebraic operations of grey number,and the prediction problem of interval grey number is usefully solved.Ultimately,through an example＇s program simulation,the validity and practicability of this novel model are verified.
基金supported by the National Natural Science Foundation of China (51572253,21271165)Scientific Research Grant of Hefei Science Center of CAS (2015SRG-HSC048)Cooperation between NSFC and Netherlands Organization for Scientific Research (51561135011)~~
文摘Rapid industrialization has accordingly increased the demand for energy.This has resulted in the increasingly severe energy and environmental crises.Hydrogen production,based on the photocatalytic water splitting driven by sunlight,is able to directly convert solar energy into a usable or storable energy resource,which is considered to be an ideal alternative energy source to assist in solving the energy crisis and environmental pollution.Unfortunately,the hydrogen production efficiency of single phase photocatalysts is too low to meet the practical requirements.The construction of heterostructured photocatalyst systems,which are comprised of multiple components or multiple phases,is an efficient method to facilitate the separation of electron‐hole pairs to minimize the energy‐waste,provide more electrons,enhance their redox ability,and hence improve the photocatalytic activity.We summarize the recent progress in the rational design and fabrication of nanoheterostructured photocatalysts.The heterojunction photocatalytic hydrogen generation systems can be divided into type‐I,type‐II,pn‐junction and Z‐scheme junction,according to the differences in the transfer of the photogenerated electrons and holes.Finally,a summary and some of the challenges and prospects for the future development of heterojunction photocatalytic systems are discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No. 197610O4)the Provincial Applied Fundamental Research Foundation of Yunnan (96a001z).
文摘A solution is given for the word problem for free idempotent distributive semirings. Using this solution the lattice L(ID) of subvarieties of the variety ID of idempotent distributive semirings is determined. It turns out that L(ID) is isomorphic to the direct product of a four-element lattice and a lattice which is itself a subdirect product of four copies of the lattice L (B) of all band varieties. Therefore L(ID) is countably infinite and distributive. Every subvariety of ID is finitely based.
文摘The nitrogen and fluorine co doped TiO 2 polycrystalline powder was synthesized by calcinations of the hydrolysis product of tetra butyl titanate with ammonium fluoride. Nitrogen and fluorine co doping causes the absorption edge of TiO 2 to shift to a lower energy region. The photocatalytic activity of co doped TiO 2 with anatase phases was found to be 2 4 times higher than that of the commercial TiO 2 photocatalyst Degussa P25 for phenol decomposition under visible light irradiation. The co doped TiO 2 powders only contain anatase phases even at 1000℃. Apparently, ammonium fluoride added retarded phase transformation of the TiO 2 powders from anatase to rutile. The substitutional fluorine and interstitial nitrogen atoms in co doped TiO 2 polycrystalline powder were responsible for the vis light response and caused the absorption edge of TiO 2 to shift to a lower energy region.
基金supported by the foundation of Yunnan University the Natural Science Foundation of Yunnan Province
文摘The aim of this paper is to investigate abundant semigroups with a multiplicative adequate transversal.Some properties and characterizations for such semigroups are obtained.In particular. we establish the structure of this class of abundant semigroups in terms of left normal bands,right normal braids and adequate semigroups with some simple Compatibility conditions.Finally.we apply this structure to some special cases.
文摘AIM: To compare the hemostatic efficacy and safety of two mechanical endoscopic methods: endoscopic band ligation (EBL) and endoscopic hemoclip placement (EHP) in patients with actively bleeding Mallory-Weiss syndrome (MWS). METHODS: A prospective randomized study to compare the efficacy and safety of EHP with EBL was performed from January 2002 to August 2005. Forty-one patients with active bleeding from MWS were treated with EHP (n = 21) or EBL (n = 20). RESULTS: There were no significant differences between groups with respect to clinical and endoscopic characteristics. The mean number of hemoclips applied was 3.2 ± 1.5 and the mean number of bands applied was 1.2 ± 0.4. Primary hemostasis was achieved in all patients. Recurrent bleeding was observed in one patient from the EHP group and two from the EBL group. Patients with recurrent bleeding were treated by the same modality as at randomization and secondary hemostasis was achieved in all. There were no significant differences between the two groups in total transfusion amount or duration of hospital stay. No complications or bleeding-related death resulted. CONCLUSION: EHP and EBL are equally effective and safe for the management of active bleeding in patients with Mallory-Weiss syndrome, even in those with shock or comorbid diseases.
基金the National Natural Science Foundation of China(No.10632020)the German Research Foundation(No.ZH 15/11-1)jointly by the China Scholarship Council and the German Academic Exchange Service(No.D/08/01795).
文摘Based on the variational theory, a wavelet-based numerical method is developed to calculate the defect states of acoustic waves in two-dimensional phononic crystals with point and line defects. The supercell technique is applied. By expanding the displacement field and the material constants （mass density and elastic stiffness） in periodic wavelets, the explicit formulations of an eigenvalue problem for the plane harmonic bulk waves in such a phononic structure are derived. The point and line defect states in solid-liquid and solid-solid systems are calculated. Comparisons of the present results with those measured experimentally or those from the plane wave expansion method show that the present method can yield accurate results with faster convergence and less computing time.
基金This work was financially supported by the National Natural Science Foundation of China (No.50309004) Liaoning Technical University (No. 02-38).
文摘Fault rockburst is treated as a strain localization problem under dynamicloading condition considering strain gradient and strain rate. As a kind of dynamic fracturephenomena, rockburst has characteristics of strain localization, which is considered as aone-dimensional shear problem subjected to normal compressive stress and tangential shear stress.The constitutive relation of rock material is bilinear (elastic and strain softening) and sensitiveto shear strain rate. The solutions proposed based on gradient-dependent plasticity show thatintense plastic strain is concentrated in fault band and the thickness of the band depends on thecharacteristic length of rock material. The post-peak stiffness of the fault band was determinedaccording to the constitutive parameters of rock material and shear strain rate. Fault bandundergoing strain softening and elastic rock mass outside the band constitute a system and theinstability criterion of the system was proposed based on energy theory. The criterion depends onthe constitutive relation of rock material, the structural size and the strain rate. The staticresult regardless of the strain rate is the special case of the present analytical solution. Highstrain rate can lead to instability of the system.
