Ethylene tetramerization with a highly active and long-lifetime trinuclear diphenylphosphinoamine/Cr（III）/MAO catalyst

The synthesis and characterization of a novel trinuclear diphosphinoamine ligand 2 are reported. The ligand combined with Cr(III), activated with methylaluminoxane, lead to highly active and long-lifetime catalytic systems for the tetramerization of ethylene to form 1-octene. The effects of reaction temperature, reaction pressure, molar ratio of Al/Cr and bis(diphenylphosphino)amine/Cr on the catalytic activity and product selectivity were studied. Compared with its mononuclear analogue 1, ligand 2 showed a higher catalytic activity and longer lifetime for ethylene tetramerization in the presence of methylaluminoxane as cocatalyst. High molecular weight polyethylene was generated as a by-product with extremely broad molecular weight distributions.     

Preparation of 1-octene by ethylene tetramerization with high selectivity

Two novel PNP ligands have been synthesized and characterized by ^1H-NMR, elemental analysis, and mass spectra. In combination with Cr（Ⅲ） and cocatalyst MAO, they generate active catalytic systems that tetramerize ethylene with both high catalytic activity and high selectivity to produce 1-octene. The results show that these catalyst systems are able to catalyze ethylene tetramerization, with high catalytic activity up to 0.89×10^6 g/mol Cr.h, and the selectivity of C8 in products is 72.52%, and the percentage of 1-olefins in the C8 cut is 97.87%.     

Synthesis of a novel triple-site diphosphinoamine （PNP） ligand and its applications in ethylene tetramerization

A novel triple-site diphosphinoamine （PNP） ligand was synthesized and characterized. In combination with Cr（Ⅲ） and methylaluminoxane （MAO）, it generated active catalytic systems for ethylene tetramerization toward 1-octene with high catalytic activity and long lifetime. The effects of reaction temperature, molar ratio of AI/Cr and molar ratio of ligand/Cr on catalytic activity and selectivity to 1-octene were studied with reaction kinetics of the catalytic system for ethylene tetramerization described. At the AI/Cr molar ratio of 100, the catalytic activity is up to 2.29×10^6 g· mol^-1 （Cr）· h^-1 and the selectivity to 1-octene is 49.65 wt%.     

Alternative Models of Iron and Cobalt Catalysts for Ethylene Oligomerization and Polymerization

1 Results Great progresses have been made in the field of transition metal-based complexes as catalytic precursors for olefin oligomerization and polymerization,in which the core subjects will remain as "know and how" to develop novel catalysts both in academic and industrial consideration.The key advantage of iron and cobalt catalyst for ethylene polymerization is to produce vinyl-type polyethylenes.Therefore following the pioneering works of bis(imino) pyridyl iron and cobalt catalyst by Brookhart[1] and Gibson[2] in 1998,there have been many contributions toward their derivatives' complexes for the investigation of their catalytic behaviors.However,there are few examples successful good activity catalysts based upon new designed ligands such as monoiminopyridines[3],2-imino-1,10-phenanthrolines[4],2-benzimidazolylpyridines[5],2-quinoxalinyl-6-imino pyridines[6] and bimetallic complex[7].Those catalysts performed good to high catalytic activities towards ethylene oligomerization and polymerization,meanwhile most of them were first contributed with our efforts inspired by bis(imino)pyridyl metal catalyst.Herein we will present our results with designing pathways,and academic and industrial considerations.     

Ethylene oligomerization by novel iron(Ⅱ) diimine complexes/MAO

Two novel Fe(Ⅱ) diimine complexes have been synthesized. In combination with MAO, they generate active catalytic systems that oligomerize ethylene with both high catalytic activity and high selectivity for α-olefins. The effects of substituents on the aryl ring, reaction temperatures and molar ratios of Al/Fe on catalytic activity and product distribution are studied.     

Dipiphosphinoazines-from Rich Coordination Variability to Catalysis

1 Results Diphosphinoazines are very versatile,potentially up to tetradentate ligands,known to form complexes with many transition metals.Recently,we developed synthesis of diphosphinoazines with various substituents on phosphorus donor atoms.This fine tuning allowed to design novel catalytic systems for several organic reactions.Hydroamination of Michael-type substrates with selected primary and secondary amines revealed the reactivity of some amines in non-catalyzed reaction.Hydroamination of methyl methacrylate by morpholine was catalyzed by palladium cationic complexes of type 1[1]. Cationic nickel complexes of type 2 are,in combinations with usual activators like MAO,catalysts for ethylene polymerization[2]. Palladium complexes with diphosphinoazine backbone in a deprotonated pincer-like form (type 3) are efficient catalysts for the Mizoroki-Heck reaction of bromoarenes and activated chloroarenes[3].See Fig.1.     

Ethylene Oligomerization and Polymerization: Alternative Iron Catalysts beyond 2,6-Bisiminopyridyl Iron Complexes

1Introduction Polyolefin industry arrives the option to transfer from multiple-site systems of the classical Ziegler-Natta catalysts to more sophisticated single-site catalysts. The late-transition metal compounds were traditionally assumed with poor polymerization properties due to the highly competitive chain-termination step, and produced the short-chain oligomers up to 40 carbon atoms (SHOP catalysts). Recently the polyolefins employing latetransition metal complexes as catalysts became a hot research subject with the pioneering works by Brookhart and Gibson. It is promising for nickel catalysts to use solely ethylene as monomer for highly branched polyethylenes, and the designed nickel catalysts were not useful in industry. It is critical time to investigate the relationship of coordination modes of nickel complexes and its catalytic activities and the properties of resultant polyethylenes.     

Ethylene Oligomerization and Polymerization： Alternative Iron Catalysts beyond 2,6-Bisiminopyridyl Iron Complexes

Polyolefin industry arrives the option to transfer from multiple-site systems of the classical Ziegler-Natta catalysts to more sophisticated single-site catalysts. The late-transition metal compounds were traditionally assumed with poor polymerization properties due to the highly competitive chain-termination step, and produced the short-chain oligomers up to 40 carbon atoms （SHOP catalysts）. Recently the polyolefins employing latetransition metal complexes as catalysts became a hot research subject with the pioneering works by Brookhart and Gibson. It is promising for nickel catalysts to use solely ethylene as monomer for highly branched polyethylenes, and the designed nickel catalysts were not useful in industry. It is critical time to investigate the relationship of coordination modes of nickel complexes and its catalytic activities and the properties of resultant polyethylenes.     

Alternative Models of Iron and Cobalt Catalysts for Ethylene Oligomerization and Polymerization

1 Results Great progresses have been made in the field of transition metal-based complexes as catalytic precursors for olefin oligomerization and polymerization,in which the core subjects will remain as “know and how“ to develop novel catalysts both in academic and industrial consideration.The key advantage of iron and cobalt catalyst for ethylene polymerization is to produce vinyl-type polyethylenes.Therefore following the pioneering works of bis(imino) pyridyl iron and cobalt catalyst by Brookhart[1] ...     

The Mechanism of Cumene Peroxidation Catalyzed by Cobalt(Ⅱ)-Chelated Copolymer

1Introduction The functionalised polymers, especially for chelating polymer, have been employed to considerable effects in organic synthesis for several decades. The use of polymer groups as ligands permits the ligand surroundings to be varied and regulation of the catalytic properties of the complexes because of the flexibility of the polymer chains, their ability to adopt various conformations, and the possibility of creating various spatial distributions of metal centers immobilized on the polymer chains[1,2]. In our recently studies[3-5], the chelating copolymer with imino-diacetic acid chelating group in the polymer side chain was manufactured, and which can increase effectively amount of the chelating group within the polymer. Meanwhile, the high catalysis performance in organic synthesis had also been proved via benzaldehyde and cumene peroxidation. For cumene peroxidation,it is hardly to find such a simple catalyst with high conversion and selectivity due to hydroperoxide decomposition by a radical mechanism. The cumene peroxidation by catalyst system and its reaction mechanism as well as the kinetic study are popularly investigated object for many researchers[6-9]. However, the reaction mechanism still does not clear owing to the by-products will be produced following the different catalysts used.     

Comparison of Parallelization Strategies for Min-Sum Decoding of Irregular LDPC Codes

Low-Density Parity-Check （LDPC） codes are powerful error correcting codes. LDPC decoders have been implemented as efficient error correction codes on dedicated VLSI hardware architectures in recent years. This paper describes two strategies to parallelize min-sum decoding of irregular LDPC codes. The first implements min-sum LDPC decoders on multicore platforms using OpenMP, while the other uses the Compute Unified Device Architecture （CUDA） to parallelize LDPC decoding on Graphics Processing Units （GPUs）. Empirical studies on data with various scales show that the performance of these decoding processes is improved by these parallel strategies and the GPUs provide more efficient, fast implementation decoder.     

A method to compress vibration signals using wavelet packet transformation combined with sub-band vector quantization

A novel compression method for mechanical vibrating signals,binding with sub-band vector quantization （SVQ） by wavelet packet transformation （WPT） and discrete cosine transformation （DCT） is proposed.Firstly,the vibrating signal is decomposed into sub-bands by WPT.Then DCT and adaptive bit allocation are done per sub-band and SVQ is performed in each sub-band.It is noted that,after DCT,we only need to code the first components whose numbers are determined by the bits allocated to that sub-band.Through an actual signal,our algorithm is proven to improve the signal-to-noise ratio （SNR） of the reconstructed signal effectively,especially in the situation of lowrate transmission.     

Cross-layer resource allocation based on potential game theory in multi-cell OFDMA networks

A cross-layer resource allocation scheme based on potential game （CLRA _ PG） is proposed for the downlink multi-cell orthogonal frequency-division multiple-access （OFDMA） system with universal frequency reuse.As a method to mitigate inter-cell interference （ICI）,base station coordination has been considered.In the process of the objective function modeling,this paper adopts a pricing mechanism which not only maximizes the individual utility but also considers the interference to other users.Based on the potential game theory,the objective problem is converted to a potential function which can be easily solved.The Karush-Kuhn-Tucker （KKT） conditions and the iterative water-filling algorithm are employed to solve the constraint objective optimization problem.Moreover,extensive simulations are conducted to evaluate how the pricing factors affect the algorithm.At the same time,comparing with the traditional policy,our simulation results show that the proposed scheme can significantly improve the performance of the system.     

Impact of public name resolving services on Akamai

To enhance user perceived performance,Akamai＇ s content distribution network （CDN） utilizes the domain name system （DNS） effectively to redirect users to close-by content replicas over short time scale.The use of DNS redirection has brought a significant advantage to Akamai＇ s CDN.However,the reliance on DNS also poses a fundamental threat to Akamai＇ s content distribution model.In particular,systematic evaluation and quantification illustrates the impact of recent emerging public DNS resolving services on Akamai＇ s CDN,including the degradation of corresponding user perceived performance and the benefit damnification of collaborating internet services providers （ISPs） that host Akamai＇ s edge servers.The measurement demonstrates that a considerable penetration of public DNS resolving services （e.g.,OpenDNS and GoogleDNS） effectively corrupts the Akamai＇ s serving model,namely the large-scale server distribution and quick DNS redirection.     

Synthesis and Characterization of Poly[ 2, 2- （m-phenylene） -5, 5-bibenzimidazole ] in 1-butyl-3-methylimidazolium Chloride

Poly[2,2-(m-phenylene)-5,5-bibenzimidazole](mPBI)were synthesized by mixing 3,3’,4,4’-tetraaminobiphenyl and isophthalic acid in 1-butyl-3-methylimidazolium chloride([BMIM]Cl).Intrinsic viscosity of mPBI polymers was 0.67 dL/g which was measured in 96%sulfuric acid.The polymer was characterized by Fourier transform infrared spectroscopy(FTIR),nuclear magnetic resonance(1H-NMR),and thermogravimetric analysis(TGA).The effects of polymerization conditions on the intrinsic viscosity of mPBI were investigated.It showed that the molecular weight of polymer mainly depended on pre-reaction time and reaction temperature.Comparison of structure and properties of mPBI synthesized in ionic liquids(ILs)and polyphosphoric acid was also reported.It indicates that the ionic liquids are a kind of good solvents in synthesis process of mPBI and ionic liquids mainly affect molecular weight of mPBI.     

Acquiring synonymous attribute phrases for named entities via online encyclopedia

In this work,an approach is proposed to acquire synonymous attribute phrases of named entities （NEs） from an online encyclopedia.Synonymous attribute phrases are the phrases that express the same attribute with different surface forms for a class of NEs.Specifically,the proposed approach is composed of three stages.Firstly,the entries related to a given NE class are automatically selected from an online encyclopedia.Secondly,attribute phrases are extracted based on the statistics of phrase frequency.Thirdly,synonymous attributes are identified in a pairwise manner through a classification framework combining multiple features.The proposed approach is applied on Baidu Baike,a Chinese online encyclopedia,for four different NE classes.Experimental results show that the approach obtains an average precision of 74％ and an average F-value of 65％ for the four NE classes.In particular,thousands of synonymous attribute phrase pairs are acquired for each class,which demonstrates the effectiveness of the proposed approach.     

A Buffer Management Scheme for Packet Queues in MANET

We introduce a new scheme of buffer management to handle packet queues in Mobile Ad hoc Networks （MANETs） for fixed and mobile nodes. In this scheme, we try to achieve efficient queuing in the buffer of a centrally communicating MANET node through an active queue management strategy by assigning dynamic buffer space to all neighboring nodes in proportion to the number of packets received from neighbors and hence controlling packet drop probabilities. Our simulation study reveals that the proposed scheme is a way to improve the buffer management for packet queues in MANET nodes in terms of packet loss ratio, transmission efficiency, and some other important system parameters.     

An adaptive pipelining scheme for H.264/AVC CABAC decoder

An adaptive pipelining scheme for H.264/AVC context-based adaptive binary arithmetic coding （CABAC） decoder for high definition （HD） applications is proposed to solve data hazard problems coming from the data dependencies in CABAC decoding process.An efficiency model of CABAC decoding pipeline is derived according to the analysis of a common pipeline.Based on that,several adaptive strategies are provided.The pipelining scheme with these strategies can be adaptive to different types of syntax elements （SEs） and the pipeline will not stall during decoding process when these strategies are adopted.In addition,the decoder proposed can fully support H.264/AVC high 4 ∶ 2 ∶ 2 profile and the experimental results show that the efficiency of decoder is much higher than other architectures with one engine.Taking both performance and cost into consideration,our design makes a good tradeoff compared with other work and it is sufficient for HD real-time decoding.     

Exploration on ecological regulation of the reservoirs

Reservoir regulation process in the Yangtze River basin is mainly divided into two types of flood regulation and initiating benefit regulation. The present reservoir management system and operation mode are mainly for dealing with or coordinating of flood control and benefit initiation as well as benefit distribution among various beneficial functions. From the view point of river ecosystem protection, the current regulation mode has two kinds of problems ： firstly, most of the reservoir regulation plans do not consider ecosystem protection at downstream of dams and needs of environment protection in reservoir areas; secondly, integrated regulation or management of water resources is ignored. It is very necessary to improve reservoir regulation mode, bearing problems faced by regulation of the Three Gorges reservoir and issues related to cascade development and regulation in Tuojiang and Minjiang River basins in mind. In accordance with the concept of scientific development, and the philosophy of ＂ensuring a healthy Yangtze River and promoting the harmony between human and water＂, taking flood control, benefit initiation and eco-system as a whole, this paper put forward the basic consideration to improve reservoir regulation as follows ： on the basis of requirements of ecosystem protection at downstream of dams and needs of environment protection in reservoir areas, we should bring the functions of reservoir such as flood control and benefit initiation into full play, control the negative influence to the ecosystem at downstream of dams and the environment in reservoir areas in an endurable scope, and restore the ecosystem and the environment step by step. This paper put forward the relevant regulation process aiming at the idiographic problems such as protection of ecosystem at downstream of dams and environment in reservoir areas, protection of aquatic wildlife species and fish species, regulation of sediment and protection of wetland.     

Mycelial fermentation and medicinal properties of a valuable medicinal fungus Cordyceps sinensis Cs-HK1

Cordyceps sinensis （Cs） or Dongchongxiacao in Chinese is a rare and precious medicinal mushroom. In this work, a Tolypocladium sp. fungus named Cs-HK1 was isolated from a natural Cs fruiting body, and its ultraviolet （UV）, infrared （IR） and high-performance liquid chromatography （HPLC） spectra all exhibited high degrees of matching to those of natural Cs, indicating the similarity of chemical composition. A crude polysaccharide （PS） fraction isolated from Cs-HKI fungal mycelium showed significant antitumor activity, inhibiting melanoma tumor growth in mice. The PS-treated mice showed significantly higher serum interferon-y （IFN-y） level and higher proliferation rate of lymphocytes ex vivo than the control animals, suggestive of the immunomodulatory activity of the PS fraction. In cell cultures, the PS fraction caused a significant and dose-dependent inhibitory effect on the proliferation of two cancer cell lines, B16/neu mouse melanoma and MDA-MB-231 human breast cancer cells, but not on normal spleen lymphocytes in vitro. Most of these bioactivities of the Cs- HK1 fungus were comparable to or even greater than those of natural Cs. The results showed that Cs-HK1 fungus may be a functional substitute for the natural Cs in health food and herbal medicine.