193 research outputs found
Development and application of generalized MUSTA schemes
No full textNumerical methods for solving non-linear systems of hyperbolic conservation laws via finite volume methods or discontinuous Galerkin finite element methods require, as the building block, a monotone numerical flux. The simplest approach for providing a monotone numerical utilizes a symmetric stencil and does not explicitly make use of wave propagation information, giving rise to centred or symmetric schemes. A more refined approach utilizes wave propagation information through the exact or approximate solution of the Riemann problem, giving rise to Godunov methods. Conventional approximate Riemann solvers are usually complex and are not available for many systems of practical interest, such as for models for compressible multi-phase flows. It is thus desirable to construct a numerical flux that emulates the best flux available (upwind) with the simplicity and generality of symmetric schemes. Here we build upon MUSTA approach [2,3], which leads to schemes that have the simplicity and generality of symmetric schemes and the accuracy of upwind schemes. First we present a new flux that is an average of symmetric fluxes and which reproduces the Godunov upwind scheme for the model hyperbolic equation. For non-linear systems it is found that this flux gives superior results to those of the whole family of incomplete Riemann solvers that do not explicitly account for linearly degenerate fields. Then we incorporate this flux into the MUSTA multi-staging approach, as predictor and corrector. It is found that the resulting MUSTA schemes reproduce the Godunov upwind scheme for the model hyperbolic equation for any number of stages, including multiple space dimensions. They are linearly stable in two and three space dimensions and the stability region is identical to that of the Godunov upwind method. For non-linear systems the MUSTA scheme with one or two stages gives results that are indistinguishable from those of Riemann solvers, such as the exact Riemann solver or Roe approximate Riemann solver. Finally, we assess the schemes on carefully chosen test problems for the one-dimensional equations of magneto hydrodynamics and nonlinear elasticity. High-order examples are provided for the multidimensional Euler equations in the framework of finite-volume WENO schemes [1]. The results illustrate the accuracy and efficiency of new methods combined with the ease of coding
Functional Cramér–Rao bounds and Stein estimators in Sobolev spaces, for Brownian motion and Cox processes
No full textWe investigate the problems of drift estimation for a shifted Brownian motion and intensity estimation for a Cox process on a finite interval [0,T], when the risk is given by the energy functional associated to some fractional Sobolev space H01⊂Wα,2⊂L2. In both situations, Cramér–Rao lower bounds are obtained, entailing in particular that no unbiased estimators (not necessarily adapted) with finite risk in H01 exist. By Malliavin calculus techniques, we also study super-efficient Stein type estimators (in the Gaussian case)
Kajian geokimia konkresi dan hubungannya dengan pembentukkan bauksit di kawasan Kuantan
No full textProses luluhawa kimia pada batuan basalt di kawasan Kuantan telah menghasilkan konkresi.
Sebanyak 21 sampel konkresi tersebut yang diambil daripada 5 profil luluhawa telah dianalis kandungan
unsur major dan unsur surih. Keputusan menunjukkan Al2O a dan Fe2O3 merupakan unsur yang
melimpah dengan julat kepekatan masing-masing 32.35%-52.23% dan 14.96%-33.99%. Kepekatan TiO2
pula berjulat 3.030/0-6.62% manakala SiO2 berjulat bdl-8.07%. Unsur-unsur MgO, CaO, Na2O dan K2O
kebanyakannya di bawah had pengesanan (bdl). SiO2, FeO, MnO dan P2O5 masih boleh dikesan dalam
sampel tetapi kebanyakannya kurang daripada 1%. Kesimpulan yang boleh dibuat berdasarkan data
geokimia unsur major ialah konkresi tersebut adalah berkomposisi bauksit, dengan Al2O3, Fe2O3, SiO2
dan TiO2 sebagai unsur pembentuk mineral yang utama. Mineral yang melimpah dan dikesan mengikut
pertambahan kelimpahannya ialah gibsit, hematit, goetit, kaolinit dan kuarza. Korelasi negatif yang
kuat antara Fe2O3 lawan Al2O3 dan Al2O3 lawan TiO2 mencadangkan pertambahan Al2O3 membentuk
gibsit akan diikuti dengan pengurangan goetit dan anatas. Purata kepekatan masing-masing bagi Cr,
Zn, Ni dan Cu dalam konkresi ialah 611 ppm, 35 ppm, 35 ppm dan 28 ppm. Korelasi positif yang
ditunjukkan oleh plot graf Ni lawan Zn, Ni lawan Cu dan Zn lawan Cu dalam konkresi mencadangkan
asosiasi unsur-unsur tersebut dalam bauksit, terutamanya dalam mineral gibsit dan goetit. Cr
kemungkinan dijerap dalam gibsit, Fe-oksida dan kaolinit, dan juga boleh terdapat dalam kromit
Geochemical characterization of volcanic soils from Tawau, Sabah
No full textThis paper discusses the geochemical characteristics of volcanic soils from Tawau, Sabah. The concentration of major elements and trace elements were determined using XRF analysis whereas mineralogical studies were carried out using XRD and SEM techniques. The results of the analyses show that SiO2 and Al2O3 are abundant in volcanic soils with concentrations from 43.06% - 67.96% and 12.55% - 29.92%, respectively. The concentration of Fe2O3 is next in abundance with the concentration of between 6.82% and 11.29%. The concentrations of CaO, K2O, MgO, Na2O, P2O5, and TiO2 are less than 5%. The high concentrations of SiO2 and Al2O3 are due to the high abundances of vermiculite and quartz as detected from XRD, while the high concentration of Fe2O3 is due to the presence of geothite. The average concentrations for Ba, V, Zr and Zn in volcanic soils are 341 ppm, 315 ppm, 239 ppm, and 124 ppm, respectively. The strong correlations between Zn and Al2O3, Fe2O3 and SiO2, indicate that Zn is being adsorbed by secondary minerals especially vermiculite and goethite
Heavy metals migration through the clayey soil from Telipok, Sabah
No full textThe migrations of heavy metals namely Cu, Cr, Ni, Pb and Zn through the soil from weathered rock of the
Crocker Formation in Telipok, Sabah were studied by means of leaching test. The leaching test conducted on soil
samples shows that most of the heavy metals are retained at the top part of the leaching columns i.e. at the depth of 1.0
cm. All of the heavy metals concentration decreased with the increasing depth within the soil profiles. The leachate
analysis indicated that all of the heavy metals except Pb achieved the breakthrough curves at the fIrst 4 pore volume (PV).
The breakthrough curve for Pb was achieved after 5 PV of leaching. From this study, based on the breakthrough curves
and mass balance calculation, it can be concluded that variation occurs during migration or mobilisation of heavy metals.
After leaching 7 PV of solution, the relative concentration (Ci/Co> of Cu, Cr, Ni, Pb and Zn are maintained at 0.90, 0.82,
0.98,0.94, and 0.80 respectively. The data obtained indicates that Zn has high mobility followed by Cu, Ni, Cr, and
Pb. At the end of the leaching test, the microstructural study showed the occurrence of micro cracks, high pore spaces
and the forming of channels at the top part of the columns. Whereas, the bottom part shows tight structure with low pore
spaces and low form of channels
Kajian perlakuan larut lesap Cu, Cr, Ni, Pb dan Zn dalam tanah laterit dari Ranau, Sabah
No full textPerlakuan larut resap logam-logam berat iaitu Cu, Cr, Ni, Pb, dan Zn dalam tanah laterit dikaji dengan
menggunakan ujian larut lesap. Sampellaterit dilarut lesapkan dengan asid pH 3.2 pada tekanan 15 psi. Kandungan
kelimpahan logam-Iogam berat dalam laterit dan cecair larut resapan dianalisis menggunakan kaedah spektrometer
serapan atom (AAS). Keputusan analisis profil migrasi bagi logam-logam Ni, Cr, Cu, Pb dan Zn menunjukkan nilai yang
lebih tinggi pada bahagian bawah profillaterit. Ini menunjukkan ada berlakunya migrasi atau larut lesap logam-Iogam
daripada bahagian atas kebahagian bawah. Ini juga disokong oleh analisis kandungan kepekatan cecair larut resap yang
mana menunjukkan kandungan Cr dan Ni yang tinggi. Profil migrasi bagi Cu, Pb, dan Zn pula didapati sangat rendah
kandungannya dalam cecair larut lesap kerana nilai dalam tanah lateritik asal yang sangat rendah. Analisis struktur
miktro dalam tanah asal laterit menunjukkan kehadiran mineral bersudut yang kebanyakannya terdiri daripada goethit,
hematit dan gibsit. Mineral-mineral tersebut didapati mengalami proses pelarutan dan jelas ditunjukkan oleh struktur
permukaan yang berubah menjadi sub-bulat oleh mikrograf elektron pengimbas (SEM)
Effect of lime on stabilization of mining waste from Sabah, malaysia
No full textThis paper deals with the effect of lime on stabilization of mining waste from Sabah, Malaysia. In this study, different percentages of lime as well as fine material were added as additive with the mining waste. The engineering properties were measured by compaction test, unconfined compressive strength tests and permeability tests. The mineral identification and microstructure were examined using X-ray diffraction (XRD) and Scanning Electron Microscopic (SEM). The compaction test indicated that the optimum moisture content varied with amount of lime content. The virgin mining waste showed low unconfined compressive strength value due to the very low cementing agent. The samples showed a rapid increase in shear strength when stabilized with lime content ranging from 2 to 8%. The rate of increase in strength is most rapid within two weeks of interaction. This is due to the pozzolanic reaction, which created more rigid - packed structure and small pore space at lime content as low as 2%. More addition of lime had increased the unconfined compressive strength due to the intensive pozzolanic reactions forming more cementitious mineral and created bridge-like structure. However the optimum percentage of lime required was 6% based on the unconfined compressive strength. Lime content in excess of the optimum (8% of lime) acted as filler or lubricant. Significant reduction in permeability to 1 x 10-7 m/s was observed at the end of the leaching test. This is due to the development of cementitious minerals and clogging of fine particle size in the pore spaces
Penilaian terhadap pencemaran tanah di kawasan penanaman sayur-sayuaran tanah tinggi, di kawasan Kundasang Sabah
No full textSampel-sampel tanah dari tiga batuan induk yang berbeza di Kundasang Sabah telah
dianalisis untuk menentukan kandungan logam-Iogam berat (As, Co, Cr, Cu, Mn, Pb, V
dan Zn) menggunakan teknik Pendarffour Sinar-X (XRF). HasiJ analisis menunjukkan
bahawa kepekatan purata logam-Iogam berat seperti Zn, V, Mn dan Cr tinggi dalam
ketiga-tiga jenis tanah berbanding dengan paras kepekatan yang selamat. Kepekatan
purata bagi Zn ialah 85ppm, 88ppm dan 137ppm masing-masing dari tanah Formasi
Trusmadi, tanah Formasi Crocker dan tanah dari Gravel Pinousuk. Kepekatan purata
bagi V pula ialah 109ppm, 126ppm dan 123ppm masing-masing dari tanah Formasi
Trusmadi, tanah Formasi Crocker dan tanah dari Gravel Pinousuk. MnO menunjukkan
kepekatan yang tertinggi iaitu 7000ppm, 5000ppm dan 7000ppm masing-masing dari
tanah Formasi Trusmadi, tanah Formasi Crocker dan tanah dari Gravel Pinousuk.
Kepekatan bagi dari tanah tanah Formasi Trusmadi, tanah Formasi Crocker dan tanah
dari Gravel Pinousuk pula masing-masing 113ppm, 137ppm dan 129ppm. Kepekatan
Cu (62ppm) pula lebih tinggi berbanding dengan paras merbahaya dalam tanah Gravel
Pinousuk sahaja, manakala dalam Formasi Trusmadi (40ppm) dan Formasi Crocker
(39ppm) pula kepekatan logam berat berada dalam keadaan normal. As, Co, Ni dan Pb
dalam tanah berada dalam paras yang normal yang dianggap selamat di ketiga-tiga
formasi. Kajian korelasi yang jelas antara logam berat dengan bahan organik, mineral
sekunder (A120 3 dan Fe20JJ, pH dan MnO tanah menunjukkan ketiga-tiga 'aidor diatas
mengawal kepekatan dan perlakuan logam-Iogam berat. Korelasi logam berat dengan
peratus saiz butiran tanah menunjukkan saiz lempung mengawal logam berat tersebut
(As, Cr, Ni dan Pb), manakala sebaliknya bagi saiz pasiran. Secara umumnya bolehlah
dikatakan bahawa punca-punca logam berat dalam tanah adalah tinggi dalam tanah
yang berasal daripada Gravel Pinousuk. Manakala tanah yang asalannya dari Formasi
Crocker dan Formasi Trusmadi agak rendah walaupun ada juga unsur tertentu yang
tinggi. Walau bagaimanapun kepekatan yang tinggi da/am tanal; tersebut adalah
jumlah keseluruhan logam beraLter:sebut dan tidak menggambarkan jumlah yang akan
diambil oleh tumbuh-tumbuhan. Jadi untuk mempastikan jumlah yang diambil oleh
tumbuhan maka kajian lanjut dalam sampel tumbuhan perlu dijalankan
Effect of leaching on lime stabilised contaminated soil and mining waste
No full textDegradation of environment due to industrial and mining related activities is identified as one of the major problem facing by most industrial and developing countries. Therefore, scientific research are needed to acquire knowledge to manage such toxic waste, which has a potential to degrade on the environment as well as on human health. Leaching column tests were conducted on two soil samples and one mining waste sample in order to investigate the potential of lime stabilisation technique to immobilise heavy metals. The soil samples were obtained fiom Kg. Kayumadang, Telipok, Sabah (KMT) and Kg. Bongkud, Ranau, Sabah (KGB), whereas the mining waste was obtained from Lohan Dam, Ranau, Sabah (LDA). The amounts of lime used for the stabilisation were 2%, 4%, 6%, and 8% of dry weight. Five selected heavy metals namely Cu, Cr, Ni, Pb, and Zn were chosen to understand their behavioural changes with the long term leaching process. These heavy metals were spiked into the unstabilised and lime stabilised samples in the leaching columns. The pH values of leachate from all stabilised KMT, KGB, and LDA samples were found to be alkaline, indicating that the heavy metals were adsorbed on the surface of the cementitious minerals, whilst the Ca ions were released from the cementitious compound. The trend of migration profiles showed that the concentrations of the heavy metals decreased with depth for all samples. On the other hand, very low concentrations of heavy metals were detected in the leachate of the lime stabilised samples. Mass balance calculations showed that Zn had the highest mobility in KMT sample, whereas Ni was the highest in KGB and LDA samples, Calculations also showed that Pb was the least mobile in KMT, whereas Cr was the slowest in both KGB and LDA samples. The permeability of all stabilised samples decreased significantly immediately after leaching processes due to the clogging of pore by fine materials and the development of cementitious mineral. Scanning electron microscope (SEM) study showed that the bottom part of the leached columns had tights structure with low pore spaces, which were clogged-up by fine materials. Using X-ray diffraction (XRD) technique, quartz, kaolinite, feldspar and cementitious minerals were detected in the stabilised samples. Nevertheless, SEM method illustrated better image of the cementitious mineral. Soil classification tests, chemical characterisations, mineralogical identifications, and engineering properties verification were also performed on both unstabilised and stabilised samples to examine the liming effect on their properties. Maximum unconfined compressive strength (UCS) was achieved by adding 6% lime to the KMT, KGB, and LDA samples, and this strength increased with age. Based on the leaching column and UCS tests, 6% lime is suggested as the optimum value for stabilisation of KMT and KGB samples. Hence, lime stabilised KMT and KGB could be used as a clay liner due to their low permeability and high strength. It is also possible to stabilise LDA with 6% lime with the addition of fine material to facilitate stabilisation process, thus irnmobilising heavy metals within the stabilised mining waste
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