Search

In this paper, we propose a finite-time structure-preserving model reduction method based on the shifted Legendre polynomials for K-power bilinear systems. First, it aims to transform the K-power bilinear system into a general bilinear system and use the shifted Legendre polynomials expansions to obtain the approximate low-rank decomposition factors of the controllability and observability Gramians, which are calculated by the recurrence formulas. Second, the approximate balanced system of the K-power bilinear system is constructed by the corresponding projection transformation of each subsystem. Then, the reduced-order model is constructed by truncating the states corresponding to the small approximate singular values. Combined with the dominant subspace projection method, the reduction process is modified to alleviate the shortcomings that above method may unexpectedly result in unstable systems although the original one is stable. Finally, two numerical experiments are given to demonstrate the effectiveness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

In this work, a flowing material balance equation (FMBE) is established for undersaturated coalbed methane (CBM) reservoirs, which considers immobile free gas expansion effect at the dewatering stage. Based on the established FMBE, five straight-line methods are proposed to determine the control area, initial water reserve, initial free gas reserve, initial adsorbed gas reserve, original gas in place, as well as permeability at the same time. Subsequently, the proposed FMBE methods for undersaturated CBM reservoirs are validated against a reservoir simulation software with and without considering free gas expansion. Finally, the proposed methods are applied in a field case when considering free gas expansion effect. Validation cases show that the straight-line relationships for the proposed five FMBE methods are excellent, and good agreements are obtained among the actual reserves and permeabilities and those evaluated by the proposed five FMBE methods, indicating the proposed five FMBE methods are effective and rational for CBM reservoirs. Results show that a small amount of free gas will result in a great deviation in reserve evaluation; hence, the immobile free gas expansion effect should be considered when establishing the material balance equation of undersaturated CBM reservoirs at the dewatering stage. [ABSTRACT FROM AUTHOR]

Based on ecological niche theory, Microcystis Aeruginosa (MA) immobilized in the complex of polyvinyl alcohol (PVA) and sodium alginate (SA) crosslinked by CaCl, was treated as a new kind of special species, and its properties were investigated. Chlorophyll a was used to characterize the bioactivity of the immobilized MA. Results reveal that the gel beads have mechanical strength and chemical stability even under non-sterile harsh conditions, which may be attributed to the rarely seen structure (including three different layers: dense surface, tubular-shaped divergent structure and honeycomb crystal lattice layer) of the immobilized MA determined by scanning electron microscope (SEM). SEM also displays that more quantity of MA is attached to the inwall after cultivation, which demonstrates that the MA within beads maintains high bioactivity. Removal capacities on phosphorous (P) removal in wastewater in the presence and absence of the BG-11 medium were examined, and the removal ratios are 80.3% and 76.7%, respectively, which indicates that the beads without providing ample nutrients still have high capacity of P removal. In addition, control experiment, utilizing polyvinyl alcohol and sodium alginate (PVA-SA) beads without immobilized MA, demonstrates that MA within beads plays the key role in absorbing P. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the expression of SUMO-1 in human hepatocellular carcinoma (HCC) cell lines and clinical HCC samples. Methods: RT-PCR and Western blot were used to detect the expressions of SUMO-1 in HCC cell lines, clinical HCC samples,and the non-neoplastic liver tissues adjacent to HCC. After transfection of SUMO-1 siRNA into HCC cell line SMMC-7721, the expression levels of Bcl- 2, c- Myc and α-tubulin were examined, and MTT assay and cell cycle analysis were carried out as well. Results: Overexpressions of SUMO-1 were detected in HCC cell lines and clinical HCC samples, while the expression level of SUMO-1 in the non-neoplastic liver tissues was significantly lower ( P < 0.001). Transfection of SUMO-1 siRNA resulted in 73.43% of maximal silencing efficiency of SUMO-1 in 48 h. The expressions of Bcl- 2 and c- Myc were down-regulated coincidentally. SUMO-1 siRNA notably inhibited SMMC-7721 cells proliferation in vitro and increased the ratios of G2 phase and S phase in the cells. Conclusions: Owing to overexpression of SUMO-1 in HCC and its important role in the development of HCC, SUMO-1 could be a latent target in diagnosis and therapy of HCC. [ABSTRACT FROM AUTHOR]