A rhodamine-based fluorescent probe selective for bisulfite anion in aqueous ethanol media

A rhodamine-based fluorescent probe with an aldehyde functionality as a binding site was developed for the selective detection of bisulfite anion in aqueous ethanol media. The new fluorescent probe showed an excellent selectivity for bisulfite anion over other anions. The bisulfite-induced ring opening of spirolactam of the rhodamine moiety resulted in the dual chromo- and fluorogenic observation.     

Ratiometric fluorescent sensors for detecting zinc ions in aqueous solution and living cells with two-photon microscopy

We report two fluorescent Zn²⁺ sensors, AD1 and AD2. In aqueous solution, upon addition of Zn²⁺, AD1 only showed the enhancement on the fluorescence intensity, while AD2, acting as a ratiometric sensor, demonstrated the variations not only on the fluorescence intensity but also on the emission wavelengths. Both sensors exhibit high sensitivity (nM level) and selectivity for Zn²⁺ over Na⁺, K⁺, Mg²⁺, and Ca²⁺ at the millimolar level. Moreover, AD2 undergoes significant increase of the TPA cross sections (δ_max) at 840 nm by the Zn²⁺-coordination induced ICT enhancement. The laser scanning confocal microscopy experiments revealed that AD2 is cell-permeable and can indeed visualize the changes of intracellular Zn²⁺ in living cells through a ratiometric approach by utilizing two-photon excitation.     

Ceria-doped SnO2 sensor highly selective to ethanol in humid air

In our earlier study, we reported that at 300 °C, a 2.0 wt.% CeO₂-doped SnO₂ sensor is highly selective to ethanol in the presence of CO and CH₄ gases [F. Pourfayaz, A. Khodadadi, Y. Mortazavi, S.S. Mohajerzadeh, CeO₂ doped SnO₂ sensor selective to ethanol in presence of CO, LPG and CH₄, Sens. Actuators B 108 (2005) 172–176]. In the present investigation, we report the influence of ambient air humidity on the ethanol selective SnO₂ sensor doped with 2.0 wt.% CeO₂. Maximum response to ethanol occurs at 300 °C which decreases with the relative humidity. The relative humidity was changed from 0 to 80% for different ambient air temperatures of 30, 40 and 50 °C and the response of the sensor was monitored in a 250–450 °C temperature range. As the relative humidity in 50 °C air increased from 0 to 30%, a 15% reduction in the maximum response to ethanol was observed. A further increase in the relative humidity no longer reduced the response significantly. The presence of humidity improved the sensor response to both CO and CH₄ up to 350 °C after which the extent of improvement became smaller and at 450 °C was almost diminished. The sensor is shown to be quite selective to ethanol in the presence of humid air containing CO and CH₄. The selectivity passes a maximum at 300 °C; however it declines at higher operating temperatures.     

CHEMAS: Identify suspect nodes in selective forwarding attacks

Selective forwarding attacks may corrupt some mission-critical applications such as military surveillance and forest fire monitoring in wireless sensor networks. In such attacks, most of the time malicious nodes behave like normal nodes but will from time to time selectively drop sensitive packets, such as a packet reporting the movement of the opposing forces, and thereby make it harder to detect their malicious nature. In this paper, we propose CHEMAS (CHEckpoint-based Multi-hop Acknowledgement Scheme), a lightweight security scheme for detecting selective forwarding attacks. Our scheme can randomly select part of intermediate nodes along a forwarding path as checkpoint nodes which are responsible for generating acknowledgements for each packet received. The strategy of random-checkpoint-selection significantly increases the resilience against attacks because it prevents a proportion of the sensor nodes from becoming the targets of attempts to compromise them. In our scheme, each intermediate node in a forwarding path, if it does not receive enough acknowledgements from the downstream checkpoint nodes, has the potential to detect abnormal packet loss and identify suspect nodes. We explore the feasibility of our detection scheme using both theoretical analysis and simulations. The simulation results show that our scheme can achieve a high detection rate, even in harsh radio conditions. The communication overhead incurred by our scheme is also within reasonable bounds.     

CdO activated Sn-doped ZnO for highly sensitive, selective and stable formaldehyde sensor

Sn-, Ni-, Fe- and Al-doped ZnO and pure ZnO are prepared by coprecipitation method, and characterized by scanning electron microscope (SEM), energy diffraction spectra (EDS) and X-ray diffraction (XRD). Their formaldehyde gas sensing properties are evaluated and the results show that 2.2 mol% Sn dopant can increase the response of ZnO by more than 2 folds, while other dopants increase little response or even decrease response. Further, CdO is used to activate ZnO based formaldehyde sensing material. It is demonstrated that 10 mol% CdO activated 2.2 mol% Sn-doped ZnO has the highest formaldehyde gas response, with a linear sensitivity of ∼10/ppm at lowered work temperature of 200 °C than 400 °C of pure ZnO, and high selectivity over toluene, CO and NH₃, as well as good stability tested in 1 month.     

A dual functional near infrared fluorescent probe based on the bodipy fluorophores for selective detection of copper and aluminum ions

A new near infrared (NIR) fluorescent 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye with dual functionality was synthesized and characterized. The compound 1 responds to copper ion in NIR region with high selectivity through a photo-induced electron transfer process established between the substituted benzene group in the meso position and the BODIPY core when Cu²⁺ binds with the four oxygen atoms in the structure, and results in the quenching of the fluorescence. The response range to copper ions was from 10 to 50 μM, and other metal ions including Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Pb²⁺, Fe³⁺, Ag⁺, Hg²⁺, Co²⁺, Zn²⁺, Mn²⁺, Cd²⁺, Ni²⁺ and Al³⁺ had no interference. When excited at 520 nm, a new emission peak at 568 nm of compound 1 was used to detect Al³⁺ selectively from 30 μM to 110 μM without any interference from other metal ions including copper ions.     

新的传感器网络假冒攻击源检测方案

针对传感器网络假冒攻击,提出了一种新的假冒攻击源检测方案。新方案利用基于身份的签名技术,结合节点报警规则,构造了基于邻居节点相互认证的单个试图假冒攻击源测定算法,以此为基础,扩充为针对局部区域内的多个试图假冒攻击源测定算法。新方案也提出了成功假冒攻击源测定算法,其中采用了汇聚节点监控排查恶意区域、普通节点认证转发报警消息机制。新方案适用于假冒攻击状况复杂、网络安全性要求较高的环境。仿真实验证实了新方案在成功检测方面的有效性。     

Performance study of selective encryption in comparison to full encryption for still visual images

Securing digital images is becoming an important concern in today＇s information security due to the extensive use of secure images that are either transmitted over a network or stored on disks. Image encryption is the most effective way to fulfil confidentiality and protect the privacy of images. Nevertheless, owing to the large size and complex structure of digital images, the computational overhead and processing time needed to carry out full image encryption prove to be limiting factors that inhibit it of being used more heavily in real time. To solve this problem, many recent studies use the selective encryption approach to encrypt significant parts of images with a hope to reduce the eneryption overhead. However, it is necessary to realistically evaluate its performance compared to full encryption. In this paper, we study the performance and efficiency of image segmentation methods used in the selective encryption approach, such as edges and face detection methods, in determining the most important parts of visual images. Experiments were performed to analyse the computational results obtained by selective image encryption compared to full image encryption using symmetric encryption algorithms. Experiment results have proven that the selective encryption approach based on edge and face detection can significantly reduce the time of encrypting still visual images as compared to full encryption. Thus, this approach can be considered a good alternative in the implementation of real-time applications that require adequate security levels.     

Novel sensor scheduling and energy-efficient quantization for tracking target in wireless sensor networks

This paper focuses on sensor scheduling and information quantization issues for target tracking in wireless sensor networks (WSNs). To reduce the energy consumption of WSNs, it is essential and effective to select the next tasking sensor and quantize the WSNs data. In existing works, sensor scheduling’ goals include maximizing tracking accuracy and minimizing energy cost. In this paper, the integration of sensor scheduling and quantization technology is used to balance the tradeoff between tracking accuracy and energy consumption. The main characteristic of the proposed schemes includes a novel filtering process of scheduling scheme, and a compressed quantized algorithm for extended Kalman filter (EKF). To make the algorithms more efficient, the proposed platform employs a method of decreasing the threshold of sampling intervals to reduce the execution time of all operations. A real tracking system platform for testing the novel sensor scheduling and the quantization scheme is developed. Energy consumption and tracking accuracy of the platform under different schemes are compared finally.     

一种新颖的传感器网络聚类路由协议

提出了一种能量有效的基于聚类的传感器网络路由协议—EEHCA（an Energy-Efficient Hierarchical Clustering Algorithm for wireless sensor networks）。该协议通过最小化通信能量消耗并在所有节点之间实现能量消耗负载平衡的方式,达到了延长传感器网络生存时间的目的。协议提出了一种新颖的簇首确定机制,该机制可以避免感知区域内的节点进行频繁的簇首选举,从而节约了能量。为提高传感器网络的容错性能,引入了备用簇首的概念。在簇首与基站通信方面,采用多跳传输的方式进行,从而避免了距离基站较远的簇首进行长距离通信时所造成的能量过早耗尽的问题。仿真结果表明提出的协议拥有比LEACH和HEED协议更长的网络生存时间。     

无线传感网络中抵抗节点复制攻击新方法

针对伏飞等人提出的LTB（Location and Time Binding）方法的不足：不能完全阻止复制节点加入传感网络;不能阻止新加入节点和复制节点建立共享密钥,提出了一个在传感网络中抵抗节点复制攻击的新方法,该方法通过把传感网络划分成一系列有效区域并把节点的密钥与身份标识和部署位置绑定起来,在共享密钥建立时阻止部署在有效区域外的复制节点建立共享密钥,在复制节点通信时检测出有效区域内的复制节点。该方案能有效地解决LTB带来的安全隐患且和LTB具有相近的通信、存储开销。     

一种基于IBE的WSNs选择转发攻击检测方案

无线传感器网络因节点能力的限制,通常采用多跳的方式进行节点间消息的互发,这种多跳路由协议为选择转发攻击提供了便利。基于此,提出一种基于随机检查点的多跳确认方案来检测无线传感器网络中的选择转发攻击,将IBE加密及LEACH路由协议引入其中,用以对选择转发攻击的检测方法加以改进。给出检测防御方案的总体框架,对其工作方式进行了具体描述。在NS2环境下,从检测点数目、计算速度与能耗、存储要求及健壮性等几方面对改进方案进行了仿真,以验证其对无线传感器网络安全性的提高。     

Three-input chemical logic circuits based on a new fluorescent sensor for ATP and Cuin aqueous solution

A new l-lysine derivative featuring an anthracene unit is synthesized and characterized by elemental analysis, ESI-MS, ¹H-NMR, and ¹³C-NMR. It can selectively bind ATP in acidic aqueous solutions, and be used as a highly selective fluorescent chemosensor for Cu²⁺ at neutral pH, resulting in fluorescence quenching. According to these characters, two combinational logic circuits are fabricated on a single molecule with three chemical inputs [H⁺(IN1), OH⁻(IN2), ATP (IN31)] and [H⁺(IN1), OH⁻(IN2), Cu²⁺(IN32)], respectively.     

基于信息覆盖理论的传感器节点部署方法

传感器网络中,覆盖控制是一个基本的问题.传感器节点既可以随机部署也可以在特定的环境中指定部署.传感器部署在传感区域网格的顶点处,如果信息能够覆盖网格中所有的顶点,此传感器网络为完全信息覆盖.通过研究基于完全信息覆盖理论的传感器节点指定部署,把传感器部署问题转化为受限的优化问题,并提出了一种贪婪算法,目的是在保证覆盖要求的条件下总代价的最小化.计算结果显示该算法不仅能有效的求得高质量的解决方案,而且还能在满足信息覆盖的要求的同时,极大地减少所需传感器的数量.     

面向交通信息采集的智能无线传感器节点

为了准确实时获取交通信息参量,利用无线传感器网络技术作为智能交通感知前端和通信手段,融合GPRS技术,构建交通信息采集网,为道路交通信息采集提供了更加便捷的解决方案。设计了交通信息采集的传感器节点,提出了动态车辆探测算法和车速测量算法。实测结果表明:动态车辆探测算法和车速测量算法能够在计算能力有限的传感器节点上实现,能准确实时地获得车流量、车速等交通参量;该交通信息采集系统能满足网络大规模部署的需求,可应用于智能交通系统。     

用于板结构损伤检测的磁致伸缩传感器

基于铁磁性材料的磁致伸缩特性,提出一种用于非铁磁性板结构损伤检测的磁致伸缩传感器。该传感器分为激励和接收两部分,由8字型线圈、镍带以及偏置永磁铁组成。根据磁致伸缩效应,激励部分在板中激励导波,波在板中传播,遇缺陷及边缘反射,通过磁致伸缩逆效应,由接收部分接收其反射信号。根据反射信号的到达时间和波在板中传播的速度,可判断出板中缺陷所在位置。改变恒定偏置磁场与时变磁场的方向可以在板中激励不同波型的导波。实验结果证明:该传感器设计是可行的,且具有价格便宜、灵敏度高、可与被测结构分离等优点。     

一种新型无线传感器网络节能覆盖方案

针对一种实际地理环境下的生态监测问题,把拓扑控制中的功率控制思想引入到节能覆盖的研究中,建立感知半径之和最小的数学模型,并用遗传算法求解该模型,得到最优覆盖解。最后,对该方案进行能耗分析和仿真实验,结果表明该算法不仅节能,而且可以获得较高覆盖率,降低信道通讯干扰并提高网络的抗毁性。     

The use of the substituted imidazoline radical as a receptor for sulphur dioxide gas sensor

Computer simulation of different structures of adsorption complexes formed by gas adsorption on organic layers with various functional groups was carried out. On the basis of simulation results, we chose 2-(4′-dimethylaminophenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl as a substance possessing high selectivity toward SO₂. Simulation results were confirmed experimentally in the studies of adsorption by means of ellipsometry and quartz microbalance.     

无线磁阻传感器网络停车检测技术研究

随着机动车保有量的高速增长,停车混乱问题日益严重,各大中城市对停车实时监控及管理有迫切的建设需求。为了构建基于无线传感器网络的大规模、低成本、低功耗的停车管理系统,本文基于磁场干扰车辆检测原理,提出了一种停车检测算法,实际应用表明该算法车辆检测精度高,达到了设计要求。     

A destination-based approach for cut detection in wireless sensor networks

Wireless sensor networks often suffer from disrupted connectivity caused by its numerous aspects such as limited battery power of a node and unattended operation vulnerable to hostile tampering. The disruption of connectivity, often referred to as network cut, leads to ill-informed routing decisions, data loss and waste of energy. A number of protocols have been proposed to efficiently detect network cuts; they focus solely on a cut that disconnects nodes from the base station. However, a cut detection scheme is truly useful when a cut is defined with respect to multiple destinations (i.e. target nodes), rather than a single base station. Thus, we extend the existing notion of cut detection, and propose an algorithm that enables sensor nodes to autonomously monitor the connectivity to multiple target nodes. We introduce a novel reactive cut detection solution, the point-to-point cut detection, where given any pair of source and destination, a source is able to locally determine whether the destination is reachable or not. Furthermore, we propose a lightweight proactive cut detection algorithm specifically designed for a network scenario with a small set of target destinations. We prove the effectiveness of the proposed algorithms through extensive simulations; specifically, in our network configurations, proposed cut detection algorithms achieve more than an order of magnitude improvement in energy consumption, when coupled with an underlying routing protocol.