Interference Cancellation for High-Frequency Surface Wave Radar

The performance of high-frequency surface wave radar (HFSWR) is known to suffer from external environmental interference and noise, such as cochannel radio-frequency interference from other radiating source, ionospheric clutter, lightning impulsive noise, etc. This paper experimentally evaluates the interference cancellation performance of various adaptive beamforming schemes with respect to the aforementioned three types of interferences in an attempt to find the most promising adaptive cancellation scheme in practical HFSWR environment.     

Electromagnetic dyadic Green's functions for multilayeredspheroidal structures. I: formulation

Dyadic Green's functions (DGFs) and their scattering coefficients are formulated in this paper for defining the electromagnetic fields in multilayered spheroidal structures. The principle of scattering superposition is applied, in a similar form of the DGF in an unbounded medium under spheroidal coordinates, the scattering DGFs due to multiple spheroidal interfaces are expanded in terms of the spheroidal vector wave functions. For the lack of general orthogonality of the spheroidal radial and angular functions, the Green's dyadics are expressed in a different way where the coordinate unit vectors are also combined in the construction, as compared with the conventional form of vector wave eigenfunction expansion. The matrix equation systems satisfied by the coupled scattering (i.e., reflection and transmission) coefficients of the DGFs are obtained so that these coefficients can be solved uniquely. The DGFs can be employed to investigate effects of spheroidal radomes used to protect the airborne or satellite antenna systems and of handy phone radiation near the spheroid-shaped human head, and so forth. Numerical calculations about the applications of the formulated multilayered DGFs are presented in part II of this paper     

A new signal processing technique for ISAR ranging: the Vernierranging method

A new technique for inversed synthetic aperture radar (ISAR) ranging, which resembles the principle of the Vernier measuring system, is presented. In this technique, the transmitted ISAR pulse comprises a train of chirp subpulses with uniformly stepped up center frequencies. The return ISAR echo is first processed, using hardware, to determine a coarse estimate of the target range. Further refinements of the range estimate are achieved through software processing, consisting of two stages of discrete Fourier transform operation. The ranging accuracy can be increased without the need for increased bandwidth, but at the expense of a slight increase in computational complexity. Numerical evaluation shows that a noiseless system is capable of achieving high-ranging accuracy, of the order of millimeters, even in the presence of dispersion and target motion. From computer simulations, the proposed system is also found to be robust against additive system noise and frequency jitter under practical conditions     

LPG-Based PVA Coated Sensor for Relative Humidity Measurement

A long period grating (LPG) coated with polyvinyl alcohol has been developed and evaluated through exposure to a range of relative humidity (RH) levels (from 33%RH to 97%RH). The conditions for the creation of the sensor probes are described and the response of the device in terms of changes in the resonance loss of several of the spectral loss bands has been monitored. In order to make comparative measurements, a noncoated LPG was exposed to various known refractive index (RI) conditions and the grating response was monitored, analyzed and the results evaluated. This is then related to the change in RH when the sensor is exposed to various RH levels, as the coating RI changes, leading to the change in resonance loss. The PVA coated LPG sensor is showing a relatively fast response time of ~ 80 s to reach 97%RH from 33%RH and inducing ~ 2 dB change in transmission of resonance loss band.     

Prediction of the melt flow index using partial least squares and support vector regression in high-density polyethylene (HDPE) process

In polyolefin processes the melt flow index (MFI) is the most important control variable indicating product quality. Because of the difficulty in the on-line measurement of MFI, a large number of MFI estimation and correlation methods have been proposed. In this work, mechanical predicting methods such as partial least squares (PLS) method and support vector regression (SVR) method are employed in contrast to conventional dynamic prediction schemes. Results of predictions are compared with other prediction results obtained from various dynamic prediction schemes to evaluate predicting performance. Hourly MFIs are predicted and compared with operation data for the high density polyethylene process involving frequent grade changes. We can see that PLS and SVR exhibit excellent predicting performance even for severe operating situations accompanying frequent grade changes.     

Dynamic Transmission Scheduling for Streaming Applications via P2P Overlay

In current Peer-to-Peer streaming applications, a lot of research attempts to provide timely stream services to the end users. Most of them focus on how to organize the peer connections into an efficient overlay network. Due to the variation in the network, a lot of overhead is generated when the overlay structure adapts to the changes. In order to minimize the impact of network fluctuation, we proposed a scheduling algorithm which helps to distribute stream data efficiently through the fluctuating networks. It needs only partial information about overlay structure and provides the services to satisfy most number of users. The global latency experienced by peers in the system is thus minimized. To alleviate the problem of packet loss along the overlay, we introduce retransmission requests into our scheduling algorithm. Requests for much needed data are treated with higher priority. Parent peers which receive the request will re-send the missing data to minimize the loss impact. The missing data which are needed by more peers will have a larger cumulative impact through the tree overlay and these are thus scheduled and sent earlier. Simulation results showed that our prioritization and scheduling algorithm minimizes the negative impact of fluctuation and data loss in a dynamic network environment.     

Antioxidant activities of phlorotannins purified from Ecklonia cava on free radical scavenging using ESR and H2O2-mediated DNA damage

The potential antioxidant activities of three phlorotannins (phloroglucinol, eckol and dieckol) purified from Ecklonia cava collected in Jeju Island were investigated to evaluate their potential value as the natural products for foods or cosmetic application. In this study, antioxidant activities were measured by electron spin resonance spectrometry (ESR) technique for scavenging effects of free radicals such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), alkyl, hydroxyl (HO^•) and superoxide anion radical (O₂ ^•−) and by comet assay for protecting effects against H₂O₂-mediated DNA damage. The results show that all the phlorotannins have the potential DPPH, alkyl, hydroxyl and superoxide radical scavenging activities. Especially, eckol samples scavenged around 93% of DPPH at 0.25, 0.5, 1 mg/mL of concentrations and were higher than the other phlorotannins, such as phloroglucinol and dieckol samples. Also, protecting effects of the phlorotannins against H₂O₂-mediated DNA damage increased with increased concentrations of the samples in the L5178 mouse T-cell lymphoma cell lines (L5178Y-R). In conclusion, these results suggest that the three phlorotannins purified from E. cava have the potential inhibitory effect on H₂O₂-mediated DNA damage and harmful free radicals and can be used as antioxidants in cosmetic, foods and drug industry.     

Performance evaluation with DEVS formalism and implementation of active emergency call system for realtime location and monitoring

In this paper, we designed and implemented the active emergency call system for emergency call service actively. Active emergency call system has two physical components; E-Device (Emergency Mobile Device) and E-Server (Emergency Server). The role of E-Device is the mobile device in order to call emergency by using mild handicapped, the elderly and children who are able to communicate their intention to another. E-Server is the server for management E-Devices with realtime monitoring. E-Device will be developed to the portable size for easily mild handicapped, the elderly and children. When they need the service of emergency call, the button of E-Device can be used and the call signal is transmitted to the emergency office and the guardian through Internet and CDMA. E-Server should be developed the integrated control system for management of E-Devices basically. And it also supported to realtime monitoring of E-Devices with respect to high quality of emergency call service for rise the efficiency. And finally we describe the results of performance evaluation about the location error of E-Device between coordinate of GPS received signal and actual E-Device coordinate, when it has been called emergency, by using DEVS (Discrete Event System Specification) formalism.     

Distributed Court System for intrusion detection in mobile ad hoc networks

Securing routing layer functions in mobile ad hoc networks is an important issue, which includes many challenges like how to enhance detection accuracy when facing the highly dynamic characteristic of such networks, and how to distinguish malicious accusations under a totally autonomous structure. In this paper, we propose Distributed Court System (DCS), a complete Intrusion Detection System that intends to solve these challenges in a low-cost and robust way. We do not deploy any centralized entity, but rely on the collaboration among the nodes neighbouring the suspected node, to integrate information, improve the detection accuracy, and reject dissemination of malicious accusation. Through mathematical analysis and simulation, the proposed DCS is proved to be effective in a highly mobile and hostile network environment.