Weak wide-band signal detection method based on small-scale periodic state of Duffing oscillator

The conventional Duffing oscillator weak signal detection method, which is based on a strong reference signal, has inherent deficiencies. To address these issues, the characteristics of the Duffing oscillator＇s phase trajectory in a small- scale periodic state are analyzed by introducing the theory of stopping oscillation system. Based on this approach, a novel Duffing oscillator weak wide-band signal detection method is proposed. In this novel method, the reference signal is discarded, and the to-be-detected signal is directly used as a driving force. By calculating the cosine function of a phase space angle, a single Duffing oscillator can be used for weak wide-band signal detection instead of an array of uncoupled Duffing oscillators. Simulation results indicate that, compared with the conventional Duffing oscillator detection method, this approach performs better in frequency detection intervals, and reduces the signal-to-noise ratio detection threshold, while improving the real-time performance of the system.

Scientific Investigation on Bronze Swords from Spring-Autumn and Warring States Period

1. Introduction The bronze swords were somewhat important in ancient China. Its alloy constituent analysishas been carried out by some scientist with modern technique. Afterwards, a series of work havebeen published. The main results are: (1) the sword materials are Pb-Sn-bearing bronze with tincontent at 15～19%; (2) it is cast alloy mainly; (3) the rhombus pattern on the sword of Yue King

THE STATE COUNCIL DECIDES TO EXTEND THEIMPORT-DUTY EXEMPTION PERIOD FOR IMPORTS OF EQUIPMENT AND RAW MATERIALS BY ENTERPRISES WITH FOREIGN INVESTMENT

Recently the State Council decided to extend the period ofduty exemption for imports of equipment and raw materials by foreign-invested enterprises below US$30 million.In order to administrate import and export activities in light ofinternational practice and apply a unified, fair and standardizedpolicy toward import duties, the State Council, on December28,1995, decided to reform and adjust the policies of import duties by fairly significant reduction of the overall import tariff leveland elimination of preferences of import-duty exemption for mostimport items, which was also applicable to imports of equipmentand raw materials by foreign-invested enterprises set up since April1st, 1996. At the same time, with a view to maintaining the policycontinuity and relative stability, those enterprises established before March 31, 1996 were allowed an extended duty-exemptionperiod of one to two years for importation of equipment and rawmaterials(referring to construction materials, etc.) if such importswere below the value of their total investments, and for

A PERIODICALLY LOCALIZED TRAVELING WAVE STATE OF BINARY FLUID CONVECTION WITH HORIZONTAL FLOWS

In this paper, the convection structure in a rectangular channel with a horizontal flow was studied for the aspect ratio ГA=12 and the separation ratio ψ=-0.11. Our simulations were preformed by solving the hydrodynamic equations using the SIMPLE method. In the system of binary fluid convection with a horizontal flow, a Periodically Localized Traveling Wave （PLTW） state was found. It has similar behavior to classical Rayleigh-Benard convection in a binary fluid mixture, but the region and wave number of convection change periodically with time. The instability of PLTW depends on the Rayleigh number r and the intensity of horizontal flows Re for given ψ. Thus, the PLTW convection results from the competition between the horizontal flow and the counter-propagating wave near the onset of convection.

SECOND-ORDER OPTIMALITY CONDITIONS FOR OPTIMAL CONTROL PROBLEMS GOVERNED BY 3-DIMENSIONAL NEVIER-STOKES EQUATIONS

This article is concerned with second-order necessary and sufficient optimality conditions for optimal control problems governed by 3-dimensional Navier-Stokes equations. The periodic state constraint is considered.

Analysis of a kind of Duffing oscillator system used to detect weak signals

The stability of the periodic solution of the Duffing oscillator system in the periodic phase state is proved by using the Yoshizaw theorem, which establishes a theoretical basis for using this kind of chaotic oscillator system to detect weak signals. The restoring force term of the system affects the weak-signal detection ability of the system directly, the quantitative relationship between the coefficients of the linear and nonlinear items of the restoring force of the Duffing oscillator system and the SNR in the detection of weak signals is obtained through a large number of simulation experiments, then a new restoring force function with better detection results is established.

Diversified manufacturing processes and multiple mineral sources:Features of Warring States bronze vessels excavated from Chutai Cemetery M1,Anhui Province

Northern Anhui was an important region for diverse bronze culture convergence and extensive metal resource circulation in the Pre-Qin Period.In this paper,metallographic microstructure analysis,chemical composition analysis,and lead isotope ratio analysis were conducted on 12 samples of 6 Warring States Period(476–221 BCE)bronze vessels excavated from Chutai Cemetery M1,Fuyang,Anhui Province,revealing the integrated application of diversified manufacturing processes,such as casting,forging,cold working,and welding and multiple metal minerals.The analytical results showed that 2 Ding vessels(鼎)were made by casting,and 2 He vessels(盒)and 2 Dui vessels(敦)were made by forging followed by cold working.These two types of bronze vessels made by different manufacturing processes have significantly distinct alloy ratios and mineral sources,among which the Cu and Sn contents of the 2 cast bronze vessels are lower and the Pb content is higher,while the Cu and Sn contents of the 4 forged bronze vessels are higher and the Pb content is lower.The lead minerals of the two types of bronze vessels might come from Western Henan and the middle and lower reaches of the Yangtze River,respectively.In addition,the 3 pieces of solder used to weld bronze vessels were all made of pure Sn,their metal minerals should come from the densely distributed area of tin ore in Southern China,and Sn solders were mainly discovered in the Chu culture area during the Eastern Zhou Period.

Food Basin from the State of Xi Spring and Autumn Period (770-476 B.C.)

The State of Xi was a small kingdom in ancient times located between the Yangtze River and Huaihe River. It was overturned by leaders from the State of Chu in 680 B.C. This bronze basin, the only unearthed relic from the State of Xi, is 21 centimeters in girth, has a lid with a bugle-shaped handle and two symmetrical handles on the sides. The bottom of the basin is engraved with the characters meaning "Xing, the king of the State Xi has this as his food basin."

Effect of sample size on the response of DEM samples with a realistic grading

This paper shows that for DEM simulations of triaxial tests using samples with a grading that is repre- sentative of a real soil, the sample size significantly influences the observed material response. Four DEM samples with identical initial states were produced： three cylindrical samples bounded by rigid wails and one bounded by a cubical periodic cell, When subjected to triaxial loading, the samples with rigid boundaries were more dilative, stiffer and reached a higher peak stress ratio than the sample enclosed by periodic boundaries. For the rigid-wall samples, dilatancy increased and stiffness decreased with increasing sample size, The periodic sample was effectively homogeneous, The void ratio increased and the contact density decreased close to the rigid walls, This heterogeneity reduced with increasing sample size. The positions of the critical state lines （CSLs） of the overall response in e-log p＇ space were sensitive to the sample size, although no difference was observed between their slopes. The critical states of the interior regions of the rigid-wall-bounded samples approached that of the homogeneous periodic sample with increasing sample size. The ultimate strength of the material at the critical state is independent of sample size.

Modeling and analysis of the transmission dynamics of mosquito-borne disease with environmental temperature fluctuation

Most of the vector-borne diseases show a clear dependence on seasonal variation,including climate change.In this paper,we proposed a nonautonomous mathematical model consisting of a periodic system of nonlinear differential equations.In the proposed model,the realistic functional forms for the different temperature-dependent parameters are considered.The autonomous system of the proposed model is also analyzed.The nontrivial solution of the autonomous model is locally asymptotically stable if R0<1.It is shown that a unique endemic equilibrium point of the autonomous model exists when R0>1 and proved that endemic solution is linearly stable when R0>1.The nonautonomous model is shown to have a nontrivial disease-free periodic state,which is globally asymptotically stable whenever temperature-dependent reproduction number is less than unity.It is observed that a unique positive endemic periodic solution of the nonautonomous system exists only when a temperature-dependent reproduction number greater than unity,which makes for the persistence of the disease.Numerical simulation has been carried out to support the analytical results and shows the effects of temperature variability in the life span of mosquitoes as well as the persistence of the disease.

Relationships between Microstructures and Properties of Chinese Ancient Bronzes

The typical morphology of alloy lead（Pb） in ancient bronzes made in the Spring-Autumn Warring States Period（770 B.C.-221 B.C.）,China,was examined by using electron microscopic techniques.We propose that the main purposes for adding metallic Pb in a large quantity into ancient bronzes,such as arrows and ritual vessel-Ding,were for increasing weight and economical reasons.In order to promote adding efficiency and improve casting quality for getting homogenously distributed Pb particles in the bronzes,a process through inserting Pb rod into the mold is supposed to be used during casting,which provided a process for preventing Pb sinkage.Scanning electron microscope（SEM） observations from the fracture surface of the bronzes revealed that the Pb particle possessed a ＂hollow-cored bubble＂ structure,which was formed due to absorbing casting gases during solidification and therefore indirectly eliminated the casting porosity and loosen.