We observe enhanced terahertz (THz) radiation generated from a Si3N4 film-coated GaAs photoconductive dipole antenna. Compared to an uncoated antenna with identical electrode geometry and optical excitation power, the...We observe enhanced terahertz (THz) radiation generated from a Si3N4 film-coated GaAs photoconductive dipole antenna. Compared to an uncoated antenna with identical electrode geometry and optical excitation power, the Si3N4 film-coated antenna has a higher effective DC resistance and larger breakdown voltage. As a result, the peak amplitude of generated THz radiation is significantly enhanced due to the Si3N4 film-coated layer.展开更多
Background Spontaneous direct carotid-cavernous fistula （CCF） is relatively rare and few reports have been found in the literature. The aim of this paper was to report the clinical characteristics, imaging findings ...Background Spontaneous direct carotid-cavernous fistula （CCF） is relatively rare and few reports have been found in the literature. The aim of this paper was to report the clinical characteristics, imaging findings and curative effect of endovascular treatment for patients with spontaneous direct CCF. Methods We retrospectively analyzed the clinical data of nine patients with spontaneous direct CCF admitted between May 2003 and November 2007 and the outcomes.of endovascular treatment. Sudden neuro-ophthalmological symptoms were the most common clinical presentation at diagnosis （n=8）. No patients had a history of head trauma. Cerebral digital subtraction angiography （DSA） was performed on all cases under local anesthesia and seven cases received endovascular treatment. Results In eight patients, internal carotid angiograms recorded during the early arterial phase revealed aneurysms located in the cavernous sinuses, and in one patient, a dilated internal carotid artery （ICA） was seen. Among the nine cases, seven received endovascular treatment via a transarterial approach and complete occlusion of the fistula was obtained with no technique-related complications, one died suddenly before treatment and one gave up treatment. A detachable balloon was used as the embolic material in two cases, a detachable balloon and detachable coil as the embolic material in two cases, balloon-assisted coil embolization in two cases and covered stents were successfully placed in the parent vessel to exclude the aneurysm and fistula from circulation in one case. During a follow-up period of 3-48 months, all treated patients remained asymptomatic except for one patient who suffered from ipsilateral decreased vision. Conclusions Most spontaneous direct CCF may be caused by a ruptured intracavernous aneurysm with direct shunting into the cavernous sinus. Endovascular treatment seems to be a safe and effective method for treating spontaneous direct CCF.展开更多
AIM: To evaluate transjugular intrahepatic portosystemic shunt (TIPS) with covered stents for hepatocellular carcinoma (HCC) with main portal vein tumor thrombus (PVTT).
AIM: To investigate the use of fully covered metal stents in benign biliary strictures (BBS) and bile leaks. METHODS: We studied 17 patients, at Harbor-UCLA Medical center (Los Angeles), with BBS (n=12) and bile leaks...AIM: To investigate the use of fully covered metal stents in benign biliary strictures (BBS) and bile leaks. METHODS: We studied 17 patients, at Harbor-UCLA Medical center (Los Angeles), with BBS (n=12) and bile leaks (n=5) from July 2007 to February 2012 that had received placement of fully covered self-expanding metal stents (FCSEMs). Fourteen patients had endoscopic placement of VIABIL (Conmed, Utica, New York, United States) stents and three had Wallflex (Boston Scientific, Mass) stents. FCSEMS were 8 mm or 10 mm in diameter and 4 cm to 10 cm in length. Patients were followed at regular intervals to evaluate for symptoms and liver function tests. FCSEMS were removed after 4 or more weeks. Resolution of BBS and leak was documented cholangiographically following stent removal. Stent patency can be defined as adequate bile and contrast flow from the stent and into the ampulla during endoscopic retrograde cholangiopancreatography (ERCP) without clinical signs and/or symptoms of biliary obstruction. Criterion for bile leak resolution at ERCP is defined as absence of contrast extravasation from the common bile duct, cystic duct remanent, or gall blad-der fossa. Rate of complications such as migration, and instent occlusion were recorded. Failure of endoscopic therapy was defined as persistent biliary stenosis or continuous biliary leakage after 12 mo of stent placement. RESULTS: All 17 patients underwent successful FC- SEMS placement and removal. Etiologies of BBS included: cholecystectomies (n=8), cholelithiasis (n=2), hepatic artery compression (n=1), pancreatitis (n=2), and Whipple procedure (n=1). All bile leaks occurred following cholecystectomy. The anatomic location of BBS varied: distal common bile duct (n=7), common hepatic duct (n=1), hepaticojejunal anastomosis (n=2), right intrahepatic duct (n=1), and choledochoduo-denal anastomatic junction (n=1). All bile leaks were found to be at the cystic duct. Twelve of 17 patients had failed prior stent placement or exchange. Resolution of the biliary strictures 展开更多
Background Despite the current availability of flow diverter devices(FDD), problems remains regarding optimal endovascular treatment(EVT) for blood blister-like aneurysms(BBAs) of the internal carotid artery(ICA). Obj...Background Despite the current availability of flow diverter devices(FDD), problems remains regarding optimal endovascular treatment(EVT) for blood blister-like aneurysms(BBAs) of the internal carotid artery(ICA). Objective To evaluate the safety and efficacy of EVT of BBAs in the ICA with a Willis covered stent. Methods 20 consecutive patients(5 men and 15 women) with ruptured BBAs underwent EVT using a Willis covered stent in two institutions from March 2013 to March 2018. Clinical observations, angiographic characteristics, and procedural and follow-up outcomes were retrospectively evaluated. Results 20 consecutive patients(5 men and 15 women) with ruptured BBAs underwent EVT using a Willis covered stent in two institutions from March 2013 to March 2018. Clinical observations, angiographic characteristics, and procedural and follow-up outcomes were retrospectively evaluated. Conclusion Our initial results demonstrate that reconstructive EVT using a Willis covered stent provides a viable approach to treat ICA BBAs. However, an expanded clinical evaluation and larger cohort are needed to confirm the results.展开更多
BACKGROUND The treatment of difficult common bile duct stones(CBDS)remains a big challenge around the world.Biliary stenting is a widely accepted rescue method in patients with failed stone extraction under endoscopic...BACKGROUND The treatment of difficult common bile duct stones(CBDS)remains a big challenge around the world.Biliary stenting is a widely accepted rescue method in patients with failed stone extraction under endoscopic retrograde cholangiopancreatography.Fully covered self-expanding metal stent(FCSEMS)has gained increasing attention in the management of difficult CBDS.AIM To manufacture a drug-eluting FCSEMS,which can achieve controlled release of stone-dissolving agents and speed up the dissolution of CBDS.METHODS Customized covered nitinol stents were adopted.Sodium cholate(SC)and disodium ethylene diamine tetraacetic acid(EDTA disodium,EDTA for short)were used as stone-dissolving agents.Three different types of drug-eluting stents were manufactured by dip coating(Stent I),coaxial electrospinning(Stent II),and dip coating combined with electrospinning(Stent III),respectively.The drugrelease behavior and stone-dissolving efficacy of these stents were evaluated in vitro to sort out the best manufacturing method.And the selected stonedissolving stents were further put into porcine CBD to evaluate their biosecurity.RESULTS Stent I and Stent II had obvious burst release of drugs in the first 5 d while Stent III presented controlled and sustainable drug release for 30 d.In still buffer,the final stone mass-loss rate of each group was 5.19%±0.69%for naked FCSEMS,20.37%±2.13%for Stent I,24.57%±1.45%for Stent II,and 33.72%±0.67%for Stent III.In flowing bile,the final stone mass-loss rate of each group was 5.87%±0.25%for naked FCSEMS,6.36%±0.48%for Stent I,6.38%±0.37%for Stent II,and 8.15%±0.27%for Stent III.Stent III caused the most stone mass-loss no matter in still buffer or in flowing bile,which was significantly higher than those of other groups(P<0.05).In vivo,Stent III made no difference from naked FCSEMS in serological analysis(P>0.05)and histopathological examination(P>0.05).CONCLUSION The novel SC and EDTA-eluting FCSEMS is efficient in diminishing CBDS in vitro.When conventional endoscopic techniques fa展开更多
The main contribution in this article is threefold:(1)we show the necessary and sufficient condition for graphs to be fractional(g,f)-covered which can be expressed in different forms,and extended to fractional(g,f,m)...The main contribution in this article is threefold:(1)we show the necessary and sufficient condition for graphs to be fractional(g,f)-covered which can be expressed in different forms,and extended to fractional(g,f,m)-covered graphs;(2)the concept of fractional-critical covered graph is put forward and its necessary and sufficient condition is given;(3)we present the degree condition for a graph to be fractional(g,f,n′,m)-critical covered,and show that degree bound is sharp when m is small.Moreover,the related result in fractional((a,b,n′,m)-critical covered setting is also verified.展开更多
In polar regions, cloud and underlying ice-snow areas are difficult to distinguish in satellite images because of their high albedo in the visible band and low surface temperature of ice-snow areas in the infrared ban...In polar regions, cloud and underlying ice-snow areas are difficult to distinguish in satellite images because of their high albedo in the visible band and low surface temperature of ice-snow areas in the infrared band. A cloud detection method over ice-snow covered areas in Antarctica is presented. On account of different texture features of cloud and ice-snow areas, five texture features are extracted based on GLCM. Nonlinear SVM is then used to obtain the optimal classification hyperplane from training data. The experiment results indicate that this algorithm performs well in cloud detection in Antarctica, especially for thin cirrus detection. Furthermore, when images are resampled to a quarter or 1/16 of the full size, cloud percentages are still at the same level, while the processing time decreases exponentially.展开更多
BACKGROUND Given most patients with distal malignant biliary obstruction present in the nonresectable stage,palliative endoscopic biliary drainage with fully covered metal stent(FCMS)or uncovered metal stent(UCMS)is t...BACKGROUND Given most patients with distal malignant biliary obstruction present in the nonresectable stage,palliative endoscopic biliary drainage with fully covered metal stent(FCMS)or uncovered metal stent(UCMS)is the only available measure to improve patients’quality of life.Half covered metal stent(HCMS)has been recently introduced commercially.The adverse effects and stent function between FCMS and UCMS have been extensively discussed.AIM To study the duration of stent patency of HCMS and compare it with FCMS and UCMS to optimize biliary drainage in inoperable patients with distal malignant obstruction.Secondary aims in our study included evaluation of patients’survival and the rates of adverse events for each type of stent.METHODS We studied 210 patients and randomized them into three equal groups;HCMS,FCMS and UCMS were inserted endoscopically.RESULTS Stent occlusion occurred in(18.6%,17.1%and 15.7%in HCMS,FCMS and UCMS groups,respectively,P=0.9).Stent migration occurred only in patients with FCMS(8.6%of patients).Cholangitis and cholecystitis occurred in 11.4%and 5.7%of patients,respectively,in FCMS.Tumor growth occurred only in 10 cases among patients with UCMS after a median of 140 d,sludge occurred in nine,seven and one patients in HCMS,FCMS and UCMS,respectively(P=0.04).CONCLUSION Given the prolonged stent functioning time,the use of HCMS is preferred over the use of UCMS and FCMS for optimizing biliary drainage in patients with distal malignant biliary obstruction.展开更多
Reactive fragment enhances lethality by incorporating the defeat mechanisms of kinetic energy and chemical energy into a unitary damage unit. Combined studies on the behavior of reactive fragment initiating covered ex...Reactive fragment enhances lethality by incorporating the defeat mechanisms of kinetic energy and chemical energy into a unitary damage unit. Combined studies on the behavior of reactive fragment initiating covered explosive are performed theoretically and experimentally. The results in- dicate that the response of the covered explosive subjected to reactive fragment is not consistent with the classical shock initiation model. When impacting and penetrating into the covered explosive, the reactive fragment releases great amounts of thermo-chemical energy up to 5. 68 times of its kinetic energy into the explosive due to violent chemical reactions. This impact-induced chemical energy re- lease behavior of the reactive fragment significantly enhances the initiation capability and damage effects on the covered explosive.展开更多
The thick-bedded and continuous karst crust only formed in the old stage of geomorphic development. The corresponding landscape is the karst planation surface. The karst planation surface consists of the loose weather...The thick-bedded and continuous karst crust only formed in the old stage of geomorphic development. The corresponding landscape is the karst planation surface. The karst planation surface consists of the loose weathering crust and the base weathering front below the crust. Its profile structure is similar to 'double surface of leveling' model built by Budel. In the limestone area, the base weathering front is the covered karst. From the Tibet Plateau to Yun-Gui (Yunnan- Guizhou) plateau and Xiang-Gui (Hunan-Guangxi) hills, the covered karst is concomitant with the red weathering crust; all of them are the component of the double-level surfaces of karst planation. But, they belong to the different disintegration stages of planation surface. The different subtypes of the covered karst and the red weathering crust indicate the existence of karst planation surface. Thus, they can be made as a reference system when the rising degree and the rising rate of the Tibet Plateau are discussed.展开更多
AIM:To present a series of covered self-expandable metal stents(CSEMS) placed for different indications and to evaluate the effectiveness,complications and extractability of these devices.METHODS:We therefore retrosp... AIM:To present a series of covered self-expandable metal stents(CSEMS) placed for different indications and to evaluate the effectiveness,complications and extractability of these devices.METHODS:We therefore retrospectively reviewed the courses of patients who received CSEMS due to malignant as well as benign biliary strictures and postsphincterotomy bleeding in our endoscopic unit between January 2010 and October 2011.RESULTS:Twenty-six patients received 28 stents due to different indications(20 stents due to malignant biliary strictures,six stents due to benign biliary strictures and two stents due to post-sphincterotomy bleeding).Biliary obstruction was relieved in all cases,regardless of the underlying cause.Hemostasis could be achieved in the two patients who received the stents for this purpose.Complications occurred in five patients(18%).Two patients(7%) developed cholecystitis,stents dislocated/migrated in other two patients(7%),and in one patient(3.6%) stent occlusion was documented during the study period.Seven stents were extracted endoscopically.Removal of stents was easily possible in all cases in which it was desired using standard forceps.Twelve patients underwent surgery with pylorus preserving duodenopancreatectomy.In all patients stents could be removed during the operation without difficulties.CONCLUSION:Despite the higher costs of these devices,fully covered self-expanding metal stents may be suitable to relief biliary obstruction due to bile duct stenosis,regardless of the underlying cause.CSEMS may also represent an effective treatment strategy of severe post-sphincterotomy bleeding,not controlled by other measures.展开更多
Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspens...Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspension insulator string,measuring method and analysis of the leakage current are developed for ice-covered XWP_2-160 porcelain suspension insulator string in this paper.The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover,in which the process can be divided into four periods according to the evolution of the leakage current.There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage,and the distortion on the leakage current waveform is detected because of the effect of arc discharge.A characteristic current(I_w)and a critical current(I_(FT))of flashover,two important parameters of the leakage current before ice-covered insulator string flashover,are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice.Statistical experimental results show that the average values of I_w and I_(FT) are within the major distribution zones,and both currents can be used for predicting the icing flashover.The values of two important leakage currents are approximately constant at different contamination degrees,while the direct relationships between the critical currents and the contamination degrees are not found in this paper.展开更多
This article, based on the field work took place on the zone of Tuomuer （托木尔） Peak, western Tian Shan （天山 ） during the period May 2008 to September 2009, obtained the spatial distribution of debris layer on t...This article, based on the field work took place on the zone of Tuomuer （托木尔） Peak, western Tian Shan （天山 ） during the period May 2008 to September 2009, obtained the spatial distribution of debris layer on the reference glaciers （Glacier No. 72, Glacier No. 74, Tuomuer Glacier） by detailed measurements of debris thickness and ablation rates on glacier and further by Spot-5 （5 m, 2005） high-resolution satellitic image applying remote sensing and geographic information systems approach to research the spatial distribution of debris layer on the zone of Tuomuer Peak. Specifically, the results indicate a sharp in ablation with debris cover thickness increasing from 0-4 cm followed by a decrease in ablation with debris thickness increasing beyond 4 cm for the glaciers No. 72 and No. 74. Spatial distributions of debris layer on the three reference glaciers have the same characteristics, the overall distribution from the vertical, the maximum thickness of debris in the glacier terminal, and the thickness of debris is constantly thinning since the end of the glacier increases with altitude. For the overall distribution from the horizontal, the regular pattern of debris thickness from both sides to the middle is diminishing. The debris on the zone of Tuomuer Peak mostly covered the glacier tongue and is mainly distributed below the altitude of 4 000 m; the area of debris covered approximate accounted for 14.9% on the entire glacier area in this region. Spatial distribution of debris layer on the zone of Tuomuer Peak is mainly affected by the elevation of the glacier terminal, followed by the slopes orientation, the sizes, and so on.展开更多
基金This work is supported by the National Natural Science Foundation of China (No. 50077017) and the U.S.National Science Foundation. X.-C. Zhang is the author to whom the correspondence should be addressed,
文摘We observe enhanced terahertz (THz) radiation generated from a Si3N4 film-coated GaAs photoconductive dipole antenna. Compared to an uncoated antenna with identical electrode geometry and optical excitation power, the Si3N4 film-coated antenna has a higher effective DC resistance and larger breakdown voltage. As a result, the peak amplitude of generated THz radiation is significantly enhanced due to the Si3N4 film-coated layer.
文摘Background Spontaneous direct carotid-cavernous fistula （CCF） is relatively rare and few reports have been found in the literature. The aim of this paper was to report the clinical characteristics, imaging findings and curative effect of endovascular treatment for patients with spontaneous direct CCF. Methods We retrospectively analyzed the clinical data of nine patients with spontaneous direct CCF admitted between May 2003 and November 2007 and the outcomes.of endovascular treatment. Sudden neuro-ophthalmological symptoms were the most common clinical presentation at diagnosis （n=8）. No patients had a history of head trauma. Cerebral digital subtraction angiography （DSA） was performed on all cases under local anesthesia and seven cases received endovascular treatment. Results In eight patients, internal carotid angiograms recorded during the early arterial phase revealed aneurysms located in the cavernous sinuses, and in one patient, a dilated internal carotid artery （ICA） was seen. Among the nine cases, seven received endovascular treatment via a transarterial approach and complete occlusion of the fistula was obtained with no technique-related complications, one died suddenly before treatment and one gave up treatment. A detachable balloon was used as the embolic material in two cases, a detachable balloon and detachable coil as the embolic material in two cases, balloon-assisted coil embolization in two cases and covered stents were successfully placed in the parent vessel to exclude the aneurysm and fistula from circulation in one case. During a follow-up period of 3-48 months, all treated patients remained asymptomatic except for one patient who suffered from ipsilateral decreased vision. Conclusions Most spontaneous direct CCF may be caused by a ruptured intracavernous aneurysm with direct shunting into the cavernous sinus. Endovascular treatment seems to be a safe and effective method for treating spontaneous direct CCF.
基金Supported by Science and Technology Planning Project of Guangdong Province,China,No.2012B010200027The Key Technologies RD Program of Guangzhou,ChinaThe Presidential Foundation of the Nanfang Hospital,Southern Medical University,Guangzhou,China,No.2011B006
文摘AIM: To evaluate transjugular intrahepatic portosystemic shunt (TIPS) with covered stents for hepatocellular carcinoma (HCC) with main portal vein tumor thrombus (PVTT).
文摘AIM: To investigate the use of fully covered metal stents in benign biliary strictures (BBS) and bile leaks. METHODS: We studied 17 patients, at Harbor-UCLA Medical center (Los Angeles), with BBS (n=12) and bile leaks (n=5) from July 2007 to February 2012 that had received placement of fully covered self-expanding metal stents (FCSEMs). Fourteen patients had endoscopic placement of VIABIL (Conmed, Utica, New York, United States) stents and three had Wallflex (Boston Scientific, Mass) stents. FCSEMS were 8 mm or 10 mm in diameter and 4 cm to 10 cm in length. Patients were followed at regular intervals to evaluate for symptoms and liver function tests. FCSEMS were removed after 4 or more weeks. Resolution of BBS and leak was documented cholangiographically following stent removal. Stent patency can be defined as adequate bile and contrast flow from the stent and into the ampulla during endoscopic retrograde cholangiopancreatography (ERCP) without clinical signs and/or symptoms of biliary obstruction. Criterion for bile leak resolution at ERCP is defined as absence of contrast extravasation from the common bile duct, cystic duct remanent, or gall blad-der fossa. Rate of complications such as migration, and instent occlusion were recorded. Failure of endoscopic therapy was defined as persistent biliary stenosis or continuous biliary leakage after 12 mo of stent placement. RESULTS: All 17 patients underwent successful FC- SEMS placement and removal. Etiologies of BBS included: cholecystectomies (n=8), cholelithiasis (n=2), hepatic artery compression (n=1), pancreatitis (n=2), and Whipple procedure (n=1). All bile leaks occurred following cholecystectomy. The anatomic location of BBS varied: distal common bile duct (n=7), common hepatic duct (n=1), hepaticojejunal anastomosis (n=2), right intrahepatic duct (n=1), and choledochoduo-denal anastomatic junction (n=1). All bile leaks were found to be at the cystic duct. Twelve of 17 patients had failed prior stent placement or exchange. Resolution of the biliary strictures
基金financially supported by the National Natural Scientific Fund of China(grant number 81771951)the Science and Technology Commission of Shanghai(grant number 14DZ1941204)
文摘Background Despite the current availability of flow diverter devices(FDD), problems remains regarding optimal endovascular treatment(EVT) for blood blister-like aneurysms(BBAs) of the internal carotid artery(ICA). Objective To evaluate the safety and efficacy of EVT of BBAs in the ICA with a Willis covered stent. Methods 20 consecutive patients(5 men and 15 women) with ruptured BBAs underwent EVT using a Willis covered stent in two institutions from March 2013 to March 2018. Clinical observations, angiographic characteristics, and procedural and follow-up outcomes were retrospectively evaluated. Results 20 consecutive patients(5 men and 15 women) with ruptured BBAs underwent EVT using a Willis covered stent in two institutions from March 2013 to March 2018. Clinical observations, angiographic characteristics, and procedural and follow-up outcomes were retrospectively evaluated. Conclusion Our initial results demonstrate that reconstructive EVT using a Willis covered stent provides a viable approach to treat ICA BBAs. However, an expanded clinical evaluation and larger cohort are needed to confirm the results.
基金the National Natural Science Foundation of China,No.81470904and Shanghai Committee of Science and Technology,No.14411963000
文摘BACKGROUND The treatment of difficult common bile duct stones(CBDS)remains a big challenge around the world.Biliary stenting is a widely accepted rescue method in patients with failed stone extraction under endoscopic retrograde cholangiopancreatography.Fully covered self-expanding metal stent(FCSEMS)has gained increasing attention in the management of difficult CBDS.AIM To manufacture a drug-eluting FCSEMS,which can achieve controlled release of stone-dissolving agents and speed up the dissolution of CBDS.METHODS Customized covered nitinol stents were adopted.Sodium cholate(SC)and disodium ethylene diamine tetraacetic acid(EDTA disodium,EDTA for short)were used as stone-dissolving agents.Three different types of drug-eluting stents were manufactured by dip coating(Stent I),coaxial electrospinning(Stent II),and dip coating combined with electrospinning(Stent III),respectively.The drugrelease behavior and stone-dissolving efficacy of these stents were evaluated in vitro to sort out the best manufacturing method.And the selected stonedissolving stents were further put into porcine CBD to evaluate their biosecurity.RESULTS Stent I and Stent II had obvious burst release of drugs in the first 5 d while Stent III presented controlled and sustainable drug release for 30 d.In still buffer,the final stone mass-loss rate of each group was 5.19%±0.69%for naked FCSEMS,20.37%±2.13%for Stent I,24.57%±1.45%for Stent II,and 33.72%±0.67%for Stent III.In flowing bile,the final stone mass-loss rate of each group was 5.87%±0.25%for naked FCSEMS,6.36%±0.48%for Stent I,6.38%±0.37%for Stent II,and 8.15%±0.27%for Stent III.Stent III caused the most stone mass-loss no matter in still buffer or in flowing bile,which was significantly higher than those of other groups(P<0.05).In vivo,Stent III made no difference from naked FCSEMS in serological analysis(P>0.05)and histopathological examination(P>0.05).CONCLUSION The novel SC and EDTA-eluting FCSEMS is efficient in diminishing CBDS in vitro.When conventional endoscopic techniques fa
基金the National Natural Science Foundation of China(Nos.12161 and 12031018).
文摘The main contribution in this article is threefold:(1)we show the necessary and sufficient condition for graphs to be fractional(g,f)-covered which can be expressed in different forms,and extended to fractional(g,f,m)-covered graphs;(2)the concept of fractional-critical covered graph is put forward and its necessary and sufficient condition is given;(3)we present the degree condition for a graph to be fractional(g,f,n′,m)-critical covered,and show that degree bound is sharp when m is small.Moreover,the related result in fractional((a,b,n′,m)-critical covered setting is also verified.
基金Supported by the Antarctic Geography Information Acquisition and Environmental Change Research of China (No.14601402024-04-06).
文摘In polar regions, cloud and underlying ice-snow areas are difficult to distinguish in satellite images because of their high albedo in the visible band and low surface temperature of ice-snow areas in the infrared band. A cloud detection method over ice-snow covered areas in Antarctica is presented. On account of different texture features of cloud and ice-snow areas, five texture features are extracted based on GLCM. Nonlinear SVM is then used to obtain the optimal classification hyperplane from training data. The experiment results indicate that this algorithm performs well in cloud detection in Antarctica, especially for thin cirrus detection. Furthermore, when images are resampled to a quarter or 1/16 of the full size, cloud percentages are still at the same level, while the processing time decreases exponentially.
文摘BACKGROUND Given most patients with distal malignant biliary obstruction present in the nonresectable stage,palliative endoscopic biliary drainage with fully covered metal stent(FCMS)or uncovered metal stent(UCMS)is the only available measure to improve patients’quality of life.Half covered metal stent(HCMS)has been recently introduced commercially.The adverse effects and stent function between FCMS and UCMS have been extensively discussed.AIM To study the duration of stent patency of HCMS and compare it with FCMS and UCMS to optimize biliary drainage in inoperable patients with distal malignant obstruction.Secondary aims in our study included evaluation of patients’survival and the rates of adverse events for each type of stent.METHODS We studied 210 patients and randomized them into three equal groups;HCMS,FCMS and UCMS were inserted endoscopically.RESULTS Stent occlusion occurred in(18.6%,17.1%and 15.7%in HCMS,FCMS and UCMS groups,respectively,P=0.9).Stent migration occurred only in patients with FCMS(8.6%of patients).Cholangitis and cholecystitis occurred in 11.4%and 5.7%of patients,respectively,in FCMS.Tumor growth occurred only in 10 cases among patients with UCMS after a median of 140 d,sludge occurred in nine,seven and one patients in HCMS,FCMS and UCMS,respectively(P=0.04).CONCLUSION Given the prolonged stent functioning time,the use of HCMS is preferred over the use of UCMS and FCMS for optimizing biliary drainage in patients with distal malignant biliary obstruction.
基金Supported by the National Innovation Funds(7130619)
文摘Reactive fragment enhances lethality by incorporating the defeat mechanisms of kinetic energy and chemical energy into a unitary damage unit. Combined studies on the behavior of reactive fragment initiating covered explosive are performed theoretically and experimentally. The results in- dicate that the response of the covered explosive subjected to reactive fragment is not consistent with the classical shock initiation model. When impacting and penetrating into the covered explosive, the reactive fragment releases great amounts of thermo-chemical energy up to 5. 68 times of its kinetic energy into the explosive due to violent chemical reactions. This impact-induced chemical energy re- lease behavior of the reactive fragment significantly enhances the initiation capability and damage effects on the covered explosive.
基金This Project was supported by Research Project of the Tibet Plateau from Chinese Academy ofSciences (Grant Nos. KZ951-A1-204 KZ95T-06) the Key Foundation of National liasic Researches of China (Grant No. G1998040800).
文摘The thick-bedded and continuous karst crust only formed in the old stage of geomorphic development. The corresponding landscape is the karst planation surface. The karst planation surface consists of the loose weathering crust and the base weathering front below the crust. Its profile structure is similar to 'double surface of leveling' model built by Budel. In the limestone area, the base weathering front is the covered karst. From the Tibet Plateau to Yun-Gui (Yunnan- Guizhou) plateau and Xiang-Gui (Hunan-Guangxi) hills, the covered karst is concomitant with the red weathering crust; all of them are the component of the double-level surfaces of karst planation. But, they belong to the different disintegration stages of planation surface. The different subtypes of the covered karst and the red weathering crust indicate the existence of karst planation surface. Thus, they can be made as a reference system when the rising degree and the rising rate of the Tibet Plateau are discussed.
文摘 AIM:To present a series of covered self-expandable metal stents(CSEMS) placed for different indications and to evaluate the effectiveness,complications and extractability of these devices.METHODS:We therefore retrospectively reviewed the courses of patients who received CSEMS due to malignant as well as benign biliary strictures and postsphincterotomy bleeding in our endoscopic unit between January 2010 and October 2011.RESULTS:Twenty-six patients received 28 stents due to different indications(20 stents due to malignant biliary strictures,six stents due to benign biliary strictures and two stents due to post-sphincterotomy bleeding).Biliary obstruction was relieved in all cases,regardless of the underlying cause.Hemostasis could be achieved in the two patients who received the stents for this purpose.Complications occurred in five patients(18%).Two patients(7%) developed cholecystitis,stents dislocated/migrated in other two patients(7%),and in one patient(3.6%) stent occlusion was documented during the study period.Seven stents were extracted endoscopically.Removal of stents was easily possible in all cases in which it was desired using standard forceps.Twelve patients underwent surgery with pylorus preserving duodenopancreatectomy.In all patients stents could be removed during the operation without difficulties.CONCLUSION:Despite the higher costs of these devices,fully covered self-expanding metal stents may be suitable to relief biliary obstruction due to bile duct stenosis,regardless of the underlying cause.CSEMS may also represent an effective treatment strategy of severe post-sphincterotomy bleeding,not controlled by other measures.
文摘Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspension insulator string,measuring method and analysis of the leakage current are developed for ice-covered XWP_2-160 porcelain suspension insulator string in this paper.The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover,in which the process can be divided into four periods according to the evolution of the leakage current.There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage,and the distortion on the leakage current waveform is detected because of the effect of arc discharge.A characteristic current(I_w)and a critical current(I_(FT))of flashover,two important parameters of the leakage current before ice-covered insulator string flashover,are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice.Statistical experimental results show that the average values of I_w and I_(FT) are within the major distribution zones,and both currents can be used for predicting the icing flashover.The values of two important leakage currents are approximately constant at different contamination degrees,while the direct relationships between the critical currents and the contamination degrees are not found in this paper.
基金supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX2-EW-311)the National Basic Research Program of China (No. 2010CB951003)+1 种基金the National Natural Science Foundation of China (Nos. 1141001040, J0930003/J0109)the SKLCS Founding (No. SKLCS-ZZ-2010-04)
文摘This article, based on the field work took place on the zone of Tuomuer （托木尔） Peak, western Tian Shan （天山 ） during the period May 2008 to September 2009, obtained the spatial distribution of debris layer on the reference glaciers （Glacier No. 72, Glacier No. 74, Tuomuer Glacier） by detailed measurements of debris thickness and ablation rates on glacier and further by Spot-5 （5 m, 2005） high-resolution satellitic image applying remote sensing and geographic information systems approach to research the spatial distribution of debris layer on the zone of Tuomuer Peak. Specifically, the results indicate a sharp in ablation with debris cover thickness increasing from 0-4 cm followed by a decrease in ablation with debris thickness increasing beyond 4 cm for the glaciers No. 72 and No. 74. Spatial distributions of debris layer on the three reference glaciers have the same characteristics, the overall distribution from the vertical, the maximum thickness of debris in the glacier terminal, and the thickness of debris is constantly thinning since the end of the glacier increases with altitude. For the overall distribution from the horizontal, the regular pattern of debris thickness from both sides to the middle is diminishing. The debris on the zone of Tuomuer Peak mostly covered the glacier tongue and is mainly distributed below the altitude of 4 000 m; the area of debris covered approximate accounted for 14.9% on the entire glacier area in this region. Spatial distribution of debris layer on the zone of Tuomuer Peak is mainly affected by the elevation of the glacier terminal, followed by the slopes orientation, the sizes, and so on.
