Mobility: a double-edged sword for HSPA networks

This paper presents an empirical study on the performance of mobile High Speed Packet Access (HSPA, a 3.5G cellular standard) networks in Hong Kong via extensive field tests. Our study, from the viewpoint of end users, covers virtually all possible mobile scenarios in urban areas, including subways, trains, off-shore ferries and city buses. We have confirmed that mobility has largely negative impacts on the performance of HSPA networks, as fast-changing wireless environment causes serious service deterioration or even interruption. Meanwhile our field experiment results have shown unexpected new findings and thereby exposed new features of the mobile HSPA networks, which contradict commonly held views. We surprisingly find out that mobility can improve fairness of bandwidth sharing among users and traffic flows. Also the triggering and final results of handoffs in mobile HSPA networks are unpredictable and often inappropriate, thus calling for fast reacting fallover mechanisms. We have conducted in-depth research to furnish detailed analysis and explanations to what we have observed. We conclude that mobility is a double-edged sword for HSPA networks. To the best of our knowledge, this is the first public report on a large scale empirical study on the performance of commercial mobile HSPA networks

Effects of matrine on collagen proliferation and TNF-α, TGF-β1 and CTGF in atrial tissues of dogs with persistent atrial fibrillation

目的 探讨苦参碱对犬心房颤动（房颤）心房肌组织中胶原合成以及肿瘤坏死因子（tumor necrosis factor alpha,TNF-α）、转化生长因子（transforming growth factor-β1，TGF-β1）和结缔组织生长因子（connective Tissue Growth Factor，CTGF）表达变化的影响。方法 健康比格犬10只采用快速右心室起搏造房颤模型，随机分成房颤组和房颤+苦参碱组各5只。采用天狼星红染色，计算胶原容积分数（collagen volume fraction，CVF）以测定纤维化程度；采用免疫组织化学法检测右心房TNF-α、TGF-β1和CTGF的蛋白表达情况；用逆转录-聚合酶链反应（RT-PCR）技术检测TNF-α、TGF-β1和CTGF的mRNA水平表达情况。结果 与房颤组相比，房颤+苦参碱组纤维化程度降低，CVF明显下降（P＜0.05），TNF-α、TGF-β1和CTGF蛋白表达水平下降，且TNF-α和TGF-β1的mRNA表达水平显著下降（P＜0.05，P＜0.01）。结论 苦参碱可能通过抑制TNF-α、TGF-β1和CTGF的表达，抑制房颤心房肌胶原合成，改善心房组织纤维化程度。Objective:To study the effects of matrine (mat) on collagen synthesis and expression of tumor necrosis factoralpha (TNF-α), and transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF) in atrial tissues of dogs with persistent atrial fibrillation (AF). Methods : Ten healthy beagle dogs were randomly divided into two groups: AF group (n=5) and AF/Mat group (n=5), using right ventricular pacing to establish AF model. The collagen volume fraction (CVF) in atrial tissue were detected by sirius red staining to determine the level of fabrication. The level of TNF-α, TGF-β1 and CTGF were detected by immunohisto-chemistry. The mRNA expression level of TNF-α, TGF-β1 and CTGF were detected by reverse transcription-polymerase chain reaction (RT-PCR). Results:  Compared with the AF group, the fabriation level of AF/Mat was decreased obviously (P<0.05), the expression levels of TNF-α, TGF-β1 and CTGF were decreased, and the mRNA expression level were decreased significantly in atrial tissues (P<0.05 and P<0.01). Conclusion: Matrine may inhibits fabrosis in atrial tissues through inhibition collagen proliferation and expression of TNF-α, TGF-β1 and CTGF

Application review on underwater radiated noise measurement by using a vessel’s own towed array

Compared with the traditional fixed test and auxiliary measurement ship, the measurement of the underwater radiated noise by using a vessel’s own towed array has many advantages, such as flexible, convenient, low cost, and so on. In this paper, the previous researches on this method are summarized. From the view of implementing this technique, the method has been divided into four aspects: towed array design, U-turn manoeuvre, underwater sound propagation and towed array signal processing. Overall, this technology is practical and feasible, and has a good application prospect. Next, combined with a large number of experiments, further study on the selected principle of the towed array and U-turn technical indicators will be done

Mass spectra of hidden heavy-flavor tetraquarks with two and four heavy quarks

Inspired by the observation of the $X(6900)$ by LHCb and the $X(6600)$ (with mass $6552\pm 10$ $\pm 12$ MeV) recently by CMS and ATLAS experiments of the LHC in the di-$J/\Psi$ invariant mass spectrum, we systemically study masses of all ground-state configurations of the hidden heavy-flavor tetraquarks $q_{1}Q_{2}\bar{q}_{3}\bar{Q}_{4}$ and $Q_{1}Q_{2}\bar{Q}_{3}\bar{Q}_{4}$ ($Q=c,b$;$q=u,d,s$) contaning two and four heavy quarks in the MIT bag model with chromomagnetic interaction and enhanced binding energy. Considering color-spin mixing due to chromomagnetic interaction, our mass computation indicates that the observed $X(6600)$ is likely to be the $0^{++}$ ground states of hidden-charm tetraquark $cc\bar{c}\bar{c}$ with computed masses $6572$ MeV, which has a $0^{++}$ color partner around $6469$ MeV. The fully bottom system of tetraquark $bb\bar{b}\bar{b}$ has masses of 19685 MeV and 19717 MeV for the the $0^{++}$ ground states. Further computation is given to the tetraquark systems $sc\bar{s}\bar{c}$, $sb\bar{s}\bar{b}$, $cb\bar{c}\bar{b}$, $nc\bar{n}\bar{c}$ and $nb\bar{n}\bar{b}$, suggesting that the $Z_{c}(4200)$ is the tetraquark $nc\bar{n}\bar{c}$ with $J^{PC}=1^{+-}$. All of these tetraquarks are above their lowest thresholds of two mesons and unstable against the strong decays

Three-Body Abrasion Sensitivity of Tribo-Mechanical Components Under Fluid Film Lubrication

Mechanical Engineerin