Does Sub-millisecond Pulsar XTE J1739-285 Contain a Low Magnetic Neutron Star or Quark Star ?

With the possible detection of the fastest spinning nuclear-powered pulsar XTE J1739-285 of frequency 1122 Hz (0.8913 ms), it arouses us to constrain the mass and radius of its central compact object and to imply the stellar matter compositions: neutrons or quarks. Spun-up by the accreting materials to such a high rotating speed, the compact star should have either a small radius or short innermost stable circular orbit. By the empirical relation between the upper kHz quasi-periodic oscillation frequency and star spin frequency, a strong constraint on mass and radius is obtained as 1.51 solar masses and 10.9 km, which excludes most equations of states (EOSs) of normal neutrons and strongly hints the star promisingly to be a strange quark star. Furthermore, the star magnetic field is estimated to be about $4\times10^{7} (G) < B < 10^{9} (G)$, which reconciles with those of millisecond radio pulsars, revealing the clues of the evolution linkage of two types of astrophysical objects.Comment: 10 pages, 2 figures, accepted by PASP 200

Thermo-magnetic history effects in the vortex state of YNi_2B_2C superconductor

The nature of five-quadrant magnetic isotherms for is different from that for in a single crystal of YNi2B2C, pointing towards an anisotropic behaviour of the flux line lattice (FLL). For, a well defined peak effect (PE) and second magnetization peak (SMP) can be observed and the loop is open prior to the PE. However, for, the loop is closed and one can observe only the PE. We have investigated the history dependence of magnetization hysteresis data for by recording minor hysteresis loops. The observed history dependence in across different anomalous regions are rationalized on the basis of su-perheating/supercooling of the vortex matter across the first-order-like phase transition and possible additional effects due to annealing of the disordered vortex bundles to the underlying equilibrium state.Comment: 4 pages, 4 figure

Sürekli Sistem Olarak Modellenen Yarı-Rijit Mesnetli Tek Katlı Çerçevelerin Tepki Spektrumları

DergiPark: 245930trakyafbdÇerçevelerin dinamik analizinde, ankastre bağlı oldukları ve kolonlarının kütle ve deformasyonunun ihmal edildiği kabulleri sıkça yapılır. Ancak gerçekte, çerçeve kolonlarının temele bağlı noktaları sismik etkiler sebebiyle ötelenme ve dönme gösterebilmektedir. Bu durumda, mesnet davranışı elastik yaylarıyla modellenebilir. Ayrıca, gerçekte kolonlar yayılı kütleye ve rijitliğe sahiptir. Bu çalışmada, Timoshenko kolonu olarak modellenen çerçevenin mesnedi ötelenmeye ve dönmeye karşı elastik yaylar ile modellenmiştir. Genelleştirilmiş hareket denklemi sistemin enerji ifadeleri kullanılarak Lagrange denklemi ile elde edilmiş, Newmark-? metodu kullanılarak sistemin dinamik tepkisi hesaplanmış ve 1999 İzmit depremi yer ivmeleri kullanılarak tepki spektrumları elde edilmiştirThe assumptions of frame supports being fully rigid and distributed masses and deformations of the columns being neglected are frequently taken into consideration in dynamic analysis of plane frames. In practice, however, column bases of frames may usually rotate and translate a little due to seismic effects. In this case, support behavior can be modeled using elastic springs at the column bases of frames. Besides, columns, in fact, are not massless, and have distributed mass and stiffness. In this study, the support of the frame modeled as Timoshenko column is modeled by elastic springs against rotation and translation. The generalized equation of motion is obtained by Lagrange equation using energy relations of the system, the dynaimc response is computed for different elastic spring coefficients using incremental Newmark-? method, and response spectra are obtained using ground accelerations of 1999 Izmit earthquak

Meaningful CSR Communication via Digital Media

It has regularly been stated that consumer demand for CSR is larger than ever, but do consumers really want to be informed about the ethical behaviour of brands? Does digital media have an impact on meaningful CSR communication? A research analysing consumer reaction to social media posts about CSR is limited. Using mixed method, this study examined the UK consumer attitudes towards CSR and its communication in digital media plus its consequent effect on purchasing intentions. Results indicate that consumers are more likely to evaluate a brand higher if made aware of CSR activity, which in turn affects purchase intention. Consumers have fairly positive attitudes about CSR communicated on digital media, but may react negatively if the message contradicts prior behaviour of the brand. Overall, the study show support for the communication of digital media but brands looking to enhance a damaged reputation must take great consideration over the message at hand

Dirhenium Carbonyl Complexes Bearing 2-Vinylpyridine, Morpholine and 1-Methylimidazole Ligands

Treatment of the labile compound [Re2(CO)8(MeCN)2] with 2-vinylpyridine in refluxing benzene affords exclusively the new compound [Re2(CO)8(μ-η1:η2-NC5H4CHCH2)] (1) in 39% yield in which the μ-η1:η2-vinylpyridine ligand is coordinated to one Re atom through the nitrogen and to the other Re atom via the olefinic double bond. Reaction of [Re2(CO)8(MeCN)2] with morpholine in refluxing benzene furnishes two compounds, [Re2(CO)9(η1-NC4H9O)] (2) and [Re2(CO)8(η1-NC4H9O)2] (3) in 5% and 29% yields, respectively. Reaction of [Re2(CO)8(MeCN)2] with 1-methylimidazole gives [Re2(CO)8{η1-NC3H3N(CH3)}2] (4) and the mononuclear compound fac-[ReCl(CO)3{η1-NC3H3N(CH3)}2] (5) in 18% and 26% yields, respectively. In the disubstituted compounds 2 and 4, the heterocyclic ligands occupy equatorial coordination sites. The mononuclear compound 5 consists of three CO groups, two N coordinated η1-1-methylimidazole ligands and a terminal Cl ligand. The XRD structures of complexes 1, 3 and 5 are reported

LabVIEW kullanarak asenkron motorlar clarke-park dönüşümleri için grafik kullanıcı arayüzü

Before any electrical system is used in industrial applications, its behavior under different operating conditions must be studied. A mathematical model must be constructed beforehand in order to observe the behavior of the system under different conditions. Modeling of three-phase asynchronous motors with an electromechanical converter is very difficult due to the time varying current and voltage. While performing dynamic analysis of such motors, a common reference system must be determined. The most commonly used methods to facilitate the analysis of three-phase induction motors are Clarke-Park transforms. In this study, a visual interface has been prepared to ease the teaching of Clarke-Park transforms. The users are moved from the 3-phase (A,B,C) axis to the reference 2 phase (α,β) axis through the interface and to the (d,q) axis with the θ angle at the magnitudes defined in the (α,β) axis system. With the interface prepared, users can change the voltage, frequency and angle values and graphically observe their effect on Clarke and Park transforms. In addition, the conversion from 2-phase axis to 3-phase axis is made with inverse Clarke and Park transforms. Mathematical modeling of the transform and the interface were made using LabVIEW.Herhangi bir elektriksel sistem, endüstriyel uygulamalarda kullanılmadan önce farklı çalışma koşulları altında davranışlarının incelenmesi gerekmektedir. Sistemin farklı koşullarda davranışlarının gözlemlenebilmesi için öncelikle matematiksel modeli oluşturulmalıdır. Bir elektromekanik dönüştürücü olan üç fazlı asenkron motorların zamanla değişen akım ve gerilim ifadesinden dolayı modellenmesi oldukça zordur. Bu tarz motorların dinamik analizi yapılırken ortak bir referans sistem belirlenmesi gerekmektedir. Üç fazlı asenkron motorların analizini kolaylaştırmak için en çok kullanılan yöntemler Clarke ve Park dönüşümleridir. Bu çalışmada Clarke ve Park dönüşümlerinin öğretilmesi amacıyla görsel bir arayüz hazırlanmıştır. Kullanıcılar arayüz aracılığıyla 3 fazlı (A,B,C) eksenden referans 2 faz (α,β) eksene ve (α,β) eksen sisteminde tanımlanmış büyüklüklerde θ açısıyla (d,q) eksenine taşınmaktadır. Hazırlanan arayüz ile kullanıcılar gerilim, frekans ve açı değerlerini değiştirerek bunların Clarke ve Park dönüşümleri üzerine olan etkisini grafiksel olarak gözlemleyebilmektedir. Ayrıca ters Clarke ve Park dönüşümleriyle 2 fazlı eksenden 3 fazlı eksene dönüşüm yapılmaktadır. Dönüşümün matematiksel modellenmesi ve arayüz LabVIEW programı kullanılarak yapılmıştır

Energy spectrum, density of states and optical transitions in strongly biased narrow-gap quantum wells

We study theoretically the effect of an electric field on the electron states and far-infrared optical properties in narrow-gap lead salt quantum wells. The electron states are described by a two-band Hamiltonian. An application of a strong electric field across the well allows the control of the energy gap between the two-dimensional (2D) states in a wide range. A sufficiently strong electric field transforms the narrow-gap quantum well to a nearly gapless 2D system, whose electron energy spectrum is described by linear dispersion relations \epsilon_{\sigma} (k) ~\pm (k-k_{\sigma}), where k_{\sigma} are the field-dependent 2D momenta corresponding to the minimum energy gaps for the states with spin numbers \sigma. Due to the field-induced shift of the 2D subband extrema away from k=0 the density of states has inverse-square-root divergencies at the edges. This property may result in a considerable increase of the magnitude of the optical absorption and in the efficiency of the electrooptical effect.Comment: Text 18 pages in Latex/Revtex format, 7 Postscript figure

Design and Performance Evaluation of a Mixed-Mode Solar Crop Dryer

This study is concerned with development and performance evaluation of a mixed-mode solar  yam dryer. It was done to address the problems of uneven drying of product on different trays coordinate position in a typical indirect multiple trays dryer. Solar energy drying system was designed using the meteorological conditions of Zaria, Nigeria to dry yam slices in the mixed-mode natural convection. The dryer was designed to dry (7 kg) of yam slices. The dimensions of the dryer were: collector length, collector area, height of the drying chamber, chimney height, length of the drying chamber, and Width of the drying chamber were 0.65 m, 0.27 m2, 0.9 m, 0.7 m, 0.5 m, and 0.43 m, respectively. The solar yam dryer was exposed to solar radiation from 10:00 am to 06:00 pm and tested without load and with yam chips of 5 mm average thickness. Meteorological conditions were monitored during the dehydration process. The average drying rate, collector efficiency and drying efficiency were 2.55 kg/s, 42.20% and 25.35%, respectively. The results of performance evaluation of the solar dryer showed that the drying rate decreases by 3% and 8% in the second and third trays relative to the first tray. This shows that the drying rates did not vary significantly with the coordinate positions of the trays