19672 research outputs found
Sort by
Operating a reservoir system based on the shark machine learning algorithm
No full textThe operating process of a multi-purpose reservoir needs to develop models that have the ability to overcome the challenges facing the decision makers. Therefore, the development of a mathematical optimization model is crucial for selecting the optimal policies for the reservoir operation. In the current study, the shark machine learning algorithm (SMLA) is proposed to develop an optimal rule for operating the reservoir. The SMLA began with a group of randomly produced potential solutions and later interactively executed the search for the optimal solution. The procedure for the SMLA is suitable to be applied to a reservoir system due to its ability to tackle the stochastic features of dam and reservoir systems. The major purpose of the proposed models is to generate an operation rule that could minimize the absolute value of the differences between water release and water demand. The proposed model has been examined using the data of the Aswan High Dam, Egypt as the case study. The performance of the SMLA was compared with the performance of the most widespread evolutionary algorithms, namely, the genetic algorithm (GA). Comprehensive analysis of the results was performed using three performance indicators, namely, resilience, reliability, and vulnerability. This work concluded that the performance of the SMLA model was better than the GA model in generating the optimal policy for reservoir operation. The result showed that the SMLA succeeded in providing high reliability (99.72%), significant resilience (1) and minimum vulnerability (20.7% of demand)
The effects of spatial dynamics on a wormhole throat
No full textPrevious studies on dynamic wormholes were focused on the dynamics of the wormhole itself, be it either rotating or evolutionary in character and also in various frameworks from classical to braneworld cosmological models. In this work, we modeled a dynamic factor that represents the spatial dynamics in terms of spacetime expansion and contraction surrounding the wormhole itself. Using an RS2-based braneworld cosmological model, we modified the spacetime metric of Wong and subsequently employed the method of Bronnikov, where it is observed that a traversable wormhole is easier to exist in an expanding brane universe, however it is difficult to exist in a contracting brane universe due to stress-energy tensors requirement. This model of spatial dynamic factor affecting the wormhole throat can also be applied on the cyclic or the bounce universe model
Evaluation of Methadone Treatment in Malaysia: Findings from the Malaysian Methadone Treatment Outcome Study (MyTOS)
No full textBackground: Opioid misuse and dependence is a global issue with a huge negative impact. In Malaysia, heroin is still the main illicit drug used, and methadone maintenance treatment (MMT) has been used since 2005. Objective: To evaluate the effectiveness of MMT. Methods: This was a cross-sectional study conducted in 103 treatment centers between October and December 2014 using a set of standard questionnaires. Data were analyzed using SPSS Statistics 20. Results: There were 3254 respondents (93.6% response rate); of these 17.5% (n = 570) transferred to another treatment center, 8.6% (n = 280) died, 29.2% (n = 950) defaulted, and 7.6% (n = 247) were terminated for various reasons. Hence, 1233 (37%) respondents' baseline and follow-up data were further analyzed. Respondents had a mean age of 39.2 years old and were mainly male, Malay, Muslim, married (51.1%, n = 617), and currently employed. Few showed viral seroconversion after they started MMT (HIV: 0.5%, n = 6; Hepatitis B: 0.3%, n = 4; Hepatitis C: 2.7%, n = 29). There were significant reductions in opioid use, HIV risk-taking score (p < 0.01), social functioning (p < 0.01), crime (p < 0.01), and health (p < 0.01). However, there were significant improvements in quality of life in the physical, psychological, social, and environmental domains. Factors associated with change were being married, employed, consuming alcohol, and high criminality at baseline. Lower methadone dosage was significantly associated with improvements in the physical, psychological, and environmental domains. Conclusion/Importance: The MMT program was found to be successful; hence, it should be expanded
Influence of Annealing Temperature on Photocatalytic and Electrochemical Sensing Properties of SnO2/ZnO Nanocomposites
No full textSnO2/ZnO nanocomposites were prepared by sol-gel technique in the presence of polyethylene glycol, followed by annealing at various temperatures ranging from 600 to 1000 °C. The prepared SnO2/ZnO were studied by XRD, FTIR, FT-Raman,TEM, UV-vis DR spectroscopy, photoluminescence spectroscopy, and nitrogen adsorption-desorption isotherm analysis. The crystal phases and energy gap of the SnO2/ZnO nanocomposites were modified with annealing temperatures. The photocatalytic activity of the prepared SnO2/ZnO nanocomposites for the decomposition of methylene blue (MB) dye was examined under visible light illumination. It was found that photodegradation rate of the prepared photocatalysts for the decomposition of MB decreased linearly upon increasing the annealing temperature from 600 to 1000 °C. The maximum photocatalytic efficiency (100%) was obtained for the SnO2/ZnO nanocomposite annealed at 600 oC. The photocatalytic activity of the SnO2/ZnO nanocomposite was dependent on their surface areas and bandgap values. The optimal SnO2/ZnO nanocomposite annealed at 600 oC was also used for the electrochemical sensing of liquid ethanol showing significant sensing response with a high sensitivity of 20.09 μAm M-1 cm-2 and a limit of detection of 25.2 μM ethanol concentration
Histological changes of immediate skin expansion of the distal limb of rats
No full textAim: Tissue expansion is an applicable technique to reconstruct many surgical defects. The aim of this research was to evaluate the histological changes caused by immediate skin tissue expansion in rats as an animal model. Materials and Methods: Immediate skin tissue expansion in 18 adult female rats was performed using three different sizes (small, medium, and big) of polymethylmethacrylate tissue expanders at the dorsal surface of the metatarsal area of the right limb. The contralateral limb was served as the control. The tissue expanders were surgically implanted and kept for 15 days. Results: The immediate skin expansion resulted in histological changes such as the increased thickness of the epidermal layer, the reduction of the dermal layer, an elevated number of fibroblast as well as increased vascularity. Furthermore, skin adnexal structures such as hair follicles and sebaceous glands were farther apart. Conclusion: The rat skin was able to rapidly adjust and compensate against a specific range of immediate mechanical expansion. The histological changes suggest that the tissues were prepared to withstand the increased external forces, in addition to create possibly additional skin in a relatively short-term period
Cross-sectional analysis of ethnic differences in fall prevalence in urban dwellers aged 55 years and over in the Malaysian Elders Longitudinal Research study
No full textObjectives Falls represent major health issues within the older population. In low/middle-income Asian countries, falls in older adults remain an area which has yet to be studied in detail. Using data from the Malaysian Elders Longitudinal Research (MELoR), we have estimated the prevalence of falls among older persons in an urban population, and performed ethnic comparisons in the prevalence of falls. Design Cross-sectional analysis was carried out using the first wave data from MELoR which is a longitudinal study. Setting Urban community dwellers in a middle-income South East Asian country. Participants 1565 participants aged ≥55 years were selected by simple random sampling from the electoral rolls of three parliamentary constituencies. Outcome measures Consenting participants from the MELoR study were asked the question € Have you fallen down in the past 12 months?' during their computer-assisted home-based interviews. Logistic regression analyses were conducted to compare the prevalence of falls among various ethnic groups. Results The overall estimated prevalence of falls for individuals aged 55 years and over adjusted to the population of Kuala Lumpur was 18.9%. The estimated prevalence of falls for the three ethnic populations of Malays, Chinese and Indian aged 55 years and over was 16.2%, 19.4% and 23.8%, respectively. Following adjustment for ethnic discrepancies in age, gender, marital status and education attainment, the Indian ethnicity remained an independent predictor of falls in our population (relative risk=1.45, 95% CI 1.08 to 1.85). Conclusion The prevalence of falls in this study is comparable to other previous Asian studies, but appears lower than Western studies. The predisposition of the Indian ethnic group to falls has not been previously reported. Further studies may be needed to elucidate the causes for the ethnic differences in fall prevalence
Real-Time Human Detection for Aerial Captured Video Sequences via Deep Models
No full textHuman detection in videos plays an important role in various real life applications. Most of traditional approaches depend on utilizing handcrafted features which are problem-dependent and optimal for specific tasks. Moreover, they are highly susceptible to dynamical events such as illumination changes, camera jitter, and variations in object sizes. On the other hand, the proposed feature learning approaches are cheaper and easier because highly abstract and discriminative features can be produced automatically without the need of expert knowledge. In this paper, we utilize automatic feature learning methods which combine optical flow and three different deep models (i.e., supervised convolutional neural network (S-CNN), pretrained CNN feature extractor, and hierarchical extreme learning machine) for human detection in videos captured using a nonstatic camera on an aerial platform with varying altitudes. The models are trained and tested on the publicly available and highly challenging UCF-ARG aerial dataset. The comparison between these models in terms of training, testing accuracy, and learning speed is analyzed. The performance evaluation considers five human actions (digging, waving, throwing, walking, and running). Experimental results demonstrated that the proposed methods are successful for human detection task. Pretrained CNN produces an average accuracy of 98.09%. S-CNN produces an average accuracy of 95.6% with soft-max and 91.7% with Support Vector Machines (SVM). H-ELM has an average accuracy of 95.9%. Using a normal Central Processing Unit (CPU), H-ELM's training time takes 445 seconds. Learning in S-CNN takes 770 seconds with a high performance Graphical Processing Unit (GPU)
Fracture resistance of three different all-ceramic crowns: In vitro study
No full textPurpose: To evaluate the fracture resistance and failure mode of three different all-ceramic crowns; CEREC Bloc, IPS e.Max Press and Cercon in a simulated clinical situation. Methods: 30 extracted maxillary premolars were prepared and randomly assigned to three groups equally according to the type of crown used. The first was the CEREC group: monolithic feldspathic crowns (CEREC Blocs). The second was the E.Max group: monolithic lithium disilicate crowns (IPS e.Max Press). The third group was the Cercon group: bilayered partially stabilized zirconia crowns (Cercon). All crowns were cemented using dual-cured resin cement (ParaCore). The specimens were then subjected to thermocycling (5-55°C/500 cycles) and loaded to failure at an angle of 45° to the occlusal surface of the crown. Failure data was statistically analyzed using one-way ANOVA and Tukey's HSD post hoc test at a= 0.05. Fractographic analysis was performed to determine the fracture modes of the failed specimens. Results: The mean fracture values for CEREC, E.Max and Cercon groups were 387 ± 60 N, 452 ± 86 N, and 540 ± 171 N, respectively. Significant differences were found between CEREC and Cercon groups (P< 0.05). Catastrophic fracture within the ceramic crown was the major failure mode of the CEREC group. For E.Max and Cercon groups, the major failure mode was exhibiting severe tooth fracture while the ceramic crown remained intact
Characterization of electron beams emitted from dense plasma focus machines using argon, neon and nitrogen
No full textThe measured current traces of two low energy machines namely the AECS PF-2 and INTI PF are used for studying of the produced electron beam features using the modified Lee code (RADPFV5.15REB) at different conditions. The fitting procedures between measured and computed current traces are made for each point of pressure. In the case of AECS PF-2 working with neon, the electron fluence reaches the maximum value 2.35 × 1022 electrons m-2 for 1.6 Torr and the flux achieves 2.42 × 1030 electrons m-2s-1 near 1.5 Torr. The electron number has a peak of 5.74 × 1014 at 0.9 Torr. The computed results demonstarte also the maximum value of the power flow density of 2.44 × 1016 Wm-2, and the superior damage factor of around 1.95 × 1012 Wm-2s0.5 at a pressure of 0.4 Torr. Argon presents the action of radiative cooling topping at highly magnified 6.13 × 1031 m-2s-1 at 0.9 Torr. The damage factor reaches almost 175 × 1012 Wm-2s0.5 for Ar but it is only 1.29 × 1012 Wm-2s0.5 for N2. The huge values for argon are a result of enhanced compression due to radiative cooling. In the case of INTI PF device, the electron energy extends from 58 keV (for N2) to 256 keV (for Ar). The results indicate that the electron fluence ranges from 2 × 1022 electrons m-2 for N2 to 88 × 1022 electrons m-2 for Ar
Conductivity, dielectric studies and structural properties of P(VA-co-PE) and its application in dye sensitized solar cell
No full textPoly(vinyl alcohol-co-ethylene), P(VA-co-PE) gel polymer electrolytes (GPEs) with sodium iodide (NaI) as a dopant salt was synthesized and investigated. Electrolytes containing different concentrations of NaI salt were studied using AC impedance spectroscopy, FTIR spectroscopy, and XRD spectroscopy. The results from dielectric studies reveal both the real part and imaginary part of complex permittivity decrease with increasing frequency. An opposite trend was observed when the temperatures of the samples were increased. Besides, the dispersion relation from the modulus studies confirmed that ionic conductivity is dominant in the GPE samples. Results from temperature studies reveal that all GPE samples conform the Arrhenius equation in the temperature range of 303 K to 373 K. The sample with 40% of NaI exhibits the highest ionic conductivity of 2.266 mS cm−1 with the activation energy of 0.16808 eV. Furthermore, FTIR studies proved the complexation between P(VA-co-PE) and NaI. The crystallinity of the samples was shown to be increasing with the increasing concentration of NaI salt via XRD results. Finally, DSSCs were assembled using the polymer electrolyte and used for photovoltaic studies. The best performance of DSSC was obtained with the energy conversion efficiency of 3.32% using the GPE sample with 40% NaI