Rendezvous is a blind process establishing a communication link on a common channel between a pair of nodes in cognitive radio networks. We propose two guaranteed rendezvous algorithms for cognitive radio networks und...Rendezvous is a blind process establishing a communication link on a common channel between a pair of nodes in cognitive radio networks. We propose two guaranteed rendezvous algorithms for cognitive radio networks under both single-radio and multi-radio scenarios with an asynchronous setting. For single-radio scenario, each cycle length is a prime number associated with a channel hopping sequence.The rendezvous can be guaranteed as long as the IDs of the two nodes are different. For multi-radio scenario, we propose a cycle length and rotation based rendezvous algorithm. Each node generates a channel hopping sequence with only one cycle length. Then these radios of each nodes rotate on the generated sequence with different rotation numbers at each hopping cycle. The rendezvous between two nodes is guaranteed as long as they have different cycle lengths or the same cycle length with different number of rotations. We conduct simulations on three metrics and the results show that the proposed algorithms outperform the existing ones.展开更多
The design and realization of a new generation of infra-red electronic distance measurement (IR EDM) system are presented.A DSP(Digital Signal Process) phase detector based on high speed analog-to-digital converter an...The design and realization of a new generation of infra-red electronic distance measurement (IR EDM) system are presented.A DSP(Digital Signal Process) phase detector based on high speed analog-to-digital converter and DSP technique has been designed,in order to improve the precision and reliability of IR EDM system.As a result,the EDM system developed with a DSP phase detector has a precision of 3 mm in the measuring range of 2 km.展开更多
In this paper, we subdivide the sample of manufacturing companies listed in two stock exchanges in China from the year 2000 to 2009 into two categories： the firms which adopted the similar financial models and those ...In this paper, we subdivide the sample of manufacturing companies listed in two stock exchanges in China from the year 2000 to 2009 into two categories： the firms which adopted the similar financial models and those which did not. Then we use t-test and nonparametric test to explore the differences between the two sub-samples in cash management, assets and liabilities structures, assets turnover ratios, profitability, liquidity and growth rates. The results show that the former has shorter Cash Conversion Cycle （CCC）, quicker assets turnover, higher Debt Ratio （DR）, higher growth rate and thus has better profitability. In addition, the regression analysis results further demonstrate that Return on Invested Capital （ROIC） of similar-financial-model firms are positively related to Net Profit Margin （NPM） （p 〈 0.01）, and negatively to CCC （p 〈 0.01）, Interest Expense Ratio （IER） （p 〈 0.01）, the Ratio of Interest-Bearing Debt to Total Liabilities （IBDR） （p 〈 0.01） and the ratio of Net Receivables to Sales Revenue （NRSR） （p 〈 0.01）. Moreover, negative relationship between ROIC and dummy variable GROUP implies that the former has better profitability than the latter.展开更多
It is of great interest to study the dynamical environment on the surface of non-spherical small bodies, especially for asteroids. This paper takes a simple case of a cube for instance, investigates the dynamics of a ...It is of great interest to study the dynamical environment on the surface of non-spherical small bodies, especially for asteroids. This paper takes a simple case of a cube for instance, investigates the dynamics of a particle on the surface of a rotating homogeneous cube, and derives fruitful results. Due to the symmetrical characteristic of the cube, the analysis includes motions on two different types of surfaces. For each surface, both the frictionless and friction cases are considered. (i) Without consideration of friction, the surface equilibria in both of the different surfaces are examined and periodic orbits are derived. The analysis of equilibria and periodic orbits could assist understanding the skeleton of motions on the surface of asteroids. (ii) For the friction cases, the conditions that the particle does not escape from the surface are examined. Due to the effect of the friction, there exist the equilibrium regions on the surface where the particle stays at rest, and the locations of them are found. Finally, the dust collection regions are predicted. Future work will extend to real asteroid shapes.展开更多
Full-annulus three-dimensional unsteady numerical simulations were conducted for a low-speed isolated axialcompressor rotor, intending to identify the behavior of self-induced unsteady tip leakage flow within multi-bl...Full-annulus three-dimensional unsteady numerical simulations were conducted for a low-speed isolated axialcompressor rotor, intending to identify the behavior of self-induced unsteady tip leakage flow within multi-bladepassages. There is a critical mass flow rate near stall point, below it, the self-induced unsteadiness of tip leakageflow can propagate circumferentially and thus initiates two circumferential waves. Otherwise, the self-inducedunsteady tip leakage flow oscillates synchronously in each single blade passage. The major findings are: 1) whilethe self-induced unsteadiness of tip leakage flow is a single-passage phenomenon, there exist phase shifts amongblade passages in multi-passage environments then evolving into the first short length wave propagating at abouttwo times of rotor rotation speed after the transient period ends; and 2) the time traces of the pseudo sensors locatedon the rotor blade tips reveal another much longer length-scale wave modulated with the first wave due tophase shift propagating at about half of rotor rotation speed. Features of the short and long length-scale circumferentialwaves are similar to those of rotating instability and modal wave, respectively.展开更多
基金supported in part by NSF under the grant CNS-1526152
文摘Rendezvous is a blind process establishing a communication link on a common channel between a pair of nodes in cognitive radio networks. We propose two guaranteed rendezvous algorithms for cognitive radio networks under both single-radio and multi-radio scenarios with an asynchronous setting. For single-radio scenario, each cycle length is a prime number associated with a channel hopping sequence.The rendezvous can be guaranteed as long as the IDs of the two nodes are different. For multi-radio scenario, we propose a cycle length and rotation based rendezvous algorithm. Each node generates a channel hopping sequence with only one cycle length. Then these radios of each nodes rotate on the generated sequence with different rotation numbers at each hopping cycle. The rendezvous between two nodes is guaranteed as long as they have different cycle lengths or the same cycle length with different number of rotations. We conduct simulations on three metrics and the results show that the proposed algorithms outperform the existing ones.
文摘The design and realization of a new generation of infra-red electronic distance measurement (IR EDM) system are presented.A DSP(Digital Signal Process) phase detector based on high speed analog-to-digital converter and DSP technique has been designed,in order to improve the precision and reliability of IR EDM system.As a result,the EDM system developed with a DSP phase detector has a precision of 3 mm in the measuring range of 2 km.
文摘In this paper, we subdivide the sample of manufacturing companies listed in two stock exchanges in China from the year 2000 to 2009 into two categories： the firms which adopted the similar financial models and those which did not. Then we use t-test and nonparametric test to explore the differences between the two sub-samples in cash management, assets and liabilities structures, assets turnover ratios, profitability, liquidity and growth rates. The results show that the former has shorter Cash Conversion Cycle （CCC）, quicker assets turnover, higher Debt Ratio （DR）, higher growth rate and thus has better profitability. In addition, the regression analysis results further demonstrate that Return on Invested Capital （ROIC） of similar-financial-model firms are positively related to Net Profit Margin （NPM） （p 〈 0.01）, and negatively to CCC （p 〈 0.01）, Interest Expense Ratio （IER） （p 〈 0.01）, the Ratio of Interest-Bearing Debt to Total Liabilities （IBDR） （p 〈 0.01） and the ratio of Net Receivables to Sales Revenue （NRSR） （p 〈 0.01）. Moreover, negative relationship between ROIC and dummy variable GROUP implies that the former has better profitability than the latter.
基金supported by the National Basic Research Program of China (Grant No. 2012CB720000)the National Natural Science Foundation of China (Grant No. 11072122)
文摘It is of great interest to study the dynamical environment on the surface of non-spherical small bodies, especially for asteroids. This paper takes a simple case of a cube for instance, investigates the dynamics of a particle on the surface of a rotating homogeneous cube, and derives fruitful results. Due to the symmetrical characteristic of the cube, the analysis includes motions on two different types of surfaces. For each surface, both the frictionless and friction cases are considered. (i) Without consideration of friction, the surface equilibria in both of the different surfaces are examined and periodic orbits are derived. The analysis of equilibria and periodic orbits could assist understanding the skeleton of motions on the surface of asteroids. (ii) For the friction cases, the conditions that the particle does not escape from the surface are examined. Due to the effect of the friction, there exist the equilibrium regions on the surface where the particle stays at rest, and the locations of them are found. Finally, the dust collection regions are predicted. Future work will extend to real asteroid shapes.
基金the National Natural Science Foundation of China with project No. 50676094 and No. 50736007the National Basic Research Program of China numbered 2007CB210104
文摘Full-annulus three-dimensional unsteady numerical simulations were conducted for a low-speed isolated axialcompressor rotor, intending to identify the behavior of self-induced unsteady tip leakage flow within multi-bladepassages. There is a critical mass flow rate near stall point, below it, the self-induced unsteadiness of tip leakageflow can propagate circumferentially and thus initiates two circumferential waves. Otherwise, the self-inducedunsteady tip leakage flow oscillates synchronously in each single blade passage. The major findings are: 1) whilethe self-induced unsteadiness of tip leakage flow is a single-passage phenomenon, there exist phase shifts amongblade passages in multi-passage environments then evolving into the first short length wave propagating at abouttwo times of rotor rotation speed after the transient period ends; and 2) the time traces of the pseudo sensors locatedon the rotor blade tips reveal another much longer length-scale wave modulated with the first wave due tophase shift propagating at about half of rotor rotation speed. Features of the short and long length-scale circumferentialwaves are similar to those of rotating instability and modal wave, respectively.
