bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mobile transmit diversity for base‐station antenna arrays
Authors: Kavak Adnan , Xu Guanghan 
Published: August 2002

AbstractFor base‐station antenna arrays operating at 1.8 GHz in urban vehicular environments, we experimentally investigate the spatial diversity provided by transmitting from the mobile terminal with two λ/2 dipole antennas that are separated by λ/2 and arranged in copolarized (CP) and cross‐polarized (XP) configurations. The results show that, in both configurations, spatial signatures observed at the antenna array associated with each antenna element of the mobile change differently, especially when nonline‐of‐sight communication exists. The relative variation of spatial signatures is larger in an XP configuration compared to a CP configuration. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 95–97, 2001.
Application of nested multigrid finite elements to two‐dimensional electromagnetic scattering
Authors: Zhu Yu , Cangellaris Andreas C. 
Published: August 2002

AbstractNested multigrid techniques are combined with the finite‐element method for the fast numerical solution of two‐dimensional electromagnetic scattering problems. The finite‐element modeling is performed on nested meshes of the same computational domain. The conjugate‐gradient method is used to solve the resultant finite‐element matrix for the finest mesh, while the multigrid method acts as the preconditioner of the iterative solver. Numerical experiments are used to demonstrate the efficiency as well as the limits of the proposed methodology. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 97–101, 2001.
Ka‐Band pulsed propagation through rain‐filled atmosphere
Authors: Maitra A. , Chowdhury A. S. , Das A. 
Published: August 2002

AbstractAn atmosphere of rain offers a dispersive medium for the propagation of radio signals above 10 GHz. The effect of dispersion, in terms of differential attenuation and phase dispersion, is insignificant for narrowband signals. Signals modulated with very short pulses can have a wide bandwidth over which dispersion will be appreciable, causing significant signal distortion. The propagation of pulsed signals under varying propagation conditions has been studied with the Fourier transform technique. The transfer function of the rain atmosphere is obtained using propagation models that include clear‐air effects and scattering effects due to raindrops. The carrier signal at 30 GHz is considered to be modulated by a raised‐cosine pulse with a base bandwidth of 1–3 GHz. A technique for the mitigation of pulse distortion using an FIR filter is presented to restore the distorted pulse to its original shape and position to a significant extent. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 105–109, 2001.
Theory and numerical analysis of higher order dispersion effects on ultra‐high‐speed nonlinear optical loop mirror demultiplexer
Authors: Zhang Fan , Ye Peida 
Published: August 2002

AbstractThe effects of higher order dispersion are analyzed for the first time in ultra‐fast signal demultiplexing using a nonlinear optical loop mirror (NOLM). The results show that performance degradation of NOLM can occur when higher order dispersion is not negligible. Therefore, a loop fiber with a higher order dispersion that is as small as possible should be chosen to realize terabit/second operation of the NOLM. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 124–127, 2001.
Erratum to “FDTD Analysis and Design of Probe‐Fed Dual‐Polarized Circular Stacked Patch Antenna”
Authors: Paul Dominique L. , Craddock Ian J. , Railton Chris J. , Fletcher Paul N. , Dean Michael 
Published: August 2002

AbstractThis contribution shows that the FDTD technique is an effective design tool for producing dual‐polarized circular stacked patch antennas. Computational requirements may be minimized by careful modeling of the coaxial feedline, including the use of mode filtering at the aperture plane of the antenna. The design process for an antenna at a frequency of 4.7 GHz is described, and results obtained for return loss and coupling between the two ports of the antenna and radiation patterns are presented. These are in very good agreement with experimental data. © 2001 Crown Copyright. Published with permission of the Defence Evaluation and Research Agency on behalf of the controller HMSO Microwave Opt Technol Lett 30: 145–147, 2001.
Study of distributions of modes and plane waves in reverberation chambers for the characterization of antennas in a multipath environment
Authors: Rosengren Kent , Kildal Per‐Simon 
Published: August 2002

AbstractA rectangular metallic cavity is known to support a number of resonant cavity modes. Each of these modes can be described as a sum of eight plane waves incident from different angles. This paper studies how these plane waves are angularly distributed in space, which is of interest when the cavity is used to simulate multipath environment. The results show that the angular distribution in space is uniform provided that the three linear dimensions of the chamber are sufficiently large, and do not deviate too much from each other. As an example, two rectangular cavities with dimensions 1 m×0.8 m×1 m and 5.5 m×2.5 m×3.5 m are analyzed in detail, and are shown to have uniform plane‐wave distributions. We also demonstrate how the chamber geometry may be chosen in order to weight the angular plane‐wave distribution in the elevation plane. A result of the study is that we detect a 25 MHz frequency band with very few modes in a small chamber designed for use with reduced accuracy in the GSM 900 MHz band. We also propose how this chamber can be modified to obtain uniform mode distribution over this frequency band. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 386–391, 2001.
Optical regeneration using a feedforward semiconductor optical amplifier with chirp‐controlled filtering
Authors: Conforti Evandro , Gallep Cristiano M. , Bordonalli Aldário C. , Kang Sung‐Mo (Steve) 
Published: August 2002

AbstractOptical pulse regeneration and reshaping using nonlinear optical pulse amplification followed by a chirp‐controlled filtering is simulated. The nonlinear amplification and chirp control are obtained by feedforward current injection in a semiconductor optical amplifier. The nonlinear amplification provides pulse regeneration, and the controlled chirp, in association with an optical frequency discriminator, can be used to optimize the shape of several Gbit/s pulse streams. The simulator model has been confirmed experimentally using eye diagram techniques. In addition, the switching action of an optical semiconductor amplifier with a dynamically arbitrarily injected current can be simulated. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 438–442, 2001.
Analysis and bandwidth enhancement of Sierpinski carpet antenna
Authors: Wong S. , Ooi B. L. 
Published: August 2002

AbstractThe boundary integral method coupled with the segmentation method have been used for the first time to analyze Sierpinski carpet antennas of different orders. As is evident from the close agreement between calculated and measured results for the resonant frequency and input return loss, this technique is found to predict the impedance characteristic accurately. A novel stacked microstrip Sierpinski carpet fractal antenna using a photonic bandgap structure is also presented. Compared to an ordinary microstrip fractal antenna, which has a maximum bandwidth of 2%, the proposed antenna has a higher input impedance bandwidth of about 9%. The radiation patterns of the proposed antenna are improved due to the removal of unwanted radiation caused by the surface wave. The experimental measurement results of the proposed antenna are presented in this paper. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 13–18, 2001.
Fast algorithm for matrix–vector multiply of asymmetric multilevel block‐Toeplitz matrices in 3‐D scattering
Authors: Barrowes Benjamin E. , Teixeira Fernando L. , Kong Jin A. 
Published: August 2002

AbstractA newO(N log N) FFT‐based method to expedite matrix–vector multiplies involving multilevel block‐Toeplitz (MBT) matrices is presented. The method is also a minimal memory method withO(N) memory requirements because only nonredundant entries of the MBT matrix are stored. The accuracy and convergence of the method are illustrated in the calculation of the scattered field and the effective permittivity of a sphere with size parameter ka up to 5 using a volume integral formulation akin to the discrete dipole approximation. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 28–32, 2001.
Buried‐object detection using free‐space time‐domain near‐field measurements
Authors: Biju Kumar S. , Aanandan C. K. , Mathew K. T. 
Published: August 2002

AbstractThe detection of buried objects using time‐domain free‐space measurements was carried out in the near field. The location of a hidden object was determined from an analysis of the reflected signal. This method can be extended to detect any number of objects. Measurements were carried out in the X‐ and Ku‐bands using ordinary rectangular pyramidal horn antennas of gain ∼15 dB. The same antenna was used as the transmitter and receiver. The experimental results were compared with simulated results by applying the two‐dimensional finite‐difference time‐domain (FDTD) method, and agree well with each other. The dispersive nature of the dielectric medium was considered for the simulation. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 45–47, 2001.
Far‐field pattern calculation in body‐of‐revolution finite‐difference time‐domain (BOR–FDTD) method
Authors: Yu Wenhua , Farahat Nader , Mittra Raj 
Published: August 2002

AbstractIn this paper, we present a far‐field pattern calculation technique in the body‐of‐revolution finite‐difference time‐domain (BOR–FDTD) method. Because the BOR–FDTD solves two‐ and half‐dimensional problems, it has different features from the three‐dimensional FDTD method in the far‐field pattern calculation. A monopole antenna fed by a coax is used to validate the technique described in this paper. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 47–50, 2001.
Erratum to “Arrayed Helical Antennas (AHA) with Low SAR for Personal Telephone Handsets”
Authors: Hong Soo‐Won , Park Myeong‐Seok , Oh Hak‐Tae , Park Cheon‐Seok 
Published: August 2002

AbstractArrayed helical antennas (AHA) for personal telephone handsets have beendeveloped for both low‐SAR and omnidirectional radiation patterns, where the AHA has two helical antennas along the direction of the width on the top of personal telephones. A comparison of the SAR value between the AHA and a conventional helical antenna (CHA) demonstrates that the SAR value of the AHA is 35% less than that of the CHA. Good performance of the radiation patterns and the VSWR of the AHA are also shown by using the experimental measurements. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 396–397, 2002.
Survival trends of childhood cancer diagnosed during 1970–1994 in Piedmont, Italy: A report from the Childhood Cancer Registry
Authors: Pastore Guido , Mosso Maria Luisa , Carnevale Fabrizio , di Montezemolo Luca Cordero , Forni Marco , Madon Enrico , Ricardi Umberto , Terracini Benedetto , Magnani Corrado 
Published: August 2002

AbstractBackgroundThe Childhood Cancer Registry of Piedmont (CCRP) started its activity in 1967. It is population based and covers the Piedmont Region (population 4,500,000; NW Italy). This article reports on time trends in survival after a childhood cancer diagnosed during 1970–1994.ProcedureDuring 1970–1994, 2,329 incident cases were registered at CCRP on the basis of histological and/or clinical information, excluding 30 cases reported only by death certificate. Histological or hematological diagnosis was available for 2,067 cases. Vital status was assessed through the offices of the town of residence. At the end of follow‐up, 1,202 cases were alive, 1,084 dead and 43 were not traceable. Survival was measured for the major diagnostic groups using both univariate and multivariate statistics.ResultsThe 5‐yr survival rate for acute lymphoblastic leukemia (ALL) improved regularly from 24.7% in 1970–1974 to 81.1% in 1990–1994, for acute nonlymphoblastic leukemia (ANLL) from 0% to 38.1%, for non‐Hodgkin lymphoma (NHL) from 25.2% to 67.7%, for tumors of the central nervous system (CNS) (all types) from 33.4% to 75.9% and for Ewing tumor from 0% to 90%. Focusing on survival by period of diagnosis, the highest 5‐year survival rate was observed for children diagnosed during 1985–1989 for medulloblastoma, neuroblastoma (NB), retinoblastoma, Wilms tumor, osteosarcoma, and rhabdomyosarcoma and for children diagnosed in 1990–1994 for the remaining sites. The trend over time was statistically significant for ALL, ANLL, NHL, CNS tumors, NB, and osteosarcoma as well as for all malignancies together.ConclusionsPopulation‐based survival studies are useful complements to clinical studies. Survival results in the present study are similar to those presented for other European countries and the United States. For most types of neoplasm (except CNS) survival probability appears to stabilize 5–10 years after diagnosis. Med. Pediatr. Oncol. 36:481–488, 2001. © 2001 Wiley‐Liss, Inc.
Study design and cohort characteristics of the childhood cancer survivor study: A multi‐institutional collaborative project
Authors: Robison Leslie L. , Mertens Ann C. , Boice John D. , Breslow Norman E. , Donaldson Sarah S. , Green Daniel M. , Li Frederic P. , Meadows Anna T. , Mulvihill John J. , Neglia Joseph P. , Nesbit Mark E. , Packer Roger J. , Potter John D. , Sklar Charles A. , Smith Malcolm A. , Stovall Marilyn , Strong Louise C. , Yasui Yutaka , Zeltzer Lonnie K. 
Published: August 2002

AbstractBackgroundIncreased attention has been directed toward the long‐term health outcomes of survivors of childhood cancer. To facilitate such research, a multi‐institutional consortium established the Childhood Cancer Survivor Study (CCSS), a large, diverse, and well‐characterized cohort of 5‐year survivors of childhood and adolescent cancer.ProcedureEligibility for the CCSS cohort included a selected group of cancer diagnoses prior to age 21 years between 1970–1986 and survival for at least 5 years.ResultsA total of 20,276 eligible subjects were identified from the 25 contributing institutions, of whom 15% are considered lost to follow‐up. Currently, 14,054 subjects (69.3% of the eligible cohort) have participated by completing a 24‐page baseline questionnaire. The distribution of first diagnoses includes leukemia (33%), lymphoma (21%), neuroblastoma (7%), CNS tumor (13%), bone tumor (8%), kidney tumor (9%), and soft‐tissue sarcoma (9%). Abstraction of medical records for chemotherapy, radiation therapy, and surgical procedures has been successfully completed for 98% of study participants. Overall, 78% received radiotherapy and 73% chemotherapy.ConclusionThe CCSS represents the largest and most extensively characterized cohort of childhood and adolescent cancer survivors in North America. It serves as a resource for addressing important issues such as risk of second malignancies, endocrine and reproductive outcome, cardiopulmonary complications, and psychosocial implications, among this unique and ever‐growing population. Med. Pediatr. Oncol. 2002;38:229–239. © 2002 Wiley‐Liss, Inc.
Neuronal migration disorders
Authors: Gleeson Joseph G. 
Published: August 2002

AbstractNeuronal migration disorders are a category of developmental brain disorders leading to cortical dysplasia. This group of disorders is characterized by defective movement of neurons from the place of origin along the lining of the lateral ventricle, to the eventual place of residence in the correct laminar position within the cerebral cortex. As a result of defective migration, affected individuals typically display mental retardation and epilepsy. Although patients with the more severe forms of these disorders often present during infancy, patients may present at any age from newborn to adulthood. The migration defect may be generalized or focal, and may be disturbed at any of several stages, leading to several distinct radiographical and clinical presentations. The human phenotypes suggests that there are at least four distinct and clinically‐important steps in cortical neuronal migration, and the identification of the responsible genes suggests that multiple cellular processes are critical for correct neuronal positioning. MRDD Research Reviews 2001;7:167–171. © 2001 Wiley‐Liss, Inc.
Simulation‐based investigation of partially parallel imaging with a linear array at high accelerations
Authors: Bankson James A. , Wright Steven M. 
Published: August 2002

AbstractPartially parallel imaging strategies such as SMASH, SENSE, and PILS rely on the sensitivity distribution of phased array RF coils to reduce MRI imaging time. Using an N‐element phased array, these techniques allow maximum accelerations, L, such that L ≤ N, with acceleration defined as the factor by which scan time is reduced in comparison to traditional, fully gradient encoded acquisitions. As N increases in modern MRI facilities or using special hardware extensions, its role as the primary limitation in partially parallel imaging will be reduced and other limiting factors will become dominant. Two such factors include available SNR and the variation of sensitivity distributions with imaging depth. Simulations have been conducted to evaluate the impact of slice depth and noise on partially parallel reconstructions for the case of a square linear array of overlapped elements that are parallel to the imaging plane. Results indicate that even when sensitivity distributions are exactly known, the linear surface array can only provide high accelerations over a limited imaging depth due to changing suitability of the sensitivity distributions for partially parallel reconstruction. This work emphasizes the importance of simulations for target‐based partially parallel array design. Magn Reson Med 47:777–786, 2002. © 2002 Wiley‐Liss, Inc.
k‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized 3He MRI: Spatial resolution and signal‐to‐noise ratio considerations
Authors: Wild Jim M. , Paley Martyn N.J. , Viallon Magalie , Schreiber Wolfgang G. , van Beek Edwin J.R. , Griffiths Paul D. 
Published: August 2002

AbstractIn this work some of the factors that can influence the signal‐to‐noise ratio (SNR) and spatial resolution in MR images of inhaled hyperpolarized gases are systematically addressed. In particular, the effects of RF depletion of longitudinal polarization and image gradient diffusion dephasing were assessed in terms of their contribution to a k‐space filter. By means of theoretical simulations and a novel method of experimental validation using a variable transverse magnetization of the 1H signal, systematic quantitative and qualitative investigations of the effects of k‐space filtering intrinsic to imaging of hyperpolarized gas were made. A 2D gradient‐echo image is considered for a range of flip angles with centric, sequential, and half‐Fourier Cartesian phase‐encoding strategies, and the results are assessed in terms of SNR and spatial resolution in the reconstructed images. Centric phase encoding was found to give the best SNR at higher flip angles, with a trade‐off in spatial resolution compared to sequential phase encoding. A half‐Fourier approach potentially offers increased SNR through the use of higher flip angles without compromising the spatial resolution, which is comparable to that achieved with sequential encoding. Magn Reson Med 47:687–695, 2002. © 2002 Wiley‐Liss, Inc.
New approach to 3D time‐resolved angiography
Authors: Madore Bruno , Pelc Norbert J. 
Published: August 2002

AbstractTRICKS is an acquisition and reconstruction method capable of generating 3D time‐resolved angiograms. Arguably, the main problem with TRICKS is the way it handles the outer regions of the k‐space matrix, leading to artifacts at the edges of blood vessels. An alternative to the data‐ processing stage of TRICKS, designed to better represent edges and small vessels, is presented here. A weakness of the new approach is an increased sensitivity to motion compared to TRICKS. Since this method can use the same data as TRICKS, a hybrid reconstruction method could conceivably be developed where the advantages of both approaches are combined. Magn Reson Med 47:1022–1025, 2002. © 2002 Wiley‐Liss, Inc.
Reliable detection of macromolecules in single‐volume 1H NMR spectra of the human brain
Authors: Seeger Uwe , Mader Irina , Nägele Thomas , Grodd Wolfgang , Lutz Otto , Klose Uwe 
Published: August 2002

AbstractIn short echo time proton MR spectra of the brain, resonances from macromolecules are visible. The macromolecular resonances in the 0.5–2.0 ppm region can be affected by lipid contamination arising from fat‐containing regions outside the selected volume of interest (VOI). This study demonstrates that considerable lipid contamination may remain in stimulated echo acquisition mode (STEAM) spectra even if the spoiling of unwanted coherences is sufficient and the VOI is placed 2 cm or more away from fat‐containing regions. The observed contamination was attributed to residual remote out‐of‐volume excitation, although only very small out‐of‐slice ripples of less than 0.2% of the in‐slice excitation were found in the calculated excitation profile of the RF pulses. Spatial presaturation of fat‐containing regions led to a sufficient suppression of the contamination and enabled the detection of highly reproducible macromolecular resonances. Thus, in single‐volume spectroscopy as well as in spectroscopic imaging (SI or CSI), the combination of volume selection and outer volume presaturation, each in three dimensions, is highly recommended to ensure accurate detection and reliable evaluation of even small pathological alterations in macromolecules, e.g., proteins or lipids, or other resonances in the 0.5–2.0 ppm region. Magn Reson Med 45:948–954, 2001. © 2001 Wiley‐Liss, Inc.
Quantification of the effect of water exchange in dynamic contrast MRI perfusion measurements in the brain and heart
Authors: Larsson Henrik B.W. , Rosenbaum Sverre , Fritz‐Hansen Thomas 
Published: August 2002

AbstractMeasurement of myocardial and brain perfusion when using exogenous contrast agents (CAs) such as gadolinium‐DTPA (Gd‐DTPA) and MRI is affected by the diffusion of water between compartments. This water exchange may have an impact on signal enhancement, or, equivalently, on the longitudinal relaxation rate, and could therefore cause a systematic error in the calculation of perfusion (F) or the perfusion‐related parameter, the unidirectional influx constant over the capillary membranes (Ki). The aim of this study was to quantify the effect of water exchange on estimated perfusion (F or Ki) by using a realistic simulation. These results were verified by in vivo studies of the heart and brain in humans. The conclusion is that water exchange between the vascular and extravascular extracellular space has no effect on Ki estimation in the myocardium when a normal dose of Gd‐DTPA is used. Water exchange can have a significant effect on perfusion estimation (F) in the brain when using Gd‐DTPA, where it acts as an intravascular contrast agent. Magn Reson Med 46:272–281, 2001. © 2001 Wiley‐Liss, Inc.