This paper investigated the throughput performance of a secondary user (SU) for a random primary user (PU) activity in a realistic experimental model. This paper proposed a sensing and frame duration of the SU to maximize the SU throughput under the collision probability constraint. The throughput of the SU and the probability of collisions depend on the pattern of PU activities. The pattern of PU activity was obtained and modelled from the experimental data that measure the wireless local area network (WLAN) environment. The WLAN signal has detected the transmission opportunity length (TOL) which was analyzed and clustered into large and small durations in the CTOL model. The performance of the SU is then analyzed and compared with static and dynamic PU models. The results showed that the SU throughput in the CTOL model was higher than the static and dynamic models by almost 45% and 12.2% respectively. Furthermore, the probability of collisions in the network and the SU throughput were influenced by the value of the minimum contention window and the maximum back-off stage. The simulation results revealed that the higher contention window had worsened the SU throughput even though the channel has a higher number of TOLs.
Microalgae are considered promising feedstock for the production of biofuels and other bioactive compounds, yet there are still challenges on commercial applications of microalgae-based products. This review focuses on the economic analysis, environmental impact, and industrial potential of biofuels production from microalgae. The cost of biofuels production remains higher compared to conventional fuel sources. However, integration of biorefinery pathways with biofuels production for the recovery of value-added products (such as antioxidants, natural dyes, cosmetics, nutritional supplements, polyunsaturated fatty acids, and so forth) could substantially reduce the production costs. It also paves the way for sustainable energy resources by significantly reducing the emissions of CO2 , NOx , SOx , and heavy metals. Large-scale biofuels production has yet to be successfully commercialized with many roadblocks ahead and heavy competition with conventional fuel feedstock as well as technological aspects. One of the prominent challenges is to develop a cost-effective method to achieve high-density microalgal cultivation on an industrial scale. The biofuels industry should be boosted by Government's support in the form of subsidies and incentives, for addressing the pressing climate change issues, achieving sustainability, and energy security.
The emergence of wireless technologies such as WirelessHART and ISA100 Wireless for deployment at industrial process plants has urged the need for research and development in wireless control. This is in view of the fact that the recent application is mainly in monitoring domain due to lack of confidence in control aspect. WirelessHART has an edge over its counterpart as it is based on the successful Wired HART protocol with over 30 million devices as of 2009. Recent works on control have primarily focused on maintaining the traditional PID control structure which is proven not adequate for the wireless environment. In contrast, Internal Model Control (IMC), a promising technique for delay compensation, disturbance rejection and setpoint tracking has not been investigated in the context of WirelessHART. Therefore, this paper discusses the control design using IMC approach with a focus on wireless processes. The simulation and experimental results using real-time WirelessHART hardware-in-the-loop simulator (WH-HILS) indicate that the proposed approach is more robust to delay variation of the network than the PID.
In order to manage blue swimming crabs in Pangkajene Kepulauan, management measures are required. Since the environment which affects the abundance of the blue swimming crab varies seasonally, it is necessary to take into account the seasonal nature with the aim of developing a management strategy. The objectives of this study are to define the abundance of and fishing season of blue swimming crabs in the Pangkajene Kepulauan waters, South Sulawesi, Indonesia. The fishing season was analysed using seasonal index analysis, while fish abundance was analysed by means of Equilibrium-Schaefer. The result of this study demonstrated that fishermen allocate their fishing gear all year, although the fish catch is seasonal. Based on analysis of the result, the fishing season for the blue swimming crabs is short. The peak fishing season starts in May and finishes in June. However, in order to enable their families to earn a living, fishermen operated their fishing gear throughout the year. As a result, both catch landing and effort were close to maximum sustainable yield (MSY). In order to reduce fishing pressure, it is necessary to reduce fishing gear and have a seasonal arrangement regarding fishing gear allocation.
In recent years, the utility grid system is more essential for the power
transmission and distribution system because it cannot produce harmful
gases or no discharge waste in the environment. PWM based phase
synchronous invert systems are generally utilised in the high efficiency
energy supply, long distance and higher power quality. The inverter output
voltage depends on the coupling transformer, input sources and invert
controllers. An inverter using a three leg IGBT has been designed for utility
grid and simulated by using MATLAB2014a. In this paper, both sides of
the LCL filters are used for removing the DC ripple current, reducing the
noise and synchronous the output phase between inverter and the utility
grid. The PWM controller has created pulse signal to control the inverter,
electronic switches and precisely synchronise with grid line frequency. In
this system, the input DC voltage 500V, switching frequency 1.65 kHz, grid
frequency 50Hz, 20 km feeder (resistance, inductance and capacitance per
unit length, which are 0.1153, 1.05e-3 and 11.33e-09 ohms/km) with 30MW
three phase load (active and inductive reactive power which are 30e6 W
and 2e6 var) and also a balanced utility grid load of star configuration (00,
1200, and 2400 degree) are considered in the design. On the other hand,
three phase transformer consists of three signal phase transformers, normal
power 100e3, magnetization resistance and inductance which are 500 pu and
416.67pu are considered in this design. The system conversion efficiency
is 99.94% and 99.96%, while the total THD are 0.06% on inverter side
and 0.04% on grid side.
Remote sensing and geographic information system techniques are significant and popular approaches that have been used in recent years to measure and map urban growth patterns. This paper primarily aims to provide a basis for a literature review of urban growth measurement and mapping by using different methods. For this purpose, the general characteristics of measuring and mapping urban growth patterns are described and classified. The strengths and weaknesses of the various methods have been identified from an analysis and discussion of the characteristics of the techniques. Results of reviews confirm that combining quantitative and qualitative techniques, such as Shannon approach and change detection, to measure and map urban growth patterns will improve understanding of the phenomenon of urban growth. Moreover, using social and economic data such as population and income data will improve understanding of the relationships between causes and effects. The integration of social and economic factors with quantitative and qualitative techniques will contribute to a perfect evaluation of urban growth patterns and land use changes, taking technical, social, economic, spatial, and temporal factors into account.
Contaminated and ageing transmission line insulators often suffer from temporary or permanent loss of their insulating properties due to flashover resulting in power system failure. Surface discharges are precursors to flashover. To pre-empt any occurrence of flashovers, utility companies monitor the conditions of their insulators. There are numerous insulator surface monitoring techniques such as Leakage Current, Acoustics, and Infrared. However, these techniques may not be suitable for in-situ condition monitoring of the insulators as they are prone to noise, affected by environmental conditions or contact methods. Monitoring of the UV signals emitted by the surface discharges of these insulators has been reported to be a promising technique. However, comprehensive studies on this technique is lacking, especially on aged insulators. This paper investigated the UV signals of contaminated and aged insulators detected during surface discharge activities using UV pulse method. The time and frequency domain of the UV signals were analysed for a group of insulator samples having varying levels of contamination and phases of ageing. Results show that there is a strong correlation between the contamination level and ageing of the insulators with the amplitude and harmonic components of the UV signals. This correlation can useful to monitor in-service insulator surface conditions.
The walking of a humanoid robot needs to be robust enough in order to maintain balance in a dynamic environment especially on uneven terrain. A walking model based on multi-sensor is proposed for a Robotis DARwIn-OP robot named as Leman. Two force sensitive resistor (FSRs) on both feet equipped to Leman to estimate the zero moment point (ZMP) alongside with accelerometer and gyrosensor embedded in the body for body state estimation. The results show that the FSRs can successfully detect the unbalanced walking event if the protuberance exists on the floor surface and the accelerometer and gyrosensor (Inertial Measurement Unit, IMU) data are recorded to tune the balancing parameter in the model.
Life-cycle assessment (LCA) is one of the most attractive tools employed nowadays by environmental policy-makers as well as business decision-makers to ensure environmentally sustainable production/consumption of various goods/services. LCA is a systematic, rigorous, and standardized approach aimed at quantifying resources consumed/depleted, pollutants released, and the related environmental and health impacts through the course of consumption and production of goods/service. Algal fuels are no exception and their environmental sustainability could be well scrutinized using the LCA methodology. In line with that, this chapter is devoted to present guidelines on the technical aspects of LCA application in algal fuels while elaborating on major standards used, i.e., ISO 14040 and 14044 standards. Overall, LCA practitioners as well as technical experts dealing with algal fuels in both the public and private sectors could be the main target audience for these guidelines.
The combined effort of the neuroscience and psychology cluster at the Universiti Sains Malaysia (USM)-fundamental, applied and clinical-has moved the institution to the number two position in the country, behind Universiti Malaya. The strategy to join the Global Brain Consortium (GBC) and put Malaysia on the map to address the GBC mission, vision, focus areas and outcomes began recently, in May 2019.
This study aims at exploring the impact of corruption control on energy efficiency in 60 countries categorized by income: lower middle (LMI), upper middle (UMI), and high (HI). Panel methodology was utilized taking the period of 2000-2017. As cross-sectional dependence is confirmed among the tested equations, the Pesaran (J Appl Econ 22(2):265-312, 2007) unit root test and the augmented mean group estimator proposed by Eberhardt and Teal (2010) were utilized to overcome this matter. The results in general indicate that the lower the corruption is, the more the energy efficiency for all income group economies. Moreover, renewable energy reduces energy efficiency in lower-middle income and high-income economies while its effect is positive in middle-income economies. In addition, the environmental Kuznets curve (EKC) found to be present in all income group economies. Lastly, causality relationships among energy efficiency, corruption, and GDP were present mostly in upper-middle income and high-income economies. From the results, it was recommended that the countries from all income groups should increase their corruption control for the purpose of enhancing energy efficiency.
This paper investigates the compressibility characteristics of compacted clay treated with cement, peat ash and silica
sand. For this purpose, one dimensional consolidation tests were conducted to determine the soil consolidation properties.
The test specimens were trimmed from the compaction test specimen. The 1D consolidation test specimen was subjected
to the normal pressures of 2.5, 5, 10, 20, 40, 80 and 160 kPa in sequence on the test specimen which was saturated with
distilled water. At the end of the loading period of 80 kPa, the vertical load was removed and the specimen was allowed
to expand for 24 h for the purpose of evaluating of its swelling behavior. The results showed that void ratio of the soil
specimens decreased with increasing effective normal pressure. The laboratory investigation clearly demonstrates that,
settlement is as the compression of a soil specimen due to vertical loading applied at the top surface of the 1D consolidation
test specimen. It was concluded that, the compression settlement of the stabilized soil with the binder composition of
18% cement, 2% peat ash and 5% silica sand improved by almost 1.3-fold. A notable discovery is the suitability of the
stabilized soil for road embankment and low lying marginal area for foundation works; also solving the environmental
problems in relation to peaty ground. However, sufficient laboratory and field testing are required.
The seasonal variation of spider assemblages in botanical garden was investigated. The spiders were manually collected by diurnal and nocturnal session between two seasons. A total of 19 families from 65 genera and 96 species were recorded. Richness-estimator indicates the inventory were 67% complete within the botanical garden. The capture rate for web-weavers were higher compared with non-web weavers. The comparison value showed the species composition and abundance were similar between seasons. Spider abundance was not affected between wet and dry season in tropical countries.
Miocene larger benthic foraminifera have been discovered from a limestone unit of the Kalumpang Formation. The limestone is exposed at the Teck Guan Quarry, Tawau, southeast Sabah. The Kalumpang Formation consists predominantly of interbedded mudstone and sandstone (graywacke), conglomerate, limestone, marl, chert and volcanic rocks. Five limestone samples have been collected and processed for petrographic analysis and identification of larger benthic foraminifera. The limestone is classified as packstone and mudstone. A total of seventeen species of larger benthic foraminifera have been identified. The foraminifera are divided into two assemblages namely Assemblage I and Assemblage II. Assemblage I is characterized by the presence of Lepidocyclina (Nephrolepidina) parva, Operculina sp. and Lepidocyclina (Eulepidina) formosa. This assemblage is an indicative of Aquitanian to Burdigalian in age (Early Miocene). Assembalge II comprises of Lepidocyclina (Nephrolepidina) sumatrensis, Lepidocyclina (Nephrolepidina) angulosa, Lepidocyclina (Nephrolepidina) ferreroi Lepidocyclina sp., Miogypsina sp., Katacycloclypeus annulatus, Katacyloclypeus martini, Cycloclypeus carpenteri, Cycloclypeus indopacificus, Cycloclypeus sp., Flosculinella bontangensis, Operculina complanata, Amphistegina bowdenensis and Amphistegina sp. This assemblage is an indicative of Langhian to Serravallian age (Middle Miocene). The foraminiferal assemblages suggest that the depositional environment was a warm tropical shallow-marine at the fore-reef shelf zone.
Dengue fever is a vector-borne viral disease which is now endemic in more than 100 countries affecting more than 2.5 billion people worldwide. In recent years, dengue fever has become a major threat to public health in Pakistan. In this paper, we derived an explicit formula for reproduction number R0 (the most important epidemiological parameter) and then used real data of dengue fever cases of different hospitals of Lahore (Pakistan) on R0. Conditions for local stability of equilibrium points are discussed. In the end, simulations are carried out for different situations.
Litter decomposition is vital for carbon and nutrient turnover in terrestrial ecosystems, and this process has now
been thoroughly demonstrated to be regulated by various mechanisms. The total environment has been continuously
changing in recent decades, especially in high-latitude regions; these alterations, however, profoundly contribute to the
decomposition process, but a comprehensive recognition has not available. Here we reviewed the empirical observations
and current knowledge regarding how hydrological leaching and freeze-thaw events modulate early decomposition of
plant litter. Leaching contributes a considerable percentage of mass loss and carbon and nutrient release in early stage of
decomposition, but the magnitudes are different between species levels depending on the chemical traits. Frequent freezing
and thawing events could positively influence decomposition rate in cold biomes but also hamper soil decomposer and
there is no general and predictable pattern has been emerged. Further experiments should be manipulated to estimate
how the altered freezing and thawing effect on carbon and nutrient release from plant litter to better understanding the
changing environment on litter decomposition.
The growth of residential and commercial areas threatens vegetation and ecosystems. Thus, an urgent urban management
issue involves determining the state and the quantity of urban tree species to protect the environment, as well as controlling
their growth and decline. This study focused on the detection of urban tree species by considering three types of tree
species, namely, Mesua ferrea L., Samanea saman, and Casuarina sumatrana. New rule sets were developed to detect these
three species. In this regard, two pixel-based classification methods were applied and compared; namely, the method of
maximum likelihood classification and support vector machines. These methods were then compared with object-based
image analysis (OBIA) classification. OBIA was used to develop rule sets by extracting spatial, spectral, textural and color
attributes, among others. Finally, the new rule sets were implemented into WorldView-2 imagery. The results indicated
that the OBIA based on the rule sets displayed a significant potential to detect different tree species with high accuracy.
A distinct element approach has been introduced for simulating the plugging performance of granular lost circulation materials (LCM) in a fracture. This approach solves the fully coupled fracture walls, fluid and particles system in an interactive environment. The effects of the particle shape, size distribution and concentration on the fracture-plugging performance of the granular LCM have been investigated using the three-dimensional particle flow code (PFC3D). The simulated results showed that the irregular granular LCM could plug a fracture width larger than the sieving granulation by single-particle bridging type. The particle size distribution (PSD) of LCM dominates the plugging depth and efficiency in a fracture and there exists an optimum concentration for maximum effect of LCM additives.
In most research including environmental research, missing recorded data often exists and has become a common problem for data quality. In this study, several imputation methods that have been designed based on the techniques for functional data analysis are introduced and the capability of the methods for estimating missing values is investigated. Single imputation methods and iterative imputation methods are conducted by means of curve estimation using regression and roughness penalty smoothing approaches. The performance of the methods is compared using a reference data set, the real PM10 data from an air quality monitoring station namely the Petaling Jaya station located at the western part of Peninsular Malaysia. A hundred of the missing data sets that have been generated from a reference data set with six different patterns of missing values are used to investigate the performance of the considered methods. The patterns are simulated according to three percentages (5, 10 and 15) of missing values with respect to two different sizes (3 and 7) of maximum gap lengths (consecutive missing points). By means of the mean absolute error, the index of agreement and the coefficient of determination as the performance indicators, the results have showed that the iterative imputation method using the roughness penalty approach is more flexible and superior to other methods.
Prevention and mitigation of rainfall induced geological hazards after the Ms=8 Wenchuan earthquake on May 12th, 2008 were significant for rebuild of earthquake hit regions. After the Wenchuan earthquake, there were tens of thousands of fractured slopes which were broken and loosened by the ground shaking, they were very susceptible to heavy rainfall and change forms into potential debris flows. In order to carry out this disaster reduction and prediction effectively in Longmenshan region, careful real-time monitoring and pre-warning of mountain hazards in both regional and site-specific scales is reasonable as alternatives in Wenchuan earthquake regions. For pre-warning the failure of fractured slopes induced by rainfall, the threshold value or the critical value of the precipitation of hazards should be proposed. However, the identification of critical criterion and parameters to pre-warning is the most difficult issue in mountainous hazards monitoring and pre-warning system especially in the elusive and massive fractured slopes widespread in Wenchuan earthquake regions. In this study, a natural coseismic fractured landslide in the Taziping village, Hongkou County, Dujianyan City, was selected to conduct the field experimental test, in order to identify the threshold parameters and critical criterion of the fractured slopes of Taziping. After the field experimental test, the correlation of rainfall intensity, rainfall duration and accumulative rainfall was investigated. The field experimental test was capable of identifying the threshold factors for failure of rainfall-induced fractured slopes after the giant earthquake.