Annular grooved projectiles(AGPs)have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates.They could become embedded solidly in the target surface dur...Annular grooved projectiles(AGPs)have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates.They could become embedded solidly in the target surface during low-velocity impact.In this investigation,the firm embedding behavior of AGP was observed by impact experiments.Corresponding numerical simulations provided a better understanding of this process.Experimental and numerical results indicated that the firm embedding behavior of AGP was mainly due to the filling-material in the groove rather than the friction between the projectile and target,unlike traditional shape such as conical projectile.According to observation,firm embedding process can generally be subdivided into four stages:initial-cratering stage,groove-filling stage,fillingmaterial failure stage and rebound vibration stage.Moreover,the damage mechanics of target material around crater was obtained through microscopic tests.A comparison of the cross-sectional figures between the experiment and simulation proved that the analysis and the proposed method were reasonable and feasible,which further demonstrated that the firm embedding behavior has application potential in new concept warheads.展开更多
The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical m...The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical method based on computational fluid mechanics(CFD).The transient aerodynamic behaviors when opening door under various flight altitudes and the corresponding structure deformation evolution in the unsteady flow fields are analyzed respectively and presented.The rules of aircraft attitude parameters′impacting to the responses of structure and the bay-door′s opening process are obtained by comparing with the analysis results.These rules can be applied to the structure design of bay-door and route specification of missile when disengaged and launched from within store.展开更多
当前的位置预测方法大多没有考虑到用户行为信息,由于用户的访问时间、行为模式等能够在很大程度上反映所处位置,因此在对位置潜在向量进行预训练时有必要使用该信息。进行位置预测时,采样粒度较细的序列长度较长,难以捕获长距离依赖。...当前的位置预测方法大多没有考虑到用户行为信息,由于用户的访问时间、行为模式等能够在很大程度上反映所处位置,因此在对位置潜在向量进行预训练时有必要使用该信息。进行位置预测时,采样粒度较细的序列长度较长,难以捕获长距离依赖。针对这2个问题,提出了基于用户行为和上下文语义的分层时空长短期记忆网络(Hierarchical Spatiotemporal Long Short-Term Memory Based on User Behavior and Contextual Semantics,CHST-LSTM)模型。该模型通过Transformer编码层处理轨迹数据,将用户相关行为信息考虑在内,融合位置的上下文语义信息,通过预训练得到位置的嵌入表征。根据用户的行为状态分割轨迹阶段,采用编码器-解码器方式对ST-LSTM进行分段分层扩展,利用BiLSTM对全局信息建模,同时处理轨迹的长短期变化,解决长序列的长距离依赖问题。对外卖员用户群体的真实移动轨迹数据进行分析和实验,通过聚类发现其特有的工作模式,在预训练时加入工作模式信息与到访时间信息,得到位置的特征向量并用于预测模型。结果表明CHST-LSTM模型在预测用户下一位置时精度更高。展开更多
Experimental and theoretical studies of drag embedment plate anchors recently carried out in Tianjin University are summarized in this research paper, which involve a series of important topics relevant to the study o...Experimental and theoretical studies of drag embedment plate anchors recently carried out in Tianjin University are summarized in this research paper, which involve a series of important topics relevant to the study of drag anchors. The techniques for measuring the trajectory and movement direction of drag anchors in soils, the techniques for measuring the moving embedment point and reverse eatenary shape of the embedded drag line, the penetration mechanism and kinematic behavior of drag anchors, the ultimate embedment depth of drag anchors, the movement direction of the anchor with an arbitrary fluke section, the reverse catenary properties of the embedded drag line, the interaetional properties between drag anchor and installation line, the kinematic model of drag anchors in seabed soils, and the analytical method for predicting the anchor trajectory in soils will all be examined. The present work remarkably reduces the uncertainties in design and analysis of drag embedment plate anchors, and is beneficial to improving the application of this new type of drag anchor in offshore engineering.展开更多
In this paper,the cracking and mechanical responses are studied for the Polymethylmethacrylate(PMMA)sample with two three-dimensional embedded coplanar elliptic flaws subjected to uniaxial compression.The experimental...In this paper,the cracking and mechanical responses are studied for the Polymethylmethacrylate(PMMA)sample with two three-dimensional embedded coplanar elliptic flaws subjected to uniaxial compression.The experimental results indicate that both the peak stress and crack initiation stress first decrease and then increase with increasing flaw angle,and they increase linearly with increasing flaw spacing.Moreover,five crack modes occur in these tested samples,including the coplanar secondary cracks,wing cracks,petal cracks,anti-wing cracks,and vertical giant cracks.The growth length of wing cracks is approximately equal to the length of the long axis of preexisting flaw.However,the maximum width is roughly equal to half the length of the long axis of pre-existing elliptic flaw.The final failure modes include the splitting failure induced by wing cracks and vertical giant cracks,and the mixed tensile-shear failure induced by coplanar secondary cracks and wing cracks.展开更多
基金financially supported by the National Natural Science Foundation of China [grant number 11472053]
文摘Annular grooved projectiles(AGPs)have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates.They could become embedded solidly in the target surface during low-velocity impact.In this investigation,the firm embedding behavior of AGP was observed by impact experiments.Corresponding numerical simulations provided a better understanding of this process.Experimental and numerical results indicated that the firm embedding behavior of AGP was mainly due to the filling-material in the groove rather than the friction between the projectile and target,unlike traditional shape such as conical projectile.According to observation,firm embedding process can generally be subdivided into four stages:initial-cratering stage,groove-filling stage,fillingmaterial failure stage and rebound vibration stage.Moreover,the damage mechanics of target material around crater was obtained through microscopic tests.A comparison of the cross-sectional figures between the experiment and simulation proved that the analysis and the proposed method were reasonable and feasible,which further demonstrated that the firm embedding behavior has application potential in new concept warheads.
文摘The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical method based on computational fluid mechanics(CFD).The transient aerodynamic behaviors when opening door under various flight altitudes and the corresponding structure deformation evolution in the unsteady flow fields are analyzed respectively and presented.The rules of aircraft attitude parameters′impacting to the responses of structure and the bay-door′s opening process are obtained by comparing with the analysis results.These rules can be applied to the structure design of bay-door and route specification of missile when disengaged and launched from within store.
文摘当前的位置预测方法大多没有考虑到用户行为信息,由于用户的访问时间、行为模式等能够在很大程度上反映所处位置,因此在对位置潜在向量进行预训练时有必要使用该信息。进行位置预测时,采样粒度较细的序列长度较长,难以捕获长距离依赖。针对这2个问题,提出了基于用户行为和上下文语义的分层时空长短期记忆网络(Hierarchical Spatiotemporal Long Short-Term Memory Based on User Behavior and Contextual Semantics,CHST-LSTM)模型。该模型通过Transformer编码层处理轨迹数据,将用户相关行为信息考虑在内,融合位置的上下文语义信息,通过预训练得到位置的嵌入表征。根据用户的行为状态分割轨迹阶段,采用编码器-解码器方式对ST-LSTM进行分段分层扩展,利用BiLSTM对全局信息建模,同时处理轨迹的长短期变化,解决长序列的长距离依赖问题。对外卖员用户群体的真实移动轨迹数据进行分析和实验,通过聚类发现其特有的工作模式,在预训练时加入工作模式信息与到访时间信息,得到位置的特征向量并用于预测模型。结果表明CHST-LSTM模型在预测用户下一位置时精度更高。
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant nos. 50639030 and 50979070） and the 863 Program of China （Grant no. 2006AA09Z348）.
文摘Experimental and theoretical studies of drag embedment plate anchors recently carried out in Tianjin University are summarized in this research paper, which involve a series of important topics relevant to the study of drag anchors. The techniques for measuring the trajectory and movement direction of drag anchors in soils, the techniques for measuring the moving embedment point and reverse eatenary shape of the embedded drag line, the penetration mechanism and kinematic behavior of drag anchors, the ultimate embedment depth of drag anchors, the movement direction of the anchor with an arbitrary fluke section, the reverse catenary properties of the embedded drag line, the interaetional properties between drag anchor and installation line, the kinematic model of drag anchors in seabed soils, and the analytical method for predicting the anchor trajectory in soils will all be examined. The present work remarkably reduces the uncertainties in design and analysis of drag embedment plate anchors, and is beneficial to improving the application of this new type of drag anchor in offshore engineering.
基金supported by National Natural Science Foundation of China(Grant Nos.51839009,41807251 and 51679017).
文摘In this paper,the cracking and mechanical responses are studied for the Polymethylmethacrylate(PMMA)sample with two three-dimensional embedded coplanar elliptic flaws subjected to uniaxial compression.The experimental results indicate that both the peak stress and crack initiation stress first decrease and then increase with increasing flaw angle,and they increase linearly with increasing flaw spacing.Moreover,five crack modes occur in these tested samples,including the coplanar secondary cracks,wing cracks,petal cracks,anti-wing cracks,and vertical giant cracks.The growth length of wing cracks is approximately equal to the length of the long axis of preexisting flaw.However,the maximum width is roughly equal to half the length of the long axis of pre-existing elliptic flaw.The final failure modes include the splitting failure induced by wing cracks and vertical giant cracks,and the mixed tensile-shear failure induced by coplanar secondary cracks and wing cracks.
