Search results for: pre-warping frequency

Authors: Sanjida Akter, Ambali Alade Odebowale, Andrey E. Miroshnichenko, Haroldo T. Hattori

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Photodetectors (PDs) play a pivotal role in optoelectronics and optical devices, serving as fundamental components that convert light signals into electrical signals. As the field progresses, the integration of advanced materials with unique optical properties has become a focal point, paving the way for the innovation of novel PDs. This study delves into the exploration of a cutting-edge photodetector designed for deep and near ultraviolet (UV) applications. The photodetector is constructed with a composite of Zirconium Boride (ZrB2) and Chromium (Cr) alloy, deposited onto a 6H nitrogen-doped silicon carbide substrate. The determination of the optimal alloy thickness is achieved through Finite-Difference Time-Domain (FDTD) simulation, and the synthesis of the alloy is accomplished using radio frequency (RF) sputtering. Remarkably, the resulting photodetector exhibits an exceptional responsivity of 3.5 A/W under an applied voltage of -2 V, at wavelengths of 405 nm and 280 nm. This heterostructure not only exemplifies high performance but also provides a versatile platform for the development of near UV photodetectors capable of operating effectively in challenging conditions, such as environments characterized by high power and elevated temperatures. This study contributes to the expanding landscape of photodetector technology, offering a promising avenue for the advancement of optoelectronic devices in demanding applications.

Keywords: responsivity, silicon carbide, ultraviolet photodetector, zirconium boride

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Authors: A. E. Obayelu, S. O. Olubiyo

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Food is different from other commodities because everybody needs food for survival. This has led to a shift in focus to food security in the global policy arena. However, there is paucity of studies on the interactions between food security, migration, urbanization and population rise. This paper therefore look at the linkages between migration and food security in the context of rapid urbanization and population rise of Nigeria. The study obtained data and information from both secondary sources and primary method through the voice of some selected Nigerians through telephone interview. The findings revealed that, the primary factor for the rapid urbanization in Nigeria is migration; most foods are still produced by peasant farmers who are scattered all over the rural areas and not multinational companies who produce on large scale. The country is still characterized with inadequate infrastructural facilities and services to cater for growing population. There are no protective policies enforced by the Nigeria government. In most cases, the migrants are left entirely on mercy of what they can find to due for survival. The most common coping mechanisms by migrants from rural to urban areas are changing food intake in terms of quantity, quality, diversity and frequency and prioritizing children. Policies that address urban food security need to consider the complex relationship between rapid population rise and migration and appropriate transformations that will be able to manage urbanization. With increasing rate of urbanization, the focus of food security should no longer be that of rural only

Keywords: agricultural commercialization, agricultural transformation, food security, urban, urbanization

Procedia PDF Downloads 407

Authors: O. J. Sharaibi, O. T. Ogundipe, O. A. Magbagbeola, M. I. Kazeem, A. J. Afolayan, M. T. Yakubu

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Hyperprolactinemia is a condition of elevated levels of serum prolactin in humans. It is one of the major causes of female infertility because, excess prolactin inhibits gonadotropin secretion. When gonadotropin is low, follicle stimulating hormone (FSH) and luteinizing hormone (LH) secretions are low and so, do not stimulate gamete production and gonadal steroid synthesis. The aim of this study is to identify and investigate indigenous medicinal plants that can be used in the treatment of hyperprolactinemia. Based on the frequency of mentioning during the ethnobotanical survey, Nymphaea lotus L. was selected for studies. The prolactin-lowering potential of aqueous extract of N. lotus and its effects on other female reproductive hormones in comparison with bromocritptine was evaluated by inducing hyperprolactinemia with metoclopramide at a dose of 5 mg/kg body weight of the animals for 21 days and then administered various doses of aqueous extract of N. lotus for another 21 days. Aqueous extract of N. lotus at 50, 100 and 200 mg/kg body weight significantly reduced the serum prolactin levels in female Wistar rats by 40.06, 52.60 and 61.92 % respectively. The extract at 200 mg/kg body weight had higher prolactin-lowering effect (61.92%) than bromocriptine (53.53%). Aqueous extract of N. lotus significantly increased (p < 0.05) the serum concentrations of FSH, LH and progesterone while estradiol concentrations were reduced. This study shows that Nymphaea lotus is a medicinal plant that can be used in the treatment of hyperprolactinemia.

Keywords: hyperprolactinemia, infertility, metoclopramide, Nymphaea lotus

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Authors: Funmilayo Abiola Opadoja, Samuel Olukayode Awotona

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Nursing services costing has been a major interest to nurses for a long period of time. Determination of nursing costing is germane in order to show the effectiveness of nursing practice in an improved and affordable health care delivery system. This has been a major concern of managers that have the mind of quality and affordable health services. The treatment or intervention should be considered as ‘product’ of nursing care and should provide an explainable term for billing. The study was non-experimental, descriptive and went about eliciting the views of nurses on costing nursing care at two public hospitals namely: University College Hospital and Adeoyo Maternity Teaching Hospital. The questionnaire was the instrument used in eliciting nurse’s response. It was administered randomly on 300 selected respondents across various wards within the hospitals. The data was collected and analysed using SPSS20.0 to generate frequency, and cross-tabulations to explore the statistical relationship between variables. The result shows that 89.2% of the respondents viewed costing of nursing care as an important issued to be looked into. The study concluded that nursing care costing is germane to enhancing the status and imagery of the nurses, it is essential because it would enhance the performance of nurses in discharging their duties. There is need to have a procedural manual agreed on by nursing practitioner on costing of each care given.

Keywords: costing, health care delivery system, intervention, nursing care, practitioner

Procedia PDF Downloads 294

Authors: Wlodzimierz Ogryczak, Tomasz Sliwinski, Jaroslaw Hurkala, Mariusz Kaleta, Bartosz Kozlowski, Piotr Palka

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Implementation concepts of a decision support system for planning and management of mobile personnel tasks (sales representatives and others) are discussed. Large-scale periodic time-dependent vehicle routing and scheduling problems with complex constraints are solved for this purpose. Complex nonuniform constraints with respect to frequency, time windows, working time, etc. are taken into account with additional fast adaptive procedures for operational rescheduling of plans in the presence of various disturbances. Five individual solution quality indicators with respect to a single personnel person are considered. This paper deals with modeling issues corresponding to the problem and general solution concepts. The research was supported by the European Union through the European Regional Development Fund under the Operational Programme ‘Innovative Economy’ for the years 2007-2013; Priority 1 Research and development of modern technologies under the project POIG.01.03.01-14-076/12: 'Decision Support System for Large-Scale Periodic Vehicle Routing and Scheduling Problems with Complex Constraints.'

Keywords: mobile personnel management, multiple criteria, time dependent, time windows, vehicle routing and scheduling

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Authors: Almas Rajguru, Archana Kamath, Rachana Singh

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The study aims to determine the depositional facies, high-resolution sequence stratigraphy, and diagenetic processes of Early Oligocene carbonates in N & N-W of Heera, Mumbai Offshore. Foraminiferal assemblage and microfacies from cores of Well A, B, C, D and E are indicative of facies association related to four depositional environments, i.e., restricted inner lagoons-tidal flats, shallow open lagoons, high energy carbonate bars-shoal complex and deeper mid-ramps of a westerly dipping homoclinal carbonate ramp. Two high-frequency (4th Order) depositional sequences bounded by sequence boundary, DS1 and DS2, displaying hierarchical stacking patterns, are identified and correlated across wells. Vadose zone diagenesis effect during short diastem/ subaerial exposure has rendered good porosity due to dissolution in HST carbonates and occasionally affected underlying TST sediments (Well D, C and E). On mapping and correlating the sequences, the presence of thin carbonate bars that can be potential reservoirs are envisaged along NW-SE direction, towards north and south of Wells E, D and C. A more pronounced development of these bars in the same orientation can be anticipated towards the west of the study area.

Keywords: sequence stratigraphy, depositional facies, diagenesis petrography, early Oligocene, Mumbai offshore

Procedia PDF Downloads 55

Authors: Uzma Ayaz, Sanam Bashir, Shahid Iqbal Awan, Muhammad Ilyas, Muhammad Fareed Khan

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Drought stress directly affects growth along with the productivity of plants by altering plant water status. Sunflower (Helianthus annuus L.), an oilseed crop, is adversely affected by abiotic stresses. The present study was carried out to characterize the genetic variability for seedling and morpho-physiological parameters in different sunflower genotypes under water-stressed conditions. A total of twenty-seven genotypes, including two hybrids, eight advanced lines and seventeen accessions of sunflower (Helianthus annuus L.) were tested against drought stress at Seedling stages by Polyethylene glycol (PEG). Significant means were calculated among traits using analysis of variance (ANOVA) whereas, correlation and principal component analysis also confirmed that germination percentage, root length, shoot length, chlorophyll content, stomatal frequency are positively linked with each other hence, these traits were responsible for most of the variation among genotypes. The cluster analysis results showed that genotypes Ausun, line-3, line-2, and 17578, line-1, line-7, line-6 and 17562 as more diverse among all the genotypes. These most divergent genotypes could be utilized in the development of drought-tolerant inbreed lines which could be subsequently used in future heterosis breeding programs.

Keywords: sunflower, drought, stress, polyethylene- glycol, screening

Procedia PDF Downloads 100

Authors: M. D. Levi, Netanel Shpigel, Sergey Sigalov, Gregory Salitra, Leonid Daikhin, Doron Aurbach

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We have developed an in-situ method for tracking ions adsorption into composite nanoporous carbon electrodes based on quartz-crystal microbalance (QCM). In these first papers QCM was used as a simple gravimetric probe of compositional changes in carbon porous composite electrodes during their charging since variation of the electrode potential did not change significantly width of the resonance. In contrast, when we passed from nanoporous carbons to a composite Li-ion battery material such as LiFePO4 olivine, the change in the resonance width was comparable with change of the resonance frequency (polymeric binder PVdF was shown to be completely rigid when used in aqueous solutions). We have provided a quantitative hydrodynamic admittance model of ion-insertion processes into electrode host accompanied by intercalation-induced dimensional changes of electrode particles, and hence the entire electrode coating. The change in electrode deformation and the related porosity modify hydrodynamic solid-liquid interactions tracked by QCM with dissipation monitoring. Using admittance modeling, we are able to evaluate the changes of effective thickness and permeability/porosity of composite electrode caused by applied potential and as a function of cycle number. This unique non-destructive technique may have great advantage in early diagnostics of cycling life durability of batteries and supercapacitors.

Keywords: Li-ion batteries, particles deformations, QCM-D, viscoelasticity

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Authors: R. S. Yadav, J. Havlica, I. Kuřitka, Z. Kozakova, J. Masilko, L. Kalina, M. Hajdúchová, V. Enev, J. Wasserbauer

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Nickel spinel ferrite NiFe2O4 nanoparticles with different particle size at different annealing temperature were synthesized using the starch-assisted sol-gel auto-combustion method. The synthesized nanoparticles were characterized by conventional powder X-ray diffraction (XRD) spectroscopy, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, Field-Emission Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy and Vibrating Sample Magnetometer. The XRD patterns confirmed the formation of NiFe2O4 spinel ferrite nanoparticles. Field-Emission Scanning Electron Microscopy revealed that particles are of spherical morphology with particle size 5-20 nm at lower annealing temperature. An infrared spectroscopy study showed the presence of two principal absorption bands in the frequency range around 525 cm-1 (ν1) and around 340 cm-1 (ν2); which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. Raman spectroscopy study also indicated the change in octahedral and tetrahedral site related Raman modes in nickel ferrite nanoparticles with change of particle size. This change in magnetic behavior with change of particle size of NiFe2O4 nanoparticles was observed.

Keywords: nickel ferrite, nanoparticles, magnetic property, NiFe2O4

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Authors: Evgeniia V. Mekhonoshina, Vladimir Ya. Modorskii, Vasilii Yu. Petrov

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At present, vibrations of rotors of gas transmittal unit evade sustainable forecasting. This paper describes elastic oscillation modes in resilient supports and rotor impellers modeled during computational experiments with regard to interference in the system of gas-dynamic flow and compressor rotor. Verification of aeroelastic approach was done on model problem of interaction between supersonic jet in shock tube with deformed plate. ANSYS 15.0 engineering analysis system was used as a modeling tool of numerical simulation in this paper. Finite volume method for gas dynamics and finite elements method for assessment of the strain stress state (SSS) components were used as research methods. Rotation speed and material’s elasticity modulus varied during calculations, and SSS components and gas-dynamic parameters in the dynamic system of gas-dynamic flow and compressor rotor were evaluated. The analysis of time dependence demonstrated that gas-dynamic parameters near the rotor blades oscillate at 200 Hz, and SSS parameters at the upper blade edge oscillate four times higher, i.e. with blade frequency. It has been detected that vibration amplitudes correction in the test points at magnetic bearings by aeroelasticity may correspond up to 50%, and about -π/4 for phases.

Keywords: Centrifugal compressor, aeroelasticity, interdisciplinary calculation, oscillation phase displacement, vibration, nonstationarity

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Authors: Rahul S. Raj

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Electro-mechanical impedance technique is a recently developed non-destructive method for structural health monitoring. This system comprises of piezo electric patch, bonded to the structure using an adhesive/epoxy and electrically excited to determine the health of the component. The subjected electric field actuates the PZT patch harmonically and imparts a force on the host structure. The structural response thus produced by the host component is in the form of peaks and valleys which further shows the admittance signatures of the structure for the given excitation frequency. Adhesives have the capability to change the structural signatures, in EMI technique, by transforming conductance and susceptance signatures. The static approximation provide a justifiable result where adhesive bond lines are thin and stiff. The epoxy adhesive bonds limits design flexibility due to poor bond strengths, hence to enhance the performance of the joints, a new technique is developed for joining PZT, i.e. the alloy bonding technique. It is a metallic joining compound which contains many active elements including Titanium, that reacts with the tenacious surface films of the ceramic and composites to create excellent bonds. This alloy-based bonding technique will be used for better strain interaction and rigorous stress transfer between PZT patch and the host structure.

Keywords: EMI technique, conductance, susceptance, admittance, alloy bonding

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Authors: Taleb L., Benarbia M., Brahmi M., Belmiloud H., Boukerche A.

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Introduction and purpose of the study: Cavum cancer in children and adolescents is rare and represents 8% of all nasopharyngeal cancers treated in our department. Our objective is to study its epidemiological, clinical, therapeutic, and evolutionary particularities. Material and methods: Retrospective study of 39 patients under 20 years old, treated for undifferentiated non-metastatic carcinoma of the nasopharynx at the Emir Abdelkader Cancer Center between 2014 and 2020. Results and statistical analysis: Median age was 14 years [7-19 years], with a sex ratio of 2.9. The median time to diagnosis was 5.6 months [1 to 14 months], the circumstances of the discovery of which were dominated by lymph node syndrome in 43.6% of cases (n=17) followed by a rhinological syndrome in 30.8% of cases (n=13). The tumor stage was T1 for two patients (5.1%), T2 for 8 (20.5%), T3 for 9 (23.1%), T4 for 20 (51.3%), N0 for 2 (5 .1%) N1 for 4 (10.3%), N2 for 28 (71.8%) and N3 for 5 (12.8%). All patients received induction chemotherapy followed by concomitant radiotherapy with cisplatin. The dose of irradiation delivered to the cavum and adenopathies was 66 Gy with fractionation of 2 Gy per session in 69.2% of cases (n=27) and 1.8 Gy in 30.8% of cases (n=12). With a median follow-up of 51 months (15 to 97 months), the locoregional, metastatic, specific, and overall relapse-free survival rates at five years were 91.1%, 73.5%, 66.1%, and 68.4, respectively. Conclusion: Chemotherapy and radiotherapy treatment of cavum cancer in children and adolescents has allowed excellent locoregional control despite the advanced stage of the disease. However, the frequency of metastatic relapses could justify the possible use of systemic maintenance treatment.

Keywords: cancer, nasopharynx, radiotherapy, chemotherapy, survival

Procedia PDF Downloads 90

Authors: Ilaria Lucrezia Amerise

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The statistical modelling of precipitation data for a given portion of territory is fundamental for the monitoring of climatic conditions and for Hydrogeological Management Plans (HMP). This modelling is rendered particularly complex by the changes taking place in the frequency and intensity of precipitation, presumably to be attributed to the global climate change. This paper applies the Wakeby distribution (with 5 parameters) as a theoretical reference model. The number and the quality of the parameters indicate that this distribution may be the appropriate choice for the interpolations of the hydrological variables and, moreover, the Wakeby is particularly suitable for describing phenomena producing heavy tails. The proposed estimation methods for determining the value of the Wakeby parameters are the same as those used for density functions with heavy tails. The commonly used procedure is the classic method of moments weighed with probabilities (probability weighted moments, PWM) although this has often shown difficulty of convergence, or rather, convergence to a configuration of inappropriate parameters. In this paper, we analyze the problem of the likelihood estimation of a random variable expressed through its quantile function. The method of maximum likelihood, in this case, is more demanding than in the situations of more usual estimation. The reasons for this lie, in the sampling and asymptotic properties of the estimators of maximum likelihood which improve the estimates obtained with indications of their variability and, therefore, their accuracy and reliability. These features are highly appreciated in contexts where poor decisions, attributable to an inefficient or incomplete information base, can cause serious damages.

Keywords: generalized extreme values, likelihood estimation, precipitation data, Wakeby distribution

Procedia PDF Downloads 123

Authors: Alia Ali, Azeem Taj, Muhammed Joher Amin, Farrukh Iqbal, Zafar Iqbal

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Background: Hypertension is commonly found in patients with Diabetic Kidney Disease (DKD). Microalbuminuria is the first clinical sign of involvement of kidneys in patients with type 2 diabetes. Uncontrolled hypertension induces a higher risk of cardiovascular events, including death, increasing proteinuria and progression to kidney disease. Objectives: To determine the correlation between microalbuminuria and hypertension and their association with other risk factors in type 2 diabetic patients. Methods: One hundred and thirteen type 2 diabetic patients were screened for microalbuminuria and raised blood pressure, attending the diabetic clinic of Shaikh Zayed Hospital, Lahore, Pakistan. The study was conducted from November 2012 to June 2013. Results: Patients were divided into two groups. Group 1, those with normoalbuminuria (n=63) and Group 2, those having microalbuminuria (n=50). Group 2 patients showed higher blood pressure values as compared to Group 1. The results were statistically significant and showed poor glycemic control as a contributing risk factor. Conclusion: The study concluded that there is high frequency of hypertension among type 2 diabetics but still much higher among those having microalbuminuria. So, early recognition of renal dysfunction through detection of microalbuminuria and to start treatment without any delay will confer future protection from end-stage renal disease as well as hypertension and its complications in type 2 diabetic patients.

Keywords: hypertension, microalbuminuria, diabetic kidney disease, type 2 Diabetes mellitus

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Authors: Isaac Yeboah

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Physical activity (PA) is considered the best preventative tool for maintaining physical health and extending lifespan because it offers a range of benefits. However, for people to benefit from physical activity, it must be done at a level that can enhance fitness, health, and overall well-being. Therefore, this study aimed to determine the link between physical activity participation levels and cardiorespiratory fitness (CRF). The study employed the descriptive correlational design. The census sampling technique included all 190 teaching staff from the two senior high schools in the Dormaa East District. An adapted International Physical Activity Questionnaire (IPAQ) and standardized physical fitness tests were used for data collection. Descriptive statistics of frequency counts and percentages were used to answer the research questions, while inferential statistics of Pearson Product Moment Correlation and the independent sample t-test were used to test hypotheses one and two, respectively. A moderately negative (r = -.156) relationship existed between physical activity participation levels and CRF. Female teachers demonstrated a statistically significant value (p = .045) than males. The study concluded that the reported physical activity levels of the teachers did not reflect their CRF. The implication is that either the participants overestimated their physical activity participation levels or the intensity of the activities was not high enough to affect physiological changes. For the teachers' CRF to improve, it was suggested, among other things, that regular physical activity sessions of the appropriate mixes of FITT be organized.

Keywords: physical activity, participation levels, cardiorespiratory fitness, sedentary lifestyle, teachers

Procedia PDF Downloads 42

Authors: X. Gu, K. L. Blackmore

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The impact factor was introduced to measure the quality of journals. Various impact measures exist from multiple bibliographic databases. In this research, we aim to provide a broader understanding of the relationship between scholarly impact and other characteristics of academic journals. Data used for this research were collected from Ulrich’s Periodicals Directory (Ulrichs), Cabell’s (Cabells), and SCImago Journal & Country Rank (SJR) from 1999 to 2015. A master journal dataset was consolidated via Journal Title and ISSN. We adopted a two-step analysis process to study the quantitative relationships between scholarly impact and other journal characteristics. Firstly, we conducted a correlation analysis over the data attributes, with results indicating that there are no correlations between any of the identified journal characteristics. Secondly, we examined the quantitative relationship between scholarly impact and other characteristics using quartile analysis. The results show interesting patterns, including some expected and others less anticipated. Results show that higher quartile journals publish more in both frequency and quantity, and charge more for subscription cost. Top quartile journals also have the lowest acceptance rates. Non-English journals are more likely to be categorized in lower quartiles, which are more likely to stop publishing than higher quartiles. Future work is suggested, which includes analysis of the relationship between scholars and their publications, based on the quartile ranking of journals in which they publish.

Keywords: academic journal, acceptance rate, impact factor, journal characteristics

Procedia PDF Downloads 286

Authors: Guanlin Wu, Jiajia Yao, Fang Liu, Junshuai Xue, Jincheng Zhang, Yue Hao

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Owing to the excellent thermal conductivity and ultra-wide bandgap, Aluminum nitride (AlN)/Gallium nitride (GaN) is a highly promising material to achieve high breakdown voltage and output power devices among III-nitrides. In this study, we explore the growth and characterization of polarization-induced AlN/GaN heterostructures using plasma-assisted molecular beam epitaxy (PA-MBE) on AlN-on-sapphire templates. To improve the crystal quality and demonstrate the effectiveness of the PA-MBE approach, a thick AlN buffer of 180 nm was first grown on the AlN-on sapphire template. This buffer acts as a back-barrier to enhance the breakdown characteristic and isolate leakage paths that exist in the interface between the AlN epilayer and the AlN template. A root-mean-square roughness of 0.2 nm over a scanned area of 2×2 µm2 was measured by atomic force microscopy (AFM), and the full-width at half-maximum of (002) and (102) planes on the X-ray rocking curve was 101 and 206 arcsec, respectively, using by high-resolution X-ray diffraction (HR-XRD). The electron mobility of 443 cm2/Vs with a carrier concentration of 2.50×1013 cm-2 at room temperature was achieved in the AlN/GaN heterostructures by using a polarization-induced GaN channel. The low depletion capacitance of 15 pF is resolved by the capacitance-voltage. These results indicate that the polarization-induced AlN/GaN heterostructures have great potential for next-generation high-temperature, high-frequency, and high-power electronics.

Keywords: AlN, GaN, MBE, heterostructures

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Authors: Srikantan L. Jayasri, James Gan

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The changes in Singapore’s land use, natural preference of long-tailed macaques (Macaca fascicularis) to live in forest edges and their adaptability has led to interface between humans and macaques. Studies have shown that two-third of human-macaque interactions in Singapore were related to human food. We aimed to assess differences among macaques groups in their dependence on human food and interaction with humans as indicators of the level of interface. Field observations using instantaneous scan sampling and all occurrence ad-lib sampling were carried out for 23 macaque groups over 28 days recording 71.5 hours of observations. Data on macaque behaviour, demography, frequency, and nature of human-macaque interactions were collected. None of the groups were found to completely rely on human food source. Of the 23 groups, 40% of them were directly or indirectly provisioned by humans. One-third of the groups observed engaged in some form of interactions with the humans. Three groups that were directly fed by humans contributed to 83% of the total human-macaque interactions observed during the study. Our study indicated that interactions between humans and macaques exist in specific groups and in those fed by humans regularly. Although feeding monkeys is illegal in Singapore, such incidents seem to persist in specific locations. We emphasize the importance of group and location-specific assessment of the existing human-wildlife interactions. Conflict management strategies developed should be location specific to address the cause of interactions.

Keywords: primates, Southeast Asia, wildlife management, Singapore

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Authors: Yun Sun, Meng Xun, Jingtao Zhou, Ming Li, Qiang Kan, Zhi Jin, Xinyu Liu, Dexin Wu

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Higher speed short-wavelength vertical-cavity surface-emitting lasers (VCSELs) working at high temperature are required for future optical interconnects. In this work, the high-speed 850 nm VCSELs are designed, fabricated and characterized. The temperature dependent static and dynamic performance of devices are investigated by using current-power-voltage and small signal modulation measurements. Temperature-stable high-speed properties are obtained by employing highly strained multiple quantum wells and short cavity length of half wavelength. The temperature dependent photon lifetimes and carrier radiative times are determined from damping factor and resonance frequency obtained by fitting the intrinsic optical bandwidth with the two-pole transfer function. In addition, an analytical theoretical model including the strain effect is development based on model-solid theory. The calculation results indicate that the better high temperature performance of VCSELs can be attributed to the strong confinement of holes in the quantum wells leading to enhancement of the carrier transit time.

Keywords: vertical cavity surface emitting lasers, high speed modulation, optical interconnects, semiconductor lasers

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Authors: Barenten Suciu, Ryoichi Kinoshita

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In this paper, an experimental and theoretical study on the bogie pseudo-hunting motion of a reduced-scale model railway vehicle, running on double-curved rails, is presented. Since the actual bogie hunting motion, occurring for real railway vehicles running on straight rails at high travelling speeds, cannot be obtained in laboratory conditions, due to the speed and wavelength limitations, a pseudo- hunting motion was induced by employing double-curved rails. Firstly, the test rig and the experimental procedure are described. Then, a geometrical model of the double-curved rails is presented. Based on such model, the variation of the carriage rotation angle relative to the bogies and the working conditions of the yaw damper are clarified. Vibration spectra recorded during vehicle travelling, on straight and double-curved rails, are presented and interpreted based on a simple vibration model of the railway vehicle. Ride comfort of the vehicle is evaluated according to the ISO 2631 standard, and also by using some particular frequency weightings, which account for the discomfort perceived during the reading and writing activities. Results obtained in this work are useful for the adequate design of the yaw dampers, which are used to attenuate the lateral vibration of the train car bodies.

Keywords: double-curved rail, octave analysis, vibration model, ride comfort, railway vehicle

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Authors: N. Guo, C. Xu, Z. C. Yang

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In order to ensure the high reliability of an aircraft, the accurate structural dynamics analysis has become an indispensable part in the design of an aircraft structure. Therefore, the structural finite element model which can be used to accurately calculate the structural dynamics and their transfer relations is the prerequisite in structural dynamic design. A dynamic finite element model updating method is presented to correct the uncertain parameters of the finite element model of a structure using measured modal parameters. The coordinate modal assurance criterion is used to evaluate the correlation level at each coordinate over the experimental and the analytical mode shapes. Then, the weighted summation of the natural frequency residual and the coordinate modal assurance criterion residual is used as the objective function. Moreover, the hybrid pattern search (HPS) optimization technique, which synthesizes the advantages of pattern search (PS) optimization technique and genetic algorithm (GA), is introduced to solve the dynamic FE model updating problem. A numerical simulation and a model updating experiment for GARTEUR aircraft model are performed to validate the feasibility and effectiveness of the present dynamic model updating method, respectively. The updated results show that the proposed method can be successfully used to modify the incorrect parameters with good robustness.

Keywords: model updating, modal parameter, coordinate modal assurance criterion, hybrid genetic/pattern search

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Authors: Hakeem Ade Omokayode Idowu

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The extent of the role played by human capabilities developments as well as knowledge management on employees’ performance in the nuclear energy sector of Nigeria remains unclear. This is in view of the important role which human resource capabilities could play in the desire to generate energy using nuclear resources. This study appraised the extent of human resource capabilities available in the nuclear energy sector of Nigeria. It further examined the relationship between knowledge management and employees’ performance in the nuclear energy sector. The study adopted a descriptive research design with a population that comprised all the 1736 members of staff of the selected centres, institutes, and the headquarters of the Nigeria Atomic Energy Commission (NAEC), Nigerian Nuclear Regulatory Authority (NNRA), and Energy Commission of Nigeria (ECN) and a sample size of 332 employees was selected using purposive and convenience sampling techniques. Data collected were subjected to analysis using frequency counts and simple regression. The results showed that majority of the employees perceived that they have to a high extent of availability of knowledge (118, 35.5%), credibility (134, 40.4%), alignment (130, 39.2%), performance (126, 38%) and innovation (138, 41.6%) The result of the hypothesis tested indicated that knowledge management has a positive and significant effect on employees’ performance (Beta weight = 0.336, R2 =0.113, F-value = 41.959, p-value = 0.000< 0.05). The study concluded that human resource capabilities and knowledge management could enhance employee performance within the nuclear energy sector of Nigeria.

Keywords: human resource capabilities, knowledge management, employees productivity, national development

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Authors: Javeria Ahmad, Ayesha Maryam, Zahid Rizwan, Nadeem Nasir, Yasir Nawab, Hafiz Shehbaz Ahmad

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Mitigation of electromagnetic interference (EMI) through thin, lightweight, and cost-effective materials is critical for electronic appliances as well as human health. The present research work discusses the design of composites that are suitable to minimize EMI through various stacking sequences. The carbon fibers reinforced composite structures impregnated with dielectric (MWCNTs) and magnetic nanofillers (Fe₂O₃) were developed to investigate their microwave absorption properties. The composite structure comprising a single type of nanofillers, each of MWCNTs & Fe₂O₃, was developed, and then their layers were stacked over each other with various stacking sequences to investigate the best stacking sequence, which presents good microwave absorption characteristics. A vector network analyzer (VNA) was used to analyze the microwave absorption properties of these developed composite structures. The composite structures impregnated with the layers of a dielectric nanofiller and sandwiched between the layers of a magnetic nanofiller show the highest EMI shielding value of 59 dB and a dielectric conductivity of 35 S/cm in the frequency range of 0.1 to 13.6 GHz. The results also demonstrate that the microwave absorption properties of the developed composite structures were dominant over reflection properties. The absence of an external peak in X-ray diffraction (XRD), marked the purity of the added nanofillers.

Keywords: nanocomposites, microwave absorption, EMI shielding, skin depth, reflection loss

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Authors: Okunola Solomon Olufemi

Abstract:

The study focused on the contribution of urban agriculture to the livelihood of 107 respondents in Kwara State of Nigeria. The study employed structured questionnaire to collect relevant data for the study while descriptive statistics such as frequency distribution and percentage were employed to analyses the objectives. Most respondents (82.9%), were one time or the other in a married state and they had formal education (80.4%) while many of the lot (58.9%) had superior education ranging from OND to Ph.D level. These farmers were either retired government workers or those trying to argument their family income or trying to be food sufficient. Most of the respondents (77.4%) had a farm size of less than or equal to 3 hectares showing that most the urban farmers were smallholders which might be as a result of stiff completion for land resource. Most of the respondents had a relatively large family size of 6 and above members. Most respondents used family labor (59.8%). Respondents in the study area also made use of the cooperatives and daily contributions for loanable funds, while few respondents utilized the formal sector. .Urban agriculture accounted for 84.4% of the Livelihood outcomes of the respondents. While non-farming activities contributed 17.6%.Most of the respondents (31.8%) participated in non-farming activities to generate extra income while their major constraints were shortage of land both in term of access and tenure (34.1%), limited access to resource and agricultural inputs (29.3%), and prohibitive urban policies and regulation (23.2%).

Keywords: poverty throes, urban agriculture, rigors of farming, non-farming, married state

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Authors: Fereshteh Pourmohammad, Mehdi Zare

Abstract:

The city of Karaj, having a population of 2.2 millions (est. 2022) is located in the South West of Alborz Mountain Belt in Northern Iran. The region is known to be a highly active seismic zone. This study is focused on the geological and seismological analyses within a radius of 200 km from the center of Karaj. There are identified five seismic zones and seven linear seismic sources. The maximum magnitude was calculated for the seismic zones. Scine tghe seismicity catalog is incomplete, we have used a parametric-historic algorithm and the Kijko and Sellevoll (1992) method was used to calculate seismicity parameters, and the return periods and the probability frequency of recurrence of the earthquake magnitude in each zone obtained for 475-years return period. According to the calculations, the highest and lowest earthquake magnitudes of 7.6 and 6.2 were respectively obtained in Zones 1 and 4. This result is a new and extremely important in view point of earthquake risk in a densely population city. The maximum strong horizontal ground motion for the 475-years return period 0.42g and for 2475-year return period 0.70g also the maximum strong vertical ground motion for 475-years return period 0.25g and 2475-years return period 0.44g was calculated using attenuation relationships. These acceleration levels are new, and are obtained to be about 25% higher than presented values in the Iranian building code.

Keywords: seismic zones, ground motion, return period, hazard analysis

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Authors: A. Benatiallah, D. Benatiallah, F. Abaidi, B. Nasri, A. Harrouz, S. Mansouri

Abstract:

The region of Adrar is located in the south-western Algeria and covers a total area of 443.782 km², occupied by a population of 432,193 inhabitants. The main activity of population is agriculture, mainly based on the date palm cultivation occupies a total area of 23,532 ha. Adrar region climate is a continental desert characterized by a high variation in temperature between months (July, August) it exceeds 48°C and coldest months (December, January) with 16°C. Rainfall is very limited in frequency and volume with an aridity index of 4.6 to 5 which corresponds to a type of arid climate. Geologically Adrar region is located on the edge North West and is characterized by a Precambrian basement cover stolen sedimentary deposit of Phanerozoic age transgressive. The depression is filled by Touat site Paleozoic deposits (Cambrian to Namurian) of a vast sedimentary basin extending secondary age of the Saharan Atlas to the north hamada Tinhirt Tademaït and the plateau of south and Touat Gourara west to Gulf of Gabes in the Northeast. In this work we have study geothermal potential of Adrar region from the borehole data eatable in various sites across the area of 400,000 square kilometres; from these data we developed a GIS (Adrar_GIS) that plots data on the various points and boreholes in the region specifying information on available geothermal potential has variable depths.

Keywords: sig, geothermal, potenteil, temperature

Procedia PDF Downloads 448

Authors: Emil Danehorn, Ulla Peterson, Marie Oscarsson, Goldina Smirthwaite, Katarina Swahnberg

Abstract:

Swedish students who choose to study abroad are common, but there has been limited research on exchange students. There are indications that some Swedish exchange students have been exposed to violence, but it is not known if they, already before their semester abroad, are more exposed to violence than students who remain on campus. Our aim was to investigate potential differences in exposure to physical, sexual, and emotional violence between prospective exchange students and campus students and between male and female students in general, as well as to determine any associations between mental health and exposure to violence among students in the total sample. Method: Comparative cross-sectional design using an online survey containing the NorVold Abuse Questionnaire and the General Health Questionnaire 12. A total of 565 participants took part in the study. Results: Prospective exchange students were less exposed to emotional violence compared to campus students. About one-half of all the participating female students had been exposed to sexual violence and about one-third of all the male students had been exposed to physical violence. The results also indicated that exposure to more than one form of violence was associated with poor mental health for students as a group. Conclusion: Prospective exchange students as a group do not report more exposure to physical and sexual violence than campus students but do report less exposure to emotional violence. However, the overall frequency of exposure to violence among the students was high. This highlights the need for proactive efforts for everyone, not least for exchange students who will be staying in a new environment unknown to them.

Keywords: sexual violence, physical violence, emotional violence, exchange students, mental health

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Authors: Kittipong Tripetch, Nobuhiko Nakano

Abstract:

This paper proposes one stage and two stage CMOS Complementary Regulated Cascode Distributed Amplifier (CRCDA) design based on Inductive and Transformer coupling techniques. Usually, Distributed amplifier is based on inductor coupling between gate and gate of MOSFET and between drain and drain of MOSFET. But this paper propose some new idea, by coupling with differential primary windings of transformer between gate and gate of MOSFET first stage and second stage of regulated cascade amplifier and by coupling with differential secondary windings transformer of MOSFET between drain and drain of MOSFET first stage and second stage of regulated cascade amplifier. This paper also proposes polynomial modeling of Silicon Transformer passive equivalent circuit from Nanyang Technological University which is used to extract frequency response of transformer. Cadence simulation results are used to verify validity of transformer polynomial modeling which can be used to design distributed amplifier without Cadence. 4 parameters of scattering matrix of 2 port of the propose circuit is derived as a function of 4 parameters of impedance matrix.

Keywords: CMOS regulated cascode distributed amplifier, silicon transformer modeling with polynomial, low power consumption, distribute amplification technique

Procedia PDF Downloads 489

Authors: W. Swiderski

Abstract:

In the paper introduced the diagnostic technique making possible the research of internal structures in composite materials reinforced fibres using in different applications. The main reason of damages in structures of these materials is the changing distribution of load in constructions in the lifetime. Appearing defect is largely complicated because of the appearance of disturbing of continuity of reinforced fibres, binder cracks and loss of fibres adhesiveness from binders. Defect in composite materials is usually more complicated than in metals. At present, infrared thermography is the most effective method in non-destructive testing composite. One of IR thermography methods used in non-destructive evaluation is vibrothermography. The vibrothermography is not a new non-destructive method, but the new solution in this test is use ultrasonic waves to thermal stimulation of materials. In this paper, both modelling and experimental results which illustrate the advantages and limitations of ultrasonic IR thermography in inspecting composite materials will be presented. The ThermoSon computer program for computing 3D dynamic temperature distribuions in anisotropic layered solids with subsurface defects subject to ulrasonic stimulation was used to optimise heating parameters in the detection of subsurface defects in composite materials. The program allows for the analysis of transient heat conduction and ultrasonic wave propagation phenomena in solids. The experiments at MIAT were fulfilled by means of FLIR SC 7600 IR camera. Ultrasonic stimulation was performed with the frequency from 15 kHz to 30 kHz with maximum power up to 2 kW.

Keywords: composite material, ultrasonic, infrared thermography, non-destructive testing

Procedia PDF Downloads 279

Authors: Bi Zhao

Abstract:

Neural network technology has greatly improved the output of machine translation in terms of both fluency and accuracy, which greatly increases its appeal for young users. The present exploratory study aims to find out how the Chinese undergraduates perceive and use machine translation in their daily life. A survey is conducted to collect data from 100 undergraduate students from multiple Chinese universities and with varied academic backgrounds, including arts, business, science, engineering, and medicine. The survey questions inquire about their use (including frequency, scenarios, purposes, and preferences) of and attitudes (including trust, quality assessment, justifications, and ethics) toward machine translation. Interviews and tasks of evaluating machine translation output are also employed in combination with the survey on a sample of selected respondents. The results indicate that Chinese undergraduate students use machine translation on a daily basis for a wide range of purposes in academic, communicative, and entertainment scenarios. Most of them have preferred machine translation tools, but the availability of machine translation tools within a certain scenario, such as the embedded machine translation tool on the webpage, is also the determining factor in their choice. The results also reveal that despite the reportedly limited trust in the accuracy of machine translation output, most students lack the ability to critically analyze and evaluate such output. Furthermore, the evidence is revealed of the inadequate awareness of ethical responsibility as machine translation users among Chinese undergraduate students.

Keywords: Chinese undergraduates, machine translation, trust, usage

Procedia PDF Downloads 109