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Diatoms are currently being used in different fields, and their application as bioindicators is one of their main benefits. Their identification is carried out by specialists, the main difficulty being the wide variety of existing species and the great similarity between some of them. In recent years attempts have been made to create an automatic identification system with the collaboration of experts in areas of pattern recognition. In this research we analyzed the use of binary masks of rings in images as a method to automatically identify diatoms, or render an approximative identification. Among the advantages of the proposed method is its invariance regarding the different positions in which the diatoms can be found. Invariance to illumination changes is achieved by means of different transforms, such as the power law transform. The image databases used to develop the algorithms were diatom images taken from samples collected at springs in Lake Patzcuaro, Michoacan, Mexico, at the San Lazaro basin, Baja California Sur, Mexico and from the public image database of ADIAC. In morphological and textural descriptors, the background of the image must be eliminated in order to classify the diatoms, whereas in the proposed methodology this is not necessary. The obtained results reach over than 90% even when the diatoms in the images are broken.

The use of UAVs or drones for criminal or terrorist enterprises is an increasing problem. Many countermeasures have been proposed to prevent, deter, detect and/or mitigate the dangers posed by such malicious UAVs. One such countermeasure is to track or pursue a malicious UAV back to its point of origin using one or more surveillance UAVs in order to apprehend the UAV and possibly its owner. If the malicious UAV has a higher capability set than the surveillance UAVs, it will be able to outrun any one of them, and therefore the tracking responsibility must be distributed over a swarm of surveillance UAVs that are geographically dispersed across the tracking area of interest. One aspect of particular interest is how the initial formation of the swarm of surveillance UAVs impacts its ability to successfully track a malicious UAV. In this paper, we examine a specific circular initial swarm formation comprising uniformly spaced concentric rings of uniformly spaced UAVs. The total number of surveillance UAVs follows the sequence of centred hexagonal numbers as the number of rings increases. The tracking performance of this circular swarm of surveillance UAVs is compared to a reference swarm of the same size in which the initial locations of the UAVs are randomly chosen. Two tracking strategies are considered: 1) Reactive tracking, in which each surveillance UAV acts independently of the others and only pursues the malicious UAV when it itself detects it, and 2) Reactive tracking with predictive pre-positioning, in which once one surveillance UAV detects the malicious UAV, it communicates the estimated trajectory and speed of the malicious UAV to all swarm members so they can predictively move to a more optimum tracking position before the malicious UAV arrives. The results demonstrate that this particular circular swarm of surveillance UAVs has superior tracking performance relative to the reference randomly positioned swarm of the same size; this is true for both tracking strategies, but particularly when predictive pre-positioning is employed with a relatively small number of surveillance UAVs.

A diode-pumped Yb:CALGO laser with intracavity conical refraction (CR) was demonstrated. The laser produced an excellent quality CR beam where the bright concentric rings are distinguishable and separated by a Poggendorff dark ring. The maximum output power obtained in the CR laser beam was >6W.

This paper presents closed form exact analytical expression of directivity for arbitrary planar array antennas. The expression is used to study and compare the directive characteristics of dense arrays and sparse arrays. The study encompasses two popular array arrangements, viz, square and concentric ring arrays. As an outcome of the study superiority of sparse arrays over dense arrays in terms of wide scanning performance is established.

In this paper, the impact of complimentary split ring resonator (CSRR) incorporation in lowering resonant frequency of X-band substrate integrated waveguide (SIW) antenna is investigated. Two concentric ring slots of CSRR are incorporated into the radiator of X-band SIW antenna which is constructed by an extended half-circle shape and fed using a microstrip line. A 1.6mm thick FR4 epoxy dielectric substrate with the dimension of 36mm by 22mm is used to deploy the proposed antenna. In order to shows the potency of resonant frequency lowering by incorporating CSRR structure, the conventional antenna, i.e. an X-band SIW antenna without CSRR, is also designed using the same dielectric substrate. The characterization result shows that the proposed X-band SIW antenna could resonate at the frequency of 12% lower than the conventional antenna without any significant changes in other radiation characteristics.

In this paper, we report our study on using a piezoelectric membrane to measure the contraction profile of Human iPSC cardiomyocytes. To guide HiPSC cardiomyocytes aligned concentrically with respect to the circular-shape piezoelectric membrane, 20 μm polydimethylsiloxane micro-grooves with 20 μm separation are molded on top of the piezoelectric membrane to form multiple concentric rings. Gelatin or fibronectin is coated on the microgrooves for promoting cell adhesions. Using this method, repeated contractions can be measured by using the circular piezoelectric membrane, and the contraction profile can be monitored. To study the performance of the piezoelectric membrane, different dosage of commercial drugs are used, including Isoproterenol and Metoprolol. Experimental results demonstrated that the piezoelectric membrane can measure the contraction profile of cardiomyocytes. Cellular responses to different drugs and dosage can be monitored electrically.

In this paper, an experimental study is performed to realize the electromagnetic properties permittivity (e r ) and permeability (µ r ), of a solar panel substrate with SRR inclusions.The proposed study is conducted for the modern wireless communication applications. The solar panel structure is based on a flexible layer of PTFE. The SRR structure is constructed from two concentric rings of three periodical unit cells in their lattice. The substrate layer, based solar panel, properties are measured using a modified Nicholson-Ross-Weir formulations (NRW) to retrieve e r =e r '+je r " and µ r =µ r '+jµ r " from the measured S-parameters. The Finite Integral Technique (FIT) simulations based on CST MWS software package formulations is invoked to evaluate the S-parameters based on the retrieved e r , µ r and compare them to their relative measurements. Next, a PTFE sample is used to validate the proposed technique. It is found that the properties of the PTFE sample are quite relative to those published in the literature where e r =2.07+j0.001 and µ r =0.999+j0.0001. Finally, an excellent matching is realized between the measured and simulated results.

A recently developed tripolar concentric ring electrode enables accurate estimation of the local Laplacian of the electroencephalogram (EEG). Here, we tested the ability of this tripolar EEG (tEEG) system to detect the extent to which the alpha rhythm—an 8-13 Hz oscillation found in the EEG when the subject is at rest with the eyes closed—is modulated by opening the eyes, and compared it with simultaneous conventional EEG measurements. In a preliminary study comprising ten independent sessions on seven subjects, opening the eyes reduced alpha power by an average of 66.5 ± 9% and 59.1 ± 10% in tEEG and conventional EEG recordings, respectively. These findings suggest that the dynamical changes in brain rhythms may be more easily detected by tEEG than by conventional EEG with implications for clinical diagnosis and neurofeedback applications.

Interconnection Network Topology plays a very important role in style of distributed systems. As a result of performance of load balancing/task allocations techniques is depends on performance of network. Therefore before discussing optimized task allocation/load equalization theme there’s a requirement of investigate the interconnection topology. Range of interconnection networks is offered in literature like hypercube, mesh, star, tree, de Bruijn and etc. networks. therefore we’ve got planned another constant degree, scalable straightforward routing networks named as concentric rings (m) in this paper, during which rings can be increased as per demand and our results shows that the overheads at significant load will to decreases conjointly.

This paper deals with the performance analysis of bandpass filter (BPF) composed of substrate integrated waveguide (SIW) and the influence of number of complimentary split ring resonators (CSRRs) incorporated into the filter. The performance analysis is emphasized on how the number of CSRRs incorporation affects to the parameters of filter, namely bandwidth, insertion loss, and return loss. The analysis is applied for the BPF without CSRRs as well as with the number of CSRRs incorporation. The SIW BPF is designed on an FR4 epoxy dielectric substrate with the thickness of 1.6mm and the relative permittivity of 4.3. Meanwhile, each CSRR comprises of 2 concentric rings with the ring width of 2mm and the diameter of 12mm and 7mm for the outer and inner ring, respectively. From the analysis, it shows that the number of CSRRs incorporation into SIW BPF contributes to the number of frequency bands in the passband area. However, the bandwidth of additional band is narrow for the increase number of CSRRs incorporation.

In this paper we present a concentric, multiple resonant elements realization of a distributed filter. The proposed filter has 3 poles and is designed to operate at a frequency of 1.8 GHz with an absolute bandwidth of 40 MHz, equivalent to 2.22 %. Each resonant chamber of the presented filter consists of 25 individual resonant elements arranged in an interdigitated fashion along the circumference of three concentric rings. The resonator occupies a volume of 40 × 40 × 5 mm3 and has an unloaded quality factor of over 1800. The internal height of the filter (5 mm or 10.8°) is lowest reported in the literature. The measurements of the filter are in an excellent agreement with simulations — the measured insertion loss is 0.44 dB, while the theoretically predicted value stands at 0.37 dB.

Tripolar concentric ring electrode (TCRE) sensors have unique properties. These sensors have been used to acquire various bio-signals such as: electroencephalography (EEG), electrocardiography (ECG), and electromyography (EMG). Compared to conventional disc electrode signals TCRE EEG (tEEG) has four times better signal-to-noise ratio, eleven times better mutual information and spatial resolution. Since the electrodes of the TCRE sensor are a millimeter apart, signals arising from distant sources produce nearly the same potential on each electrode. Therefore, when the difference of the signals is taken between the electrodes the common signal is cancelled. We have found significant improvements in real-time brain computer interfacing with tEEG compared to EEG. We have also found that we can see higher-frequency signals with tEEG, up to 425 Hz so far, compared to EEG.

Microsaccades are tiny, involuntary eye movements that occur during fixation, and they are necessary to human sight to maintain a sharp image and correct the effects of other fixational movements. Researchers have theorized and studied the effects of microsaccades on electroencephalography (EEG) signals to understand and eliminate the unwanted artifacts from EEG. The tripolar concentric ring electrode (TCRE) sensors are used to acquire TCRE EEG (tEEG). The tEEG detects extremely focal signals from directly below the TCRE sensor. We have noticed a slow wave frequency found in some tEEG recordings. Therefore, we conducted the current work to determine if there was a correlation between the slow wave in the tEEG and the microsaccades. This was done by analyzing the coherence of the frequency spectrums of both tEEG and eye movement in recordings where microsaccades are present. Our preliminary findings show that there is a correlation between the two.

In this paper, bow-tie antenna with defected ground structure (DGS) has presented. The radiating element is bow-tie antenna, two concentric ring slots are presented on it for producing the circular polarization (CP). Rectangular patch is loaded to bow-tie antenna for enhance the gain. On the ground plane four equal bow-tie slots are considered for enhancing the impedance bandwidth upto 10.3%. It is operated at 14.5 GHz frequency. The gain is 5.9 dB. The good agreement between the simulated and measured values is observed. These results are very useful for airborne and radar applications.

The technique of using randomly rotated circularly polarized microstrip antennas as the elements of concentric ring array (CRA) for radar cross section (RCS) reduction is presented in this paper. The main concept of the technique is that a rotated microstrip antenna can provide additional phase shift for the reflected wave. When all elements are rotated randomly, the diffuse, instead of the cophasal, scattered fields can be achieved. Three types of concentric arrays are compared by full wave simulations. Results indicate that the RCS of the randomly rotated array can be reduced significantly, even in the main beam region.

Sparse concentric ring arrays composed of aperiodic rings with elements equally spaced in each ring are capable of achieving circularly symmetric patterns with low sidelobe level (SLL) compared with the thinning concentric ring arrays. Here teaching learning based optimization (TLBO) algorithm which is based on stochastic optimization is first applied to synthesizing sparse concentric ring arrays. TLBO is adopted to optimize the non-uniform ring radii considering the constraints on the aperture and the minimum inter-ring spacing so as to achieve circularly symmetric pattern with both the SLL and the number of elements reduced. Numerical experiments are presented to demonstrate the performance and the potential applications of the proposed method.

in this paper, we have urbanized a fresh sink placement policy in Wireless Sensor Networks (WSNs). We studied the problems in previous sink placement strategies such as RSP, CNP, GOSP, SOSP, CLHM, ISP, and GSP. These previous sink placement strategies are not concerned about dynamicity of the network under consideration. The information about sensor nodes positions is not known beforehand in concerned WSN environment. On the reverse, GSP policy is designed particularly for unidentified feeler nodes site and is proposed as a standard sink placement policy in WSNs. So, GSP has been chosen to compare our strategy that reduces both energy consumption as well as routing overheads. We are proposing the new and improved strategies which work on concentric ring routing principle with and without density. In with density, a new random protocol used, in which the location of sinks are placed according to the density of the nodes and in the new uniform protocol they are fixed.

Latency-sensitive multiparty applications involve intensive communication between multiple participating nodes. Relays are usually adopted for matchmaking end hosts, filtering unwanted traffics, bypassing routing outages and so on. Speeding up the relay-communication becomes increasingly important to improve the QoE of clients. Currently, no rigorous guarantees have been made for the latency-optimal relay communication. We propose a novel framework to truthfully represent the relay communication in the latency space. Real-world data sets show that nearly 90% of node triples obey the average triangle inequality, while our new model allows for the asymmetry and triangle inequality violations to occur. We propose the general triangle to rigorously locate a candidate relay closer to multiple nodes, with which we systematically analyze the feasibility of finding an optimal relay node for arbitrarily sized groups. Our results show that distributed greedy methods are able to locate optimal relays with modest communication overhead and small search hops.

In this study, the effects of the radii of the concentric rings and the substrate material on the spectral characteristics of the two concentric ring slot frequency selective surface structure are investigated by means of a finite integration technique and finite element technique based simulators. For the investigated dual band frequency selective surface structure, it has been demonstrated that the radius of the circular metallic patch and the inner ring slot affect only the resonance characteristics of the second stop band. However, the outer radius of the outer ring slot affects only the resonance characteristics of the first stop band. Tailoring the radius of the center metallic patch is found to be more useful for making fine adjustments in the spectral position of the second resonance band. The resonance frequencies of the stop bands can also be decreased if a substrate having a larger permittivity value is used.

Recently, new interfaces for bionic arm using surface electromyography (EMG) have been developed. To control bionic arms, the motion identification of five fingers using forearm muscle is required. However, estimation of independent muscle activity on five fingers is difficult because differential electrodes between two points have low spatial selectivity. On the other hand, small concentric ring electrodes have high spatial selectivity. Therefore, in this research, we showed possibility of independent measurement of EMG corresponding to each finger's movement using small concentric ring electrodes. Also, we compared Signal-Noise Ratio (SNR) of EMG for each finger's using differential electrodes between two points and a virtual concentric ring electrode by an array electrode (3×3).

Non-invasive electrohysterogram (EHG) recording could provide valuable information about uterine dynamics. Bipolar EHG has usually been performed using monopolar disposable electrodes. Recently concentric ring electrodes have been used for EHG recordings so as to acquire more localized electrical activity which may be helpful for deducing uterine contraction efficiency. Nevertheless concentric ring electrodes have commonly been implemented in rigid substrates. Therefore they do not adapt to the body surface curvature which may cause discomfort for patients and a poor contact between electrode and skin. The aim of this paper is to examine the feasibility of picking up EHG signals (BC-EHG) using a new flexible tripolar concentric ring (TCR) electrode placed on the abdominal surface, and to compare it with the conventional bipolar recordings. For this purpose, a total of 7 recording sessions were carried out in 7 pregnant women. Each recording implied simultaneous acquisition of one bipolar EHG signal and of two bipolar concentric EHG (BC-EHG) signals using the flexible TCR electrode. Then a set of temporal and spectral parameters was computed from both bipolar EHG and BC-EHG bursts. Experimental results show no noticeable difference in duration and in dominant frequency in Fast Wave High frequency range. Nonetheless, the low frequency content (0.1-0.2 Hz) of BC-EHG records is smaller than that of bipolar record. These results suggest that the new flexible TCR electrode permits to pick up uterine electrical activity and may provide additional information for deducing uterine efficiency.

Non-invasive electrical brain stimulation has shown potential utility as a treatment for seizures in epilepsy patients. Transcranial focal stimulation (TFS) via tripolar concentric ring electrodes (TCREs) has been effective in reducing seizure severity in acute rodent models, but it has yet to be determined whether or not it will serve as a viable long-term treatment strategy. Prior experiments indicate that a single dose of TFS via TCRE does not impact short- or long-term memory formation. The present study investigated if five daily doses of TFS via a TCRE on the scalp affected the memory. The spontaneous object recognition (SOR) test was used to evaluate the memory. Sham and TFS-treated groups were evaluated and both showed comparable levels of preference for novel objects, indicating successful memory formation. More work on repeated dosage strategies is important for establishing the safety and efficacy of TFS as a putative treatment.

We have previously shown that tripolar concentric ring electrode (TCRE) Laplacian electroencephalography (tEEG) has significantly better signal-to-noise ratio, spatial resolution, and mutual information than disc electrode electroencephalography (EEG). This paper compares the EEG signals acquired simultaneously from the outer ring of the TCRE (oTCRE), shorting all three elements of the TCRE (sTCRE) and disc electrode (disc) concurrently from nearly the same location on the human scalp. We calculated the average correlation for the time series between each pair of signals and average coherence over the pass-band frequencies between all pairs of signals as well. All the correlations and coherences were above 0.99. The results suggest that the oTCRE can be used to record EEG concurrently with tEEG from the same sensor at the same location.

In an effort to improve the bandwidth of the single layer reflectarray, this paper investigates the use of double concentric circular ring elements arranged in a range of sub-wavelength grids on a single layer of substrate. The double concentric circular ring elements used here allow an additional degree-of-freedom to improve the bandwidth. Based on the concentric ring element, four offset-fed 0.43m×0.43m (14.3λ×14.3λ) reflectarrays centered at 10 GHz with various element periodicities, namely λ/2, λ/3, λ/4 and λ/5 grids, are designed and developed. The measured results show that among the four reflectarrays, the one with λ/4 grid spacing achieves the broadest 2-dB gain bandwidth of 33% with an aperture efficiency of 36.2%.

Interest in uniformly illuminated density-tapered planar antenna arrays has recently revived. For arrays consisting of concentric rings of elements, we present an algorithm that calculates ring radii for generation of pencil beams without the need for prior specification of the number of rings. If element phases are allowed to differ, the algorithm also synthesizes density-tapered arrays generating axially symmetric shaped beams.

We present a new Video Fire Detection (VFD) system for surveillance applications in fire and security industries. The system consists of three modules: pixel-level processing to identify potential fire blobs, blob-based spatial-temporal feature extraction, and a Support Vector Machine (SVM) classifier. The proposed novel spatial-temporal features include a spatial-temporal structural feature and a spatial-temporal contour dynamics feature. The spatial-temporal structural features are extracted from an accumulated motion mask (AMM) and an accumulated intensity template (AIT), capturing the concentric ring structure of fire intensity. The spatial-temporal dynamics features are based on the Fourier descriptor of contours in space and time, capturing the dynamic properties of fire. These global blob-based features are more robust and effective in rejecting false alarms and nuisance sources than pixel-wise features. In addition, extraction of the spatial-temporal features is very efficient, and no tracking of blobs or contours is needed. We also present a new multi-spectrum fire video database for algorithm testing. We evaluate the effectiveness of the proposed features on fire detection on the video database and obtain very promising results.

This paper investigates a new designed element namely concentric element to improve the limited bandwidth of reflectarray element. This element is using single-layer configuration with an introduction of split concept into the element. The dual frequency operation is realized through the using of two elements of ring and ring square at 13.44 GHz and 18.36 GHz. The bandwidth broadening is observed improved from 19.8% to 20.3% in which comparable of solid and split element.

A tri-band frequency selective band-stop EMI shield is designed using various concentric rings with each ring resonating at the specific desired frequency. The shield is fabricated using roll-by-roll screen-printing process, making it suitable for large surface architectural shielding applications. The design is designed using full-wave simulation tool and the performance is validated experimentally.

Reflectarray antennas (RA) are nowadays a quite well established technology, used in several applications. Nevertheless, they still suffer for some limitations, that are partially due to their intrinsic reduced bandwidth, that could be enlarged, but generally with a drastic increase of the structure complexity. Here we propose a new type of re-radiating element, consisting in two concentric square rings in which two geometric parameters are varied. In this way it is possible to better control both the spatial and frequency phase variation of the re-radiated field. Numerical analysis of reduced size RAs has been carried out, and it confirms the promising characteristics of such radiating elements.

We propose polarization and angle insensitive metasurfaces for THz frequencies. The new unit cell consists of two concentric ring resonators with interdigitated fingers. The number of these fingers allows for controlling the sharpness of the bandstop resonance. A quality factor of more than 16 is observed. The experimental results are in very good agreement with the simulations.

Epilepsy affects approximately one percent of the world population. Antiepileptic drugs are ineffective in approximately 30% of patients and have side effects. We are developing a noninvasive, or minimally invasive, transcranial focal electrical stimulation (TFS) system through our novel concentric ring electrodes to control seizures. Here we report on the development of a seizure detecting algorithm to be used for automatic application of TFS. A cumulative sum (CUSUM) algorithm was evaluated that detected the electrographic seizure activity in all experiments well in advance of the behavioral seizure activity.

In this paper, multiple concentric rings are considered as phase elements in reflectarrays and the benefits of these single layer rings are compared to conventional reflective structures (multi and single layer, rectangular or elliptical printed patches) when applied to the design of reflectarrays. These ring-shaped structures have got, as the main advantages, the ease of manufacture and the wide range of phase obtained, exceeding easily 1000 degrees. The analysis of the structures is made by means of the CG-FFT method. The simulations are carried out in the Ku band, the one commonly used in Direct Broadcast Satellite applications (DBS). In order to determine the effect of the manufacturing tolerances, results of a test carried out with a simulated reflectarray are included, using a PSO based algorithm to perform the phase synthesis.

In this paper we continue numerical and experimental investigations of highly birefringent microstructured fibers (HiBi MSFs) proposed earlier [1,2]. These HiBi MSFs have an elliptical or circular core surrounded by two or more concentric rings of holes of constant diameter d. The holes in the first ring around the core have equal spacing Λ between the centers, except one or two pairs of holes with increased spacing Λ1. For convenience, we use the following code name characterizing the new HiBi MSF structure: MNKLec, where M is the number of holes in the first ring; N is the number of gaps in the first ring; K is the number of additional holes, which cover the gaps; L is the number of holes in the second ring; e means that the core is elliptical (c, circular); c means that the holes are circular (e, elliptical). To characterize the HiBi MSF shape, we use parameter δ defined as the deviation of the angle between adjacent holes in the first ring from its maximum value.

A pattern synthesis method based on Gravitational Search Algorithm (GSA) is presented to generate a dual pencil beam patterns with two different pre-defined sidelobe levels from a concentric ring array of isotropic antennas. Both the patterns are generated by sharing a common optimum amplitude distribution of the array elements. The pattern with sidelobe level lower than the other is generated by switching phase distribution of the array elements from zero to the optimum value. The amplitude and the phase of the array elements are varied radially along the array using GSA to generate a dual pencil beam of two different sidelobe levels.

Reduction of sidelobe level in a concentric ring array results in wide first null beamwidth. The authors propose a pattern synthesis method based on the Differential Evolution (DE) algorithm to reduce the sidelobe level of a concentric ring array of isotropic antennas while keeping the first null beamwidth (FNBW) fixed and variable by optimizing both ring spacing and interelement distance of each ring.

High intensity focused ultrasound (HIFU) guided by magnetic resonance imaging (MRI) is a noninvasive treatment that can potentially reduce morbidity, lower costs, and widen accessibility for patients with upper abdominal cancers. Traditionally, piezoelectric transducers are used for HIFU, but recent developments in capacitive micromachined ultrasonic transducers (CMUTs) have made them competitive. Previously, we designed, fabricated, and tested HIFU CMUTs for use under MRI guidance and demonstrated successful unfocused heating of a HIFU phantom. In this paper, we use this CMUT design in the construction of an 8-element, equal area, concentric ring array for ablation of upper abdominal cancers. We report on the measurement of the beam profile of the transducer and compare it to models; in addition, we report on the effects of acoustic crosstalk on this array.

A ring array is a planar array with elements lying on a circle. If several of these arrays with different radii share a common center, then the resulting planar array is known as a concentric ring array. This paper demonstrates the optimized thinning of concentric ring arrays using point sources and dipoles.

The western Heilongjiang Province is one of the most important land saline-alkalization region in China. Taking the vector data of land saline-alkalization in 1976 and 2001 as the information source, the paper evaluated the degree of land saline-alkalization in the west of Heilongjiang Province, and analyzed spatial-temporal variation characteristics of land saline-alkalization by raster technology and ordinary kriging fitting method in Geostatistics. The results showed that the degree of land saline-alkalization was lower than 0.4 except Daqing urban areas in 1976. Furthermore, it took three points as land saline-alkalization center, and the field was reduced nearly concentric ring outwards, and degree of land saline-alkalization was generally lower; the land saline-alkalization degree of Lindian county proved to have the largest increase in 2001, the second were Daqing urban areas, Zhaoyuan county and Dumeng county. The land saline-alkalization degree took only one point as center, and the field was reduced nearly coaxial strip of width outwards, , which is generally higher than that of 1976.

Grounding characteristics of linear, star-type and toroidal electrodes are discussed in this paper. Based on the analysis of the performance of double-ring in uniform and horizontal two-layer soils, an electrode model of standard triple concentric rings buried with different depth is presented for plusmn800 kV Xiluodu and Xiangjiaba converter stations in the first period of Jinsha River DC projects. Considering the three sending converter stations in the projects close to each other relatively, an initial analysis of sharing electrodes has been made, including the operation mode of converter stations, choice of rated current and the design model of electrodes. Simulation results obtained from the electrode sites primarily selected for Xiluodu right-bank converter station show that the above model can satisfy the operation requirements with a better economical performance and sharing electrodes by multi-converter stations is also feasible. They may supply some reference to the practical projects.

Partial adaptation is often used to reduce the computation and improve the tracking ability of an adaptive array. In some practical situations, the received signal to be processed contains some interferences whose characteristics are known. The previously proposed partially adaptive concentric ring array is not able to utilize the prior information of known interferences without sacrificing the number of degrees of freedom, which causes higher steady state error and smaller number of interferences that can be cancelled. We propose in this paper an improved partially adaptive concentric ring array that can utilize the prior knowledge to improve the performance and maintain the same number of degrees of freedom. The proposed method designs the non-adaptive weights to remove the known interferences, and is shown to provide much faster convergence speed and lower steady state error than the original method

The influence of the thermal treatment during the saw damage etching process on the mechanical stability of multicrystalline silicon wafers has been investigated for four different alkaline saw damage etching procedures. After the different etching procedures the mechanical stabilities of the multicrystalline wafers have been measured using the concentric ring test and the four-point-bending test. The experimental results are compared to those obtained by numerical simulations.

Ultrasound hyperthermia has been used extensively as an adjuvant therapy along with radiation. Typically, single element applicators are used in clinical or operating room (OR) treatments. Patient discomfort often limits the hyperthermia treatments in clinical settings, but is removed as a factor in the OR. Still, the limitations of shaping power distribution by a single element applicator have fostered multi-element applicator development. The results of concentric ring and mosaic applicators are compared to single element applicators in hyperthermia patient treatments. By introducing radial and 2-dimensional power shaping, high central peak temperatures are avoided and temperature profiles assume a flatter distribution. INTRODUCIlON

Potentials on the body surface from the heart are of a spatial and temporal function. The 12-lead electrocardiogram (ECG) provides useful global temporal assessment, but it yields limited spatial information due to the smoothing effect caused by the volume conductor. The smoothing complicates identification of multiple simultaneous bioelectrical events. In an attempt to circumvent the smoothing problem, some researchers used a five-point method (FPM) to numerically estimate the analytical solution of the Laplacian with an array of monopolar electrodes. The FPM is generalized to develop a bi-polar concentric ring electrode system. We have developed a new Laplacian ECG sensor, a trielectrode sensor, based on a nine-point method (NPM) numerical approximation of the analytical Laplacian. For a comparison, the NPM, FPM and compact NPM were calculated over a 400 /spl times/ 400 mesh with 1/400 spacing. Tri and bi-electrode sensors were also simulated and their Laplacian estimates were compared against the analytical Laplacian. We found that tri-electrode sensors have a much-improved accuracy with significantly less relative and maximum errors in estimating the Laplacian operator. Apart from the higher accuracy, our new electrode configuration will allow better localization of the electrical activity of the heart than bi-electrode configurations.