MOBILITY CONTROL IN WIRELESS SENSOR NETWORK

Wireless sensor networks (WSNs) have become one of the most important topics in wireless communication during the last decade. WSNs integrates many different technologies such as in hardware, software, data fusion, and applications. Hence, WSNs has received recently special research activities. WSNs have so many applications in different areas such as health-care systems, monitoring and control systems, rescue systems, and military applications. Since WSNs are usually deployed with large numbers of nodes in wide areas, they should be reliable, inexpensive, with very low power consumption, and with high redundancy to preserve the life-time of the whole network. In this M.Sc. thesis we consider one extremely important research topic in WSNs which is the mobility control. The mobility control is analyzed theoretically as well as with extensive simulations. In the simulation scenarios, static sensor nodes are first randomly deployed to the decided area. Then a reference trajectory for the mobile node is created based on the observed point phenomena, and the network guides the mobile node to move along the trajectory. A simulation platform called PiccSIM is used to simulate the scenarios. It is developed by the Communication and Control Engineering Groups at Helsinki University of Technology (TKK). The obtained results from these simulations are discussed and analyzed. This work opens the doors for more real applications in this area in the nearby future.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Improved mechanical property and corrosion and wear resistance of high-voltage aluminium wires by micro-arc oxidation coating

New surface treatments are required to improve the resistance of high-voltage aluminium conductors to corrosion and wear. This paper describes the preparation of ceramic coatings on the surface of aluminium wires by the micro-arc oxidation (MAO) technology. The surface morphology, mechanical and tribological properties, electrical resistivity, wear and corrosion resistance of the MAO-treated aluminium samples are examined and compared not only with the untreated samples but also between the use of different current densities in the MAO process. The MAO treatment can increase the tensile strength of the wire and mitigate the wire elongation at excessive high temperature. In addition, the increased surface hardness and the overlapping micro-porous distribution of the MAO coating improve the resistance of the treated sample to wear and corrosion respectively, protecting the aluminium substrate from the joint effects of wear and corrosion. Furthermore, the MAO coating has little impact on the electrical resistivity of aluminium conductors and can mitigate the resistivity change due to corrosive damage. The MAO technology providing a potential idea for the surface treatment of aluminium conductors is expected to extend the service life and alleviate maintenance needs of aluminium conductors operating in harsh environments

Hippo Signaling Suppresses Cell Ploidy and Tumorigenesis through Skp2

大多数真核生物的体细胞是二倍体，即仅含有两组染色体，分别遗传自父本和母本。而一些特定组织如心脏、肝脏等就含有多倍体细胞，特别是肝脏组织含有较高比例的四、八倍体等多倍体细胞。肝脏是人体的重要解毒器官，同时酒精、肝炎病毒等毒性物质或毒性代谢物容易诱发肝细胞的基因突变，多倍体被认为有利于提供代偿性的正常基因来维持肝脏稳态。然而肝脏受损后，多倍体细胞将会受胁迫进行增殖，再生修复受损的肝组织。因此研究机体调控多倍体细胞产生及多倍体细胞进行细胞分裂的调控机理对于理解肝癌的发病机理和肝癌的治疗至关重要。Hippo信号通路在调节组织成体干细胞的分化和增殖，调控器官再生与尺寸大小中具有重要作用。深入研究发现, Hippo信号通路下游效应分子YAP通过AKT-SKP2信号促进二倍体细胞向多倍体转化及多倍体细胞的生长增殖。本项研究阐明了Hippo缺失及YAP激活促进多倍体细胞产生及增殖作为肝癌发生发展中的一个重要机制，为肝癌诊疗提供了新的策略。 周大旺，博士，厦门大学生命科学学院教授、副院长、国家杰出青年基金获得者。【Abstract】Polyploidy can lead to aneuploidy and tumorigenesis. Here, we report that the Hippo pathway effector Yap promotes the diploid-polyploid conversion and polyploid cell growth through the Akt-Skp2 axis. Yap strongly induces the acetyltransferase p300-mediated acetylation of the E3 ligase Skp2 via Akt signaling. Acetylated Skp2 is exclusively localized to the cytosol, which causes hyper-accumulation of the cyclin-dependent kinase inhibitor p27, leading to mitotic arrest and subsequently cell polyploidy. In addition, the pro-apoptotic factors FoxO1/3 are overly degraded by acetylated Skp2, resulting in polyploid cell division, genomic instability, and oncogenesis. importantly, the depletion or inactivation of Akt or Skp2 abrogated Hippo signal deficiency-induced liver tumorigenesis, indicating their epistatic interaction. Thus, we conclude that Hippo-Yap signaling suppresses cell polyploidy and oncogenesis through Skp2.该研究工作获得了国家自然科学基金委、国家重点基础研究发展计划(973)项目、青年千人计划和中央高校基本科研基金的资助。 The Yap (S127A) transgenic mice were kindly provided by Dr. Fernando Camargo from Harvard Medical School, Boston, MA. D.Z. and L.C. were supported by the National Natural Science Foundation of China (31625010,U1505224, and J1310027 to D.Z.; 81422018, U1405225, and 81372617 to L.C.; 81472229 to L.H.), the National Basic Research Program (973) of China (2015CB910502 to L.C.), the Fundamental Research Funds for the Central Universities of China-Xiamen University (20720140551 to L.C. and 2013121034 and 20720140537 to D.Z.)

Hippo信号通路通过调控Skp2活性从而抑制细胞多倍体产生及肝癌发生

文章简介在这项研究中,课题组揭示了Hippo信号通路在限制肝脏细胞的染色体由两倍体向多倍/非整倍体转变过程中起关键作用,该机制异常将导致基因组不稳定继而诱发肝癌的发生发展。课题组通过对Hippo信号通路重要成员(WW45,Mst1/2,Lats1/2)肝脏特异性敲除和过表达国家自然科学基金委;;国家重点基础研究发展计划(973)项目;;青年千人计划;;中央高校基本科研基金的资

Preparation and properties of wear-resistant carbonized-ceramic composite coating on pure aluminum surface

In this paper, a new composite coating was prepared on the surface of pure aluminum (Al) by combining the micro-arc oxidation (MAO) technology with the polyethylene glycol (PEG 400) carbonization technology. The composite coating and the single MAO coating were observed by scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS), finding that the single MAO coating surface with volcano-like pores and microcracks was covered by the carbonized layer of the composite coating where the overall coating thickness was around 19.5 μm including 17.5 μm of inner MAO coating. The material properties of the composite coating were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The wear resistance of the composite coating was tested under dry friction conditions, finding that the wear width on the composite coating surface was 909.6 μm only, which was around 55.7%, 50.4% and 58.2% of those for pure Al substrate, single carbonized coating and single MAO coating respectively. Then the comprehensive wear resistance of the composite coating was explored under different sliding speeds and lubrication mediums. Finally, the wear-resisting mechanism of the composite coating was discussed, concluding that the composite coating could effectively reduce adhesive wear and abrasive wear of the Al substrate

Heat Transfer Augmentation for the Flow of Highly Viscous Fluids in Tubes Using Cross Trapezoid Wave Tape Inserts

The development and heat transfer augmentation mechanism of a new type cross trapezoid wave tape (CTWT) insert was introduced. Experiments were conducted to evaluate the heat transfer, pressure drop, and fouling characteristics of CTWT inserts for heating of polymer resin and heavy oil, respectively. A 60-120% increase in heat transfer efficiency was achieved, accompanied by a 100% increase in pressure drop over comparable empty tubes. It was also found that CTWT inserts could beneficially reduce the fouling of tubes. Correlations for overall heat transfer coefficient, Nusselt number, and friction factor were derived from the experimental data.Department of Building Services Engineerin

Carbon quantum dots improve the mechanical behavior of polyvinyl alcohol/polyethylene glycol hydrogel

As the wear and tear effects of artificial joints disturb patients after joint replacement, techniques of new lubrication materials or methods are constantly being investigated. Hydrothermal method was adopted to produce carbon quantum dots (CDs), and physically cross-linked polyvinyl alcohol-polyethylene glycol hydrogel (PVA-PEG) to encapsulate CDs, which was evaluated as a lubricant for lubrication appraisal with their slow-release solution. Results of the friction experiment showed that the addition of CDs changed the structure of the gel and promoted the tribological properties of the gel. The structural characterization results show that the CDs are successfully wrapped in gel. The network cross-linked structure of the gel is improved due to the addition of CDs, which are shown by the results of thermogravimetric analysis (TGA) and differential scanning calorimetry analysis (DSC). At the same time, CDs can influence the thermal stability and crystallinity of the gel as well as the degree of cross-linking. These results of TGA and DSC suggest that the curled molecular chain will not be stretched during the gel cross-linking process. After 2 h of self-healing, the recovered gel did not break again under the pull of external force. All these contribute to the preparation and application of hydrogels which is worth looking forward to accelerate the development of polymer lubrication

Tribological behavior of extruded spray-forming 2195-T6 Al-Li alloy at different loads using pin-on-disk tribotester

The tribological properties of Al-Li alloys impact the reliability of components used in different industrial sectors. In this research, the effect of normal load on friction and wear properties of the extruded spray-formed 2195-T6 Al-Li alloy is investigated by using a pin-on-disk tester. Through the microstructure of the friction subsurface, it is evaluated that the friction coefficient of 2195 alloy decreases from 0.408 to 0.306 by increasing load (25 N to 150 N), while the wear rate increases exponentially. It is also analyzed that a mild-severe wear transition occurs between 100 N and 125 N and the main wear mechanism gradually shifts from abrasive wear and oxidative wear to delamination wear (25 N ∼ 100 N), and finally attains the state of severe plastic deformation (125 N ∼ 150 N). Under the action of normal load and friction shearing force, the deformation layer in the subsurface increases from 3 μ m to 43 μ m with increasing load, and the accumulation of strain leads to cracks and holes