Coupling is the significant characteristic of parallel mechanism,while it is just the coupling that brings about much difficulty for the configuration design,theoretical analysis and the development of the control sys...Coupling is the significant characteristic of parallel mechanism,while it is just the coupling that brings about much difficulty for the configuration design,theoretical analysis and the development of the control system of the parallel mechanism. And recently,the research on the decoupled parallel mechanism becomes one of the research hot points in the mechanism fields. In this paper,a type synthesis method for the translational decoupled parallel mechanism( TDPM) is proposed based on the screw theory. To achieve the decoupling characteristics of the translational parallel mechanism,the translational decoupled criterion for type synthesis of the branches are presented in this paper. According to this criterion and the realization conditions of rotational degree of freedom of the mechanism proposed former,a large number of branches for the TDPM are obtained. Taking the three degrees of freedom( DOFs) TDPM as an example,the process of type synthesis is discussed in detail. Using this proposed type synthesis method,a serial of translational decoupled parallel mechanisms, including but not limited to all the existing typical 3-DOF TDPMs, are obtained, which identifies the correctness and effective of the method. The contents of this paper provide a reference and possess significant theoretical meanings for the synthesis and development of the novel decoupled parallel mechanisms.展开更多
Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains （GRV）, Antarctica, were presented and their. Weathering effect, shock metamorphism and type distribution patterns were discu...Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains （GRV）, Antarctica, were presented and their. Weathering effect, shock metamorphism and type distribution patterns were discussed in this study. Among them, six are unequilibrated ordinary chondrites, including 3 H3 and 3 L3 ; and 92 meteorites are equilibrated ordinary chondrites, including 24 H-group （ 13 H4, 10 H5, 1 H6）, 64 L-group （2 L4, 44 L5, 18 L6） and 4 LL-group （3 LL4, 1 LL5）. Most GRV ehondrites （ 〉 90% ） displayed minor weathering effect （ W1 and W2）. About half of the meteorites experienced severe shock metamorphism. They commonly contain shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals. In addition, the Grove Mountains collection seems to have more abundant unequilibrated and L group ordinary ehondrites compared to the US Antarctic meteorite collection which were mainly found along the Transantarctic Mountains.展开更多
Objectives: To explore the treatment and related prognosis of elderly patients with Anderson II odontoid fracture with posterior pedicle screw fixation combined with iliac bone grafting. Methods: Retrospective analysi...Objectives: To explore the treatment and related prognosis of elderly patients with Anderson II odontoid fracture with posterior pedicle screw fixation combined with iliac bone grafting. Methods: Retrospective analysis of 17 cases of elderly patients with Anderson II odontoid fracture who underwent posterior pedicle screw fixation combined with iliac bone grafting from January 2013 to December 2016. 17 patients had a history of trauma before surgery, and they all have varying degrees of atlantoaxial instability or subluxation and varying degrees of neck occipital pain and limited mobility. Result: No spinal cord or vertebral artery injury occurred during surgery. Follow-up information is complete. The follow-up period was 6 to 48 months (mean 27.4 ± 12.4 months). Postoperative imaging review prompted a good reduction of cervical spine, stable sequence;no pedicle screw loosening, fracture, iliac bone graft at the location of the situation, odontoid fracture and bone healing at the good, the patient after cervical rotation are limited to varying degrees. Conclusion: Posterior pedicle screw fixation combined with iliac bone grafting in elderly patients with Anderson II odontoid fracture can achieve good stability, and the prognosis is good, but long-term cervical rotation function may be affected to varying degrees.展开更多
BACKGROUND Neurofibromatosis type 1(NF-1)is a common autosomal dominant genetic disorder.It is characterized by café-au-lait spots and cutaneous neurofibromas.Although NF-1 typically involves the skin,nerves,bone...BACKGROUND Neurofibromatosis type 1(NF-1)is a common autosomal dominant genetic disorder.It is characterized by café-au-lait spots and cutaneous neurofibromas.Although NF-1 typically involves the skin,nerves,bones,and eyes,vascular manifestation in the form of devastating hemorrhage can occur rarely.CASE SUMMARY We present the case of a 47-year-old female with NF-1 who had a ruptured right lower limb arterial malformation.She presented with sudden right lower limb swelling for two hours and symptoms of hemorrhagic shock on admission.The physical examination revealed a right lower limb presenting as elephantiasis and visible dark-brown pigmentation over a large area.Computed tomography angiography showed right lower limb arteriovenous malformation.Therefore,the patient underwent emergency right lower limb digital subtraction angiography(DSA)and vascular embolization after blood transfusions.However,after DSA,vascular embolization,and repeated blood transfusions,the anemia and right lower limb swelling and tenderness did not improve.As a result,the patient underwent right lower extremity above-knee amputation.After amputation,the patient's hemoglobin level improved significantly without blood transfusion,and she was discharged from the hospital after the incision healed.Postoperative pathological examination suggested neurogenic tumors.No other complications had occurred 1-year follow-up.CONCLUSION Vascular malformation and rupture are fatal complications of NF-1.Embolization may not provide complete relief,the patient might need to undergo neurofibroma resection or amputation.展开更多
We are concerned with global solutions of multidimensional(M-D)Riemann problems for nonlinear hyperbolic systems of conservation laws,focusing on their global configurations and structures.We present some recent devel...We are concerned with global solutions of multidimensional(M-D)Riemann problems for nonlinear hyperbolic systems of conservation laws,focusing on their global configurations and structures.We present some recent developments in the rigorous analysis of two-dimensional(2-D)Riemann problems involving transonic shock waves through several prototypes of hyperbolic systems of conservation laws and discuss some further M-D Riemann problems and related problems for nonlinear partial differential equations.In particular,we present four different 2-D Riemann problems through these prototypes of hyperbolic systems and show how these Riemann problems can be reformulated/solved as free boundary problems with transonic shock waves as free boundaries for the corresponding nonlinear conservation laws of mixed elliptic-hyperbolic type and related nonlinear partial differential equations.展开更多
Objectives To assess the prognostic value of B-type natriuretic peptide （BNP） in severe AMI patients treated with intra-aortic ballon counterpulsation（IABP）. Methods A total of 42 AMI patients with cardiogenic sho...Objectives To assess the prognostic value of B-type natriuretic peptide （BNP） in severe AMI patients treated with intra-aortic ballon counterpulsation（IABP）. Methods A total of 42 AMI patients with cardiogenic shock were retrospectively studied. BNP plasma level was recorded in the 24th hour and 4th day after myocardial infarction. The different mortality were compared among patients with different BNP levels. Results With aggressive treatment, 20 patients survived short term hospitalization. Plasma concentration of BNP in dying patients is much higher than in survivals（1369 ± 353 vs 651 ± 302 pg/ml. P〈 0.01）.Patients with BNP higher than 1474 pg/mL had a mortality of 92.9 %. Conclusions Elevated BNP level in AMI patients with cardiogenic shock treated with IABP is highly associated with poor prognosis.展开更多
经过40余年临床应用与不断发展,引导骨组织再生术(guided bone regeneration,GBR)已被证明是一种可靠的牙槽骨骨增量技术。GBR技术在应用过程中的核心要素是充足的血供和稳定的环境。但现有GBR技术都是在“以血供为核心”的理论体系下...经过40余年临床应用与不断发展,引导骨组织再生术(guided bone regeneration,GBR)已被证明是一种可靠的牙槽骨骨增量技术。GBR技术在应用过程中的核心要素是充足的血供和稳定的环境。但现有GBR技术都是在“以血供为核心”的理论体系下进行的,缺乏对稳定要素重要性的重视。我们通过文献阅读及系列临床试验,提出“以稳定为核心”的牙槽骨修复重建理念。基于新理念,创建了以单纯人工骨粉修复牙槽骨重度缺损的治疗新术式,革新了国际上必须用自体骨修复骨缺损的治疗理念。本文将从GBR技术的历史发展轨迹中寻找稳定的重要性,结合现有骨再生理论,详细阐述“以稳定为核心”的牙槽骨修复重建治疗新技术。展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.51005195,51205339)
文摘Coupling is the significant characteristic of parallel mechanism,while it is just the coupling that brings about much difficulty for the configuration design,theoretical analysis and the development of the control system of the parallel mechanism. And recently,the research on the decoupled parallel mechanism becomes one of the research hot points in the mechanism fields. In this paper,a type synthesis method for the translational decoupled parallel mechanism( TDPM) is proposed based on the screw theory. To achieve the decoupling characteristics of the translational parallel mechanism,the translational decoupled criterion for type synthesis of the branches are presented in this paper. According to this criterion and the realization conditions of rotational degree of freedom of the mechanism proposed former,a large number of branches for the TDPM are obtained. Taking the three degrees of freedom( DOFs) TDPM as an example,the process of type synthesis is discussed in detail. Using this proposed type synthesis method,a serial of translational decoupled parallel mechanisms, including but not limited to all the existing typical 3-DOF TDPMs, are obtained, which identifies the correctness and effective of the method. The contents of this paper provide a reference and possess significant theoretical meanings for the synthesis and development of the novel decoupled parallel mechanisms.
基金supported by the Doctor's Foundation of Hunan University of Science and Technology(Grant No.E50806)
文摘Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains （GRV）, Antarctica, were presented and their. Weathering effect, shock metamorphism and type distribution patterns were discussed in this study. Among them, six are unequilibrated ordinary chondrites, including 3 H3 and 3 L3 ; and 92 meteorites are equilibrated ordinary chondrites, including 24 H-group （ 13 H4, 10 H5, 1 H6）, 64 L-group （2 L4, 44 L5, 18 L6） and 4 LL-group （3 LL4, 1 LL5）. Most GRV ehondrites （ 〉 90% ） displayed minor weathering effect （ W1 and W2）. About half of the meteorites experienced severe shock metamorphism. They commonly contain shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals. In addition, the Grove Mountains collection seems to have more abundant unequilibrated and L group ordinary ehondrites compared to the US Antarctic meteorite collection which were mainly found along the Transantarctic Mountains.
文摘Objectives: To explore the treatment and related prognosis of elderly patients with Anderson II odontoid fracture with posterior pedicle screw fixation combined with iliac bone grafting. Methods: Retrospective analysis of 17 cases of elderly patients with Anderson II odontoid fracture who underwent posterior pedicle screw fixation combined with iliac bone grafting from January 2013 to December 2016. 17 patients had a history of trauma before surgery, and they all have varying degrees of atlantoaxial instability or subluxation and varying degrees of neck occipital pain and limited mobility. Result: No spinal cord or vertebral artery injury occurred during surgery. Follow-up information is complete. The follow-up period was 6 to 48 months (mean 27.4 ± 12.4 months). Postoperative imaging review prompted a good reduction of cervical spine, stable sequence;no pedicle screw loosening, fracture, iliac bone graft at the location of the situation, odontoid fracture and bone healing at the good, the patient after cervical rotation are limited to varying degrees. Conclusion: Posterior pedicle screw fixation combined with iliac bone grafting in elderly patients with Anderson II odontoid fracture can achieve good stability, and the prognosis is good, but long-term cervical rotation function may be affected to varying degrees.
文摘BACKGROUND Neurofibromatosis type 1(NF-1)is a common autosomal dominant genetic disorder.It is characterized by café-au-lait spots and cutaneous neurofibromas.Although NF-1 typically involves the skin,nerves,bones,and eyes,vascular manifestation in the form of devastating hemorrhage can occur rarely.CASE SUMMARY We present the case of a 47-year-old female with NF-1 who had a ruptured right lower limb arterial malformation.She presented with sudden right lower limb swelling for two hours and symptoms of hemorrhagic shock on admission.The physical examination revealed a right lower limb presenting as elephantiasis and visible dark-brown pigmentation over a large area.Computed tomography angiography showed right lower limb arteriovenous malformation.Therefore,the patient underwent emergency right lower limb digital subtraction angiography(DSA)and vascular embolization after blood transfusions.However,after DSA,vascular embolization,and repeated blood transfusions,the anemia and right lower limb swelling and tenderness did not improve.As a result,the patient underwent right lower extremity above-knee amputation.After amputation,the patient's hemoglobin level improved significantly without blood transfusion,and she was discharged from the hospital after the incision healed.Postoperative pathological examination suggested neurogenic tumors.No other complications had occurred 1-year follow-up.CONCLUSION Vascular malformation and rupture are fatal complications of NF-1.Embolization may not provide complete relief,the patient might need to undergo neurofibroma resection or amputation.
基金The research of Gui-Qiang G.Chen was supported in part by the UK Engineering and Physical Sciences Research Council Awards EP/L015811/1,EP/V008854/1,EP/V051121/1the Royal Society-Wolfson Research Merit Award WM090014.
文摘We are concerned with global solutions of multidimensional(M-D)Riemann problems for nonlinear hyperbolic systems of conservation laws,focusing on their global configurations and structures.We present some recent developments in the rigorous analysis of two-dimensional(2-D)Riemann problems involving transonic shock waves through several prototypes of hyperbolic systems of conservation laws and discuss some further M-D Riemann problems and related problems for nonlinear partial differential equations.In particular,we present four different 2-D Riemann problems through these prototypes of hyperbolic systems and show how these Riemann problems can be reformulated/solved as free boundary problems with transonic shock waves as free boundaries for the corresponding nonlinear conservation laws of mixed elliptic-hyperbolic type and related nonlinear partial differential equations.
文摘Objectives To assess the prognostic value of B-type natriuretic peptide （BNP） in severe AMI patients treated with intra-aortic ballon counterpulsation（IABP）. Methods A total of 42 AMI patients with cardiogenic shock were retrospectively studied. BNP plasma level was recorded in the 24th hour and 4th day after myocardial infarction. The different mortality were compared among patients with different BNP levels. Results With aggressive treatment, 20 patients survived short term hospitalization. Plasma concentration of BNP in dying patients is much higher than in survivals（1369 ± 353 vs 651 ± 302 pg/ml. P〈 0.01）.Patients with BNP higher than 1474 pg/mL had a mortality of 92.9 %. Conclusions Elevated BNP level in AMI patients with cardiogenic shock treated with IABP is highly associated with poor prognosis.
文摘经过40余年临床应用与不断发展,引导骨组织再生术(guided bone regeneration,GBR)已被证明是一种可靠的牙槽骨骨增量技术。GBR技术在应用过程中的核心要素是充足的血供和稳定的环境。但现有GBR技术都是在“以血供为核心”的理论体系下进行的,缺乏对稳定要素重要性的重视。我们通过文献阅读及系列临床试验,提出“以稳定为核心”的牙槽骨修复重建理念。基于新理念,创建了以单纯人工骨粉修复牙槽骨重度缺损的治疗新术式,革新了国际上必须用自体骨修复骨缺损的治疗理念。本文将从GBR技术的历史发展轨迹中寻找稳定的重要性,结合现有骨再生理论,详细阐述“以稳定为核心”的牙槽骨修复重建治疗新技术。
