ANALISA PERLAKUAN ARTIFICIAL AGING TERHADAP KERATAAN PERMUKAAN PADA MATERIAL KOMPOSIT Al-ABU DASAR BATUBARA

Abstrak Komposit merupakan gabungan dua bahan atau lebih, yang menghasilkan sifat baru yang berbeda dari matriknya, salah satu material komposit matrik logam adalah Aluminium-Abu Dasar Batubara. Pada penggunaannya sebagai piringan cakram mendapatkan panas yang akan mengakibatkan distorsi sehingga dapat mengakibatkan perubahan bentuk Untuk memperbaiki sifat fisik dan mekanik material, maka perlu dilakukan perlakuan panas pada material. Untuk komposit bermatrik aluminium, perlakuan panas yang digunakan adalah perlakuan panas artificial aging T6.Dalam penelitian ini akan dilakukan perlakuan panas dengan temperatur pelarutan pada 540oC dengan waktu tahan 6 jam. Kemudian dilakukan penuaan buatan dengan variasi temperatur 160oC, 180oC, dan 200oC serta variasi waktu tahan 2, 4, dan 6 jam. Kemudian dilakukan analisa terhadap kerataan permukaan. Setelah dilakukan pengujian kerataan permukaan, maka diperoleh angka ketidak rataan tertinggi pada spesimen F dengan nilai rata-rata -6,4x 10-2 mm, pada temperatur 180oC dengan waktu penahanan 4 jam. Dan diperoleh angka  ketidak rataan terendah pada spesimen D dengan nilai rata-rata 0,0 x 10-2 mm, pada temperatur 180oC dengan waktu penahanan 2 jam. Kata kunci: Artificial Aging, Aluminium, Abu Dasar Batubara, Kerataan Permukaa

The New Views as to the Morphology of the Thymus Gland and Their Bearing on the Problem of the Function of the Thymus

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Revisiting the Problem of Searching on a Line

We revisit the problem of searching for a target at an unknown location on a line when given upper and lower bounds on the distance D that separates the initial position of the searcher from the target. Prior to this work, only asymptotic bounds were known for the optimal competitive ratio achievable by any search strategy in the worst case. We present the first tight bounds on the exact optimal competitive ratio achievable, parameterized in terms of the given bounds on D, along with an optimal search strategy that achieves this competitive ratio. We prove that this optimal strategy is unique. We characterize the conditions under which an optimal strategy can be computed exactly and, when it cannot, we explain how numerical methods can be used efficiently. In addition, we answer several related open questions, including the maximal reach problem, and we discuss how to generalize these results to m rays, for any m >= 2

Diffuse transport and spin accumulation in a Rashba two-dimensional electron gas

The Rashba Hamiltonian describes the splitting of the conduction band as a result of spin-orbit coupling in the presence of an asymmetric confinement potential and is commonly used to model the electronic structure of confined narrow-gap semiconductors. Due to the mixing of spin states some care has to be exercised in the calculation of transport properties. We derive the diffusive conductance tensor for a disordered two-dimensional electron gas with spin-orbit interaction and show that the applied bias induces a spin accumulation, but that the electric current is not spin-polarized.Comment: REVTeX4 format, 5 page

Optical Designs for a Multi-Beam 340 and 625/640 GHz Spaceborne Climate Research Instrument

We report on an ongoing study where different optical configurations for a multi-beam limb-viewing (four to eight receiver channels at 340 and two channels at 625 GHz) spaceborne instrument for climate research are presented and compared. The optical configurations are analyzed in terms of optical performance (gain, side lobe levels, beam efficiency etc.), weight and size of the overall instrument envelope. Using ideal fundamental Gaussian beam modes and numerical tools relying on ray-tracing and physical optics methods, the different configurations are designed and evaluated. Preliminary results indicate that a 1.3 m x 0.65 m primary reflector can be used in a configuration that includes a relay optics system having two to four elements. In addition to the limb-viewing instrument, there will be an additional instrument operating at 640 GHz for observing clouds in nadir mode

Ballistic spin-polarized transport and Rashba spin precession in semiconductor nanowires

We present numerical calculations of the ballistic spin-transport properties of quasi-one-dimensional wires in the presence of the spin-orbit (Rashba) interaction. A tight-binding analog of the Rashba Hamiltonian which models the Rashba effect is used. By varying the robustness of the Rashba coupling and the width of the wire, weak and strong coupling regimes are identified. Perfect electron spin-modulation is found for the former regime, regardless of the incident Fermi energy and mode number. In the latter however, the spin-conductance has a strong energy dependence due to a nontrivial subband intermixing induced by the strong Rashba coupling. This would imply a strong suppression of the spin-modulation at higher temperatures and source-drain voltages. The results may be of relevance for the implementation of quasi-one-dimensional spin transistor devices.Comment: 19 pages (incl. 9 figures). To be published in PR

Critical properties of S=1/2 Heisenberg ladders in magnetic fields

The critical properties of the $S=1/2$ Heisenberg two-leg ladders are investigated in a magnetic field. Combining the exact diagonalization method and the finite-size-scaling analysis based on conformal field theory, we calculate the critical exponents of spin correlation functions numerically. For a strong interchain coupling, magnetization dependence of the critical exponents shows characteristic behavior depending on the sign of the interchain coupling. We also calculate the critical exponents for the $S=1/2$ Heisenberg two-leg ladder with a diagonal interaction, which is thought as a model Hamiltonian of the organic spin ladder compound ${Cu}_2({1,4-diazacycloheptane})_2{Cl}_4$. Numerical results are compared with experimental results of temperature dependence of the NMR relaxation rate $1/T_1$.Comment: REVTeX, 10 pages, 8 figures, accepted for Phys. Rev.

Observation of Field-Induced Transverse N\'{e}el Ordering in the Spin Gap System TlCuCl3_3

Neutron elastic scattering experiments have been performed on the spin gap system TlCuCl$_3$ in magnetic fields parallel to the $b$-axis. The magnetic Bragg peaks which indicate the field-induced N\'{e}el ordering were observed for magnetic field higher than the gap field $H_{\rm g}\approx 5.5$ T at $Q=(h, 0, l)$ with odd $l$ in the $a^*-c^*$ plane. The spin structure in the ordered phase was determined. The temperature and field dependence of the Bragg peak intensities and the phase boundary obtained were discussed in connection with a recent theory which describes the field-induced N\'{e}el ordering as a Bose-Einstein condensation of magnons.Comment: 4 pages, 5 eps figures, jpsj styl

Nursing assistants matters—An ethnographic study of knowledge sharing in interprofessional practice

© 2017 John Wiley & Sons Ltd Interprofessional collaboration involves some kind of knowledge sharing, which is essential and will be important in the future in regard to the opportunities and challenges in practices for delivering safe and effective health care. Nursing assistants are seldom mentioned as a group of health care workers that contribute to interprofessional collaboration in health care practice. The aim of this ethnographic study was to explore how the nursing assistants’ knowledge can be shared in a team on a spinal cord injury rehabilitation ward. Using a sociomaterial perspective on practice, we captured different aspects of interprofessional collaboration in health care. The findings reveal how knowledge was shared between professionals, depending on different kinds of practice architecture. These specific cultural–discursive, material–economic, and social–political arrangements enabled possibilities through which nursing assistants’ knowledge informed other practices, and others’ knowledge informed the practice of nursing assistants. By studying what health care professionals actually do and say in practice, we found that the nursing assistants could make a valuable contribution of knowledge to the team