Aperture Length Research Articles

Morphometric Relationships Between the Hermit Crab Isocheles sawayai (Forest & Saint Laurent) (Crustacea Anomura Diogenidae) and its Shell from Southern Brazil

A study on morphometric relationships between the hermit crab Isocheles sawayai and its shell in a population from Parana-Santa Catarina States coast was carried out. Hermit crabs from the by-catch of shrimp fishing (4-15m depth) were collected. Cephalothoracic shield length (CL) and width (CW) from hermit crabs and total length (SL), aperture length (AL) and weight (SW) from shells were taken. A total of 266 hermit crabs occupying eight species of shell - Buc- cinanops lamarckii, Dorsanum moniliferum, Oliva reticularis, Olivancillaria steeriae, O. urceus, Polinices hepaticus, Semicassis granulatum and Stramonita haemastoma - were obtained. Males (N = 189) that dominated strongly (1M : 0.4 F) occupied eight shell species, while females (N = 76) occupied only six. There was only one intersex individual that oc- cupied a Stramonita shell. Contrarily to intertidal populations, O. urceus was the most frequently occupied shell by males (57.14%) and females (62.33%) in this studied area. Due to the smaller size of females (mean CL 5.19±0.84mm), these ones occupied shells of a smaller size than males (mean CL 6.49±1.14mm). The highest O. urceus shell frequency of oc- cupation is connected to the hermit crabs life style: it is a filter feeding species and its shell remains totally buried in the sandy substratum having only its cephalothoracic appendages free. The heavy shell of this gastropod (highest SW/SL) fa- vors the stability in strong current water conditions, as it functions as an anchorage for this semi-buried hermit crab.

Large scale direct shear tests of soil/PET-yarn geogrid interfaces

The interface shear strength of soil against geosynthetic is of great interest among the researchers in geosynthetic properties. This study conducts a series of large scale direct shear tests to investigate the interface shear strength of different soils (sand, gravel, and laterite) against PET-yarn geogrids of various tensile strengths, percent open area, and aperture patterns. First, the appropriateness of different set-ups of a lower shearing box is examined in this study. It reveals that a lower box which is filled with the test soil and is of the same size as the upper box is more suitable for testing the soil/geogrid interface. The test results show that the soil/PET-yarn geotextile interface has significantly lower shear strength than soil strength. The ratio of shear strength soil/PET-yarn geotextile interface to internal shear strength of soil is about 0.7–0.8 for Ottawa sand and for laterite, and it is about 0.85–0.95 for gravel. On the other hand, the soil/geogrid interface has higher shear strength. The ratio of shear strength soil/PET-yarn geogrid interface to internal shear strength of soil is about 0.9–1.05. It is found that the shear strength ratio of soil/PET-yarn geogrid interface is positively correlated to the transverse tensile strength of the PET-yarn geogrid. However, it is negatively correlated with the aperture length and percent open area of the PET-yarn geogrid. The interface shear test results of PET-yarn geogrid against different soils are compared with the test results predicted by a classical model for analyzing the applicability of the classical model. Further, a simple model is proposed herein to estimate the bearing resistance provided by the transverse ribs of geogrid. It shows this component to be about 0–15% when PET-yarn geogrid is against Ottawa sand or laterite, while it is smaller when the PET-yarn geogrid is against gravel.

A Novel Modified Omega-K Algorithm for Synthetic Aperture Imaging Lidar through the Atmosphere.

The spatial resolution of a conventional imaging lidar system is constrained by the diffraction limit of the telescope's aperture. The combination of the lidar and synthetic aperture (SA) processing techniques may overcome the diffraction limit and pave the way for a higher resolution air borne or space borne remote sensor. Regarding the lidar transmitting frequency modulation continuous-wave (FMCW) signal, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. The given modified Omega-K algorithm takes the continuous motion into account, which can compensate for the Doppler shift induced by the continuous motion efficiently and azimuth ambiguity for the low pulse recurrence frequency limited by the tunable laser. And then, simulation of Phase Screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implemented in order to simulate turbulence. Finally, the computer simulation shows the validity of the modified algorithm and if in the turbulence the synthetic aperture length does not exceed the similar coherence length of the atmosphere for SAIL, we can ignore the effect of the turbulence.

Simultaneous measurement of pressure and temperature in a focused ultrasound field with a fiber optic hydrophone

The characterization of high intensity focused ultrasound (HIFU) fields is important for both clinical treatment planning as well as for regulation of HIFU medical devices. In previous work, we have used a 100-μm fiber optic probe hydrophone (FOPH) to measure pressure waveforms from a 2-MHz HIFU source with 42-mm aperture and 44-mm focal length. The formation of shock waves with peak positive pressure of up to 80-MPa were measured and modeled in transparent tissue-mimicking gel phantoms and boiling was achieved in milliseconds [Canney MS, et al., J. Acoust. Soc. Am., 120:3110 (2006)]. In this work, the FOPH was also used to measure temperature changes in tissue phantoms from HIFU at peak focal intensities of 5000-20,000 W/cm2. Temperature measurements were obtained by first low-pass filtering the voltage signal measured from the FOPH to remove the acoustic part of the measurement. Then, calibration of voltage to temperature was performed using results from a separate calibration experiment. Experimental measurements were compared with numerical modeling using a KZK-type model for acoustic propagation coupled with a heat transfer model. In summary, temperatures of 100°C were measured at the HIFU focus in milliseconds, in agreement with modeling [Work supported by NIH DK43881, NSBRI SMS00402, and RFBR.]

Stress effects on permeability in a fractured rock mass with correlated fracture length and aperture

The effect of stress on permeability and fluid flow patterns in fractured rock masses is studied when distributed fracture aperture is correlated with fracture trace length, using a discrete element method (DEM). The basic assumptions are that the rock matrix is impermeable and linearly elastic, and that the fluid flows only in fractures. A new nonlinear algorithm is developed for prediction of normal stress–normal displacement behavior of fractures based on the Bandis model and the correlation between aperture and length. The results show that when small stress ratios ( K=horizontal/vertical stress) are applied at the model boundaries, the overall permeability of the fracture network is generally decreased. However, contribution from a few large fractures of higher hydraulic conductivity prevents drastic reduction of the overall permeability, compared with models that assume uniform fracture apertures. With large values of the stress ratio, both the overall permeability and flow patterns are controlled by a combination of highly conductive larger fractures and fractures with shear slipping and dilation, with much increased overall permeability and shear-induced flow channeling. With increasing stress ratios, it becomes more and more difficult to establish an equivalent permeability tensor and representative elementary volume (REV) of a fractured rock, compared with the unstressed model. These results show significant difference between correlated and non-correlated aperture and fracture length distributions, and highlight more significant scale and stress dependence of hydro-mechanical behavior of fractures rocks when geometric parameters of rock fractures are correlated.

Influence of prior experience on shell selection by the white spotwrist hermit crab Pagurus criniticornis (Crustacea: Paguridae)

Individuals of Pagurus criniticornis in a free-choice situation were experimentally tested under different laboratory conditions. In order to assess the effect of recently occupied shells on the size- and type-preference by hermit crabs, individuals were held for 30 days under one of the following two conditions: (1) excess of shells and (2) absence of shells. The crabs were then allowed to select shells from a wide array of empty gastropod shells of the two most-occupied species, as observed previously in the field: Cerithium atratum and Morula nodulosa. Preferred shell type (species) and size (shell aperture width and length) were correlated with hermit-crab size. The crabs showed a strong (100%) preference for C. atratum shells, demonstrating that recent and past experience did not influence either shell-type or shell-size preferences in this pagurid.

Consideration of digital filtering during selection of parameters of multichannel continuously scanning digital X-ray radiography systems

The problem of optimal selection of the aperture length of an individual detector in a linear array, the radiation detection time, and the pulsed response of a digital filter has been solved in two versions for continuously scanning digital X-ray radiography systems containing a linear detector array. The maximum spatial resolution of the system in the scanning direction at a specified testing capacity served as the criterion for the optimal selection.

Chilina iguazuensis (Gastropoda: Chilinidae), New Species From Iguazú National Park, Argentina

The Chilinidae comprises 16 species currently cited for Argentina, mostly distributed in Patagonia. All original descriptions of these species have been based on shell characters, and their internal anatomy is poorly known. Here a new species, Chilina iguazuensis, is described, including shell, radula, and reproductive and nervous systems. This species, found in Iguazú National Park, Misiones Province, Argentina, in the Upper Iguazú River rapids, has the following distinctive characteristics: aperture length equal to last whorl length; central radular tooth asymmetric and bicuspid, with both cusps serrated; and prepuce length 60% of penis sheath length. Chilina iguazuensis is endemic in Iguazú National Park, along with Chilina megastoma, which inhabits waterfalls in the same river.

Efecto del tamaño de probeta y orientación en la resistencia a la tracción y a la tenacidad a la fractura

In this work, an experimental research was conducted to determine size and orientation effects on tension and toughness properties through CTOD-R curves, using standard and miniature specimens taken from a structural steel plate. Compliance function estimation for the miniature size samples through load-displacement curves was considered. Experimental and statistical results showed that size and orientation affect tension and toughness properties. The miniature tension test specimens showed strength values slightly greater than the standard ones but with less ductility. Miniature specimen CTOD-R curves showed sensibility to load changes and measurement method of crack aperture and crack length. Inconsistency in fracture toughness for specimen orientation longitudinal circumferential (LC) regarding size effect was also observed. Short orientations showed less strength and toughness than the other directions.

Radar Signatures of a Passenger Car

Upcoming new synthetic aperture radar (SAR) satellites such as TerraSAR-X and Radarsat-2 offer high spatial image resolution and dual receive antenna capabilities, which open new opportunities for worldwide traffic monitoring applications. If the radar cross section (RCS) of the vehicles is strong enough, they can be detected in the SAR data, and their speed can be measured. For system performance prediction and algorithm development, it is therefore indispensable to know the RCS of typical passenger cars. The geometry parameters that have to be considered are the radar look direction, incidence angle, and vehicle orientation. In this letter, the radar signatures of nonmoving or parking cars are presented. They are measured experimentally from airborne experimental SAR (E-SAR) data, which have been collected during flight campaigns in 2005 and 2006 with multiple overflights at different aircraft headings. The radar signatures could be measured for the whole range of aspect angles from 0 to 180 and with high angular resolution due to the large synthetic aperture length of the E-SAR radar sensor. The analysis for one type of passenger car and particular incidence angles showed that the largest radar cross-sectional values and, thus, the greatest chance of detection of the vehicles appear when the car is seen from the front, back, and side. Radar cross-sectional values for slanted views are much lower and are therefore less suitable for car detection. The measurements have been performed in the -band (9.6 GHz) with VV-polarization, and at incidence angles of 41.5deg and 42.5deg. The derived radar signature profile can also be used for the verification of radar cross-sectional simulation studies.

Coupling coefficient determination based on simulation and experiment for ST-Cut quartz saw delay-line response

This paper used the theoretical calculation to simulate the response of surface acoustic wave (SAW) delay-line on quartz substrate and then compared to the experimental results. The coupling coefficients affected by operation frequency as well as aperture length were built up by experimental data analysis. Based on the experimental values of these two parameters, the device-coupling coefficient was defined. This method is new and we has not found in other document. In addition, it improves the simulation results and helps the analysis process more comprehensive. This study developed ST-cut quartz SAW delay-lines with gold inter-digital transducer (IDT) operating at 39.5 and 78.9 MHz corresponding to 80 and 40 μm of the wavelength. The differences of aperture length in IDT designs were investigated to help understand the effects of this parameter on SAW sensor response. The maximum error of operating frequency is 1%; of insertion loss is 4.25 and 3.13% for bandwidth. The larger of the insertion loss error is expected owing to the result of mathematical approximation and the quality of quartz substrate. The simulation results agree with the experimental results shows that the simulation method can apply to quartz-based SAW delay-line as well as for other material based SAW delay-line applications. The results help understand more about the parameters which effect the insertion loss, operating frequency and bandwidth. It should be very useful for IDT design in specific, SAW sensor and SAW filter design in general.

Growth models and shell morphometrics of two populations of Melanoides tuberculata (Thiaridae) living in hot springs and freshwater pools

Two morphologically different populations of snail, Melanoides tuberculata (Muller, 1774), were observed at Azraq Oasis, Jordan. Snails at the hot spring, where water temperature is higher than ambient, looked larger than those at the pools. The purpose of this study is to find out if there are differences in morphometrics, age, and growth due to the variation in water temperature and to quantify these differences. Snails were randomly collected from both sites, measured and statistically and mathematically analyzed for age, growth, and shell morphometric. Results indicate that snails from hot spring and pools may survive for five and four years, respectively. Theoretically, snails from the hot springs may reach 56.0 and snails from the pools may reach 28.0 mm in length. However, observed lengths reached 30.0 and 19.6 mm, respectively. The relationships of the shell length to shell and dry weights are curvilinear. However, the relationships of the shell length to shell width, aperture length, and aperture width are linear. There is an indication of an effect due to temperature difference on the age, growth and the morphometrics of the two populations of M. tuberculata.

MMSE/EGC adaptive selection for nonuniformly aligned adaptive array antenna

AbstractWhen an adaptive array antenna is used in cellular and other mobile communication base stations for the purpose of improving SINR, the array antenna itself sometimes falls into a fading valley, resulting in failure to obtain an adequate improvement effect. While this problem can be solved by increasing the aperture length of the array antenna, simply increasing the aperture length alone increases the number of antenna elements, so that a large‐scale adaptive array antenna becomes required, leading to the problem of failure of the weighting to track changes in the environment during fast fading. In this paper, we try to solve the first issue by making the element spacing nonuniformly aligned, reducing the number of elements. For the second issue, the weighting is divided into two layers, resolving the problem through both use of MMSE to eliminate interference and use of EGC for diversity combining. In a slow fading environment, however, favorable characteristics can be obtained when the entire weighting is controlled by MMSE. In this paper, we estimate the fading speed by the amount of envelope fluctuation in the desired signal after elimination of interference by the initial layer MMSE, and propose during slow fading the use of MMSE batch control, and during fast fading a control that incorporates both MMSE and EGC diversity combining. Finally, we use a computer simulation to evaluate the validity. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(12): 13–21, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20397

Measurement of radar signatures of passenger cars: airborne SAR multi-frequency and polarimetric experiment

The launch of SAR satellites with high-resolution and dual-receive antenna capabilities opens new possibilities for traffic-monitoring applications on a global scale. Thus, it will be possible to detect cars and measure their speed from the acquired along track interferometric data. The development of vehicle-detection algorithms requires the knowledge of the radar signatures of vehicles, especially under consideration of the geometry of the radar look direction and the vehicle orientation. The radar signatures of the non-moving cars are presented. They are estimated experimentally from airborne E-SAR multi-frequency and polarimetric data, which have been collected during a flight campaign in 2003. Radar signatures are estimated for a considerable part of aspect angles ranging from 0° to 180°. The large synthetic aperture length of the E-SAR radar sensor allows the look processing of data and therefore allows an increase of the aspect angle resolution. The radar signature analysis for one type of passenger cars showed that the largest radar cross-section values and thus the greatest chance for high probability of detection are for cars standing in rear and front views of radar beam direction. This holds true for all frequencies and co-polarisations. Radar cross-section values for cross-polarisations and diagonal views are much lower and are therefore less suitable for car detection. The radar signature profile over a considerable range of aspect angles in fine resolution can be used further for the verification of simulation studies and for the performance prediction for traffic monitoring with a coming German TerraSAR-X satellite.

Higher than optimum temperature under CO 2 enrichment influences stomata anatomical characters in rose ( Rosa hybrida)

There is little available information on the effects of temperature and CO 2 enrichment on stomata anatomical characteristics of plants. Effect of these two microclimates was studied on five rose ( Rosa spp.) cultivars, viz. ‘First Red’ (used as check), ‘Arjun’, ‘Raktima’, ‘Raktagandha’ and ‘Pusa Pitamber’. Budded, single-stemmed rose cultivars having five lateral buds were grown in controlled environment growth cabinets under enriched CO 2 (1000 μmol mol −1) and optimum (28/18 °C, T 0) or high (35/25 °C, T 1) temperature for 50 days. All observations were made on the abaxial leaf surface. Significant increases in stomatal density (68.7%), index (29.6%) and epidermal cell density (37.3%) were recorded in plants grown at high temperature over control with CO 2 enrichment. The cultivars responded differently in terms of length and width of guard cell and stoma (pore) under high temperature, however, the values averaged over treatments showed a significant reduction in these parameters. Further, number of stomata per leaf was higher (28.3%) in plants grown at high temperature, except First Red. A reduction in mean leaf area (26.7%) and dry mass (32.0%) was recorded at high rather than optimum temperature. The specific leaf area was maximum in Arjun (87%) while in First Red, a 14% reduction was noted at high temperature. The changes in the stomatal aperture (length and width of guard cell and stoma) did not show a clear pattern in response to higher temperature under CO 2 enrichment, which suggests that it is a genotypic character. Our data also show that temperature is potentially a more important factor determining stomatal anatomy than other environmental factors. Thus, this study provides an important database on stomatal anatomy for two important microclimates which is of direct significance to ornamental horticulture.

Synthetic aperture processing of reflection profiling data

Chirp sonar data are processed using synthetic aperture processing to improve the spatial resolution and subsurface penetration of reflection profiles of the seabed. Synthetic aperture processing is implemented by calculating the vertical change in the positions of acoustic transducers between transmission and using the offsets to time shift the acoustic data so that reflectors are summed coherently. The changes in projector and hydrophone positions between successive transmissions are calculated based on Doppler velocity log and inertial measurement unit measurements of vehicle motion. The pulse repetition interval can exceed half‐wavelength spacing by increasing the number of physical hydrophone channels. Imagery generated from reflection profiles of seabeds generated in several depositional environments are compared, and used to quantify the improvement in the spatial resolution and the SNR of reflection profiles as a function of the length of the synthetic aperture.

Self-calibration for transmitted wavefront measurements

Micro-optic components and subsystems are becoming increasingly important in optical sensors, communications, data storage, and many other diverse applications. To adequately predict the performance of the final system, it is important to understand the element's effect on the wavefront as it propagates through the system. The wavefront can be measured using interferometric means, however, random and systematic errors contribute to the measurement. Self-calibration techniques exploit symmetries of the measurement or averaging techniques to separate the systematic errors of the instrument from the errors in the test lens. If the transmitted wavefront of a ball lens is measured in a number of random orientations and the measurements are averaged, the only remaining deviations from a perfect wavefront will be spherical aberration from the ball lens and the systematic errors of the interferometer. If the radius, aperture, and focal length of the ball lens are known, the spherical aberration can be calculated and subtracted, leaving only the systematic errors of the interferometer. We develop the theory behind the technique and illustrate the approach with a description of the calibration of a microinterferometer used to measure the transmitted wavefront error of micro-optics.

A Two-Dimensional Bandwidth Extrapolation Technique for Polarimetric Synthetic Aperture Radar Images

The resolution of a synthetic aperture radar (SAR) image, in range and azimuth, is determined by the transmitted bandwidth and the synthetic aperture length, respectively. Various superresolution techniques for improving resolution have been proposed, and we have proposed an algorithm that we call polarimetric bandwidth extrapolation (PBWE). To apply PBWE to a radar image, one needs to first apply PBWE in the range direction and then in the azimuth direction, or <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vice versa </i> . In this paper, PBWE is further extended to the 2-D case. This extended case (2D-PBWE) utilizes a 2-D polarimetric linear prediction model and expands the spatial frequency bandwidth in range and azimuth directions simultaneously. The performance of the 2D-PBWE is shown through a simulated radar image and a real polarimetric SAR image

Hydraulic properties of fractured rock masses with correlated fracture length and aperture

Permeability of fractured rocks is investigated considering the correlation between distributed fracture aperture and trace length, based on a newly developed correlation equation. The influence of the second moment of the lognormal distribution of apertures on the existence of representative elementary volume (REV), and the possibility of equivalent permeability tensor of the fractured rock mass, is examined by simulating flow through a large number of stochastic discrete fracture network (DFN) models of varying sizes and varying fracture properties. The REV size of the DFN models increases with the increase of the second moment of the lognormal distribution, for both the correlated and uncorrelated cases. The variation of overall permeability between different stochastic realizations is an order of magnitude larger when the aperture and length are correlated than when they are uncorrelated. The mean square error of the directional permeability increases with increasing value of the second moment of the lognormal distribution function, and good fitting to an ellipsis of permeability tensor can only be reached with very large sizes of DFN models, compared with the case of constant fracture aperture, regardless of fracture trace length.

High-Frequency Ultrasonic Imaging of the Anterior Segment Using an Annular Array Transducer

Very high-frequency ultrasound (VHFU; >35 megahertz [MHz]) allows imaging of anterior segment structures of the eye with a resolution of less than 40 microm. The low focal ratio of VHFU transducers, however, results in a depth of field (DOF) of less than 1 mm. The aim was to develop a high-frequency annular array transducer for ocular imaging with improved DOF, sensitivity, and resolution compared with conventional transducers. Experimental study. Cadaver eyes, ex vivo cow eyes, in vivo rabbit eyes. A spherically curved annular array ultrasound transducer was fabricated. The array consisted of 5 concentric rings of equal area, had an overall aperture of 6 mm, and a geometric focus of 12 mm. The nominal center frequency of all array elements was 40 MHz. An experimental system was designed in which a single array element was pulsed and echo data were recorded from all elements. By sequentially pulsing each element, echo data were acquired for all 25 transmit-and-receive annuli combinations. The echo data then were focused synthetically and composite images were produced. Transducer operation was tested by scanning a test object consisting of a series of 25-microm diameter wires spaced at increasing range from the transducer. Imaging capabilities of the annular array were demonstrated in ex vivo bovine, in vivo rabbit, and human cadaver eyes. Depth of field, resolution, and sensitivity. The wire scans verified the operation of the array and demonstrated a 6.0-mm DOF, compared with the 1.0-mm DOF of a conventional single-element transducer of comparable frequency, aperture, and focal length. B-mode images of ex vivo bovine, in vivo rabbit, and cadaver eyes showed that although the single-element transducer had high sensitivity and resolution within 1 to 2 mm of its focus, the array with synthetic focusing maintained this quality over a 6-mm DOF. An annular array for high-resolution ocular imaging has been demonstrated. This technology offers improved DOF, sensitivity, and lateral resolution compared with single-element fixed focus transducers currently used for VHFU imaging of the eye.