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Experimental measurement of growth patterns on fossil corals:Secular variation in ancient Earth-Sun distances

Chinese science Bulletin 2010年第35期55卷 4010-4017页

作者： ZHANG WeiJia1,3,4,LI ZhengBin2,3 & LEI Yang1 1 Department of Physics,Peking University,Beijing 100871,China 2 Department of Electrical Engineering and computer science,Peking University,Beijing 100871,China 3 State Key Laboratory of Advanced Optical communication Systems & networks,Peking University,Beijing 100871,China 4 Committee of Yuanpei Honors Program,Peking University,Beijing 100871,China Department of Physics Peking University Beijing 100871 China State Key Laboratory of Advanced Optical Communication Systems & Networks Peking University Beijing 100871 China Committee of Yuanpei Honors Program Peking University Beijing 100871 China Department of Electrical Engineering and Computer Science Peking University Beijing 100871 China

In recent years,much attention has been given to the increase in the Earth-Sun distance,with the modern rate reported as 5-15 m/cy on the basis of astronomical ***,traditional methods cannot measure the ancient leaving rates,so a myriad of research attempting to provide explanations were met with unmatched *** this paper we consider that the growth patterns on fossils could reflect the ancient Earth-Sun *** mechanical analysis of both the Earth-Sun and Earth-Moon systems,these patterns confirmed an increase in the Earth-Sun *** a large number of well-preserved specimens and new technology available,both the modern and ancient leaving rates could be measured with high precision,and it was found that the Earth has been leaving the Sun over the past 0.53 billion *** Earth's semi-major axis was 146 million kilometers at the beginning of the Phanerozoic Eon,equating to 97.6% of its current *** modern leaving rates are 5-14 m/cy,whereas the ancient rates were much *** results indicate a special expansion with an average expansion coefficient of 0.57H0 and deceleration in the form of Hubble *** the basis of experimental results,the Earth's semi-major axis could be represented by a simple formula that matches fossil measurements.

关键词：地球太阳古代距离生长模式实验石珊瑚量化

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Soft Frequency Reuse in the Uplink of an OFDMA Network

Soft Frequency Reuse in the Uplink of an OFDMA Network

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IEEE Conference on Vehicular Technology (VTC)

作者： Florian Wamser David Mittelstädt Dirk Staehle University of Würzburg Institute of Computer Science Chair of Communication Networks Würzburg Germany

ISBN: (纸本)9781424425181;9781424425198

The challenges with deploying a cellular wireless communication network with static frequency reuse in an interference limited environment is that for highly loaded cells, significant regions of coverage will experience high interference levels, resulting in unserviceable low signal-to-interference values. Therefore, interference mitigation approaches as adaptive fractional frequency reuse are considered to tackle the problem. In this paper, different strategies for user and resource allocation are evaluated along with fractional frequency reuse schemes. In contrast to downlink scenarios, we investigate the performance of the OFDMA uplink. It is shown that soft frequency reuse is well-performing in the uplink although it is easy to deploy since it does not rely on resource coordination.

关键词： Interference Resource management Frequency conversion Radio spectrum management Downlink Mobile computing Throughput Cellular networks computer science communication networks

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Passive scheme with a photon-number-resolving detector for monitoring the untrusted source in a plug-and-play quantum-key-distribution system

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Physical Review A 2010年第4期82卷 042301-042301页

作者： Bingjie Xu Xiang Peng Hong Guo State Key Laboratory of Advanced Optical Communication Systems and Networks (Peking University) School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

A passive scheme with a beam splitter and a photon-number-resolving (PNR) detector is proposed to verify the photon statistics of an untrusted source in a plug-and-play quantum-key-distribution system by applying a three-intensity decoy-state protocol. The practical issues due to statistical fluctuation and detection noise are analyzed. The simulation results show that the scheme can work efficiently when the total number of optical pulses sent from Alice to Bob is above 108, and the dark count rate of the PNR detector is below 0.5 counts/pulse, which is realizable with current techniques. Furthermore, we propose a practical realization of the PNR detector with a variable optical attenuator combined with a threshold detector.

关键词： Photons

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The delay with new-additive increase multiplicative decrease congestion avoidance and control algorithm

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Information Technology Journal 2010年第7期9卷 1327-1335页

作者： Jasem, HayderNatiq Zukarnain, ZuriatiAhmad Othman, Mohamed Subramaniam, Shamala Department of Communication Technology and Networks Faculty of Computer Science and Information Technology University Putra Malaysia 43400 UPM Serdang Selangor Malaysia

As the Internet becomes increasingly heterogeneous, the issue of congestion control becomes ever more important. And the queue length and end-to-end (congestion) delays are some of the important things in term of congestion avoidance and control mechanisms. In this research we continued to study the performances of the New-Additive Increase Multiplicative Decrease (AIMD) algorithm as one of the core protocols for TCP congestion avoidance and control mechanism, we want now to evaluate the effect of using the New-AIMD algorithm to measure the queue length and end-to-end delays and we will use the NCTUns simulator to get the results after make the modification of the mechanism. And we will use the Droptail mechanism as Active Queue Management (AQM) in the bottleneck router. After implementation of our new approach with different number of flows, we will measure the delay for two types of delays (queuing delay and end-to-end delay), we expect the delay will be less with using our mechanism comparing with the mechanism in the previous study. Now and after got this results as low delay for bottleneck link case, we know the New-AIMD mechanism work as well under the network condition in the experiments. © 2010 Asian Network for Scientific Information.

关键词： Transmission control protocol

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Scheduling Complex Automotive Embedded Real-Time Systems

Scheduling Complex Automotive Embedded Real-Time Systems

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2010 IEEE International Conference on Vehicular Electronics and Safety(2010 IEEE 汽车电子与安全国际会议)

作者： Reinhard German Christoph Lauer Kai-Steffen Hielscher Jens Pollmer Department of Computer Science 7 Computer Networks and Communication Systems University of Erlangen- Department of Safety Electronics Audi AG Ingolstadt Germany

The formal verification of task schedulability is getting more important in the automotive domain as more and more applications are integrated into domain specific controllers. Especially for safety critical applications an indepth knowledge about the worstcase response time of tasks is of utmost importance. Such systems often consist of subsystems that comprise of a collection of tasks, called transactions, which are triggered by external events. We adapt a well known response time analysis to analyze asynchronous task sets where subsets may be triggered from different clock references. Therefore we refine the original computational model from the literature to capture the information about transaction clock references. To determine the schedulability of the system we first analyze all task subsets which are triggered by the same clock reference. Then we combine the results to derive the response times for the complete task set. The approach incorporates no overestimation of the response times and therefore represets a necessary and sufficient schedulability test for such systems. The computational complexity of the presented approach is O(nm) with n being the number of tasks and m the number of clock references in the system. We apply the analysis to a real-world scenario from the automotive safety domain to confirm the computational feasibility and validity of the analysis in real-world systems.

关键词： Equations

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Discrete Event Simulation and Analysis of Timing Problems in Automotive Embedded Systems

Discrete Event Simulation and Analysis of Timing Problems in...

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Annual IEEE International Systems Conference

作者： Christoph Lauer Reinhard German Jens Pollmer Department of Computer Science 7 Computer Networks and Communication Systems University of Erlangen-Nuremberg Department of Safety Electronics Audi AG Ingolstadt

ISBN: (纸本)9781424458820

Designing integrated electronic control units (ECU) in the automotive domain is challenging especially when legacy sub-systems are involved. Nevertheless, important design decisions have to be made at early design stages when some performance parameters of new sub-systems may not be validated yet. To account for uncertainty in the system development we use statistical modeling and discrete event simulation to perform sensitivity analysis from an average-case perspective. Average-case analysis is useful if performance aspects during normal system operation are of interest. The simulation model we implemented enables us to conduct holistic sensitivity analyses of systems consisting of multiple controllers, field-busses, sensors, actors, and applications. Applications are modeled as signal chains traversing the system model experiencing delay in each node along the predefined path. We present the strength of our approach by analyzing the latency of a distributed application in case of an asynchronous, synchronous, and event-triggered integrated ECU context. The results show that clock drift may result in high signal latencies in asynchronous ECUs and synchronous ECUs are superior in terms of signal latency and jitter. Event-triggered ECUs have to be designed carefully and come with trade-offs between performance of the legacy system and new applications.

关键词： Discrete event simulation Timing Automotive engineering Embedded system Delay Sensitivity analysis Uncertainty Performance analysis Analytical models Sensor systems and applications

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Performance Evaluation of Network Mobility Handover over Future Aeronautical Data Link

Performance Evaluation of Network Mobility Handover over Fut...

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2010 IEEE Global Telecommunications Conference GLOBECOM 2010

作者： Serkan Ayaz Felix Hoffmann Christoph Sommer Reinhard German Falko Dressler Institute of Communications and Navigation German AeroSpace Center Wessling Germany Computer Networks and Communication Systems Department of Computer Science University of Erlangen Germany

The aviation community is currently working on the standardization of data communication systems for the future air traffic management. In this context, the ICAO and EUROCONTROL are working on the standardization of IP-based aeronautical telecommunications network and future radio access technologies, respectively. With this work, for the first time, we integrate L-DACS 1, which is one candidate for future radio access technologies, with realistic IP-based network layer functionality and analyze the handover delay performance. We first investigate the effect of link layer retransmissions on handover delay performance. We realized that for regions with low signal-to-noise ratio (BER of 1e-3), link layer retransmissions improve the total handover delay (layer 2 and 3) by about 80%. Considering regions with high signal-to-noise ratio (BER of 1e-5), the benefit of link layer retransmissions becomes negligible due to the reduced number of packet losses. During our analysis, we notice frequent transmission of router advertisement messages causing significant overhead on L-DACS 1 and propose two approaches in order to decrease the overhead to an acceptable range. In the last section, we tackle the increase in handover delay due to a limited number of return link resource request opportunities in congested cells.

关键词： Delay Bit error rate Automatic repeat request Proposals Protocols Mobile communication Resource management

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Schedulability Analysis in Time-Triggered Automotive Real-Time Systems

Schedulability Analysis in Time-Triggered Automotive Real-Ti...

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IEEE Conference on Vehicular Technology (VTC)

作者： Christoph Lauer Kai-Steffen Hielscher Reinhard German Jens Pollmer Department of Computer Science 7 Computer Networks and Communication Systems University of Erlangen Nuremberg Germany Department of Safety Electronics AUDI AG Ingolstadt Germany

In embedded automotive real-time systems correct timing is required to effectively implement distributed applications, time-triggered communication, and integration of intelligent safety applications. We use formal schedulability analysis to validate the task timing for asynchronous real-time systems in an automotive context. Restricting the computational model to purely time-triggered task activation and applying application specific constraints enables us to perform exact response time analyses without pessimism. The analysis can be done efficiently since our computational model drastically limits the number of critical instant candidates to be considered for the worst-case scenario. Simulation results show that the original computational model incorporates a significant amount of response time overestimation and a high computational workload. The presented method can be applied in early design stages as well as in series development and helps to reduce development risks for electronic control units and embedded telematic systems.

关键词： Computational modeling Real time systems Context Time factors Automotive engineering Analytical models Clocks

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Constellation Design for Odd-Bit Quadrature Amplitude Modulation

Constellation Design for Odd-Bit Quadrature Amplitude Modula...

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IEEE Wireless communications and Networking Conference Workshops (WCNCW)

作者： Yiling Wu Yuping Zhao Hongbin Li State Key Laboratory of Advanced Optical Communication Systems & Networks School of Electronics Engineering and Computer Science Peking University Beijing China

ISBN: (纸本)9781424464050;9781424464067

In this paper, we study the constellation design of quadrature amplitude modulations (QAMs) with odd number of bits per symbol. A square constellation, which adopts symmetrical Gray labeling, is proposed. Simplified mapping and demapping methods are also designed for it. Performance of the proposed square constellation is compared with that of conventional rectangular and cross constellations. As simulation results show, the proposed square constellation obtains better BER performance when channel coding is used in communication systems. Moreover, it achieves much lower realization complexity than cross constellation by using the proposed mapping and demapping method.

关键词： Quadrature amplitude modulation Labeling Peak to average power ratio Bit error rate Design methodology Channel coding Frequency estimation Optical design Laboratories Optical fiber communication

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Truly random number generation based on measurement of phase noise of a laser

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Physical Review E 2010年第5期81卷 051137-051137页

作者： Hong Guo Wenzhuo Tang Yu Liu Wei Wei CREAM Group State Key Laboratory of Advanced Optical Communication Systems and Networks (Peking University) and Institute of Quantum Electronics School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

We present a simple approach to realize truly random number generator based on measuring the phase noise of a single-mode vertical cavity surface emitting laser. The true randomness of the quantum phase noise originates from the spontaneous emission of photons and the random bit generation rate is ultimately limited only by the laser linewidth. With the final bit generation rate of 20 Mbit/s, the truly random bit sequence guaranteed by the uncertainty principle of quantum mechanics passes the three standard randomness tests (ENT, Diehard, and NIST Statistical Test Suites). Moreover, a continuously generated random bit sequence, with length up to 14 Gbit, is verified by two additional criteria for its true randomness.

关键词： Phase noise

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