Malaysian fisheries policy : Search for new grounds

Past fisheries development policies in Malaysia are assessed and new grounds for managing the Malaysian fisheries are explored. Some incompatibility in the goals for fishery development are discerned, especially those of increasing domestic landings through mechanization and resource conservation. Future management efforts should be based on a fuller understanding of the fishery stock and regional management of fish stocks. Aquaculture is often seen as a plausible alternative in order to augment supplies from the capture fisheries. A comprehensive multidisciplinary approach is needed to transform and commercialize traditional, experience-dependent culture systems into technology-packaged systems based on scientific methods. There is also substantial potential for the development of recreational fisheries.     

Micro-CT and FIB–SEM imaging and pore structure characterization of dolomite rock at multiple scales

With improvements of imaging techniques and computational power, Digital Rock Physics (DRP) has been increasingly used to determine transport and elastic properties of reservoir core plugs. Since numerical computations highly rely on accurate 3D representations of the porous microstructure of the rocks, the imaging technique and the scale at which the imaging is performed is a critical parameter. In this paper, we introduce a multiscale imaging workflow that uses both micro-X-ray tomography (micro-XCT) and focused ion beam combined with scanning electron microscope (FIB–SEM) to characterize a dolomite rock from the microscale to the nanoscale. This allows for the accurate capture of the different heterogeneities that exist in the carbonate (texture, mineralogy, pore size). The reconstructed microporous structures were then used to successfully predict elastic and permeability properties of selected carbonate.     

TM/ETM+/LDCM Images for Studying Land Surface Temperature (LST) Interplay with Impervious Surfaces Changes over Time Within the Douala Metropolis,Cameroon

Douala, the most important metropolis of Cameroon, is a sub-Saharan wet coastal environment of which the anarchic urbanization is a socio-economic and environmental problem, significantly influencing the local climate. In this study, three Landsat images from 1986 (TM), 2007 (ETM+) and 2016 (LDCM), were utilized to investigate the effect of this urbanization on the increasing land surface temperature (LST) between these dates. Thus, the urban indices (UI), determined from the Landsat Visible and NIR channels were used to identify impervious areas (Urban Fabric and bare soil) of urban area. It has been shown from the UI images that, impervious areas have been increased from 1986 to 2016. The LST images derived have a continual expansion of zones and points of heat throughout these dates. The correlation analysis of LST and UI, at the pixel-scale, indicated the positive relationship between these parameters, which could show a real impact of urbanization on the increasing temperature in the area. These correlations are fairly low in 1986 (maximum R-square value is about 0.35) and in 2007 (maximum R-square value is about 0.44. In 2016, a high positive correlation (maximum R-square value is about 0.77) confirm that, the impervious areas strengthen the temperature and the Urban Heat Island effect in Douala urban zone. Overall, the earth observation images and the geographic information system techniques were effective approaches for aiming at environment monitoring and analyzing urban growth patterns and evaluating their impacts on urban climates.     

Dimensional Reduction of Pattern-Based Simulation Using Wavelet Analysis

A pattern-based simulation technique using wavelet analysis is proposed for the simulation (wavesim) of categorical and continuous variables. Patterns are extracted by scanning a training image with a template and then storing them in a pattern database. The dimension reduction of patterns in the pattern database is performed by wavelet decomposition at certain scale and the approximate sub-band is used for pattern database classification. The pattern database classification is performed by the k-means clustering algorithm and classes are represented by a class prototype. For the simulation of categorical variables, the conditional cumulative density function (ccdf) for each class is generated based on the frequency of the individual categories at the central node of the template. During the simulation process, the similarity of the conditioning data event with the class prototypes is measured using the L ₂-norm. When simulating categorical variables, the ccdf of the best matched class is used to draw a pattern from a class. When continuous variables are simulated, a random pattern is drawn from the best matched class. Several examples of conditional and unconditional simulation with two- and three- dimensional data sets show that the spatial continuity of geometric features and shapes is well reproduced. A comparative study with the filtersim algorithm shows that the wavesim performs better than filtersim in all examples. A full-field case study at the Olympic Dam base metals deposit, South Australia, simulates the lithological rock-type units as categorical variables. Results show that the proportions of various rock-type units in the hard data are well reproduced when similar to those in the training image; when rock-type proportions between the training image and hard data differ, the results show a compromise between the two.     

Surface-rupturing history of the Bree fault scarp, Roer Valley graben: Evidence for six events since the late Pleistocene

Since 1996 paleoseismological investigations have been used to develop the surface- rupturing history of the Bree fault scarp, the morphologically best-defined segment of the southwestern border fault of the Roer Valley graben in northeastern Belgium. The first studies determined that the escarpment is associated with a surface fault, and they exposed evidence for three surface displacements since about 40 ka BP. The most recent eventprobably occurred between 1000 and 1350 yr cal BP. Geophysical and trenching studies at a new site near the southeastern end of the fault scarp reconfirmed the coincidence of the frontal escarpment with a shallow normal fault, which displaces the Middle Pleistocene `Main Terrace' of the Maas River, as well as overlying coversands of Saalian to late Weichselian age. Different amounts of displacement shown by the two youngest coversand units indicate two discrete faulting events, but primary evidence for the coseismic nature of these events is sparse. Radiocarbon and optically stimulated luminescence dating constrainthe age of these events to the Holocene and between 14.0 ± 2.3 ka BP and 15.8 ± 2.9 ka BP, respectively. In addition, four older surface-rupturing events are inferred from the presence of four wedge-shaped units of reworked Main Terrace deposits that are interbedded with coversand units in the hanging wall of the trench and in shallow boreholes. These wedges are interpreted as colluvial wedges, produced by accelerated slope processes in response torejuvenation of the fault scarp, most probably in a periglacial environment. Luminescence dating indicates that five out of a total of six identified faulting events are younger than 136.6 ± 17.6 ka. The antepenultimate event was the largest faulting event, associated with a total fault displacement in excess of 1 m. Thus, the newly investigated trench site represents the longest and most complete record of surface rupturing recovered so far along the Bree fault scarp. This study also demonstrates the viability of the paleoseismological approach to identify past large earthquakes in areas of present-day moderate to low seismic activity.     

Substructure design optimization and nonlinear responses control analysis of the mega-sub controlled structural system(MSCSS) under earthquake action

The newly proposed mega sub-controlled structure system(MSCSS) and related studies have drawn the attention of civil engineers for practice in improving the performance and enhancing the structural effectiveness of mega frame structures. However, there is still a need for improvement to its basic structural arrangement. In this project, an advanced, reasonable arrangement of mega sub-controlled structure models, composed of three mega stories with different numbers and arrangements of substructures, are designed to investigate the control performance of the models and obtain the optimal model configuration(model with minimum acceleration and displacement responses) under strong earthquake excitation. In addition, the dynamic parameters that affect the performance effectiveness of the optimal model of MSCSS are studied and discussed. The area of the relative stiffness ratio RD, with different mass ratio MR, within which the acceleration and displacement of the optimal model of MSCSS reaches its optimum(minimum) value is considered as an optimum region. It serves as a useful tool in practical engineering design. The study demonstrates that the proposed MSCSS configuration can efficiently control the displacement and acceleration of high rise buildings. In addition, some analytical guidelines are provided for selecting the control parameters of the structure.     

Surface water quality contamination source apportionment and physicochemical characterization at the upper section of the Jakara Basin, Nigeria

The present study investigates the surface water quality of three important tributaries of Jakara Basin, northwestern Nigeria to provide an overview of the relationship and sources of physicochemical and biological parameters. A total of 405 water samples were collected from 27 sampling points and analyzed for 13 parameters: dissolved oxygen (DO), 5-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), suspended solids (SS), pH, ammonia-nitrogen (NH₃NL), dissolved solids (DS), total solids (TS), nitrates (NO₃), chloride (Cl), phosphates (PO₄), Escherichia coli (E. coli) and fecal coliform bacteria (FCB). Pearson’s product–moment correlation matrix and principal component analysis (PCA) were used to distinguish the main pollution sources in the basin. Four varimax components were extracted from PCA, which explained 84.86, 83.60, and 78.69 % of the variation in the surface water quality for Jakara, Tsakama, and Gama-Kwari Rivers, respectively. Strong positive loading included BOD₅, COD, NH₃NL, E. coli, and FCB with negative loading on DO attribute to a domestic waste water pollution source. One-way ANOVA revealed that there was no significant difference in the mean of the three water bodies (p?>?0.05). It is therefore recommended that the government should be more effective in controlling the point source of pollution in the area.     

Two-stage reverse flotation process for removal of carbonates and silicates from phosphate ore using anionic and cationic collectors

Phosphate rock contains various gangue minerals including silicates and carbonates which need to be reduced in content in order to meet the requirements of the phosphate industry. Froth flotation has become an integral part of phosphate concentration process. In this study, double reverse flotation was applied to recover apatite from phosphate ore. H₃PO₄ and CaO were used as phosphate depressants, in acidic and alkaline conditions. Fatty acids and amines were added as carbonate and silicate collectors respectively. An experimental protocol devised to optimize the grade and recovery of phosphate using anionic–cationic method was found effective. Consequently, a required high quality of phosphate concentrate containing 30.1% P₂O₅ was obtained, with a recovery of 94%. X-ray diffraction and optical microscopy studies were performed to define the main minerals.     

Qualité des eaux du cours principal de la Medjerda (Tunisie et Algérie) et trois de ses affluents Nord

Résumé

Une étude a été effectuée dans la zone Nord-Ouest du bassin versant de la Medjerda avec pour objectif de fournir de nouvelles connaissances sur la qualité des eaux ainsi que sur le type de relation qui peut exister entre les variables physico-chimiques, bactériologiques et les indices de diversité/densité de la méiofaune. Les résultats montrent une dégradation de la qualité du cours principal de la Medjerda et de trois de ses affluents Nord (augmentation de la salinité, teneur en nitrate, matière organique, coliformes…). Les indices de diversité et d’équitabilité suivent cette évolution régressive des variables physico-chimiques et apportent de nouvelles connaissances sur le type et la qualité du sédiment.

Editeur Z.W. Kundzewicz ; Editeur associé B. Touaïbia     

Observations of sea ice interannual variations and spring bloom occurrences at the Japanese scallop farming area in the Okhotsk Sea using satellite imageries

The dynamics of ice formation and phytoplankton bloom development in the coastal region of the Okhotsk Sea, Hokkaido, where the Japanese scallop, Mizuhopecten yessoensis, are cultured were investigated using seven years (1998–2004) satellite data from the Special Sensor Microwave/Imager (SSM/I) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS). The interannual variability of sea ice cover and timing of spring bloom occurrences were analyzed. Longer ice cover in 1999, 2001 and 2003 with the presence of ice until early April and shortened ice cover in 1998, 2000, 2002 and 2004 with the occurrence of ice until early March were recognized at this area. Variability in the timing of sea ice retreat and development of spring blooms at the scallop areas were observed. Progression of a single ice edge bloom showed higher Chl-a concentration compared to development of an initial ice edge bloom followed by a later open water bloom. Higher concentration of phytoplankton biomass was observed in the initial bloom when sea ice melting is delayed compared to when the sea ice leaves earlier. Wind events were also observed to affect the occurrences of spring bloom.