12,860 research outputs found
Purely Magnetic Spacetimes
Purely magnetic spacetimes, in which the Riemann tensor satisfies
for some unit timelike vector , are studied. The
algebraic consequences for the Weyl and Ricci tensors are examined in detail
and consideration given to the uniqueness of . Some remarks concerning the
nature of the congruence associated with are made.Comment: 12 pages, standard latex. Submitted to Classical and Quantum Gravity
Peningkatan Kemampuan Menulis Pengumuman Melalui Metode Latihan Siswa Kelas IV SD Inpres 2 Gio Kecamatan Moutong
Permasalahan penelitian ini adalah apakah dengan menggunakan metode latihan dapat meningkatkan kemampuan menulis pengumuman siswa kelas IV SD Inpres 2 Gio Kecamatan Moutong? Tujuan penelitian ini untuk meningkatkan kemampuan menulis pengumuman melalui metode latihan siswa kelas IV SD Inpres 2 Gio Kecamatan Moutong. Sumber data siswa dan guru (peneliti). Jenis data adalah data kuantitatif berupa hasil evaluasi pada siklus I dan siklus II dan data kualitatif beupa hasil observasi aktivitas guru dan siswa. Subjek penelitian adalah siswa kelas IV berjumlah 27 siswa terdiri dari 12 laki-laki dan 15 perempuan. Proses penelitian tindakan kelas ini dilaksanakan dua siklus meliputi: (1) perncanaan, (2) pelaksanaan tindakan, (3) Observasi, (4) Refleksi. Hasil evaluasi siswa siklus I rata-rata daya serap 71,07 % dengan presentase ketuntasan klasikal 63 % siklus II nilai rata-rata daya serap meningkat menjadi 79,88 dengan ketuntasan klasikal 93%. Hasil observasi guru siklus I sebesar 75% kategori cukup siklus II sebesar 82% kategori baik. Hasil observasi siswa siklus I sebesar 77,5% kategori cukup siklus II sebesar 82,50% kategori baik. Berdasarkan data tersebut, menunjukan bahwa metode latihan dapat meningkatkan kemampuan menulis pengumuman siswa kelas IV SD Inpres 2 Gio Kecamatan Moutong
Evaluation of greenwaste mulch to control runoff quality from landfill sites during frequent storms
This paper describes a preliminary evaluation of two types of greenwaste (fresh and aged) used as a mulch layer to control runoff from disturbed landfill areas. Fresh greenwaste refers to woody and herbaceous garden waste that has been recently collected, chopped and shredded. Aged greenwaste is greenwaste which has been stockpiled for 18 months. We used rainfall simulator tests to investigate two aspects: (1) the performance of greenwaste mulch in reducing runoff during designed storm events with a high frequency of occurrence and (2) the release of pollutants via runoff as total suspended solids (TSS) and total organic carbon (TOC) during rain. Rainfall of <5-year average recurrence interval (ARI) was generally applied, consistent with stormwater compliance requirements for many Australian landfills. TOC released from fresh greenwaste material was higher in concentration than from aged greenwaste. However when used as a 10cm-deep mulch layer, fresh greenwaste was able to completely prevent runoff, even when tested under rainfalls up to 50 year ARI duration. An equivalent mulch layer of aged greenwaste was also effective in reducing runoff volume and TSS concentration compared with the bare soil during a 3.5-year ARI rainfall, but mean TOC concentration was higher. Based on these preliminary results, fresh greenwaste mulching of bare soils is an attractive option to control runoff and erosion from areas subject to intermittent landfill operations and worthy of further investigations
Length and time scale divergences at the magnetization-reversal transition in the Ising model
The divergences of both the length and time scales, at the magnetization-
reversal transition in Ising model under a pulsed field, have been studied in
the linearized limit of the mean field theory. Both length and time scales are
shown to diverge at the transition point and it has been checked that the
nature of the time scale divergence agrees well with the result obtained from
the numerical solution of the mean field equation of motion. Similar growths in
length and time scales are also observed, as one approaches the transition
point, using Monte Carlo simulations. However, these are not of the same nature
as the mean field case. Nucleation theory provides a qualitative argument which
explains the nature of the time scale growth. To study the nature of growth of
the characteristic length scale, we have looked at the cluster size
distribution of the reversed spin domains and defined a pseudo-correlation
length which has been observed to grow at the phase boundary of the transition.Comment: 9 pages Latex, 3 postscript figure
Dynamic Magnetization-Reversal Transition in the Ising Model
We report the results of mean field and the Monte Carlo study of the dynamic
magnetization-reversal transition in the Ising model, brought about by the
application of an external field pulse applied in opposition to the existing
order before the application of the pulse. The transition occurs at a
temperature T below the static critical temperature T_c without any external
field. The transition occurs when the system, perturbed by the external field
pulse competing with the existing order, jumps from one minimum of free energy
to the other after the withdrawal of the pulse. The parameters controlling the
transition are the strength h_p and the duration Delta t of the pulse. In the
mean field case, approximate analytical expression is obtained for the phase
boundary which agrees well with that obtained numerically in the small Delta t
and large T limit. The order parameter of the transition has been identified
and is observed to vary continuously near the transition. The order parameter
exponent beta was estimated both for the mean field (beta =1) and the Monte
Carlo beta = 0.90 \pm 0.02 in two dimension) cases. The transition shows a
"critical slowing-down" type behaviour near the phase boundary with diverging
relaxation time. The divergence was found to be logarithmic in the mean field
case and exponential in the Monte Carlo case. The finite size scaling technique
was employed to estimate the correlation length exponent nu (= 1.5 \pm 0.3 in
two dimension) in the Monte Carlo case.Comment: 13 pages, latex, 8 figure
Gluon Condensates, Chiral Symmetry Breaking and Pion Wave Function
We consider here chiral symmetry breaking in quantum chromodynamics arising
from gluon condensates in vacuum. Through coherent states of gluons simulating
a mean field type of approximation, we show that the off-shell gluon
condensates of vacuum generate a mass-like contribution for the quarks, giving
rise to chiral symmetry breaking. We next note that spontaneous breaking of
global chiral symmetry links the four component quark field operator to the
pion wave function. This in turn yields many hadronic properties in the light
quark sector in agreement with experiments, leading to the conclusion that low
energy hadron properties are primarily driven by the vacuum structure of
quantum chromodynamics.Comment: 25 pages, IP/BBSR/92-76, revte
- …