1,752 research outputs found

    Phonons in MgB2 by Polarized Raman Scattering on Single Crystals

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    The paper presents detailed Raman scattering study of the unusually broad E2g phonon mode in MgB2 crystal. For the first time, it is shown by the polarized Raman scattering on few-micron-size crystallites with natural faces that the observed broad Raman feature really does obey the selection rules of an E2g mode. Raman spectra on high quality polycrystalline superconducting MgB2 wires reveal a very symmetric E2g phonon line near 615 1/cm with the room temperature linewidth of 260 1/cm only. Additional scattering of different polarization dependence, observed in certain crystallites is interpreted as weighted phonon density of states induced by lattice imperfections.Comment: 4 pages + 7 figure

    Preliminary Sunyaev Zel'dovich Observations of Galaxy Clusters with OCRA-p

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    We present 30 GHz Sunyaev Zel'dovich (SZ) observations of a sample of four galaxy clusters with a prototype of the One Centimetre Receiver Array (OCRA-p) which is mounted on the Torun 32-m telescope. The clusters (Cl0016+16, MS0451.6-0305, MS1054.4-0321 and Abell 2218) are popular SZ targets and serve as commissioning observations. All four are detected with clear significance (4-6 sigma) and values for the central temperature decrements are in good agreement with measurements reported in the literature. We believe that systematic effects are successfully suppressed by our observing strategy. The relatively short integration times required to obtain these results demonstrate the power of OCRA-p and its successors for future SZ studies.Comment: 9 pages, 2 figures. Accepted by MNRAS, online earl

    Comparison of numerical and experimental strains distributions in composite panel for aerospace applications

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    In structural applications of aerospace industry, weight efficiency, understood as minimal weight and maximal stiffness, is of great importance. This criterion can be achieved by composite lightweight structures. Typical structures for aforementioned applications are sandwich panels (e.g., with honeycomb core) and stiffened panels (e.g., with blade ribs, T-bar ribs, or hat ribs). In this paper, a hat-stiffened panel, made of carbon/epoxy woven composite, is considered. Results of experiments, consisting of loading the panel and measuring exciting forces and strains (using strain gages), are presented. The results are compared to strains distribution obtained from finite element model of the panel.The research was partially funded from financial resources from the statutory subsidy of the Faculty of Mechanical Engineering, Silesian University of Technology, in 2021. W.M. acknowledges the National Agency for Academic Exchange of Poland (under the Academic International Partnerships program, grant agreement PPI/APM/2018/1/00004) for supporting training in the University of Minho, which enabled execution of the study

    Penerapan Problem Based Learning (Pbl) Dengan Penilaian Portofolio Untuk Meningkatkan Keaktifan Dan Prestasi Belajar Pada Materi Stoikiometri Di SMA N 2 Surakarta Tahun Ajaran 2013/2014

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    Penelitian ini bertujuan untuk meningkatkan: 1). keaktifan belajar siswa kelas X IPA 5 pada materi konsep mol dan perhitungan kimia di SMA Negeri 2 Surakarta Tahun Ajaran 2013/2014, 2). prestasi belajar siswa kelas X IPA 5 pada materi konsep mol dan perhitungan kimia di SMA Negeri 2 Surakarta Tahun Ajaran 2013/2014. Penelitian ini merupakan Penelitian Tindakan Kelas (PTK) yang terdiri dari dua siklus. Setiap siklus terdapat empat tahapan yang terdiri dari perencanaan tindakan, pelaksanaan tindakan, observasi, refleksi. Subyek penelitian adalah siswa kelas X IPA 5 SMA Negeri 2 Surakarta Tahun Ajaran 2013/2014 yang berjumlah 32 siswa. Sumber data berasal dari guru, dan siswa. Data penelitian yang diperoleh berupa keaktifan siswa (visual activities, oral activities, listening activities, dan writing activities) dan prestasi belajar (aspek kognitif dan aspek sikap). Pengumpulan data adalah dengan metode tes (tertulis) dan non tes (observasi, wawancara, kajian dokumen, angket). Teknik analisis data penelitian secara deskriptif kualitataif dan kuantitatif. Berdasarkan hasil dari penelitian yang telah dilakukan, maka dapat diambil kesimpulan sebagai berikut: 1). penerapan model Problem Based Learning (PBL) dengan penilaian portofolio dapat meningkatkan keaktifan belajar siswa X IPA 5 pada materi konsep mol dan perhitungan kimia di SMA Negeri 2 Surakarta Tahun Ajaran 2013/2014. Persentase rata-rata nilai akhir keaktifan siswa siklus I dalam pembelajaran adalah 73,65 % meningkat menjadi 74,40 % pada siklus II, 2). penerapan model Problem Based Learning (PBL) dengan penilaian portofolio dapat meningkatkan prestasi belajar siswa X IPA 5 pada materi konsep mol dan perhitungan kimia di SMA Negeri 2 Surakarta Tahun Ajaran 2013/2014. Persentase rata-rata nilai akhir prestasi belajar siswa siklus I adalah 87,98 % meningkat menjadi 90,34 % pada siklus II dengan jumlah siswa tuntas sebanyak 32 siswa (100 %). Persentase rata-rata nilai akhir aspek sikap siswa pada siklus I adalah 70,99 % meningkat menjadi 75,7 % pada siklus II

    A progressive diagonalization scheme for the Rabi Hamiltonian

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    A diagonalization scheme for the Rabi Hamiltonian, which describes a qubit interacting with a single-mode radiation field via a dipole interaction, is proposed. It is shown that the Rabi Hamiltonian can be solved almost exactly using a progressive scheme that involves a finite set of one variable polynomial equations. The scheme is especially efficient for lower part of the spectrum. Some low-lying energy levels of the model with several sets of parameters are calculated and compared to those provided by the recently proposed generalized rotating-wave approximation and full matrix diagonalization.Comment: 8pages, 1 figure, LaTeX. Accepted for publication in J. Phys. B: At. Mol. Opt. Phy
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