Statistical evaluation of a liquid desiccant dehumidification system using RSM and theoretical study based on the effectiveness NTU model

L. Omidvar Langroudi,H. Pahlavanzadeh,S.M. Mousavi 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5

In the present study the performance of an air dehumidifier using lithium bromide (LiBr) as a desiccant was investigated. Response surface methodology (RSM) was used to assess individual and interactive effects of the six main factors (velocity, temperature and humidity of air, flow rate, temperature and concentration of desiccant) on dehumidification mass rate. A reduced quadratic statistical model was derived to predict dehumidification mass rate. The maximum dehumidification mass rate was obtained 0.154 g/s under the optimal conditions of an air velocity of 4.1 m/s, desiccant flow rate of 0.035 kg/s, air humidity ratio of 0.0185 kg/kg, desiccant concentration of 0.48 kg/kg, air temperature of 29.5 ℃, and desiccant temperature of 21.8 ℃. The effectiveness number of transfer unit (NTU) model was employed to describe the coupled heat and mass transfer. The results of the model and the experimental data show good agreement. Dimensionless mass and heat transfer coefficients correlations are proposed; the average absolute differences between the predicted values and the experimental findings for Sh and Nu numbers were calculated as 2.14% and 5.27%, with the discrepancies mainly within ±9% and ±13%, respectively.

Tuning New Fuzzy Control for Nonlinear Second Order System

Babak Ranjbar,Gholam Dashti,Ali Omidvar,Javad Mahmoodi,Hasan Karbasi 보안공학연구지원센터 2014 International Journal of Hybrid Information Techno Vol.7 No.6

Cognitive method is used in this research to create portfilo of movement robot manipulator. Gradient descent (GD) fuzzy controller was used and robot’s postures and trajectory were expected in MATLAB/SIMULINK environment. Fuzzy logic controller (FLC) is an influential nonlinear controller to certain and uncertain systems which it is based on artificial intelligent and computes the required torques using the nonlinear feedback control law. Practically a large amount of systems have uncertainties accordingly this method has a challenge. Linear proportional-integral-derivative (PID) controller is a significant combination nonlinear stable-robust controller under condition of partly uncertain dynamic parameters of system. This technique is used to control of highly nonlinear systems especially in nonlinear time varient nonlinear dynamic system. To compensate for the dependence on model-free parameters, PID methodology is used. The nonlinear model dynamic formulation problem in uncertain system can be solved by using PID theorem. Proportional-Derivative-Integral (PID) theory is used to estimate the system dynamic.

Competitive adsorption of arsenic and mercury on nano-magnetic activated carbons derived from hazelnut shell

Mojtaba Zabihi,Omidvar Maryam,Alireza Motavalizadehkakhky,Rahele Zhiani 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.2

Magnetic activated carbons (AC) derived from hazelnut shell using the chemical activation method with ZnCl2 and KOH were prepared in the present work. The adsorption performance of the magnetic sorbents was evaluated for the removal of mercury and arsenic ions in the binary solutions, and the interference of ions with each other during the adsorption process was investigated. The synthesized adsorbents were characterized using XRD, FTIR, BET, XRF, FESEM, TGA and VSM. The XRD results indicated that the small iron oxide crystallites, including goethite and magnetite, were detected on the hazelnut shell-based AC activated by ZnCl2. The extended Langmuir and the modified competitive Langmuir isotherms were applied to fit the competitive adsorption of Hg (II) and As (V) ions using genetic algorithm (GA). The experimental data were in good agreement with the extended Langmuir equation, while the correlation coefficient was measured close to 1. The highest adsorption capacity was calculated to be 80 and 39.31 mg/g for mercury and arsenic ions on the magnetic sample activated by ZnCl2, respectively. The kinetic behavior of carbonaceous adsorbents was studied using pseudo-first and second-order models. The effect of various operating conditions was investigated on the competitive adsorption of metal ions.

TRIPLE CENTRALIZERS OF C^* -ALGEBRAS

Davarpanah, Seyed Mohammad,Omidvar, Mohsen Erfanian,Moradi, Hamid Reza The Kangwon-Kyungki Mathematical Society 2018 한국수학논문집 Vol.26 No.4

In this paper, we extend the concept of double centralizer to triple centralizer and we show that, the triple centralizer is a $C^*$-algebra. Some algebraic properties are investigated.

Food frequency questionnaires developed and validated in Iran: a systematic review

Arezoo Rezazadeh,Nasrin Omidvar,Katherine L,Tucker 한국역학회 2020 Epidemiology and Health Vol.42 No.-

OBJECTIVES: To systematically review and identify food frequency questionnaires (FFQs) developed for the Iranian population and their validation and reproducibility in order to determine possible research gaps and needs. METHODS: Studies were selected by searching for relevant keywords in the PubMed, Scopus, Science Direct, Google Scholar, SID, and Iranmedex databases, unpublished data, and theses in November 2016 (updated in September 2019). All English-language and Persian-language papers were included. Duplicates, articles with unrelated content, and articles only containing a protocol were excluded. The FFQs were categorized based on: (1) number of food items in to short (≤80 items) and long (>80 items) and; (2) the aim of the FFQ to explore total consumption pattern/nutrients (general) or to detect specific nutrient(s)/food group(s) (specialized). RESULTS: Sixteen reasonably validated questionnaires were identified. However, only 13 presented a reproducibility assessment. Ten FFQs were categorized as general (7 long, 3 short) and 6 as specialized (3 long, 3 short). The correlation coefficients for nutrient intake between dietary records or recalls and FFQs were 0.07-0.82 for long (general: 0.07-0.82 and specialized: 0.26-0.67) and 0.20-0.67 for short (general: 0.24-0.54 and specialized: 0.20-0.42) FFQs. Long FFQs showed higher validity and reproducibility than short FFQs. Reproducibility of FFQs was acceptable (0.32-0.89). The strongest correlations were reported by studies with shorter intervals between FFQs. CONCLUSIONS: FFQs designed for the Iranian population appear to be appropriate tools for dietary assessment. Despite their acceptable reproducibility, their validity for assessing specific nutrients and their applicability for populations other than those they were developed for may be questionable.

A novel nanocomposite as adsorbent for formaldehyde removal from aqueous solution

Hejri, Zahra,Hejri, Mehri,Omidvar, Maryam,Morshedi, Sadjad Techno-Press 2020 Advances in nano research Vol.8 No.1

In order to develop a new adsorbent for removal of formaldehyde from aqueous solution, surface modification of TiO₂ nanoparticles was performed with 2,4-Dinitrophenylhydrazine (DNPH) that have a strong affinity to the formaldehyde. Sodium dodecyl sulfate (SDS) surfactant was used to improve the DNPH grafting to TiO₂ surface. Modified adsorbents were characterized by SEM, TEM, XRD, EDX and FTIR. Since the COD level in wastewaters including formaldehyde is considerable, it is necessary to determine the COD content of the synthetic wastewater. In order to determine the optimal removal conditions, the effect of contact time (60-210 min), pH (4-10) and adsorbent dosage (0.5-1.5 g/L) on adsorption and COD removal efficiencies were studied, using response surface method. EDX and FTIR analysis confirmed the presence of nitrogen-containing functional groups on the modified TiO₂ surface. The maximum formaldehyde adsorption and COD removal efficiencies by modified TiO₂ were about 15.65 and 7.35% higher than the unmodified nanoparticles respectively. Therefore, the grafting of nano-TiO₂ with DNPH would greatly improve its formaldehyde adsorption efficiency. The optimum conditions determined for a maximum formaldehyde removal of 99.904% and a COD reduction of 94.815% by TiO₂/SDS/DNPH nanocomposites were: adsorbent dosage 1.100 g/L, pH 7.424 and the contact time 183.290 min.

Adapting the Community Readiness Model and Validating a Community Readiness Tool for Childhood Obesity Prevention Programs in Iran

Mahdieh Niknam,Nasrin Omidvar,Parisa Amiri,Hassan Eini-Zinab,Naser Kalantari 대한예방의학회 2023 예방의학회지 Vol.56 No.1

Objectives: It is critical to assess community readiness (CR) when implementing childhood obesity prevention programs to ensure their eventual success and sustainability. Multiple tools have been developed based on various conceptions of readiness. One of the most widely used and flexible tools is based on the community readiness model (CRM). This study aimed to adapt the CRM and assess the validity of a community readiness tool (CRT) for childhood obesity prevention programs in Iran. Methods: A Delphi study that included 26 individuals with expertise in 8 different subject areas was conducted to adapt the CRM into a theoretical framework for developing a CRT. After linguistic validation was conducted for a 35-question CR interview guide, the modified interview guide was evaluated for its content and face validity. The quantitative and qualitative analyses were performed using Stata version 13 and MAXQDA 2010, respectively. Results: The Delphi panelists confirmed the necessity/appropriateness and adequacy of all 6 CRM dimensions. The Persian version of the interview guide was then modified based on the qualitative results of the Delphi study, and 2 more questions were added to the community climate dimension of the original CRT. All questions in the modified version had acceptable content and face validity. The final CR interview guide included 37 questions across 6 CRM dimensions. Conclusions: By adapting the CRM and confirming linguistic, content, and face validity, the present study devised a CRT for childhood obesity prevention programs that can be used in relevant studies in Iran.

An experimental study on the mechanisms of enhancing oil recovery by nanoparticles-assisted surfactant flood

Sina Mobaraki,Mahdi Zakavi,Omid Mahmoodi,Milad Omidvar Sorkhabadi,Seyyed Shahram Khalilinezhad,Reza Shiri Torkmani 한국자원공학회 2020 Geosystem engineering Vol.23 No.6

The central concern of this study is to examine the synergic effects of an anionic surfactant and hydrophilic silica nanoparticles on the improvement of surfactant properties. The assessment of the effect of silica nanoparticles on the emulsification ability of the surfactant solution was performed by the use of both electrical conductivity measurements and phase behavior tests. Accordingly, an optimal chemical formulation for the utilized crude oil was suggested. Optical absorption technique was also employed to evaluate the stability of the optimal solution. The oil recovery experiments were carried out in a transparent glass micromodel saturated with crude oil to monitor some pore-scale displacement events during the simultaneous flow of the optimal solution and the crude oil through porous media. Phase behavior tests indicated that the silica nanoparticles are effective in terms of Interfacial tension (IFT) reduction since they can achieve ultra-low IFT level. The results of conductivity experiments proved the ability of silica nanoparticles to reduce the Critical Micelle Concentration (CMC) of the surfactant. The stability tests proved that the optimal solution is stable for a reasonable time. The multiphase flow experiments revealed that oil recovery increased by about 5% during nanoparticles-assisted surfactant flooding compared with surfactant flood.

Neighbourhood morphology, genuine self-expression and place attachment, the case of Tehran neighbourhoods

Hossein Khosravi,Hossein Bahrainy,Shadi Omidvar Tehrani 서울시립대학교 도시과학연구원 2020 도시과학국제저널 Vol.24 No.3

In this paper, the neighbourhood’s morphology has been evaluated according to socio-behavioural aspects and sense of place. It seems that place attachment, social bonding, and total time residents spent in local spaces are highly determined by neighbourhood’s socio-behavioural dimensions, and in turn, neighbourhood’s morphological attributes have a great impact on socio-behavioural dimensions. To verify the hypothesis, 843 participants have been selected through Neyman allocation modelling from 5 morphologically representative neighbourhoods. The built-environment attributes were gathered through an objective method (GIS). Sense of place, meantime residents, spent in public spaces, socio-behavioural indicators, and a number of socio-demographic characteristics were collected by self-administered questionnaires. According to our analysis, high and middle-rise neighbourhoods, with low coverage massing, by providing plenty of wide, non-hierarchical, and inter-connected spaces, could ensure personal privacy, anonymity, and consequently autonomy, genuineness, and tendency to use neighbourhood spaces. In contrast, historic organic neighbourhoods with narrow hierarchical pathways and massing alongside them increase the level of social monitoring and conformity. Thus, policies that support mixed-use, connected street networks, plenty of shared open spaces, non- hierarchical network patterns, and smaller block sizes can be used by urban designers to promote neighbourhoods supporting residents’ psycho-social preferences.

Advanced Approach to Modify Friction Stir Spot Welding Process

Behrouz Bagheri,Mahmoud Abbasi,Amin Abdollahzadeh,Hamid Omidvar 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.10

Nowadays, friction stir spot welding (FSSW) is used in automotive, rail vehicle construction, the aerospace industry, andelectrical industry. In the current research, a modified version of the FSSW process entitled friction stir spot vibration weldingwas introduced to join Al5083 specimens. The joining specimens were vibrated normal to the tool movement direction,while the joint position cooled by passing coolant through the fixture. Different characteristics of developed joint namelymicrostructure, mechanical properties, corrosion behavior were studied. The results showed that stir zone grain size decreasedsignificantly as the vibration was employed and the joint position was cooled. It was found that vibration enhanced thedynamic recrystallization and coolant decreased the grain growth. Both led to enhanced grain refinement in the stir zone. The results also indicated that shear strength and hardness of the weld region increased as the modified version of FSSWwas applied. Corrosion tests revealed that corrosion resistance increased as the modified method was applied.