967 research outputs found
Experimental and theoretical investigation of passive damping concepts for member forced and free vibration
Potential passive damping concepts for use in space structures are identified. The effectiveness of copper brush, wool swab, and silly putty in chamber dampers is investigated through natural vibration tests on a tubular aluminum member. The member ends have zero translation and possess partial rotational restraints. The silly putty in chamber dampers provide the maximum passive damping efficiency. Forced vibration tests are then conducted with one, two, and three damper chambers containing silly putty. Owing to the limitation of the vibrator used, the performance of these dampers could not be evaluated experimentally until the forcing function was disengaged. Nevertheless, their performance is evaluated through a forced dynamic finite element analysis conducted as a part of this investigation. The theoretical results based on experimentally obtained damping ratios indicate that the passive dampers are considerably more effective under member natural vibration than during forced vibration. Also, the maximum damping under forced vibration occurs at or near resonance
Comment on `Renormalization-Group Calculation of the Dependence on Gravity of the Surface Tension and Bending Rigidity of a Fluid Interface'
It is shown that the interface model introduced in Phys. Rev. Lett. 86, 2369
(2001) violates fundamental symmetry requirements for vanishing gravitational
acceleration , so that its results cannot be applied to critical properties
of interfaces for .Comment: A Comment on a recent Letter by J.G. Segovia-L\'opez and V.
Romero-Roch\'{\i}n, Phys. Rev. Lett.86, 2369 (2001). Latex file, 1 page
(revtex
Penerapan Sistem Monitoring Terapi Arv(antiretroviral) dengan Metode Client Server Berbasis Smartphone pada Rsup Dr. Sardjito
AIDS (Acquired Immune Deficiency Syndrome) adalah salah satu penyakit yang menyita perhatian yang besar dalam dunia medis. AIDS merupakan suatu penyakit yang berupa sekumpulan gejala dan infeksi atau sindrom yang ditimbulkan oleh rusaknya sistem kekebalan tubuh manusia akibat infeksi virus HIV (Human Immunodeficiency Virus). Penangan penyakit AIDS dalam dunia medis adalah dengan terapi pengobatan ARV. Dalam menjalankan terapi ARV harus meminum obat harus disiplin ketat dan terus menerus seumur hidup ODHA(Orang Dengan HIV / AIDS) untuk menghambat replikasi virus HIV, namun dalam Kenyataanya banyak pasien penyakit AIDS yang tidak mendapatkan hasil yang optimal dalam menalankan terapi HIV, karena kurangnya tingkat kepatuhan pasien dalam mengkonsumsi obat dalam menjalani terapi ARV. Subjek yang menjadi penelitian ini adalah penerapan sistem monitoring untuk pemantauan pelaksanaan terapi pengobatan ARV. Metode penelitian yang digunakan dengan studi pustaka dan wawancara dengan petugas klinik pengobatan HIV/AIDS. Tahap analisis dilakukan untuk menentukan spesifikasi sistem monitoring agar sesuai dengan kebutuhan. Tahap analisis meliputi perancangan sistem, perancangan database dan perancangan antarmuka. Metode yang digunakan pada tahap implementasi adalah client server, dimana aplikasi server dikembangkan menggunakan PHP dengan Framework Codeigniter, sedangkan aplikasi client menggunakan bahasa pemrograman JAVA untuk mengembangankan aplikasi berbasis smartphone Android. Sistem yang dihasilkan diuji dengan dua metode yaitu Black Box Test dan Alfa Test.Hasil dari penelitian ini adalah sebuah sistem monitoring yang terdiri dari aplikasi server berbasis web dan aplikasi client berbasis Android yang dapat membantu proses pemantauan kepatuhan dan pemantauan pekembangan CD4 pasien HIV/AIDS ARV untuk mensukseskan pelaksanaan terapi ARV
Modeling hydrodynamic self-propulsion with Stokesian Dynamics. Or teaching Stokesian Dynamics to swim
We develop a general framework for modeling the hydrodynamic self-propulsion (i.e., swimming) of bodies (e.g., microorganisms) at low Reynolds number via Stokesian Dynamics simulations. The swimming body is composed of many spherical particles constrained to form an assembly that
deforms via relative motion of its constituent particles. The resistance tensor describing the hydrodynamic interactions among the individual particles maps directly onto that for the assembly. Specifying a particular swimming gait and imposing the condition that the swimming body is force- and torque-free determine the propulsive speed. The body’s translational and rotational
velocities computed via this methodology are identical in form to that from the classical theory for the swimming of arbitrary bodies at low Reynolds number. We illustrate the generality of the method through simulations of a wide array of swimming bodies: pushers and pullers, spinners, the
Taylor=Purcell swimming toroid, Taylor’s helical swimmer, Purcell’s three-link swimmer, and an amoeba-like body undergoing large-scale deformation. An open source code is a part of the supplementary material and can be used to simulate the swimming of a body with arbitrary geometry and swimming gait
Solver and Turbulence Model Upgrades to OVERFLOW 2 for Unsteady and High-Speed Applications
An implicit unfactored SSOR algorithm has been added to the overset Navier-Stokes CFD code OVERFLOW 2 for unsteady and moving body applications. The HLLEM and HLLC third-order spatial upwind convective flux models have been added for high-speed flow applications. A generalized upwind transport equation has been added for solution of the two-equation turbulence models and the species equations. The generalized transport equation is solved using an unfactored SSOR implicit algorithm. Three hybrid RANS/DES turbulence models have been added for unsteady flow applications. Wall function boundary conditions that include compressibility and heat transfer effects have been also been added to OVERFLOW 2
Spurious phase in a model for traffic on a bridge
We present high-precision Monte Carlo data for the phase diagram of a
two-species driven diffusive system, reminiscent of traffic across a narrow
bridge. Earlier studies reported two phases with broken symmetry; the existence
of one of these has been the subject of some debate. We show that the disputed
phase disappears for sufficiently large systems and/or sufficiently low bulk
mobility.Comment: 8 pages, 3 figures, JPA styl
Gas permeation through a polymer network
We study the diffusion of gas molecules through a two-dimensional network of
polymers with the help of Monte Carlo simulations. The polymers are modeled as
non-interacting random walks on the bonds of a two-dimensional square lattice,
while the gas particles occupy the lattice cells. When a particle attempts to
jump to a nearest-neighbor empty cell, it has to overcome an energy barrier
which is determined by the number of polymer segments on the bond separating
the two cells. We investigate the gas current as a function of the mean
segment density , the polymer length and the probability
for hopping across segments. Whereas decreases monotonically with
for fixed , its behavior for fixed and increasing
depends strongly on . For small, non-zero , appears to increase
slowly with . In contrast, for , it is dominated by the underlying
percolation problem and can be non-monotonic. We provide heuristic arguments to
put these interesting phenomena into context.Comment: Dedicated to Lothar Schaefer on the occasion of his 60th birthday. 11
pages, 3 figure
Methyl 2-methyl-4-(oxiran-2-ylmethoxy)-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide
In the title compound, C14H15NO6S, the thiazine ring adopts a distorted half-chair conformation. The structure displays several cooperative weak intermolecular C—H⋯O hydrogen-bonding interactions, giving rise to a two-dimensional sheet packing motif. The CH2 group in the methoxy linker to the oxirane ring, and the CH group in that ring, exhibit twofold positional disorder. The three-membered oxirane ring is twisted approximately perpendicular with respect to thiazine ring (dihedral angle = 60/86° for the major/minor disorder components). 1,2-Benzothiazines of this kind have a wide range of biological activities and are mainly used as medicines in the treatment of inflammation and rheumatoid arthritis
Will jams get worse when slow cars move over?
Motivated by an analogy with traffic, we simulate two species of particles
(`vehicles'), moving stochastically in opposite directions on a two-lane ring
road. Each species prefers one lane over the other, controlled by a parameter
such that corresponds to random lane choice and
to perfect `laning'. We find that the system displays one large cluster (`jam')
whose size increases with , contrary to intuition. Even more remarkably, the
lane `charge' (a measure for the number of particles in their preferred lane)
exhibits a region of negative response: even though vehicles experience a
stronger preference for the `right' lane, more of them find themselves in the
`wrong' one! For very close to 1, a sharp transition restores a homogeneous
state. Various characteristics of the system are computed analytically, in good
agreement with simulation data.Comment: 7 pages, 3 figures; to appear in Europhysics Letters (2005
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