Evaluating Land Surface Changes of Makassar City Using DInSAR and Landsat Thematic Mapper Images

Urban growth has been a major issue in environmental monitoring and changes occurred on land surfaces have been monitored by applying remote sensing as well as ground measurement. Most major cities in the world have experienced land subsidence phenomena on some parts of them due to the load of development and modernization. Excessive extraction of groundwater for the needs of industry has led to the condition where the water table drops, and this can possibly trigger subsidence, as observed in Indonesian cities. In this study the authors have shown that the application of DInSAR （differential interferometric synthetic aperture radar） technique using Japanese Earth Resources Satellite-I Synthetic Aperture Radar JERS-I SAR data can reveal subsidence conditions in the studied Makassar city area. Landsat TM （thematic mapper） images were used to evaluate the change of land cover during the observation period of 1994-1999. Makassar is fiat, covered mainly by alluvium deposit that is vulnerable to the load of constructions, and volcanic formations which is porous and will easily be degraded by groundwater extraction. It is found that mostly the subsidence has occurred in the western part of the city, including the industrial district, reclamation area, trading center area and the seaport area. The ground survey has indicated that high human activity exists in every point of subsidence. It is likely that various human activities such as ground water pumping and construction work should have affected the local subsidence phenomena in Makassar, as in the case of other large-scale cities in Indonesia.     

Structural development and magnetic phenomenon in Zn–Cr–Fe multi oxide nano-crystals

The Cr³⁺ ions doped multi-oxide ZnFe_2−xCr_xO₄ ferrite nanoparticles have been synthesized by chemical co-precipitation method. Site occupancies of Zn²⁺, Cr³⁺ and Fe³⁺ ions were analyzed using X-ray diffraction data and Buerger's method. The effect of the constituent phase variation on the magnetic hysteresis behavior was examined by saturation magnetization which decreases with the increase in Cr³⁺ content in place of Fe³⁺ ions at octahedral B-site. Typical blocking temperature (T_B) around 90 K was observed by zero field cooling and field cooling magnetization study. Room temperature Mössbauer spectra show two paramagnetic doublets (tetrahedral and octahedral sites). The isomer shifts of both doublets decrease whereas quadrupole splitting and relative area of tetrahedral A-site increases with increasing Cr³⁺ substitution. The dielectric constant (measured on compositions x=0, 0.4, 0.8 and 1.0) increases when the temperature increases as in the semiconductor. This behavior is attributed to the hopping of electrons between Fe²⁺ and Fe³⁺ ions with a thermal activation.     

Simulation of producer gas flameless combustion with fresh reactant diluted by hot flue gas

Flameless combustion is considered as a flexible and efficient combustion process for low heating value gas fuel. This paper presents numerical simulations of premixed flameless combustion using producer gas as a fuel. Different initial conditions of the premixed fresh reactant (air/fuel mixture) and dilution levels are taken into account for the investigation. The numerical simulations were investigated using a network of chemical reactor models with the detailed reaction mechanism of GRI‐Mech 3.0. A threshold dilution level for flameless combustion fuelled by producer gas was determined. The numerical results show that dilution of the fresh reactant with hot combustion products and initial fresh reactant temperature play important roles in flameless combustion formation and its auto‐ignition behaviour, rather than equivalence ratio of the fresh reactant. In the flameless combustion regime, temperature and chemical concentrations were reduced while chemical kinetics process was decelerated, resulting in delay of the auto‐ignition process.     

Irradiation induced texturing in the Mg0.95Mn0.05Fe2O4 ferrite thin film

We present a study on the effect of swift heavy ions irradiation on the structural and magnetic properties of Mg_0.95Mn_0.05Fe₂O₄ ferrite thin film grown by pulsed laser deposition technique. X-ray diffraction (XRD) pattern of the as-deposited film reveals a cubic spinel structure with an intermediate phase of α-Fe₂O₃. This impurity phase completely dissolves upon irradiation with 200 MeV Ag¹⁵⁺-ions and it exhibits a strong crystallographic texture along the (440) plane. The magnetization values start increasing systematically with irradiation at lower fluence values, whereas decrease for higher one. This decrease in magnetic signal can be attributed to partial amorphization caused by irradiation in agreement with XRD and atomic/magnetic force microscopic images.     

Moessbauer spectra of MnFe2-2x Al2xO4 （0 ≤x≤ 0.4） ferrites

The effect of non-magnetic Al³⁺ ion doping on the magnetic properties of MnFe_2−2x Al_2x O₄ (0≼x≼0.4) spinel ferrites was studied using M?ssbauer spectroscopy measurements at room temperature. From the M?ssbauer study, it is observed that the resolved hyperfine sextets are due to the distribution of Fe ions on the two sublattices of the spinel ferrites. The value of the isomer shift obtained from the fitting of the M?ssbauer spectra indicates that Fe ions are in +3 state. A paramagnetic doublet is observed at degree of inversion x=0.4, superimposed on the hyperfine sextets, indicating that the super-exchange interaction A–B decreases due to the dilution of sublattice by Al³⁺ ions. The hyperfine magnetic field decreases at both interstitial sites of tetrahedral (A) and octahedral (B) with the increase in Al concentration.     

Influence of Ti^4＋ doping on hyperfine field parameters of Mg0.95Mn0.05Fe2-2xTizxO4 （0 ≤x ≤ 0.7）

The mixed spinel ferrite system Mg_0.95Mn_0.05Fe_2−2x Ti_2x O₄ (0⩽x⩽0.7) was synthesized by the conventional solid-state reaction technique. The effect of Ti⁴⁺ doping was studied by using the M?ssbauer spectroscopy measurements at room temperature. From the analysis of the M?ssbauer spectra, it is observed that s-electron density, electric field gradient (EFG), quadrupole coupling constant (QCC) and the net hyperfine magnetic fields acting on the M?ssbauer nuclei-Fe_A ³⁺ and Fe_B ³⁺ change with the increase of Ti⁴⁺ doping in Mg_0.95Mn_0.05Fe₂O₄. The hyperfine magnetic field decreases with the increase of Ti⁴⁺ doping.     

Study of structural and magnetic properties of (Co–Cu)Fe2O4/PANI composites

The nanocomposites of the polyaniline and Co_1−xCu_xFe₂O₄ (PANI/CoCuFe) were prepared by in-situ oxidative polymerization of aniline. Prepared nanocomposites samples were characterized by using various experimental techniques like X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), Mössbauer spectroscopy and ultraviolet–visible spectrophotometry (UV–VIS). The elemental analysis as obtained from the energy dispersive X-ray spectroscopy (EDAX) measurement is in close agreement with the expected composition from the stoichiometry of the reactant solutions. XRD result confirms that all the samples have the single phase cubic spinel structure. Unit cell parameter ‘a’ is found to decrease with the increase in copper ion substitution. The crystallite size was investigated by using the Debye–Scherer formula and it was found in the range of ∼28–37 nm. FE-SEM confirmed the homogeneous and well defined surface morphology of the synthesized samples. FT-IR study showed the main absorption bands corresponding to the spinel structure those arose due to the tetrahedral and octahedral stretching vibrations. Cation distribution was estimated using XRD data. Hysteresis measurements revealed that the saturation magnetization decreased with increase in Cu²⁺ substitution. Magnetic environment of ⁵⁷Fe in Cu-doped cobalt ferrite was investigated by using Mössbauer spectroscopy. Mössbauer study evidenced the ferrimagnetic behavior of the synthesized samples.     

Gasification of lignocellulosic biomass in fluidized beds for renewable energy development: A review

A literature review on gasification of lignocellulosic biomass in various types of fluidized bed gasifiers is presented. The effect of several process parameters such as catalytic bed material, bed temperature and gasifying agent on the performance of the gasifier and quality of the producer gas is discussed. Based on the priorities of researchers, the optimum values of various desired outputs in the gasification process including improved producer gas composition, enhanced LHV, less tar and char content, high gas yield and enhanced carbon conversion and cold gas efficiency have been reported. The characteristics and performance of different fluidized bed gasifiers were assessed and the obtained results from the literature have been extensively reviewed. Survey of literature revealed that several industrial biomass gasification plants using fluidized beds are currently conducting in various countries. However, more research and development of technology should be devoted to this field to enhance the economical feasibility of this process for future exploitations.     

Genetic Isolation among the Northwestern,Southwestern and Central-Eastern Indian Ocean Populations of the Pronghorn Spiny Lobster Panulirus penicillatus

The pronghorn spiny lobster Panulirus penicillatus is a highly valuable species which is widely distributed in Indo-West Pacific and Eastern Pacific regions. Mitochondrial DNA control region sequences (566–571 bp) were determined to investigate the population genetic structure of this species in the Indian Ocean. In total, 236 adult individuals of Panulirus penicillatus were collected from five locations in the Indian Ocean region. Almost all individuals had a unique haplotype. Intrapopulation haplotype (h) and nucleotide (π) diversities were high for each locality, ranging from h = 0.9986–1.0000 and π = 0.031593–0.043441. We observed distinct genetic isolation of population located at the northwestern and southwestern edge of the species range. Gene flow was found within localities in the central and eastern region of the Indian Ocean, probably resulting from an extended planktonic larval stage and prevailing ocean currents.     

Electronic structure and magnetic properties of the Ni0.2Cd0.3Fe(2.5-x)A1(x)O4 (0 < or = x < or = 0.4) ferrite nanoparticles

The structural, magnetic, and electronic structural properties of Ni0.2Cd0.3Fe(2.5-x)Al(x)O4 ferrite nanoparticles were studied via X-ray diffraction (XRD), transmission electron microscopy (TEM), DC magnetization, and near-edge X-ray absorption fine-structure spectroscopy (NEXAFS) measurements. Nanoparticles of Ni0.2Cd0.3Fe(2.5x)Al(x)O4 (0 < or = x < or = 0.4) ferrite were synthesized using the sol-gel method. The XRD and TEM measurements showed that all the samples had a single-phase nature with a cubic structure, and had nanocrystalline behavior. From the XRD and TEM analysis, it was found that the particle size increases with Al doping. The DC magnetization measurements revealed that the blocking temperature increases with increased Al doping. It was observed that the magnetic moment decreases with Al doping, which may be due to the dilution of the sublattice by the doping of the Al ions. The NEXAFS measurements performed at room temperature indicated that Fe exists in a mixed-valence state.