Plastic pipes reinforced by cross helically wound steel wires (PSP), which have exhibited excellent mechanical performance, consist of inner polyethylene (PE) layer, winding layer and outer PE layer. The winding layer...Plastic pipes reinforced by cross helically wound steel wires (PSP), which have exhibited excellent mechanical performance, consist of inner polyethylene (PE) layer, winding layer and outer PE layer. The winding layer is composed of two monolayers where steel wires are cross helically wound. An analytical procedure is developed to predict the short-term burst pressure of PSP as the monolayer is assumed to be elastic and orthotropic. The 3D anisotropic elasticity and Maximum Stress Failure Criterion are employed in the formulation of the elasticity problem. Good agreement between the theoretical results and the experimental data shows that the proposed approach can well predict the short-term burst pressure of PSP.展开更多
Cold-stretched pressure vessels from austenitic stainless steels （ASS） are widely used for storage and transportation of liquefied gases, and have such advantages as thin wall and light weight. Fatigue is an importa...Cold-stretched pressure vessels from austenitic stainless steels （ASS） are widely used for storage and transportation of liquefied gases, and have such advantages as thin wall and light weight. Fatigue is an important concern in these pressure vessels, which are subjected to alternative loads. Even though several codes and standards have guidelines on these pressure vessels, there are no relevant design methods on fatigue failure. To understand the fatigue properties of ASS 1.4301 （equivalents include UNS $30400 and AISI 304） in solution-annealed （SA） and cold-stretched conditions （9% strain level） and the response of fatigue properties to cold stretching （CS）, low-cycle fatigue （LCF） tests were performed at room temperature, with total strain amplitudes ranging from ：~0.4% to ＂0.8%. Martensite transformations were measured during the tests. Comparisons on cyclic stress response, cyclic stress-strain behavior, and fatigue life were carried out between SA and CS materials. Results show that CS reduces the initial hardening stage, but prolongs the softening period in the cyclic stress response. Martensite transformation helps form a stable regime and subsequent secondary hardening. The stresses of monotonic and cyclic stress-strain curves are improved by CS, which leads to a lower plastic strain and a much higher elastic strain. The fatigue resistance of the CS material is better than that of the SA material, which is approximately 1 - 103 to 2 - 104 cycles. The S-N curve of the ASME standard for ASS is compared with the fatigue data and is justified to be suitable for the fatigue design of cold-stretched pressure vessels. However, considering the CS material has a better fatigue resistance, the S-N curve will be more conservative. The present study would be helpful in making full use of the advantages of CS to develop a new S-N curve for fatigue design of cold-stretched pressure vessels.展开更多
This paper proposes a theoretical method using finite element analysis(FEA) to calculate the plastic collapse loads of pressure vessels under internal pressure,and compares the analytical methods according to three cr...This paper proposes a theoretical method using finite element analysis(FEA) to calculate the plastic collapse loads of pressure vessels under internal pressure,and compares the analytical methods according to three criteria stated in the ASME Boiler Pressure Vessel Code. First,a finite element technique using the arc-length algorithm and the restart analysis is developed to conduct the plastic collapse analysis of vessels,which includes the material and geometry non-linear properties of vessels. Second,as the mechanical properties of vessels are assumed to be elastic-perfectly plastic,the limit load analysis is performed by em-ploying the Newton-Raphson algorithm,while the limit pressure of vessels is obtained by the twice-elastic-slope method and the tangent intersection method respectively to avoid excessive deformation. Finally,the elastic stress analysis under working pressure is conducted and the stress strength of vessels is checked by sorting the stress results. The results are compared with those obtained by experiments and other existing models. This work provides a reference for the selection of the failure criteria and the calculation of the plastic collapse load.展开更多
As the idea of simulated annealing (SA) is introduced into the fitness function, an improved genetic algorithm (GA) is proposed to perform the optimal design of a pressure vessel which aims to attain the minimum weigh...As the idea of simulated annealing (SA) is introduced into the fitness function, an improved genetic algorithm (GA) is proposed to perform the optimal design of a pressure vessel which aims to attain the minimum weight under burst pressure con- straint. The actual burst pressure is calculated using the arc-length and restart analysis in finite element analysis (FEA). A penalty function in the fitness function is proposed to deal with the constrained problem. The effects of the population size and the number of generations in the GA on the weight and burst pressure of the vessel are explored. The optimization results using the proposed GA are also compared with those using the simple GA and the conventional Monte Carlo method.展开更多
大麻素受体与疼痛、炎症、骨质疏松等多种疾病紧密相关,是极具潜力的药物靶点。本研究分别选取吲哚类CB2选择性激动剂和CB1选择性激动剂为研究对象,采用Discovery studio 2019软件分别构建两种激动剂共同特征药效团模型,首次对这两种药...大麻素受体与疼痛、炎症、骨质疏松等多种疾病紧密相关,是极具潜力的药物靶点。本研究分别选取吲哚类CB2选择性激动剂和CB1选择性激动剂为研究对象,采用Discovery studio 2019软件分别构建两种激动剂共同特征药效团模型,首次对这两种药效团模型进行比较分析。随后通过测试集和ROC曲线两种验证方法对CB2选择性激动剂药效团模型的可靠性进行验证和筛选,得到一个最佳模型,该模型可用于天然化合物数据库的筛选,为发现新型CB2选择性激动剂提供理论基础。展开更多
To the Editor:The patient was a 16-year-old adolescent boy who was diagnosed with congenital megacolon.He had difficulty with defecating for more than 10 years.His bowel movements stopped more than 1 week ago.He was a...To the Editor:The patient was a 16-year-old adolescent boy who was diagnosed with congenital megacolon.He had difficulty with defecating for more than 10 years.His bowel movements stopped more than 1 week ago.He was admitted to the hospital with incomplete intestinal obstruction.The patient showed signs of moderate nutrition,poor mental health,and full abdominal bulging and had an abdominal circumference of 104 cm. Rectal examination showed blasting exhaust and defecation, and the anal pressure measurement value was 89 mmHg.The total abdominal augmentation computed tomography and total colorectal sputum angiography showed that the upper and middle rectum,descending colon,transverse colon,and ascending colon were dilated,the maximum diameter of the intestine was 23 cm,and the intestine was filled with feces, suggesting that the lower rectum and sigmoid colon were narrow [Figure 1a and 1b].展开更多
BACKGROUND Coronavirus disease 2019(COVID-19)has spread rapidly to multiple countries through its infectious agent severe acute respiratory syndrome coronavirus 2.The severity,atypical clinical presentation,and lack o...BACKGROUND Coronavirus disease 2019(COVID-19)has spread rapidly to multiple countries through its infectious agent severe acute respiratory syndrome coronavirus 2.The severity,atypical clinical presentation,and lack of specific anti-viral treatments have posed a challenge for the diagnosis and treatment of COVID-19.Understanding the epidemiological and clinical characteristics of COVID-19 cases in different geographical areas is essential to improve the prognosis of COVID-19 patients and slow the spread of the disease.AIM To investigate the epidemiological and clinical characteristics and main therapeutic strategy for confirmed COVID-19 patients hospitalized in Liaoning Province,China.METHODS Adult patients(n=65)with confirmed COVID-19 were enrolled in this retrospective study from January 20 to February 29,2020 in Liaoning Province,China.Pharyngeal swabs and sputum specimens were collected from the patients for the detection of severe acute respiratory syndrome coronavirus 2 nucleic acid.Patient demographic information and clinical data were collected from the medical records.Based on the severity of COVID-19,the patients were divided into nonsevere and severe groups. All patients were followed until March 20,2020.RESULTSThe mean age of 65 COVID-19 patients was 45.5 ± 14.4 years, 56.9% were men,and 24.6% were severe cases. During the 14 d before symptom onset, 25 (38.5%)patients lived or stayed in Wuhan, whereas 8 (12.3%) had no clear history ofexposure. Twenty-nine (44.6%) patients had at least one comorbidity;hypertension and diabetes were the most common comorbidities. Compared withnonsevere patients, severe patients had significantly lower lymphocyte counts[median value 1.3 × 10^(9)/L (interquartile range 0.9-1.95) vs 0.82 × 10^(9)/L (0.44-1.08),P < 0.001], elevated levels of lactate dehydrogenase [450 U/L (386-476) vs 707 U/L(592-980), P < 0.001] and C-reactive protein [6.1 mg/L (1.5-7.2) vs 52 mg/L (12.7-100.8), P < 0.001], and a prolonged median duration of viral shedding [19.5 d (16-21) vs 23.5 d (19.展开更多
基金the New Century Excellent Talents in University, MOE, China (No. NCET-04-0526)the Specialized Research Fund for the Doctoral Program of Higher Education, MOE, China (No. J20050398)the Key Project of Wenzhou (No. G2004034), China
文摘Plastic pipes reinforced by cross helically wound steel wires (PSP), which have exhibited excellent mechanical performance, consist of inner polyethylene (PE) layer, winding layer and outer PE layer. The winding layer is composed of two monolayers where steel wires are cross helically wound. An analytical procedure is developed to predict the short-term burst pressure of PSP as the monolayer is assumed to be elastic and orthotropic. The 3D anisotropic elasticity and Maximum Stress Failure Criterion are employed in the formulation of the elasticity problem. Good agreement between the theoretical results and the experimental data shows that the proposed approach can well predict the short-term burst pressure of PSP.
基金Project supported by the National Key Technology R&D Program (No.2011BAK06B0205)the International Science and Technology Cooperation Project (No. 2010DFB42960)the Key Technology Innovation Team of Zhejiang Province (No. 2010R50001),China
文摘Cold-stretched pressure vessels from austenitic stainless steels （ASS） are widely used for storage and transportation of liquefied gases, and have such advantages as thin wall and light weight. Fatigue is an important concern in these pressure vessels, which are subjected to alternative loads. Even though several codes and standards have guidelines on these pressure vessels, there are no relevant design methods on fatigue failure. To understand the fatigue properties of ASS 1.4301 （equivalents include UNS $30400 and AISI 304） in solution-annealed （SA） and cold-stretched conditions （9% strain level） and the response of fatigue properties to cold stretching （CS）, low-cycle fatigue （LCF） tests were performed at room temperature, with total strain amplitudes ranging from ：~0.4% to ＂0.8%. Martensite transformations were measured during the tests. Comparisons on cyclic stress response, cyclic stress-strain behavior, and fatigue life were carried out between SA and CS materials. Results show that CS reduces the initial hardening stage, but prolongs the softening period in the cyclic stress response. Martensite transformation helps form a stable regime and subsequent secondary hardening. The stresses of monotonic and cyclic stress-strain curves are improved by CS, which leads to a lower plastic strain and a much higher elastic strain. The fatigue resistance of the CS material is better than that of the SA material, which is approximately 1 - 103 to 2 - 104 cycles. The S-N curve of the ASME standard for ASS is compared with the fatigue data and is justified to be suitable for the fatigue design of cold-stretched pressure vessels. However, considering the CS material has a better fatigue resistance, the S-N curve will be more conservative. The present study would be helpful in making full use of the advantages of CS to develop a new S-N curve for fatigue design of cold-stretched pressure vessels.
基金Project (Nos. 2006BAK04A02-02 and 2006BAK02B02-08) supported by the National Key Technology R&D Program, China
文摘This paper proposes a theoretical method using finite element analysis(FEA) to calculate the plastic collapse loads of pressure vessels under internal pressure,and compares the analytical methods according to three criteria stated in the ASME Boiler Pressure Vessel Code. First,a finite element technique using the arc-length algorithm and the restart analysis is developed to conduct the plastic collapse analysis of vessels,which includes the material and geometry non-linear properties of vessels. Second,as the mechanical properties of vessels are assumed to be elastic-perfectly plastic,the limit load analysis is performed by em-ploying the Newton-Raphson algorithm,while the limit pressure of vessels is obtained by the twice-elastic-slope method and the tangent intersection method respectively to avoid excessive deformation. Finally,the elastic stress analysis under working pressure is conducted and the stress strength of vessels is checked by sorting the stress results. The results are compared with those obtained by experiments and other existing models. This work provides a reference for the selection of the failure criteria and the calculation of the plastic collapse load.
基金Project (Nos. 2006BAK04A02-02 and 2006BAK02B02-08) sup-ported by the National Key Technology R&D Program, China
文摘As the idea of simulated annealing (SA) is introduced into the fitness function, an improved genetic algorithm (GA) is proposed to perform the optimal design of a pressure vessel which aims to attain the minimum weight under burst pressure con- straint. The actual burst pressure is calculated using the arc-length and restart analysis in finite element analysis (FEA). A penalty function in the fitness function is proposed to deal with the constrained problem. The effects of the population size and the number of generations in the GA on the weight and burst pressure of the vessel are explored. The optimization results using the proposed GA are also compared with those using the simple GA and the conventional Monte Carlo method.
文摘大麻素受体与疼痛、炎症、骨质疏松等多种疾病紧密相关,是极具潜力的药物靶点。本研究分别选取吲哚类CB2选择性激动剂和CB1选择性激动剂为研究对象,采用Discovery studio 2019软件分别构建两种激动剂共同特征药效团模型,首次对这两种药效团模型进行比较分析。随后通过测试集和ROC曲线两种验证方法对CB2选择性激动剂药效团模型的可靠性进行验证和筛选,得到一个最佳模型,该模型可用于天然化合物数据库的筛选,为发现新型CB2选择性激动剂提供理论基础。
文摘To the Editor:The patient was a 16-year-old adolescent boy who was diagnosed with congenital megacolon.He had difficulty with defecating for more than 10 years.His bowel movements stopped more than 1 week ago.He was admitted to the hospital with incomplete intestinal obstruction.The patient showed signs of moderate nutrition,poor mental health,and full abdominal bulging and had an abdominal circumference of 104 cm. Rectal examination showed blasting exhaust and defecation, and the anal pressure measurement value was 89 mmHg.The total abdominal augmentation computed tomography and total colorectal sputum angiography showed that the upper and middle rectum,descending colon,transverse colon,and ascending colon were dilated,the maximum diameter of the intestine was 23 cm,and the intestine was filled with feces, suggesting that the lower rectum and sigmoid colon were narrow [Figure 1a and 1b].
基金Supported by 345 Talent Program of Shengjing HospitalScientific Research Projects Related to Prevention and Control of Coronavirus Disease 2019(COVID-19)of China Medical University,No.1210120010。
文摘BACKGROUND Coronavirus disease 2019(COVID-19)has spread rapidly to multiple countries through its infectious agent severe acute respiratory syndrome coronavirus 2.The severity,atypical clinical presentation,and lack of specific anti-viral treatments have posed a challenge for the diagnosis and treatment of COVID-19.Understanding the epidemiological and clinical characteristics of COVID-19 cases in different geographical areas is essential to improve the prognosis of COVID-19 patients and slow the spread of the disease.AIM To investigate the epidemiological and clinical characteristics and main therapeutic strategy for confirmed COVID-19 patients hospitalized in Liaoning Province,China.METHODS Adult patients(n=65)with confirmed COVID-19 were enrolled in this retrospective study from January 20 to February 29,2020 in Liaoning Province,China.Pharyngeal swabs and sputum specimens were collected from the patients for the detection of severe acute respiratory syndrome coronavirus 2 nucleic acid.Patient demographic information and clinical data were collected from the medical records.Based on the severity of COVID-19,the patients were divided into nonsevere and severe groups. All patients were followed until March 20,2020.RESULTSThe mean age of 65 COVID-19 patients was 45.5 ± 14.4 years, 56.9% were men,and 24.6% were severe cases. During the 14 d before symptom onset, 25 (38.5%)patients lived or stayed in Wuhan, whereas 8 (12.3%) had no clear history ofexposure. Twenty-nine (44.6%) patients had at least one comorbidity;hypertension and diabetes were the most common comorbidities. Compared withnonsevere patients, severe patients had significantly lower lymphocyte counts[median value 1.3 × 10^(9)/L (interquartile range 0.9-1.95) vs 0.82 × 10^(9)/L (0.44-1.08),P < 0.001], elevated levels of lactate dehydrogenase [450 U/L (386-476) vs 707 U/L(592-980), P < 0.001] and C-reactive protein [6.1 mg/L (1.5-7.2) vs 52 mg/L (12.7-100.8), P < 0.001], and a prolonged median duration of viral shedding [19.5 d (16-21) vs 23.5 d (19.
