Sparse Reconstruction for Near-Field MIMO Radar Imaging Using Fast Multipole Method

Radar imaging using multiple input multiple output systems are becoming popular recently. These applications typically contain a sparse scene and the imaging system is challenged by the requirement of high quality real-time image reconstruction from under-sampled measurements via compressive sensing. In this paper, we deal with obtaining sparse solution to near- field radar imaging problems by developing efficient sparse reconstruction, which avoid storing and using large-scale sensing matrices. We demonstrate that the "fast multipole method" can be employed within sparse reconstruction algorithms to efficiently compute the sensing operator and its adjoint (backward) operator, hence improving the computation speed and memory usage, especially for large-scale 3-D imaging problems. For several near-field imaging scenarios including point scatterers and 2-D/3-D extended targets, the performances of sparse reconstruction algorithms are numerically tested in comparison with a classical solver. Furthermore, effectiveness of the fast multipole method and efficient reconstruction are illustrated in terms of memory requirement and processing time

Magnetospheric particle acceleration and X-ray emission of pulsars

The available data on isolated X-ray pulsars, their wind nebulae, and the supernova remnants which are connected to some of these sources are analyzed. It is shown that electric fields of neutron stars tear off charged particles from the surface of neutron star and trigger the acceleration of particles. The charged particles are accelerated mainly in the field of magneto-dipole radiation wave. Power and energy spectra of the charged particles depend on the strength of the magneto-dipole radiation. Therefore, the X-ray radiation is strongly dependent on the rate of rotational energy loss and weakly dependent on the electric field intensity. Coulomb interaction between the charged particles is the main factor for the energy loss and the X-ray spectra of the charged particles.Comment: minor correction on table format, 20 pages (4 figures, 1 table), submitted to International Journal of Modern Physics

Effects of the background radiation on radio pulsar and supernova remnant searches and the birth rates of these objects

In different directions of the Galaxy the Galactic background radio radiation and radiation of complex star formation regions which include large number of OB associations have different influences on radio pulsar (PSR) and supernova remnant (SNR) searches. In this work we analyse the effects of these background radiations on the observations of PSRs at 1400 MHz and SNRs at 1000 MHz. In the interval l=0$^o$$\pm60^o$ the PSRs with flux F$_{1400}$$>$0.2 mJy and the SNRs with surface brightness $\Sigma$$>10^{-21}$ Wm$^{-2}$Hz$^{-1}$sr$^{-1}$ are observable for all values of l and b. All the SNRs with $\Sigma$$>3\times10^{-22}$ Wm$^{-2}$Hz$^{-1}$sr$^{-1}$ can be observed in the interval 60$^o$$<$l$<300^o$. We have examined samples of PSRs and SNRs to estimate the birth rates of these objects in the region up to 3.2 kpc from the Sun and also in the Galaxy. The birth rate of PSRs is about one in 200 years and the birth rate of SNRs is about one in 65 years in our galaxy.Comment: revised versio

Realization and analitical and numerical analysis of a groove type resonator at millimeter waves

Bir yarı-simetrik oyuklu dalga kılavuzu rezonat&ouml;r&uuml; 20 &ndash; 40 GHz frekans bandında kullanılmak &uuml;zere tasarlanmış ve duraleminyum kullanılarak ger&ccedil;eklenmiştir. Rezonat&ouml;r, biri d&uuml;z diğeri ise dairesel oyuk i&ccedil;eren iki plakadan oluşmuştur. Uygun hareketli bir destek sistemine monte edilen rezonat&ouml;r&uuml;n, gerekli &ouml;l&ccedil;&uuml;m d&uuml;zeni de hazırlanarak, frekans spektrumu g&ouml;zlenmiş, rezonans frekansları ve kalite fakt&ouml;r&uuml; &ouml;l&ccedil;&uuml;lm&uuml;şt&uuml;r. Oyuklu rezonat&ouml;r, hem analitik ve hem de sayısal y&ouml;ntemler kullanılarak analiz edilmiştir. Kullanılan sayısal y&ouml;ntem zamanda sonlu farklar (FDTD) y&ouml;ntemidir. &Ouml;l&ccedil;&uuml;m sonucu elde edilen rezonans frekansları, analitik ve sayısal y&ouml;ntemlerden elde edilenlerle karşılaştırılmıştır. Anahtar Kelimeler: Oyuklu dalga kılavuzu, oyuklu rezonat&ouml;r, FDTD, mikrodalga, transfer rezonans metodu.As an alternative to the classical waveguides, such as the H-waveguide and the rectangular waveguide, the Groove waveguide has been used at millimeter wavelengths for the last couple of decades. It has many advantages such as low-loss and higher power handling capacity. Here, in this study, a semi-symmetrical groove guide resonator based on groove waveguide structure is designed and fabricated. Instead of using the classical symmetrical shaped groove guide, a novel semi-symmetrical groove guide structure is presented for the first time. This semi-symmetrical structure was chosen because it is easier to fabricate and excite. The groove resonator which has one grooved plate and one plane plate, first analyzed analytically. Since exact solutions usually exist for idealized geometries, the closed resonator structure is taken into account first. The Green's function method is applied for different oriented line sources. Then the transverse resonance method is used for the open groove resonator. The numerical simulations are performed via the powerful time domain simulator FDTD (Finite Difference Time Domain). Both cartesian and cylindrical coordinate systems are used for FDTD calculations. Here, the purpose to use cylindrical coordinate is to calibrate cartesian coordinates for discretization. Then, a measurement setup which includes a movable support platform was established from 20 GHz to 40 GHz. The resonance frequencies and loaded quality factor are measured. Analitical and numerical results are compared with measurements and a good agreement was observed.Keywords: Groove waveguide, groove resonator, FDTD, microwave, transverse resonance method.

Influences of neutron star parameters on evolutions of different types of pulsar; evolutions of anomalous X-ray pulsars, soft gamma repeaters and dim isolated thermal neutron stars on the P-\.{P} diagram

Influences of the mass, moment of inertia, rotation, absence of stability in the atmosphere and some other parameters of neutron stars on the evolution of pulsars are examined. It is shown that the locations and evolutions of soft gamma repeaters, anomalous X-ray pulsars and other types of pulsar on the period versus period derivative diagram can be explained adopting values of B$<10^{14}$ G for these objects. This approach gives the possibility to explain many properties of different types of pulsar.Comment: 18 pages, 1 figur

Heritage language anxiety and majority language anxiety among Turkish immigrants in the Netherlands

Aims and objectives: This study examines the language anxiety that occurs in immigrants’ daily lives when speaking the heritage language and the majority language, both in their host country and during visits to their home country. It compares the levels of heritage language anxiety and majority language anxiety across three generations of the Turkish immigrant community in the Netherlands and explores the link between immigrants’ language anxiety, and sociobiographical (i.e. generation, gender, education) and language background variables (i.e. age of acquisition, self-perceived proficiency, frequency of language use). Design: A Likert scale-based questionnaire was administered to 116 participants across three generations who reported their language anxiety levels when speaking the heritage language and the majority language in three social contexts (i.e. family, friendship and speaking with native speakers). Findings: Statistical analyses revealed that heritage language anxiety and majority language anxiety were prevalent in immigrants’ daily life, and that levels of both forms of anxiety differed across generations, and in different daily life situations. First- and second-generation immigrants typically experienced majority language anxiety, while second- and predominantly third-generation immigrants suffered from heritage language anxiety. Relationships emerged between language background variables and both forms of anxiety, but only in certain situations. These findings suggest that language background variables on their own may be insufficient to explain immigrant language anxiety in certain social contexts (i.e. within family). Rather than merely language background factors, a variety of other issues within social, cultural and national currents must be considered when examining language anxiety in the immigrant context. Implications: Taking an interdisciplinary approach that combines language contact and foreign language anxiety/second language anxiety research, this study suggests that the concept of foreign language anxiety/second language anxiety should be expanded beyond the confines of the classroom in order to include daily interactions immigrant or minority communities. Originality: This study contributes to the limited body of evidence on the topic of language anxiety in immigrant contexts and presents a new construct ‘majority language anxiety’

Femoral nerve compression secondary to a ganglion cyst arising from a hip joint: a case report and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Femoral nerve compression due to a cystic lesion around the hip joint is rare and only a few cases have been described in the literature. Among these, true ganglion cysts are even more rare.</p> <p>Case presentation</p> <p>We report the case of a 57-year-old woman with femoral nerve compression caused by a true ganglion cyst of the hip joint.</p> <p>Conclusion</p> <p>A high index of suspicion is required to predict a non-palpable cystic lesion around the hip joint as it may mimic different disorders and should be kept in mind in the differential diagnosis of unusual groin pain, radicular pain and peripheral vascular disorders.</p

Lack of association between RNASEL Arg462Gln variant and the risk of breast cancer

Background: The RNASEL G1385A variant was recently found to be implicated in the development of prostate cancer. Considering the function of RNase L and the pleiotropic effects of mutations associated with cancer, we sought to investigate whether the RNASEL G1385A variant is a risk factor for breast cancer. Patients and Methods: A total of 453 breast cancer patients and 382 age- and sex-matched controls from Greece and Turkey were analyzed. Genotyping for the RNASEL G1385A variant was performed using an Amplification Refractory Mutation System (ARMS). Results: Statistical evaluation of the RNASEL G1385A genotype distribution among breast cancer patients and controls revealed no significant association between the presence of the risk genotype and the occurrence of breast cancer. Conclusion: Although an increasing number of studies report an association between the RNASEL G1385A variant and prostate cancer risk, this variant does not appear to be implicated in the development of breast cancer