Model Perencanaan Pengiriman Struktur Anjungan Lepas Pantai

Anjungan atau bangunan lepas pantai (offshore platform) adalah struktur atau bangunan yang dibuat sebagai sarana dalam proses eksplorasi minyak dan gas di lepas pantai. Jenis anjungan lepas pantai yang sering dipakai di Indonesia adalah jenis fixed platform. Anjungan lepas pantai ini dibuat di darat, kemudian diangkut dan diinstalasi di lokasi eksplorasi. Pengangkutan ini biasanya menggunakan 3 (tiga) cara atau skenario yang merupakan kombinasi antara ketersediaan dan ukuran barge. Setiap cara dipilih dengan alasan yang tidak jelas selain kedua yang disebut di atas, oleh karena itu penelitian ini bertujuan untuk mengetahui faktor yang mempengaruhi pemilihan skenario pengangkutan dan pemilihan barge untuk mengangkut jacket maupun topside, dan kemudian membuatnya dalam sebuah model. Berdasarkan hasil wawancara, penentuan skenario pengiriman jacket dan topside dilakukan dengan memperhatikan 4 faktor, yaitu, (i) jadwal selesai fabrikasi dan instalasi jacket maupun topside (ii) dimensi dan berat jacket dan topside (iii) ketersediaan barge, serta (iv) jarak dari lokasi fabrikasi ke instalasi. Pembuatan model untuk memilih skenario yang tepat dilakukan setelah mewawancarai beberapa pakar di bidangnya. Berdasarkan hasil perhitungan model, pada site 1, barge yang terpilih adalah B 34 dengan sewa harian sebesar Rp 1.927 jt. dan barge B4 sewa TCH/bulan sebesar Rp 2.199 jt. Sedangkan barge dalam negeri yaitu B18 sewa TCH per bulan sebesar Rp 2.147 jt. dan B19 sewa harian sebesar Rp 1.023 jt. Pada site 2 barge yang terpilih adalah B14 dengan sewa VCH sebesar Rp 6309 jt. Sedangkan barge dalam negeri adalah B17 sewa tch per bulan sebesar Rp 11897 Jt. Pada site 3 barge luar negeri yang terpilih adalah barge B10 dengan sewa harian sebesar Rp 4.448 jt. dan B15 dengan sewa TCH/bulan sebersar Rp 3.302 jt. Sedangkan barge dalam negeri yaitu B20 dengan sewa VCH sebesar Rp 3.659 jt. dan B16 dengan sewa TCH per bulan sebesar 8119 jt

Static Gravitational Global Monopoles

Static solutions in spherical symmetry are found for gravitating global monopoles. Regular solutions lacking a horizon are found for $\eta < 1/\sqrt{8\pi}$, where $\eta$ is the scale of symmetry breaking. Apparently regular solutions with a horizon are found for 1/\sqrt{8\pi} \le \eta \alt \sqrt{3/8\pi}. Though they have a horizon, they are not Schwarzschild. The solution for $\eta = 1/\sqrt{8\pi}$ is argued to have a horizon at infinity. The failure to find static solutions for $\eta > \sqrt{3/8\pi} \approx 0.3455$ is consistent with findings that topological inflation begins at $\eta \approx 0.33$.Comment: 4 pages, 6 figure

On stability of discretizations of the Helmholtz equation (extended version)

We review the stability properties of several discretizations of the Helmholtz equation at large wavenumbers. For a model problem in a polygon, a complete $k$-explicit stability (including $k$-explicit stability of the continuous problem) and convergence theory for high order finite element methods is developed. In particular, quasi-optimality is shown for a fixed number of degrees of freedom per wavelength if the mesh size $h$ and the approximation order $p$ are selected such that $kh/p$ is sufficiently small and $p = O(\log k)$, and, additionally, appropriate mesh refinement is used near the vertices. We also review the stability properties of two classes of numerical schemes that use piecewise solutions of the homogeneous Helmholtz equation, namely, Least Squares methods and Discontinuous Galerkin (DG) methods. The latter includes the Ultra Weak Variational Formulation

Weak-Lensing by Large-Scale Structure and the Polarization Properties of Distant Radio-Sources

We estimate the effects of weak lensing by large-scale density inhomogeneities and long-wavelength gravitational waves upon the polarization properties of electromagnetic radiation as it propagates from cosmologically distant sources. Scalar (density) fluctuations do not rotate neither the plane of polarization of the electromagnetic radiation nor the source image. They produce, however, an appreciable shear, which distorts the image shape, leading to an apparent rotation of the image orientation relative to its plane of polarization. In sources with large ellipticity the apparent rotation is rather small, of the order (in radians) of the dimensionless shear. The effect is larger at smaller source eccentricity. A shear of 1% can induce apparent rotations of around 5 degrees in radio sources with the smallest eccentricity among those with a significant degree of integrated linear polarization. We discuss the possibility that weak lensing by shear with rms value around or below 5% may be the cause for the dispersion in the direction of integrated linear polarization of cosmologically distant radio sources away from the perpendicular to their major axis, as expected from models for their magnetic fields. A rms shear larger than 5% would be incompatible with the observed correlation between polarization properties and source orientation in distant radio galaxies and quasars. Gravity waves do rotate both the plane of polarization as well as the source image. Their weak lensing effects, however, are negligible.Comment: 23 pages, 2 eps figures, Aastex 4.0 macros. Final version, as accepted by ApJ. Additional references and some changes in the introduction and conclusion

A Search for the Fourth SM Family Fermions and E_6 Quarks at μ+μ−\mu ^{+}\mu ^{-} Colliders

The potential of $\mu ^{+}\mu ^{-}$ colliders to investigate the fourth SM family fermions predicted by flavour democracy has been analyzed. It is shown that muon colliders are advantageous for both pair production of fourth family fermions and resonance production of fourth family quarkonia. Also isosinglet quarks production at $\mu ^{+}\mu ^{-}$ colliders has been investigated.Comment: 9 pages, 5 table

Modelling the dynamics of global monopoles

A thin wall approximation is exploited to describe a global monopole coupled to gravity. The core is modelled by de Sitter space; its boundary by a thin wall with a constant energy density; its exterior by the asymptotic Schwarzschild solution with negative gravitational mass $M$ and solid angle deficit, $\Delta\Omega/4\pi = 8\pi G\eta^2$, where $\eta$ is the symmetry breaking scale. The deficit angle equals $4\pi$ when $\eta=1/\sqrt{8\pi G} \equiv M_p$. We find that: (1) if $\eta <M_p$, there exists a unique globally static non-singular solution with a well defined mass, $M_0<0$. $M_0$ provides a lower bound on $M$. If $M_0<M<0$, the solution oscillates. There are no inflating solutions in this symmetry breaking regime. (2) if $\eta \ge M_p$, non-singular solutions with an inflating core and an asymptotically cosmological exterior will exist for all $M<0$. (3) if $\eta$ is not too large, there exists a finite range of values of $M$ where a non-inflating monopole will also exist. These solutions appear to be metastable towards inflation. If $M$ is positive all solutions are singular. We provide a detailed description of the configuration space of the model for each point in the space of parameters, $(\eta, M)$ and trace the wall trajectories on both the interior and the exterior spacetimes. Our results support the proposal that topological defects can undergo inflation.Comment: 44 pages, REVTeX, 11 PostScript figures, submitted to the Physical Review D. Abstract's correcte

Gravity of Monopole and String and Gravitational Constant in 3He-A

We discuss the effective metric produced in superfluid 3He-A by such topological objects as radial disgyration and monopole. In relativistic theories these metrics are similar to that of the local string and global monopole correspondingly. But in 3He-A they have the negative angle deficit, which corresponds to the negative mass of the topological objects. The effective gravitational constant G in superfluid 3He-A, derived from the comparison with relativistic theories, is inversely proportional to the square of the gap amplitude Delta, which plays the part of the Planck energy cut-off. G depends on temperature and increases with T, which corresponds to the vacuum screening of the Newton's constant.Comment: Latex file, 10 pages, no figure

Exotic spacetimes, superconducting strings with linear momentum, and (not quite) all that

We derive the general exact vacuum metrics associated with a stationary (non static), non rotating, cylindrically symmetric source. An analysis of the geometry described by these vacuum metrics shows that they contain a subfamily of metrics that, although admitting a consistent time orientation, display "exotic" properties, such as "trapping" of geodesics and closed causal curves through every point. The possibility that such spacetimes could be generated by a superconducting string, endowed with a neutral current and momentum, has recently been considered by Thatcher and Morgan. Our results, however, differ from those found by Thatcher and Morgan, and the discrepancy is explained. We also analyze the general possibility of constructing physical sources for the exotic metrics, and find that, under certain restrictions, they must always violate the dominant energy condition (DEC). We illustrate our results by explicitly analyzing the case of concentric shells, where we find that in all cases the external vacuum metric is non exotic if the matter in the shells satisfies the DEC.Comment: 13 pages with no figures. Accepted in PR

Bremsstrahlung in the gravitational field of a cosmic string

In the framework of QED we investigate the bremsstrahlung process for an electron passing by a straight static cosmic string. This process is precluded in empty Minkowski space-time by energy and momentum conservation laws. It happens in the presence of the cosmic string as a consequence of the conical structure of space, in spite of the flatness of the metric. The cross section and emitted electromagnetic energy are computed and analytic expressions are found for different energies of the incoming electron. The energy interval is divided in three parts depending on whether the energy is just above electron rest mass $M$, much larger than $M$, or exceeds $M/\delta$, with $\delta$ the string mass per unit length in Planck units. We compare our results with those of scalar QED and classical electrodynamics and also with conic pair production process computed earlier.Comment: 21 pages, to appear in Phys. Rev. D., KONS-RGKU-94-0

Topological Defects in Gravitational Theories with Non Linear Lagrangians

The gravitational field of monopoles, cosmic strings and domain walls is studied in the quadratic gravitational theory $R+\alpha R^2$ with $\alpha |R|\ll 1$, and is compared with the result in Einstein's theory. The metric aquires modifications which correspond to a short range `Newtonian' potential for gauge cosmic strings, gauge monopoles and domain walls and to a long range one for global monopoles and global cosmic strings. In this theory the corrections turn out to be attractive for all the defects. We explain, however, that the sign of these corrections in general depends on the particular higher order derivative theory and topological defect under consideration. The possible relevance of our results to the study of the evolution of topological defects in the early universe is pointed out.Comment: LaTeX (uses revrex macros), 13 page