Pengembangan Aplikasi Simulasi Perdagangan Saham dengan Sector Rotation dan Linear Programming

In strategic development a university will shift from teaching university to research university. It is because academic outcomes will be more useful if they can be commercialized by industries, which help improve the ranking of a university. The development of capital market and management measures of Indonesia Stock Exchange during the last 8 years aiming at academicians in order to identify and be interested in investing in the stock market needs to be observed. That is by providing a simulation so that more students can improve the competition at their graduation. The involvement of industry selection strategy and portfolio management will be required so that the expertise and ability to manage investments in the capital market can be better. So, it necessarily requires a development of simulation application of stock trading with business rotation and linear programming

Translational groups as generators of gauge transformations

We examine the gauge generating nature of the translational subgroup of Wigner's little group for the case of massless tensor gauge theories and show that the gauge transformations generated by the translational group is only a subset of the complete set of gauge transformations. We also show that, just like the case of topologically massive gauge theories, translational groups act as generators of gauge transformations in gauge theories obtained by extending massive gauge noninvariant theories by a Stuckelberg mechanism. The representations of the translational groups that generate gauge transformations in such Stuckelberg extended theories can be obtained by the method of dimensional descent. We illustrate these with the examples of Stuckelberg extended first class versions of Proca, Einstein-Pauli-Fierz and massive Kalb-Ramond theories in 3+1 dimensions. A detailed analysis of the partial gauge generation in massive and massless 2nd rank symmetric gauge theories is provided. The gauge transformations generated by translational group in 2-form gauge theories are shown to explicitly manifest the reducibility of gauge transformations in these theories.Comment: Latex, 20 pages, no figures, Version to appear in Physical Review

Four-fold basal plane anisotropy of the nonlocal magnetization of YNi2B2C

Studies of single crystal YNi2B2C have revealed a four-fold anisotropy of the equilibrium magnetization in the square crystallographic basal plane. This pi/2 periodicity occurs deep in the superconductive mixed state. In this crystal symmetry, an ordinary superconductive mass anisotropy (as in usual London theory) allows only a constant, isotropic response. In contrast, the experimental results are well described by generalized London theory incorporating non-local electrodynamics, as needed for this clean, intermediate-k superconductor.Comment: 4 pages, 4 figure

Magneto-electrodynamics at high frequencies in the antiferromagnetic and superconducting states of DyNi_2B_2C

We report the observation of novel behaviour in the radio frequency (rf) and microwave response of DyNi_2B_2C over a wide range of temperature (T) and magnetic field (H) in the antiferromagnetic (AFM) and superconducting (SC) states. At microwave frequencies of 10 GHz, the T dependence of the surface impedance Z_s=R_s+iX_s was measured which yields the T dependence of the complex conductivity \sigma_1-i\sigma_2 in the SC and AFM states. At radio frequencies (4 MHz), the H and T dependence of the penetration depth \lambda(T,H) were measured. The establishment of antiferromagnetic order at T_N=10.3 K results in a marked decrease in the scattering of charge carriers, leading to sharp decreases in R_s and X_s. However, R_s and X_s differ from each other in the AFM state. We show that the results are consistent with conductivity relaxation whence the scattering rate becomes comparable to the microwave frequency. The rf measurements yield a rich dependence of the scattering on the magnetic field near and below T_N. Anomalous decrease of scattering at moderate applied fields is observed at temperatures near and above T_N, and arises due to a crossover from a negative magnetoresistance state, possibly associated with a loss of spin disorder scattering at low fields, to a positive magnetoresistance state associated with the metallic nature. The normal state magnetoresistance is positive at all temperatures for \mu_0H>2T and at all fields for T>15K. Several characteristic field and temperature scales associated with metamagnetic transitions (H_M1(T), H_M2(T)) and onset of spin disorder H_D(T), in addition to T_c, T_N and H_c2(T) are observed in the rf measurements.Comment: 9 pages, Latex, Uses REVTeX, This and related publications also available at http://sagar.physics.neu.edu/ Submitted to Phys. Rev.

Influence of nonlocal electrodynamics on the anisotropic vortex pinning in YNi2B2CYNi_2B_2C

We have studied the pinning force density Fp of YNi_2B_2C superconductors for various field orientations. We observe anisotropies both between the c-axis and the basal plane and within the plane, that cannot be explained by usual mass anisotropy. For magnetic field $H \parallel c$, the reorientation structural transition in the vortex lattice due to nonlocality, which occurs at a field $H_1 \sim 1kOe$, manifests itself as a kink in Fp(H). When $H \bot c$, Fp is much larger and has a quite different H dependence, indicating that other pinning mechanisms are present. In this case the signature of nonlocal effects is the presence of a fourfold periodicity of Fp within the basal plane.Comment: 4 pages, 3 figure

A study of supercooling of the disordered vortex phase via minor hysteresis loops in 2H-NbSe_2

We report on the observation of novel features in the minor hysteresis loops in a clean crystal of NbSe_2 which displays a peak effect. The observed behavior can be explained in terms of a supercooling of the disordered vortex phase while cooling the superconductor in a field. Also, the extent of spatial order in a flux line lattice formed in ascending fields is different from (and larger than) that in the descending fields below the peak position of the peak effect; this is attributed to unequal degree of annealing of the state induced by a change of field in the two cases.Comment: 5 pages of text + 6 figures, submitted to Phys. Rev.

Equilibrium basal-plane magnetization of superconductive YNi(2)B(2)C - the influence of non-local electrodynamics

For a single crystal of YNi(2)B(2)C superconductor, the equilibrium magnetization M in the square basal plane has been studied experimentally as a function of temperature and magnetic field. While the magnetization M(H) deviates from conventional London predictions, a recent extension of London theory (to include effects of non-local electrodynamics) describes the experiments accurately. The resulting superconductive parameters are well behaved. These results are compared with corresponding findings for the case with M perpendicular to the basal plane.Comment: 7 pages, 5 Postscript Figures, 2 table

Reentrant Peak Effect in an anisotropic superconductor 2H-NbSe_2 : Role of disorder

The reentrant nature of Peak Effect is established in a single crystal of 2H-NbSe_2 via electrical transport and dc magnetisation studies. The role of disorder on the reentrant branch of PE has been examined in three single crystals with varying levels of quenched random disorder. Increasing disorder presumably shrinks the (H,T) parameter space over which vortex array retains spatial order. Although, the upper branch of the PE curve is somewhat robust, the lower reentrant branch of the same curve is strongly affected by disorder.Comment: 5 Pages of text, 4 figure

Metastability and Transient Effects in Vortex Matter Near a Decoupling Transition

We examine metastable and transient effects both above and below the first-order decoupling line in a 3D simulation of magnetically interacting pancake vortices. We observe pronounced transient and history effects as well as supercooling and superheating between the 3D coupled, ordered and 2D decoupled, disordered phases. In the disordered supercooled state as a function of DC driving, reordering occurs through the formation of growing moving channels of the ordered phase. No channels form in the superheated region; instead the ordered state is homogeneously destroyed. When a sequence of current pulses is applied we observe memory effects. We find a ramp rate dependence of the V(I) curves on both sides of the decoupling transition. The critical current that we obtain depends on how the system is prepared.Comment: 10 pages, 15 postscript figures, version to appear in PR

Generic phase diagram for vortex matter via a study of peak effect phenomenon in crystals of 2H-NbSe<SUB>2</SUB>

The disordering of a flux line lattice (FLL) is studied in weak pinning single crystal samples of the layered low-Tc superconductor NbSe2 containing varying amounts of quenched disorder. The phenomenon of the peak effect, i.e., an anomalous peak in the critical current, attributed to a collapse of the correlated volume of the pinned FLL, shows a rich evolution as the quenched disorder is varied. The experimental results demonstrate (i) the effect of disorder on the peak effect boundary in the (H, T) space, (ii) the appearance of a new disorder induced transformation at the onset of the peak effect that is attributed to a transformation of a topologically ordered FLL to a plastically deformed one, (iii) a two-step process that leads to the amorphization of the FLL, and (iv) the appearance of strong metastability and history dependence of the magnetic response of the system. These results elucidate the combined effects of quenched disorder and thermal fluctuations on the stability of the ordered lattice and on the transformation process into glassy disordered phases. The experimentally constructed 'generic phase diagram' is compared with theoretically expected behavior of vortex matter with quenched disorder