It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 ...It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 times without maintenance during the lifetime of the pump. A theoretical analysis based on the nonlinear finite element method and an experimental investigation of the reusability of the C ring are carried out. The effects of the elastic modulus of the ring material, the ring wall thickness, the amount of assembly interference between the spring and the C ring, the operating temperature and the compression ratio are discussed. The parameter S, which denotes the reaction force difference percentage, is determined to measure the reusability of the C ring. The results show that the ring wall thickness plays an important role in the reusability. Although the normal force of a thick wall decreases after the ring is reused eight times, the value is still higher than the first normal force of a thin wall. In contrast, the elastic modulus of the material has the lowest impact. Here, a pre-compression ratio of 18.2% not only produces a larger first normal force but also leads to a smaller reduction in the normal force when the ring is reused. A simulated experiment is carried out to investigate the influence of the coating of the C ring on its reusability. The results show that when plastic deformation occurs on the contact surface, the contact state of the C ring coating becomes a major factor that affects the seal performance. Aging treatment at high temperatures （250℃） reduces gized metal C ring, which leads to the deterioration in the reusability the binding force of the silver coating on the spring ener of the ring.展开更多
Rana kunyuensis is a species of brown frog that lives exclusively on Kunyu Mountain,Yantai,China.In the current study,a 279-bp cDNA sequence encoding a novel antimicrobial peptide (AMP),designated as amurin-9KY,was cl...Rana kunyuensis is a species of brown frog that lives exclusively on Kunyu Mountain,Yantai,China.In the current study,a 279-bp cDNA sequence encoding a novel antimicrobial peptide (AMP),designated as amurin-9KY,was cloned from synthesized double-strand skin cDNA of R.kunyuensis.The amurin-9KY precursor was composed of 62 amino acid (aa) residues,whereas the mature peptide was composed of 14 aa and contained two cysteines forming a C-terminal heptapeptide ring (Rana box domain) and an amidated C-terminus.These structural characters represent a novel amphibian AMP family.Although amurin-9KY exhibited high similarity to the already identified amurin-9AM from R.amurensis,little is known about the structures and activities of amurin-9 family AMPs so far.Therefore,amurin-9KY and its three derivatives (amurin-9KY1-3) were designed and synthesized.The structures and activities were examined to evaluate the influence of C-terminal amidation and the heptapeptide ring on the activities and structure of amurin-9KY..Results indicated that C-terminal amidation was essential for antimicrobial activity,whereas both C-terminal amidation and the heptapeptide ring played roles in the low hemolytic activity.Circular dichroism (CD) spectra showed that the four peptides adopted an α-helical conformation in THF/H2O (v/v 1∶1) solution,but a random coil in aqueous solution.Elimination of the C-terminal heptapeptide ring generated two free cysteine residues with unpaired thiol groups,which greatly increased the concentration-dependent anti-oxidant activity.Scanning electron microscopy (SEM) was also performed to determine the possible bactericidal mechanisms.展开更多
A C/D ring synthon of vitamin D is readily obtained from cholesteryl acetate via oxidation, elimination of acetoxy group and Norrish type II photochemical reaction.
A selective ring-opening [3+2] cyclization reaction of benzo[d]isoxazoles with 2-bromo-propanamides has been developed.The azaoxyallyl cation intermediates are employed as C^O 3-atom synthon to build oxa-heterocycles ...A selective ring-opening [3+2] cyclization reaction of benzo[d]isoxazoles with 2-bromo-propanamides has been developed.The azaoxyallyl cation intermediates are employed as C^O 3-atom synthon to build oxa-heterocycles via the selectivity of suitable cyclization partners.This transformation provides rapid access to highly functionalized 2-hydroxyaryl-oxazolines under mild conditions and excellent regioselectivity.展开更多
伴随结构精细化、小型化的发展,薄板、薄壁管件等小尺寸构件得到应用,试样小型化对满足特殊取样要求和材料断裂韧度测试需求有重要工程意义,而基于非标小试样的材料断裂性能测试方法尚难满足需求。设计用于延性材料断裂韧度测试的C形环...伴随结构精细化、小型化的发展,薄板、薄壁管件等小尺寸构件得到应用,试样小型化对满足特殊取样要求和材料断裂韧度测试需求有重要工程意义,而基于非标小试样的材料断裂性能测试方法尚难满足需求。设计用于延性材料断裂韧度测试的C形环小试样,提出应用该类小尺寸试样获取材料延性断裂韧度的、基于量纲一载荷分离理论的规则化测试方法。分别采用C形环小试样和传统紧凑拉伸型(Compact tension,CT)大试样完成转子材料26Ni Cr Mo V11-5钢和压力容器材料A508-Ⅲ钢的J阻力曲线试验,讨论C形环小试样厚度、初始裂纹长度对试验结果的影响。结果表明,试样厚度和初始裂纹长度对C形环的J阻力曲线测试结果影响有限,但C形环试样裂尖具有更高的约束水平,由C形环试样得到的J阻力曲线明显低于CT试样的结果。展开更多
基金supported by the National Key S&T Special Project(Grant No.2012ZX06901-022)
文摘It is well known that static seals are usually designed to be used once. In this paper, we discuss the reusability of a type of static seal called the spring energized metal C ring, which is required to be reused 4-5 times without maintenance during the lifetime of the pump. A theoretical analysis based on the nonlinear finite element method and an experimental investigation of the reusability of the C ring are carried out. The effects of the elastic modulus of the ring material, the ring wall thickness, the amount of assembly interference between the spring and the C ring, the operating temperature and the compression ratio are discussed. The parameter S, which denotes the reaction force difference percentage, is determined to measure the reusability of the C ring. The results show that the ring wall thickness plays an important role in the reusability. Although the normal force of a thick wall decreases after the ring is reused eight times, the value is still higher than the first normal force of a thin wall. In contrast, the elastic modulus of the material has the lowest impact. Here, a pre-compression ratio of 18.2% not only produces a larger first normal force but also leads to a smaller reduction in the normal force when the ring is reused. A simulated experiment is carried out to investigate the influence of the coating of the C ring on its reusability. The results show that when plastic deformation occurs on the contact surface, the contact state of the C ring coating becomes a major factor that affects the seal performance. Aging treatment at high temperatures （250℃） reduces gized metal C ring, which leads to the deterioration in the reusability the binding force of the silver coating on the spring ener of the ring.
基金supported by grants from the National Natural Science Foundation of China(31772455)Natural Science Foundation of Jiangsu Province(BK20160336and BK20171214)+1 种基金Natural Science Foundation of College in Jiangsu Province(16KJB350004)Suzhou Science and Technology Development Project(SYN201504 and SNG2017045)
文摘Rana kunyuensis is a species of brown frog that lives exclusively on Kunyu Mountain,Yantai,China.In the current study,a 279-bp cDNA sequence encoding a novel antimicrobial peptide (AMP),designated as amurin-9KY,was cloned from synthesized double-strand skin cDNA of R.kunyuensis.The amurin-9KY precursor was composed of 62 amino acid (aa) residues,whereas the mature peptide was composed of 14 aa and contained two cysteines forming a C-terminal heptapeptide ring (Rana box domain) and an amidated C-terminus.These structural characters represent a novel amphibian AMP family.Although amurin-9KY exhibited high similarity to the already identified amurin-9AM from R.amurensis,little is known about the structures and activities of amurin-9 family AMPs so far.Therefore,amurin-9KY and its three derivatives (amurin-9KY1-3) were designed and synthesized.The structures and activities were examined to evaluate the influence of C-terminal amidation and the heptapeptide ring on the activities and structure of amurin-9KY..Results indicated that C-terminal amidation was essential for antimicrobial activity,whereas both C-terminal amidation and the heptapeptide ring played roles in the low hemolytic activity.Circular dichroism (CD) spectra showed that the four peptides adopted an α-helical conformation in THF/H2O (v/v 1∶1) solution,but a random coil in aqueous solution.Elimination of the C-terminal heptapeptide ring generated two free cysteine residues with unpaired thiol groups,which greatly increased the concentration-dependent anti-oxidant activity.Scanning electron microscopy (SEM) was also performed to determine the possible bactericidal mechanisms.
文摘A C/D ring synthon of vitamin D is readily obtained from cholesteryl acetate via oxidation, elimination of acetoxy group and Norrish type II photochemical reaction.
基金partial financial support from the Ministry of Science and Technology of China(No.2016YFE0132600)Zhengzhou University。
文摘A selective ring-opening [3+2] cyclization reaction of benzo[d]isoxazoles with 2-bromo-propanamides has been developed.The azaoxyallyl cation intermediates are employed as C^O 3-atom synthon to build oxa-heterocycles via the selectivity of suitable cyclization partners.This transformation provides rapid access to highly functionalized 2-hydroxyaryl-oxazolines under mild conditions and excellent regioselectivity.
文摘伴随结构精细化、小型化的发展,薄板、薄壁管件等小尺寸构件得到应用,试样小型化对满足特殊取样要求和材料断裂韧度测试需求有重要工程意义,而基于非标小试样的材料断裂性能测试方法尚难满足需求。设计用于延性材料断裂韧度测试的C形环小试样,提出应用该类小尺寸试样获取材料延性断裂韧度的、基于量纲一载荷分离理论的规则化测试方法。分别采用C形环小试样和传统紧凑拉伸型(Compact tension,CT)大试样完成转子材料26Ni Cr Mo V11-5钢和压力容器材料A508-Ⅲ钢的J阻力曲线试验,讨论C形环小试样厚度、初始裂纹长度对试验结果的影响。结果表明,试样厚度和初始裂纹长度对C形环的J阻力曲线测试结果影响有限,但C形环试样裂尖具有更高的约束水平,由C形环试样得到的J阻力曲线明显低于CT试样的结果。
