Metallocenes and other transition metal compounds comprise a new generation of single site catalysts for the production of precisely designed polyolefins and engineering plastics. The discovery of metallocene methylalumoxane (MAO) catalysts has opened a frontier in the area of polymer synthesis and processing. A great number of symmetric and chiral zirconocenes have been synthesized to give isotactic,syndiotactic,isoblock,or stereoblock polymers with increased impact strength and toughness,better melt characteristics or elasticity,and improved clarity in films. Cycloolefin copolymers (COC) and syndiotactic polystyrene can be produced by metallocene catalysts. These are new types of polymers with special properties and a high potential as engineering plastics. Norbornene-ethene copolymers are most interesting for technical uses because of the easily available monomers. Due to different incorporation values of the cyclic olefin in the copolymer,the glass transition temperature can vary over a wide range and reaches 180 °C.

A three-dimensional, exact analysis is presented in this paper for the problem of an external circular crack in a transversely isotropic piezoelectric medium subjected to arbitrary antisymmetric shear loading. A recently proposed general solution of three-dimensional piezoelectricity is employed. It is shown that four quasi harmonic functions involved in the general solution can be represented by just one complex potential. Previous results in potential theory are then used to obtain the exact solution of the problem. For point shear loading, Green\'s functions for the elastoelectric field are derived in terms of elementary functions.

The equation of the suspension-gas non-streamwise complex disturbance velocity ratio near the injection area of moving jet was theoretically derived by using a phase-coupled model and stability theory. Then the ratio curves were obtained by the finite difference method based on the asymptotic method and the Euler conservative difference scheme.Analysis of the curves yielded conclusions on the disturbance properties of suspensions and effects of the natures of the flow-field and the properties of the suspensions on the suspensions\' ability to track the disturbed gas flow are presented in this paper.

The superconductor sample had periodic distribution of pinned region (with length of L_p) and unpinned region (with length of L−L_p) along the driving force direction. Numerical study on the influence of the distribution of pinning centers on pinning of the two-dimensional vortex system showed that the critical depinning force F_c, beyond which the vortex system begins to depin,increases with increase of L_p, indicating that the homogeneity of pinning centers helps to enhance the critical electric current of a superconductor. We found that the critical depinning force F_c depends logarithmically on L/L_p.

Construction cost control is a complex system engineering. The traditional controlling method cannot dynamically control in advance the construction cost because of its hysteresis. This paper proposes a computer simulation based construction cost integrated control method, which combines the cost with PERT systematically, so that the construction cost can be predicted and optimized systematically and effectively. The new method overcomes the hysteresis of the traditional systems, and is a distinct improvement over them in effect and practicality.

Sanitary landfilling is the most important method of municipal solid waste disposal in China. Landfill sites are always set up in mountain valley, on plain or beside seashore. A complete landfill consists of base system, cover system, and leachate collection and gas extraction system. This paper reviews the state-of-the-art landfilling technology in China and collection discusses research projects for engineers.

Short circuit is a serious fault in power network. Some novel circuit topologies of current limiter using power electronic technology have been developed, which can limit the fault current to any desired level without much penalty. The operating principle and control strategies of such current limiters are discussed in detail. Simulation and experimental results are given to verify the performance of the current limiter, which can meet the requirements set for locations of bus tie, feeder, as well as the main transformer in the distribution network.

Traditional DPIV (Digital Particle Image Velocimetry) methods are mostly based on area-correlation (Willert,C.E.,1991). Though proven to be very time-consuming and very much error prone, they are widely adopted because of they are conceptually simple and easily implemented, and also because there are few alternatives. This paper proposes a non-correlation, conceptually new, fast and efficient approach for DPIV, which takes the nature of flow into consideration. An Incompressible Affined Flow Model (IAFM) is introduced to describe a flow that incorporates rational restraints into the computation. This IAFM, combined with a modified optical flow method-named Total Optical Flow Computation (TOFC), provides a linear system solution to DPIV. Experimental results on real images showed our method to be a very promising approach for DPIV.

The Hybrid Fiber-Coax (HFC) network is being paid close attention to in recent years as a bi-directional broadband access network.To achieve seamless connection with the backbone network,an Asynchronous Transfer Mode (ATM) Network Network Interface (NNI) cell format is used as the basic transmission packet unit in the HFC system. As the transmission condition of the HFC system\'s upstream channel is bad, two improved header error control (HEC) schemes, i.e. the improved HEC and the cell interleaving technique,are employed to guarantee the packet integrity. Theoretical analysis of the results showed that the improved HEC and the cell interleaving technique are applicable to isolated random errors and burst errors, respectively.

A novel charge/discharge equalization scheme is proposed in this paper. According to the states of batteries, two equalizing methods are adopted for equalization during different charging and discharging phases. A switched capacitor is utilized during high rate charging and discharging. During the later period of charging and discharging, an auxiliary low power DC/DC converter and the inherent switch modules of a control/monitor unit are used. So it is very simple and efficient. With the developed equalizer, the lifetime of a series battery string can be extended.

This paper presents a theory on premix fuel combustion at near isosceles triangle type rate of heat release, describes the measures taken for the combustion system, points out its many theoretical advantages, and that it can solve effectively the problems of rough running, fuel consumption and exhaust emission. Two squish lip type combustion chambers are designed to match separately with multiple holes injector and conical spray type injector in order to achieve premix combustion at near isosceles triangle type rate of heat release. Experimental studies on two single cylinder diesel engines showed that premix combustion at isosceles triangle type rate of heat release resulted in longer ignition delay period, larger amount of fuel injected into cylinder during the ignition delay period, lower maximum pressure,better fuel economy, and better exhaust emission.

The solution of quadratic programming problems is an important issue in the field of mathematical programming and industrial applications. In this paper, we solve convex quadratic programming by a potential-reduction interior-point algorithm. It is proved that the potential-reduction interior-point algorithm is globally convergent. Some numerical experiments were made.

Providing a wider movement range of virtual camera is an unsolved problem for state-of-the-art image-based rendering system. In this paper, we present a new image based rendering technology called panoramic mosaics of slit images with depth that can provide large virtual camera motion region for some scenes. By limiting camera motion to a horizontal plane only,a slit image with united depth value is used as the rendering element. The panoramic mosaics of slit images with depth are easy to capture, and the data size is as small as that of panorama. We present here the capturing,construction as well as rendering process of panoramic slit images mosaic with depth. In addition, we present the join up process of multiple panoramic slit images mosaic with depth.

Suppose {X,X_n;n≥1} is a sequence i.i.d.r.v. with EX=0 and EX²<∞. Shao (1995) proved a conjecture of Révész (1990): if P(X=±1)=1/2, then ... Furthermore he conjectured that ... In this paper we prove that if sup_b>0P(X=b)≥P(X=0) then this conjecture is true.

Selective dissolution with ammonium oxalate was carried out to extract amorphous matter in some kaolins from China. Ammonium oxalate extraction is an effective method to extract amorphous constituents without destroying the kaolinite crystalline structure. The study showed that, absolute amounts of amorphous constituents in kaolins are in the order Al>Si>Fe, but that relative amounts are in the order Fe>Al>Si. The amorphous phases are probably mainly in the form of separate particles, or colloidal particles absorbed on the surface of kaolinite particles.Compared to older kaolins, younger kaolins contain much more amorphous iron content.

Studies were conducted on specific core collections constructed on the basis of different traits and sample size by the method of stepwise cluster with three sampling strategies based on genotypic values of cotton. A total of 21 traits (11 agronomy traits, 5 fiber traits and 5 seed traits) were used to construct main core collections. Specific core collections,as representative of the initial collection, were constructed by agronomy,fiber or seed trait, respectively. As compared with the main core collection, specific core collections tended to have similar property for maintaining genetic diversity of agronomy, seed or fiber traits.Core collections developed by about sample size of 17% (&Pmacr;₂=0.17) and 24% (&Pmacr;₁=0.24) with three sampling strategies could be quite representative of the initial collection.

Objective: To determine the role of microsatellite alterations in carcinogenesis of colorectal carcinoma (CRC). Methods: Alterations of 10 microsatellite loci from 5 different chromosomes were detected in 92 colorectal cancers and their paired normal mucosa by PCR, denatured polyacrylamide gel electrophoresis and silver staining. Associations of microsatellite alterations with clinopathologic parameters were statistically clarified.Results: Alterations of microsatellite were classified into microsatellite instability type I, type II and loss of heterozygosity (LOH). The carcinoma with ≥30% loci microsatellite alterations was defined as replication error(RER) positive tumors. Of 92 cases, 14 were RER+. Microsatellite alterations of P53₍₁₎ and D18S363 loci (64.29%) was most commonly identified in the RER+ tumors. RER+ were more commonly seen in poorly differentiated carcinomas and tended to occur in mucoid carcinomas. The type of microsatellite alterations varied in different histological types of CRC. Conclusions: Microsatellite alteration is a common molecular event in CRC. Different microsatellite loci showed various biologic significance. P53₍₁₎ and D18S363 should be essentially detected loci that can show the RER status of tumors.

Objective: To determine the effective nucleotide sites of ribozymes against HCV, and obtain a highly effective, nontoxic and inexpensive antisense ribozyme specific for HCV. Methods: Two effective ribozymes, targeted to HCV 5\'NC region and C region, were designed and synthesized.Eukaryotic expression vectors, pSV2-gpt. CD-SR, containing either HCRZNC or HCRZC were constructed and transfected into MT-2 cells, which had been infected by HCV. Quantitative PCR and hybridization were used to determine the effect of inhibition of HCV by ribozymes. Results: HCRZNC and HCRZC suppressed the replication of HCV by 54.7% and 2.1%, respectively. Furthermore, when both ribozymes were cotransfected into cells, they suppressed replication by 78.8%. Conclusion: Two specific antisense ribozymes have strong inhibitory effects on the replication of HCV in cultured cells, and have better effect when used together.

Endoscopic retrograde cholangiopancreatography(ERCP) was performed preoperatively on 29 patients suffering from hepatocellular carcinoma (HCC) invading bile ducts. The outstanding features were: 1. Most of the filling defects were situated within the common, right or left hepatic duct associated with proximal bile duct dilatations (17 cases); 2. Tumor encasement resulted in localised or diffused irregular strictures and dilatations (9 cases); 3. Displacemen t and stretching of the intrahepatic ducts by pressure of tumor mass (3 cases). These features are different from that in cholangiocarcinoma. ERCP should be considered as an important diagnostic procedure for HCC. It is especially useful for cases with obscure intrahepatic duct dialatation and /or an increase of AFP, and will help early diagnosis of HCC.

To study the function of transforming growth factor β₁ (TGF-β₁) and transforming growth factor-β type II receptor (TGF-βR II) in varying stages of colorectal adenoma during neoplastic transformation, fifty-five cases of resected colorectal adenomas were examined immunohistochemically. Our results showed that the expression of TGF-β₁ ranged from high to low, with the progression of low-grade to high-grade dysplasia of adenomas to carcinoma. And there was significantly different expression of TGF-β₁ between moderate and high dysplasia adenomas (P<0.05), but no significantly different expression of TGF-β R II was found among varying stages of adenomas. Our results suggested that the quantities of TGF-β₁ secreted by adenoma cells decrease dramatically in moderate to severe dysplasia colorectal adenomas. It is the decreased secretion of TGF-β₁, rather than the mutated TGF-βR II that may play an important role in transforming colorectal adenomas to adenocarcinomas.

Objective: To study the relationship between the size of pontocerebellar angle tumor and audiology. Methods: Retrospective analysis of accoustically evoked brainstem response (ABR) waveforms and pure tone threshold in 27 subjects with tumor of pontocerebellar angle. Results: ABR wave forms and pure tone threshold were significantly affected statistically by the size of tumors, especially those tumor larger than 3 cm in diameter. Conclusion: The primary symptom of the patient was unilateral hearing loss. Early discovery of the lesion is important and ABR is a sensitive tool for early diagnose of the tumor.

With the emergence of Knowledge Economy and its penetration into every aspect of society, many industrial functions have been changing, including management and labor relations. In this paper, the author first presents a system view of management and labor relations under Knowledge Economy,and then based on it, elaborates on effect of Knowledge Economy on them, using the case of HP as demonstration. In the end, conclusion is made that new dynamic equilibration will develop, depending upon the dynamic power contrast of the above two subjects under dynamic changing circumstances of Knowledge Economy.

Zhejiang University, with a history of more than a hundred years, published a brand new English academic journal in the second millenium: Journal of Zhejiang University (SCIENCE). Our Editor-in-Chief, PAN Yun-he, proudly invited T. D. Lee and some famous scholars as the members of the editorial board. The aim of our Journal is to present the latest developments and achievements in scientific research in China and overseas to the world\'s scientific circles, specially to stimulate and promote academic exchange between Chinese scientists and their foreign counterparts everywhere. This Journal covers subjects in Science, Engineering, Agriculture, Medicine and Social Science. We hope that in the very near future, the Journal will be recognized by scholars all over the world, and that the name of the Journal will appear in the most popular indexing systems.