Solar flares are a solar activity phenomenon powered by magnetic energy released rapidly through magnetic reconnection. So far the mechanisms for heating the flaring plasma are still under debate. Recently, the researchers from George Mason University, Peking University, etc. discovered that a group of dark tadpole-like downflows, produced during flares, collide with the apexes of flare loops, and strongly heat the surrounding plasma to a higher temperature of 10–20 MK. This discovery also provides a new and alternative explanation for the quasi-periodic pulsations that are often observed in solar and stellar flares.
{"title":"Tadpole-like downflows: A new mechanism for plasma heating in the flaring solar corona","authors":"Leping Li","doi":"10.1360/SSPMA-2021-0053","DOIUrl":"https://doi.org/10.1360/SSPMA-2021-0053","url":null,"abstract":"Solar flares are a solar activity phenomenon powered by magnetic energy released rapidly through magnetic reconnection. So far the mechanisms for heating the flaring plasma are still under debate. Recently, the researchers from George Mason University, Peking University, etc. discovered that a group of dark tadpole-like downflows, produced during flares, collide with the apexes of flare loops, and strongly heat the surrounding plasma to a higher temperature of 10–20 MK. This discovery also provides a new and alternative explanation for the quasi-periodic pulsations that are often observed in solar and stellar flares.","PeriodicalId":44892,"journal":{"name":"Scientia Sinica-Physica Mechanica & Astronomica","volume":"29 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90037184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhipeng Du, Xiaoqiang Zhang, Peng Gao, Ying Li, Lei Zhang
The anti-ship missile warhead must enter the ship’s deep interior in order to achieve the satisfied damage effect. However, the ship’s hull is crisscrossed, which results in far more complex mechanical characteristics of the warhead than that of the parallel target. In order to study the mechanical characteristics of warhead penetrating into the complex structure of a real ship, the complex structure of the ship is simplified as a kind of Z-shaped composite target plate, and the mechanical characteristics of the warhead penetrating into the Z-shaped target plate in a complex attitude are analyzed by using the momentum theorem. Based on the Timoshenko beam theory, the motion equation of the combat part is derived and the theoretical solution is obtained. The attitude change and mechanical properties of warhead penetrating into each stage of Z-shaped target are simulated by LS-DYNA software. The analysis results show that the transverse load of the warhead penetrating Z target is about 2–3 times higher than that of the parallel target, and the movement mode of the warhead is also significantly changed. The Z target can better reflect the complex structural characteristics of the ship than the parallel target, and can provide a reference for the design of the warhead penetration test target. warhead Z-type target plate, mechanical
{"title":"Research on the mechanical characteristics of the Z-type target plate of the warhead entirely penetrating the ship simulation structure","authors":"Zhipeng Du, Xiaoqiang Zhang, Peng Gao, Ying Li, Lei Zhang","doi":"10.1360/sspma-2020-0360","DOIUrl":"https://doi.org/10.1360/sspma-2020-0360","url":null,"abstract":"The anti-ship missile warhead must enter the ship’s deep interior in order to achieve the satisfied damage effect. However, the ship’s hull is crisscrossed, which results in far more complex mechanical characteristics of the warhead than that of the parallel target. In order to study the mechanical characteristics of warhead penetrating into the complex structure of a real ship, the complex structure of the ship is simplified as a kind of Z-shaped composite target plate, and the mechanical characteristics of the warhead penetrating into the Z-shaped target plate in a complex attitude are analyzed by using the momentum theorem. Based on the Timoshenko beam theory, the motion equation of the combat part is derived and the theoretical solution is obtained. The attitude change and mechanical properties of warhead penetrating into each stage of Z-shaped target are simulated by LS-DYNA software. The analysis results show that the transverse load of the warhead penetrating Z target is about 2–3 times higher than that of the parallel target, and the movement mode of the warhead is also significantly changed. The Z target can better reflect the complex structural characteristics of the ship than the parallel target, and can provide a reference for the design of the warhead penetration test target. warhead Z-type target plate, mechanical","PeriodicalId":44892,"journal":{"name":"Scientia Sinica-Physica Mechanica & Astronomica","volume":"86 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86320517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There is no standard specification for targeted design based on the torpedo explosion damage assessment. Existing methods are currently based on ship damage assessments. We analyze the basis for the classification of damage levels of surface ships, which clarified that the design of the damage assessment target should refer to the damage and failure conditions of the ship structure such as different breaks and plastic deformation, and point out the problems around drawing on the current ship damage rating standards in the process of assessing target design. In this work, these issues are resolved through simulation, and the results show that there is complex coupling between underwater explosion loads and typical surface ships. Torpedo explosion damage efficiency is not only related to the physical work of the explosive load on the hull but also to the mode of action of the load and the energy output structure. The damage mode and energy output structure are quite different under different working conditions. The design of the underwater explosion target structure should be carried out based on the damage mode and energy output structure under the corresponding working conditions predicted by the calculation results. According to the characteristics of torpedo explosion damage, an optimized design method for the underwater explosion target structure is proposed. The equivalence of target design damage is verified through simulation. The simulation comparison shows that the design of the target, based on this method, can effectively evaluate the damage of the actual ship by the torpedo. The design process for the torpedo explosion damage target under actual combat conditions is given to provide technical support to the torpedo explosion damage evaluation target design. This method can also provide simulation prediction for torpedo explosion damage test assessments.
{"title":"Targeted design method based on torpedo explosiondamage assessment","authors":"Wensi Liu, Hengdou Tian, SuQiu Cheng","doi":"10.1360/sspma-2020-0361","DOIUrl":"https://doi.org/10.1360/sspma-2020-0361","url":null,"abstract":"There is no standard specification for targeted design based on the torpedo explosion damage assessment. Existing methods are currently based on ship damage assessments. We analyze the basis for the classification of damage levels of surface ships, which clarified that the design of the damage assessment target should refer to the damage and failure conditions of the ship structure such as different breaks and plastic deformation, and point out the problems around drawing on the current ship damage rating standards in the process of assessing target design. In this work, these issues are resolved through simulation, and the results show that there is complex coupling between underwater explosion loads and typical surface ships. Torpedo explosion damage efficiency is not only related to the physical work of the explosive load on the hull but also to the mode of action of the load and the energy output structure. The damage mode and energy output structure are quite different under different working conditions. The design of the underwater explosion target structure should be carried out based on the damage mode and energy output structure under the corresponding working conditions predicted by the calculation results. According to the characteristics of torpedo explosion damage, an optimized design method for the underwater explosion target structure is proposed. The equivalence of target design damage is verified through simulation. The simulation comparison shows that the design of the target, based on this method, can effectively evaluate the damage of the actual ship by the torpedo. The design process for the torpedo explosion damage target under actual combat conditions is given to provide technical support to the torpedo explosion damage evaluation target design. This method can also provide simulation prediction for torpedo explosion damage test assessments.","PeriodicalId":44892,"journal":{"name":"Scientia Sinica-Physica Mechanica & Astronomica","volume":"81 4 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83155720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhou Xinlin, T. Wenwu, Zhu Hui, WU Dan, C. Xiaohong, Zhang Jianli, Zhang Mengfei, Zhang Shaobo, Lei XianHuan, Chen Haolin
{"title":"Detection of magnetic monopoles: History and current status","authors":"Zhou Xinlin, T. Wenwu, Zhu Hui, WU Dan, C. Xiaohong, Zhang Jianli, Zhang Mengfei, Zhang Shaobo, Lei XianHuan, Chen Haolin","doi":"10.1360/sspma-2021-0210","DOIUrl":"https://doi.org/10.1360/sspma-2021-0210","url":null,"abstract":"","PeriodicalId":44892,"journal":{"name":"Scientia Sinica-Physica Mechanica & Astronomica","volume":"22 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90690986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The water jet formed after the collapse of the bubble in the near-field underwater explosion can cause serious damage to the local structure of the ship, and the formation of the jet is asymmetric, which makes it difficult to measure its data in the experiment. At present, studies on the pressure time history curves of the bubble jet in the underwater explosion are still relatively rare. In order to study the characteristics of the jet, the underwater explosion test of 2.5 g TNT explosive at the bottom of fixed square plate at different detonation distances was carried out. First, the accuracy of the test data was verified by the underwater pressure sensor. Second, the image of the whole process from the explosive initiation to the bubble jet generated by the action of the bubble and the steel plate was obtained by high-speed camera. Finally, the time-history curve of water jet pressure was measured by the wall pressure sensor in the center of the steel plate, and another group of wall pressure sensors was set 15 cm away from the center of the steel plate as a control group to ensure that the measured jet data were not clutter. The test data recorded by the underwater sensor show that the error between the shock wave overpressure, the maximum bubble radius of the bubble pulse period and the empirical formula is within 10%. The results recorded by the high-speed camera and wall pressure sensor show that three jets can be observed when the burst distance is 28 cm, but the pressure time history curve is not measured due to the long burst distance. When the burst distances are 15, 17.5 and 20 cm, three jet pressure time history curves are measured. However, due to the short burst distance and the presence of a large number of bubbles between the steel plate and the water surface under the action of the shock wave, it is difficult to observe the test phenomenon with high-speed cameras. The pressure time history curve shows that three jets are generated after the first bubble pulse peak, and the jet pressure can reach 1/4 of the shock wave. The jet appears 1–3 ms after the first
近场水下爆炸气泡破裂后形成的水射流会对船舶局部结构造成严重的破坏，且射流的形成是不对称的，这使得实验中测量其数据变得困难。目前对水下爆炸气泡射流压力时程曲线的研究还比较少。为了研究射流的特性，对2.5 g TNT炸药在固定方板底部进行了不同爆轰距离的水下爆炸试验。首先，通过水下压力传感器验证了试验数据的准确性。其次，利用高速摄像机获得了从爆炸起爆到气泡与钢板相互作用产生气泡射流的整个过程的图像;最后，利用钢板中心的壁压传感器测量水射流压力时程曲线，并将另一组壁压传感器设置在距钢板中心15cm处作为对照组，以保证测量的射流数据不杂乱。水下传感器记录的试验数据表明，冲击波超压、气泡脉冲周期的最大气泡半径与经验公式的误差在10%以内。高速摄像机和壁面压力传感器记录的结果表明，当爆破距离为28 cm时，可以观测到3道射流，但由于爆破距离较长，没有测量到压力时程曲线。在爆破距离为15、17.5和20 cm时，测量了3条射流压力时程曲线。然而，由于在激波作用下钢板与水面之间爆发距离短，且存在大量气泡，使用高速摄像机很难观察到试验现象。压力时程曲线显示，在第一个气泡脉冲峰值后产生三束射流，射流压力可达到激波的1/4。喷射在第一次喷射后1-3毫秒出现
{"title":"Research on bubble jet of underwater explosion at the bottom of fixed square plate","authors":"J. Qin, Wen Yanbo, Xiangyao Meng, Ruiyuan Huang","doi":"10.1360/sspma-2020-0379","DOIUrl":"https://doi.org/10.1360/sspma-2020-0379","url":null,"abstract":"The water jet formed after the collapse of the bubble in the near-field underwater explosion can cause serious damage to the local structure of the ship, and the formation of the jet is asymmetric, which makes it difficult to measure its data in the experiment. At present, studies on the pressure time history curves of the bubble jet in the underwater explosion are still relatively rare. In order to study the characteristics of the jet, the underwater explosion test of 2.5 g TNT explosive at the bottom of fixed square plate at different detonation distances was carried out. First, the accuracy of the test data was verified by the underwater pressure sensor. Second, the image of the whole process from the explosive initiation to the bubble jet generated by the action of the bubble and the steel plate was obtained by high-speed camera. Finally, the time-history curve of water jet pressure was measured by the wall pressure sensor in the center of the steel plate, and another group of wall pressure sensors was set 15 cm away from the center of the steel plate as a control group to ensure that the measured jet data were not clutter. The test data recorded by the underwater sensor show that the error between the shock wave overpressure, the maximum bubble radius of the bubble pulse period and the empirical formula is within 10%. The results recorded by the high-speed camera and wall pressure sensor show that three jets can be observed when the burst distance is 28 cm, but the pressure time history curve is not measured due to the long burst distance. When the burst distances are 15, 17.5 and 20 cm, three jet pressure time history curves are measured. However, due to the short burst distance and the presence of a large number of bubbles between the steel plate and the water surface under the action of the shock wave, it is difficult to observe the test phenomenon with high-speed cameras. The pressure time history curve shows that three jets are generated after the first bubble pulse peak, and the jet pressure can reach 1/4 of the shock wave. The jet appears 1–3 ms after the first","PeriodicalId":44892,"journal":{"name":"Scientia Sinica-Physica Mechanica & Astronomica","volume":"1 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82922563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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