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.

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.

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.

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.

A New Method for Developing Seismic Collapse Fragility Curves Grounded on State-Based Philosophy

Aref Baharvand,Abdolrasoul Ranjbaran 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.2

Since the current process to achieve the collapse fragility curve in practical applications seems too complicated, also time-consuming to dominant by structure designers, the focus of this study is on introducing of a new approach for establishing collapse fragility curves which requires less analytical effort. To achieve this goal, state-based philosophy (SBP) has been taken into consideration. This theory benefits from some similarities in the nature of every failure process in solid mechanics regardless of its source. In this study these similarities are used intelligently in procedure of formulating new fragility function which has couple of unknown parameters. Next, it will be shown that these parameters can be attained from two different sources: the pushover curves of the structure, some selective damage data from incremental dynamic analysis analyses. Finally a complete form of new collapse fragility function which is called "SBP fragility function" proposed as a substitute for conventional collapse fragility function. The most important advantage of this new fragility function is its non-probabilistic structure that will make a huge difference in the amount of effort required to achieve the fragility curves. In this research, in order to ensure the efficiency, accuracy of this fragility function all steps of SBP fragility analyses are done on some special moment frames models, their results are presented.

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%.

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

Characterization of relatively demicompact operators by means of measures of noncompactness

Aref Jeribi,Bilel Krichen,Makrem Salhi 대한수학회 2018 대한수학회지 Vol.55 No.4

In this paper, we show that an unbounded $S_{0}$-demicompact linear operator $T$ with respect to a bounded linear operator $S_{0}$, acting on a Banach space, can be characterized by the Kuratowskii measure of noncompactness. Moreover, some other quantities related to this measure provide sufficient conditions to the operator $T$ to be $S_{0}$-demicompact. The obtained results are used to discuss the connection with Fredholm and upper Semi-Fredholm operators.

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.

Compact electromagnetic vibration suppressor and energy harvester; an experimental study

Aref Afsharfard,Kyung Chun Kim,Hooman Zoka 국제구조공학회 2024 Smart Structures and Systems, An International Jou Vol.33 No.3

In this study, an electromagnetic dynamic vibration suppressor and energy harvester is designed and studied. In this system, a gear mechanism is used to convert the linear motion to continuous rotary motion. Governing equations of motion for the system are derived and validated using the experimental results. Effects of changing the main parameters of the presented system, such as mass ratio, stiffness ratio and gear ratio on the electro-mechanical behavior of system are investigated. Moreover, using so-called Weighted Cost Function, the optimum parameters of the system are obtained. Finally, it is shown that the presented electromagnetic dynamic vibration absorber not only can reduce the undesired vibration of the main system but also it can harvest acceptable electrical energy.