重力场下单循环与双循环小通道热驱动比较研究

本文以实验的方法,对重力场下单循环与双循环小通道热驱动进行了比较研究。两者都是一端加热,一端冷却,利用彻体力场下流体的热驱动来实现换热。实验结果表明,在热流密度相同的情况下,双循环小通道比单循环具有更好的换热效果。因此,将微小循环通道换热运用于涡轮叶片的冷却时可以考虑采用双循环甚至多循环通道。     

Hispolon Induces Apoptosis,Suppresses Migration and Invasion of Glioblastoma Cells and Inhibits GBM Xenograft Tumor Growth In Vivo

Hispolon, a polyphenol compound isolated from Phellinus linteus, has been reported to exhibit antioxidant, antiproliferative, and antitumor activities. This study aimed to explore the antitumor effects of hispolon on glioblastoma multiforme (GBM) cells in vitro and in vivo. The results revealed that hispolon significantly inhibited GBM cell proliferation and induced apoptosis through caspase-9 and caspase-3 activation and PARP cleavage. Hispolon also induced cell cycle G2/M phase arrest in GBM cells, as supported by flow cytometry analysis and confirmed by a decrease in cyclin B1, cdc2, and cdc25c protein expressions in a dose- and time-dependent manner. Furthermore, hispolon suppressed the migration and invasion of GBM cells by modulating epithelial–mesenchymal transition (EMT) markers via wound healing, transwell assays, and real-time PCR. Moreover, hispolon significantly reduced tumor growth in DBTRG xenograft mice and activated caspase-3 in hispolon-treated tumors. Thus, our findings revealed that hispolon is a potential candidate for the treatment of GBM.     

一类平面微分系统极限环的存在唯一性

研究一类平面微分系统的极限环,利用Hopf分支理论得到了该系统极限环存在性的若干充分条件,利用Л.А.Чеpкас和Л..Иилевьтч的唯一性定理得到了极限环唯一性与稳定性的若干充分条件.     

Gray codes for column-convex polyominoes and a new class of distributive lattices

We introduce the problem of polyomino Gray codes, which is the listing of all members of certain classes of polyominoes such that successive polyominoes differ by some well-defined closeness condition (e.g., the movement of one cell). We discuss various closeness conditions and provide several Gray codes for the class of column-convex polyominoes with a fixed number of cells in each column. For one of our closeness conditions, a natural new class of distributive lattice arises: the partial order is defined on the set of m-tuples [S₁]×[S₂]××[S_m], where each S_i>1 and [S_i]={0,1,…,S_i−1}, and the cover relations are (p₁,p₂,…,p_m)(p₁+1,p₂,…,p_m) and (p₁,p₂,…,p_j,p_j+1,…,p_m)(p₁,p₂,…,p_j−1,p_j+1+1,…,p_m). We also discuss some properties of this lattice.     

A look at cycles containing specified elements of a graph

This article is intended as a brief survey of problems and results dealing with cycles containing specified elements of a graph. It is hoped that this will help researchers in the area to identify problems and areas of concentration.     

The orientable genus of some joins of complete graphs with large edgeless graphs

In an earlier paper the authors showed that with one exception the nonorientable genus of the graph with m≥n−1, the join of a complete graph with a large edgeless graph, is the same as the nonorientable genus of the spanning subgraph . The orientable genus problem for with m≥n−1 seems to be more difficult, but in this paper we find the orientable genus of some of these graphs. In particular, we determine the genus of when n is even and m≥n, the genus of when n=2^p+2 for p≥3 and m≥n−1, and the genus of when n=2^p+1 for p≥3 and m≥n+1. In all of these cases the genus is the same as the genus of K_m,n, namely ⌈(m−2)(n−2)/4⌉.     

A multisyringe sequential injection method for monitoring water in the energy cogeneration system of a municipal waste incinerator

Leading-edge urban solid waste ashing plants use burning heat energy to obtain electrical power. Water fed to their boilers for conversion into steam should be highly pure in order to minimize corrosion, scaling and similar phenomena, which can lead to malfunctioning and a reduced useful life but can be avoided by proper management and control of the water supply. In this work, we developed a multiparameter monitor based on multisyringe sequential injection for the sequential determination of up to eight important parameters, namely: pH, specific and acid conductivity, hydrazine, ammonium, phosphate, silicate and total iron.Acid conductivity was determined by passing the sample through a cation-exchange resin in order to retain ammonium ion and release protons. This parameter was deemed the most accurate indicator of dissolved solids in boiler water. Chemical parameters were determined spectrophotometrically: hydrazine by reaction with p-dimethylaminobenzaldehyde, ammonium by the modified Berthelot reaction, iron with o-phenanthroline, and phosphate and silica by formation of a molybdoheteropoly blue dye in the presence of ascorbic acid as reductant. Use of the optimum chemical and physical operating conditions provided 3s_blank detection limits of 0.01 mg l⁻¹ N₂H₄, 0.13 mg l⁻¹ NH₄⁺, 0.04 mg l⁻¹ Fe, 0.03 mg l⁻¹ SiO₂ and 0.05 mg l⁻¹ PO₄³⁻, and relative standard deviations not greater than 2.5%. The methods integrated in the proposed monitor were successfully applied to real samples from the water-steam cycle at the Son Reus ashing plant in Palma de Mallorca (Spain).     

Piezoelectric control of Hopf bifurcations: A non-linear discrete case study

Linear and non-linear analyses of a piezoelectric controlled non-linear Ziegler column are carried out in this paper. The aim is to evaluate the effects of a linear piezoelectric element on the Hopf bifurcations of the non-linear mechanical system, triggered by the non-conservative follower force. To this end a linear stability analysis, showing the performances of the controller in shifting forward the critical load of the uncontrolled system, is carried out and the role of the electro-mechanical coupling parameter and of the mechanical damping is investigated. The beneficial effects of the controller on the amplitude of the limit cycle occurring in the post-critical field are also discussed.     

高温超声拉压疲劳试件设计与温度自动控制

本文较深入地开展了高温环境条件下的超声拉压疲劳实验系统研究,深入分析了试件温度高精测量与自动控制和高温试件设计的关键问题。实验系统可以实现高温环境条件下大于1010周次超高周次的疲劳加载。本实验系统利用传统超声疲劳试验机,使用非接触式红外测温仪对试件温度进行实时动态监测,采用间歇振动的方法保证温度波动小于±3℃。实验结果显示,采用本系统得到的实验结果与传统疲劳加载方式的结果一致性很好。本文工作为进一步开展高温环境条件下金属材料高温超高周(1010周次)疲劳损伤和疲劳破坏机理研究提供了新的有效的平台。