Rancang Bangun Dan Pengujian Kompor Metanol Untuk Keperluan Membatik

Bahan bakar merupakan suatu sumber daya yang bisa menghasilkan energi .yang banyak dipakai untuk keperluan rumah tangga maupun industri.Seperti industri batik yang masih menggunakan minyak tanah dan LPG sebagai bahan bakar kompor untuk media pemanasan lilin batik,akan tetapi dengan kenaikan harga minyak tanah dan kasus tabung LPG yang meledak akan berpengaruh terhadap kelangsungan hidup industry batik dimasa depan.Salah satu alternatif yang digunakan adalah dengan pemanfaatan bahan bakar methanol yang diharapkan mampu menjadi solusi energi alternatif untuk kelangsungan hidup indusrti batik dimasa depan, maka perlu dibuat desain bentuk burner dan penambahan selubung yang tepat agar proses pembakarannya sempurna. Penelitian bertujuan untuk mengetahui pengaruh selubung pada kompor metanol terhadap karakteristik pembakaran kemudian dibandingkan dengan karakteristik pembakaran pada kompor minyak tanah. Penelitian diawali dengan menggunakan kompor minyak tanah kemudian dibandingkan dengan kompor metanol yang divariasikan dengan penambahan selubung dan yang tidak memakai selubung. Tahap penelitian untuk setiap masing-masing kompor adalah dengan melakukukan pengujian terhadap karakteristik pembakaran yaitu dengan cara mengukur temperatur api dari hasil pembakaran, waktu pendidihan air sebanyak 500 ml dan konsumsi bahan bakar.Kemudian panelitian dilanjutkan dengan mencairkan 100gr malam batik yang bertujuan untuk mengetahui waktu yang dibutuhkan selama proses pencairan dan konsumsi bahan bakar. Hasil penelitian diketahui api paling setabil diperoleh pada kompor dengan penambahan selubung. Temperatur api tertertinggi diperoleh pada kompor dengan penambahan selubung. Konsumsi bahan bakar paling hemat sampai air mendidih dan malam mencair pada kompor dengan penambahan selubung, waktu pendidihan air dan pencairan malam paling cepat juga pada kompor metanol dengan penambahan selubung

Phonon Bottleneck Effect Leads to Observation of Quantum Tunneling of the Magnetization and Butterfly Hysteresis Loops in (Et4N)3Fe2F9

A detailed investigation of the unusual dynamics of the magnetization of (Et4N)3Fe2F9 (Fe2), containing isolated [Fe2F9]3- dimers, is presented and discussed. Fe2 possesses an S=5 ground state with an energy barrier of 2.40 K due to an axial anisotropy. Poor thermal contact between sample and bath leads to a phonon bottleneck situation, giving rise to butterfly-shaped hysteresis loops below 5 K concomitant with slow decay of the magnetization for magnetic fields Hz applied along the Fe--Fe axis. The butterfly curves are reproduced using a microscopic model based on the interaction of the spins with resonant phonons. The phonon bottleneck allows for the observation of resonant quantum tunneling of the magnetization at 1.8 K, far above the blocking temperature for spin-phonon relaxation. The latter relaxation is probed by AC magnetic susceptibility experiments at various temperatures and bias fields. At H=0, no out-of-phase signal is detected, indicating that at T smaller than 1.8 K Fe2 does not behave as a single-molecule magnet. At 1 kG, relaxation is observed, occurring over the barrier of the thermally accessible S=4 first excited state that forms a combined system with the S=5 state.Comment: 10 pages, 10 figure

Gamma-Ray Burst Polarization: Limits from RHESSI Measurements

Using the RHESSI satellite as a Compton polarimeter, a recent study claimed that the prompt emission of GRB021206 was almost fully linearly polarized. This was challenged by a subsequent reanalysis. We present an novel approach, applying our method to the same data. We identify Compton scattering candidates by carefully filtering events in energy, time, and scattering geometry. Our polarization search is based on time dependent scattering rates in perpendicular directions, thus optimally excluding systematic errors. We perform simulations to obtain the instrument's polarimetric sensitivity, and these simulations include photon polarization. For GRB021206, we formally find a linear polarization degree of 41% (+57% -44%), concluding that the data quality is insufficient to constrain the polarization degree in this case. We further applied our analysis to GRB030519B and found again a null result.Comment: 39 pages, 11 figures, accepted for publication by the Astrophysical Journa

Quantum statistics of interacting dimer spin systems

The compound TlCuCl3 represents a model system of dimerized quantum spins with strong interdimer interactions. We investigate the triplet dispersion as a function of temperature by inelastic neutron scattering experiments on single crystals. By comparison with a number of theoretical approaches we demonstrate that the description of Troyer, Tsunetsugu, and Wurtz [Phys. Rev. B 50, 13 515 (1994)] provides an appropriate quantum statistical model for dimer spin systems at finite temperatures, where many-body correlations become particularly important

Scaling laws of solar and stellar flares

In this study we compile for the first time comprehensive data sets of solar and stellar flare parameters, including flare peak temperatures T_p, flare peak volume emission measures EM_p, and flare durations t_f from both solar and stellar data, as well as flare length scales L from solar data. Key results are that both the solar and stellar data are consistent with a common scaling law of EM_p ~ T_p^4.7, but the stellar flares exhibit ~250 times higher emission measures (at the same flare peak temperature). For solar flares we observe also systematic trends for the flare length scale L(T_p) ~ T_p^0.9 and the flare duration t_F(T_p) ~ T_p^0.9 as a function of the flare peak temperature. Using the theoretical RTV scaling law and the fractal volume scaling observed for solar flares, i.e., V(L) ~ L^2.4, we predict a scaling law of EM_p ~ T_p^4.3, which is consistent with observations, and a scaling law for electron densities in flare loops, n_p ~ T_p^2/L ~ T_p^1.1. The RTV-predicted electron densities were also found to be consistent with densities inferred from total emission measures, n_p=(EM_p/q_V*V)^1/2, using volume filling factors of q_V=0.03-0.08 constrained by fractal dimensions measured in solar flares. Our results affect also the determination of radiative and conductive cooling times, thermal energies, and frequency distributions of solar and stellar flare energies.Comment: 9 Figs., (paper in press, The Astrophsycial Journal

[OI] disk emission in the Taurus star forming region

The structure of protoplanetary disks is thought to be linked to the temperature and chemistry of their dust and gas. Whether the disk is flat or flaring depends on the amount of radiation that it absorbs at a given radius, and on the efficiency with which this is converted into thermal energy. The understanding of these heating and cooling processes is crucial to provide a reliable disk structure for the interpretation of dust continuum emission and gas line fluxes. Especially in the upper layers of the disk, where gas and dust are thermally decoupled, the infrared line emission is strictly related to the gas heating/cooling processes. We aim to study the thermal properties of the disk in the oxygen line emission region, and to investigate the relative importance of X-ray (1-120 Angstrom) and far-UV radiation (FUV, 912-2070 Angstrom) for the heating balance there. We use [OI] 63 micron line fluxes observed in a sample of protoplanetary disks of the Taurus/Auriga star forming region and compare it to the model predictions presented in our previous work. The data were obtained with the PACS instrument on board the Herschel Space Observatory as part of the Herschel Open Time Key Program GASPS (GAS in Protoplanetary diskS), published in Howard et al. (2013). Our theoretical grid of disk models can reproduce the [OI] absolute fluxes and predict a correlation between [OI] and the sum Lx+Lfuv. The data show no correlation between the [OI] line flux and the X-ray luminosity, the FUV luminosity or their sum. The data show that the FUV or X-ray radiation has no notable impact on the region where the [OI] line is formed. This is in contrast with what is predicted from our models. Possible explanations are that the disks in Taurus are less flaring than the hydrostatic models predict, and/or that other disk structure aspects that were left unchanged in our models are important. ..abridged..Comment: 9 pages, accepted for publication in A&

Are Coronae of Magnetically Active Stars Heated by Flares? III. Analytical Distribution of Superimposed Flares

(abridged) We study the hypothesis that observed X-ray/extreme ultraviolet emission from coronae of magnetically active stars is entirely (or to a large part) due to the superposition of flares, using an analytic approach to determine the amplitude distribution of flares in light curves. The flare-heating hypothesis is motivated by time series that show continuous variability suggesting the presence of a large number of superimposed flares with similar rise and decay time scales. We rigorously relate the amplitude distribution of stellar flares to the observed histograms of binned counts and photon waiting times, under the assumption that the flares occur at random and have similar shapes. Applying these results to EUVE/DS observations of the flaring star AD Leo, we find that the flare amplitude distribution can be represented by a truncated power law with a power law index of 2.3 +/- 0.1. Our analytical results agree with existing Monte Carlo results of Kashyap et al. (2002) and Guedel et al. (2003). The method is applicable to a wide range of further stochastically bursting astrophysical sources such as cataclysmic variables, Gamma Ray Burst substructures, X-ray binaries, and spatially resolved observations of solar flares.Comment: accepted for publication in Ap

The solar energetic balance revisited by young solar analogs, helioseismology and neutrinos

The energetic balance of the Standard Solar Model (SSM) results from an equilibrium between nuclear energy production, energy transfer, and photospheric emission. In this letter, we derive an order of magnitude of several % for the loss of energy in kinetic energy, magnetic energy, and X or UV radiation during the whole solar lifetime from the observations of the present Sun. We also estimate the mass loss from the observations of young solar analogs which could reach up to 30% of the current mass. We deduce new models of the present Sun, their associated neutrino fluxes, and their internal sound-speed profile. This approach sheds quantitative lights on the disagreement between the sound speed obtained by helioseismology and the sound speed derived from the SSM including the updated photospheric CNO abundances, based on recent observations. We conclude that about 20% of the present discrepancy could come from the incorrect description of the early phases of the Sun, its activity, its initial mass and mass-loss history. This study has obvious consequences on the solar system formation and the early evolution of the closest planets.Comment: 14 pages, 3 figures; Published in ApJ lett 201

Solar Wind and its Evolution

By using our previous results of magnetohydrodynamical simulations for the solar wind from open flux tubes, I discuss how the solar wind in the past is different from the current solar wind. The simulations are performed in fixed one-dimensional super-radially open magnetic flux tubes by inputing various types of fluctuations from the photosphere, which automatically determines solar wind properties in a forward manner. The three important parameters which determine physical properties of the solar wind are surface fluctuation, magnetic field strengths, and the configuration of magnetic flux tubes. Adjusting these parameters to the sun at earlier times in a qualitative sense, I infer that the quasi-steady-state component of the solar wind in the past was denser and slightly slower if the effect of the magneto-centrifugal force is not significant. I also discuss effects of magneto-centrifugal force and roles of coronal mass ejections.Comment: 6 pages, 1 figure, Earth, Planets, & Space in press (based on 5th Alfven Conference) correction of discussion on a related pape