Search results for: high tunnel

Authors: Obasanjo Afolabi Bolarinwa

Abstract:

This study assesses the levels of knowledge of sexually transmitted infections among unmarried youths in Nigeria; examines the pattern of high risk sex among unmarried youths in Nigeria; investigate the socio-demographic factors (age, place of residence, religion, level of education, wealth index and employment status) affecting the practice of high-risk sexual behaviour and ascertain the relationships between knowledge of sexually transmitted infections and practice of high risk sex. The goal of the study is to identify the factors associated with the practice of high risk sex among youth. These were with a view to identifying critical actions needed to reduce high risk sexual behaviour among youths. The study employed secondary data. The data for the study were extracted from the 2013 Nigeria Demographic and Health Survey (NDHS). The 2013 NDHS collected information from 38,948 Women ages 15-49 years and 17,359 men ages 15-49. A total of 7,744 female and 6,027 male respondents were utilized in the study. In order to adjust for the effect of oversampling of the population, the weighting factor provided by Measure DHS was applied. The data were analysed using frequency distribution and logistic regression. The results show that both male (92.2%) and female (93.6%) have accurate knowledge of sexually transmitted infections. The study also revealed that prevalence of high risk sexual behavior is high among Nigerian youths; this is evident as 77.7% (female) and 78.4% (male) are engaging in high risk sexual behavior. The bivariate analysis shows that age of respondent (χ2=294.2; p < 0.05), religion (χ2=136.64; p < 0.05), wealth index (χ2=17.38; p < 0.05), level of education (χ2=34.73; p < 0.05) and employment status (χ2=94.54; p < 0.05) were individual factors significantly associated with high risk sexual behaviour among male while age of respondent (χ2=327.07; p < 0.05), place of residence (χ2=6.71; p < 0.05), religion (χ2=81.04; p < 0.05), wealth index (χ2=7.41; p < 0.05), level of education (χ2=18.12; p < 0.05) and employment status (χ2=51.02; p < 0.05) were individual factors significantly associated with high risk sexual behaviour among female. Furthermore, the study shows that there is a relationship between knowledge of sexually transmitted infections and high risk sex among male (χ2=38.32; p < 0.05) and female (χ2=18.37; p < 0.05). At multivariate level, the study revealed that individual characteristics such as age, religion, place of residence, wealth index, levels of education and employment status were statistically significantly related with high risk sexual behaviour among male and female (p < 0.05). Lastly, the study shows that knowledge of sexually transmitted infection was significantly related to high risk sexual behaviour among youths (p < 0.05). The study concludes that there is a high level of knowledge of sexually transmitted infections among unmarried youths in Nigeria. The practice of high risk sex is high among unmarried youths but higher among male youths. The prevalence of high risk sexual activity is higher for males when they are at disadvantage and higher for females when they are at advantage. Socio-demographic factors like age of respondents, religion, wealth index, place of residence, employment status and highest level of education are factors influencing high risk sexual behaviour among youths.

Keywords: high risk sex, wealth index, sexual behaviour, knowledge

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Authors: Ahmed A. Al-Mudhafar, Ali A. Abduljabar, Hayder Jawad Albattat

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This work suggests a new microwave resonator sensor (MRS) device for measuring the oil’s breakdown voltage of high voltage transformers. A precise high-sensitivity sensor is designed and manufactured based on a microstrip split ring resonator (SRR). To improve the sensor sensitivity, a RF amplifier of 30 dB gain is linked through a transmission line of 50Ω.The sensor operates at a microwave band (L) with a quality factor of 1.35x105 when it is loaded with an empty tube. In this work, the sensor has been tested with three samples of high voltage transformer oil of different ages (new, middle, and damaged) where the quality factor differs with each sample. A mathematical model was built to calculate the breakdown voltage of the transformer oils and the accuracy of the results was higher than 90%.

Keywords: active resonator sensor, oil breakdown voltage, transformers oils, quality factor

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Authors: Ioannis Panagiotopoulos, Aristidis Anastasakis, Konstantinos Toutouzas, Ioannis Iakovou, Charalampos Vlachopoulos, Vasilis Voudris, Georgios Tziomalos, Konstantinos Tsioufis, Efstathios Kastritis, Alexandros Briassoulis, Kimon Stamatelopoulos, Alexios Antonopoulos, Paraskevi Exadaktylou, Evanthia Giannoula, Anastasia Katinioti, Maria Kalantzi, Evangelos Leontiadis, Eftychia Smparouni, Ioannis Malakos, Nikolaos Aravanis, Argyrios Doumas, Maria Koutelou

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Introduction: Cardiac amyloidosis from Transthyretin (ATTR-CA) is an infiltrative disease characterized by the deposition of pathological transthyretin complexes in the myocardium. This study describes the characteristics of patients diagnosed with ATTR-CA from 2019 until present at the Nuclear Medicine Department of Onassis Cardiac Surgery Center and AHEPA Hospital. These centers have extensive experience in amyloidosis and modern technological equipment for its diagnosis. Materials and Methods: Records of consecutive patients (N=73) diagnosed with any type of amyloidosis were collected, analyzed, and prospectively followed. The diagnosis of amyloidosis was made using specific myocardial scintigraphy with Tc-99m DPD. Demographic characteristics, including age, gender, marital status, height, and weight, were collected in a database. Clinical characteristics, such as amyloidosis type (ATTR and AL), serum biomarkers (BNP, troponin), electrocardiographic findings, ultrasound findings, NYHA class, aortic valve replacement, device implants, and medication history, were also collected. Some of the most significant results are presented. Results: A total of 73 cases (86% male) were diagnosed with amyloidosis over four years. The mean age at diagnosis was 82 years, and the main symptom was dyspnea. Most patients suffered from ATTR-CA (65 vs. 8 with AL). Out of all the ATTR-CA patients, 61 were diagnosed with wild-type and 2 with two rare mutations. Twenty-eight patients had systemic amyloidosis with extracardiac involvement, and 32 patients had a history of bilateral carpal tunnel syndrome. Four patients had already developed polyneuropathy, and the diagnosis was confirmed by DPD scintigraphy, which is known for its high sensitivity. Among patients with isolated cardiac involvement, only 6 had left ventricular ejection fraction below 40%. The majority of ATTR patients underwent tafamidis treatment immediately after diagnosis. Conclusion: In conclusion, the experiences shared by the two centers and the continuous exchange of information provide valuable insights into the diagnosis and management of cardiac amyloidosis. Clinical suspicion of amyloidosis and early diagnostic approach are crucial, given the availability of non-invasive techniques. Cardiac scintigraphy with DPD can confirm the presence of the disease without the need for a biopsy. The ultimate goal still remains continuous education and awareness of clinical cardiologists so that this systemic and treatable disease can be diagnosed and certified promptly and treatment can begin as soon as possible.

Keywords: amyloidosis, diagnosis, myocardial scintigraphy, Tc-99m DPD, transthyretin

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Authors: Mohamad Farhat, Bal Virdee

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This paper present a compact Microstrip Bandpass filter exhibiting a very wide stop band and high selectivity. The filter comprises of asymmetric resonator structures, which are interconnected by an inter-digital capacitor to enable the realization of a wide bandwidth with high rejection level. High selectivity is obtained by optimizing the parameters of the interdigital capacitor. The filter has high out-of-band rejection (> 30 dB), less than 0.6 dB of insertion-loss, up to 5.5 GHz spurii free, and about 18 dB of return-loss. Full-wave electromagnetic simulator ADSTM (Mom) is used to analyze and optimize the prototype bandpass filter. The proposed technique was verified practically to validate the design methodology. The experimental results of the prototype circuit are presented and a good agreement was obtained comparing with the simulation results. The dimensions of the proposed filter are 32 x 24 mm2.The filter’s characteristics and compact size make it suitable for wireless communication systems.

Keywords: asymmetric resonator, bandpass filter, microstrip, spurious suppression, ultra-wide stop band

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Authors: Muhammad Habib, Lin Tang, Guoliang Xue, Attaur Rahman, Myong-Ho Kim, Soonil Lee, Xuefan Zhou, Yan Zhang, Dou Zhang

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Designing a high-performance, lead-free ceramic has become a cutting-edge research topic due to growing concerns about the toxic nature of lead-based materials. In this work, a convenient strategy of compositional design and domain engineering is applied to the lead-fee BiFeO₃-BaTiO₃ ceramics, which provides a flexible polarization-free-energy profile for domain switching. Here, simultaneously enhanced dynamic piezoelectric constant (d33* = 772 pm/V) and a good thermal-stability (d33* = 26% over the temperature of 20-180 ᵒC) are achieved with a high Curie temperature (TC) of 432 ᵒC. This high piezoelectric strain performance is collectively attributed to multiple effects such as thermal quenching, suppression of defect charges by donor doping, chemically induced local structure heterogeneity, and electric field-induced phase transition. Furthermore, the addition of BT content decreased octahedral tilting, reduced anisotropy for domain switching and increased tetragonality (cₜ/aₜ), providing a wider polar length for B-site cation displacement, leading to high piezoelectric strain performance. Atomic-resolution transmission electron microscopy and piezoelectric force microscopy combined with X-ray diffraction results strongly support the origin of high piezoelectricity. The high and temperature-stable piezoelectric strain response of this work is superior to those of other lead-free ceramics. The synergistic approach of composition design and the concept present here for the origin of high strain response provides a paradigm for the development of materials for high-temperature piezoelectric actuator applications.

Keywords: Piezoelectric, BiFeO3-BaTiO3, Quenching, Temperature-insensitive

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Authors: Bachir Belmadani, Rachid Taleb, M’hamed Helaimi

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Multilevel inverters are well used in high power electronic applications because of their ability to generate a very good quality of waveforms, reducing switching frequency, and their low voltage stress across the power devices. This paper presents the hybrid pulse-width modulation (HPWM) strategy of a uniform step asymmetrical cascaded H-bridge nine-level Inverter (USACHB9LI). The HPWM approach is compared to the well-known sinusoidal pulse-width modulation (SPWM) strategy. Simulation results demonstrate the better performances and technical advantages of the HPWM controller in feeding a high power induction motor.

Keywords: uniform step asymmetrical cascaded h-bridge high-level inverter, hybrid pwm, sinusoidal pwm, high power induction motor

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Authors: Ahmed E. Hodaib, Samar F. Abdel Fattah

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High-speed transportation is a growing concern. To develop high-speed rails and to increase high-speed efficiencies, the idea of Hyperloop was introduced. The challenge is to overcome the difficulties of managing friction and air-resistance which become substantial when vehicles approach high speeds. In this paper, we are presenting the methodologies of the capsule design which got a design concept innovation award at SpaceX competition in January, 2016. MATLAB scripts are written for the levitation and propulsion calculations and iterations. Computational Fluid Dynamics (CFD) is used to simulate the air flow around the capsule considering the effect of the axial-flow air compressor and the levitation cushion on the air flow. The design procedures of a single-sided linear induction motor are analyzed in detail and its geometric and magnetic parameters are determined. A structural design is introduced and Finite Element Method (FEM) is used to analyze the stresses in different parts. The configuration and the arrangement of the components are illustrated. Moreover, comments on manufacturing are made.

Keywords: high-speed transportation, hyperloop, railways transportation, single-sided linear induction Motor (SLIM)

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Authors: S. S. Awanti, Aravindakumar B. Harwalkar

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Concrete construction in future has to be environmental friendly apart from being safe so that society at large is benefited by the huge investments made in the infrastructure projects. To achieve this, component materials of the concrete system have to be optimized with reference to sustainability. This paper presents a study on development of mix proportions of high volume fly ash concrete (HFC). A series of HFC mixtures with cement replacement levels varying between 50% and 65% were prepared with water/binder ratios of 0.3 and 0.35. Compressive strength values were obtained at different ages. From the experimental results, pozzolanic efficiency ratios and mix design curves for HFC were established.

Keywords: age factor, compressive strength, high volume fly ash concrete, pozolanic efficiency ratio

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Authors: A. Bahadoran, M. Zomorodian

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The synthesizer of cobalt oxide nanoballs (length 3−4 μm, width 250−400 nm) was achieved by a simple high-temperature supercritical solution method. Multiwalled carbon aerogels are a step towards high-density nanometer-scale nanostructures. Cobalt oxide nanoballs were prepared by supercritical solution method. Synthesis in an aqueous solution containing cobalt hydroxide at ∼80 °C without any further heat treatment at high temperature. The formation of cobalt oxide nanoballs on carbon aerogel was confirmed by X-ray diffraction and Raman spectroscopy. The FE-SEM images showed the presence of cobalt oxide nanoballs. The reaction mechanism of the ultrasound-assisted synthesis of cobalt oxide nanostructures was proposed on the basis of the XRD, X-ray absorption spectroscopy analysis and FE-SEM observation of the reaction products taken during the course of the synthesis.

Keywords: cobalt oxide nano balls, carbon aerogel, synthesize, nanostructure

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Authors: Robert J. Thomas, Colton Bedke, Andrew Sorensen

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The exemplary mechanical performance and durability of ultra-high performance concrete (UHPC) has led to its rapid emergence as an advanced cementitious material. The uncharacteristically high mechanical strength and ductility of UHPC makes it a promising potential material for defense structures which may be subject to highly dynamic loads like impact or blast. However, the mechanical response of UHPC under dynamic loading has not been fully characterized. In particular, there is a need to characterize the energy absorption of UHPC under high-frequency shear loading. This paper presents preliminary results from a parametric study of the dynamic shear energy absorption of UHPC using the Charpy impact test. UHPC mixtures with compressive strengths in the range of 100-150 MPa exhibited dynamic shear energy absorption in the range of 0.9-1.5 kJ/m. Energy absorption is shown to be sensitive to the water/cement ratio, silica fume content, and aggregate gradation. Energy absorption was weakly correlated to compressive strength. Results are highly sensitive to specimen preparation methods, and there is a demonstrated need for a standardized test method for high frequency shear in cementitious composites.

Keywords: Charpy impact test, dynamic shear, impact loading, ultra-high performance concrete

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Authors: Silvia Arrate, Waldo Salud, Eloy París

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The wear of cutting tools is one of the most decisive elements when planning tunneling works, programming the maintenance stops and saving the optimum stock of spare parts during the evolution of the excavation. Being able to predict the behavior of cutting tools can give a very competitive advantage in terms of costs and excavation performance, optimized to the needs of the TBM itself. The incredible evolution of data science in recent years gives the option to implement it at the time of analyzing the key and most critical parameters related to machinery with the purpose of knowing how the cutting head is performing in front of the excavated ground. Taking this as a case study, Metro Line 3 of Guadalajara in Mexico will develop the feasibility of using Specific Energy versus data science applied over parameters of Torque, Penetration, and Contact Force, among others, to predict the behavior and status of cutting tools. The results obtained through both techniques are analyzed and verified in the function of the wear and the field situations observed in the excavation in order to determine its effectiveness regarding its predictive capacity. In conclusion, the possibilities and improvements offered by the application of digital tools and the programming of calculation algorithms for the analysis of wear of cutting head elements compared to purely empirical methods allow early detection of possible damage to cutting tools, which is reflected in optimization of excavation performance and a significant improvement in costs and deadlines.

Keywords: cutting tools, data science, prediction, TBM, wear

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Authors: Xiping Guo, Fanglin Ge, Ping Guan

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Refractory high entropy alloys are alternative materials expected to be employed at high temperatures. The comprehensive changes of microstructure and properties of NbTiZrCrAl refractory high entropy alloys are systematically studied by adjusting Al content. Five kinds of button alloy ingots with different contents of Al in NbTiZrCrAlX (X=0, 0.2, 0.5, 0.75, 1.0) were prepared by vacuum non-consumable arc melting technology. The microstructure analysis results show that the five alloys are composed of BCC solid solution phase rich in Nb and Ti and Laves phase rich in Cr, Zr, and Al. The addition of Al changes the structure from hypoeutectic to hypereutectic, increases the proportion of Laves phase, and changes the structure from cubic C15 to hexagonal C14. The hardness and fracture toughness of the five alloys were tested at room temperature, and the compressive mechanical properties were tested at 1000℃. The results showed that the addition of Al increased the proportion of Laves phase and decreased the proportion of the BCC phase, thus increasing the hardness and decreasing the fracture toughness at room temperature. However, at 1000℃, the strength of 0.5Al and 0.75Al alloys whose composition is close to the eutectic point is the best, which indicates that the eutectic structure is of great significance for the improvement of high temperature strength of NbTiZrCrAl refractory high entropy alloys. The five alloys were oxidized for 1 h and 20 h in static air at 1000℃. The results show that only the oxide film of 0Al alloy falls off after oxidizing for 1 h at 1000℃. After 20h, the oxide film of all the alloys fell off, but the oxide film of alloys containing Al was more dense and complete. By producing protective oxide Al₂O₃, inhibiting the preferential oxidation of Zr, promoting the preferential oxidation of Ti, and combination of Cr₂O₃ and Nb₂O₅ to form CrNbO₄, Al significantly improves the high temperature oxidation resistance of NbTiZrCrAl refractory high entropy alloys.

Keywords: NbTiZrCrAl, refractory high entropy alloy, al content, microstructural evolution, room temperature mechanical properties, high temperature compressive strength, oxidation resistance

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Authors: Farid Adisaputra Gumilang

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Kucing Liar Underground Mine is a future mine of PT Freeport Indonesia PTFI that is currently being developed. In the development process, problems were found when blasting the tunnels; there were overbreak, and void occur caused by geological contact or poor rock conditions. Geotechnical engineers must evaluate not only the remnant capacity of ground support systems but also investigate the depth of rock mass yield within pillars. To prevent the potential hazard caused by void zones, geotechnical engineers must ensure the planned drift is mined in the best location where people can work safely. GPR, or Ground penetrating radar, is a geophysical method that can image the subsurface. This non-destructive method uses electromagnetic radiation and detects the reflected signals from subsurface structures. The GPR survey measurements are conducted 48 meters along the drift that has a poor ground condition with 150MHz antenna with several angles (roof, wall, and floor). Concern grounds are determined by the continuity of reflector/low reflector in the radargram section. Concern grounds are determined by the continuity of reflector/low reflector in the radargram section. In this paper, processing data using instantaneous amplitude to identify the void zone. In order to have a good interpretation and result, it combines with the geological information and borehole camera data, so the calibrated GPR data allows the geotechnical engineer to determine the safe location to change the drift location.

Keywords: underground mine, ground penetrating radar, reflectivity, borehole camera

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Authors: Emdad K. Z. Balanji, M. Neaz Sheikh, Muhammad N. S. Hadi

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This paper presents results of an experimental investigation on the behaviour of Hybrid Steel Fibre Reinforced High Strength Concrete (HSFR-HSC) cylinder specimens (150 mm x 300 mm) under uniaxial compression. Three different combinations of HSFR-HSC specimens and reference specimens without steel fibres were prepared. The first combination of HSFR-HSC included 1.5% Micro Steel (MS) fibre and 1% Deformed Steel (DS) fibre. The second combination included 1.5% MS fibre and 1.5% Hooked-end Steel (HS) fibre. The third combination included 1% DS fibre and 1.5% HS fibre. The experimental results showed that the addition of hybrid steel fibres improved the ductility of high strength concrete. The combination of MS fibre and HS fibre in high strength concrete mixes showed best stress-strain behaviour compared to the other combinations and the reference specimens.

Keywords: high strength concrete, micro steel fibre (MS), deformed steel fibre (DS), hooked-end steel fibre (HS), hybrid steel fibre

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Authors: Aman Kaur, Colin Ribton, Wamadeva Balachandaran

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Electron beam welding due to its inherent advantages is being extensively used for material processing where high precision is required. Especially in aerospace or nuclear industries, there are high quality requirements and the cost of materials and processes is very high which makes it very important to ensure the beam quality is maintained and checked prior to carrying out the welds. Although the processes in these industries are highly controlled, however, even the minor changes in the operating parameters of the electron gun can make large enough variations in the beam quality that can result in poor welding. To measure the beam quality a simple device has been designed that can be used at high powers. The device consists of two slits in x and y axis which collects a small portion of the beam current when the beam is deflected over the slits. The signals received from the device are processed in data acquisition hardware and the dedicated software developed for the device. The device has been used in controlled laboratory environments to analyse the signals and the weld quality relationships by varying the focus current. The results showed matching trends in the weld dimensions and the beam characteristics. Further experimental work is being carried out to determine the ability of the device and signal processing software to detect subtle changes in the beam quality and to relate these to the physical weld quality indicators.

Keywords: electron beam welding, beam quality, high power, weld quality indicators

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Authors: Sevana Daneghian, Leila Chodari, Sahar Mehranfar, Shadi Mohammadpour-Asl, Diman Mahdi

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Sarcopenia is an age-related muscle disease. Lack of antioxidant protection, and cumulative oxidative damage to skeletal muscle are recognized mechanisms. Curcumin is a hormetin as it has a stimulating effect in low doses and an inhibitory effect in high doses. The purpose of this study was to examine the effects of four weeks of curcumin supplementation in presarcopenic and sarcopenic rats, and likelihood of potential negative effects while co-exist with sarcopenia. The rats were divided into 7 groups: young sham rats, 18 months old; presarcopenic control, supplemented with 400 and 1500 mg/kg/day, 24 months old; Sarcopenia control, sarcopenia supplemented with 400 and 1500 mg/kg/day. MDA levels were significantly reduced in the low-dose pre-sarcopenic group compared to the control group. Compared to the corresponding control groups, SOD levels decreased in the groups treated with low-dose presarcopenic supplementation and increased in the high-dose sarcopenic supplemented. GPx levels increased at both doses only in the sarcopenic group compared to the control group. SIRT-1 only increased at low doses in the sarcopenic groups and PGC-1α in both pre-sarcopenia groups compared to the corresponding control. IGF-1 increased compared to the control group at both doses in the pre-sarcopenic group and at high doses in sarcopenic group. Considering the hormetic effects of curcumin, it can be argued that, curcumin supplementation has some positive effects not only at low but also at high doses in both groups. This means that the high doses of curcumin have no negative synergistic effects in addition to oxidative stress during sarcopenia and high-dose supplementation in patients already suffering from high oxidative stress due to sarcopenia is safe and could be considered hormetic.

Keywords: curcumin, hormesis, sarcopenia, muscular atrophy, PGC protein, Sirtuins

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Authors: Richard Chen

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The study is mainly focused on the influence of different kinds of friendships on the well being of Chinese high school students. The main objective is to find out whether friendship style focusing on depth rather than breadth and whether making friends based on similarities in personality and character rather than interests and hobbies improve students’ mental state. Overall, 262 high school participants completed our study by filling out questionnaires online across China. Data showed, unexpectedly, optimal combinations of friendship styles indicate that students who seek depth of connection in friendship benefit more by focusing more on hobbies than on personalities, and those aiming to expand their social connections would be happier and less stressed when they made friends with those who shared their personalities rather than hobbies. The relationship between stress and the frequency of self-talk was also investigated, and a positive correlation between the pressure a student felt, and the frequency of self-talk behavior was confirmed. The results shed light on relationship management and wellbeing among Chinese high school students and may be applied by counselors and teachers to improve the overall level of satisfaction for Chinese high school students.

Keywords: hobbies, personalities, happiness, pressure, self-talk

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Authors: Syali Pradhan, Neetu Jha

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The Marigold flower is used in religious places for offering and decoration purpose every day. The flowers are discarded near trees or in aquatic bodies. This floral waste can be used for extracting dyes or oils. Still the secondary waste remains after processing which need to be addressed. This research aims to provide green and clean power using secondary floral waste available after processing. The carbonization of floral waste produce carbon material with high surface area and enhance active site for more reaction. The Hybrid supercapacitors are more stable, offer improved operating temperature and use less toxic material compared to battery. They provide enhanced energy density compared to supercapacitors. Hence, hybrid supercapacitor designed using waste material would be more practicable for future energy application. Here, we present the utilization of carbonized floral waste as supercapacitor electrode material. This material after carbonization gets graphitized and shows high surface area, optimum porosity along with high conductivity. Hence, this material has been tested as cathode electrode material for high performance zinc storage hybrid supercapacitor. High energy storage along with high stability has been obtained using this cathodic waste material as electrode.

Keywords: marigold, flower waste, energy storage, cathode, supercapacitor

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Authors: Yaner Yan, Ning Li, Yajun Qiao, Shuqing An

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Although most studies have focused on assessing and mapping terrestrial ecosystem services, there is still a knowledge gap on coastal ecosystem services and an urgent need to assess them. Lau (2013) clearly defined five types of costal ecosystem services: carbon sequestration, shoreline protection, fish nursery, biodiversity, and water quality. While high-resolution remote sensing can provide the more direct, spatially estimates of biophysical parameters, such as species distribution relating to biodiversity service, and Fluorescence information derived from remote sensing direct relate to photosynthesis, availing in estimation of carbon sequestration and the response to environmental changes in coastal wetland. Here, we review the capabilities of high-resolution and fluorescence remote sesing for describing biodiversity, vegetation condition, ecological processes and highlight how these prodicts may contribute to costal ecosystem service assessment. In so doing, we anticipate rapid progress to combine the high-resolution and fluorescence remote sesing to estimate the spatial pattern of costal ecosystem services.

Keywords: ecosystem services, high resolution, remote sensing, chlorophyll fluorescence

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Authors: Ziyu Zhang, Xuanyu Ren, Fei Wu, Qinfei Lu, Yongmei Li, Xinyue Zhi

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Introduction: Adolescents experience a critical period of physical and psychological growth. Few studies focus on the influence of sleep hygiene on psychological health from the high school period to freshmen year. Also, the influence of the COVID-19 pandemic has public health significance. Methods: Totally 698 students from high school and college were included in the manuscript, and a cross-sectional procedure was conducted; the objective was to make the epidemiological comparison of the social phobia/depression prevalence and discuss the effects of potential determinants. Results: Psychological problems, including social phobia and depression, are prevalent, especially among high school students, with gender differences. The current results indicated that the association between sleep status and social phobia is most obvious among high school students, while the higher MMR risk was found both for high school social phobia students and college depressive freshmen. Moreover, the interaction between social phobia and depression was also obvious for both populations. Conclusions: Psychological problems, including social phobia and depression, are more prevalent among high school girls when compared with their male and freshmen peers. Important influenced factors for the risk of psychological problems among the two populations were different, but media multitasking status should be paid attention to for both.

Keywords: adolescence, psychological health, epidemiology, social culture

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Authors: Hassan Irshad Bhatti, Saravanan Yuvaraja, Xiaohang Li

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GaN-based devices, such as high electron mobility transistors (HEMTs), offer superior characteristics for high-power, high-frequency, and high-temperature applications [1]. However, this exceptional electrical performance is compromised by undesirable self-heating effects under high-power applications [2, 3]. Some of the issues caused by self-heating are current collapse, thermal runway and performance degradation [4, 5]. Therefore, accurate and reliable methods for measuring the temperature of individual devices on a chip are needed to monitor and control the thermal behavior of GaN-based devices [6]. Temperature measurement at the micro/nanoscale is a challenging task that requires specialized techniques such as Infrared microscopy, Raman thermometry, and thermoreflectance. Recently, micro-thermocouples (MTCs) have attracted considerable attention due to their advantages of simplicity, low cost, high sensitivity, and compatibility with standard fabrication processes [7, 8]. A micro-thermocouple is a junction of two different metal thin films, which generates a Seebeck voltage related to the temperature difference between a hot and cold zone. Integrating MTC in a device allows local temperature to be measured with high sensitivity and accuracy [9]. This work involves the fabrication and integration of micro-thermocouples (MTCs) to measure the channel temperature of GaN HEMT. Our fabricated MTC (Platinum-Chromium junction) has shown a sensitivity of 16.98 µV/K and can measure device channel temperature with high precision and accuracy. The temperature information obtained using this sensor can help improve GaN-based devices and provide thermal engineers with useful insights for optimizing their designs.

Keywords: Electrical Engineering, Thermal engineering, Power Devices, Semiconuctors

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Authors: George Mahalu

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The Chua diode has been configured over time in various ways, using electronic structures like operational amplifiers (AOs) or devices with gas or semiconductors. When discussing the use of semiconductor devices, tunnel diodes (Esaki diodes) are most often considered, and more recently, transistorized configurations such as lambda diodes. The paperwork proposed here uses in the modeling a lambda diode type configuration consisting of two junction field effect transistors (JFET). The original scheme is created in the MULTISIM electronic simulation environment and is analyzed in order to identify the conditions for the appearance of evolutionary unpredictability specific to nonlinear dynamic systems with chaos-induced behavior. The chaotic deterministic oscillator is one autonomous type, a fact that places it in the class of Chua’s type oscillators, the only significant and most important difference being the presence of a nonlinear device like the one mentioned structure above. The chaotic behavior is identified both by means of strange attractor-type trajectories and visible during the simulation and by highlighting the hypersensitivity of the system to small variations of one of the input parameters. The results obtained through simulation and the conclusions drawn are useful in the further research of ways to implement such constructive electronic solutions in theoretical and practical applications related to modern small signal amplification structures, to systems for encoding and decoding messages through various modern ways of communication, as well as new structures that can be imagined both in modern neural networks and in those for the physical implementation of some requirements imposed by current research with the aim of obtaining practically usable solutions in quantum computing and quantum computers.

Keywords: chua, diode, memristor, chaos

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Authors: Seongsoo Lee

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Motion estimation occupies the heaviest computation in HEVC (high efficiency video coding). Many fast algorithms such as TZS (test zone search) have been proposed to reduce the computation. Still the huge computation of the motion estimation is a critical issue in the implementation of HEVC video codec. In this paper, motion estimator architecture with optimized number of PEs (processing element) is presented by exploiting early termination. It also reduces hardware size by exploiting parallel processing. The presented motion estimator architecture has 8 PEs, and it can efficiently perform TZS with very high utilization of PEs.

Keywords: motion estimation, test zone search, high efficiency video coding, processing element, optimization

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Authors: Cheng-Lin Liu, Fei Liu

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For the multi-agent systems with agent's dynamics described by high-order integrator, and usual consensus algorithm composed of the state coordination control parts is proposed. Under communication delay, consensus algorithm in asynchronously-coupled form just can make the agents achieve a stationary consensus, and sufficient consensus condition is obtained based on frequency-domain analysis. To recover the original consensus state of the high-order agents without communication delay, besides, a predictor-based consensus algorithm is constructed via multiplying the delayed neighboring agents' states by a delay-related compensation part, and sufficient consensus condition is also obtained. Simulation illustrates the correctness of the results.

Keywords: high-order dynamic agents, communication delay, consensus, predictor-based algorithm

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Authors: Rachid Taleb, M’hamed Helaimi, Djilali Benyoucef, Ahmed Derrouazin

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Multilevel inverters are well used in high power electronic applications because of their ability to generate a very good quality of waveforms, reducing switching frequency, and their low voltage stress across the power devices. This paper presents the Optimal Minimization of the Total Harmonic Distortion (OMTHD) strategy of a uniform step asymmetrical seven-level inverter (USA7LI). The OMTHD approach is compared to the well-known sinusoidal pulse-width modulation (SPWM) strategy. Simulation results demonstrate the better performances and technical advantages of the OMTHD controller in feeding a High Power Induction Motor (HPIM).

Keywords: uniform step asymmetrical seven-level inverter (USA7LI), optimal minimization of the THD (OMTHD), sinusoidal PWM (SPWM), high power induction motor (HPIM)

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Authors: M. Farnush

Abstract:

This study is concerned with the microstructural analysis and improvement of wear resistance of 356 aluminum alloy by a high energy electron beam. Shock hardening on material by high energy electron beam improved wear resistance. Particularly, in the surface of material by shock hardening, the wear resistance was greatly enhanced to 29% higher than that of the 356 aluminum alloy substrate. These findings suggested that surface shock hardening using high energy electron beam irradiation was economical and useful for the development of surface shock hardening with improved wear resistance.

Keywords: Al356 alloy, HEEB, wear resistance, frictional characteristics

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Authors: T. Toathom, M. Munlin, P. Sugunnasil

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The traveling salesman problem (TSP) is one of the best-known problems in optimization problem. There are many research regarding the TSP. One of the most usage tool for this problem is the genetic algorithm (GA). The chromosome of the GA for TSP is normally encoded by the order of the visited city. However, the traditional chromosome encoding scheme has some limitations which are twofold: the large solution space and the inability to encapsulate some information. The number of solution for a certain problem is exponentially grow by the number of city. Moreover, the traditional chromosome encoding scheme fails to recognize the misplaced correct relation. It implies that the tradition method focuses only on exact solution. In this work, we relax some of the concept in the GA for TSP which is the exactness of the solution. The proposed work exploits the relation between cities in order to reduce the solution space in the chromosome encoding. In this paper, a second order GA is proposed to solve the TSP. The term second order refers to how the solution is encoded into chromosome. The chromosome is divided into 2 types: the high order chromosome and the low order chromosome. The high order chromosome is the chromosome that focus on the relation between cities such as the city A should be visited before city B. On the other hand, the low order chromosome is a type of chromosome that is derived from a high order chromosome. In other word, low order chromosome is encoded by the traditional chromosome encoding scheme. The genetic operation, mutation and crossover, will be performed on the high order chromosome. Then, the high order chromosome will be mapped to a group of low order chromosomes whose characteristics are satisfied with the high order chromosome. From the mapped set of chromosomes, the champion chromosome will be selected based on the fitness value which will be later used as a representative for the high order chromosome. The experiment is performed on the city data from TSPLIB.

Keywords: genetic algorithm, traveling salesman problem, initial population, chromosomes encoding

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Authors: Palanisamy Samyraj, Sriram Yogesh, Kishore Kumar, Vaishak Cibi

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The project is about design and analysis of crankshaft using Al-Al2O3 composite material. The project is mainly concentrated across two areas one is to design and analyze the composite material, and the other is to work on the practical model. Growing competition and the growing concern for the environment has forced the automobile manufactures to meet conflicting demands such as increased power and performance, lower fuel consumption, lower pollution emission and decrease noise and vibration. Metal matrix composites offer good properties for a number of automotive components. The work reports on studies on Al-Al2O3 as the possible alternative material for a crank shaft. These material have been considered for use in various components in engines due to the high amount of strength to weight ratio. These materials are significantly taken into account for their light weight, high strength, high specific modulus, low co-efficient of thermal expansion, good air resistance properties. In addition high specific stiffness, superior high temperature, mechanical properties and oxidation resistance of Al2O3 have developed some advanced materials that are Al-Al2O3 composites. Crankshafts are used in automobile industries. Crankshaft is connected to the connecting rod for the movement of the piston which is subjected to high stresses which cause the wear of the crankshaft. Hence using composite material in crankshaft gives good fuel efficiency, low manufacturing cost, less weight.

Keywords: metal matrix composites, Al-Al2O3, high specific modulus, strength to weight ratio

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Authors: Ahmad Hashim, Zarizi Ab Rahman

Abstract:

Measurement of body composition via a field method has the most popular instruments which are used to estimate the percentage of body fat. Among the instruments used are the Body Mass Index, Bio Impedance Analysis and Skinfold Test. All three of these instruments do not involve high costs, do not require high technical skills, are mobile, save time, and are suitable for use in large populations. Because all three instruments can estimate the percentage of body fat, but it is important to identify the most appropriate instruments and have high reliability. Hence, this study was conducted to determine the reliability and convergent validity of the instruments. A total of 40 students, males and females aged between 13 and 14 years participated in this study. The study found that the test retest and Pearson correlation coefficient of reliability for the three instruments is very high, r = .99. While the inter class reliability also are at high level with r = .99 for Body Mass Index and Bio Impedance Analysis, r = .96 for Skin fold test. Intra class reliability coefficient for these three instruments is too high for Body Mass Index r = .99, Bio Impedance Analysis r = .97, and Skin fold Test r = .90. However, Standard Error of Measurement value for all three instruments indicates the Body Mass Index is the most appropriate instrument with a mean value of .000672 compared with other instruments. The findings show that the Body Mass Index is an instrument which is the most accurate and reliable in estimating body fat percentage for the population studied.

Keywords: reliability, validity, body mass index, bio impedance analysis and skinfold test

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Authors: M. Beyzaiea, S. Mohammadia

Abstract:

High aspect ratio metallic (silver, cobalt) nanowire arrays were fabricated using ac electrodeposition techniques into the nanoporous alumina template. The template with long pore dept fabricated by hard anodization (HA) and thinned for ac electrodeposition. Template preparation was done in short time by using HA technique and high speed thing process. The TEM and XRD investigation confirm the three dimensional nucleation growth mechanism of metallic nanowire inside the nanoporous alumina that fabricated by HA process.

Keywords: metallic, nanowire, nanoporous alumina, ac electrodeposition

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