On channel adaptive energy management in wireless sensor networks

Energy constraints in a wireless sensor network are crucial issues critically affecting the network lifetime and connectivity. To realize true energy saving in a wireless environment,the time varying property of the wireless channel should also be taken into account. Unfortunately, this factor has long been ignored in most existing state-of-the-art energy saving protocols. Neglecting the effects of varying channel quality can lead to an unnecessary waste of precious battery resources, and, in turn, can resultin the rapid depletion of sensor energy and partitioning of the network. In this paper, we propose a channel adaptiveenergy managementprotocol, called CAEM, that can exploit this time varying nature of the wireless link. Specifically, CAEM leverages on the synergistically cross-layer interaction between physical and MAC layers. Thus, each sensor node can intelligently access the wireless medium according to the current wireless link quality and the predicted traffic load, to realize an efficient utilization of the energy. Extensivesimulation results indicate that CAEM can achieve as much as 40% reductionin energy dissipation compared with traditional protocols without channel adaptation. © 2005 IEEE.published_or_final_versio

A multipath ad hoc routing approach to combat wireless link insecurity

As wireless LAN (WLAN) technologies proliferate, it is becoming common that ad hoc networks, in which mobile devices communicate via temporary links, are built using WLAN products. In the IEEE 802.11b standard, the Wired Equivalent Privacy (WEP) scheme is used as the only measure to enhance data confidentiality against eavesdropping. However, owing to the well known pitfalls in Initialization Vector (IV) attachment in the ciphertext, the underlying 40-bit RC4 encryption mechanism in WEP is unsafe regardless of the key size. On the other hand, solutions involving replacement of RC4 by another cipher are not attractive because that may lead to reconstruction of the whole system and result in high costs as well as redevelopment of the products. In order to enhance the security on the existing development efforts, we propose a novel multipath routing approach to combat the link insecurity problem at a higher protocol layer. This approach does not require the application to use sophisticated encryption technologies that may be too heavy burdens for mobile devices. Based on our suggested confidentiality measurement model, we find that our proposed multipath ad hoc routing technique, called Secure Multipath Source Routing (SMSR), is highly effective.published_or_final_versio

A quantitative comparison of ad hoc routing protocols with and without channel adaptation

To efficiently support tetherless applications in ad hoc wireless mobile computing networks, a judicious ad hoc routing protocol is needed. Much research has been done on designing ad hoc routing protocols and some well-known protocols are also being implemented in practical situations. However, one major imperfection in existing protocols is that the time-varying nature of the wireless channels among the mobile terminals is ignored, let alone exploited. This could be a severe design drawback because the varying channel quality can lead to very poor overall route quality in turn, resulting in low data throughput. Indeed, better performance could be achieved if a routing protocol dynamically changes the routes according to the channel conditions. In this paper, we first propose two channel adaptive routing protocols which work by using an adaptive channel coding and modulation scheme that allows a mobile terminal to dynamically adjust the data throughput via changing the amount of error protection incorporated. We then present a qualitative and quantitative comparison of the two classes of ad hoc routing protocols. Extensive simulation results indicate that channel adaptive ad hoc routing protocols are more efficient in that shorter delays and higher rates are achieved, at the expense of a higher overhead in route set-up and maintenance. © 2005 IEEE.published_or_final_versio

阿爾泰哈巴河群的沉積時代及其構造背景

Habahe Group mainly consists of elastic sediments, which widely distribute in the Chinese Altai and can provide important constraints on the tectonic evolution of the Central Asian Orogenic Belt (CAOB). However, there are different opinions about its deposition time and tectonic background. Previous studies suggested that the Habahe Group formed in Sinian to Mid-Ordovician or Mid- to Late Ordovician in a passive continental margin. On the other hand, recent geological investigations reveal a long lasting subduction-related setting in the Chinese Altai at least since Cambrian. The current geochronological study for detrital zircons from the Habahe Group reveals that the detrital zircons of individual samples, irrespective of their lithological and metamorphic differences, all show similar age patterns, with the early Paleozoic ( 206Pb/ 238U age = 463 ± 542Ma) grains predominating. The youngest detrital zircons from different samples display similar ages (ca. 470Ma), which may reflect the maximum deposition time of the Habahe Group. Dating of growth rim of detrital zircons from migmatite yielded a Mid-Devonian age (384 ± 6Ma), which was coeval with intrusion of Early to Mid-Devonian granitic plutons in the area and clearly indicates the minimum deposition time of the Hababe Group. Therefore, the deposition time of the Habahe Group can be constrained to be Mid-Ordovician to Early Devonian. Zircon U Pb dating results indicate that the detrital zircons of the Habahe Group are dominated by early Paleozoic grains, with small proportion formed in Precambrian. The early Paleozoic detrital zircons are mostly magmatic in origin, and their less rounded shapes indicate a limited transportation. The age and morphological characteristics of the detrital zircons are consistent with those of detrital zircons in active tectonic settings and indicate that the Chinese Altai was under an active continental margin environment during the Early Paleozoic. 北疆阿爾泰造山帶的哈巴河群變質碎屑巖分布廣泛,其沉積時代和構造環境對于認識中亞造山帶的演化歷史有重要意義。早期研究認為哈巴河群沉積于震旦紀—中奧陶世時期,形成于被動大陸邊緣構造環境。而最近有學者根據中亞造山帶的地質演化背景提出,阿爾泰形成于活動陸緣構造環境。對哈巴河群中碎屑鋯石的年代學研究表明,不同巖性或變質程度不同的樣品碎屑鋯石主要類群具有相似的年齡分布特征,其206Pb/238U 年齡主要介于463～542Ma 之間。在這些樣品中, 最年輕的碎屑鋯石年齡均集中于470Ma 左右,代表了碎屑沉積的時代下限。而哈巴河群混合巖樣品中碎屑鋯石增生邊形成于中泥盆世晚期（384±6Ma）,與侵入該群的早古生代花崗巖的年齡十分接近,大致反映了哈巴河群碎屑巖沉積時代的上限,因此哈巴河群的沉積時代應在早泥盆世—中奧陶世之間。鋯石的形態和內部結構特征顯示哈巴河群的年輕碎屑鋯石類群（463～542Ma）主要為巖漿鋯石,其磨圓度較差,而且在比例上遠高于前寒武紀碎屑鋯石。上述特點與活動大陸邊緣碎屑鋯石類群分布特征完全一致,反映阿爾泰在中奧陶世至早泥盆世可能處于活動大陸邊緣構造環境。postprin

The curvature match of the tool and surface in the non-vertical coordinate system

2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Overexpression of protein kinase C-beta 1 isoenzyme suppresses SC-236-induced apoptosis in gastric epithelial cells

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