An exciting prospect is the use of antimatter as a fuel source due to its ability to convert mass energy to kinetic energy. Upon annihilation of antimatter with matter, tremendous amounts of energy are carried away by...An exciting prospect is the use of antimatter as a fuel source due to its ability to convert mass energy to kinetic energy. Upon annihilation of antimatter with matter, tremendous amounts of energy are carried away by charged and neutral particles. By redirecting the charged particles through an exhaust using a non-uniform magnetic field, an impulse can be generated capable of supplying thrust to an engine. Using the Geant 4 simulation toolkit developed by CERN, we simulate this process using a beam core engine design. By analyzing charged pions that result from antiproton-proton annihilation, we optimize the engine parameters and derive a specific impulse for antiproton fuel as used in the beam core configuration. A specific impulse of (2.49 ± 0.08) × 106 s was determined. This value is significantly higher than specific impulses of current chemical rocket fuels which range from 240 - 400 s.展开更多
Section five of James Joyce＇s A Portrait of the Artist as a Young Man is designed, among other things, to dramatize a young poet＇s ascension to the rank of ＂priest of art,＂ Where Stephen had previously contemplate...Section five of James Joyce＇s A Portrait of the Artist as a Young Man is designed, among other things, to dramatize a young poet＇s ascension to the rank of ＂priest of art,＂ Where Stephen had previously contemplated being a Catholic priest, he now decides to embrace the world girdling Catholicity of global culture and its full range of spiritual traditions. To show how Stephen becomes a priest of art, Joyce has Stephen face three challengers in the form of MacCann, Davin, and Cranly, who all upbraid Dedalus to abandon his apostasy and conform. These three all try to tempt Dedalus away from his devotion to his individuality and personal integrity, and are analogues to the temptations faced by the Buddha on the eve of his enlightenment under the Bo tree. The Buddha faced Kama, the God of Desire; Mara, the Lord of death; and Dharma, who represents Duty. Stephen faces the temptations of social activism （and its attendant ego inflation） in the form of MacCann, a self-destructive Irish Nationalism in the figure of Davin and finally his obligation to his parochial and demanding family as represented by Cranly＇s arguments. Cranly （Dharma） even enjoins Stephen explicitly to make his Easter duty. These are dangerous distractions which can all keep Stephen from his goal, which is the Nibbana of artistic achievement. When Stephen triumphs over these three tempters he has come through the fire of self-doubt and is ready for his larger fate as an artist.展开更多
For a commutative ring R and a faithfully fiat R-algebra S we prove, under mild extra assumptions, that an R-module M is Gorenstein flat if and only if the left S-module S R M is Gorenstein flat, and that an R-module ...For a commutative ring R and a faithfully fiat R-algebra S we prove, under mild extra assumptions, that an R-module M is Gorenstein flat if and only if the left S-module S R M is Gorenstein flat, and that an R-module N is Gorenstein injective if and only if it is cotorsion and the left S-module Homn（S, N） is Gorenstein injective. We apply these results to the study of Gorenstein homological dimensions of unbounded complexes. In particular, we prove two theorems on stability of these dimensions under faithfully flat （co-）base change.展开更多
The 5G networks which have begun to spread worldwide are expected to contribute to an increase in the use of Internet of Things(IoT)technologies and applications,which require massive connectivity,security,and ultra-l...The 5G networks which have begun to spread worldwide are expected to contribute to an increase in the use of Internet of Things(IoT)technologies and applications,which require massive connectivity,security,and ultra-low latency.However,it is known that 5G alone is not sufficient for many IoT devices to exchange various types of data in real time.These constraints promote the emergence of 6G technologies which can support higher network capacity,lower latency,and faster data transmission than 5G networks.To understand the current trends in 6G research and their relation to IoT,this paper introduces the main drivers of 6G technology,describes 6G’s enabling technologies,summarizes current 6G research,and introduces the possible applications of 6G to IoT technologies and service areas.展开更多
文摘An exciting prospect is the use of antimatter as a fuel source due to its ability to convert mass energy to kinetic energy. Upon annihilation of antimatter with matter, tremendous amounts of energy are carried away by charged and neutral particles. By redirecting the charged particles through an exhaust using a non-uniform magnetic field, an impulse can be generated capable of supplying thrust to an engine. Using the Geant 4 simulation toolkit developed by CERN, we simulate this process using a beam core engine design. By analyzing charged pions that result from antiproton-proton annihilation, we optimize the engine parameters and derive a specific impulse for antiproton fuel as used in the beam core configuration. A specific impulse of (2.49 ± 0.08) × 106 s was determined. This value is significantly higher than specific impulses of current chemical rocket fuels which range from 240 - 400 s.
文摘Section five of James Joyce＇s A Portrait of the Artist as a Young Man is designed, among other things, to dramatize a young poet＇s ascension to the rank of ＂priest of art,＂ Where Stephen had previously contemplated being a Catholic priest, he now decides to embrace the world girdling Catholicity of global culture and its full range of spiritual traditions. To show how Stephen becomes a priest of art, Joyce has Stephen face three challengers in the form of MacCann, Davin, and Cranly, who all upbraid Dedalus to abandon his apostasy and conform. These three all try to tempt Dedalus away from his devotion to his individuality and personal integrity, and are analogues to the temptations faced by the Buddha on the eve of his enlightenment under the Bo tree. The Buddha faced Kama, the God of Desire; Mara, the Lord of death; and Dharma, who represents Duty. Stephen faces the temptations of social activism （and its attendant ego inflation） in the form of MacCann, a self-destructive Irish Nationalism in the figure of Davin and finally his obligation to his parochial and demanding family as represented by Cranly＇s arguments. Cranly （Dharma） even enjoins Stephen explicitly to make his Easter duty. These are dangerous distractions which can all keep Stephen from his goal, which is the Nibbana of artistic achievement. When Stephen triumphs over these three tempters he has come through the fire of self-doubt and is ready for his larger fate as an artist.
基金supported by the National Security Agency (Grant No. H98230-140140)National Natural Science Foundation of China (Grant Nos. 11301240 and 11371187)the Scientific Research Foundation for the Returned Overseas Chinese Scholars (State Education Ministry)
文摘For a commutative ring R and a faithfully fiat R-algebra S we prove, under mild extra assumptions, that an R-module M is Gorenstein flat if and only if the left S-module S R M is Gorenstein flat, and that an R-module N is Gorenstein injective if and only if it is cotorsion and the left S-module Homn（S, N） is Gorenstein injective. We apply these results to the study of Gorenstein homological dimensions of unbounded complexes. In particular, we prove two theorems on stability of these dimensions under faithfully flat （co-）base change.
文摘The 5G networks which have begun to spread worldwide are expected to contribute to an increase in the use of Internet of Things(IoT)technologies and applications,which require massive connectivity,security,and ultra-low latency.However,it is known that 5G alone is not sufficient for many IoT devices to exchange various types of data in real time.These constraints promote the emergence of 6G technologies which can support higher network capacity,lower latency,and faster data transmission than 5G networks.To understand the current trends in 6G research and their relation to IoT,this paper introduces the main drivers of 6G technology,describes 6G’s enabling technologies,summarizes current 6G research,and introduces the possible applications of 6G to IoT technologies and service areas.
