Brittle failure of rocks is a classical rock mechanical problem. Rock failure not only involves initiation and propagation of single crack, but also is associated with initiation, propagation and coalescence of many c...Brittle failure of rocks is a classical rock mechanical problem. Rock failure not only involves initiation and propagation of single crack, but also is associated with initiation, propagation and coalescence of many cracks. The rock failure process analysis （RFPA） tool has been proposed since 1995. The heterogeneity of rocks at a mesoscopic level is considered by assuming that the material properties follow the Weibull distribution. Elastic damage mechanics is used for describing the constitutive law of the meso-level element. The finite element method （FEM） is employed as the basic stress analysis tool. The maximum tensile strain criterion and the Mohr-Coulomb criterion are utilized as the damage threshold. In order to solve the stability problem related to rock engineering structures, fundamental principles of strength reduction method （SRM） and gravity increase method （GIM） are integrated into the RFPA. And the acoustic emission （AE） event rate is employed as the criterion for rock engineering failure. The prominent feature of the RFPA-SRM and RFPA-GIM for stability analysis of rock engineering is that the factor of safety can be obtained without any presumption for the shape and location of the failure surface. In this paper, several geotechnical engineering applications that use the RFPA method to analyze their stability are presented to provide some references for relevant researches. The principles of the RFPA method in engineering are introduced firstly, and then the stability analysis of tunnel, slope and dam is focused on. The results indicate that the RFPA method is capable of capturing the mechanism of rock engineering stability and has the potential for application in a larger range of geo-engineering.展开更多
BACKGROUND Benzbromarone is a uricosuric agent that reduces proximal tubular reabsorption of uric acid.Because of hepatotoxicity,it has been withdrawn from the market in Europe.Recently,some benefit-risk assessments o...BACKGROUND Benzbromarone is a uricosuric agent that reduces proximal tubular reabsorption of uric acid.Because of hepatotoxicity,it has been withdrawn from the market in Europe.Recently,some benefit-risk assessments of benzbromarone suggest that benzbromarone has greater benefits than risks,and the application of benzbromarone in the treatment of gout and hyperuricemia is still under debate.CASE S UMMARY A 39-year-old man was admitted to the hospital for icterus and nausea,and he was treated with benzbromarone(100 mg/d)for 4 mo because of hyperuricemia He had a 10-year history of beer drinking(alcohol:about 28 g/d).Laboratory data showed severe liver injury and serious coagulation dysfunction;tests for autoimmune antibodies,viral hepatitis,and human immunodeficiency virus were negative.Despite administration of liver function-protecting drugs and efficient supportive treatment,the patient deteriorated quickly after hospitalization and developed grade Ⅱ encephalopathy within a few days.The patient accepted continuous plasma exchange six times;however,his condition did not improve.Based on suggestions from multidisciplinary consultation,the patient underwent liver transplantation 26 d after admission.Liver specimen pathology results showed massive necrosis consistent with drug-induced liver injury,supporting the diagnosis of acute liver failure associated with benzbromarone.The patient recovered quickly thereafter.CONCL USION This case highlights that clinicians should be on the alert for the severe hepatotoxicity of benzbromarone.Before prescribing benzbromarone,physicians should evaluate the high-risk factors that may lead to liver injury and provide suggestions for monitoring benzbromarone’s hepatotoxicity during treatment.展开更多
电力设备在运行维护中积累了大量包含重要实体信息的故障文本,然而文本实体边界模糊、术语较多等特点导致传统实体识别方法训练效率低下,效果难以提升。为此,该文提出一种新的实体识别方法I-BRC(integrated algorithm of BERT based BiR...电力设备在运行维护中积累了大量包含重要实体信息的故障文本,然而文本实体边界模糊、术语较多等特点导致传统实体识别方法训练效率低下,效果难以提升。为此,该文提出一种新的实体识别方法I-BRC(integrated algorithm of BERT based BiRNN with CRF)。该方法采用字嵌入模型将文本逐字转化为字向量序列以避免分词处理带来的误差累积;利用循环神经网络与概率图模型对文本的序列特征信息进行抽取;集成多个单一类型实体识别器分别独立学习不同类型实体的特征并采用并行预训练机制提升算法训练效率;最后利用多类型识别器对识别结果进行整合。此外,通过调整单一类型实体识别器可以灵活机动地应对不同电力设备的实体识别任务,避免重复训练,节省计算资源。实验表明,所提出的I-BRC仅需3次迭代就可收敛,训练效率大幅度提升;且该模型的F1值、精确率、召回率分别达到了88.0%、86.8%与89.2%,相比传统模型性能提升了7.5%~29.3%,验证了所提模型的有效性与可行性。展开更多
The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a re...The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a result,structurally-controlled failures(e.g.planar,wedge or toppling)are most likely to occur.The probabilistic approach offers a major advantage over the traditional deterministic method in that it accounts for the different degrees of variability and uncertainty often encountered in rock properties.This paper presents a bench slope stability assessment for an open pit mine in Peru using a probabilistic-based approach by coupling a kinematic analysis based on stereographic projection techniques followed by a kinetic analysis by means of the limit equilibrium method.Finally,these two probabilities are combined to provide an overall measure of the probability of failure(PoF)of the bench slope system.The case study is characterized by significant scatter in the geometrical and mechanical properties of the joints.Extensive surface mapping was conducted at 36 different sites following the ISRM suggested procedures.Several direct shear tests were carried out.It is shown that by combining field and laboratory measurements and engineering judgment,the probability density functions(PDF)of the discontinuity parameters can be obtained.These are then used in a Monte Carlo simulation process to compute both kinematic and kinetic probabilities of failure.The overall probability of failure aims to provide the design engineer with a tool to critically evaluate the bench performance from a geotechnical risk perspective and to provide a basis for future bench design optimization.展开更多
基金Supported by the State Key Development Program for Basic Research of China(2007CB209400)Projects of International Cooperation and Exchanges NSFC(50820125405)the National Natural Science Foundation of China(51004020)
文摘Brittle failure of rocks is a classical rock mechanical problem. Rock failure not only involves initiation and propagation of single crack, but also is associated with initiation, propagation and coalescence of many cracks. The rock failure process analysis （RFPA） tool has been proposed since 1995. The heterogeneity of rocks at a mesoscopic level is considered by assuming that the material properties follow the Weibull distribution. Elastic damage mechanics is used for describing the constitutive law of the meso-level element. The finite element method （FEM） is employed as the basic stress analysis tool. The maximum tensile strain criterion and the Mohr-Coulomb criterion are utilized as the damage threshold. In order to solve the stability problem related to rock engineering structures, fundamental principles of strength reduction method （SRM） and gravity increase method （GIM） are integrated into the RFPA. And the acoustic emission （AE） event rate is employed as the criterion for rock engineering failure. The prominent feature of the RFPA-SRM and RFPA-GIM for stability analysis of rock engineering is that the factor of safety can be obtained without any presumption for the shape and location of the failure surface. In this paper, several geotechnical engineering applications that use the RFPA method to analyze their stability are presented to provide some references for relevant researches. The principles of the RFPA method in engineering are introduced firstly, and then the stability analysis of tunnel, slope and dam is focused on. The results indicate that the RFPA method is capable of capturing the mechanism of rock engineering stability and has the potential for application in a larger range of geo-engineering.
文摘BACKGROUND Benzbromarone is a uricosuric agent that reduces proximal tubular reabsorption of uric acid.Because of hepatotoxicity,it has been withdrawn from the market in Europe.Recently,some benefit-risk assessments of benzbromarone suggest that benzbromarone has greater benefits than risks,and the application of benzbromarone in the treatment of gout and hyperuricemia is still under debate.CASE S UMMARY A 39-year-old man was admitted to the hospital for icterus and nausea,and he was treated with benzbromarone(100 mg/d)for 4 mo because of hyperuricemia He had a 10-year history of beer drinking(alcohol:about 28 g/d).Laboratory data showed severe liver injury and serious coagulation dysfunction;tests for autoimmune antibodies,viral hepatitis,and human immunodeficiency virus were negative.Despite administration of liver function-protecting drugs and efficient supportive treatment,the patient deteriorated quickly after hospitalization and developed grade Ⅱ encephalopathy within a few days.The patient accepted continuous plasma exchange six times;however,his condition did not improve.Based on suggestions from multidisciplinary consultation,the patient underwent liver transplantation 26 d after admission.Liver specimen pathology results showed massive necrosis consistent with drug-induced liver injury,supporting the diagnosis of acute liver failure associated with benzbromarone.The patient recovered quickly thereafter.CONCL USION This case highlights that clinicians should be on the alert for the severe hepatotoxicity of benzbromarone.Before prescribing benzbromarone,physicians should evaluate the high-risk factors that may lead to liver injury and provide suggestions for monitoring benzbromarone’s hepatotoxicity during treatment.
文摘电力设备在运行维护中积累了大量包含重要实体信息的故障文本,然而文本实体边界模糊、术语较多等特点导致传统实体识别方法训练效率低下,效果难以提升。为此,该文提出一种新的实体识别方法I-BRC(integrated algorithm of BERT based BiRNN with CRF)。该方法采用字嵌入模型将文本逐字转化为字向量序列以避免分词处理带来的误差累积;利用循环神经网络与概率图模型对文本的序列特征信息进行抽取;集成多个单一类型实体识别器分别独立学习不同类型实体的特征并采用并行预训练机制提升算法训练效率;最后利用多类型识别器对识别结果进行整合。此外,通过调整单一类型实体识别器可以灵活机动地应对不同电力设备的实体识别任务,避免重复训练,节省计算资源。实验表明,所提出的I-BRC仅需3次迭代就可收敛,训练效率大幅度提升;且该模型的F1值、精确率、召回率分别达到了88.0%、86.8%与89.2%,相比传统模型性能提升了7.5%~29.3%,验证了所提模型的有效性与可行性。
基金supported by a scholarship from the Peruvian Institute of Mining Engineers
文摘The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a result,structurally-controlled failures(e.g.planar,wedge or toppling)are most likely to occur.The probabilistic approach offers a major advantage over the traditional deterministic method in that it accounts for the different degrees of variability and uncertainty often encountered in rock properties.This paper presents a bench slope stability assessment for an open pit mine in Peru using a probabilistic-based approach by coupling a kinematic analysis based on stereographic projection techniques followed by a kinetic analysis by means of the limit equilibrium method.Finally,these two probabilities are combined to provide an overall measure of the probability of failure(PoF)of the bench slope system.The case study is characterized by significant scatter in the geometrical and mechanical properties of the joints.Extensive surface mapping was conducted at 36 different sites following the ISRM suggested procedures.Several direct shear tests were carried out.It is shown that by combining field and laboratory measurements and engineering judgment,the probability density functions(PDF)of the discontinuity parameters can be obtained.These are then used in a Monte Carlo simulation process to compute both kinematic and kinetic probabilities of failure.The overall probability of failure aims to provide the design engineer with a tool to critically evaluate the bench performance from a geotechnical risk perspective and to provide a basis for future bench design optimization.
