Variable Speed Wind Turbine Control Using the Homotopy Perturbation Method

Arefe Shalbafian,Soheil Ganjefar 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.1

In this study, we present a method to obtain optimal control of the variable-speed fixed-pitch wind turbine using the homotopy perturbation method (HPM). In general, the optimal control problem for nonlinear systems should solve the Hamilton–Jacobi–Bellman (HJB) equation. The partial differential HJB equations that arise in optimal control problem, give closed-loop control law and it is difficult to obtain an exact solution of them for nonlinear systems. The main objective of this work is to employ the homotopy perturbation method to solve the HJB equation for a two-mass model of a wind turbine to capture the maximum power from the wind in below-rated wind speed. By applying this strategy, we obtained an approximate solution of the HJB equation for a two-mass model of the wind turbine with high accuracy. In the simulation section, we compare the results of the proposed HPM strategy with the nonlinear static state feedback control (NSSFE) approach. The presented results confirm that the HPM controller produces more electrical power while minimizing low-speed shaft oscillations by improving dynamic characteristics.

A Report of Health Related Anthropometric Indices in 2-5 Years Old Children of Golestan Province of Iran in 2015

Arefe Khaksar Jalali,Ahmadreza Dorosty Motlagh,Zahra Abdollahi,Ariyo Movahedi,Mina Minaie,Behnood Abbasi 한국임상영양학회 2019 Clinical Nutrition Research Vol.8 No.2

Pediatric malnutrition is an enormous health issue all around the world and its distribution is different in distinct areas of a country. This study has been designed to report the anthropometric status and some socio-economic factors among 2–5 years old children from Golestan province of Iran to show a better view of pediatric health status and better planning for future actions. This study was carried out by clustered-randomized sampling method on 1,382 of 2–5 years old children in urban and rural areas of Golestan province. Anthropometric measurements were performed and World Health Organization child growth standards were used for further analyses. The prevalence of stunting in boys and girls were 7.4% and 7.5% in urban and 4.1% and 5.4% in rural areas. The prevalence of underweight in boys and girls were 6.9% and 4.7% in urban and 5.7% and 4.4% in rural areas. The prevalence of subjects being at risk for overweight were 17.8% and 11.7% in boys and girls, respectively, in urban areas and were 11.1% and 9.2% in rural areas, respectively. There was a marginally significant difference between urban boys and girls in terms of weight status (p = 0.067). In this study remarkably high prevalence of malnutrition, especially a high dominance of overweight, was reported in Golestan province of Iran. Follow-up investigation to identify the cause of malnutrition and to establish public health policies are needed to revise these health issues in Golestan province of Iran.

Monolayer Molybdenum Disulfide Transistors with Single-Atom-Thick Gates

Zhu, Yibo,Li, Yijun,Arefe, Ghidewon,Burke, Robert A.,Tan, Cheng,Hao, Yufeng,Liu, Xiaochi,Liu, Xue,Yoo, Won Jong,Dubey, Madan,Lin, Qiao,Hone, James C. American Chemical Society 2018 NANO LETTERS Vol.18 No.6

<P>Two-dimensional transition-metal dichalcogenides (TMDs) are unique candidates for the development of next-generation electronic devices. However, the large contact resistance between metal and the monolayer TMDs have significantly limited the devices’ performance. Also, the integration of ultrathin high-<I>k</I> dielectric layers with TMDs remains difficult due to the lack of dangling bonds on the surface of TMDs. We present monolayer molybdenum disulfide field-effect transistors with bottom local gates consisting of monolayer graphene. The atomic-level thickness and surface roughness of graphene facilitate the growth of high-quality ultrathin HfO<SUB>2</SUB> and suppress gate leakage. Strong displacement fields above 8 V/nm can be applied using a single graphene gate to electrostatically dope the MoS<SUB>2</SUB>, which reduces the contact resistances between Ni and monolayer MoS<SUB>2</SUB> to 2.3 kΩ·μm at low gate voltages. The devices exhibit excellent switching characteristics including a near-ideal subthreshold slope of 64 millivolts per decade, low threshold voltage (∼0.5 V), high channel conductance (>100 μS/μm), and low hysteresis. Scaled devices with 50 and 14 nm channels as well as ultrathin (5 nm) gate dielectrics show effective immunity to short-channel effects. The device fabricated on flexible polymeric substrate also exhibits high performance and has a fully transparent channel region that is desirable in optical-related studies and practical applications.</P> [FIG OMISSION]</BR>

Multi-terminal transport measurements of MoS2 using a van der Waals heterostructure device platform.

Cui, Xu,Lee, Gwan-Hyoung,Kim, Young Duck,Arefe, Ghidewon,Huang, Pinshane Y,Lee, Chul-Ho,Chenet, Daniel A,Zhang, Xian,Wang, Lei,Ye, Fan,Pizzocchero, Filippo,Jessen, Bjarke S,Watanabe, Kenji,Taniguchi, Nature Pub. Group 2015 Nature nanotechnology Vol.10 No.6

<P>Atomically thin two-dimensional semiconductors such as MoS2 hold great promise for electrical, optical and mechanical devices and display novel physical phenomena. However, the electron mobility of mono- and few-layer MoS2 has so far been substantially below theoretically predicted limits, which has hampered efforts to observe its intrinsic quantum transport behaviours. Potential sources of disorder and scattering include defects such as sulphur vacancies in the MoS2 itself as well as extrinsic sources such as charged impurities and remote optical phonons from oxide dielectrics. To reduce extrinsic scattering, we have developed here a van der Waals heterostructure device platform where MoS2 layers are fully encapsulated within hexagonal boron nitride and electrically contacted in a multi-terminal geometry using gate-tunable graphene electrodes. Magneto-transport measurements show dramatic improvements in performance, including a record-high Hall mobility reaching 34,000???cm(2)???V(-1)???s(-1) for six-layer MoS2 at low temperature, confirming that low-temperature performance in previous studies was limited by extrinsic interfacial impurities rather than bulk defects in the MoS2. We also observed Shubnikov-de Haas oscillations in high-mobility monolayer and few-layer MoS2. Modelling of potential scattering sources and quantum lifetime analysis indicate that a combination of short-range and long-range interfacial scattering limits the low-temperature mobility of MoS2.</P>

Atomically thin p–n junctions with van der Waals heterointerfaces

Lee, Chul-Ho,Lee, Gwan-Hyoung,van der Zande, Arend M.,Chen, Wenchao,Li, Yilei,Han, Minyong,Cui, Xu,Arefe, Ghidewon,Nuckolls, Colin,Heinz, Tony F.,Guo, Jing,Hone, James,Kim, Philip Nature Publishing Group, a division of Macmillan P 2014 Nature nanotechnology Vol.9 No.9

Semiconductor p–n junctions are essential building blocks for electronic and optoelectronic devices. In conventional p–n junctions, regions depleted of free charge carriers form on either side of the junction, generating built-in potentials associated with uncompensated dopant atoms. Carrier transport across the junction occurs by diffusion and drift processes influenced by the spatial extent of this depletion region. With the advent of atomically thin van der Waals materials and their heterostructures, it is now possible to realize a p–n junction at the ultimate thickness limit. Van der Waals junctions composed of p- and n-type semiconductors—each just one unit cell thick—are predicted to exhibit completely different charge transport characteristics than bulk heterojunctions. Here, we report the characterization of the electronic and optoelectronic properties of atomically thin p–n heterojunctions fabricated using van der Waals assembly of transition-metal dichalcogenides. We observe gate-tunable diode-like current rectification and a photovoltaic response across the p–n interface. We find that the tunnelling-assisted interlayer recombination of the majority carriers is responsible for the tunability of the electronic and optoelectronic processes. Sandwiching an atomic p–n junction between graphene layers enhances the collection of the photoexcited carriers. The atomically scaled van der Waals p–n heterostructures presented here constitute the ultimate functional unit for nanoscale electronic and optoelectronic devices.

Natural Dyeing of Wool by Madder (Rubia tinctorum L.) Root Extract Using Tannin-based Biomordants: Colorimetric, Fastness and Tensile Assay

Aref Jahangiri,고레이시안,Ahmad Akbari,Mohammad Norouzi,Masoomeh Ghasemi,Maryamsadat Ghoreishian,Elham Shafiabadi 한국섬유공학회 2018 Fibers and polymers Vol.19 No.10

In this work, the natural dyeing behavior of woollen yarn with madder (Rubia tinctorum L.) root extract was studied. The effects of different tannin-rich plants (Rhus coriaria, Eucalyptus, Terminalia chebula, Quercus castaneifolia, Pomegranate) extract as biomordants and alum (as a chemical mordant) with two mordanting procedures (pre- and metamordanting) on color characteristics of the dyed samples were also investigated. The CIEDE2000 values, color strength (K/S), washing fastness and tensile property of the mordanted and dyed samples were assessed. Visually, a range of hues from orange to brownish-red were obtained. In general, pre-biomordanted samples with Rhus coriaria (10 %owf), Eucalyptus (10 %owf), Terminalia chebula (5 %owf), Quercus castaneifolia (5 %owf) and Pomegranate (5 %owf) showed almost the same color difference (ΔE00) and wash fastness values compared to those treated with 3 %owf alum. Finally, it was concluded from the comparative studies that the biomordants have good potential to be considered as alternatives to the common chemical mordants.

Design of Vibro-impact Electromagnetic Ocean-wave Energy Harvesting System

Aref Afsharfard(아레프 아프샤파드),Hyungmin Shin(신형민),Sajjad Hosseini(사자드 호쎄이니),Eun Soo Kim(김은수),Inwon Lee(이인원),Kyung Chun Kim(김경천) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

Dysarthric speaker identification with different degrees of dysarthria severity using deep belief networks

Aref Farhadipour,Hadi Veisi,Mohammad Asgari,Mohammad Ali Keyvanrad 한국전자통신연구원 2018 ETRI Journal Vol.40 No.5

Dysarthria is a degenerative disorder of the central nervous system that affects the control of articulation and pitch; therefore, it affects the uniqueness of sound produced by the speaker. Hence, dysarthric speaker recognition is a challenging task. In this paper, a feature‐extraction method based on deep belief networks is presented for the task of identifying a speaker suffering from dysarthria. The effectiveness of the proposed method is demonstrated and compared with well‐known Mel‐frequency cepstral coefficient features. For classification purposes, the use of a multi‐layer perceptron neural network is proposed with two structures. Our evaluations using the universal access speech database produced promising results and outperformed other baseline methods. In addition, speaker identification under both text‐dependent and text‐independent conditions are explored. The highest accuracy achieved using the proposed system is 97.3%.

Effect of Adding Scoria as Cement Replacement on Durability-Related Properties

Aref Mohamad al-Swaidani,Samira Dib Aliyan 한국콘크리트학회 2015 International Journal of Concrete Structures and M Vol.9 No.2

A lot of reinforced concrete (RC) structures in Syria went out of service after a few years of construction. This was mainly due to reinforcement corrosion or chemical attack on concrete. The use of blended cements is growing rapidly in the construction industry due to economical, ecological and technical benefits. Syria is relatively rich in scoria. In the study, mortar/concrete specimens were produced with seven types of cement: one plain Portland cement (control) and six blended cements with replacement levels ranging from 10 to 35 %. Rapid chloride penetration test was carried in accordance with ASTM C 1202 after two curing times of 28 and 90 days. The effect on the resistance of concrete against damage caused by corrosion of the embedded steel has been investigated using an accelerated corrosion test by impressing a constant anodic potential. The variation of current with time and time to failure of RC specimens were determined at 28 and 90 days curing. In addition, effects of aggressive acidic environments on mortars were investigated through 100 days of exposure to 5 % H₂SO₄, 10 % HCl, 5 % HNO₃ and 10 % CH₃COOH solutions. Evaluation of sulfate resistance of mortars was also performed by immersing in 5 % Na₂SO₄ solution for 52 weeks. Test results reveal that the resistance to chloride penetration of concrete improves substantially with the increase of replacement level, and the concretes containing scoria based-blended cements, especially CEM II/B-P, exhibited corrosion initiation periods several times longer than the control mix. Further, an increase in scoria addition improves the acid resistance of mortar, especially in the early days of exposure, whereas after a long period of continuous exposure all specimens show the same behavior against the acid attack. According to results of sulfate resistance, CEM II/B-P can be used instead of SRPC in sulfate-bearing environments.

Seismic Fragility Functions Grounded on State-Based Philosophy: Application to Low to Midrise Steel Frame Buildings

Aref Baharvand,Abdolrasoul Ranjbaran 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.6

In this study, a new formulation for structural fragility function based on the theory of state-based philosophy (SBP) is introduced. In this innovative approach, gradual changes in stiffness (or flexibility) of the structure is considered as a firm base for describing changes in the state of the structure due to damage from various sources. In this study, the source of damage data is considered ground motions. After formulating state changes by using SBP theory, a new fragility function is proposed. Therefore, this new function is based on observations of various failure stages of the structure and, besides, it is organized specifically for the structural damage data. In order to prove the accuracy of this method, some special moment frames (SMFs) are modeled, and incremental dynamic analysis (IDA) is performed on them. Thus damage data are provided as initial input to the fragility function. After that, the final results of the SBP fragility function are compared with the results of the conventional methods of plotting the fragility curve, and lastly, the fragility curve's accuracy obtained by using this new function is verified. This new fragility function is called ‘SBP fragility function’ and has some advantages over the ordinary fragility functions, which are discussed in this article.