The misoperation of hydraulic components such as pumps and valves in pressurized pipelines triggers water hammer phenomena and seriously threats the safe operation of hydraulic systems.At present,the main water hammer...The misoperation of hydraulic components such as pumps and valves in pressurized pipelines triggers water hammer phenomena and seriously threats the safe operation of hydraulic systems.At present,the main water hammer simulation methods are method of characteristics(MOC),and further investigation of new algorithms is needed.Therefore,a new method for simulating the water hammer using the finite volume method(FVM),semi-implicit method for pressure linked equations(SIMPLE)algorithm is proposed in the present work.Compared with the experimental data,the accuracy and reliability of the proposed algorithm are verified.Results show that the IAB,MIAB friction models not only predict the first pressure peak but also accurately predict the pressure attenuation.From the comparison of the MOC,SIMPLE algorithms,the results of the two algorithms are almost the same in front of the valve,while near the upstream tank,when using the same friction model,the pressure attenuation predicted by the SIMPLE algorithm is slightly greater than that of the MOC method and closer to the experimental data.Therefore,the newly proposed algorithm can serve as an alternative to the MOC method in simulating water hammer.The investigation enriches the numerical methods of hydraulic transients and lays the foundation for subsequent program development.展开更多
1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their...1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their incredible speed of development and wide-reaching impact,mobile communications serve as the cornerstone of the Internet of Everything,profoundly reshaping human cognitive abilities and ways of thinking.Furthermore,mobile communications are altering the patterns of production and life,driving leaps in productivity quality,and strongly promot-ing innovation within human civilization.展开更多
The linked simulation-optimization model can be used for solving a complex groundwater pollution source identification problem. Advanced simulators have been developed and successfully linked with numerous optimizatio...The linked simulation-optimization model can be used for solving a complex groundwater pollution source identification problem. Advanced simulators have been developed and successfully linked with numerous optimization algorithms for identification of groundwater pollution sources. However, the identification of pollution sources in a groundwater aquifer using linked simulation-optimization model has proven to be computationally expensive. To overcome this computational burden, an approximate simulator, the artificial neural network (ANN) model can be used as a surrogate model to replace the complex time-consuming numerical simulation model. However, for large-scale aquifer system, the performance of the ANN-based surrogate model is not satisfactory when a single ANN model is used to predict the concentration at different observation locations. In such a situation, the model efficiency can be enhanced by developing separate ANN model for each of the observation locations. The number of ANN models is equal to the number of observation wells in the aquifer. As a result, the complexity of the ANN-based simulation-optimization model will be related to the number of observation wells. Thus, this study used a modified formulation to find out the optimal numbers of observation wells which will eventually reduce the computational time of the model. The performance of the ANN-based simulation-optimization model is evaluated by identifying the groundwater pollutant sources of a hypothetical study area. The limited evaluation shows that the model has the potential for field application.展开更多
BACKGROUND Linked color imaging(LCI) is a method of endoscopic imaging that emphasizes slight differences in red mucosal color.AIM To evaluate LCI in diagnostic endoscopy of early gastric cancer and to compare LCI and...BACKGROUND Linked color imaging(LCI) is a method of endoscopic imaging that emphasizes slight differences in red mucosal color.AIM To evaluate LCI in diagnostic endoscopy of early gastric cancer and to compare LCI and pathological findings.METHODS Endoscopic images were obtained for 39 patients(43 lesions) with early gastric cancer. Three endoscopists evaluated lesion recognition with white light imaging(WLI) and LCI. Color values in Commission Internationale de l'Eclairage(CIE)1976 L*a*b* color space were used to calculate the color difference(ΔE) between cancer lesions and non-cancer areas. After endoscopic submucosal dissection,blood vessel density in the surface layer of the gastric epithelium was evaluated pathologically. The identical region of interest was selected for analyses of endoscopic images(WLI and LCI) and pathological analyses.RESULTS LCI was superior for lesion recognition(P < 0.0001), and ΔE between cancer and non-cancer areas was significantly greater with LCI than WLI(29.4 vs 18.6, P <0.0001). Blood vessel density was significantly higher in cancer lesions(5.96% vs4.15%, P = 0.0004). An a* cut-off of ≥ 24 in CIE 1976 L*a*b* color space identified a cancer lesion using LCI with sensitivity of 76.7%, specificity of 93.0%, and accuracy of 84.9%.CONCLUSION LCI is more effective for recognition of early gastric cancer compared to WLI as a result of improved visualization of changes in redness. Surface blood vessel density was significantly higher in cancer lesions, and this result is consistent with LCI image analysis.展开更多
The influence of dissolved oxygen content on the oxidative stability of a linked polymer solution (LPS) was studied by micro-filtration, dynamic light scattering and viscosity measurements. The results showed that at ...The influence of dissolved oxygen content on the oxidative stability of a linked polymer solution (LPS) was studied by micro-filtration, dynamic light scattering and viscosity measurements. The results showed that at the same temperature, the degree of the oxidative degradation of the LPS increased and the rapidity of the oxidative degradation was accelerated with the increase of the dissolved oxygen content. Consequently, the size of linked polymer coils (LPCs) of the LPS became small, and the plugging capability of the LPS decreased. At a fixed content of dissolved oxygen, with increasing degradation temperature, almost the same results were observed, namely, an increased degree of oxidative degradation, accelerated rapidity of the oxidative degradation and decreased plugging capacity, with decreased oxidative stability of LPS. At 90 °C, in the presence of oxygen, LPS lost its plugging capability after having been degraded for a period of time. But at 40 °C, LPS with low dissolved oxygen content could be stable for a long time. The decreased plugging ability of LPS after oxidative degradation is mainly caused by the decreased size and number of the LPCs due to the breaking of hydrolyzed polyacrylamide (HPAM) molecule segments and the structural changing of HPAM molecules.展开更多
Suzuki-Miyaura coupling reaction of N-protected 4-iodopheyl alanine isoxazoles with arylboronic acids,catalyzed by palladium,efficiently produce benzyl-N-（4-bipheyl）-2-（3-methyl-5（E）-2-aryl-1-ethenyl-4-isoxazolyl...Suzuki-Miyaura coupling reaction of N-protected 4-iodopheyl alanine isoxazoles with arylboronic acids,catalyzed by palladium,efficiently produce benzyl-N-（4-bipheyl）-2-（3-methyl-5（E）-2-aryl-1-ethenyl-4-isoxazolyl）-amino-2-oxoethyl）carba- mates in good yields.This process is first of its kind to construct carbon-carbon bond formation having biaryl motif on amino acid linked isoxazole moiety.展开更多
AIM： To evaluate the association between gastroesophageal reflux diseases （GERD） and coronary heart diseases. METHODS： One thousand nine hundred and seventy consecutive patients who attended our hospital were enro...AIM： To evaluate the association between gastroesophageal reflux diseases （GERD） and coronary heart diseases. METHODS： One thousand nine hundred and seventy consecutive patients who attended our hospital were enrolled. All of the patients who first attend our hospital were asked to respond to the F-scale questionnaire regardless of their chief complaints. All patients had a careful history taken, and resting echocardiography （ECG） was performed by physicians if the diagnostic necessity arose. Patients with ECG signs of coronary artery ischemia were defined as ST- segment depression based on the Minnesota code. RESULTS： Among 712 patients （36%） with GERD, ECG was performed in 171 （24%）, and ischemic changes were detected in eight （5%）. Four （50%） of these patients with abnormal findings upon ECG had no chest symptoms such as chest pain, chest oppression, or palpitations. These patients （0.6%; 4/712） were thought to have non-GERD heartburn, which may be related to ischemic heart disease. Of 281 patients who underwent ECG and did not have GERD symptoms, 20 （7%） had abnormal findings upon ECG. In patients with GERD symptoms and ECG signs of coronary artery ischemia, the prevalence of linked angina was considered to be 0.4% （8/1970 patients）.CONCLUSION： The present study suggested that ischemic heart disease might be found although a patient was referred to the hospital with a complaint of GERD symptoms. Physicians have to be concerned about missing clinically important coronary artery disease while evaluating patients for GERD symptoms.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52079140,52379095)。
文摘The misoperation of hydraulic components such as pumps and valves in pressurized pipelines triggers water hammer phenomena and seriously threats the safe operation of hydraulic systems.At present,the main water hammer simulation methods are method of characteristics(MOC),and further investigation of new algorithms is needed.Therefore,a new method for simulating the water hammer using the finite volume method(FVM),semi-implicit method for pressure linked equations(SIMPLE)algorithm is proposed in the present work.Compared with the experimental data,the accuracy and reliability of the proposed algorithm are verified.Results show that the IAB,MIAB friction models not only predict the first pressure peak but also accurately predict the pressure attenuation.From the comparison of the MOC,SIMPLE algorithms,the results of the two algorithms are almost the same in front of the valve,while near the upstream tank,when using the same friction model,the pressure attenuation predicted by the SIMPLE algorithm is slightly greater than that of the MOC method and closer to the experimental data.Therefore,the newly proposed algorithm can serve as an alternative to the MOC method in simulating water hammer.The investigation enriches the numerical methods of hydraulic transients and lays the foundation for subsequent program development.
基金supported by the National Key Research and Develop-ment Program of China(2019YFB1803400).
文摘1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their incredible speed of development and wide-reaching impact,mobile communications serve as the cornerstone of the Internet of Everything,profoundly reshaping human cognitive abilities and ways of thinking.Furthermore,mobile communications are altering the patterns of production and life,driving leaps in productivity quality,and strongly promot-ing innovation within human civilization.
文摘The linked simulation-optimization model can be used for solving a complex groundwater pollution source identification problem. Advanced simulators have been developed and successfully linked with numerous optimization algorithms for identification of groundwater pollution sources. However, the identification of pollution sources in a groundwater aquifer using linked simulation-optimization model has proven to be computationally expensive. To overcome this computational burden, an approximate simulator, the artificial neural network (ANN) model can be used as a surrogate model to replace the complex time-consuming numerical simulation model. However, for large-scale aquifer system, the performance of the ANN-based surrogate model is not satisfactory when a single ANN model is used to predict the concentration at different observation locations. In such a situation, the model efficiency can be enhanced by developing separate ANN model for each of the observation locations. The number of ANN models is equal to the number of observation wells in the aquifer. As a result, the complexity of the ANN-based simulation-optimization model will be related to the number of observation wells. Thus, this study used a modified formulation to find out the optimal numbers of observation wells which will eventually reduce the computational time of the model. The performance of the ANN-based simulation-optimization model is evaluated by identifying the groundwater pollutant sources of a hypothetical study area. The limited evaluation shows that the model has the potential for field application.
文摘BACKGROUND Linked color imaging(LCI) is a method of endoscopic imaging that emphasizes slight differences in red mucosal color.AIM To evaluate LCI in diagnostic endoscopy of early gastric cancer and to compare LCI and pathological findings.METHODS Endoscopic images were obtained for 39 patients(43 lesions) with early gastric cancer. Three endoscopists evaluated lesion recognition with white light imaging(WLI) and LCI. Color values in Commission Internationale de l'Eclairage(CIE)1976 L*a*b* color space were used to calculate the color difference(ΔE) between cancer lesions and non-cancer areas. After endoscopic submucosal dissection,blood vessel density in the surface layer of the gastric epithelium was evaluated pathologically. The identical region of interest was selected for analyses of endoscopic images(WLI and LCI) and pathological analyses.RESULTS LCI was superior for lesion recognition(P < 0.0001), and ΔE between cancer and non-cancer areas was significantly greater with LCI than WLI(29.4 vs 18.6, P <0.0001). Blood vessel density was significantly higher in cancer lesions(5.96% vs4.15%, P = 0.0004). An a* cut-off of ≥ 24 in CIE 1976 L*a*b* color space identified a cancer lesion using LCI with sensitivity of 76.7%, specificity of 93.0%, and accuracy of 84.9%.CONCLUSION LCI is more effective for recognition of early gastric cancer compared to WLI as a result of improved visualization of changes in redness. Surface blood vessel density was significantly higher in cancer lesions, and this result is consistent with LCI image analysis.
文摘The influence of dissolved oxygen content on the oxidative stability of a linked polymer solution (LPS) was studied by micro-filtration, dynamic light scattering and viscosity measurements. The results showed that at the same temperature, the degree of the oxidative degradation of the LPS increased and the rapidity of the oxidative degradation was accelerated with the increase of the dissolved oxygen content. Consequently, the size of linked polymer coils (LPCs) of the LPS became small, and the plugging capability of the LPS decreased. At a fixed content of dissolved oxygen, with increasing degradation temperature, almost the same results were observed, namely, an increased degree of oxidative degradation, accelerated rapidity of the oxidative degradation and decreased plugging capacity, with decreased oxidative stability of LPS. At 90 °C, in the presence of oxygen, LPS lost its plugging capability after having been degraded for a period of time. But at 40 °C, LPS with low dissolved oxygen content could be stable for a long time. The decreased plugging ability of LPS after oxidative degradation is mainly caused by the decreased size and number of the LPCs due to the breaking of hydrolyzed polyacrylamide (HPAM) molecule segments and the structural changing of HPAM molecules.
文摘Suzuki-Miyaura coupling reaction of N-protected 4-iodopheyl alanine isoxazoles with arylboronic acids,catalyzed by palladium,efficiently produce benzyl-N-（4-bipheyl）-2-（3-methyl-5（E）-2-aryl-1-ethenyl-4-isoxazolyl）-amino-2-oxoethyl）carba- mates in good yields.This process is first of its kind to construct carbon-carbon bond formation having biaryl motif on amino acid linked isoxazole moiety.
文摘AIM： To evaluate the association between gastroesophageal reflux diseases （GERD） and coronary heart diseases. METHODS： One thousand nine hundred and seventy consecutive patients who attended our hospital were enrolled. All of the patients who first attend our hospital were asked to respond to the F-scale questionnaire regardless of their chief complaints. All patients had a careful history taken, and resting echocardiography （ECG） was performed by physicians if the diagnostic necessity arose. Patients with ECG signs of coronary artery ischemia were defined as ST- segment depression based on the Minnesota code. RESULTS： Among 712 patients （36%） with GERD, ECG was performed in 171 （24%）, and ischemic changes were detected in eight （5%）. Four （50%） of these patients with abnormal findings upon ECG had no chest symptoms such as chest pain, chest oppression, or palpitations. These patients （0.6%; 4/712） were thought to have non-GERD heartburn, which may be related to ischemic heart disease. Of 281 patients who underwent ECG and did not have GERD symptoms, 20 （7%） had abnormal findings upon ECG. In patients with GERD symptoms and ECG signs of coronary artery ischemia, the prevalence of linked angina was considered to be 0.4% （8/1970 patients）.CONCLUSION： The present study suggested that ischemic heart disease might be found although a patient was referred to the hospital with a complaint of GERD symptoms. Physicians have to be concerned about missing clinically important coronary artery disease while evaluating patients for GERD symptoms.
