Beach rock,which forms at the intertidal zone,is a natural barrier to protect beach and island from wave erosion. The formation mechanism of beach rocks is significant in the study of surface carbonate diagenesis and ...Beach rock,which forms at the intertidal zone,is a natural barrier to protect beach and island from wave erosion. The formation mechanism of beach rocks is significant in the study of surface carbonate diagenesis and protection of island. Beach rocks in Qilian Islets and Cays were formed about 500–700 a BP,neither its composition nor sedimentary structure experienced intense post-reformation.Beach rocks in Qilian Islets and Cays are mainly composed of reef-building skeletal fragments and bioclasts without terrigenous sediments. This study focused on the types and morphologies of cements in beach rocks of Qilian Islets and Cays,and its cementation mechanisms and influencing factors. Biological activities,such as micritization caused by microbial activities and algae binding action,play an important role in the initial stage of bioclast transformation and promote the subsequent early marine and early meteoric cementation. Acicular aragonite induced by early marine cementation is well developed in beach rocks,especially in those samples from Medium Islet. Early meteoric cementation is not common as marine cementation,generally presenting granular and meniscus cements. The main factors affecting the formation and development of beach rocks in Qilian Islets and Cays include sediment source,hydrodynamic condition,climate,sea level change and anthropogenic impacts.展开更多
Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know litt...Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know little about them, especially those recently formed sand cays. In this research, we monitor migration of a new sand cay in Nanxun Jiao（Gaven Reef） using a series of Quick Bird and World View-2 satellite images between June 2006 and August 2013. We conduct a regression between migration distance and wind observational data to examine the migration patterns of the new sand cay. The migration distance is calculated based on the sand cay locations extracted based on Normalized Difference Water Index（NDWI）. The wind observational data downloaded from NOAA are reformed into four wind direction vectors. Based on the results of regression, we concluded that the migration of the new sand cay on Nanxun Jiao was significantly associated with the east, west and north wind.East wind was the main influence factor of the migration; its impact strength was almost twice as the west and north wind. The south wind has little effect on the migration of the sand cay, which is partly blocked by the artificial structure in the south.展开更多
Given the socio-economic consequences associated with declaring areas of ocean protected in order to achieve conservation objectives, this paper contributes to the growing global need to assess Marine Protected Areas ...Given the socio-economic consequences associated with declaring areas of ocean protected in order to achieve conservation objectives, this paper contributes to the growing global need to assess Marine Protected Areas (MPAs) as an effective management tool. It adds to the current body of knowledge on MPA effectiveness by conducting an evaluation of the Tobago Cays Marine Park (TCMP), located in St. Vincent and the Grenadines (SVG) in the eastern Caribbean, using a modified MPA effectiveness framework. Due to the limited information existing about the current performance of this MPA, this assessment also provides needed insight on the effect that the TCMP is having on the marine ecosystem, as well as its overall management performance. By comparing the performance of the MPA over a 10-year span (2007 and 2016), the results indicate that overall, the TCMP could be described as having limited success when key management categories of context, planning, input, process, output and outcomes are evaluated. In particular, efforts dedicated to planning, process and outcomes are assessed as deficient. Furthermore, the analysis revealed that efforts to realize the stated goals relating to conservation, public awareness and public education were being neglected. However, considerable effort was being expended by TCMP staff on achieving the remaining goal focusing on deriving economic benefits from touristic activities in the Park. Preliminary field research examining the effects of the TCMP on the abundance and density of an economically important species, Lobatus gigas, (commonly referred to as the queen conch) showed the TCMP as having no effect towards conch protection. The results and recommendations of this study, combined with continued monitoring of a recommended targeted suite of indicators, could contribute to better-informed adaptive MPA management, leading to progress towards the achievement of the stated goals for the TCMP.展开更多
It has been conjectured that there is a hamiltonian cycle in every finite connected Cayley graph.In spite of the difficulty in proving this conjecture,we show that almost all Cayley graphs are hamiltonian.That is,as t...It has been conjectured that there is a hamiltonian cycle in every finite connected Cayley graph.In spite of the difficulty in proving this conjecture,we show that almost all Cayley graphs are hamiltonian.That is,as the order n of a group G approaches infinity,the ratio of the number of hamiltonian Cayley graphs of G to the total number of Cayley graphs of G approaches 1.展开更多
随着口腔种植技术的发展,种植体的精准植入逐渐成为口腔种植领域热议的话题。计算机辅助种植(computer-assisted implant surgery, CAIs)技术的出现,从静态导板技术到动态导航技术,再到最近几年兴起的口腔种植机器人,使得种植体的精准...随着口腔种植技术的发展,种植体的精准植入逐渐成为口腔种植领域热议的话题。计算机辅助种植(computer-assisted implant surgery, CAIs)技术的出现,从静态导板技术到动态导航技术,再到最近几年兴起的口腔种植机器人,使得种植体的精准植入成为可能。本文就目前存在的三种计算机辅助种植技术在发展分类、操作流程、精度及其影响因素做一综述,并指出了各种技术存在的不足,以期为口腔临床数字化种植的选择提供参考。With the development of oral implant technology, the precise placement of implants is becoming a hot topic of discussion in the field of oral implantology. The emergence of computer-assisted implant surgery (CAIs), from static guides to dynamic navigation, and the rise of dental implant robots in recent years, has made it possible to accurately implant implants. This article reviews the principle classification, workflow, accuracy and its influencing factors of three computer-assisted implant surgery, and points out the shortcomings of each surgery in order to provide reference for the selection of dental clinical digital implant.展开更多
超声成像作为一种无创、快速且方便的检查方法,在甲状腺结节的诊断治疗和随访中发挥着重要作用。其缺点包括:观察者之间和观察者内部的高差异性、有限的视野和有限的功能成像。随着医学的不断进步和超声设备的日益完善,超声成像正在克...超声成像作为一种无创、快速且方便的检查方法,在甲状腺结节的诊断治疗和随访中发挥着重要作用。其缺点包括:观察者之间和观察者内部的高差异性、有限的视野和有限的功能成像。随着医学的不断进步和超声设备的日益完善,超声成像正在克服这些限制,包括三维多普勒、弹性成像、结节特征提取和新型机器学习算法。本文综述了超声成像在甲状腺结节领域的应用现状和未来趋势,并讨论了可能改善甲状腺结节的诊断、治疗和随访的新发展和趋势的潜力。As a non-invasive, rapid and convenient examination method, ultrasound imaging plays an important role in the diagnosis, treatment and follow-up of thyroid nodules. Disadvantages include high variability between and within observers, limited field of view, and limited functional imaging. With the continuous advancement of medicine and the increasing sophistication of ultrasound equipment, ultrasound imaging is overcoming these limitations, including 3D Doppler, elastography, nodule feature extraction, and novel machine learning algorithms. This article reviews the current status and future trends of ultrasound imaging in the field of thyroid nodules, and discusses the potential of new developments and trends that may improve the diagnosis, treatment, and follow-up of thyroid nodules.展开更多
To reduce the uncertainty associated with the traditional definition of tunnel boring machine(TBM)utilization(U)and achieve an effective indicator of TBM performance,a new performance indicator called rock mass-relate...To reduce the uncertainty associated with the traditional definition of tunnel boring machine(TBM)utilization(U)and achieve an effective indicator of TBM performance,a new performance indicator called rock mass-related utilization(U_(r))is introduced;this variable considers only rock mass-related factors rather than all potential factors.This work aims to predict U_(r)by adopting the rock mass rating(RMR)and the moisture-dependent Cerchar abrasivity index(CAI).Substantial U_(r),RMR and CAI data are acquired from a 31.57 km northwestern Chinese water conveyance tunnel via tunnelling field recordings,geological investigations and Cerchar abrasivity tests.The moisture dependence of the CAI is explored across four lithologies:quartz schists,granites,sandstones and metamorphic andesites.The potential influences of RMR and CAI on Ur are then investigated.As the RMR increases,U_(r)initially increases and then peaks at an RMR of 56 before declining.U_(r)appears to decline with CAI.An investigation-based relation among U_(r),RMR and moisture-dependent CAI is developed for estimating U_(r).The developed relation can accurately predict U_(r)using RMR and moisture-dependent CAI in the majority of the tunnelling cases examined.This work proposes a stable indicator of TBM performance and provided a fairly accurate prediction method for this indicator.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41672107, 41372119, 41440040)supports provided by the Marine Environmental Observation and Research Station at the Xisha Islands, the South China Sea Institute of Oceanology, CAS during the fieldwork
文摘Beach rock,which forms at the intertidal zone,is a natural barrier to protect beach and island from wave erosion. The formation mechanism of beach rocks is significant in the study of surface carbonate diagenesis and protection of island. Beach rocks in Qilian Islets and Cays were formed about 500–700 a BP,neither its composition nor sedimentary structure experienced intense post-reformation.Beach rocks in Qilian Islets and Cays are mainly composed of reef-building skeletal fragments and bioclasts without terrigenous sediments. This study focused on the types and morphologies of cements in beach rocks of Qilian Islets and Cays,and its cementation mechanisms and influencing factors. Biological activities,such as micritization caused by microbial activities and algae binding action,play an important role in the initial stage of bioclast transformation and promote the subsequent early marine and early meteoric cementation. Acicular aragonite induced by early marine cementation is well developed in beach rocks,especially in those samples from Medium Islet. Early meteoric cementation is not common as marine cementation,generally presenting granular and meniscus cements. The main factors affecting the formation and development of beach rocks in Qilian Islets and Cays include sediment source,hydrodynamic condition,climate,sea level change and anthropogenic impacts.
基金National Sea Islands Protection and Management Programme
文摘Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know little about them, especially those recently formed sand cays. In this research, we monitor migration of a new sand cay in Nanxun Jiao（Gaven Reef） using a series of Quick Bird and World View-2 satellite images between June 2006 and August 2013. We conduct a regression between migration distance and wind observational data to examine the migration patterns of the new sand cay. The migration distance is calculated based on the sand cay locations extracted based on Normalized Difference Water Index（NDWI）. The wind observational data downloaded from NOAA are reformed into four wind direction vectors. Based on the results of regression, we concluded that the migration of the new sand cay on Nanxun Jiao was significantly associated with the east, west and north wind.East wind was the main influence factor of the migration; its impact strength was almost twice as the west and north wind. The south wind has little effect on the migration of the sand cay, which is partly blocked by the artificial structure in the south.
文摘Given the socio-economic consequences associated with declaring areas of ocean protected in order to achieve conservation objectives, this paper contributes to the growing global need to assess Marine Protected Areas (MPAs) as an effective management tool. It adds to the current body of knowledge on MPA effectiveness by conducting an evaluation of the Tobago Cays Marine Park (TCMP), located in St. Vincent and the Grenadines (SVG) in the eastern Caribbean, using a modified MPA effectiveness framework. Due to the limited information existing about the current performance of this MPA, this assessment also provides needed insight on the effect that the TCMP is having on the marine ecosystem, as well as its overall management performance. By comparing the performance of the MPA over a 10-year span (2007 and 2016), the results indicate that overall, the TCMP could be described as having limited success when key management categories of context, planning, input, process, output and outcomes are evaluated. In particular, efforts dedicated to planning, process and outcomes are assessed as deficient. Furthermore, the analysis revealed that efforts to realize the stated goals relating to conservation, public awareness and public education were being neglected. However, considerable effort was being expended by TCMP staff on achieving the remaining goal focusing on deriving economic benefits from touristic activities in the Park. Preliminary field research examining the effects of the TCMP on the abundance and density of an economically important species, Lobatus gigas, (commonly referred to as the queen conch) showed the TCMP as having no effect towards conch protection. The results and recommendations of this study, combined with continued monitoring of a recommended targeted suite of indicators, could contribute to better-informed adaptive MPA management, leading to progress towards the achievement of the stated goals for the TCMP.
基金Supported by the National Natural Science Foundation of China,Xinjiang Educational Committee and Xinjiang University.
文摘It has been conjectured that there is a hamiltonian cycle in every finite connected Cayley graph.In spite of the difficulty in proving this conjecture,we show that almost all Cayley graphs are hamiltonian.That is,as the order n of a group G approaches infinity,the ratio of the number of hamiltonian Cayley graphs of G to the total number of Cayley graphs of G approaches 1.
文摘随着口腔种植技术的发展,种植体的精准植入逐渐成为口腔种植领域热议的话题。计算机辅助种植(computer-assisted implant surgery, CAIs)技术的出现,从静态导板技术到动态导航技术,再到最近几年兴起的口腔种植机器人,使得种植体的精准植入成为可能。本文就目前存在的三种计算机辅助种植技术在发展分类、操作流程、精度及其影响因素做一综述,并指出了各种技术存在的不足,以期为口腔临床数字化种植的选择提供参考。With the development of oral implant technology, the precise placement of implants is becoming a hot topic of discussion in the field of oral implantology. The emergence of computer-assisted implant surgery (CAIs), from static guides to dynamic navigation, and the rise of dental implant robots in recent years, has made it possible to accurately implant implants. This article reviews the principle classification, workflow, accuracy and its influencing factors of three computer-assisted implant surgery, and points out the shortcomings of each surgery in order to provide reference for the selection of dental clinical digital implant.
文摘超声成像作为一种无创、快速且方便的检查方法,在甲状腺结节的诊断治疗和随访中发挥着重要作用。其缺点包括:观察者之间和观察者内部的高差异性、有限的视野和有限的功能成像。随着医学的不断进步和超声设备的日益完善,超声成像正在克服这些限制,包括三维多普勒、弹性成像、结节特征提取和新型机器学习算法。本文综述了超声成像在甲状腺结节领域的应用现状和未来趋势,并讨论了可能改善甲状腺结节的诊断、治疗和随访的新发展和趋势的潜力。As a non-invasive, rapid and convenient examination method, ultrasound imaging plays an important role in the diagnosis, treatment and follow-up of thyroid nodules. Disadvantages include high variability between and within observers, limited field of view, and limited functional imaging. With the continuous advancement of medicine and the increasing sophistication of ultrasound equipment, ultrasound imaging is overcoming these limitations, including 3D Doppler, elastography, nodule feature extraction, and novel machine learning algorithms. This article reviews the current status and future trends of ultrasound imaging in the field of thyroid nodules, and discusses the potential of new developments and trends that may improve the diagnosis, treatment, and follow-up of thyroid nodules.
基金financially supported by the National Natural Science Foundation of China(Nos.41972270,52076198)the Key Research and Development Plan of Henan Province(No.182102210014)+2 种基金the Excellent Youth Foundation of Henan Scientific Committee(No.222300420078)the Youth Talent Promotion Project of Henan Province(No.2022HYTP019)the Open Foundation of State Key Laboratory of Shield Machine and Boring Technology(No.SKLST-2019-K06)。
文摘To reduce the uncertainty associated with the traditional definition of tunnel boring machine(TBM)utilization(U)and achieve an effective indicator of TBM performance,a new performance indicator called rock mass-related utilization(U_(r))is introduced;this variable considers only rock mass-related factors rather than all potential factors.This work aims to predict U_(r)by adopting the rock mass rating(RMR)and the moisture-dependent Cerchar abrasivity index(CAI).Substantial U_(r),RMR and CAI data are acquired from a 31.57 km northwestern Chinese water conveyance tunnel via tunnelling field recordings,geological investigations and Cerchar abrasivity tests.The moisture dependence of the CAI is explored across four lithologies:quartz schists,granites,sandstones and metamorphic andesites.The potential influences of RMR and CAI on Ur are then investigated.As the RMR increases,U_(r)initially increases and then peaks at an RMR of 56 before declining.U_(r)appears to decline with CAI.An investigation-based relation among U_(r),RMR and moisture-dependent CAI is developed for estimating U_(r).The developed relation can accurately predict U_(r)using RMR and moisture-dependent CAI in the majority of the tunnelling cases examined.This work proposes a stable indicator of TBM performance and provided a fairly accurate prediction method for this indicator.
