Simulation of beam-beam induced emittance growth in the HL-LHC with crab cavities

The emittance growth in the HL-LHC due to beam-beam effects is examined by virtue of strong-strong computer simulations. A model of the transverse damper and the noise level have been tuned to simulate the emittance growth in the present LHC. Simulations with projected HL-LHC beam parameters and crab cavities are discussed. It is shown that with the nominal working point, the large beam-beam tune shift moves the beam into a resonance that causes substantial emittance growth. Increasing the working point slightly is demonstrated to be very beneficial.Comment: 6 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201

Traveling Wave Solutions for Systems of ODEs on a Two-Dimensional Spatial Lattice

This is the published version, also available here: http://dx.doi.org/10.1137/S0036139996312703.We consider infinite systems of ODEs on the two-dimensional integer lattice, given by a bistable scalar ODE at each point, with a nearest neighbor coupling between lattice points. For a class of ideal nonlinearities, we obtain traveling wave solutions in each direction $e^{i\theta}$, and we explore the relation between the wave speed c, the angle $\theta$, and the detuning parameter a of the nonlinearity. Of particular interest is the phenomenon of "propagation failure," and we study how the critical value $a=a^*(\theta)$ depends on $\theta$, where $a^*(\theta)$ is defined as the value of the parameter a at which propagation failure (that is, wave speed c=0) occurs. We show that $a^*:\Bbb{R}\to\Bbb{R} is continuous at each point$\theta$where$\tan\theta$is irrational, and is discontinuous where$\tan\theta$ is rational or infinite

Pemodelan Inundasi (Banjir Rob) Di Pesisir Kota Semarang Dengan Menggunakan Model Hidrodinamika

Fenomena banjir rob yang terjadi di Semarang sudah sangat memprihatinkan, karena banjir ini tidak hanya terjadi pada daerah pesisir pantai saja tetapi sudah menggenangi wilayah pariwisata, pemukiman, maupun industri. Tujuan penelitian ini adalah untuk menghitung jarak dan luas genangan rob di pesisir Kota Semarang akibat kondisi pasang surut pada saat purnama dan perbani.Metode yang digunakan dalam penelitian ini adalah metode kuantitatif. Penelitian dibagi menjadi tiga tahap, yaitu pengumpulan data sekunder, pengambilan data lapangan, dan pengolahan data. Pengambilan data lapangan dilakukan di perairan Kota Semarang yang dilaksanakan dari tanggal 5 - 20 Juli 2010 pada koordinat 6052'30”- 6057'30” LS dan 110019'45”-110027'30” BT. Pengolahan data serta proses pemodelan dilakukan di BPPT, Yogyakarta. Berdasarkan hasil penelitian diketahui bahwa arus di daerah penelitian didominasi oleh arus pasang surut sebesar 74,3%, dimana pergerakannya condong dari arah utara ke selatan dengan kecepatan rata-rata terhadap kedalaman mencapai 0,024 m/s. Sedangkan dari hasil analisis banjir rob (inundasi), jarak terjauh terjadi di kecamatan Genuk yang mencapai 4,295 km dari garis pantai pada saat pasang purnama dan jarak terdekat terjadi di kecamatan Semarang Barat yang mencapai 488,93 m dari garis pantai pada saat pasang perbani. Selain itu berdasarkan hasil penelitian didapat luas banjir maksimal terjadi di kecamatan Tugu dengan luas 3450,1 Ha pada saat pasang purnama. Sedangkan wilayah yang paling sedikit terendam terjadi di kecamatan Gayamsari dengan luas 71,228 Ha pada saat pasang perbani. Hasil verifikasi bathimetri mempunyai tingkat kebenaran sekitar 73,69%, pasut sekitar 84,87%, vektor u dan v arus lapangan sekitar 93,58% dan model sekitar 92%

Experimental study of Taylor's hypothesis in a turbulent soap film

An experimental study of Taylor's hypothesis in a quasi-two-dimensional turbulent soap film is presented. A two probe laser Doppler velocimeter enables a non-intrusive simultaneous measurement of the velocity at spatially separated points. The breakdown of Taylor's hypothesis is quantified using the cross correlation between two points displaced in both space and time; correlation is better than 90% for scales less than the integral scale. A quantitative study of the decorrelation beyond the integral scale is presented, including an analysis of the failure of Taylor's hypothesis using techniques from predictability studies of turbulent flows. Our results are compared with similar studies of 3D turbulence.Comment: 27 pages, + 19 figure

Global Hopf bifurcation in the ZIP regulatory system

Regulation of zinc uptake in roots of Arabidopsis thaliana has recently been modeled by a system of ordinary differential equations based on the uptake of zinc, expression of a transporter protein and the interaction between an activator and inhibitor. For certain parameter choices the steady state of this model becomes unstable upon variation in the external zinc concentration. Numerical results show periodic orbits emerging between two critical values of the external zinc concentration. Here we show the existence of a global Hopf bifurcation with a continuous family of stable periodic orbits between two Hopf bifurcation points. The stability of the orbits in a neighborhood of the bifurcation points is analyzed by deriving the normal form, while the stability of the orbits in the global continuation is shown by calculation of the Floquet multipliers. From a biological point of view, stable periodic orbits lead to potentially toxic zinc peaks in plant cells. Buffering is believed to be an efficient way to deal with strong transient variations in zinc supply. We extend the model by a buffer reaction and analyze the stability of the steady state in dependence of the properties of this reaction. We find that a large enough equilibrium constant of the buffering reaction stabilizes the steady state and prevents the development of oscillations. Hence, our results suggest that buffering has a key role in the dynamics of zinc homeostasis in plant cells.Comment: 22 pages, 5 figures, uses svjour3.cl

Inverse velocity statistics in two dimensional turbulence

We present a numerical study of two-dimensional turbulent flows in the enstrophy cascade regime, with different large-scale forcings and energy sinks. In particular, we study the statistics of more-than-differentiable velocity fluctuations by means of two recently introduced sets of statistical estimators, namely {\it inverse statistics} and {\it second order differences}. We show that the 2D turbulent velocity field, $\bm u$, cannot be simply characterized by its spectrum behavior, $E(k) \propto k^{-\alpha}$. There exists a whole set of exponents associated to the non-trivial smooth fluctuations of the velocity field at all scales. We also present a numerical investigation of the temporal properties of $\bm u$ measured in different spatial locations.Comment: 9 pages, 12 figure