Background The redirected walking(RDW)method for multi-user collaboration requires maintaining the relative position between users in a virtual environment(VE)and physical environment(PE).A chasing game in a VE is a t...Background The redirected walking(RDW)method for multi-user collaboration requires maintaining the relative position between users in a virtual environment(VE)and physical environment(PE).A chasing game in a VE is a typical virtual reality game that entails multi-user collaboration.When a user approaches and interacts with a target user in the VE,the user is expected to approach and interact with the target user in the corresponding PE as well.Existing methods of multi-user RDW mainly focus on obstacle avoidance,which does not account for the relative positional relationship between the users in both VE and PE.Methods To enhance the user experience and facilitate potential interaction,this paper presents a novel dynamic alignment algorithm for multi-user collaborative redirected walking(DA-RDW)in a shared PE where the target user and other users are moving.This algorithm adopts improved artificial potential fields,where the repulsive force is a function of the relative position and velocity of the user with respect to dynamic obstacles.For the best alignment,this algorithm sets the alignment-guidance force in several cases and then converts it into a constrained optimization problem to obtain the optimal direction.Moreover,this algorithm introduces a potential interaction object selection strategy for a dynamically uncertain environment to speed up the subsequent alignment.To balance obstacle avoidance and alignment,this algorithm uses the dynamic weightings of the virtual and physical distances between users and the target to determine the resultant force vector.Results The efficacy of the proposed method was evaluated using a series of simulations and live-user experiments.The experimental results demonstrate that our novel dynamic alignment method for multi-user collaborative redirected walking can reduce the distance error in both VE and PE to improve alignment with fewer collisions.展开更多
Background The redirected jumping(RDJ)technique is a new locomotion method that saves physical tracking area and enhances the body movement experience of users in virtual reality.In a previous study,the range of imper...Background The redirected jumping(RDJ)technique is a new locomotion method that saves physical tracking area and enhances the body movement experience of users in virtual reality.In a previous study,the range of imperceptible manipulation gains in RDJ was discussed in an empty virtual environment(VE).Methods In this study,we conducted three tasks to investigate the influence of alley width on the detection threshold of jump redirection in a VE.Results The results demonstrated that the imperceptible distance gain range in RDJ was not associated with the width of the alleys.The imperceptible height and rotation gain ranges in RDJ are related to the width of the alleys.Conclusions We preliminarily summarized the relationship between the occlusion distance and manipulation range of the three gains in a complex environment.Simultaneously,the guiding principle for choosing three gains in RDJ according to the occlusion distance in a complex environment is provided.展开更多
Background Redirected jumping(RDJ)allows users to explore virtual environments(VEs)naturally by scaling a small real-world jump to a larger virtual jump with virtual camera motion manipulation,thereby addressing the p...Background Redirected jumping(RDJ)allows users to explore virtual environments(VEs)naturally by scaling a small real-world jump to a larger virtual jump with virtual camera motion manipulation,thereby addressing the problem of limited physical space in VR applications.Previous RDJ studies have mainly focused on detection threshold estimation.However,the effect VE or self representation(SR)has on the perception or performance of RDJs remains unclear.Methods In this paper,we report experiments to measure the perception(detection thresholds for gains,presence,embodiment,intrinsic motivation,and cybersickness)and physical performance(heart rate intensity,preparation time,and actual jumping distance)of redirected forward jumping under six different combinations of VE(low and high visual richness)and SRs(invisible,shoes,and human-like).Results Our results indicated that the detection threshold ranges for horizontal translation gains were significantly smaller in the VE with high rather than low visual richness.When different SRs were applied,our results did not suggest significant differences in detection thresholds,but it did report longer actual jumping distances in the invisible body case compared with the other two SRs.In the high visual richness VE,the preparation time for jumping with a human-like avatar was significantly longer than that with other SRs.Finally,some correlations were found between perception and physical performance measures.Conclusions All these findings suggest that both VE and SRs influence users'perception and performance in RDJ and must be considered when designing locomotion techniques.展开更多
Background: Mesh expansion and fixation at retro-rectus plane through multiples stabs produces good results. But these stabs cause cosmetic disorders for the patients and doctors. So, we find some modification to do t...Background: Mesh expansion and fixation at retro-rectus plane through multiples stabs produces good results. But these stabs cause cosmetic disorders for the patients and doctors. So, we find some modification to do this procedure without these stabbing wounds in midline hernial repair. Patients and methods: This technique was used to fix the mesh at retro-rectus plane in 50 patients suffering from midline hernias, from January 2008 through January 2010 at Zagazig university Hospital, Egypt. Laparotomy incision was done over the hernial sac or at old incision;the contents were then released and reduced into peritoneal cavity without much subcutaneous dissection. The suitable sheet of polypropylene mesh to cover the hernial defect and any weak area was prepared and fixed at retro-rectus plane percutaneously without stabbing wounds by using redirecting suture hook. The mean period of follow up was 26 months. Results: There was no recurrence during the period of follow up. Five patients developed subcutaneous bluish discoloration at the site of some stitches, which disappear within two weeks with conservative treatment. Conclusion: Percutaneous mesh expansion and fixation at retro-rectus plane by using redirecting suture hook procedure has good results in recurrence rate and cosmetic appearance.展开更多
Locomotion is a fundamental interaction technique that allows free navigation in virtual scenes.A large body of literature has demonstrated that natural locomotion experience can significantly improve the sense of pre...Locomotion is a fundamental interaction technique that allows free navigation in virtual scenes.A large body of literature has demonstrated that natural locomotion experience can significantly improve the sense of presence and help users achieve better performance in tasks such as searching and training.In the upcoming metaverse era,locomotion will play a critical role in the success of large-scale interactive applications.Perception and redirection are two tightly connected problems in virtual locomotion.Given a limited physical condition and a target virtual scene,how to make the perceived locomotion as natural as possible,and further unknowingly redirect the user in the physical world is an open question.In this special issue,we have selected five papers that provide their latest updates for research problems of view control,virtual jumping,climbing,and searching.展开更多
Monensin,a polyether ionophore antibiotic produced by Streptomyces cinnamonensis,exhibits notable anticoccidial and antitumor properties.In this study,a fatty acid addition(FAA)strategy significantly enhanced the mone...Monensin,a polyether ionophore antibiotic produced by Streptomyces cinnamonensis,exhibits notable anticoccidial and antitumor properties.In this study,a fatty acid addition(FAA)strategy significantly enhanced the monensin production capability of S.cinnamonensis,resulting in an unprecedented monensin titer of 17.72 g/L at 192 h,7.36 times that of the control.Physiological assay showed the FAA markedly altered the cellular morphology,cell membrane fluidity,enzymatic activity and intracellular cofactors,thus indicating of an increased carbon flux.With transcriptional analysis at the product biosynthesis phase,4 genes in the monensin biosynthesis cluster and 11 genes related to the oxidative stress response were observed to be upregulated.Meanwhile,genes consisting of two sugar transport systems were downregulated.For the precursors supply,genes associated with triacylglycerols(TAG)degradation(lps)and fatty acid degradation genes(fadE,fadB,fadA)were upregulated,while genes to TAG synthesis were downregulated.For the monensin synthetic pathway,8 polyketide synthase genes,9 modifier genes and 3 pathway-specific regulatory genes within the monensin biosynthetic gene cluster(mon)were upregulated.Consequently,the physiological and transcriptional response of S.cinnamonensis to the FAA strategy was correlated well with the monensin biosynthesis.The findings not only elucidated the de novo biosynthesis of monensin via FAA,but also offered a strategic framework for efficient production of polyketide natural products.展开更多
As the virtual reality(VR)technology strives to provide immersive and natural user experiences,the challenge of aligning vast virtual environments with limited physical spaces remains significant.This survey comprehen...As the virtual reality(VR)technology strives to provide immersive and natural user experiences,the challenge of aligning vast virtual environments with limited physical spaces remains significant.This survey comprehensively explores the advancements in redirected walking(RDW)techniques aimed at overcoming spatial constraints in VR.RDW addresses this by subtly manipulating users’physical movements to allow for seamless navigation within constrained areas.The survey delves into gain perception mechanisms,detailing how slight discrepancies between virtual and real-world movements can be utilized without user awareness,thus extending the effective navigable space.Various RDW control algorithms for gain-based RDW are analyzed,highlighting their implementation and effectiveness in maintaining immersion and minimizing perceptual disturbances.Furthermore,novel methods extending beyond traditional gain-based techniques are discussed,showcasing innovative approaches that further refine VR interactions.The practical implications of RDW in enhancing safety and reducing physical collisions in VR environments are underscored,alongside its potential to improve user experience by aligning virtual exploration more closely with natural human behavior patterns.Through a thorough review of existing literature and recent advancements,this survey provides a systematic understanding for researchers,developers,and industry professionals.It underscores the importance of RDW in the future of VR,emphasizing RDW's role in making VR more accessible and practical across various applications,from education and training to therapy and entertainment.The paper concludes with a forward-looking perspective on the continued evolution and potential of RDW in revolutionizing virtual reality experiences.展开更多
T cell-redirecting bispecific antibodies are specifically designed to bind to tumor-associated antigens,thereby engaging with CD3 on the T cell receptor.This linkage between tumor cells and T cells actively triggers T...T cell-redirecting bispecific antibodies are specifically designed to bind to tumor-associated antigens,thereby engaging with CD3 on the T cell receptor.This linkage between tumor cells and T cells actively triggers T cell activation and initiates targeted killing of the identified tumor cells.These antibodies have emerged as one of the most promising avenues within tumor immunotherapy.However,despite success in treating hematological malignancies,significant advancements in solid tumors have yet to be explored.In this review,we aim to address the critical challenges associated with T cellredirecting bispecific antibodies and explore novel strategies to overcome these obstacles,with the ultimate goal of expanding the application of this therapy to include solid tumors.展开更多
Asteroids may contain valuable minerals.A method to exploit asteroid mines is to transfer them closer to the Earth for further mining processes.In this work,we optimally mount a set of fixed-angle spacecraft thrusters...Asteroids may contain valuable minerals.A method to exploit asteroid mines is to transfer them closer to the Earth for further mining processes.In this work,we optimally mount a set of fixed-angle spacecraft thrusters on the surface of an asteroid to conduct concurrent detumbling and redirecting to the desired orbit.The optimization objective reconciles the minimum duration of the mission with the minimum required fuel as well as the maximum uniformity of the fuel distribution required for all thrusters.Each thruster can respond to redirection and detumbling commands simultaneously.Redirection and detumbling are performed via the directional adaptive guidance method and PID controllers,respectively,and the weight factors for each orbital element and the gains of the rotational control channels are also optimized in the process.We use the particle swarm optimization algorithm to evaluate the objective function by simulating the entire mission to find the optimal design.The rotational control damps the tumbling of the asteroid without interfering with the simultaneous redirection process and eventually fixes the asteroid in the optimally selected orientation in the inertial reference frame.The rotational velocity and attitude of the asteroid are controlled via separate PID controllers,which are set robustly.We can effectively optimize the mission by collectively tuning both the system’s rotational and redirection behaviors as well as the thrusters’configuration and optimally selecting the final attitude of the asteroid.展开更多
Virtual reality(VR)allows users to explore and experience a computer-simulated virtual environment so that VR users can be immersed in a totally artificial virtual world and interact with arbitrary virtual objects.How...Virtual reality(VR)allows users to explore and experience a computer-simulated virtual environment so that VR users can be immersed in a totally artificial virtual world and interact with arbitrary virtual objects.However,the limited physical tracking space usually restricts the exploration of large virtual spaces,and VR users have to use special locomotion techniques to move from one location to another.Among these techniques,redirected walking(RDW)is one of the most natural locomotion techniques to solve the problem based on near-natural walking experiences.The core idea of the RDW technique is to imperceptibly guide users on virtual paths,which might vary from the paths they physically walk in the real world.In a similar way,some RDW algorithms imperceptibly change the structure and layout of the virtual environment such that the virtual environment fits into the tracking space.In this survey,we first present a taxonomy of existing RDW work.Based on this taxonomy,we compare and analyze both contributions and shortcomings of the existing methods in detail,and find view manipulation methods offer satisfactory visual effect but the experience can be interrupted when users reach the physical boundaries,while virtual environment manipulation methods can provide users with consistent movement but have limited application scenarios.Finally,we discuss possible future research directions,indicating combining artificial intelligence with this area will be effective and intriguing.展开更多
Honeypot is a recent developed computer security concept which uses active offense to against attacks from hackers . It lures hackers to attack a seemly vulnerable fake network where they could be well observed in ord...Honeypot is a recent developed computer security concept which uses active offense to against attacks from hackers . It lures hackers to attack a seemly vulnerable fake network where they could be well observed in order to learn about the tactics and tools used by the attackers, so that we may improve the system security accordingly later. In this paper, we propose a novel approach for redirecting technique in honeypot system. First, we introduce briefly concepts of the honeypot system. Then we describe a redirection technique and an implementation algorithm. Finally, using the IDS Snort and the firewall IPTable, we set up a testing environment and give some simulations results. We also discuss some future research topics.展开更多
Novel biologics that redirect cytotoxic T lymphocytes （CTLs） to kill tumor cells bearing a tumor associated antigen hold great promise in the clinic. However, the ability to safely and potently target CD3 on CTL tow...Novel biologics that redirect cytotoxic T lymphocytes （CTLs） to kill tumor cells bearing a tumor associated antigen hold great promise in the clinic. However, the ability to safely and potently target CD3 on CTL toward tumor associated antigens （TAA） expressed on tumor cells remains a challenge of both technology and biol- ogy. Herein we describe the use of a Half DVD-Ig format that can redirect CTL to kill tumor cells. Notably, Half DVD-Ig molecules that are monovalent for each speci- ficity demonstrated reduced non-specific CTL activation and conditional CTL activation upon binding to TAA compared to intact tetravalent DVD-Ig molecules that are bivalent for each specificity, while maintaining good drug like properties and appropriate PK properties.展开更多
研究小行星的暴露年龄对于理解其形成与演化具有重要意义。双小行星重定向测试(Double Asteroid Redirection Test,DART)任务的实施,不仅验证了动能撞击技术偏转近地小行星轨道的可行性,也为研究小行星暴露年龄及其成因演化提供了宝贵...研究小行星的暴露年龄对于理解其形成与演化具有重要意义。双小行星重定向测试(Double Asteroid Redirection Test,DART)任务的实施,不仅验证了动能撞击技术偏转近地小行星轨道的可行性,也为研究小行星暴露年龄及其成因演化提供了宝贵机会。基于DART撞击前后地基望远镜获得的可见近红外光谱数据,对主星Didymos表面及次星Dimorphos溅射物开展暴露年龄研究。结果表明,Didymos表面的暴露年龄约为45.7万年,表明主星在约45.7万年前发生了一次较大规模的物质脱落事件。该事件对主星的表面年龄几乎没有影响,但重置了次星的表面年龄及主星的暴露年龄。Dimorphos溅射物与主星Didymos的表面成分相同,但风化程度较低,这表明在次星形成后,主星和次星表面受到强烈的太空风化作用,而次星内部物质受到的太空风化作用相对较弱。展开更多
基金Supported by STI 2030 Major Projects of China(2021ZD0200400).
文摘Background The redirected walking(RDW)method for multi-user collaboration requires maintaining the relative position between users in a virtual environment(VE)and physical environment(PE).A chasing game in a VE is a typical virtual reality game that entails multi-user collaboration.When a user approaches and interacts with a target user in the VE,the user is expected to approach and interact with the target user in the corresponding PE as well.Existing methods of multi-user RDW mainly focus on obstacle avoidance,which does not account for the relative positional relationship between the users in both VE and PE.Methods To enhance the user experience and facilitate potential interaction,this paper presents a novel dynamic alignment algorithm for multi-user collaborative redirected walking(DA-RDW)in a shared PE where the target user and other users are moving.This algorithm adopts improved artificial potential fields,where the repulsive force is a function of the relative position and velocity of the user with respect to dynamic obstacles.For the best alignment,this algorithm sets the alignment-guidance force in several cases and then converts it into a constrained optimization problem to obtain the optimal direction.Moreover,this algorithm introduces a potential interaction object selection strategy for a dynamically uncertain environment to speed up the subsequent alignment.To balance obstacle avoidance and alignment,this algorithm uses the dynamic weightings of the virtual and physical distances between users and the target to determine the resultant force vector.Results The efficacy of the proposed method was evaluated using a series of simulations and live-user experiments.The experimental results demonstrate that our novel dynamic alignment method for multi-user collaborative redirected walking can reduce the distance error in both VE and PE to improve alignment with fewer collisions.
基金the National Natural Science Foundation of China(619320061772051).
文摘Background The redirected jumping(RDJ)technique is a new locomotion method that saves physical tracking area and enhances the body movement experience of users in virtual reality.In a previous study,the range of imperceptible manipulation gains in RDJ was discussed in an empty virtual environment(VE).Methods In this study,we conducted three tasks to investigate the influence of alley width on the detection threshold of jump redirection in a VE.Results The results demonstrated that the imperceptible distance gain range in RDJ was not associated with the width of the alleys.The imperceptible height and rotation gain ranges in RDJ are related to the width of the alleys.Conclusions We preliminarily summarized the relationship between the occlusion distance and manipulation range of the three gains in a complex environment.Simultaneously,the guiding principle for choosing three gains in RDJ according to the occlusion distance in a complex environment is provided.
基金the National Natural Science Foundation of China(61902012)the Young Talents Support Project of China Association for Science and Technology.
文摘Background Redirected jumping(RDJ)allows users to explore virtual environments(VEs)naturally by scaling a small real-world jump to a larger virtual jump with virtual camera motion manipulation,thereby addressing the problem of limited physical space in VR applications.Previous RDJ studies have mainly focused on detection threshold estimation.However,the effect VE or self representation(SR)has on the perception or performance of RDJs remains unclear.Methods In this paper,we report experiments to measure the perception(detection thresholds for gains,presence,embodiment,intrinsic motivation,and cybersickness)and physical performance(heart rate intensity,preparation time,and actual jumping distance)of redirected forward jumping under six different combinations of VE(low and high visual richness)and SRs(invisible,shoes,and human-like).Results Our results indicated that the detection threshold ranges for horizontal translation gains were significantly smaller in the VE with high rather than low visual richness.When different SRs were applied,our results did not suggest significant differences in detection thresholds,but it did report longer actual jumping distances in the invisible body case compared with the other two SRs.In the high visual richness VE,the preparation time for jumping with a human-like avatar was significantly longer than that with other SRs.Finally,some correlations were found between perception and physical performance measures.Conclusions All these findings suggest that both VE and SRs influence users'perception and performance in RDJ and must be considered when designing locomotion techniques.
文摘Background: Mesh expansion and fixation at retro-rectus plane through multiples stabs produces good results. But these stabs cause cosmetic disorders for the patients and doctors. So, we find some modification to do this procedure without these stabbing wounds in midline hernial repair. Patients and methods: This technique was used to fix the mesh at retro-rectus plane in 50 patients suffering from midline hernias, from January 2008 through January 2010 at Zagazig university Hospital, Egypt. Laparotomy incision was done over the hernial sac or at old incision;the contents were then released and reduced into peritoneal cavity without much subcutaneous dissection. The suitable sheet of polypropylene mesh to cover the hernial defect and any weak area was prepared and fixed at retro-rectus plane percutaneously without stabbing wounds by using redirecting suture hook. The mean period of follow up was 26 months. Results: There was no recurrence during the period of follow up. Five patients developed subcutaneous bluish discoloration at the site of some stitches, which disappear within two weeks with conservative treatment. Conclusion: Percutaneous mesh expansion and fixation at retro-rectus plane by using redirecting suture hook procedure has good results in recurrence rate and cosmetic appearance.
文摘Locomotion is a fundamental interaction technique that allows free navigation in virtual scenes.A large body of literature has demonstrated that natural locomotion experience can significantly improve the sense of presence and help users achieve better performance in tasks such as searching and training.In the upcoming metaverse era,locomotion will play a critical role in the success of large-scale interactive applications.Perception and redirection are two tightly connected problems in virtual locomotion.Given a limited physical condition and a target virtual scene,how to make the perceived locomotion as natural as possible,and further unknowingly redirect the user in the physical world is an open question.In this special issue,we have selected five papers that provide their latest updates for research problems of view control,virtual jumping,climbing,and searching.
基金funded by the National Natural Science Foundation of China(21776114)the National First-class Discipline Program of Light Industry Technology and Engineering of China(QGJC20230203)+1 种基金the 111 Project of MOE(China)(111-2-06)the Postgraduate Research and Practice Innovation Program of Jiangsu Province(China)(KYCX22-2377).
文摘Monensin,a polyether ionophore antibiotic produced by Streptomyces cinnamonensis,exhibits notable anticoccidial and antitumor properties.In this study,a fatty acid addition(FAA)strategy significantly enhanced the monensin production capability of S.cinnamonensis,resulting in an unprecedented monensin titer of 17.72 g/L at 192 h,7.36 times that of the control.Physiological assay showed the FAA markedly altered the cellular morphology,cell membrane fluidity,enzymatic activity and intracellular cofactors,thus indicating of an increased carbon flux.With transcriptional analysis at the product biosynthesis phase,4 genes in the monensin biosynthesis cluster and 11 genes related to the oxidative stress response were observed to be upregulated.Meanwhile,genes consisting of two sugar transport systems were downregulated.For the precursors supply,genes associated with triacylglycerols(TAG)degradation(lps)and fatty acid degradation genes(fadE,fadB,fadA)were upregulated,while genes to TAG synthesis were downregulated.For the monensin synthetic pathway,8 polyketide synthase genes,9 modifier genes and 3 pathway-specific regulatory genes within the monensin biosynthetic gene cluster(mon)were upregulated.Consequently,the physiological and transcriptional response of S.cinnamonensis to the FAA strategy was correlated well with the monensin biosynthesis.The findings not only elucidated the de novo biosynthesis of monensin via FAA,but also offered a strategic framework for efficient production of polyketide natural products.
基金supported by the National Key Research and Development Program of China under Grant No.2023YFF0905104the National Natural Science Foundation of China under Grant No.62361146854Tsinghua-Tencent Joint Laboratory for Internet Innovation Technology.
文摘As the virtual reality(VR)technology strives to provide immersive and natural user experiences,the challenge of aligning vast virtual environments with limited physical spaces remains significant.This survey comprehensively explores the advancements in redirected walking(RDW)techniques aimed at overcoming spatial constraints in VR.RDW addresses this by subtly manipulating users’physical movements to allow for seamless navigation within constrained areas.The survey delves into gain perception mechanisms,detailing how slight discrepancies between virtual and real-world movements can be utilized without user awareness,thus extending the effective navigable space.Various RDW control algorithms for gain-based RDW are analyzed,highlighting their implementation and effectiveness in maintaining immersion and minimizing perceptual disturbances.Furthermore,novel methods extending beyond traditional gain-based techniques are discussed,showcasing innovative approaches that further refine VR interactions.The practical implications of RDW in enhancing safety and reducing physical collisions in VR environments are underscored,alongside its potential to improve user experience by aligning virtual exploration more closely with natural human behavior patterns.Through a thorough review of existing literature and recent advancements,this survey provides a systematic understanding for researchers,developers,and industry professionals.It underscores the importance of RDW in the future of VR,emphasizing RDW's role in making VR more accessible and practical across various applications,from education and training to therapy and entertainment.The paper concludes with a forward-looking perspective on the continued evolution and potential of RDW in revolutionizing virtual reality experiences.
基金supported by the National Natural Science Foundation of China(Nos.32070940 and 81991491)the China Postdoctoral Science Foundation(No.2021M700115)+2 种基金the Postdoctoral Innovation Talents Support Program(No.BX20220189,China)the Science and Technology Planning Project of Fujian Province(No.2022L3080,China)the CAMS Innovation Fund for Medical Sciences(No.2019RU022,China).
文摘T cell-redirecting bispecific antibodies are specifically designed to bind to tumor-associated antigens,thereby engaging with CD3 on the T cell receptor.This linkage between tumor cells and T cells actively triggers T cell activation and initiates targeted killing of the identified tumor cells.These antibodies have emerged as one of the most promising avenues within tumor immunotherapy.However,despite success in treating hematological malignancies,significant advancements in solid tumors have yet to be explored.In this review,we aim to address the critical challenges associated with T cellredirecting bispecific antibodies and explore novel strategies to overcome these obstacles,with the ultimate goal of expanding the application of this therapy to include solid tumors.
文摘Asteroids may contain valuable minerals.A method to exploit asteroid mines is to transfer them closer to the Earth for further mining processes.In this work,we optimally mount a set of fixed-angle spacecraft thrusters on the surface of an asteroid to conduct concurrent detumbling and redirecting to the desired orbit.The optimization objective reconciles the minimum duration of the mission with the minimum required fuel as well as the maximum uniformity of the fuel distribution required for all thrusters.Each thruster can respond to redirection and detumbling commands simultaneously.Redirection and detumbling are performed via the directional adaptive guidance method and PID controllers,respectively,and the weight factors for each orbital element and the gains of the rotational control channels are also optimized in the process.We use the particle swarm optimization algorithm to evaluate the objective function by simulating the entire mission to find the optimal design.The rotational control damps the tumbling of the asteroid without interfering with the simultaneous redirection process and eventually fixes the asteroid in the optimally selected orientation in the inertial reference frame.The rotational velocity and attitude of the asteroid are controlled via separate PID controllers,which are set robustly.We can effectively optimize the mission by collectively tuning both the system’s rotational and redirection behaviors as well as the thrusters’configuration and optimally selecting the final attitude of the asteroid.
基金the National Natural Science Foundation of China under Grant Nos.61902012 and 61932003Frank Steinicke was supported by funds from the BMBF,BMWi,DFG,and EU.
文摘Virtual reality(VR)allows users to explore and experience a computer-simulated virtual environment so that VR users can be immersed in a totally artificial virtual world and interact with arbitrary virtual objects.However,the limited physical tracking space usually restricts the exploration of large virtual spaces,and VR users have to use special locomotion techniques to move from one location to another.Among these techniques,redirected walking(RDW)is one of the most natural locomotion techniques to solve the problem based on near-natural walking experiences.The core idea of the RDW technique is to imperceptibly guide users on virtual paths,which might vary from the paths they physically walk in the real world.In a similar way,some RDW algorithms imperceptibly change the structure and layout of the virtual environment such that the virtual environment fits into the tracking space.In this survey,we first present a taxonomy of existing RDW work.Based on this taxonomy,we compare and analyze both contributions and shortcomings of the existing methods in detail,and find view manipulation methods offer satisfactory visual effect but the experience can be interrupted when users reach the physical boundaries,while virtual environment manipulation methods can provide users with consistent movement but have limited application scenarios.Finally,we discuss possible future research directions,indicating combining artificial intelligence with this area will be effective and intriguing.
基金This workis supported by Natural Science Foundation of Jiangsu Province (BK2004218 ,BK2003106) Pandeng Project of Nanjing Universities of Postsand Telecommunications.
文摘Honeypot is a recent developed computer security concept which uses active offense to against attacks from hackers . It lures hackers to attack a seemly vulnerable fake network where they could be well observed in order to learn about the tactics and tools used by the attackers, so that we may improve the system security accordingly later. In this paper, we propose a novel approach for redirecting technique in honeypot system. First, we introduce briefly concepts of the honeypot system. Then we describe a redirection technique and an implementation algorithm. Finally, using the IDS Snort and the firewall IPTable, we set up a testing environment and give some simulations results. We also discuss some future research topics.
文摘Novel biologics that redirect cytotoxic T lymphocytes （CTLs） to kill tumor cells bearing a tumor associated antigen hold great promise in the clinic. However, the ability to safely and potently target CD3 on CTL toward tumor associated antigens （TAA） expressed on tumor cells remains a challenge of both technology and biol- ogy. Herein we describe the use of a Half DVD-Ig format that can redirect CTL to kill tumor cells. Notably, Half DVD-Ig molecules that are monovalent for each speci- ficity demonstrated reduced non-specific CTL activation and conditional CTL activation upon binding to TAA compared to intact tetravalent DVD-Ig molecules that are bivalent for each specificity, while maintaining good drug like properties and appropriate PK properties.
文摘研究小行星的暴露年龄对于理解其形成与演化具有重要意义。双小行星重定向测试(Double Asteroid Redirection Test,DART)任务的实施,不仅验证了动能撞击技术偏转近地小行星轨道的可行性,也为研究小行星暴露年龄及其成因演化提供了宝贵机会。基于DART撞击前后地基望远镜获得的可见近红外光谱数据,对主星Didymos表面及次星Dimorphos溅射物开展暴露年龄研究。结果表明,Didymos表面的暴露年龄约为45.7万年,表明主星在约45.7万年前发生了一次较大规模的物质脱落事件。该事件对主星的表面年龄几乎没有影响,但重置了次星的表面年龄及主星的暴露年龄。Dimorphos溅射物与主星Didymos的表面成分相同,但风化程度较低,这表明在次星形成后,主星和次星表面受到强烈的太空风化作用,而次星内部物质受到的太空风化作用相对较弱。
