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Timing jitter, frequency offset, carrier phase jitter and sampling clock frequency offset are the main synchronization errors encountered by OFDM systems. As many literatures have proved, OFDM systems are very sensitive to frequency errors. In this paper, three new methods to estimate the integer part of frequency offset are proposed, simulation results show its robustness to mitigate the multi-path effect and its enlarged estimation range for frequency offset. The correspondent Field Programmable Gate Array (FPGA) circuit through test in HDTV prototype in Team of Engineering Expert Group (TEEG) proves its feasibility and availability. The proposed method is also suitable for burst mode transmission systems such as Wireless Local Area Network (WLAN) and Fixed-Broadband Wireless Access (F-BWA). Index Terms--COFDM, HDTV, Frequency offset estimation, WLAN

Since the trend of electricity power industry reformation is to separate power plants from grid, it’s difficult for power Grid Company to interference the operation of plants. But as a manager of grid, it’s necessary for Grid Company to build a calculation formula of monthly standard electricity coal inventory to estimate the security of thermal power plant operation. y analyzing the special features of coal inventory management of thermal power plants. Taking into consideration of the changing demand of electricity and the uncertain supply of coal during a month, a practical inventory model with the target of maximizing the safety of generating electricity was built based on the modified classic safety stock formula to determine the optimal standard safety stocks. It’s depends on history data. Finally, On the basis of the solving results of power plants in Hunan province, the optimal safety stock was found, and the quantity of coal to purchase during a month were also suggested. The results provide a good reference for guiding the purchase and storage strategy of thermal power plant.

The line overload is discussed and the coordination and optimization model of preventive and emergency control is proposed in this paper. It combines with the sensitivity’s concept and reverse phase equivalent matching adjustment principle, takes into account the severity of the accident probability and consequences, and introduces the important factor of the corresponding accident; adjust automatically according to the influence degree of the accident to the power grid. Getting reasonable coordination optimization strategies to ensure the safety and economy of the system is effective and verified by this paper.

Combined with the power system fault diagnosis current situation, fault diagnosis methods are important to shorten fault outage time, prevent accident expanding and restore power quickly. We summed up expert system, artificial neural network, Petri network and Bayesian network fault diagnosis methods. The diagnosis principle, advantages and disadvantages of different methods were discussed.

This paper introduces the complexity of fault information and summarizes some main methods in the field of fault diagnosis,including Expert system,Artificial neural network,Fuzzy inference,Rough set theory,Petri network,Bias network,etc.Analyse basic concepts,method principles and their advantages and disadvantages of various methods.Put forward methods of combining multiple methods to synthetically handle the fault information of power network

Pancreatic cancer remains a lethal disease. In this study, we investigated the efficacy of a combination of gastrin-releasing peptide receptor antagonist RC-3095 and gemcitabine on pancreatic cancer CFPAC-1.

Three novel flame retardants containing both phosphorus and silicon elements in their structures, including [(1,1,3,3-tetramethyl-1,3-disiloxanediyl)di-2, 1-ethanediyl]bis(diphenylphosphine oxide) (FR-1), [(2,4,6,8-tetramethylcyclotetra-siloxane-2,4,6,8-tetrayl)tetra-2,1-ethanediyl]tetrakis[diphenylphosphine oxide] (FR-2) and 1,3,5,7,9,11,13,15-octakis(di-phenylphosphine oxide-2,1-ethanediyl)pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (FR-3) were synthesized by a convenient pathway from the reaction of diphenylphosphine oxide (DPPO) and vinyl-terminated siloxanes under the catalysis of triethylborane. The chemical structures of the target compounds were confirmed by nuclear magnetic resonance (1H NMR, 13C NMR, 29Si NMR and 31P NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and Fourier transform infrared (FT IR) measurements. Thermogravimetric analysis (TGA) results indicated that the new flame retardants possessed good thermal stability both in nitrogen and in air. FR-3 containing polyhedral oligosilsesquioxanes (POSS) moiety exhibited the best thermal properties with a 10% weight loss temperature 400°C and a residual weight ratio 39% at 700°C.

Novel ether-bridged fluorinated poly(phenylquinoxaline) (PEPPQ) dielectric films with enhanced glass-transition temperatures (Tg) have been developed in order to meet the high-temperature demands for interlayer dielectrics used in microelectronic fabrication. The PEPPQ films were prepared from newly-developed aromatic bis(α-diketone) monomers containing ortho-substituted methyl groups (2-1) or a fluorene moiety (2-2) in their molecular structures. The obtained PEPPQ films exhibited excellent combined properties, including high thermal stability with Tgover 260 °C, high electrical insulating characteristics with a volume resistivity of over 1017Ω cm, and a dielectric strength higher than 212 V μm−1. Besides, the bulky substituents and low-molar-electronegative trifluoromethyl groups endowed the polymers with low dielectric constants (DK< 2.82 at 1 MHz) and good water repellent property.

A new diamine monomer with bis-trifluoromethyl-substituted phenyl in the side chain, α,α-bis (4-amino-3,5-dimethylphenyl)-3′,5′-bis(trifluoromethyl)phenyl methane (6FMA) was successfully synthesized. A series of fluorinated polyimides (PI-IIa-d) were prepared by reacting the diamine with various aromatic dianhydrides. For comparison, another series of polyimides (PI-Ia-d) derived from another diamine with single-trifluoromethyl-substituted phenyl in the side chain, α,α-bis(4-amino-3,5-dimethylphenyl)-3′-trifluoromethyl phenyl methane and the same dianhydrides were also synthesized. The polymers were characterized by inherent viscosity, elemental analysis, Fourier transform-infrared, X-ray, ultraviolet-visible analysis, moisture absorption, thermogravimetric analysis, and differential scanning calorimetry measurements. It was shown that PI-II polyimides exhibited good film formability, enhanced solubility, good thermal stability, superior optical transparency, and acceptable mechanical properties. In addition, the polyimides derived from 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 6FMA showed high sensitivity to i-line (365 nm) of a high-pressure mercury lamp. The combined properties of the polyimides make them good candidates for microelectronic fabrications.

Summary: Two novel polypyrrolones (PPys) with asymmetric biphenyl moieties in the main chains have been synthesized from 2,3,3′,4′-biphenyl tetracarboxylic dianhydride (a-BPDA) and two aromatic tetra-amines: 3,3′,4,4′‐tetra‐amino biphenyl (TABP) and 3,3′,4,4′‐tetra‐amino diphenyl ether (TADPE) respectively, via soluble poly(amide amino acid) (PAAA) precursors, followed by thermal cyclization at elevated temperatures. The polymerization and curing conditions were studied and confirmed. Asymmetric biphenyl structures endowed the polymers with good combined properties. For example, flexible and tough PPy films with acceptable mechanical properties were obtained. Tensile strengths of higher than 70 MPa and elongations at break of higher than 6% were achieved. The PPy films with a final curing temperature of 350 °C exhibited good thermal stability and the 10% weight loss temperatures were 610.3 °C for PPy‐I, and 607.8 °C for PPy‐II. The residual weight ratios at 700 °C were higher than 80%. In addition, the PPy films showed good dielectric properties with dielectric breakdown strengths of higher than 100 V · µm−1 and dielectric constants of 3.64 for PPy‐I and 3.53 for PPy‐II.Chemical structures of polypyrrolones with asymmetric biphenyl moieties.

A novel fluorinated aromatic diamine, 1,1‐bis(4‐amino‐3,5‐dimethylphenyl)‐1‐(3,5‐ditrifluoromethylphenyl)‐2,2,2‐trifluoroethane (9FMA), was synthesized by the coupling reaction of 3′,5′‐ditrifluoromethyl‐2,2,2‐trifluoroacetophenone with 2,6‐dimethylaniline under the catalysis of 2,6‐dimethylaniline hydrochloride. A series of fluorinated aromatic polyimides were synthesized from 9FMA and various aromatic dianhydrides, including pyromellitic dianhydride, 3,3′4,4′‐biphenyl tetracarboxylic dianhydride, 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′‐hexafluoroisopropylidene diphthalic anhydride, via a high‐temperature, one‐stage imidization process. The inherent viscosities of the polyimides ranged from 0.37 to 0.74 dL/g. All the polyimides were quickly soluble in many low‐boiling‐point organic solvents such as tetrahydrofuran, chloroform, and acetone as well as some polar organic solvents such as N‐methyl‐2‐pyrrolidinone, N,N′‐dimethylacetamide, and N,N′‐dimethylformamide. Freestanding fluorinated polyimide films could be prepared and exhibited good thermal stability with glass‐transition temperatures of 298–334 °C and outstanding mechanical properties with tensile strengths of 69–102 MPa and elongations at break of 3.3–9.9%. Moreover, the polyimide films possessed low dielectric constants of 2.70–3.09 and low moisture absorption (<0.58%). The films also exhibited good optical transparency with a cutoff wavelength of 303–351 nm. One polyimide (9FMA/BTDA) also exhibited an intrinsic negative photosensitivity, and a fine pattern could be obtained with a resolution of 5 μm after exposure at the i‐line (365‐nm) wavelength. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2665–2674, 2006

A series of organo-soluble polyimides based on a new fluorinated diamine, 4,4′-bis(3-amino-5-trifluoromethylphenoxy)-3,3′,5,5′-tetramethyl biphenyl (3,5-TFMDA) and various aromatic dianhydrides, were synthesized and characterized. The structures of the obtained polyimides were affirmed by Fourier transform infrared measurement and the properties were evaluated by wide-angle X-ray diffraction measurement, ultraviolet-visible analysis, thermogravimetry (TG), differential scanning calorimetry (DSC), tensile and electrical tests, and solubility tests. It was shown that the polyimides have good solubility not only in polar aprotic solvents, but in many common solvents, such as cyclopentanone, chloroform, and even in toluene for PI-4, derived from TFMDA and 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA). The polyimide solutions could be cast into flexible and tough films, which exhibited good thermal stability up to 500° C and showed glass transition temperatures in the range of 250–280° C. The films also showed acceptable tensile properties and good electrical insulating properties. Furthermore, the polyimide films exhibited good transparency in the visible light region with transmittance higher than 80% at 450 nm and a cut-off wavelength lower than 360 nm.

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A series of new polybenzimidazopyrrolones (polypyrrolone, PPy) were synthesized by polycondensation of pyridine-bridged aromatic tetraamines, including 2,6-bis (3',4'-diaminophenyl)-4-phenylpyridine and 2,6-bis(3',4'- diaminophenyl)-4-(3"-trifluoromethyl)phenyl pyridine, with various aromatic dianhydrides. Experimental results indicated that the PPys, multiaromatic conjugated and semiladder polymers, showed good thermal stabilities with thermal-decomposition temperatures of about 500 °C and residual weight retention at 750 °C as high as 84%. PPy films could be obtained by casting the precursor solution, poly(amide amino acid) on glass substrate, followed by thermal dehydrating at elevated temperatures. The polymer films exhibited excellent alkaline hydrolysis resistance, which retained their original shapes and toughness after boiling 7 days in 10% sodium hydroxide solution. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1845–1856, 2004

A series of new polymerized monomer reactants (PMR) matrix resins of poly(pyrrolone-benzimidazole)s containing a pyridine unit (PPBP) were synthesized by polycondensation of monoethyl ester of cis-5-norbornene-endo-2,3-dicarboxylic acid, 2,6-diphenyl ester pyridinedicarboxylic acid or 3,5-diphenyl ester pyridinedicarboxylic acid, and diethyl ester of 4,4'-oxydiphthalic acid with 3,3'-diaminobenzidine in a mixing solution of anhydrous ethyl alcohol and N-methylpyrrolidone under given temperature and pressure conditions. The resulting resin solutions showed good solubility in polar organic solvents and stability at room temperature. The corresponding PPBP matrix resin, molded powder, and molded plate were prepared by undergoing amidation, imidization, cyclization, and crosslinking reactions when the reaction temperature was increased from 80 to 350°C, successively; the crosslinking structure was formed by the reverse Diels–Alder reaction at 270–290°C under 50 MPa pressure (2.5–3.5 MPa displayed by the pressure meter). The chemical reactions and properties of the resulting PPBP were studied by means of FTIR, TGA, and DMA methods, and the results indicated that the kinds of PPBP materials retain excellent thermal stability and processability; when the initial decomposition temperature was above 620°C the Tg was at 413.5°C for 3,5-PPBP-20 molded plate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3981–3990, 2004

Two fluorinated polyphenylquinoxalines (FPPQs) have been prepared from the newly developed trifluoromethyl-containing aromatic bis(a-diketone) monomers (FTKs) and aromatic bis(o-diamine). The thermal, electrical, and hydrolytic properties of the FPPQs were investigated. The results reveal that the developed FPPQ films exhibit low dielectric constants of 2.78–2.85, which are closely related to their excellent hydrophobic nature. The FPPQ films also manifest excellent hydrolytic stability in the aqueous environment. Meanwhile, the intrinsically high thermal stability and electrical resistivity are maintained for the FPPQs.

Trissolcus japonicus (Hymenoptera: Scelionidae) and Trissolcus plautiae are solitary endoparasitoids in eggs of stink bugs (Hemiptera: Pentatomidae). These two closely related parasitoids differ in their degree of host specificity. With the aid of scanning electron microscopy, we examined the external morphology, distribution, and abundance of the antennal sensilla of sexes of both species to gain insights into the olfactory mechanism in relation to host selection behavior. Seven types of sensilla were recorded in both species: basiconica, trichodea, grooved-peg, sickle-shaped, chaetica, papillary, and campaniformium sensilla. Sexual dimorphism of antennal structures occurred in both species. Male antennae possessed one more flagellomere and a larger number of olfactory sickle-shaped sensilla than female antennae, indicating that sensilla may be involved in mate or host location. There was a peg gland on the fifth antennomere of male antennae. Compared with males, females had a higher number of trichodea sensilla as well as papillary sensilla, which were not found in males. These sensilla might be involved in host recognition and acceptance during the drumming behavior of both species. No qualitative differences were recorded between the species in antennal structure, or sensilla types or topographical arrangement. However, the abundance of key sensilla was significantly different between species. T. plautiae females and males had larger numbers of trichodea sensilla than those of T. japonicus. T. japonicus females possessed fewer and larger sickle-shaped sensilla compared with T. plautiae females. These differences may provide a morphological basis for understanding the process of host habitat location and recognition in these parasitoids.