As an extension of the"teleparallel"equivalent of general relativity,f(T)gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modif...As an extension of the"teleparallel"equivalent of general relativity,f(T)gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modified gravity also has impacts on the Solar System,we might test it during future interplanetary missions with ultrastable clocks.In this work,we investigate the effects of f(T)gravity on the dynamics of the clock and its time transfer link.Under these influences,theΛ-term and theα-term of f(T)gravity play important roles.Here,Λis the cosmological constant andαrepresents a model parameter in f(T)gravity that determines the divergence from teleparallel gravity at the first order approximation.We find that the signal of f(T)gravity in the time transfer is much more difficult to detect with the current state of development for clocks than those effects on dynamics of an interplanetary spacecraft with a bounded orbit with parameters 0.5 au≤a≤5.5 au and 0≤e≤0.1.展开更多
20th century physics experimentally established beyond doubt the fact that moving clocks read differently from “static” clocks. This fact is typically interpreted as support for special relativity. On the other hand...20th century physics experimentally established beyond doubt the fact that moving clocks read differently from “static” clocks. This fact is typically interpreted as support for special relativity. On the other hand, the same century produced proof that clocks at various locations in the gravitational field also read differently, and this fact is explained by general relativity, which is, in general, not Lorentz transformable. This paper establishes a common framework for the physics of clocks in these different situations.展开更多
Haug has recently introduced a new theory of unified quantum gravity coined “<em>Collision Space-Time</em>”. From this new and deeper understanding of mass, we can also understand how a grandfather pendu...Haug has recently introduced a new theory of unified quantum gravity coined “<em>Collision Space-Time</em>”. From this new and deeper understanding of mass, we can also understand how a grandfather pendulum clock can be used to measure the world’s shortest time interval, namely the Planck time, indirectly, without any knowledge of G. Therefore, such a clock can also be used to measure the diameter of an indivisible particle indirectly. Further, such a clock can easily measure the Schwarzschild radius of the gravity object and what we will call “Schwarzschild time”. These facts basically prove that the Newton gravitational constant is not needed to find the Planck length or the Planck time;it is also not needed to find the Schwarzschild radius. Unfortunately, there is significant inertia towards new ideas that could significantly alter our perspective on the fundamentals in the current physics establishment. However, this situation is not new in the history of science. Still, the idea that the Planck time can be measured totally independently of any knowledge of Newton’s gravitational constant could be very important for moving forward in physics. Interestingly, an old instrument that today is often thought of as primitive instrument can measure the world’s shortest possible time interval. No atomic clock or optical clock is even close to be able to do this.展开更多
In this paper, the design of a coarse-fine interpolation Time-to-Digital Converter (TDC) is implemented in an ALTERA’s Cyclone FPGA. The carry-select chain performs as the tapped delay line. The Logic Array Block (LA...In this paper, the design of a coarse-fine interpolation Time-to-Digital Converter (TDC) is implemented in an ALTERA’s Cyclone FPGA. The carry-select chain performs as the tapped delay line. The Logic Array Block (LAB) having a propagation delay of 165 ps in the chain is synthesized as delay cell. Coarse counters triggered by the global clock count the more significant bits of the time data. This clock is also fed through the delay line, and LABs create the copies. The replicas are latched by the tested event signal, and the less significant bits are encoded from the latched binary bits. Single-shot resolution of the TDC can be 60 ps. The worst Differential Nonlinearity (DNL) is about 0.2 Least Significant Bit (LSB, 165 ps in this TDC module), and the Integral Nonlinearity (INL) is 0.6 LSB. In comparison with other architectures using the synchronous global clock to sample the taps, this architecture consumed less electric power and logic cells, and is more stable.展开更多
Real-time satellite orbit and clock corrections obtained from the broadcast ephemerides can be improved using IGS real-time service (RTS) products. Recent research showed that applying such corrections for broadcast e...Real-time satellite orbit and clock corrections obtained from the broadcast ephemerides can be improved using IGS real-time service (RTS) products. Recent research showed that applying such corrections for broadcast ephemerides can significantly improve the RMS of the estimated coordinates. However, unintentional streaming interruption may happen for many reasons such as software or hardware failure. Streaming interruption, if happened, will cause sudden degradation of the obtained solution if only the broadcast ephemerides are used. A better solution can be obtained in real-time if the predicted part of the ultra-rapid products is used. In this paper, Harmonic analysis technique is used to predict the IGS RTS corrections using historical broadcasted data. It is shown that using the predicted clock corrections improves the RMS of the estimated coordinates by about 72%, 58%, and 72% in latitude, longitude, and height directions, respectively and reduces the 2D and 3D errors by about 80% compared with the predicted part of the IGS ultra-rapid clock corrections.展开更多
The data acquisition stations and the data processing center of the Science and Application Center for Lunar and Deep-space Exploration (SACLuDE) are located at different geographical sites. They respectively have the...The data acquisition stations and the data processing center of the Science and Application Center for Lunar and Deep-space Exploration (SACLuDE) are located at different geographical sites. They respectively have their own local networks and interconnect with each other through access to the core data network. This paper describes the clock drift in the computer and other networked devices building up the infrastructure of the above local networks. The network time variance of the stochastic model is also estimated. The poor precision of network synchronization will bring about potential hazards to the network operation and application running in the networks, which is clarified in the present paper. At the end of the paper, a cost-effective and feasible solution is proposed based on the Global Position System (GPS) and the Network Time Protocol (NTP).展开更多
There is an impressive scarcity of quantitative models of the clock patterns in the brain. We propose a mesoscopic approach, i.e. neither a description at single neuron level, nor at systemic level/too coarse granular...There is an impressive scarcity of quantitative models of the clock patterns in the brain. We propose a mesoscopic approach, i.e. neither a description at single neuron level, nor at systemic level/too coarse granularity, of the time perception at the time of the saccade. This model uses functional pathway knowledge and is inspired by, and integrates, recent findings in both psychophysics and neurophysiology. Perceived time delays in the perisaccadic window are shown numerically consistent with recent experimental measures. Our model provides explanation for several experimental outcomes on saccades, estimates popu-lation variance of the error in time perception and represent a meaningful example for bridging psychophysics and neurophysiology. Finally we found that the insights into information processing during saccadic events lead to considerations on engineering exploitation of the underlying phenomena.展开更多
Einstein relativity theory shows its high capability of promoting itself to solve the long stand physical problems. The so-called generalized special relativity (GSR) was derived later, using the beautiful Einstein re...Einstein relativity theory shows its high capability of promoting itself to solve the long stand physical problems. The so-called generalized special relativity (GSR) was derived later, using the beautiful Einstein relation between field and space-time curvature. In this work we re-derive (GSR) expression of time by incorporating the field effect in it, and by using mirror clock and Lorentz transformations. This expression reduces to that of (GSR) the previous conventional one, besides reducing to special relativistic expression. It also shows that the speed of light is constant inside the field and is equal to C. This means that the observed decrease of light in matter and field is attributed to the strong interaction of photons with particles and mediates which causes successive absorption and reemission processes that lead to time delay. This absorption process makes some particles appear to move faster than light within the field or medium. This new expression, unlike that of GSR, can describe time and coordinate relativistic expressions for strong as well as weak fields at constant acceleration.展开更多
Satellite disciplined clock system(SDCS)composed of satellite timing receiver and local frequency synthesis is widely applied for its high accuracy and low cost.This paper provides a review of SDCS.Key technologies su...Satellite disciplined clock system(SDCS)composed of satellite timing receiver and local frequency synthesis is widely applied for its high accuracy and low cost.This paper provides a review of SDCS.Key technologies such as phase difference measurement,pulse noise process and frequency calibration are surveyed in detail.Disciplined clock model based on PI controller is built and disciplined process is analyzed.The methods of realizing the disciplined clock circuit are classified and summarized.A prototype based on FPGA is proposed.At last development trend of SDCS is discussed.展开更多
Shifting the feeding time for fish from daytime to nighttime could alter their digestive behavior, disturb their metabolism, and may af fect immune-related genes. This study aimed to clone complement component C7 and ...Shifting the feeding time for fish from daytime to nighttime could alter their digestive behavior, disturb their metabolism, and may af fect immune-related genes. This study aimed to clone complement component C7 and analyze the different expression of C7 mRNA in fish fed during either the day or at night and then challenged with Aeromonas hydrophila infection. The P v-C7 cDNA of Pelteobagrus vachellii contained 2 647 bp with an open reading frame encoding a protein of 818 amino acids. Multiple sequences analysis indicated that P v-C7 included eight domains, which was similar to results for other species. Quantitative PCR analysis showed that P v-C7 was mainly expressed in the liver, spleen, intestine and head kidney tissues of healthy P. vachellii. Quantitative PCR analysis showed that C7 mRNA transcript in the liver, spleen and head kidney also increased significantly when the fish were fed at nighttime(20:00). In addition, the expression of Pv-C7 mRNA significantly increased with A. hydrophila challenge in the liver(48–96 h), spleen and head kidney(12–96 h) tissues of P. vachellii. Pv-C7 mRNA expression of the fish fed at nighttime showed significant higher than that in the fish fed at day time at 12–48 h in head kidney and 12–24 h in spleen. This study indicates that altering the feeding time from daytime to nighttime could increase P v-C7 mRNA expression, and feeding time may af fect the immune response involving C7.展开更多
This paper proposes a distributed second-order consensus time synchronization, which incorporates the second-order consensus algorithm into wireless sensor networks. Since local clocks may have different skews and off...This paper proposes a distributed second-order consensus time synchronization, which incorporates the second-order consensus algorithm into wireless sensor networks. Since local clocks may have different skews and offsets, the algorithm is designed to include offset compensation and skew compensation. The local clocks are not directly modified, thus the virtual clocks are built according to the local clocks via the compensation parameters. Each node achieves a virtual consensus clock by periodically updated compensation parameters. Finally, the effectiveness of the proposed algorithm is verified through a number of simulations in a mesh network. It is proved that the proposed algorithm has the advantage of being distributed, asymptotic convergence, and robust to new node joining.展开更多
In this work we find a lower bound on the energy required for synchronizing moving sensor nodes in a Wireless Sensor Network (WSN) affected by large-scale fading, based on clock estimation techniques. The energy requi...In this work we find a lower bound on the energy required for synchronizing moving sensor nodes in a Wireless Sensor Network (WSN) affected by large-scale fading, based on clock estimation techniques. The energy required for synchronizing a WSN within a desired estimation error level is specified by both the transmit power and the required number of messages. In this paper we extend our previous work introducing nodes’ movement and the average message delay in the total energy, including a comprehensive analysis on how the distance between nodes impacts on the energy and synchronization quality trade-off under large-scale fading effects.展开更多
In this work, the existing trade-off between time synchronization quality and energy is studied for both large-scale and small-scale fading wireless channels. We analyze the clock offset estimation problem using one-w...In this work, the existing trade-off between time synchronization quality and energy is studied for both large-scale and small-scale fading wireless channels. We analyze the clock offset estimation problem using one-way, two-way and N-way message exchange mechanisms affected by Gaussian and exponentially distributed impairments. Our main contribution is a general relationship between the total energy required for synchronizing a wireless sensor network and the clock offset estimation error by means of the transmit power, number of transmitted messages and average message delay, deriving the energy optimal lower bound as a function of the time synchronization quality and the number of hops in a multi-hop network.展开更多
Industrial timer requirements are multifaceted. On-delay, off-delay, cyclic or sequential timing requirements, with usual time range varying from seconds to days, depending on the process. Custom build timers cannot p...Industrial timer requirements are multifaceted. On-delay, off-delay, cyclic or sequential timing requirements, with usual time range varying from seconds to days, depending on the process. Custom build timers cannot provide all of these requirements simultaneously and hence an advanced timer rectifying this shortcoming has been designed and fabricated in this work. This timer is based on the real time clock chip used in mother boards. Our design can be programmed for a specific time requirement and can later be put to work in standalone mode. A demonstration board is fabricated and tested.展开更多
The NIM4 cesium fountain clock has been operating stably and sub-continually since Aug. 2003. In this paper we present improvements on NIM4 in 2005-2006 and the most recent evaluation for its frequency shifts with an ...The NIM4 cesium fountain clock has been operating stably and sub-continually since Aug. 2003. In this paper we present improvements on NIM4 in 2005-2006 and the most recent evaluation for its frequency shifts with an uncertainty of 5E-15. A 220 days comparison between NIM4 and GPS showed an agreement of 2E-14. Finally the construction of a NIM5 transportable cesium fountain clock is briefly reported.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 11103010)funded by the Natural Science Foundation of China (Grant No. 11103085)+3 种基金the Fundamental Research Program of Jiangsu Province of China (Grant No. BK20131461Grant No. BK2011553)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110091120003)the Fundamental Research Funds for the Central Universities (No. 1107020116)
文摘As an extension of the"teleparallel"equivalent of general relativity,f(T)gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modified gravity also has impacts on the Solar System,we might test it during future interplanetary missions with ultrastable clocks.In this work,we investigate the effects of f(T)gravity on the dynamics of the clock and its time transfer link.Under these influences,theΛ-term and theα-term of f(T)gravity play important roles.Here,Λis the cosmological constant andαrepresents a model parameter in f(T)gravity that determines the divergence from teleparallel gravity at the first order approximation.We find that the signal of f(T)gravity in the time transfer is much more difficult to detect with the current state of development for clocks than those effects on dynamics of an interplanetary spacecraft with a bounded orbit with parameters 0.5 au≤a≤5.5 au and 0≤e≤0.1.
文摘20th century physics experimentally established beyond doubt the fact that moving clocks read differently from “static” clocks. This fact is typically interpreted as support for special relativity. On the other hand, the same century produced proof that clocks at various locations in the gravitational field also read differently, and this fact is explained by general relativity, which is, in general, not Lorentz transformable. This paper establishes a common framework for the physics of clocks in these different situations.
文摘Haug has recently introduced a new theory of unified quantum gravity coined “<em>Collision Space-Time</em>”. From this new and deeper understanding of mass, we can also understand how a grandfather pendulum clock can be used to measure the world’s shortest time interval, namely the Planck time, indirectly, without any knowledge of G. Therefore, such a clock can also be used to measure the diameter of an indivisible particle indirectly. Further, such a clock can easily measure the Schwarzschild radius of the gravity object and what we will call “Schwarzschild time”. These facts basically prove that the Newton gravitational constant is not needed to find the Planck length or the Planck time;it is also not needed to find the Schwarzschild radius. Unfortunately, there is significant inertia towards new ideas that could significantly alter our perspective on the fundamentals in the current physics establishment. However, this situation is not new in the history of science. Still, the idea that the Planck time can be measured totally independently of any knowledge of Newton’s gravitational constant could be very important for moving forward in physics. Interestingly, an old instrument that today is often thought of as primitive instrument can measure the world’s shortest possible time interval. No atomic clock or optical clock is even close to be able to do this.
基金Supported by National Natural Science Foundation of China (No. 10405023)Knowledge Innovation Program of The Chinese Academy of Sciences (KJCX2-YW-N27)
文摘In this paper, the design of a coarse-fine interpolation Time-to-Digital Converter (TDC) is implemented in an ALTERA’s Cyclone FPGA. The carry-select chain performs as the tapped delay line. The Logic Array Block (LAB) having a propagation delay of 165 ps in the chain is synthesized as delay cell. Coarse counters triggered by the global clock count the more significant bits of the time data. This clock is also fed through the delay line, and LABs create the copies. The replicas are latched by the tested event signal, and the less significant bits are encoded from the latched binary bits. Single-shot resolution of the TDC can be 60 ps. The worst Differential Nonlinearity (DNL) is about 0.2 Least Significant Bit (LSB, 165 ps in this TDC module), and the Integral Nonlinearity (INL) is 0.6 LSB. In comparison with other architectures using the synchronous global clock to sample the taps, this architecture consumed less electric power and logic cells, and is more stable.
文摘Real-time satellite orbit and clock corrections obtained from the broadcast ephemerides can be improved using IGS real-time service (RTS) products. Recent research showed that applying such corrections for broadcast ephemerides can significantly improve the RMS of the estimated coordinates. However, unintentional streaming interruption may happen for many reasons such as software or hardware failure. Streaming interruption, if happened, will cause sudden degradation of the obtained solution if only the broadcast ephemerides are used. A better solution can be obtained in real-time if the predicted part of the ultra-rapid products is used. In this paper, Harmonic analysis technique is used to predict the IGS RTS corrections using historical broadcasted data. It is shown that using the predicted clock corrections improves the RMS of the estimated coordinates by about 72%, 58%, and 72% in latitude, longitude, and height directions, respectively and reduces the 2D and 3D errors by about 80% compared with the predicted part of the IGS ultra-rapid clock corrections.
文摘The data acquisition stations and the data processing center of the Science and Application Center for Lunar and Deep-space Exploration (SACLuDE) are located at different geographical sites. They respectively have their own local networks and interconnect with each other through access to the core data network. This paper describes the clock drift in the computer and other networked devices building up the infrastructure of the above local networks. The network time variance of the stochastic model is also estimated. The poor precision of network synchronization will bring about potential hazards to the network operation and application running in the networks, which is clarified in the present paper. At the end of the paper, a cost-effective and feasible solution is proposed based on the Global Position System (GPS) and the Network Time Protocol (NTP).
文摘There is an impressive scarcity of quantitative models of the clock patterns in the brain. We propose a mesoscopic approach, i.e. neither a description at single neuron level, nor at systemic level/too coarse granularity, of the time perception at the time of the saccade. This model uses functional pathway knowledge and is inspired by, and integrates, recent findings in both psychophysics and neurophysiology. Perceived time delays in the perisaccadic window are shown numerically consistent with recent experimental measures. Our model provides explanation for several experimental outcomes on saccades, estimates popu-lation variance of the error in time perception and represent a meaningful example for bridging psychophysics and neurophysiology. Finally we found that the insights into information processing during saccadic events lead to considerations on engineering exploitation of the underlying phenomena.
文摘Einstein relativity theory shows its high capability of promoting itself to solve the long stand physical problems. The so-called generalized special relativity (GSR) was derived later, using the beautiful Einstein relation between field and space-time curvature. In this work we re-derive (GSR) expression of time by incorporating the field effect in it, and by using mirror clock and Lorentz transformations. This expression reduces to that of (GSR) the previous conventional one, besides reducing to special relativistic expression. It also shows that the speed of light is constant inside the field and is equal to C. This means that the observed decrease of light in matter and field is attributed to the strong interaction of photons with particles and mediates which causes successive absorption and reemission processes that lead to time delay. This absorption process makes some particles appear to move faster than light within the field or medium. This new expression, unlike that of GSR, can describe time and coordinate relativistic expressions for strong as well as weak fields at constant acceleration.
文摘Satellite disciplined clock system(SDCS)composed of satellite timing receiver and local frequency synthesis is widely applied for its high accuracy and low cost.This paper provides a review of SDCS.Key technologies such as phase difference measurement,pulse noise process and frequency calibration are surveyed in detail.Disciplined clock model based on PI controller is built and disciplined process is analyzed.The methods of realizing the disciplined clock circuit are classified and summarized.A prototype based on FPGA is proposed.At last development trend of SDCS is discussed.
基金Supported by the National Natural Science Foundation of China(No.31402305)the Natural Science Foundation of Sichuan Province(No.2017JY0161)the Educational Commission of Sichuan Province of China(No.14ZA0249)
文摘Shifting the feeding time for fish from daytime to nighttime could alter their digestive behavior, disturb their metabolism, and may af fect immune-related genes. This study aimed to clone complement component C7 and analyze the different expression of C7 mRNA in fish fed during either the day or at night and then challenged with Aeromonas hydrophila infection. The P v-C7 cDNA of Pelteobagrus vachellii contained 2 647 bp with an open reading frame encoding a protein of 818 amino acids. Multiple sequences analysis indicated that P v-C7 included eight domains, which was similar to results for other species. Quantitative PCR analysis showed that P v-C7 was mainly expressed in the liver, spleen, intestine and head kidney tissues of healthy P. vachellii. Quantitative PCR analysis showed that C7 mRNA transcript in the liver, spleen and head kidney also increased significantly when the fish were fed at nighttime(20:00). In addition, the expression of Pv-C7 mRNA significantly increased with A. hydrophila challenge in the liver(48–96 h), spleen and head kidney(12–96 h) tissues of P. vachellii. Pv-C7 mRNA expression of the fish fed at nighttime showed significant higher than that in the fish fed at day time at 12–48 h in head kidney and 12–24 h in spleen. This study indicates that altering the feeding time from daytime to nighttime could increase P v-C7 mRNA expression, and feeding time may af fect the immune response involving C7.
基金Supported by the National Natural Science Foundation of China(No.61340034)the Research Program of Application Foundation and Advanced Technology of Tianjin(No.13JCYBJC15600)
文摘This paper proposes a distributed second-order consensus time synchronization, which incorporates the second-order consensus algorithm into wireless sensor networks. Since local clocks may have different skews and offsets, the algorithm is designed to include offset compensation and skew compensation. The local clocks are not directly modified, thus the virtual clocks are built according to the local clocks via the compensation parameters. Each node achieves a virtual consensus clock by periodically updated compensation parameters. Finally, the effectiveness of the proposed algorithm is verified through a number of simulations in a mesh network. It is proved that the proposed algorithm has the advantage of being distributed, asymptotic convergence, and robust to new node joining.
文摘In this work we find a lower bound on the energy required for synchronizing moving sensor nodes in a Wireless Sensor Network (WSN) affected by large-scale fading, based on clock estimation techniques. The energy required for synchronizing a WSN within a desired estimation error level is specified by both the transmit power and the required number of messages. In this paper we extend our previous work introducing nodes’ movement and the average message delay in the total energy, including a comprehensive analysis on how the distance between nodes impacts on the energy and synchronization quality trade-off under large-scale fading effects.
文摘In this work, the existing trade-off between time synchronization quality and energy is studied for both large-scale and small-scale fading wireless channels. We analyze the clock offset estimation problem using one-way, two-way and N-way message exchange mechanisms affected by Gaussian and exponentially distributed impairments. Our main contribution is a general relationship between the total energy required for synchronizing a wireless sensor network and the clock offset estimation error by means of the transmit power, number of transmitted messages and average message delay, deriving the energy optimal lower bound as a function of the time synchronization quality and the number of hops in a multi-hop network.
文摘Industrial timer requirements are multifaceted. On-delay, off-delay, cyclic or sequential timing requirements, with usual time range varying from seconds to days, depending on the process. Custom build timers cannot provide all of these requirements simultaneously and hence an advanced timer rectifying this shortcoming has been designed and fabricated in this work. This timer is based on the real time clock chip used in mother boards. Our design can be programmed for a specific time requirement and can later be put to work in standalone mode. A demonstration board is fabricated and tested.
文摘The NIM4 cesium fountain clock has been operating stably and sub-continually since Aug. 2003. In this paper we present improvements on NIM4 in 2005-2006 and the most recent evaluation for its frequency shifts with an uncertainty of 5E-15. A 220 days comparison between NIM4 and GPS showed an agreement of 2E-14. Finally the construction of a NIM5 transportable cesium fountain clock is briefly reported.