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1
Mallet, Frédéric. "Clock constraint specification language: specifying clock constraints with UML/MARTE." Innovations in Systems and Software Engineering 4, no. 3 (August 9, 2008): 309–14. http://dx.doi.org/10.1007/s11334-008-0055-2.
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Dai, Xiaolei, Yidong Lou, Zhiqiang Dai, Caibo Hu, Yaquan Peng, Jing Qiao, and Chuang Shi. "Precise Orbit Determination for GNSS Maneuvering Satellite with the Constraint of a Predicted Clock." Remote Sensing 11, no. 16 (August 20, 2019): 1949. http://dx.doi.org/10.3390/rs11161949.
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Precise orbit products are essential and a prerequisite for global navigation satellite system (GNSS) applications, which, however, are unavailable or unusable when satellites are undertaking maneuvers. We propose a clock-constrained reverse precise point positioning (RPPP) method to generate the rather precise orbits for GNSS maneuvering satellites. In this method, the precise clock estimates generated by the dynamic precise orbit determination (POD) processing before maneuvering are modeled and predicted to the maneuvering periods and they constrain the RPPP POD during maneuvering. The prediction model is developed according to different clock types, of which the 2-h prediction error is 0.31 ns and 1.07 ns for global positioning system (GPS) Rubidium (Rb) and Cesium (Cs) clocks, and 0.45 ns and 0.60 ns for the Beidou navigation satellite system (BDS) geostationary orbit (GEO) and inclined geosynchronous orbit (IGSO)/Median Earth orbit (MEO) satellite clocks, respectively. The performance of this proposed method is first evaluated using the normal observations without maneuvers. Experiment results show that, without clock-constraint, the average root mean square (RMS) of RPPP orbit solutions in the radial, cross-track and along-track directions is 69.3 cm, 5.4 cm and 5.7 cm for GPS satellites and 153.9 cm, 12.8 cm and 10.0 cm for BDS satellites. When the constraint of predicted satellite clocks is introduced, the average RMS is dramatically reduced in the radial direction by a factor of 7–11, with the value of 9.7 cm and 13.4 cm for GPS and BDS satellites. At last, the proposed method is further tested on the actual GPS and BDS maneuver events. The clock-constrained RPPP POD solution is compared to the forward and backward integration orbits of the dynamic POD solution. The resulting orbit differences are less than 20 cm in all three directions for GPS satellite, and less than 30 cm in the radial and cross-track directions and up to 100 cm in the along-track direction for BDS satellites. From the orbit differences, the maneuver start and end time is detected, which reveals that the maneuver duration of GPS satellites is less than 2 min, and the maneuver events last from 22.5 min to 107 min for different BDS satellites.
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Huang, Wei, Pascale Defraigne, Giovanna Signorile, and Ilaria Sesia. "Improved Multi-GNSS PPP Software for Upgrading the DEMETRA Project Time Monitoring Service." Sensors 19, no. 20 (October 11, 2019): 4389. http://dx.doi.org/10.3390/s19204389.
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The H2020 DEMETRA project provides short latency clock monitoring services to the time users using the Atomium precise point positioning (PPP) software developed by the Royal Observatory of Belgium. In this paper, three recent updates of the current Atomium software are introduced: adding Galileo signals in the PPP computation; the option to constrain the receiver clock; PPP with integer ambiguity resolution. The advantages of these updates are demonstrated: Combining the Galileo and global positioning system (GPS) signals for PPP time transfer will further improve the frequency stability inside the computation batch; PPP with receiver clock constraint is not only used to reduce the short-term noise of the clock measurements but can also be used for some specific applications to a keep continuous clock solution in the computation batch or retrieve correct clock measurements from extremely noisy environments; the integer PPP allows a continuous clock solution, and improves the mid-term and long-term stability of the frequency transfer compared to the current PPP frequency transfer techniques.
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Wu, Xiu Long, Zhi Ting Lin, Jian Meng, and Jun Ning Chen. "Process Antenna Effect Elimination in Ultra Deep Submicron." Applied Mechanics and Materials 229-231 (November 2012): 1519–22. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.1519.
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This paper analyzes the mechanism of process antenna effect in ultra deep submicron IC physical design and provides the antenna ratio calculation method. A new elimination method of process antenna effect combined with clock tree synthesis is proposed. The elimination method minimizes the impact to the clock latency and clock skew by setting up reasonable constraint for clock tree synthesize. Finally, the elimination method is used during place and route of the physical design of a reconfigurable video decoder chip, which is based on TSMC 65nm low power technology. The proposed method eliminates the process antenna effect of the design effectively, also minimizes the impact to clock tree and chip timing to the least.
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Qin, Weijin, Yulong Ge, Pei Wei, and Xuhai Yang. "An Approach to a Clock Offsets Model for Real-Time PPP Time and Frequency Transfer During Data Discontinuity." Applied Sciences 9, no. 7 (April 3, 2019): 1405. http://dx.doi.org/10.3390/app9071405.
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To resolve the dilemma in any post-processing strategy, i.e., the difficulty of monitoring the real-time time and frequency signals in a timely manner, real-time GPS time and the frequency transfer have recently become trending topics. Unfortunately, data interruption occurs when conducting real-time time transfer, sometimes from unexpected reasons. In this study, to ensure the stability and precision of real-time time transfer, an adaptive prediction model and a between-epoch constraint receiver clock model are applied as the mathematic models. The purpose of prediction is to solve the ambiguity from re-convergence when the data reappear. Moreover, compared to the conventional method, the between-epoch constraint receiver clock model is employed in this study to consider the correlation of epoch-wise clock parameters to avoid wasting useful information. The simulation data and real data are compared to verify the performance of the new approach. The simulation data for 165 days are designed with random daily interruptions of 10, 30, 60 and 90 min. Real data from 12 days is captured from the incomplete data in routine observation records. Ignoring the simulation data and real data, the investigation of six stations shows that the results with the between-epoch constraint receiver clock model were smoother than those with a white noise model. With an adaptive prediction model and the between-epoch constraint receiver clock model, the simulation results illustrate that the average root mean squares (RMS) values of all the stations are significantly reduced, i.e., by 66.03% from 0.43 to 0.14 ns, by 64.91% from 0.44 to 0.15 ns, by 57.47% from 0.43 to 0.18 ns, and by 51.67% from 0.44 to 0.21 ns for the 10, 30, 60 and 90 min data interruptions, respectively. The stability of all the stations is improved by at least 50%. The improvement increases to 100% for short-term stability. The real results show that the stability of four links is boosted by at least 5%. The model proposed in this paper is more effective in producing short-term stability than long-term stability.
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Krabbenhoft, T. J., and T. F. Turner. "Clock Gene Evolution: Seasonal Timing, Phylogenetic Signal, or Functional Constraint?" Journal of Heredity 105, no. 3 (February 20, 2014): 407–15. http://dx.doi.org/10.1093/jhered/esu008.
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YONEDA, T., K. MASUDA, and H. FUJIWARA. "Test Scheduling for Multi-Clock Domain SoCs under Power Constraint." IEICE Transactions on Information and Systems E91-D, no. 3 (March 1, 2008): 747–55. http://dx.doi.org/10.1093/ietisy/e91-d.3.747.
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Mallet, Frédéric, Julien DeAntoni, Charles André, and Robert de Simone. "The clock constraint specification language for building timed causality models." Innovations in Systems and Software Engineering 6, no. 1-2 (December 22, 2009): 99–106. http://dx.doi.org/10.1007/s11334-009-0109-0.
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Ramanna, S., and J. F. Peters. "Explicit clock temporal logic in constraint checking for real-time systems *." IFAC Proceedings Volumes 24, no. 10 (September 1991): 47–58. http://dx.doi.org/10.1016/b978-0-08-041698-4.50013-5.
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Keiser, Jane M., and Diana V. Lambdin. "The Clock Is Ticking: Time Constraint Issues in Mathematics Teaching Reform." Journal of Educational Research 90, no. 1 (September 1996): 23–31. http://dx.doi.org/10.1080/00220671.1996.9944440.
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Ramanna, S., and J. F. Peters. "Explicit clock temporal logic in constraint checking for real-time systems." Annual Review in Automatic Programming 16 (January 1991): 47–58. http://dx.doi.org/10.1016/0066-4138(91)90009-z.
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Zhou, Jiang, Chen, Li, and Liu. "Improving the GRACE Kinematic Precise Orbit Determination Through Modified Clock Estimating." Sensors 19, no. 19 (October 8, 2019): 4347. http://dx.doi.org/10.3390/s19194347.
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Utilizing global positioning system (GPS) to determine the precise kinematic orbits for the twin satellites of the Gravity Recovery and Climate Experiment (GRACE) plays a very important role in the earth’s gravitational and other scientific fields. However, the orbit quality is highly depended on the geometry of observed GPS satellites. In this study, we propose a kinematic orbit determination method for improving the GRACE orbit quality especially when the geometry of observed GPS satellites is weak, where an appropriate random walk clock constraint between adjacent epochs is recommended according to the stability of on-board GPS receiver clocks. GRACE data over one month were adopted in the experimental validation. Results show that the proposed method could improve the root mean square (RMS) by 20–40% in radial component and 5–20% in along and cross components. For those epochs with position dilution of precision (PDOP) larger than 4, the orbits were improved by 50–70% in radial component and 17–50% in along and cross components. Meanwhile, the Allan deviation of clock estimates in the proposed method was much closer to the reported Allan deviation of GRACE on-board oscillator. All the results confirmed the improvement of the proposed method.
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Woo, Jeongmin, David L. Robertson, and Simon C. Lovell. "Constraints on HIV-1 Diversity from Protein Structure." Journal of Virology 84, no. 24 (September 29, 2010): 12995–3003. http://dx.doi.org/10.1128/jvi.00702-10.
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ABSTRACT The high rate of HIV-1 evolution contributes to immune escape, enables the virus to escape drug therapy, and may underlie the difficulty of producing an effective vaccine. Identifying constraints on HIV evolution is therefore of prime importance. To investigate this problem, we examined the relationships between sequence diversity, selection, and protein structure. We found that while there was an increase in sequence diversity over time, this variation had a tendency to be limited to specific structural regions. When individual sites were analyzed, there was, in contrast, substantial and widespread evolutionary constraint over gag and env. This constraint was present even in the highly variable envelope proteins. The evolutionary significance of an individual site is indicated by the change in selection pressure along the time course: increasing entropy indicates that the site is evolving predominantly in a more “clock”-like manner, low entropy values with no increase indicate a high degree of constraint, and high entropy values indicate a lack of constraint. Few sites display high degrees of turnover. Mapping these sites onto the three-dimensional protein structure, we found a significant difference between evolutionary rates for regions buried in the core of the protein and those on the surface. This constraint did not change over the time period analyzed and was not subtype dependent, as similar results were found for subtypes B and C. This link between sequence and structure not only demonstrates the limits of recent HIV-1 evolution but also highlights the origins of evolutionary constraint on viral change.
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Lee, Taehee, David Z. Pan, and Joon-Sung Yang. "Clock Network Optimization With Multibit Flip-Flop Generation Considering Multicorner Multimode Timing Constraint." IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems 37, no. 1 (January 2018): 245–56. http://dx.doi.org/10.1109/tcad.2017.2698025.
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BISTARELLI, STEFANO, MAURIZIO GABBRIELLI, MARIA CHIARA MEO, and FRANCESCO SANTINI. "Timed soft concurrent constraint programs: An interleaved and a parallel approach." Theory and Practice of Logic Programming 15, no. 6 (June 6, 2014): 743–82. http://dx.doi.org/10.1017/s1471068414000106.
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AbstractWe propose a timed and soft extension of Concurrent Constraint Programming. The time extension is based on the hypothesis ofbounded asynchrony: The computation takes a bounded period of time and is measured by a discrete global clock. Action prefixing is then considered as the syntactic marker that distinguishes a time instant from the next one. Supported by soft constraints instead of crisp ones,tellandaskagents are now equipped with a preference (or consistency) threshold, which is used to determine their success or suspension. In this paper, we provide a language to describe the agents' behavior, together with its operational and denotational semantics, for which we also prove the compositionality and correctness properties. After presenting a semantics using maximal parallelism of actions, we also describe a version for their interleaving on a single processor (with maximal parallelism for time elapsing). Coordinating agents that need to take decisions on both preference values and time events may benefit from this language.
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DE CICCO, HERNÁN, and CLAUDIO SIMEONE. "GAUGE INVARIANCE OF PARAMETRIZED SYSTEMS AND PATH INTEGRAL QUANTIZATION." International Journal of Modern Physics A 14, no. 32 (December 30, 1999): 5105–20. http://dx.doi.org/10.1142/s0217751x99002414.
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Gauge invariance of systems whose Hamilton–Jacobi equation is separable is improved by adding surface terms to the action functional. The general form of these terms is given for some complete solutions of the Hamilton–Jacobi equation. The procedure is applied to the relativistic particle and toy universes, which are quantized by imposing canonical gauge conditions in the path integral; in the case of empty models, we first quantize the parametrized system called "ideal clock," and then we examine the possibility of obtaining the amplitude for the minisuperspaces by matching them with the ideal clock. The relation existing between the geometrical properties of the constraint surface and the variables identifying the quantum states in the path integral is discussed.
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Jeon, Jin-Kwan, In-Won Hwang, Hyun-Jun Lee, and Younho Lee. "Improving the Performance of RLizard on Memory-Constraint IoT Devices with 8-Bit ATmega MCU." Electronics 9, no. 9 (September 22, 2020): 1549. http://dx.doi.org/10.3390/electronics9091549.
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We propose an improved RLizard implementation method that enables the RLizard key encapsulation mechanism (KEM) to run in a resource-constrained Internet of Things (IoT) environment with an 8-bit micro controller unit (MCU) and 8–16 KB of SRAM. Existing research has shown that the proposed method can function in a relatively high-end IoT environment, but there is a limitation when applying the existing implementation to our environment because of the insufficient SRAM space. We improve the implementation of the RLizard KEM by utilizing electrically erasable, programmable, read-only memory (EEPROM) and flash memory, which is possessed by all 8-bit ATmega MCUs. In addition, in order to prevent a decrease in execution time related to their use, we improve the multiplication process between polynomials utilizing the special property of the second multiplicand in each algorithm of the RLizard KEM. Thus, we reduce the required MCU clock cycle consumption. The results show that, compared to the existing code submitted to the National Institute of Standard and Technology (NIST) PQC standardization competition, the required MCU clock cycle is reduced by an average of 52%, and the memory used is reduced by approximately 77%. In this way, we verified that the RLizard KEM works well in our low-end IoT environments.
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Liu, Junhong, Defeng Gu, Bing Ju, Yuwang Lai, and Dongyun Yi. "Relative clock estimation method between two LEO satellites with a double-difference solution constraint." Acta Astronautica 109 (April 2015): 34–41. http://dx.doi.org/10.1016/j.actaastro.2014.12.014.
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Shi, Junbo, and Yang Gao. "A Troposphere Constraint Method To Improve PPP Ambiguity-Resolved Height Solution." Journal of Navigation 67, no. 2 (October 8, 2013): 249–62. http://dx.doi.org/10.1017/s0373463313000647.
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Integer ambiguity resolution is able to improve positioning accuracy and reduce convergence time in Precise Point Positioning (PPP). Although significantly improved horizontal positioning accuracy has been demonstrated, the height solution improvement is found to be less significant, and improving this requires further investigation. In this paper, a troposphere constraint method using precise troposphere corrections is proposed to improve the PPP ambiguity-resolved height solution. This is different from the conventional approach that typically applies meteorological data to calculate the a priori troposphere delay and estimates the residual troposphere delay. The effects of the troposphere delay on PPP ambiguity-resolved height solutions are first studied. Numerical analysis is conducted to ambiguity-resolved positioning results based on the decoupled clock model and hourly Global Positioning System (GPS) observations from a Canadian PPP-inferred troposphere precipitable water vapour system. The results show that by using the proposed method the PPP ambiguity-resolved height accuracy can be further improved to 3·86 cm compared to 5·32 cm using the conventional approach.
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Tajmar, Martin, and Lance L. Williams. "An Experimental Test of the Classical Interpretation of the Kaluza Fifth Dimension." Physics 2, no. 4 (October 22, 2020): 587–95. http://dx.doi.org/10.3390/physics2040033.
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Kaluza was the first to realize that the four-dimensional gravitational field of general relativity and the classical electromagnetic field behave as if they were components of a five-dimensional gravitational field. We present a novel experimental test of the macroscopic classical interpretation of the Kaluza fifth dimension. Our experiment design probes a key feature of Kaluza unification—that electric charge is identified with motion in the fifth dimension. Therefore, we tested for a time dilation effect on an electrically charged clock. This test can also be understood as a constraint on time dilation from a constant electric potential of any origin. This is only the second such test of time dilation under electric charge reported in the literature, and a null result was obtained here. We introduce the concept of a charged clock in the Kaluza context, and discuss some ambiguities in its interpretation. We conclude that a classical, macroscopic interpretation of the Kaluza fifth dimension may require a timelike signature in the five-dimensional metric, and the associated absence of a rest frame along the fifth coordinate.
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Zhang, Min, and Yunhui Ying. "Towards SMT-based LTL model checking of clock constraint specification language for real-time and embedded systems." ACM SIGPLAN Notices 52, no. 5 (September 14, 2017): 61–70. http://dx.doi.org/10.1145/3140582.3081035.
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Ding, You, and Xiangdong Zhang. "(2+1)-dimensional loop quantum cosmology of Bianchi I models." International Journal of Modern Physics A 35, no. 29 (October 20, 2020): 2050185. http://dx.doi.org/10.1142/s0217751x20501857.
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We study the anisotropic Bianchi I loop quantum cosmology in [Formula: see text] dimensions. The [Formula: see text] scheme is considered in the present paper and the following expected results are established: (i) the massless scalar field again play the role of emergent time variables and serves as an internal clock; (ii) by imposing the fundamental discreteness of length operator, the total Hamiltonian constraint is obtained and gives rise the evolution as a difference equation; and (iii) the exact solutions of Friedmann equation are constructed rigorously for both classical and effective level. The investigation extends the domain of validity of loop quantum cosmology to beyond the four dimensions.
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Pérez-Miranda, Fabian, Omar Mejia, Benjamín López, and Oldřich Říčan. "Molecular clocks, biogeography and species diversity in Herichthys with evaluation of the role of Punta del Morro as a vicariant brake along the Mexican Transition Zone in the context of local and global time frame of cichlid diversification." PeerJ 8 (April 29, 2020): e8818. http://dx.doi.org/10.7717/peerj.8818.
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Using molecular dated phylogenies and biogeographic reconstructions, the species diversity, biogeography and time frame of evolution of the genus Herichthys were evaluated. In particular, we test the role of Punta del Morro (PdM) as a vicariant brake along the Mexican Transition Zone in the context of local and global time frame of cichlid diversification using several sets of calibrations. Species diversity in Herichthys is complex and the here employed dating methods suggest young age and rapid divergence for many species while species delimitation methods did not resolve these young species including both sympatric species pairs. Based on our molecular clock dating analyses, Herichthys has colonized its present distribution area significantly prior to the suggested vicariance by PdM (10–17.1 Ma vs. 5 to 7.5 Ma). The PdM constraint is in conflict with all other paleogeographic and fossil constraints including novel ones introduced in this study that are, however, congruent among each other. Our study demonstrates that any cichlid datings significantly older or younger than the bounds presented by our analyses and discussion have to be taken as highly questionable from the point of view of Middle American paleogeography and cichlid biogeography unless we allow the option that cichlid biogeography is completely independent from ecological and geological constraints.
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Satoh, Yoko, Hiroshi Kawai, Naomi Kudo, Yoichi Kawashima, and Atsushi Mitsumoto. "Time-restricted feeding entrains daily rhythms of energy metabolism in mice." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 290, no. 5 (May 2006): R1276—R1283. http://dx.doi.org/10.1152/ajpregu.00775.2005.
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Energy metabolism, oxygen consumption rate (V̇o2), and respiratory quotient (RQ) in mice were monitored continuously throughout 12:12-h light-dark cycles before, during, and after time-restricted feeding (RF). Mice fed ad libitum showed robust daily rhythms in both parameters: high during the dark phase and low during the light phase. The daily profile of energy metabolism in mice under daytime-only feeding was reversed at the beginning of the first fasting night. A few days after daytime-only feeding began, RF also reversed the circadian core body temperature rhythm. Moreover, RF for 6 consecutive days shifted the phases of circadian expression patterns of clock genes in liver significantly by 8–10 h. When mice were fed a high-fat (HF) diet ad libitum, the daily rhythm of RQ dampened day by day and disappeared on the sixth day of RF, whereas V̇o2 showed a robust daily rhythm. Mice fed HF only in the daytime had reversed V̇o2 and RQ rhythms. Similarly, mice fed HF only in the daytime significantly phase shifted the clock gene expression in liver, whereas ad libitum feeding with HF had no significant effect on the expression phases of liver clock genes. These results suggested that V̇o2 is a sensitive indicator of entrainment in the mouse liver. Moreover, physiologically, it can be determined without any surgery or constraint. On the basis of these results, we hypothesize that a change in the daily V̇o2 rhythm, independent of the energy source, might drive phase shifts of circadian oscillators in peripheral tissues, at least in the liver.
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Kardian, Aqwam Rosadi, Sunny Arief Sudiro, and Sarifuddin Madenda. "Efficient Implementation of Mean, Variance and Skewness Statistic Formula for Image Processing Using FPGA Device." Bulletin of Electrical Engineering and Informatics 7, no. 3 (September 1, 2018): 386–92. http://dx.doi.org/10.11591/eei.v7i3.687.
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Processing statistic formula in image processing and accessing data from memory is easy in software, the other hand for hardware implementation is more dificult considering a lot of constraint. This article proposes an implementation of optimum mean, variance and skewness formula in FGPA Device. The proposed circuit design for all formulas only need three additions component (in three accumulators) and two divisions using two shift-right-registers, two subtractors, one adder and six multipliers. For 8x8 image size need 64 clock cycles to finish the mean, variance and skewness calculations, comparing other approach that need more than 1024 additions component without skewness calculation. Implementation into FPGA needs 68 slices of flip-flops and 121 of 4 input LUTs.
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Moriyama, E. N., and T. Gojobori. "Rates of synonymous substitution and base composition of nuclear genes in Drosophila." Genetics 130, no. 4 (April 1, 1992): 855–64. http://dx.doi.org/10.1093/genetics/130.4.855.
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Abstract We compared the rates of synonymous (silent) substitution among various genes in a number of species of Drosophila. First, we found that even for a particular gene, the rate of synonymous substitution varied considerably with Drosophila lineages. Second, we showed a large variation in synonymous substitution rates among nuclear genes in Drosophila. These rates of synonymous substitution were correlated negatively with C content and positively with A content at the third codon positions. Nucleotide sequences were also compared between pseudogenes and their functional homologs. The C content of the pseudogenes was lower than that of the functional genes and the A content of the former was higher than that of the latter. Because the synonymous substitution for functional genes and the nucleotide substitution for pseudogenes are exempted from any selective constraint at the protein level, these observations could be explained by a biased pattern of mutation in the Drosophila nuclear genome. Such a bias in the mutation pattern may affect the molecular clock (local clock) of each nuclear gene of each species. Finally, we obtained the average rates of synonymous substitution for three gene groups in Drosophila; 11.0 x 10(-9), 17.5 x 10(-9) and 27.1 x 10(-9)/site/year.
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ANDREEV, BORIS, EDWARD L. TITLEBAUM, and EBY G. FRIEDMAN. "SIZING CMOS INVERTERS WITH MILLER EFFECT AND THRESHOLD VOLTAGE VARIATIONS." Journal of Circuits, Systems and Computers 15, no. 03 (June 2006): 437–54. http://dx.doi.org/10.1142/s0218126606003143.
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The maximum speed of synchronous circuits is generally constrained by the worst case propagation delay, which limits the system clock frequency. Various techniques exist to manage the circuit delay, trading off speed for other system resources. One such approach is to equalize the rise and fall delay times. The primary design parameter for equalizing these delay times is the ratio between the width of the PMOS and NMOS transistors, which determines the relationship between the currents passed along the pull-up and pull-down paths. The variation of the pull-up to pull-down ratio for different circuit parameters is discussed in this paper under the constraint of equal rise and fall delay times. It is shown that the short-circuit current and the Miller capacitance affect the ideal linear relationship between the CMOS inverter delay times and the load capacitance, requiring the pull-up to pull-down ratio to be adjusted as circuit parameters are varied. These effects are more pronounced in deep submicrometer technologies with significant parasitic MOSFET capacitances and threshold voltage variations. Based on analytic and experimental observations, circuit design guidelines are proposed to minimize the Miller effect.
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Wang, Jinyong, Zhiqiu Huang, Xiaowei Huang, Yi Zhu, and Fei Wang. "Multiclock Constraint System Modelling and Verification for Ensuring Cooperative Autonomous Driving Safety." Journal of Advanced Transportation 2020 (December 5, 2020): 1–24. http://dx.doi.org/10.1155/2020/8830752.
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CADS (cooperative autonomous driving systems) are software-intensive and safety-critical reactive systems and give great promise to our daily life, but system errors may not be identified in the design stage until the implement stage, and the cost to correct them will be more expensive later than the early stage. For designing trustworthy autonomous software systems, we have to deal with multiclock constraint models. SysML (System Modeling Language) meets increasing adoption in order to carry out system-level modelling and verification against abstract representations, but it suffers from semantic ambiguities in the design of safety-critical autonomous systems. The main objective is to investigate methods for coping with the design and analysis models simultaneously and to achieve semantic consistency based on mathematical foundations and formal model transformation. In this paper, we propose a method to combine the requirement modelling process with analysis process together for CADS safety and reliability guarantee. Firstly, we extend SysML metamodels and construct SysML profile for the CADS domain that could improve modelling correctness and enhance reusability. An instantiated CADS model has been designed by means of adopting a profile containing different key functional and nonfunctional attributes and behaviors. Secondly, we define formal syntax and semantic notations for modelling elements in the SysML state machine diagram and show transformation rules between the state machine diagram and the CCSL (Clock Constraint Specification Language) model. Semantic preservation is also proved using the bisimulation relation between them for rigorous mapping correctness. Thirdly, a cooperative autonomous overtaking driving case study on the highway scenario is used for illustration, and we use the tool TimeSquare to simulate CCSL specification execution traces at the system design stage.
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sriraman, Harini, and Pattabiraman Venkatasubbu. "SeRA: Self-Repairing Architecture for Dark Silicon Era." Journal of Circuits, Systems and Computers 29, no. 04 (June 13, 2019): 2050053. http://dx.doi.org/10.1142/s021812662050053x.
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The lifetime reliability of processors has become a major design constraint in the dark silicon era. Processor reliability issues are mainly due to design defects and aging. Unlike design defects, however, aging faults gradually accumulate over time. Many methods have recently been proposed to monitor the performance degradation of circuits. In this study, an architectural solution that extends the circuit-level age monitoring to processor stages is proposed for monitoring performance degradation. When degradation of a stage quantified as delay of half of the reference clock occurs, a self-repairing mechanism is triggered. This mechanism configures an field programmable gate array (FPGA), which takes over the functions of the degraded unit. The proposed self-repairing mechanism is applied to the stages of the processor data-path. This method (SeRA) has lesser area overhead compared with the state-of-art solutions.
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Greggio, Laura, Paolo Simonetti, and Francesca Matteucci. "On the delay times of merging double neutron stars." Monthly Notices of the Royal Astronomical Society 500, no. 2 (October 27, 2020): 1755–71. http://dx.doi.org/10.1093/mnras/staa3312.
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ABSTRACT The merging rate of double neutron stars (DNS) has a great impact on many astrophysical issues, including the interpretation of gravitational waves signals, of the short gamma-ray bursts (GRBs), and of the chemical properties of stars in galaxies. Such rate depends on the distribution of the delay times (DDT) of the merging events. In this paper, we derive a theoretical DDT of merging DNS following from the characteristics of the clock controlling their evolution. We show that the shape of the DDT is governed by a few key parameters, primarily the lower limit and the slope of the distribution of the separation of the DNS systems at birth. With a parametric approach, we investigate on the observational constraints on the DDT from the cosmic rate of short GRBs and the europium-to-iron ratio in Milky Way stars, taken as tracer of the products of the explosion. We find that the local rate of DNS merging requires that $\sim \! 1 {{\ \rm per\ cent}}$ of neutron stars progenitors live in binary systems which end their evolution as merging DNS within a Hubble time. The redshift distribution of short GRBs does not yet provide a strong constraint on the shape of the DDT, although the best-fitting models have a shallow DDT. The chemical pattern in Milky Way stars requires an additional source of europium besides the products from merging DNS, which weakens the related requirement on the DDT. At present both constraints can be matched with the same DDT for merging DNS.
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Suh, Eun Suk, Kaushik Sinha, and Jaemyung Ahn. "Multi-attribute optimization-based system decomposition considering several value chain stakeholder perspectives." Research in Engineering Design 31, no. 4 (July 16, 2020): 411–28. http://dx.doi.org/10.1007/s00163-020-00342-9.
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Abstract The final architecture of a complex system reflect preferences of several value chain stakeholders on system attributes, also called “ilities”. Owing to differences in their individual roles and responsibilities, different stakeholders prefer different approaches to architect and decompose a system to optimize their attributes of interest. However, owing to increasing complexity of modern engineering systems, optimizing multiple attributes of complex systems has become challenging; moreover, very few researches have been published in this regard. Thus, to address this gap in available literature, this paper presents a multi-attribute optimization framework for complex system decomposition. The proposed framework primarily optimizes two attributes—system robustness (to the perspective of the stakeholder), and modularity—while system maintainability is considered an optimization constraint. Feasibility of the proposed framework has been demonstrated through a case study, wherein system attributes of three different mechanical clock models having different architectures were optimized.
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Zhang, Li Hua, Li Ping Zhang, and Er Fei Bai. "Generalized Elliptic Curve Digital Signature Chain Based Authentication and Key Agreement Scheme." Advanced Materials Research 108-111 (May 2010): 1503–8. http://dx.doi.org/10.4028/www.scientific.net/amr.108-111.1503.
Full textAbstract:
Recently, several one time password authentication schemes have been proposed. However, most one-time password authentication schemes have security flaws. In this paper, a novel one-time password authentication and key agreement scheme (EAKAS) based on elliptic curve digital signature chain is developed. The proposed scheme has the following merits password or verification table is not required in the server; users can choose or change password; it can resist off-line dictionary attacks and achieves mutual authentication; it has no system clock synchronization and no constraint of transmission delay; it can resist replay attacks, man-in-the-middle attack and insider attack; it is sensitive to password error and strong in security restoration; the session keys in proposed scheme have the feature of freshness, confidentiality, known key security and forward security. Compared with the related schemes, our proposed scheme has better security and well suited to scenarios requiring a high level security.
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Trajanovski, S., C. Albrecht, K. Schreiber, R. Schultheiß, T. Stadler, M. Benke, and T. Wilke. "Testing the spatial and temporal framework of speciation in an ancient lake species flock: the leech genus <i>Dina</i> (Hirudinea: Erpobdellidae) in Lake Ohrid." Biogeosciences 7, no. 11 (November 3, 2010): 3387–402. http://dx.doi.org/10.5194/bg-7-3387-2010.
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Abstract. Ancient Lake Ohrid on the Balkan Peninsula is considered to be the oldest ancient lake in Europe with a suggested Plio-/Pleistocene age. Its exact geological age, however, remains unknown. Therefore, molecular clock data of Lake Ohrid biota may serve as an independent constraint of available geological data, and may thus help to refine age estimates. Such evolutionary data may also help unravel potential biotic and abiotic factors that promote speciation events. Here, mitochondrial sequencing data of one of the largest groups of endemic taxa in the Ohrid watershed, the leech genus Dina, is used to test whether it represents an ancient lake species flock, to study the role of potential horizontal and vertical barriers in the watershed for evolutionary events, to estimate the onset of diversification in this group based on molecular clock analyses, and to compare this data with data from other endemic species for providing an approximate time frame for the origin of Lake Ohrid. Based on the criteria speciosity, monophyly and endemicity, it can be concluded that Dina spp. from the Ohrid watershed, indeed, represents an ancient lake species flock. Lineage sorting of its species, however, does not seem to be complete and/or hybridization may occur. Analyses of population structures of Dina spp. in the Ohrid watershed indicate a horizontal zonation of haplotypes from spring and lake populations, corroborating the role of lake-side springs, particularly the southern feeder springs, for evolutionary processes in endemic Ohrid taxa. Vertical differentiation of lake taxa, however, appears to be limited, though differences between populations from the littoral and the profundal are apparent. Molecular clock analyses indicate that the most recent common ancestor of extant species of this flock is approximately 1.99 ± 0.83 million years (Ma) old, whereas the split of the Ohrid Dina flock from a potential sister taxon outside the lake is estimated at 8.30 ± 3.60 Ma. Comparisons with other groups of endemic Ohrid species indicated that in all cases, diversification within the watershed started ≤2 Ma ago. Thus, this estimate may provide information on a minimum age for the origin of Lake Ohrid. Maximum ages are less consistent and generally less reliable. But cautiously, a maximum age of 3 Ma is suggested. Interestingly, this time frame of approximately 2–3 Ma ago for the origin of Lake Ohrid, generated based on genetic data, well fits the time frame most often used in the literature by geologists.
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Trajanovski, S., C. Albrecht, K. Schreiber, R. Schultheiß, T. Stadler, M. Benke, and T. Wilke. "Testing the spatial and temporal framework of speciation in an ancient lake species flock: the leech genus <i>Dina</i> (Hirudinea: Erpobdellidae) in Lake Ohrid." Biogeosciences Discussions 7, no. 4 (July 1, 2010): 5011–45. http://dx.doi.org/10.5194/bgd-7-5011-2010.
Full textAbstract:
Abstract. Ancient Lake Ohrid on the Balkan Peninsula is considered to be the oldest ancient lake in Europe with a suggested Plio-Pleistocene age. Its exact geological age, however, remains unknown. Therefore, molecular clock data of Lake Ohrid biota may serve as an independent constraint of available geological data, and may thus also help to refine age estimates. Such evolutionary data may also help unravel potential biotic and abiotic factors that promote speciation events. Here, mitochondrial sequencing data of one of the largest groups of endemic taxa in Lake Ohrid, the leech genus Dina, is used to test whether it represents an ancient lake species flock, to study the role of horizontal and vertical barriers in Lake Ohrid for evolutionary events, to estimate the onset of intralacustrine diversification in this group based on molecular clock analyses, and to compare this data with data from other endemic species for providing an approximate time frame for the origin of Lake Ohrid. Based on the criteria speciosity, monophyly and endemicity, it can be concluded that Lake Ohrid Dina, indeed, represents an ancient lake species flock. Lineage sorting of its species, however, does not seem to be complete. Analyses of population structures of Dina spp. in the Ohrid watershed indicate a horizontal zonation of haplotypes from spring and lake populations, corroborating the role of lake-side springs, particularly the southern feeder springs, for evolutionary processes in endemic Ohrid taxa. Vertical differentiation of lake taxa, however, appears to be limited, though differences between populations from the littoral and the profundal are apparent. Molecular clock analyses indicate that the most recent common ancestor of extant species of this flock is approximately 1.99±0.83 Ma old, whereas the split of the Lake Ohrid Dina flock from a potential sister taxon outside the lake is estimated at 8.30±3.60 Ma. Comparisons with other groups of endemic Ohrid species indicated that in all cases, intralacustrine diversification started ≤2 Ma ago. Thus, this estimate may provide information on a minimum age for the origin of Lake Ohrid. Maximum ages are less consistent and generally less reliable. But cautiously, a maximum age of 3 Ma is suggested. Interestingly, this time frame of approximately 2–3 Ma for the origin of Lake Ohrid, generated based solely on evolutionary data, well fits the time frame most often used in the literature by geologists. Future studies must show whether this concurrence holds true.
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Malik, Luqman Abdul, and Elkaf Rahmawan Pramudya. "IMPLEMENTASI ALGORITMA FUZZY EVOLUSI UNTUK PENGATURAN JADWAL LABORATORIUM KOMPUTER DI SEKOLAH." CCIT Journal 10, no. 2 (August 8, 2017): 207–20. http://dx.doi.org/10.33050/ccit.v10i2.540.
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Problems in the placement of the clock and the use of the computer lab this time wearing schedule which already available, but the use of spaces and their subjects will use laboratory space is not yet available on the schedule of lessons. This is a constraint in the use of computer lab room each day and happens constantly every day and every week. But yet the formation schedule use of a computer lab space evenly for classes which does require a competence in practice the subjects and rely solely on coming first entered in the computer lab. Scheduling the use of the computer lab is expected to obtain a schedule by the number of hours of instruction that are already defined and a timetable of the lessons taught are evenly distributed to every teacher lessons and students can be met to use the computer lab right on schedule in order not to occur collisions. In the fuzzy algorithm of evolution has several stages, among others: Represent chromosome, Initialize the population, Determining the function of Evaluation, doing the selection, Specify the Operator and include a combination of genetics, in the crossover and mutation.
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BROUT, R., and R. PARENTANI. "TIME IN COSMOLOGY." International Journal of Modern Physics D 08, no. 01 (February 1999): 1–22. http://dx.doi.org/10.1142/s0218271899000031.
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The notion of time in cosmology is revealed through an examination of transition matrix elements of radiative processes occurring in the cosmos. To begin with, the very concept of time is delineated in classical physics in terms of correlations between the succession of configurations which describe a process and a standard trajectory called the clock. The total is an isolated system of fixed energy. This is relevant for cosmology in that the universe is an isolated system which we take to be homogeneous and isotropic. Furthermore, in virtue of the constraint which arises from reparametrization invariance of time, it has zero total energy. Therefore the momentum of the scale factor is determined from the energy of matter. In the quantum theory this is exploited through the use of WKB approximation for the wave function of the scale factor, justified for a large universe. The formalism then gives rise to matrix elements describing matter processes. These are shown to take on the form of usual time dependent quantum amplitudes wherein the temporal dependence is given by a background which is once more fixed by the total energy of matter.
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Wcisło, P., P. Ablewski, K. Beloy, S. Bilicki, M. Bober, R. Brown, R. Fasano, et al. "New bounds on dark matter coupling from a global network of optical atomic clocks." Science Advances 4, no. 12 (December 2018): eaau4869. http://dx.doi.org/10.1126/sciadv.aau4869.
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We report on the first Earth-scale quantum sensor network based on optical atomic clocks aimed at dark matter (DM) detection. Exploiting differences in the susceptibilities to the fine-structure constant of essential parts of an optical atomic clock, i.e., the cold atoms and the optical reference cavity, we can perform sensitive searches for DM signatures without the need for real-time comparisons of the clocks. We report a two orders of magnitude improvement in constraints on transient variations of the fine-structure constant, which considerably improves the detection limit for the standard model (SM)–DM coupling. We use Yb and Sr optical atomic clocks at four laboratories on three continents to search for both topological defect and massive scalar field candidates. No signal consistent with a DM coupling is identified, leading to considerably improved constraints on the DM-SM couplings.
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Lee, Jinsu, and Eunji Lee. "Concerto: Dynamic Processor Scaling for Distributed Data Systems with Replication." Applied Sciences 11, no. 12 (June 21, 2021): 5731. http://dx.doi.org/10.3390/app11125731.
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A surge of interest in data-intensive computing has led to a drastic increase in the demand for data centers. Given this growing popularity, data centers are becoming a primary contributor to the increased consumption of energy worldwide. To mitigate this problem, this paper revisits DVFS (Dynamic Voltage Frequency Scaling), a well-known technique to reduce the energy usage of processors, from the viewpoint of distributed systems. Distributed data systems typically adopt a replication facility to provide high availability and short latency. In this type of architecture, the replicas are maintained in an asynchronous manner, while the master synchronously operates via user requests. Based on this relaxation constraint of replica, we present a novel DVFS technique called Concerto, which intentionally scales down the frequency of processors operating for the replicas. This mechanism can achieve considerable energy savings without an increase in the user-perceived latency. We implemented Concerto on Redis 6.0.1, a commercial-level distributed key-value store, demonstrating that all associated performance issues were resolved. To prevent a delay in read queries assigned to the replicas, we offload the independent part of the read operation to the fast-running thread. We also empirically demonstrate that the decreased performance of the replica does not cause an increase of the replication lag because the inherent load unbalance between the master and replica hides the increased latency of the replica. Performance evaluations with micro and real-world benchmarks show that Redis saves 32% on average and up to 51% of energy with Concerto under various workloads, with minor performance losses in the replicas. Despite numerous studies of the energy saving in data centers, to the best of our best knowledge, Concerto is the first approach that considers clock-speed scaling at the aggregate level, exploiting heterogeneous performance constraints across data nodes.
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Haentjens, B., G. Desruelles, G. Chrétien, A. Leborgne, Y. Haentjens, J. Dupuy, F. Jorge, et al. "Packaging Tradeoff for SIP Integration Targeting High Speed PAM-4 Applications." International Symposium on Microelectronics 2015, no. 1 (October 1, 2015): 000730–34. http://dx.doi.org/10.4071/isom-poster3.
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High speed transmission systems using optical fiber are now focusing on 4-level PAM (Pulse Amplitude Modulation) format. This is requesting ultra-wideband electronic system in package, with a high phase linearity behavior in order to drive the electro-optical modulators. Moreover, new power DAC (Digital to Analog Converter) dies, are now available to generate up to 56 GBd, 4-level PAM signals, and providing 4Vpp of differential output amplitude swing. High frequency studies have been pursued to provide system integration in a BGA (Ball Grid Array) package. The BGA package transitions optimization and the configuration of multi-lines carriers, becomes a key step in the design flow. In this paper, some steps of the design, manufacturing process of the SIP (System In Package) and its demonstration board are proposed. The choices of the package, the thermal management, the clock management function are studied according to the final environmental constraint of the SIP. The data lines phase skew are analyzed with the support of EM (Electro Magnetic) simulations to better understand the potential impact on the output eye. Finally, the BGA package transition, simulated and measured results are compared, from DC up to 40 GHz and the measured SIP output, 4 levels, 56GBps eye diagram is presented.
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Qin, Honglei, Peng Liu, Li Cong, and Xia Xue. "Ambiguity of Residual Constraint-Based Precise Point Positioning with Partial Ambiguity Resolution under No Real-Time Network Corrections Using Real Global Positioning System (GPS) Data." Sensors 20, no. 11 (June 5, 2020): 3220. http://dx.doi.org/10.3390/s20113220.
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Although precise point positioning (PPP) is a well-established and promising technique with the use of precise satellite orbit and clock products, it costs a long convergence time to reach a centimeter-level positioning accuracy. The PPP with ambiguity resolution (PPP-AR) technique can improve convergence performance by resolving ambiguities after separating the fractional cycle bias (FCB). Now the FCB estimation is mainly realized by the regional or global operating reference station network. However, it does not work well in the areas where network resources are scarce. The contribution of this paper is to realize an ambiguity residual constraint-based PPP with partial ambiguity resolution (PPP-PARC) under no real-time network corrections to speed up the convergence, especially when the performance of the float solution is poor. More specifically, the update strategy of FCB estimation in a stand-alone receiver is proposed to realize the PPP-PAR. Thereafter, the solving process of FCB in a stand-alone receiver is summarized. Meanwhile, the influencing factors of the ambiguity success rate in the PPP-PAR without network corrections are analyzed. Meanwhile, the ambiguity residual constraint is added to adapt the particularity of the partial ambiguity-fixing without network corrections. Moreover, the positioning experiments with raw observation data at the Global Positioning System (GPS) globally distributed reference stations are conducted to determine the ambiguity residual threshold for post-processing and real-time scenarios. Finally, the positioning performance was verified by 22 GPS reference stations. The results show that convergence time is reduced by 15.8% and 26.4% in post-processing and real-time scenarios, respectively, when the float solution is unstable, compared with PPP using a float solution. However, if the float solution is stable, the PPP-PARC method has performance similar to the float solution. The method shows the significance of the PPP-PARC for future PPP applications in areas where network resource is deficient.
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GREWAL, GARY WILLIAM, and THOMAS CHARLES WILSON. "AN ENHANCED GENETIC ALGORITHM FOR SOLVING THE HIGH-LEVEL SYNTHESIS PROBLEMS OF SCHEDULING, ALLOCATION, AND BINDING." International Journal of Computational Intelligence and Applications 01, no. 01 (March 2001): 91–110. http://dx.doi.org/10.1142/s1469026801000044.
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This paper presents a novel approach to the concurrent solution of three High-Level Synthesis (HLS) problems that are modeled as a Constraint-Satisfaction Problem (CSP) and solved using an Enhanced Genetic Algorithm (EGA). We focus on the core problems of high-level synthesis: Scheduling, Allocation, and Binding. Scheduling consists of assigning of operations in a Data-Flow Graph (DFG) to control steps or clock cycles. Allocation selects specific numbers and types of functional units from a hardware library to perform the operations specified in the DFG. Binding assigns constituent operations of the DFG to specific unit instances. A very general version of this problem is considered where functional units may perform different operations in different numbers of control steps. The EGA is designed to solve CSPs quickly and does not require a user to specify appropriate mutation and crossover rates a priori; these are determined automatically during the course of the genetic search. The enhancements include a directed mutation operator and a new type of elitism that avoids premature convergence. The HLS problems are solved by applying two EGAs in a hierarchical manner. The first performs allocation, while the second performs scheduling and binding and serves as the fitness function for the second. When compared to other, well-known techniques, our results show a reduction in time to obtain optimal solutions for standard benchmarks.
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Jorba, Jaume, Ray Campagnoli, Lina De, and Olen Kew. "Calibration of Multiple Poliovirus Molecular Clocks Covering an Extended Evolutionary Range." Journal of Virology 82, no. 9 (February 20, 2008): 4429–40. http://dx.doi.org/10.1128/jvi.02354-07.
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ABSTRACT We have calibrated five different molecular clocks for circulating poliovirus based upon the rates of fixation of total substitutions (K t ), synonymous substitutions (K s ), synonymous transitions (A s ), synonymous transversions (B s ), and nonsynonymous substitutions (K a ) into the P1/capsid region (2,643 nucleotides). Rates were determined over a 10-year period by analysis of sequences of 31 wild poliovirus type 1 isolates representing a well-defined phylogeny derived from a common imported ancestor. Similar rates were obtained by linear regression, the maximum likelihood/single-rate dated-tip method, and Bayesian inference. The very rapid K t [(1.03 ± 0.10) × 10−2 substitutions/site/year] and K s [(1.00 ± 0.08) × 10−2] clocks were driven primarily by the A s clock [(0.96 ± 0.09) × 10−2], the B s clock was ∼10-fold slower [(0.10 ± 0.03) × 10−2], and the more stochastic K a clock was ∼30-fold slower [(0.03 ± 0.01) × 10−2]. Nonsynonymous substitutions at all P1/capsid sites, including the neutralizing antigenic sites, appeared to be constrained by purifying selection. Simulation of the evolution of third-codon positions suggested that saturation of synonymous transitions would be evident at 10 years and complete at ∼65 years of independent transmission. Saturation of synonymous transversions was predicted to be minimal at 20 years and incomplete at 100 years. The rapid evolution of the K t , K s , and A s clocks can be used to estimate the dates of divergence of closely related viruses, whereas the slower B s and K a clocks may be used to explore deeper evolutionary relationships within and across poliovirus genotypes.
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Pouyaud, L., R. Gustiano, and G. G. Teugels. "CONTRIBUTION TO THE PHYLOGENY OF THE PANGASIIDAE BASED ON MITOCHONDRIAL 12S RDNA." Indonesian Journal of Agricultural Science 5, no. 2 (October 25, 2016): 4562. http://dx.doi.org/10.21082/ijas.v5n2.2004.4562.
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Catfishes are generally one of the economically important groups of fresh and brackish water fishes in the world. In many countries, they form a significant part of inland fisheries, and several species have been introduced in fish culture. Judging from literature, the main constraint to cultivate wild species and to optimise the production of pangasiid catfishes is due to the poorly documented systematics of this family. In the present contribution, the phylogenetic relationships within Pangasiidae are studied to contribute to a better insight in their taxonomy and evolution. The genetic relatedness is inferred using mitochondrial 12S rDNA gene sequences. To resolve the phylogenetic position of Laides in this group of catfish, five genera of Asian and African Schilbeidae are also considered. The results showed that a species group (complex) could be clearly seen in the genetic tree. Pangasius is more derive than the other genera. By using approximate molecular clock/evolutionary calibration from mitochondrial gene, a new episode of speciation for the family marked explosive radiation about 5- 8 million years ago (mya). This adaptive radiation extended until the Late Pleistocene. Regarding the relationships between the Pangasiidae and Schilbeidae, two families show an allopatric distribution with slight overlap. The Pangasiidae occur mainly in Southeast Asia, while the Schilbeidae are seen mainly on the Indian subcontinent (including Myanmar) and Africa. It confirms the separation between Schilbeidae and Pangasiidae occurred in the Early Miocene.
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Pouyaud, L., R. Gustiano, and G. G. Teugels. "CONTRIBUTION TO THE PHYLOGENY OF THE PANGASIIDAE BASED ON MITOCHONDRIAL 12S RDNA." Indonesian Journal of Agricultural Science 5, no. 2 (October 25, 2016): 4562. http://dx.doi.org/10.21082/ijas.v5n2.2004.p4562.
Full textAbstract:
Catfishes are generally one of the economically important groups of fresh and brackish water fishes in the world. In many countries, they form a significant part of inland fisheries, and several species have been introduced in fish culture. Judging from literature, the main constraint to cultivate wild species and to optimise the production of pangasiid catfishes is due to the poorly documented systematics of this family. In the present contribution, the phylogenetic relationships within Pangasiidae are studied to contribute to a better insight in their taxonomy and evolution. The genetic relatedness is inferred using mitochondrial 12S rDNA gene sequences. To resolve the phylogenetic position of Laides in this group of catfish, five genera of Asian and African Schilbeidae are also considered. The results showed that a species group (complex) could be clearly seen in the genetic tree. Pangasius is more derive than the other genera. By using approximate molecular clock/evolutionary calibration from mitochondrial gene, a new episode of speciation for the family marked explosive radiation about 5- 8 million years ago (mya). This adaptive radiation extended until the Late Pleistocene. Regarding the relationships between the Pangasiidae and Schilbeidae, two families show an allopatric distribution with slight overlap. The Pangasiidae occur mainly in Southeast Asia, while the Schilbeidae are seen mainly on the Indian subcontinent (including Myanmar) and Africa. It confirms the separation between Schilbeidae and Pangasiidae occurred in the Early Miocene.
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Yiğitler, Hüseyin, Behnam Badihi, and Riku Jäntti. "Overview of Time Synchronization for IoT Deployments: Clock Discipline Algorithms and Protocols." Sensors 20, no. 20 (October 20, 2020): 5928. http://dx.doi.org/10.3390/s20205928.
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Internet of Things (IoT) is expected to change the everyday life of its users by enabling data exchanges among pervasive things through the Internet. Such a broad aim, however, puts prohibitive constraints on applications demanding time-synchronized operation for the chronological ordering of information or synchronous execution of some tasks, since in general the networks are formed by entities of widely varying resources. On one hand, the existing contemporary solutions for time synchronization, such as Network Time Protocol, do not easily tailor to resource-constrained devices, and on the other, the available solutions for constrained systems do not extend well to heterogeneous deployments. In this article, the time synchronization problems for IoT deployments for applications requiring a coherent notion of time are studied. Detailed derivations of the clock model and various clock relation models are provided. The clock synchronization methods are also presented for different models, and their expected performance are derived and illustrated. A survey of time synchronization protocols is provided to aid the IoT practitioners to select appropriate components for a deployment. The clock discipline algorithms are presented in a tutorial format, while the time synchronization methods are summarized as a survey. Therefore, this paper is a holistic overview of the available time synchronization methods for IoT deployments.
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De Baets, Kenneth, Alexandre Antonelli, and Philip C. J. Donoghue. "Tectonic blocks and molecular clocks." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1699 (July 19, 2016): 20160098. http://dx.doi.org/10.1098/rstb.2016.0098.
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Evolutionary timescales have mainly used fossils for calibrating molecular clocks, though fossils only really provide minimum clade age constraints. In their place, phylogenetic trees can be calibrated by precisely dated geological events that have shaped biogeography. However, tectonic episodes are protracted, their role in vicariance is rarely justified, the biogeography of living clades and their antecedents may differ, and the impact of such events is contingent on ecology. Biogeographic calibrations are no panacea for the shortcomings of fossil calibrations, but their associated uncertainties can be accommodated. We provide examples of how biogeographic calibrations based on geological data can be established for the fragmentation of the Pangaean supercontinent: (i) for the uplift of the Isthmus of Panama, (ii) the separation of New Zealand from Gondwana, and (iii) for the opening of the Atlantic Ocean. Biogeographic and fossil calibrations are complementary, not competing, approaches to constraining molecular clock analyses, providing alternative constraints on the age of clades that are vital to avoiding circularity in investigating the role of biogeographic mechanisms in shaping modern biodiversity. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’.
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Goda, Tadahiro, Brandi Sharp, and Herman Wijnen. "Temperature-dependent resetting of the molecular circadian oscillator in Drosophila." Proceedings of the Royal Society B: Biological Sciences 281, no. 1793 (October 22, 2014): 20141714. http://dx.doi.org/10.1098/rspb.2014.1714.
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Circadian clocks responsible for daily time keeping in a wide range of organisms synchronize to daily temperature cycles via pathways that remain poorly understood. To address this problem from the perspective of the molecular oscillator, we monitored temperature-dependent resetting of four of its core components in the fruitfly Drosophila melanogaster : the transcripts and proteins for the clock genes period ( per ) and timeless ( tim ). The molecular circadian cycle in adult heads exhibited parallel responses to temperature-mediated resetting at the levels of per transcript, tim transcript and TIM protein. Early phase adjustment specific to per transcript rhythms was explained by clock-independent temperature-driven transcription of per . The cold-induced expression of Drosophila per contrasts with the previously reported heat-induced regulation of mammalian Period 2 . An altered and more readily re-entrainable temperature-synchronized circadian oscillator that featured temperature-driven per transcript rhythms and phase-shifted TIM and PER protein rhythms was found for flies of the ‘Tim 4’ genotype, which lacked daily tim transcript oscillations but maintained post-transcriptional temperature entrainment of tim expression. The accelerated molecular and behavioural temperature entrainment observed for Tim 4 flies indicates that clock-controlled tim expression constrains the rate of temperature cycle-mediated circadian resetting.
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Flis, Anna, Aurora Piñas Fernández, Tomasz Zielinski, Virginie Mengin, Ronan Sulpice, Kevin Stratford, Alastair Hume, et al. "Defining the robust behaviour of the plant clock gene circuit with absolute RNA timeseries and open infrastructure." Open Biology 5, no. 10 (October 2015): 150042. http://dx.doi.org/10.1098/rsob.150042.
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Our understanding of the complex, transcriptional feedback loops in the circadian clock mechanism has depended upon quantitative, timeseries data from disparate sources. We measure clock gene RNA profiles in Arabidopsis thaliana seedlings, grown with or without exogenous sucrose, or in soil-grown plants and in wild-type and mutant backgrounds. The RNA profiles were strikingly robust across the experimental conditions, so current mathematical models are likely to be broadly applicable in leaf tissue. In addition to providing reference data, unexpected behaviours included co-expression of PRR9 and ELF4 , and regulation of PRR5 by GI . Absolute RNA quantification revealed low levels of PRR9 transcripts (peak approx. 50 copies cell −1 ) compared with other clock genes, and threefold higher levels of LHY RNA (more than 1500 copies cell −1 ) than of its close relative CCA1 . The data are disseminated from BioDare, an online repository for focused timeseries data, which is expected to benefit mechanistic modelling. One data subset successfully constrained clock gene expression in a complex model, using publicly available software on parallel computers, without expert tuning or programming. We outline the empirical and mathematical justification for data aggregation in understanding highly interconnected, dynamic networks such as the clock, and the observed design constraints on the resources required to make this approach widely accessible.
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Chen, Yen-Liang, and Li-Jen Hsiao. "Shipping problems with body clock constraints." Computers & Operations Research 30, no. 7 (June 2003): 1037–49. http://dx.doi.org/10.1016/s0305-0548(02)00054-0.
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Bérard, Béatrice, and Catherine Dufourd. "Timed automata and additive clock constraints." Information Processing Letters 75, no. 1-2 (July 2000): 1–7. http://dx.doi.org/10.1016/s0020-0190(00)00075-2.
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