Computational study of a small scale vertical axis wind turbine (VAWT): comparative performance of various turbulence models

Lazaros Aresti,Mustafa Tutar,Yong Chen,Rajnish K. Calay 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.17 No.6

The paper presents a numerical approach to study of fluid flow characteristics and to predict performance of wind turbines. The numerical model is based on Finite-volume method (FVM) discretization of unsteady Reynolds-averaged Navier- Stokes (URANS) equations. The movement of turbine blades is modeled using moving mesh technique. The turbulence is modeled using commonly used turbulence models: Renormalization Group (RNG) k- turbulence model and the standard k- and k- turbulence models. The model is validated with the experimental data over a large range of tip-speed to wind ratio (TSR) and blade pitch angles. In order to demonstrate the use of numerical method as a tool for designing wind turbines, two dimensional (2-D) and three-dimensional (3-D) simulations are carried out to study the flow through a small scale Darrieus type H-rotor Vertical Axis Wind Turbine (VAWT). The flows predictions are used to determine the performance of the turbine. The turbine consists of 3- symmetrical NACA0022 blades. A number of simulations are performed for a range of approaching angles and wind speeds. This numerical study highlights the concerns with the self-starting capabilities of the present VAWT turbine. However results also indicate that self-starting capabilities of the turbine can be increased when the mounted angle of attack of the blades is increased. The 2-D simulations using the presented model can successfully be used at preliminary stage of turbine design to compare performance of the turbine for different design and operating parameters, whereas 3-D studies are preferred for the final design.

Coping With Korean Medium of Instruction For African Students Studying in Korean Universities

Andrea Lazaro,신서영 사단법인 미래융합기술연구학회 2019 아시아태평양융합연구교류논문지 Vol.5 No.4

The present study aimed to investigate how Africa students cope and adjust with Korean language as they pursue their studies in Korean universities. The study employed a qualitative approach which was informed by an ethnography case study. The findings revealed that international students from Africa had low proficiency in Korean language which led them to fail to actively participate in class discussion and normal interactions outside the classroom. It also challenged the students in coping with teaching and learning style leading to their failure to master well courses contents taught in Korean language. To overcome language problem students from Africa had to use English related textbooks or materials for courses taught in Korean; asking permission from course instructors to use English in writing assignments, presentations, tests, and university exams; asking for the help from Korean classmates in doing or preparing assignments and presentations in Korean; and using Google translator as strategies of coping and adjusting with Korean language as they pursue their studies in Korean universities. Based on these results, the study recommended that Universities need to design favourable programs to help international students to continue learning Korean language while pursuing their major degree programs.

Computational study of a small scale vertical axis wind turbine (VAWT): comparative performance of various turbulence models

Aresti, Lazaros,Tutar, Mustafa,Chen, Yong,Calay, Rajnish K. Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.17 No.6

The paper presents a numerical approach to study of fluid flow characteristics and to predict performance of wind turbines. The numerical model is based on Finite-volume method (FVM) discretization of unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The movement of turbine blades is modeled using moving mesh technique. The turbulence is modeled using commonly used turbulence models: Renormalization Group (RNG) k-${\varepsilon}$ turbulence model and the standard k-${\varepsilon}$ and k-${\omega}$ turbulence models. The model is validated with the experimental data over a large range of tip-speed to wind ratio (TSR) and blade pitch angles. In order to demonstrate the use of numerical method as a tool for designing wind turbines, two dimensional (2-D) and three-dimensional (3-D) simulations are carried out to study the flow through a small scale Darrieus type H-rotor Vertical Axis Wind Turbine (VAWT). The flows predictions are used to determine the performance of the turbine. The turbine consists of 3-symmetrical NACA0022 blades. A number of simulations are performed for a range of approaching angles and wind speeds. This numerical study highlights the concerns with the self-starting capabilities of the present VAWT turbine. However results also indicate that self-starting capabilities of the turbine can be increased when the mounted angle of attack of the blades is increased. The 2-D simulations using the presented model can successfully be used at preliminary stage of turbine design to compare performance of the turbine for different design and operating parameters, whereas 3-D studies are preferred for the final design.

Development of a Support Tool System for Evaluating the User Experience for Personal Mobility Devices (PMD)

May Jorella Lazaro,Sungho Kim,Adriance Wilfred Anggang,Jeong Heo,Jane Lee,Seung Yun Ha,Myung Hwan Yun 대한인간공학회 2021 대한인간공학회 학술대회논문집 Vol.2021 No.11

Objective: The purpose of this study is to design and develop a prototype of a support tool system for user experience (UX) designers to evaluate the UX of personal mobility devices (PMD) more effectively and efficiently. Background: Traffic problems continues to rise as the complexity of the transportation system grows. One of the solutions being employed to solve such issues is the use of personal mobility devices (PMD). PMDs are suitable for traveling at a faster speed and a more flexible route. Although the usage of PMDs continues to increase, there is still a lack of research with regards to the UX of PMDs due to characteristics of the device which is different from the conventional transport systems. Thus, a support tool to help UX designers specifically evaluate PMDs is essential. Method: The methodology for this study can be classified into three stages: research, ideation and prototyping. For the research stage, a review of the literature was conducted to collect information about how PMDs are being evaluated in terms of UX and to determine any gaps in the literature. After that, during the ideation stage, the results of the review were organized, and the hierarchy of information was structured based on multiple brainstorming sessions by the UX researchers. The brainstorming sessions also involved different design thinking techniques such as creating conceptual maps and flowcharts. Lastly, on the prototyping stage, low-fidelity and high-fidelity prototypes were developed to test and show the information architecture of the system. Results: The final prototype of the support tool system was created. The main features that were included in the system were: UX evaluation database, UX evaluation guide, and UX testing. Conclusion: This study developed a support tool for UX designers to help them better evaluate the UX specifically for PMDs. Application: The prototype of the system designed in this study can contribute to improving the efficiency and effectiveness of UX evaluation specifically for PMDs with further development and evaluation.

Echocardiographic indices in normal German shepherd dogs

Ruthnea Aparecida Lazaro Muzzi,, ,,Leonardo Augusto Lopes Muzzi,Roberto Baracat de Araujo,Marcos Cherem 대한수의학회 2006 Journal of Veterinary Science Vol.7 No.2

Emergency Department Healthcare Professionals" Usage and Satisfaction on Electronic Medical Record Systems in South Korea: A Structural Equation Modeling Approach

May Jorella S. Lazaro(엘라),Gee Won Shin(신지원),Gyungbhin Kim(김경빈),Sangwoo Bahn(반상우),Yura Lee(이유라),Jae-Ho Lee(이재호),Myung Hwan Yun(윤명환) 대한인간공학회 2020 대한인간공학회 학술대회논문집 Vol.2020 No.10

The Effects of Personality Traits on User’s Evaluation of Perceived Hedonic Quality

May Jorella S. Lazaro,Gee Won Shin,Jaramier Cobrado Joibi,Yein Song,Bania Putri,Myung Hwan Yun 대한산업공학회 2019 대한산업공학회 추계학술대회논문집 Vol.2019 No.11

COVID-19 transmission: a rapid systematic review of current knowledge

Panagiotis Mourmouris,Lazaros Tzelves,Christiana Roidi,Anastasia Fotsali 질병관리본부 2021 Osong Public Health and Research Persptectives Vol.12 No.2

Objectives: The objective of this study was to identify the potential and definite sources of transmission of coronavirus disease 2019 (COVID-19). Methods: Due to time constraints and the acute nature of the pandemic, we searched only PubMed/MEDLINE from inception until January 28, 2021. We analyzed the level of evidence and risk of bias in each category and made suggestions accordingly. Results: The virus was traced from its potential origin via possible ways of transmission to the last host. Symptomatic human-to-human transmission remains the driver of the epidemic, but asymptomatic transmission can potentially contribute in a substantial manner. Feces and fomites have both been found to contain viable virus; even though transmission through these routes has not been documented, their contribution cannot be ruled out. Finally, transmission from pregnant women to their children has been found to be low (up to 3%). Conclusion: Even though robust outcomes cannot be easily assessed, medical personnel must maintain awareness of the main routes of transmission (via droplets and aerosols from even asymptomatic patients). This is the first attempt to systematically review the existing knowledge to produce a paper with a potentially significant clinical impact.

Tragus formation during concha-type microtia repair using a chondrocutaneous island flap

하정현,정의철,Hudson Lazaro 대한두개안면성형외과학회 2018 Archives of Craniofacial Surgery Vol.19 No.1

Formation of an ideally-shaped tragus remains one of the most challenging issues during staged tragus reconstruction in microtia patients. The authors describe a new method used to treat a unique case of concha-type microtia in which the 10-year-old male patient had only a portion of pre-existing cartilage at the tragus site. An anomalous skin lump was also present. During the initial stages of the reconstruction, the two-stage Nagata method was used for surgical correction of the microtia. An autologous rib cartilage graft was used to form the ear framework. A temporoparietal fascia flap was also constructed. Remnant skin tags and anomalous cartilage that accompany microtia are usually removed during microtia repair. However, the cartilage and skin lump were preserved during the reconstruction. The skin lump was later used to form a vascularized chondrocutaneous island flap that supplemented the portion of cartilage during tragus formation. The result was a new tragus that was satisfactorily improved in both size and shape. Patients with concha-type microtia may benefit from the use of this new method for tragus formation.

e-Scooter Sharing System: UX Factor Investigation using Exploratory Factor Analysis

Adriance Wilfred,May Jorella Lazaro,Joong Hee Lee(이중희),Gyungbhin Kim(김경빈),Jeong Heo(허정),Donggun Park(박동건),Myung Hwan Yun(윤명환) 대한인간공학회 2021 대한인간공학회 학술대회논문집 Vol.2021 No.11

Objective: This research aims to investigate the user experience (UX) factors in the usage of e-scooter sharing system to aid the stakeholders to establish a sharing system which satisfies their e-scooter users. Background: The user population of e-scooters has rapidly increased 6 times in a single year from 2020 to 2021 in the Republic of Korea. E-scooter sharing system is expected to resolve traffic issues in metropolises. Furthermore, some countries borrowed and implemented the policies of car-sharing service for the e-scooter system in order to encourage the use of personal mobility device (PMD) when commuting in short distances. However, such policies are not directly applicable due to the differences in various contextual factors such as user characteristic, terrains, and products form factors. Therefore, there were insufficient research investigating the UX factors of e-scooter sharing system. Method: We conducted an online user survey with 42-item questionnaire which include items about pragmatic and hedonic qualities. All questionnaires were retrospective. A total of 315 participants (159 females and 156 males) residing in Seoul, who has experience in using e-scooter sharing systems participated in the survey. We conducted the Exploratory Factor Analysis (EFA) using IBM SPSS Statistics 26 software to determine and extract the significant UX factors. Results: The result of the analysis showed 9 UX factors, accounting for 74.771% of the variance. The extracted factors are as follows: (1) Ecological-and-Economical Friendly, (2) User Attitude and Engagement, (3) Perceived Usefulness, (4) Privacy and Security, (5) Perceived Ease-of-Use, (6) Tech-Enthusiastic, (7) Safety Concerns, (8) Environmental Concerns, and (9) Accessibility (Availability). Each factor showed reliable Cronbach’s alpha value of above 0.779. Conclusion: This study was able to identify 9 UX factors for e-scooter sharing systems. We expect there will be more increasing number of significant UX factors as the future of e-scooter sharing systems improve over the time. Application: Based on these results, we expect these findings would benefit and assist the designers and developers of the e-scooter sharing system in the future by considering the extracted UX factors.