Type synthesis of mechanisms aims to systematically determine all possible structures for a specific mobility requirement. Numerous methods based on di erent theories were proposed for type synthesis of lower mobility...Type synthesis of mechanisms aims to systematically determine all possible structures for a specific mobility requirement. Numerous methods based on di erent theories were proposed for type synthesis of lower mobility parallel mechanisms in past decades. However, there does not exist a comprehensive review on these approaches. Therefore, the goal of this paper is to give such a review, classifying the approaches proposed in the literature into three groups, namely, motion-based methods, constraint-based methods, and other methods. The motion-based methods include the Lie group based method, the GF set method, the linear transformation method, the POC set method,and the finite screw method. The constraint-based methods involve the screw theory-based method, the virtual chain method, the method based on Grassmann line geometry and line graphs, and the motion constraint generator method. Other methods contain the enumeration approach based on the general CGK mobility formula and the graph theory method. Upon thoroughly analyzing the characteristics and/or limitations of each method, this review provides a well reference to help researchers find an e ective synthesis method for innovative design and further scientific investigations for mechanisms.展开更多
The main purpose of this paper is to study the lower order and type of second order differential equation w"(z)-A(z)w=0,where A(z)is a polynomial.In the case of A(z)=a_dz^d,the authors prove that the lower order ...The main purpose of this paper is to study the lower order and type of second order differential equation w"(z)-A(z)w=0,where A(z)is a polynomial.In the case of A(z)=a_dz^d,the authors prove that the lower order and the type of all non-trivial solutions w of w"(z)-A(z)w=0 are equal to(d+2)/2 and(2(|a_d|)^(1/2))/(d+2)respectively.In the case of A(z)=a_dz^d+a_(d-1)z^(d-1)+…a_1z+a_0,a_d>0,a_(d-1)>0,…,a_1≥0,a_0≥0,the authors prove that the lower order of all non-trivial solutions w of w"(z)-A(z)w=0 is(d+2)/2.展开更多
There are many advantages of combining incretin therapy[glucagon-like peptide-1(GLP-1)receptor agonists and dipeptidyl peptidase-4(DPP-4)inhibitors]with insulin therapy as a glucose-lowering strategy in type2 diabetes...There are many advantages of combining incretin therapy[glucagon-like peptide-1(GLP-1)receptor agonists and dipeptidyl peptidase-4(DPP-4)inhibitors]with insulin therapy as a glucose-lowering strategy in type2 diabetes.One important advantage is the complementary mode of the mechanistic action of incretin and insulin therapy.Another advantage is the reduction in risk of hypoglycemia and weight gain when adding incretin therapy to insulin.Several clinical trials have studied the addition of GLP-1 receptor agonists[exenatide BID(twice daily),lixisenatide,albiglutide]or DPP-4inhibitors(vildagliptin,sitagliptin,saxagliptin,alogliptin,linagliptin)to ongoing insulin therapy or adding insulin to ongoing therapy with a GLP-1 receptor agonist(liraglutide).These studies show improved glycemia in the presence of limited risk for hypoglycemia and weight gain with the combination of incretin therapy with insulin.This article reviews the background and clinical studies on this combination.展开更多
Objective: To investigate the correlation between lower extremity vascular sclerosis and osteoporosis in elderly men with type 2 diabetes mellitus. Methods: A total of 359 elderly male patients with type II diabetes h...Objective: To investigate the correlation between lower extremity vascular sclerosis and osteoporosis in elderly men with type 2 diabetes mellitus. Methods: A total of 359 elderly male patients with type II diabetes hospitalized in the First Affiliated Hospital of Chongqing Medical University from January 2018 to June 2023 were retrospectively collected. According to the BMD (Bone Density Value), the patients were categorized into osteoporotic (T ≤ -2.5, n = 248) and non-osteoporotic groups (T > -2.5, n = 111). T test and Chi-square test were used to evaluate the differences in clinical data, biochemical markers and ABI between two groups. Multivariate logistic regression was used to analyze the risk factors of osteoporosis in elderly men with type 2 diabetes mellitus. Results: Compared with the non-osteoporotic group, the differences in diabetes course, systolic blood pressure, ABI, BMI, uric acid, triglyceride, and HDL in the osteoporotic group were statistically significant (P < 0.05). Logistic multivariate regression analysis showed that lower extremity vascular sclerosis was an independent risk factor for osteoporosis in elderly men with type 2 diabetes mellitus (P Conclusion: Atherosclerosis of the lower extremities in elderly men with T2DM is closely related to osteoporosis, and can lead to a decrease in bone mass, and an increase in osteoporosis.展开更多
In present paper, we study precisely the growth of analytic functions defined by zero order Laplace-Stieltjes transformation converging in right plane. The coefficient characterizations of generalized logarithmic p-ty...In present paper, we study precisely the growth of analytic functions defined by zero order Laplace-Stieltjes transformation converging in right plane. The coefficient characterizations of generalized logarithmic p-type and generalized lower logarithmic p-type are obtained, which improve the results of logarithmic type and lower logarithmic type.展开更多
The physical properties and group compositions of crude oils in the western depression of the Liaohe Basin possess such characteristics as to increase gradually in density, viscosity and wax contents, and decrease in ...The physical properties and group compositions of crude oils in the western depression of the Liaohe Basin possess such characteristics as to increase gradually in density, viscosity and wax contents, and decrease in saturated hydrocarbon and non-hydrocarbon and bitumen contents from the deep level to the shallow level and from the center of the depression to its boundary. Saturated hydrocarbons have various spectra, such as single peak and double peak patterns, front peak and rear peak patterns, and smooth peak and serated peak patterns, as well as the chromatograms of biodegraded n-alkanes. The ratios of Pr/Ph in crude oils from the southern part of the depression are generally higher than those in the northern part. The distribution of regular steranes C27-C29 is predominantly of the ramp type, and only a few samples have relatively high C28 contents in the southern part of the depression. As viewed from their physical properties and geochemical characteristics, crude oils in the study area can be divided into two types (I and II) based on oil-generating sources and sedimentary environments, and then further divided into three sub-types (Ia, Ib and Ic:IIa, IIb and IIIc, respectively) based on their degrees of maturation and secondary transformation. This will provide the reliable basis for oil-source correlation and petroleum exploration and prediction.展开更多
The objective of this paper is to study the issue of uniformity on asymmetrical designs with two and three mixed levels in terms of Lee discrepancy. Based on the known formulation, we present a new lower bound of Lee ...The objective of this paper is to study the issue of uniformity on asymmetrical designs with two and three mixed levels in terms of Lee discrepancy. Based on the known formulation, we present a new lower bound of Lee discrepancy of fractional factorial designs with two and three mixed levels. Our new lower bound is sharper and more valid than other existing lower bounds in literature, which is a useful complement to the lower bound theory of discrepancies.展开更多
In this study, a sandstone interval of the lower Cretaceous successions in SW Iran is analyzed regarding the effects of late diagenesis on the alteration of primary reservoir quality and pore system. Petrological and ...In this study, a sandstone interval of the lower Cretaceous successions in SW Iran is analyzed regarding the effects of late diagenesis on the alteration of primary reservoir quality and pore system. Petrological and geochemical analyses indicate dominant quartz mineralogy(quartz arenite) deposited in distributary channel and mouth bar environments which is embedded in delta front to prodelta argillaceous sediments. Rather than mineralogy and some remaining primary(intergranular)porosity, several late(burial) diagenetic processes including multi-phase carbonate cementation, chlorite cementation, and chemical compaction, affected the reservoir quality. Most of the diagenetic processes had a decreasing effect on the primary reservoir quality. All recognized diagenetic features are related to burial diagenesis of the surrounding open marine shales(clay mineral transformation) and expelled diagenetic fluids.展开更多
Sedimentary organic matter(OM) is a major reservoir of organic carbon in the global carbon cycle. Despite many studies, there still exist many debates on the mechanism of OM accumulation and preservation in marine sed...Sedimentary organic matter(OM) is a major reservoir of organic carbon in the global carbon cycle. Despite many studies, there still exist many debates on the mechanism of OM accumulation and preservation in marine sediments. We present a new field study of a Lower Cambrian shallow marine shelf sequence in the northern edge of the Yangtze Plate, China. Our results show that palynological OM and biogenic silica(Bio-Si) could be used alongside more conventional redox and paleo-productivity proxies to study the distribution of OM in marine sediments. The qualitative and quantitative study of palynological OM provides more detailed information on the nature of sedimentary organic carbon, which can be helpful in the assessment of primary productivity and OM preservation. In addition, the presence of Bio-Si stimulates the physical preservation of OM. Further analysis indicates that an increase in Bio-Si can promote OM preservation. This case-study provides insight into the intertwined factors controlling OM accumulation in the Early Cambrian.展开更多
Using well logs data only, the evaluation of shale gas hydrocarbon potential of Talhar Shale Member of Lower Goru Formation has been a challenge in Southern Lower Indus Basin in Pakistan. Well logs data analysis is he...Using well logs data only, the evaluation of shale gas hydrocarbon potential of Talhar Shale Member of Lower Goru Formation has been a challenge in Southern Lower Indus Basin in Pakistan. Well logs data analysis is helpful to evaluate the gas potential of source shale rocks. We introduced and applied empirical and graphical method to fulfil this task and derived geochemical parameters from well logs data. The method mentioned is cheap and fast. Talhar Shale has kerogen type Ⅲ and type Ⅱ which are montmorillonite clay and have potential to produce oil and gas. Talhar Shale has better sorption property. Empirical formulas are used to derive parameters, using well logs of porosity, density and uranium. Porosity and volume of kerogen, calculated from density log, give average values of 11.8% and 11.4%. Average value of level of maturity index （LMI） derived from log is 0.54, which indicates that it is at the early stage of maturity. Vitrinite reflectance is between 0.5%-0.55% as calculated by graphical method and empirical formula. Talhar Shale is at onset of oil generation, with main products of oil and gas. It is a good potential source in the study area.展开更多
Two systems of La_(2-x)Sr_xCuO_(4±λ) and La_(2-x)Th_xCuO_(4±λ) mixed oxides with K_2NiF_4structure were synthesized.The compositions and structures of the catalysts were characterized by means of XRD,XPS,c...Two systems of La_(2-x)Sr_xCuO_(4±λ) and La_(2-x)Th_xCuO_(4±λ) mixed oxides with K_2NiF_4structure were synthesized.The compositions and structures of the catalysts were characterized by means of XRD,XPS,chemical analysis and so on.The catalytic behavior for the direct decomposition of NO has been investigated.The results show that the catalytic activity is closely related to the oxygen vacancy and lower valence metallic ion in the direct decomposition of NO.The presence of oxygen vacancy is necessary for mixed oxide to have steady activity in NO decomposition.展开更多
The existence of at feast one solution and the existence of extreme solutions of periodic boundary value problems for first-order integro-differential equations of mixed type are studied, in the presence of generalize...The existence of at feast one solution and the existence of extreme solutions of periodic boundary value problems for first-order integro-differential equations of mixed type are studied, in the presence of generalized upper and laver solutions. The discussion is based an new comparison theorems and coincidence degree and monotone iterative methods.展开更多
For the lower bound about the determinant of Hadamard product of A and B, where A is a n × n real positive definite matrix and B is a n × n M-matrix, Jianzhou Liu [SLAM J. Matrix Anal. Appl., 18(2)(1997): 30...For the lower bound about the determinant of Hadamard product of A and B, where A is a n × n real positive definite matrix and B is a n × n M-matrix, Jianzhou Liu [SLAM J. Matrix Anal. Appl., 18(2)(1997): 305-311]obtained the estimated inequality as follows det(A o B)≥a11b11 nⅡk=2(bkk detAk/detAk-1+detBk/detBk-1(k-1Ei=1 aikaki/aii))=Ln(A,B),where Ak is kth order sequential principal sub-matrix of A. We establish an improved lower bound of the form Yn(A,B)=a11baa nⅡk=2(bkk detAk/detAk-1+akk detBk/detBk-1-detAdetBk/detak-1detBk-1)≥Ln(A,B).For more weaker and practical lower bound, Liu given thatdet(A o B)≥(nⅡi=1 bii)detA+(nⅡi=1 aii)detB(nⅡk=2 k-1Ei=1 aikaki/aiiakk)=(L)n(A,B).We further improve it as Yn(A,B)=(nⅡi=1 bii)detA+(nⅡi=1 aii)detB-(detA)(detB)+max1≤k≤n wn(A,B,k)≥(nⅡi=1 bii)detA+(nⅡi=1 aii)detB-(detA)(detB)≥(L)n(A,B).展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51705465,51525504)Young Researchers Foundation of Zhejiang Provincial Top Key Academic Discipline of Mechanical Engineering of Zhejiang Sci-tech University(Grant No.ZSTUME02B02)
文摘Type synthesis of mechanisms aims to systematically determine all possible structures for a specific mobility requirement. Numerous methods based on di erent theories were proposed for type synthesis of lower mobility parallel mechanisms in past decades. However, there does not exist a comprehensive review on these approaches. Therefore, the goal of this paper is to give such a review, classifying the approaches proposed in the literature into three groups, namely, motion-based methods, constraint-based methods, and other methods. The motion-based methods include the Lie group based method, the GF set method, the linear transformation method, the POC set method,and the finite screw method. The constraint-based methods involve the screw theory-based method, the virtual chain method, the method based on Grassmann line geometry and line graphs, and the motion constraint generator method. Other methods contain the enumeration approach based on the general CGK mobility formula and the graph theory method. Upon thoroughly analyzing the characteristics and/or limitations of each method, this review provides a well reference to help researchers find an e ective synthesis method for innovative design and further scientific investigations for mechanisms.
基金Foundation item： Supported by the NNSF of China（11201395） Supported by the Science Foundation of Educational Commission of Hubei Province（Q20132801）
文摘The main purpose of this paper is to study the lower order and type of second order differential equation w"(z)-A(z)w=0,where A(z)is a polynomial.In the case of A(z)=a_dz^d,the authors prove that the lower order and the type of all non-trivial solutions w of w"(z)-A(z)w=0 are equal to(d+2)/2 and(2(|a_d|)^(1/2))/(d+2)respectively.In the case of A(z)=a_dz^d+a_(d-1)z^(d-1)+…a_1z+a_0,a_d>0,a_(d-1)>0,…,a_1≥0,a_0≥0,the authors prove that the lower order of all non-trivial solutions w of w"(z)-A(z)w=0 is(d+2)/2.
文摘There are many advantages of combining incretin therapy[glucagon-like peptide-1(GLP-1)receptor agonists and dipeptidyl peptidase-4(DPP-4)inhibitors]with insulin therapy as a glucose-lowering strategy in type2 diabetes.One important advantage is the complementary mode of the mechanistic action of incretin and insulin therapy.Another advantage is the reduction in risk of hypoglycemia and weight gain when adding incretin therapy to insulin.Several clinical trials have studied the addition of GLP-1 receptor agonists[exenatide BID(twice daily),lixisenatide,albiglutide]or DPP-4inhibitors(vildagliptin,sitagliptin,saxagliptin,alogliptin,linagliptin)to ongoing insulin therapy or adding insulin to ongoing therapy with a GLP-1 receptor agonist(liraglutide).These studies show improved glycemia in the presence of limited risk for hypoglycemia and weight gain with the combination of incretin therapy with insulin.This article reviews the background and clinical studies on this combination.
文摘Objective: To investigate the correlation between lower extremity vascular sclerosis and osteoporosis in elderly men with type 2 diabetes mellitus. Methods: A total of 359 elderly male patients with type II diabetes hospitalized in the First Affiliated Hospital of Chongqing Medical University from January 2018 to June 2023 were retrospectively collected. According to the BMD (Bone Density Value), the patients were categorized into osteoporotic (T ≤ -2.5, n = 248) and non-osteoporotic groups (T > -2.5, n = 111). T test and Chi-square test were used to evaluate the differences in clinical data, biochemical markers and ABI between two groups. Multivariate logistic regression was used to analyze the risk factors of osteoporosis in elderly men with type 2 diabetes mellitus. Results: Compared with the non-osteoporotic group, the differences in diabetes course, systolic blood pressure, ABI, BMI, uric acid, triglyceride, and HDL in the osteoporotic group were statistically significant (P < 0.05). Logistic multivariate regression analysis showed that lower extremity vascular sclerosis was an independent risk factor for osteoporosis in elderly men with type 2 diabetes mellitus (P Conclusion: Atherosclerosis of the lower extremities in elderly men with T2DM is closely related to osteoporosis, and can lead to a decrease in bone mass, and an increase in osteoporosis.
基金Supported by the Technology Project of Jiangxi Provincial Education Department(Grant No.GJJ13788)
文摘In present paper, we study precisely the growth of analytic functions defined by zero order Laplace-Stieltjes transformation converging in right plane. The coefficient characterizations of generalized logarithmic p-type and generalized lower logarithmic p-type are obtained, which improve the results of logarithmic type and lower logarithmic type.
文摘The physical properties and group compositions of crude oils in the western depression of the Liaohe Basin possess such characteristics as to increase gradually in density, viscosity and wax contents, and decrease in saturated hydrocarbon and non-hydrocarbon and bitumen contents from the deep level to the shallow level and from the center of the depression to its boundary. Saturated hydrocarbons have various spectra, such as single peak and double peak patterns, front peak and rear peak patterns, and smooth peak and serated peak patterns, as well as the chromatograms of biodegraded n-alkanes. The ratios of Pr/Ph in crude oils from the southern part of the depression are generally higher than those in the northern part. The distribution of regular steranes C27-C29 is predominantly of the ramp type, and only a few samples have relatively high C28 contents in the southern part of the depression. As viewed from their physical properties and geochemical characteristics, crude oils in the study area can be divided into two types (I and II) based on oil-generating sources and sedimentary environments, and then further divided into three sub-types (Ia, Ib and Ic:IIa, IIb and IIIc, respectively) based on their degrees of maturation and secondary transformation. This will provide the reliable basis for oil-source correlation and petroleum exploration and prediction.
基金supported by the National Natural Science Foundation of China(11301546).supported by the National Natural Science Foundation of China(11271147,11471136)
文摘The objective of this paper is to study the issue of uniformity on asymmetrical designs with two and three mixed levels in terms of Lee discrepancy. Based on the known formulation, we present a new lower bound of Lee discrepancy of fractional factorial designs with two and three mixed levels. Our new lower bound is sharper and more valid than other existing lower bounds in literature, which is a useful complement to the lower bound theory of discrepancies.
基金The NIOC is thanked for data preparation and sponsorship
文摘In this study, a sandstone interval of the lower Cretaceous successions in SW Iran is analyzed regarding the effects of late diagenesis on the alteration of primary reservoir quality and pore system. Petrological and geochemical analyses indicate dominant quartz mineralogy(quartz arenite) deposited in distributary channel and mouth bar environments which is embedded in delta front to prodelta argillaceous sediments. Rather than mineralogy and some remaining primary(intergranular)porosity, several late(burial) diagenetic processes including multi-phase carbonate cementation, chlorite cementation, and chemical compaction, affected the reservoir quality. Most of the diagenetic processes had a decreasing effect on the primary reservoir quality. All recognized diagenetic features are related to burial diagenesis of the surrounding open marine shales(clay mineral transformation) and expelled diagenetic fluids.
基金supported by the National Natural Science Foundation of China(No.41430101)the State Special Fund from Ministry of Science and Technology(No.2017ZX05036002)
文摘Sedimentary organic matter(OM) is a major reservoir of organic carbon in the global carbon cycle. Despite many studies, there still exist many debates on the mechanism of OM accumulation and preservation in marine sediments. We present a new field study of a Lower Cambrian shallow marine shelf sequence in the northern edge of the Yangtze Plate, China. Our results show that palynological OM and biogenic silica(Bio-Si) could be used alongside more conventional redox and paleo-productivity proxies to study the distribution of OM in marine sediments. The qualitative and quantitative study of palynological OM provides more detailed information on the nature of sedimentary organic carbon, which can be helpful in the assessment of primary productivity and OM preservation. In addition, the presence of Bio-Si stimulates the physical preservation of OM. Further analysis indicates that an increase in Bio-Si can promote OM preservation. This case-study provides insight into the intertwined factors controlling OM accumulation in the Early Cambrian.
文摘Using well logs data only, the evaluation of shale gas hydrocarbon potential of Talhar Shale Member of Lower Goru Formation has been a challenge in Southern Lower Indus Basin in Pakistan. Well logs data analysis is helpful to evaluate the gas potential of source shale rocks. We introduced and applied empirical and graphical method to fulfil this task and derived geochemical parameters from well logs data. The method mentioned is cheap and fast. Talhar Shale has kerogen type Ⅲ and type Ⅱ which are montmorillonite clay and have potential to produce oil and gas. Talhar Shale has better sorption property. Empirical formulas are used to derive parameters, using well logs of porosity, density and uranium. Porosity and volume of kerogen, calculated from density log, give average values of 11.8% and 11.4%. Average value of level of maturity index （LMI） derived from log is 0.54, which indicates that it is at the early stage of maturity. Vitrinite reflectance is between 0.5%-0.55% as calculated by graphical method and empirical formula. Talhar Shale is at onset of oil generation, with main products of oil and gas. It is a good potential source in the study area.
文摘Two systems of La_(2-x)Sr_xCuO_(4±λ) and La_(2-x)Th_xCuO_(4±λ) mixed oxides with K_2NiF_4structure were synthesized.The compositions and structures of the catalysts were characterized by means of XRD,XPS,chemical analysis and so on.The catalytic behavior for the direct decomposition of NO has been investigated.The results show that the catalytic activity is closely related to the oxygen vacancy and lower valence metallic ion in the direct decomposition of NO.The presence of oxygen vacancy is necessary for mixed oxide to have steady activity in NO decomposition.
文摘The existence of at feast one solution and the existence of extreme solutions of periodic boundary value problems for first-order integro-differential equations of mixed type are studied, in the presence of generalized upper and laver solutions. The discussion is based an new comparison theorems and coincidence degree and monotone iterative methods.
文摘For the lower bound about the determinant of Hadamard product of A and B, where A is a n × n real positive definite matrix and B is a n × n M-matrix, Jianzhou Liu [SLAM J. Matrix Anal. Appl., 18(2)(1997): 305-311]obtained the estimated inequality as follows det(A o B)≥a11b11 nⅡk=2(bkk detAk/detAk-1+detBk/detBk-1(k-1Ei=1 aikaki/aii))=Ln(A,B),where Ak is kth order sequential principal sub-matrix of A. We establish an improved lower bound of the form Yn(A,B)=a11baa nⅡk=2(bkk detAk/detAk-1+akk detBk/detBk-1-detAdetBk/detak-1detBk-1)≥Ln(A,B).For more weaker and practical lower bound, Liu given thatdet(A o B)≥(nⅡi=1 bii)detA+(nⅡi=1 aii)detB(nⅡk=2 k-1Ei=1 aikaki/aiiakk)=(L)n(A,B).We further improve it as Yn(A,B)=(nⅡi=1 bii)detA+(nⅡi=1 aii)detB-(detA)(detB)+max1≤k≤n wn(A,B,k)≥(nⅡi=1 bii)detA+(nⅡi=1 aii)detB-(detA)(detB)≥(L)n(A,B).
