Center for low-gravity fluid mechanics and transport phenomena

Research projects in several areas are discussed. Mass transport in vapor phase systems, droplet collisions and coalescence in microgravity, and rapid solidification of undercooled melts are discussed

Numerical Approaches to Spacetime Singularities

This Living Review updates a previous version which its itself an update of a review article. Numerical exploration of the properties of singularities could, in principle, yield detailed understanding of their nature in physically realistic cases. Examples of numerical investigations into the formation of naked singularities, critical behavior in collapse, passage through the Cauchy horizon, chaos of the Mixmaster singularity, and singularities in spatially inhomogeneous cosmologies are discussed.Comment: 51 pages, 6 figures may be found in online version: Living Rev. Relativity 2002-1 at www.livingreviews.or

Counterions and water molecules in charged silicon nanochannels: the influence of surface charge discreteness

In order to detect the effect of the surface charge discreteness on the properties at the solid-liquid interface, molecular dynamics simulation model taking consideration of the vibration of wall atoms was used to investigate the ion and water performance under different charge distributions. Through the comparison between simulation results and the theoretical prediction, it was found that, with the degree of discreteness increasing, much more counterions were attracted to the surface. These ions formed a denser accumulating layer which located much nearer to the surface and caused charge inversion. The ions in this layer were non-hydrated or partially hydrated. When a voltage was applied across the nanochannel, this dense accumulating layer did not move unlike the ions near uniformly charged surface. From the water density profiles obtained in nanochannels with different surface charge distributions, the influence of the surface charge discreteness on the water distributions could be neglected

Research and Education in Computational Science and Engineering

Over the past two decades the field of computational science and engineering (CSE) has penetrated both basic and applied research in academia, industry, and laboratories to advance discovery, optimize systems, support decision-makers, and educate the scientific and engineering workforce. Informed by centuries of theory and experiment, CSE performs computational experiments to answer questions that neither theory nor experiment alone is equipped to answer. CSE provides scientists and engineers of all persuasions with algorithmic inventions and software systems that transcend disciplines and scales. Carried on a wave of digital technology, CSE brings the power of parallelism to bear on troves of data. Mathematics-based advanced computing has become a prevalent means of discovery and innovation in essentially all areas of science, engineering, technology, and society; and the CSE community is at the core of this transformation. However, a combination of disruptive developments---including the architectural complexity of extreme-scale computing, the data revolution that engulfs the planet, and the specialization required to follow the applications to new frontiers---is redefining the scope and reach of the CSE endeavor. This report describes the rapid expansion of CSE and the challenges to sustaining its bold advances. The report also presents strategies and directions for CSE research and education for the next decade.Comment: Major revision, to appear in SIAM Revie

IDENTIFIKASI MISKONSEPSI SISWA SMA KELAS X PADA MATERI MOMENTUM DAN IMPULS SETELAH PEMBELAJARAN INKUIRI BERBATUAN SIMULASI KOMPUTER

Miskonsepsi merupakan suatu konsepsi yang tidak sesuai dengan pandangan para ahli sehingga dapat menghambat siswa dalam mencapai tujuan pembelajaran Fisika. Miskonsepsi dapat terjadi pada berbagai materi Fisika seperti Momentum dan Impuls. Tujuan penelitian ini adalah untuk mengidentifikasi miskonsepsi siswa pada materi momentum dan impuls setelah pembelajaran inkuiri berbantuan simulasi komputer. Metode penelitian yang digunakan adalah metode pre-eksperimental dengan desain penelitian intact-group comparison. Penelitian ini dilakukan kepada siswa kelas X di salah satu SMA di kota Bandung yang dibagi menjadi dua kelompok, yaitu kelompok A yang terdiri atas 28 siswa (yang belajar menggunakan model inkuiri berbantuan simulasi komputer) dan kelompok B yang terdiri atas 30 siswa (yang belajar menggunakan pembelajaran konvensional). Instrumen yang digunakan untuk mengidentifikasi miskonsepsi siswa pada materi Momentum dan Impuls adalah Momentum and Impulse Four-tier Test (MIFT). Ditemukan bahwa konsepsi siswa terbagi menjadi lima kategori yaitu miskonsepsi, paham konsep, paham sebagian, tidak paham konsep, dan tidak dapat dikodekan. Persentase jumlah siswa yang mengalami miskonsepsi setelah pembelajaran inkuiri berbantuan simulasi komputer dan konvensional (ceramah) masing-masing 15,8% dan 33,8%. Miskonsepsi tersebar pada sub materi momentum, impuls, dan hubungan momentum dan impuls. Hal ini mengindikasikan bahwa penerapan model pembelajaran inkuiri berbantuan simulasi komputer lebih baik dalam memfasilitasi konsepsi siswa SMA kelas X pada materi Momentum dan Impuls. ----- Misconception is a conception which is not in accordance with the views of experts that can inhibit students in achieving the learning objectives of physics. Misconceptions can occur in a variety of physics materials such as momentum and impulse. The purpose of this study was to identify misconceptions students on the material momentum and impulse after computer simulations-assisted inquiry learning. The method used is pre-experimental with research design is intact-group comparison. This study was conducted to tenth grade students in one high school in Bandung who were divided into two groups: group a, which consists of 28 students (who learn to use computer simulations-assisted inquiry learning) and group b consisted of 30 students (who learn to use conventional learning). The instrument used to identify misconceptions students on momentum and impulse material is momentum and impulse four-tier test (MIFT). It was found that the student conception divided into five categories, that is misconceptions, sound understanding, partial understanding, no understanding, and no coding. The percentage of students who have misconceptions after computer simulations-assisted inquiry learning and conventional learning respectively is 15,8% and 33,8%. Misconceptions spread in sub material momentum, impulse and relation of momentum and impulse. This indicates that the application of computer simulations-assisted inquiry learning is better in facilitating the student conception on momentum and impulse materials

Active Brownian Particles. From Individual to Collective Stochastic Dynamics

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte