The method of volume identification in pneumatics was studied through theoretical analysis and experimental investigation. Regarding discharging from a container as a thermodynamic process with invariable index the d...The method of volume identification in pneumatics was studied through theoretical analysis and experimental investigation. Regarding discharging from a container as a thermodynamic process with invariable index the dependence of the container’s volume on the pressure in the container and the index, during discharging at the velocity of sound, is deduced. Then through a lot of experiments, the value of index n of the process is found with a given precision and a specified volume range. Furthermore, the feasibility and practicability of this method are verified by experiments.展开更多
For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic...For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic theory of leakage detection and location was introduced. Then the physical relationship between instantaneous energy and structural state variation of a system was analyzed theoretically. With HILBERT-HUANG transformation (HHT), the instantaneous energy distribution feature of an unstable acoustic signal was obtained. According to the relative contribution method of the instantaneous energy, the noise in signal was eliminated effectively. Furthermore, in order to judge the leakage, the typical characteristic of the instantaneous energy of signal in the input and output end was discussed using correlative analysis. A number of experiments were carried out to classify the leakage from normal operations, and the results show that the leakages are successfully detected and the average recognition rate reaches 93.3% among three group samples. It is shown that the method using acoustic technique with IED and correlative analysis is effective and it may be referred in other pipelines.展开更多
A leak detection method based on Bayesian theory and Fisher’s law was developed for water distribution systems. A hydraulic model was associated with the parameters of leaks (location, extent). The randomness of para...A leak detection method based on Bayesian theory and Fisher’s law was developed for water distribution systems. A hydraulic model was associated with the parameters of leaks (location, extent). The randomness of parameter values was quantified by probability density function and updated by Bayesian theory. Values of the parameters were estimated based on Fisher’s law. The amount of leaks was estimated by back propagation neural network. Based on flow characteristics in water distribution systems, the location of leaks can be estimated. The effectiveness of the proposed method was illustrated by simulated leak data of node pressure head and flow rate of pipelines in a test pipe network, and the leaks were spotted accurately and renovated on time.展开更多
Pipeline in te grity defect is a considerable portion in all the defects.Therefore, the study o n detection technique is of great concern to the owners of pipelines. A real ti me monitoring system of pipeline defect i...Pipeline in te grity defect is a considerable portion in all the defects.Therefore, the study o n detection technique is of great concern to the owners of pipelines. A real ti me monitoring system of pipeline defect is established. For unexpected accidents of pipeline leakage, several methods of signal processing, including wavelet an alysis are utilized. The leakage can be located accurately in time. This system is applied to many long distance pipelines in China, which has made great contri butions to the economy.展开更多
AIM： To evaluate the efficacy of endoscopic treatment in patients who undergo OLTx or LRLTx and develop biliary complications. METHODS： This is a prospective, observational study of patients who developed biliary co...AIM： To evaluate the efficacy of endoscopic treatment in patients who undergo OLTx or LRLTx and develop biliary complications. METHODS： This is a prospective, observational study of patients who developed biliary complications, after OLTx and LRLTx, with duct-to-duct anastomosis performed between June 2003 and June 2007. Endoscopic Retrograde Cholangiopancreatography （ERCP） was considered unsuccessful when there was evidence of continuous bile leakage despite endoscopic stent placement, or persistence of stenosis after i year, despite multiple dilatation and stent placement. When the ERCP failed, a percutaneous trans-hepatic approach （PTC） or surgery was adopted. RESULTS： From June 2003 to June 2007, 261 adult patients were transplanted in our institute, 68 from living donors and 193 from cadaveric donors. In the OLTx group the rate of complications was 37.3%, while in the LRLTx group was 64.7%. The rate of ERCP failure was 19.4% in the OLTx group and 38.6% in LRLTx group. In OLTx group, i patient was retransplanted and 8 patients died. In the LRLTx group, 2 patients underwent OLTx and 8 patients died. The follow-up was 23.3±13.13 mo and 21.02± 14.10 mo, respectively.CONCLUSION： Albhough ERCP is quite an effective mode of managing post-transplant bile duct complications, a significant number of patients need other types of approach. Further prospective studies are necessary in order to establish whebher obher endoscopic protocols or new devices, could improve bhe current results.展开更多
In this paper,we propose a hybrid power model that includes the power consumption of not only the registers but also part of the combinational logic.By doing knownkey analysis with this hybrid model,power side-channel...In this paper,we propose a hybrid power model that includes the power consumption of not only the registers but also part of the combinational logic.By doing knownkey analysis with this hybrid model,power side-channel leakage caused by correct keys can be detected.In experiment,PRINTcipher and DES algorithms were chosen as analysis targets and combinational logic s-box unit was selected to build power template.The analysis results showed the signal-to-noise ratio(SNR) power consumption increase of more than 20%after considering s-box's power consumption so that the information of keys can be obtained with just half number of power traces.In addition,the side channel-leakage detection capability of our method also shows better effectiveness that can identify the correct keys.展开更多
With the widespread application and fast development of gas and oil pipeline network in China, the pipeline inspection technology has been used more extensively. The magnetic flux leakage （MFL） method has establishe...With the widespread application and fast development of gas and oil pipeline network in China, the pipeline inspection technology has been used more extensively. The magnetic flux leakage （MFL） method has established itself as the most widely used in-line inspection technique for the evaluation of gas and oil pipelines. The MFL data obtained from seamless pipeline inspection is usually contaminated by the seamless pipe noise （SPN）. SPN can in some cases completely mask MFL signals from certain type of defects, and therefore considerably reduces the detectability of the defect signals. In this paper, a new de-noising algorithm called wavelet domain adaptive filtering is proposed for removing the SPN contained in the MFL data. The new algorithm results from combining the wavelet transform with the adaptive filtering technique. Results from application of the proposed algorithm to the MFL data from field tests show that the proposed algorithm has good performance and considerably improves the detectability of the defect signals in the MFL data.展开更多
The hydrogen leakage detection and alarm processing system is established for the fuel cell （FC） power train lab to meet the hydrogen safety demand of the FC performance test and examination for the project named ＂...The hydrogen leakage detection and alarm processing system is established for the fuel cell （FC） power train lab to meet the hydrogen safety demand of the FC performance test and examination for the project named ＂Research and Development of the Vehicular Technology for the Fuel Cell City Bus＂ by Tsinghua University. The established hydrogen safety system includes the hydrogen supply system, hydrogen leakage detection system, alarm processing system, ventilation system, measures against electrostatic, thunder-arresting and explosion-protection, and the strict hydrogen operation rules. In this safety system, the explosion proof catalytic combustion sensors are used to detect the hydrogen leakage and the electrical control system is designed to process the alarm automatically. The hydrogen safety system plays an important role in the performance, examination of the FC and the assuring the personnel＇ s safety of the fuel cell power train lab.展开更多
文摘The method of volume identification in pneumatics was studied through theoretical analysis and experimental investigation. Regarding discharging from a container as a thermodynamic process with invariable index the dependence of the container’s volume on the pressure in the container and the index, during discharging at the velocity of sound, is deduced. Then through a lot of experiments, the value of index n of the process is found with a given precision and a specified volume range. Furthermore, the feasibility and practicability of this method are verified by experiments.
基金Project(51004005) supported by the National Natural Science Foundation of ChinaProject supported by Open Research Fund Program of Beijing Engineering Research Center of Monitoring for Construction Safety (Beijing University of Civil Engineering and Architecture), China
文摘For solving the difficult problem of leakage detection in city gas pipelines, a method using acoustic technique based on instantaneous energy (IE) distribution and correlation analysis was proposed. Firstly, the basic theory of leakage detection and location was introduced. Then the physical relationship between instantaneous energy and structural state variation of a system was analyzed theoretically. With HILBERT-HUANG transformation (HHT), the instantaneous energy distribution feature of an unstable acoustic signal was obtained. According to the relative contribution method of the instantaneous energy, the noise in signal was eliminated effectively. Furthermore, in order to judge the leakage, the typical characteristic of the instantaneous energy of signal in the input and output end was discussed using correlative analysis. A number of experiments were carried out to classify the leakage from normal operations, and the results show that the leakages are successfully detected and the average recognition rate reaches 93.3% among three group samples. It is shown that the method using acoustic technique with IED and correlative analysis is effective and it may be referred in other pipelines.
基金Supported by National Natural Science Foundation of China (No. 50278062 and 50578108)Science and Technology Innovation Funds Project of Tianjin, China (No. 08FDZDSF03200)
文摘A leak detection method based on Bayesian theory and Fisher’s law was developed for water distribution systems. A hydraulic model was associated with the parameters of leaks (location, extent). The randomness of parameter values was quantified by probability density function and updated by Bayesian theory. Values of the parameters were estimated based on Fisher’s law. The amount of leaks was estimated by back propagation neural network. Based on flow characteristics in water distribution systems, the location of leaks can be estimated. The effectiveness of the proposed method was illustrated by simulated leak data of node pressure head and flow rate of pipelines in a test pipe network, and the leaks were spotted accurately and renovated on time.
文摘Pipeline in te grity defect is a considerable portion in all the defects.Therefore, the study o n detection technique is of great concern to the owners of pipelines. A real ti me monitoring system of pipeline defect is established. For unexpected accidents of pipeline leakage, several methods of signal processing, including wavelet an alysis are utilized. The leakage can be located accurately in time. This system is applied to many long distance pipelines in China, which has made great contri butions to the economy.
文摘AIM： To evaluate the efficacy of endoscopic treatment in patients who undergo OLTx or LRLTx and develop biliary complications. METHODS： This is a prospective, observational study of patients who developed biliary complications, after OLTx and LRLTx, with duct-to-duct anastomosis performed between June 2003 and June 2007. Endoscopic Retrograde Cholangiopancreatography （ERCP） was considered unsuccessful when there was evidence of continuous bile leakage despite endoscopic stent placement, or persistence of stenosis after i year, despite multiple dilatation and stent placement. When the ERCP failed, a percutaneous trans-hepatic approach （PTC） or surgery was adopted. RESULTS： From June 2003 to June 2007, 261 adult patients were transplanted in our institute, 68 from living donors and 193 from cadaveric donors. In the OLTx group the rate of complications was 37.3%, while in the LRLTx group was 64.7%. The rate of ERCP failure was 19.4% in the OLTx group and 38.6% in LRLTx group. In OLTx group, i patient was retransplanted and 8 patients died. In the LRLTx group, 2 patients underwent OLTx and 8 patients died. The follow-up was 23.3±13.13 mo and 21.02± 14.10 mo, respectively.CONCLUSION： Albhough ERCP is quite an effective mode of managing post-transplant bile duct complications, a significant number of patients need other types of approach. Further prospective studies are necessary in order to establish whebher obher endoscopic protocols or new devices, could improve bhe current results.
基金supported by Major State Basic Research Development Program(No. 2013CB338004)National Natural Science Foundation of China(No.61402286, 61472250,61472249,61202372)+1 种基金National Science and Technology Major Project of the Ministry of Science and Technology of China (No.2014ZX01032401-001)Plan of Action for the Innovation of Science and Technology of Shanghai Municipal Science and Technology Commission(No.14511100300)
文摘In this paper,we propose a hybrid power model that includes the power consumption of not only the registers but also part of the combinational logic.By doing knownkey analysis with this hybrid model,power side-channel leakage caused by correct keys can be detected.In experiment,PRINTcipher and DES algorithms were chosen as analysis targets and combinational logic s-box unit was selected to build power template.The analysis results showed the signal-to-noise ratio(SNR) power consumption increase of more than 20%after considering s-box's power consumption so that the information of keys can be obtained with just half number of power traces.In addition,the side channel-leakage detection capability of our method also shows better effectiveness that can identify the correct keys.
文摘With the widespread application and fast development of gas and oil pipeline network in China, the pipeline inspection technology has been used more extensively. The magnetic flux leakage （MFL） method has established itself as the most widely used in-line inspection technique for the evaluation of gas and oil pipelines. The MFL data obtained from seamless pipeline inspection is usually contaminated by the seamless pipe noise （SPN）. SPN can in some cases completely mask MFL signals from certain type of defects, and therefore considerably reduces the detectability of the defect signals. In this paper, a new de-noising algorithm called wavelet domain adaptive filtering is proposed for removing the SPN contained in the MFL data. The new algorithm results from combining the wavelet transform with the adaptive filtering technique. Results from application of the proposed algorithm to the MFL data from field tests show that the proposed algorithm has good performance and considerably improves the detectability of the defect signals in the MFL data.
文摘The hydrogen leakage detection and alarm processing system is established for the fuel cell （FC） power train lab to meet the hydrogen safety demand of the FC performance test and examination for the project named ＂Research and Development of the Vehicular Technology for the Fuel Cell City Bus＂ by Tsinghua University. The established hydrogen safety system includes the hydrogen supply system, hydrogen leakage detection system, alarm processing system, ventilation system, measures against electrostatic, thunder-arresting and explosion-protection, and the strict hydrogen operation rules. In this safety system, the explosion proof catalytic combustion sensors are used to detect the hydrogen leakage and the electrical control system is designed to process the alarm automatically. The hydrogen safety system plays an important role in the performance, examination of the FC and the assuring the personnel＇ s safety of the fuel cell power train lab.
