On the basis of computational fluid dynamics,the flow field characteristics of multi-trophic artificial reefs,including the flow field distribution features of a single reef under three different velocities and the ef...On the basis of computational fluid dynamics,the flow field characteristics of multi-trophic artificial reefs,including the flow field distribution features of a single reef under three different velocities and the effect of spacing between reefs on flow scale and the flow state,were analyzed.Results indicate upwelling,slow flow,and eddy around a single reef.Maximum velocity,height,and volume of upwelling in front of a single reef were positively correlated with inflow velocity.The length and volume of slow flow increased with the increase in inflow velocity.Eddies were present both inside and backward,and vorticity was positively correlated with inflow velocity.Space between reefs had a minor influence on the maximum velocity and height of upwelling.With the increase in space from 0.5 L to 1.5 L(L is the reef lehgth),the length of slow flow in the front and back of the combined reefs increased slightly.When the space was 2.0 L,the length of the slow flow decreased.In four different spaces,eddies were present inside and at the back of each reef.The maximum vorticity was negatively correlated with space from 0.5 L to 1.5 L,but under 2.0 L space,the maximum vorticity was close to the vorticity of a single reef under the same inflow velocity.展开更多
Grassland degradation can alter the structure and function of ecosystem and soil seed bank.Therefore,estimating the role of soil seed bank in vegetation regeneration of degraded grasslands is crucial.We selected grass...Grassland degradation can alter the structure and function of ecosystem and soil seed bank.Therefore,estimating the role of soil seed bank in vegetation regeneration of degraded grasslands is crucial.We selected grasslands with three levels of degradation,namely non-degraded(ND),mildly degraded(MD),and heavily degraded(HD)to analyze the effect of grassland degradation on soil seed bank,as well as the role of soil seed bank on vegetation regeneration of the alpine grasslands,China.Soil samples from each level were collected in May,before seedling emergence,in August,after completion of transient seed bank germination,and in December,after seed dispersal,to determine the seed density and species composition through germination experiment.Result showed that a total of 35 plant species was identified,including 15 species observed in both soil seed bank and above-ground vegetation.A total of 19,15,and 14 species of soil seed bank were identified in December,May,and August,respectively.The most abundant species in soil seed bank were Compositae(5 species),followed by Poaceae(4 species),and Cyperaceae(3 species).Degradation level has no significant impact on species richness and Shannon-Wiener index of soil seed bank.In addition,sampling month and grassland degradation affected soil seed bank density,in which December>May>August,and ND>MD>HD,indicating that density of transient seed bank was greater than persistent seed bank.Soil seed bank density of surface layer(0–5 cm)accounting for 42%–72%of the total density,which was significantly higher than that of deep layer(5–10 cm).Similarity of species composition between vegetation and soil seed bank was low,and it increased with degradation level(ranged from 0.14 to 0.69).We concluded that grassland degradation affects soil seed bank density more than species diversity,and soil seed bank contributed slightly to vegetation regeneration of degraded alpine grassland.Therefore,it is unlikely that degraded alpine meadow can be restored solely through soil seed bank.展开更多
随着移动通信网络的迅猛发展,其安全漏洞产生的影响更为广泛,使得安全性研究尤为重要。根据长期演进(Long Term Evolution,LTE)非接入层协议的漏洞,构建了针对网络端和终端的两种拒绝服务攻击模型,通过获取不同终端的国际移动用户标识...随着移动通信网络的迅猛发展,其安全漏洞产生的影响更为广泛,使得安全性研究尤为重要。根据长期演进(Long Term Evolution,LTE)非接入层协议的漏洞,构建了针对网络端和终端的两种拒绝服务攻击模型,通过获取不同终端的国际移动用户标识并分别伪造鉴权拒绝消息和附着请求消息对目标发起不同危害程度的拒绝服务攻击。实验结果表明,采用鉴权拒绝发起的攻击会使目标终端强制降为2G网络;而采用附着请求发起的攻击会使核心网侧中央处理器(Central Processing Unit,CPU)使用率由30%提升至80%,造成网络资源消耗巨大,导致用户很难正常接入。研究结论有助于推进非接入层协议的安全演进。展开更多
为了研究移动通信漏洞对用户速率的影响,针对空口中接入层用户设备能力信息以明文传输的特点,提出了一种在用户设备和真实网络之间中继并修改长期演进(long term evolution,LTE)信令的中间人攻击方案。该方案将目标终端吸引至中间人系统...为了研究移动通信漏洞对用户速率的影响,针对空口中接入层用户设备能力信息以明文传输的特点,提出了一种在用户设备和真实网络之间中继并修改长期演进(long term evolution,LTE)信令的中间人攻击方案。该方案将目标终端吸引至中间人系统,同时中间人系统中的终端以目标终端的国际移动用户标识(international mobile subscriber identity,IMSI)向真实网络发起注册,中间人系统中继传递目标终端和真实网络的信令,对接收到的接入层用户设备能力信息修改再转发至真实网络,从而使得目标终端的数据速率下降。测试结果表明,攻击导致目标终端的下行传输速率从64.9 Mbps降低到8.1 Mbps,上行传输速率从38.3 Mbps降低到3.5 Mbps。由于该攻击具有普遍适用性,该工作可以为移动通信网络改进提供参考。展开更多
背景与目的:乳腺癌在30岁以下的青年女性中很罕见,但近几年乳腺癌趋向年轻化并且发病率逐年增高,而早期乳腺癌免疫组织化学分子亚型的识别可以完善治疗方案。该研究旨在探讨青年女性(≤30岁)乳腺癌的超声、数字乳腺X线摄影(digital mamm...背景与目的:乳腺癌在30岁以下的青年女性中很罕见,但近几年乳腺癌趋向年轻化并且发病率逐年增高,而早期乳腺癌免疫组织化学分子亚型的识别可以完善治疗方案。该研究旨在探讨青年女性(≤30岁)乳腺癌的超声、数字乳腺X线摄影(digital mammography,DM)及数字乳腺断层合成摄影(digital breast tomosynthesis,DBT)特征与免疫组织化学分子亚型的相关性。方法:回顾并分析2013年12月—2019年7月于青岛大学附属医院进行过乳腺超声、DM和DBT检查,且经手术后病理学检查证实为乳腺癌,年龄≤30岁的139例青年女性患者。影像学特征参照第5版乳腺影像报告及数据系统(Breast Imaging Reporting and Data System,BI-RADS)进行评估及分类。对肿块样病变,3种检查方法均评估了病变的形状、边缘,DM和DBT对肿块密度另加以评估,超声对病变内部回声、后方回声、血流信号另加以评估;对异常钙化评估其形态及分布;依据BI-RADS评估了乳腺纤维腺体构成;分子亚型根据2015年修订的St.Gallen国际专家共识建议确定。结果:病变多表现为可触及肿块(89.9%)、临床T2期(50.4%)、组织学Ⅱ级(58.3%)、腋窝淋巴结转移(59.7%)、luminal B型乳腺癌(44.6%),BI-RADS多为4类或5类。在所有成像中,肿块病变均多表现为不规则形(P<0.001),luminal A型乳腺癌及三阴性乳腺癌(triple-negative breast cancer,TNBC)多为肿块样病变,luminal B型乳腺癌中肿块伴钙化病变多见,HER2过表达型多见单纯钙化样病变(P<0.001)。在DM和DBT上,诊断为阴性情况更常见于luminal A型乳腺癌(P<0.001)。对于肿块样病变,DM中最常见表现为边缘模糊(71.9%),而DBT多见毛刺影(51.8%),毛刺边缘多与luminal A和luminal B型乳腺癌相关(P<0.01)。良性影像学特征多与TNBC相关,表现为卵圆形或圆形(P<0.001),边缘清楚(P<0.01)。HER2过表达型和TNBC型两组中肿块病变的范围均大于luminal A和luminal B型乳腺癌(P=0.003)。结论:30岁以下青年女性乳腺癌的部分影像学特征可用于预测某些肿瘤免疫组织化学分子亚型。DBT的乳腺癌检出率高于DM,对乳腺致密的青年女性具有广泛的应用价值。展开更多
基金supported by the National Natural Science Foundation of China(No.32002442)the National Key R&D Program(No.2019YFD0902101).
文摘On the basis of computational fluid dynamics,the flow field characteristics of multi-trophic artificial reefs,including the flow field distribution features of a single reef under three different velocities and the effect of spacing between reefs on flow scale and the flow state,were analyzed.Results indicate upwelling,slow flow,and eddy around a single reef.Maximum velocity,height,and volume of upwelling in front of a single reef were positively correlated with inflow velocity.The length and volume of slow flow increased with the increase in inflow velocity.Eddies were present both inside and backward,and vorticity was positively correlated with inflow velocity.Space between reefs had a minor influence on the maximum velocity and height of upwelling.With the increase in space from 0.5 L to 1.5 L(L is the reef lehgth),the length of slow flow in the front and back of the combined reefs increased slightly.When the space was 2.0 L,the length of the slow flow decreased.In four different spaces,eddies were present inside and at the back of each reef.The maximum vorticity was negatively correlated with space from 0.5 L to 1.5 L,but under 2.0 L space,the maximum vorticity was close to the vorticity of a single reef under the same inflow velocity.
基金supported by the National Natural Science Foundation of China (31960279)the Science and Technology Program of Gansu Province, China (21JR11RA018)+1 种基金the Special Project for Central Universities to Build World-class Universities/Disciplines, and Characteristic Development GuidanceProgram for Changjiang Scholars and Innovative Research Team in University of Ministry of Education, China (IRT_17R88)
文摘Grassland degradation can alter the structure and function of ecosystem and soil seed bank.Therefore,estimating the role of soil seed bank in vegetation regeneration of degraded grasslands is crucial.We selected grasslands with three levels of degradation,namely non-degraded(ND),mildly degraded(MD),and heavily degraded(HD)to analyze the effect of grassland degradation on soil seed bank,as well as the role of soil seed bank on vegetation regeneration of the alpine grasslands,China.Soil samples from each level were collected in May,before seedling emergence,in August,after completion of transient seed bank germination,and in December,after seed dispersal,to determine the seed density and species composition through germination experiment.Result showed that a total of 35 plant species was identified,including 15 species observed in both soil seed bank and above-ground vegetation.A total of 19,15,and 14 species of soil seed bank were identified in December,May,and August,respectively.The most abundant species in soil seed bank were Compositae(5 species),followed by Poaceae(4 species),and Cyperaceae(3 species).Degradation level has no significant impact on species richness and Shannon-Wiener index of soil seed bank.In addition,sampling month and grassland degradation affected soil seed bank density,in which December>May>August,and ND>MD>HD,indicating that density of transient seed bank was greater than persistent seed bank.Soil seed bank density of surface layer(0–5 cm)accounting for 42%–72%of the total density,which was significantly higher than that of deep layer(5–10 cm).Similarity of species composition between vegetation and soil seed bank was low,and it increased with degradation level(ranged from 0.14 to 0.69).We concluded that grassland degradation affects soil seed bank density more than species diversity,and soil seed bank contributed slightly to vegetation regeneration of degraded alpine grassland.Therefore,it is unlikely that degraded alpine meadow can be restored solely through soil seed bank.
文摘随着移动通信网络的迅猛发展,其安全漏洞产生的影响更为广泛,使得安全性研究尤为重要。根据长期演进(Long Term Evolution,LTE)非接入层协议的漏洞,构建了针对网络端和终端的两种拒绝服务攻击模型,通过获取不同终端的国际移动用户标识并分别伪造鉴权拒绝消息和附着请求消息对目标发起不同危害程度的拒绝服务攻击。实验结果表明,采用鉴权拒绝发起的攻击会使目标终端强制降为2G网络;而采用附着请求发起的攻击会使核心网侧中央处理器(Central Processing Unit,CPU)使用率由30%提升至80%,造成网络资源消耗巨大,导致用户很难正常接入。研究结论有助于推进非接入层协议的安全演进。
文摘为了研究移动通信漏洞对用户速率的影响,针对空口中接入层用户设备能力信息以明文传输的特点,提出了一种在用户设备和真实网络之间中继并修改长期演进(long term evolution,LTE)信令的中间人攻击方案。该方案将目标终端吸引至中间人系统,同时中间人系统中的终端以目标终端的国际移动用户标识(international mobile subscriber identity,IMSI)向真实网络发起注册,中间人系统中继传递目标终端和真实网络的信令,对接收到的接入层用户设备能力信息修改再转发至真实网络,从而使得目标终端的数据速率下降。测试结果表明,攻击导致目标终端的下行传输速率从64.9 Mbps降低到8.1 Mbps,上行传输速率从38.3 Mbps降低到3.5 Mbps。由于该攻击具有普遍适用性,该工作可以为移动通信网络改进提供参考。
文摘背景与目的:乳腺癌在30岁以下的青年女性中很罕见,但近几年乳腺癌趋向年轻化并且发病率逐年增高,而早期乳腺癌免疫组织化学分子亚型的识别可以完善治疗方案。该研究旨在探讨青年女性(≤30岁)乳腺癌的超声、数字乳腺X线摄影(digital mammography,DM)及数字乳腺断层合成摄影(digital breast tomosynthesis,DBT)特征与免疫组织化学分子亚型的相关性。方法:回顾并分析2013年12月—2019年7月于青岛大学附属医院进行过乳腺超声、DM和DBT检查,且经手术后病理学检查证实为乳腺癌,年龄≤30岁的139例青年女性患者。影像学特征参照第5版乳腺影像报告及数据系统(Breast Imaging Reporting and Data System,BI-RADS)进行评估及分类。对肿块样病变,3种检查方法均评估了病变的形状、边缘,DM和DBT对肿块密度另加以评估,超声对病变内部回声、后方回声、血流信号另加以评估;对异常钙化评估其形态及分布;依据BI-RADS评估了乳腺纤维腺体构成;分子亚型根据2015年修订的St.Gallen国际专家共识建议确定。结果:病变多表现为可触及肿块(89.9%)、临床T2期(50.4%)、组织学Ⅱ级(58.3%)、腋窝淋巴结转移(59.7%)、luminal B型乳腺癌(44.6%),BI-RADS多为4类或5类。在所有成像中,肿块病变均多表现为不规则形(P<0.001),luminal A型乳腺癌及三阴性乳腺癌(triple-negative breast cancer,TNBC)多为肿块样病变,luminal B型乳腺癌中肿块伴钙化病变多见,HER2过表达型多见单纯钙化样病变(P<0.001)。在DM和DBT上,诊断为阴性情况更常见于luminal A型乳腺癌(P<0.001)。对于肿块样病变,DM中最常见表现为边缘模糊(71.9%),而DBT多见毛刺影(51.8%),毛刺边缘多与luminal A和luminal B型乳腺癌相关(P<0.01)。良性影像学特征多与TNBC相关,表现为卵圆形或圆形(P<0.001),边缘清楚(P<0.01)。HER2过表达型和TNBC型两组中肿块病变的范围均大于luminal A和luminal B型乳腺癌(P=0.003)。结论:30岁以下青年女性乳腺癌的部分影像学特征可用于预测某些肿瘤免疫组织化学分子亚型。DBT的乳腺癌检出率高于DM,对乳腺致密的青年女性具有广泛的应用价值。
