The aims of the study were to investigate the incidence of C-shaped root canal systems in mandibular second molars in a native Chinese population using radiography and clinical examination under microscope and to comp...The aims of the study were to investigate the incidence of C-shaped root canal systems in mandibular second molars in a native Chinese population using radiography and clinical examination under microscope and to compare the relative efficacies of these methods. For the recognition of C-shaped root canal system, 1 146 mandibular second molars were selected and examined. Teeth with C-shaped canal systems were categorized by using the radiographic classification criteria and the modified Melton＇s method. C-shaped canals were identified in 397 （34.64%） mandibular second molars by radiography （type I, 31.23%; type II, 38.29%; type III, 30.48%）. Clinical examination showed that 449 （39.18%） cases exhibited C-shaped canal systems （C1, 22.94%; C2, 48.11%; C3a, 15.59%; C3b, 13.36%）. As for the result of the radiographic and clinical combined examination, C-shaped root canals were found in 473 （41.27%） mandibular second molars （C1, 21.78%; C2, 45.67%; C3a, 16.70%; C3b, 15.86%）. The incidence of C-shaped root canal diagnosed by radiographic method was statistically different from that by clinical examination and the combined examination （P〈O.05）. The study indicated a high incidence of C-shaped canal system in a Chinese population. The combination of microscopic and radiographic examination is an effective method in identifying the C-shaped root canal system.展开更多
In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the ...In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the dynamic equation, the in-bore motion characteristics of the armature are obtained. The distribution of current in the rail and armature is analyzed based on the magnetic diffusion equation and Ampere’s law. On this basis, three simulation models are proposed, which correspond to static state,motion state and motion state considering the velocity skin effect. The magnetic field of the investigated points along the central axes of the armature front end are obtained. The results show that, in static state,the peak magnetic flux density of each investigated point is greater than the other two states. Velocity skin effect leads to a decrease in peak magnetic flux density. The change of motion state has little influence on the peak magnetic flux density of the investigated point that far away from the armature. The calculated results can be used in the electromagnetic shielding design of intelligent ammunition.展开更多
Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with t...Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with triple bandnotched characteristics is presented. The proposed antenna consists of a square patch with four truncated corners and a partial ground plane with a rectangular slit. The operation bandwidth of the designed antenna is from 2.66 GHz to more than 13.5 GHz. Band-notched characteristics of antenna to reject the frequency band of 3.18 - 3.59 GHz and 4.70 - 5.88 GHz, is realized by inserting two C-shaped slots in the patch, the third band of 9.54 - 12.22 GHz is achieved by slottype capacitively-loaded loop (CLL) inserted in the patch near the feed line. Details of the proposed antenna design and simulated results are presented and discussed.展开更多
To evaluate the retention properties of the novel ‘C＇-shaped molar bands at a laboratory level. Resin-modified glass ionomer cement（RMGIC） was used as a luting agent for the novel C-shaped molar band. The mechanic...To evaluate the retention properties of the novel ‘C＇-shaped molar bands at a laboratory level. Resin-modified glass ionomer cement（RMGIC） was used as a luting agent for the novel C-shaped molar band. The mechanical properties of the band were examined and the retention performance was characterized in the mesial, distal and vertical directions. A clinical trial was conducted using a spilt-mouth design on 50 patients. The novel C-shaped molar bands fit most molars without a repeated try-in process.The use of both nanoHA coating and RMGIC enhanced the tensile（8.00 ± 1.8 MPa） and shear strengths（27.17 ± 8.6 MPa） of the molar bands, leading to high retention in vertical, mesial and distal directions（ p 〈 0.001）. In clinical trials, the C-shaped molar bands had a failure rate（15%） comparable to that of traditional bands, and 93% of the failed bands demonstrated an adhesive remnant index score of 0, corroborating the observation that no luting agent residue remained on the tooth surface in most cases. The novel C-shaped molar bands appear to be a promising appliance that requires further clinical investigations, and may be used effectively in orthodontics.展开更多
四川盆地震旦系灯影组是重要的油气勘探开发层系,复杂的成岩演化和多期流体活动导致多种类型的白云岩形成。揭示震旦系白云岩的形成时代和成因不仅可以为四川盆地震旦系下一步的油气勘探提供更加充实的科学依据,也可为理解全球大规模存...四川盆地震旦系灯影组是重要的油气勘探开发层系,复杂的成岩演化和多期流体活动导致多种类型的白云岩形成。揭示震旦系白云岩的形成时代和成因不仅可以为四川盆地震旦系下一步的油气勘探提供更加充实的科学依据,也可为理解全球大规模存在前寒武纪白云岩的原因提供有益启示。本文针对川中地区震旦系灯影组“葡萄花边”白云岩的形成时代和成因进行了综合研究。岩相学研究表明,“葡萄花边”白云岩充填于藻白云岩的孔隙内,向内对称生长,结晶程度明显好于藻白云岩。在岩相学的基础上,利用激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)微区原位U-Pb定年确定其形成时代,研究结果表明:川中地区震旦系灯影组“葡萄花边”白云岩形成时代为530±12Ma~502±12Ma,略新于灯影组地层年代。结合微量元素分析以及碳-氧-锶同位素数据,对川中地区震旦系灯影组“葡萄花边”白云岩进行成因分析。结果表明,其稀土元素总量(∑REE)相对较低(0.680×10^(-6)~8.963×10^(-6)),δ13 C VPDB(-0.1‰~1.7‰)略低于与同时期海水沉积白云岩的碳同位素值,δ18 O VPDB(-2.3‰~1.4‰)略高于与同时期海水达到氧同位素平衡的白云岩氧同位素值,87 Sr/86 Sr值(0.70876~0.70909)基本落入同时期海水范围。稀土元素配分总体为水平的模式,所有样品表现出Ce负异常。表明其形成环境既非海水沉积环境,也不完全是表生大气水岩溶条件。综合上述特征,推断川中地区震旦系灯影组“葡萄花边”白云岩是在震旦纪末-寒武纪早期海平面高频低幅度波动这一背景下,灯影组地层多次暴露与淹没,形成岩溶裂缝和孔洞的同时在溶蚀空间内结晶形成。残留孔洞为其后流体活动、油气充注提供了储集空间。本研究为认识川中地区震旦系灯影组“葡萄花边”白云岩成因、震旦纪末-寒武纪早期水化学条件、及超深层油气勘探开发提供了有益参考。展开更多
本文提出了一种高精度的二阶无源噪声整形逐次逼近型模数转换器(NS SAR ADC)。首先,采用了一种通过动态浮动反向放大器(FIA)实现kT/C噪声消除的技术,随后结合差分结构的定制电容,实现更小的电容阵列面积的同时抑制了采样热噪声。最后,...本文提出了一种高精度的二阶无源噪声整形逐次逼近型模数转换器(NS SAR ADC)。首先,采用了一种通过动态浮动反向放大器(FIA)实现kT/C噪声消除的技术,随后结合差分结构的定制电容,实现更小的电容阵列面积的同时抑制了采样热噪声。最后,采用翻转电压跟随器(FVF)结构作为动态缓冲器提取残差电压,并通过电容堆叠的操作实现无源求和,对比较器噪声与量化噪声进行了二阶整形。该设计采用0.18μm工艺实现,仿真表明,在1.8 V电源电压、8倍过采样率和2 MS/s的采样频率下,信号噪声失真比(SNDR)为88.57 dB,无杂散动态范围(SFDR)为99.09 dB,功耗仅为302μW。展开更多
基金supported by the grant from the Independent Innovation Foundation of Shandong University of China (No. 2011JC019)the grant of Science and Technique Development Foundation of Shandong province(2010G0020230)
文摘The aims of the study were to investigate the incidence of C-shaped root canal systems in mandibular second molars in a native Chinese population using radiography and clinical examination under microscope and to compare the relative efficacies of these methods. For the recognition of C-shaped root canal system, 1 146 mandibular second molars were selected and examined. Teeth with C-shaped canal systems were categorized by using the radiographic classification criteria and the modified Melton＇s method. C-shaped canals were identified in 397 （34.64%） mandibular second molars by radiography （type I, 31.23%; type II, 38.29%; type III, 30.48%）. Clinical examination showed that 449 （39.18%） cases exhibited C-shaped canal systems （C1, 22.94%; C2, 48.11%; C3a, 15.59%; C3b, 13.36%）. As for the result of the radiographic and clinical combined examination, C-shaped root canals were found in 473 （41.27%） mandibular second molars （C1, 21.78%; C2, 45.67%; C3a, 16.70%; C3b, 15.86%）. The incidence of C-shaped root canal diagnosed by radiographic method was statistically different from that by clinical examination and the combined examination （P〈O.05）. The study indicated a high incidence of C-shaped canal system in a Chinese population. The combination of microscopic and radiographic examination is an effective method in identifying the C-shaped root canal system.
基金supported by the Key Basic Research Projects of Basic Strengthening Plan under Grants 2017-JCJQ-ZD-004
文摘In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the dynamic equation, the in-bore motion characteristics of the armature are obtained. The distribution of current in the rail and armature is analyzed based on the magnetic diffusion equation and Ampere’s law. On this basis, three simulation models are proposed, which correspond to static state,motion state and motion state considering the velocity skin effect. The magnetic field of the investigated points along the central axes of the armature front end are obtained. The results show that, in static state,the peak magnetic flux density of each investigated point is greater than the other two states. Velocity skin effect leads to a decrease in peak magnetic flux density. The change of motion state has little influence on the peak magnetic flux density of the investigated point that far away from the armature. The calculated results can be used in the electromagnetic shielding design of intelligent ammunition.
文摘Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with triple bandnotched characteristics is presented. The proposed antenna consists of a square patch with four truncated corners and a partial ground plane with a rectangular slit. The operation bandwidth of the designed antenna is from 2.66 GHz to more than 13.5 GHz. Band-notched characteristics of antenna to reject the frequency band of 3.18 - 3.59 GHz and 4.70 - 5.88 GHz, is realized by inserting two C-shaped slots in the patch, the third band of 9.54 - 12.22 GHz is achieved by slottype capacitively-loaded loop (CLL) inserted in the patch near the feed line. Details of the proposed antenna design and simulated results are presented and discussed.
基金Funded by Department of Education,National Natural Science Foundation of China(No.81170960)Heilongjiang Province(No.11531204)+1 种基金Department of Health,Heilongjiang Province(No.2006-123)Youth Foundation of the Second Affiliated Hospital of Harbin Medical University(No.QN2006-13)
文摘To evaluate the retention properties of the novel ‘C＇-shaped molar bands at a laboratory level. Resin-modified glass ionomer cement（RMGIC） was used as a luting agent for the novel C-shaped molar band. The mechanical properties of the band were examined and the retention performance was characterized in the mesial, distal and vertical directions. A clinical trial was conducted using a spilt-mouth design on 50 patients. The novel C-shaped molar bands fit most molars without a repeated try-in process.The use of both nanoHA coating and RMGIC enhanced the tensile（8.00 ± 1.8 MPa） and shear strengths（27.17 ± 8.6 MPa） of the molar bands, leading to high retention in vertical, mesial and distal directions（ p 〈 0.001）. In clinical trials, the C-shaped molar bands had a failure rate（15%） comparable to that of traditional bands, and 93% of the failed bands demonstrated an adhesive remnant index score of 0, corroborating the observation that no luting agent residue remained on the tooth surface in most cases. The novel C-shaped molar bands appear to be a promising appliance that requires further clinical investigations, and may be used effectively in orthodontics.
文摘四川盆地震旦系灯影组是重要的油气勘探开发层系,复杂的成岩演化和多期流体活动导致多种类型的白云岩形成。揭示震旦系白云岩的形成时代和成因不仅可以为四川盆地震旦系下一步的油气勘探提供更加充实的科学依据,也可为理解全球大规模存在前寒武纪白云岩的原因提供有益启示。本文针对川中地区震旦系灯影组“葡萄花边”白云岩的形成时代和成因进行了综合研究。岩相学研究表明,“葡萄花边”白云岩充填于藻白云岩的孔隙内,向内对称生长,结晶程度明显好于藻白云岩。在岩相学的基础上,利用激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)微区原位U-Pb定年确定其形成时代,研究结果表明:川中地区震旦系灯影组“葡萄花边”白云岩形成时代为530±12Ma~502±12Ma,略新于灯影组地层年代。结合微量元素分析以及碳-氧-锶同位素数据,对川中地区震旦系灯影组“葡萄花边”白云岩进行成因分析。结果表明,其稀土元素总量(∑REE)相对较低(0.680×10^(-6)~8.963×10^(-6)),δ13 C VPDB(-0.1‰~1.7‰)略低于与同时期海水沉积白云岩的碳同位素值,δ18 O VPDB(-2.3‰~1.4‰)略高于与同时期海水达到氧同位素平衡的白云岩氧同位素值,87 Sr/86 Sr值(0.70876~0.70909)基本落入同时期海水范围。稀土元素配分总体为水平的模式,所有样品表现出Ce负异常。表明其形成环境既非海水沉积环境,也不完全是表生大气水岩溶条件。综合上述特征,推断川中地区震旦系灯影组“葡萄花边”白云岩是在震旦纪末-寒武纪早期海平面高频低幅度波动这一背景下,灯影组地层多次暴露与淹没,形成岩溶裂缝和孔洞的同时在溶蚀空间内结晶形成。残留孔洞为其后流体活动、油气充注提供了储集空间。本研究为认识川中地区震旦系灯影组“葡萄花边”白云岩成因、震旦纪末-寒武纪早期水化学条件、及超深层油气勘探开发提供了有益参考。
