Tunable fast and slow light in a hybrid optomechanical system

We explain the probe field transmission spectrum under the influence of a strong pump field in a hybrid optomechanical system, composed of an optical cavity, a mechanical resonator, and a two-level atom. We show fast (superluminal) and slow (subluminal) light effects of the transmitted probe field in the hybrid system for suitable parametric regimes. For the experimental accessible domain, we find that the fast light effect obtained for the single optomechanical coupling can further be enhanced with the additional atom-field coupling in the hybrid system. Furthermore, we report the existence of a tunable switch from fast to slow light by adjusting the atomic detuning with the anti-Stokes and Stokes sidebands, respectively, as $\Delta_a=+\omega_m$ and $-\omega_m$. The reported characteristics are realizable in state-of-the-art laboratory experiments.Comment: 9 pages, 7 figures, typos corrected, figure and references added, we have also clarified some points, published versio

A disaster-resilient multi-content optical datacenter network architecture

Cloud services based on datacenter networks are becoming very important. Optical networks are well suited to meet the demands set by the high volume of traffic between datacenters, given their high bandwidth and low-latency characteristics. In such networks, path protection against network failures is generally ensured by providing a backup path to the same destination, which is link-disjoint to the primary path. This protection fails to protect against disasters covering an area which disrupts both primary and backup resources. Also, content/service protection is a fundamental problem in datacenter networks, as the failure of a single datacenter should not cause the disappearance of a specific content/service from the network. Content placement, routing and protection of paths and content are closely related to one another, so the interaction among these should be studied together. In this work, we propose an integrated ILP formulation to design an optical datacenter network, which solves all the above-mentioned problems simultaneously. We show that our disaster protection scheme exploiting anycasting provides more protection, but uses less capacity, than dedicated single-link protection. We also show that a reasonable number of datacenters and selective content replicas with intelligent network design can provide survivability to disasters while supporting user demands

PENGARUH PENDEKATAN BERMAIN TERHADAP MOTIVASI SISWA DALAM PEMBELAJARAN AKTIVITAS BERLARI SPRINT

Latar belakang masalah pada penelitian ini adalah rendahnya motivasi belajar siswa kelas VII A MTs. Al-Hidayah Cukangkawung dalam mengikuti aktivitas pembelajaran aktivitas lari jarak pendek (sprint), sebagai akibat kurang pahamnya fungsi lari jarak pendek. Adapun faktor lain yang dapat mempengaruhi siswa tidak mau atau kurang termotivasi dalam pembelajaran lari jarak pendek adalah kurangnya pengetahuan guru tentang metode pembelajaran yang dapat meningkatkan motivasi siswa. Oleh karena itu untuk meningkatkan motivasi belajar siswa maka peneliti akan menerapkan pendekatan bermain. Tujuan penelitian ini adalah untuk meningkatkan motivasi belajar siswa di dalam pembelajaran aktivitas berlari sprint. Oleh karena ini masalah penelitian yang akan dipecahkan dengan penggunaan atau penerapan pendekatan bermain adalah untuk meningkatkan motivasi siswa. Untuk meningkatkan motivasi belajar siswa peneliti menerapkan: teknik motivasi belajar siswa, dan menerapkan pendekatan bermain. Metode yang peneliti gunakan ialah penelitian tindakan kelas (PTK) dengan menggunakan dua siklus. Subjek dalam penelitian ini ialah siswa kelas VII A MTs. Al-Hidayah Cukangkawung yang berjumlah 38 siswa, 18 siswa putri dan 20 siswa putra. Instrument yang digunakan dalam penelitian ini adalah instrument motivasi belajar aktivitas lari sprint yang berupa angket, observasi, dan wawancara. Hasil penelitian menunjukan bahwa motivasi meningkat dari prasiklus yang hanya 96, siklus I 127, dan siklus yang ke II 143 Berdasarkan hasil pengolahan dan analisis data, diketahui bahwa adanya peningkatan motivasi siswa dalam pembelajaran aktivitas berlari sprint. ;---The background of this research is the lack motivation of class 7 A students at MTs. Al-Hidayah Cukangkawung on participate the sprint subject, as the result is less fngtion understanding of athletic. There is also another factor that affected student motivation on sprint subject. It is the teacher lack knowledge the method of teaching to increase the students motivation. Because of it to increase the students learning motivation then the research will improve approachment game. The aim of this research is to improve student motivation on sprint activity. As the research question will be done using game approachment to improve student motivation. To increase students learning motivation the research will be using: the technic student motivation, and improve approachment game. The research method is using Action Research with two cycles. Sample of this research is students from class 7A at MTs. Al-Hidayah Cukangkawung. There are 38 students, 18 of them are girls, and the other 20 are boys. Instrument used in this research is learning motivation instrument of sprint activity which are questioner, observation, and interview. The result of the questioner on pre-cycle is 96, first cycle is 127, and second cycle is 143. According the analyzed and tabulated data, there is an improvement in student motivation on learning sprint activity

The strength of nuclear shell effects at N=126 in the r-process region

We have investigated nuclear shell effects across the magic number N=126 in the region of the r-process path. Microscopic calculations have been performed using the relativistic Hartree-Bogoliubov approach within the framework of the RMF theory for isotopic chains of rare-earth nuclei in the r-process region. The Lagrangian model NL-SV1 with the inclusion of the vector self-coupling of omega meson has been employed. The RMF results show that the shell effects at N=126 remain strong and exhibit only a slight reduction in the strength in going from the r-process path to the neutron drip line. This is in striking contrast to a systematic weakening of the shell effects at N=82 in the r-process region predicted earlier in the similar approach. In comparison the shell effects with microscopic-macroscopic mass formulae show a near constancy of shell gaps leading to strong shell effects in the region of r-process path to the drip line. A recent analysis of solar-system r-process abundances in a prompt supernova explosion model using various mass formulae including the recently introduced mass tables based upon HFB approach shows that whilst mass formulae with weak shell effects at N=126 give rise to a spread and an overproduction of nuclides near the third abundance peak at A~190, mass tables with droplet models showing stronger shell effects are able to reproduce the abundance features near the third peak appropriately. In comparison, several analyses of the second r-process peak at A~130 have required weakened shell effects at N=82. Our predictions in the RMF theory with NL-SV1, which exhibit weaker shell effects at N=82 and stronger one at N=126 in the r-process region, support the conjecture that a different nature of the shell effects at the magic numbers may be at play in r-process nucleosynthesis of heavy nuclei.Comment: 14 pages, 8 figures; submitted to Physical Review C. Part of this work was presented at Nuclear Physics in Astrophysics II, 20th International Nuclear Physics Divisional Conference of the European Physical Society, at Debrecen, Hungary, May 16-20, 200