• Title/Summary/Keyword: Re-closure

Search Result 58, Processing Time 0.022 seconds

Numerical Analysis of the Hydraulic Characteristics of a Boundary Layer Streaming over Surf-Zone Using LES and Dynamic Smagorinsky Turbulence Model (LES와 Dynamic Smagorinsky 난류모형을 이용한 쇄파역에서의 경계층 Streaming 수치해석)

  • Cho, Yong Jun
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • v.32 no.1
    • /
    • pp.69-84
    • /
    • 2020
  • Natural shoreline repeats its re-treatment and advance in response to the endlessly varying sea-conditions, and once severely eroded under stormy weather conditions, natural beaches are gradually recovered via a boundary layer streaming when swells are prevailing after storms cease. Our understanding of the boundary layer streaming over surf-zone often falls short despite its great engineering value, and here it should be noted that the most sediments available along the shore are supplied over the surf-zone. In this rationale, numerical simulation was implemented to investigate the hydraulic characteristics of boundary layer streaming over the surf zone in this study. In doing so, comprehensive numerical models made of Spatially filtered Navier-Stokes Eq., LES (Large Eddy Simulation), Dynamic Smagorinsky turbulence closure were used, and the effects of turbulence closure such as Dynamic Smagorinsky in LES and k-ε on the numerically simulated flow field were also investigated. Numerical results show that due to the intrinsic limits of k-ε turbulence model, numerically simulated flow velocity near the bottom based on k-ε model and wall function are over-predicted than the one using Dynamic Smagorinsky in LES. It is also shown that flow velocities near the bottom are faster than the one above the bottom which are relatively free from the presence of the bottom, complying the typical boundary layer streaming by Longuet-Higgins (1957), the spatial scope where boundary layer streaming are occurring is extended well into the surf zone as incoming waves are getting longer. These tendencies are plausible considering that it is the bottom friction that triggers a boundary layer streaming, and longer waves start to feel the bottom much faster than shorter waves.

SOME CLASSES OF MULTIVALENT FUNCTIONS WITH NEGATIVE COEFFICIENTS I

  • AUOF, M.K.;DARWISH, H.E.
    • Honam Mathematical Journal
    • /
    • v.16 no.1
    • /
    • pp.119-135
    • /
    • 1994
  • Let $Q_{n+p-1}(\alpha)$ denote the- dass of functions $$f(z)=z^{P}-\sum_{n=0}^\infty{a_{(p+k)}z^{p+k}$$ ($a_{p+k}{\geq}0$, $p{\in}N=\left{1,2,{\cdots}\right}$) which are analytic and p-valent in the unit disc $U=\left{z:{\mid}z:{\mid}<1\right}$ and satisfying $Re\left{\frac{D^{n+p-1}f(\approx))^{\prime}}{pz^{p-a}\right}>{\alpha},0{\leq}{\alpha}<1,n>-p,z{\in}U.$ In this paper we obtain sharp results concerning coefficient estimates, distortion theorem, closure theorems and radii of p-valent close-to- convexity, starlikeness and convexity for the class $Q_{n+p-1}$ ($\alpha$). We also obtain class preserving integral operators of the form $F(z)=\frac{c+p}{z^{c}}\int_{o}^{z}t^{c-1}f(t)dt.$ c>-p $F\left(z\right)=\frac{c+p}{z^{c}}\int_{0}^{z} t^{c-1}f\left(t \right)dt. \qquad c>-p$ for the class $Q_{n+p-1}$ ($\alpha$). Conversely when $F(z){\in}Q_{n+p-1}(\alpha)$, radius of p-valence of f(z) has been determined.

  • PDF

Ventricular Septal Defect with Aortic Insufficiency: A Report of 7 Cases (대동맥판막 폐쇄부전증을 동반한 심실중격결손증 -7례 보고-)

  • 조대윤
    • Journal of Chest Surgery
    • /
    • v.12 no.1
    • /
    • pp.50-55
    • /
    • 1979
  • The development of aortic insufficiency radically alters the physical findings which are generally associated with ventricular septal defect that was not hemodynamically significant, and the combination of the two lesions produces a typical clinical picture, that may be serious and life-threatening when it is left untreated. Therefore, the selection of patients, type and timing of surgical treatment is considered to be important. Among 114 cases of ventricular septal defect treated surgically utilizing cardiopulmonary bypass in the Department of Thoracic Surgery, Seoul National University Hospital, 7 cases were associated with aortic insufficiency. 1. Five cases were male, and 2 cases were female. Ages were from 4 years to 24 years, and mean age was 11.9 years. 2. In all cases, ventricular septal defect was closed with Teflon patch. In a case, a aortic valvuloplasty and in another, a aortic valve replacement with Hancock valve 23 mm., 5 months after the closure of ventricular septal defect were done. 3. Four cases were type I ventricular septal defect by Kirklin`s classification, 3 cases were type II ventricular septal defect, and diameters of ventricular septal defect were from 3.5 cm. to 0.7 cm. A PDA. was combined to a type I ventricular septal defect. 4. In 5 cases, herniation of the aortic cusp through the ventricular septal defect and in a case, annulus dilatation on the aortic valve was noted. 5. Two cases with type I ventricular septal defect and severe pulmonary hypertension expired. A re-opened case with type II ventricular septal defect expired. 6. Four cases were alive, and all of them show decrease of pulse pressure and aortic insufficiency.

  • PDF

Tunnelized-facial Artery Myomucosal Island Flap (t-FAMMIF) for Palatomaxillary Reconstruction: A Report of Two Cases (터널화 안면동맥 협부 근점막 도피판을 이용한 구개상악 결손의 재건: 증례보고)

  • Ryu, Da Jung;Jang, Hyo Won;Park, Hye Jeong;Kim, Hyung Jun;Cha, In-Ho;Nam, Woong
    • Maxillofacial Plastic and Reconstructive Surgery
    • /
    • v.35 no.2
    • /
    • pp.100-106
    • /
    • 2013
  • There are many challenges for reconstruction after intraoral tumor resection. Especially, palatomaxillary reconstruction has two primary goals: closure of the oronasal communication and re-creation of proper myomucosal function. Prosthodontic treatment using obturator and several surgical procedures are selected depending on the size and site of the defect, the difficulty of operative procedure, operation time and donor site problem. Above all, it is considered that radial forearm free flap is the first choice for palatal reconstruction. Our department introduces a novel method using tunnelized-facial artery myomucosal island flap for palatomaxillary defect reconstruction, which can successfully reduce donor-site morbidity, and duration of surgery and hospitalization.

A Study on the y+ Effects on Turbulence Model of Unstructured Grid for CFD Analysis of Wind Turbine (풍력터빈 전산유체역학해석에서 비균일 그리드 무차원 연직거리의 난류모델에 대한 영향특성)

  • Lee, Kyoung-Soo;Ziaul, Huque;Han, Sang-Eul
    • Journal of Korean Association for Spatial Structures
    • /
    • v.15 no.1
    • /
    • pp.75-84
    • /
    • 2015
  • This paper presents the dimensionless wall distance, y+ effect on SST turbulent model for wind turbine blade. The National Renewable Energy Laboratory (NREL) Phase VI wind turbine was used for the study, which the wind tunnel and structural test data has publicly available. The near wall treatment and turbulent characteristics have important role for proper CFD simulation. Most of the CFD development in this area is focused on advanced turbulence model closures including second moment closure models, and so called Low-Reynolds (low-Re) number and two-layer turbulence models. However, in many cases CFD aerodynamic predictions based on these standard models still show a large degree of uncertainty, which can be attributed to the use of the $\epsilon$-equation as the turbulence scale equation and the associated limitations of the near wall treatment. The present paper demonstrates the y+ definition effect on SST (Shear Stress Transport) turbulent model with advanced automatic near wall treatment model and Gamma theta transitional model for transition from lamina to turbulent flow using commercial ANSYS-CFX. In all cases the SST model shows to be superior, as it gives more accurate predictions and is less sensitive to grid variations.

Performance Analysis of Anti-islanding Function for Grid-connected PV Inverter Systems under Parallel Connections (병렬운전하는 계통연계형 태양광 발전용 인버터의 단독운전 검출 성능 분석)

  • Jung, Young-Seok;Yu, Byung-Gyu;Kang, Gi-Hwa
    • Journal of the Korean Solar Energy Society
    • /
    • v.33 no.5
    • /
    • pp.34-40
    • /
    • 2013
  • Islanding phenomenon of photovoltaic system is undesirable because it leads to a safety hazard to utility service personnel and may cause damage to power generation and power supply facilities as a result of unsynchronized re-closure. Anti-islanding protection is an important technical requirement for grid-connected PV system. Until now, various anti-islanding methods for detecting and preventing islanding of photovoltaic and other distributed generations have been proposed. Most of them are focusing on the anti-islanding performance of single PV system according to the related international and domestic standard test procedures. There are few studies on the islanding phenomenon for multiple photovoltaic operation in parallel. This paper presents performance analysis of anti-islanding function for grid-connected PV inverter systems when several PV inverters are connected in parallel.

Experimental and numerical investigation of a surface-fixed horizontal porous wave barrier

  • Poguluri, Sunny Kumar;Kim, Jeongrok;George, Arun;Cho, I.H.
    • Ocean Systems Engineering
    • /
    • v.11 no.1
    • /
    • pp.1-16
    • /
    • 2021
  • Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

Management of Traumatized Gingival Wound Using Tissue Adhesivein Dental Hygiene Practice (치위생 임상에서 조직접착제를 활용한 외상성 치은열창의 처치)

  • Chung, Won-Gyun;Noh, Hie-Jin;Jang, Sun-Ok
    • Journal of dental hygiene science
    • /
    • v.3 no.1
    • /
    • pp.1-4
    • /
    • 2003
  • The purpose of this paper is to present the potential application of tissue adhesive in the management of traumatized gingival wound in clinical dental hygiene practice. Cyanoacrylate adhesive has been used for closure of superficial laceration without suturing, which is available in periodontal and oral surgery. Small gingival or mucosal lacerations may occur by improper or excessive instrumentation of the dental hygienist during scaling and root planing procedure. In this circumstances, tissue adhesive is very effective, simple, and convenient method as an alternative to conventional wound closure by suturing. The tissue adhesive consists of monomeric n-butyl-2-cyanoacrylate, which polymerizes quickly in contact with tissue fluid. The sutureless treatment of gingival laceration with tissue adhesive has advantages of good esthetic results, less trauma, time saving, antibacterial and hemostatic effects. In addition, local anesthesia as well as re-visit for dressing and removal of suture are not required. Use of tissue adhesive could be beneficial to both dental hygienist and patient in the management of procedural error.

  • PDF

Art and Collectivity (미술과 집단성)

  • Kwok, Kian-Chow
    • The Journal of Art Theory & Practice
    • /
    • no.4
    • /
    • pp.181-202
    • /
    • 2006
  • "When it comes to art, nationalism is a goodticket to ride with", says the title of a report in the Indian Express (Mumbai, 29 Oct 2000). The newspaper report goes on to say that since Indian art was kept "ethnic" by colonialism, national liberation meant opening up to the world on India's own terms. Advocacy, at the tail end of the 20th century, would contrast dramatically with the call by Rabindranath Tagore, the founder of the academy at Santiniketan in 1901, to guard against the fetish of nationalism. "The colourless vagueness of cosmopolitanism," Tagore pronounced, "nor thefierce self-idolatry of nation-worship, is the goal of human history" (Nationalism, 1917). This contrast is significant on two counts. First is the positive aspect of "nation" as a frame in art production or circulation, at the current point of globalization when massive expansion of cultural consumers may be realized through prevailing communication networks and technology. The organization of the information market, most vividly demonstrated through the recent FIFA World Cup when one out of every five living human beings on earth watched the finals, is predicated on nations as categories. An extension of the Indian Express argument would be that tagging of artworks along the category of nation would help ensure greatest reception, and would in turn open up the reified category of "art," so as to consider new impetus from aesthetic traditions from all parts of the world many of which hereto fore regarded as "ethnic," so as to liberate art from any hegemony of "international standards." Secondly, the critique of nationalism points to a transnational civic sphere, be it Tagore's notion of people-not-nation, or the much mo re recent "transnational constellation" of Jurgen Habermas (2001), a vision for the European Union w here civil sphere beyond confines of nation opens up new possibilities, and may serve as a model for a liberated sphere on global scale. There are other levels of collectivity which art may address, for instance the Indonesian example of local communities headed by Ketua Rukun Tetangga, the neighbourhood headmen, in which community matters of culture and the arts are organically woven into the communal fabric. Art and collectivity at the national-transnational level yield a contrasting situation of, on the idealized end, the dual inputs of local culture and tradition through "nation" as necessary frame, and the concurrent development of a transnational, culturally and aesthetically vibrant civic sphere that will ensure a cosmopolitanism that is not a "colourless vagueness." In art historical studies, this is seen, for instance, in the recent discussion on "cosmopolitan modernisms." Conversely, we may see a dual tyranny of a nationalism that is a closure (sometimes stated as "ethno-nationalism" which is disputable), and an internationalism that is evolved through restrictive understanding of historical development within privileged expressions. In art historical terms, where there is a lack of investigation into the reality of multiple modernisms, the possibility of a democratic cosmopolitanism in art is severely curtailed. The advocacy of a liberal cosmopolitanism without a democratic foundation returns art to dominance of historical privileged category. A local community with lack of transnational inputs may sometimes place emphasis on neo-traditionalism which is also a double edged sword, as re kindling with traditions is both liberating and restrictive, which in turn interplays with the push and pull of the collective matrix.

  • PDF

Development of Contents in Fundamental Design Education for Fashion Design (패션디자인 교육에 있어서 기초조형 교육내용 개발)

  • Cho, Jung-Mee
    • Journal of the Korean Society of Clothing and Textiles
    • /
    • v.34 no.8
    • /
    • pp.1265-1276
    • /
    • 2010
  • The carelessness of basic design form in education can result in a lack of creativeness and critical thinking ability that will decrease adaptability in a rapidly changing fashion industry. If the fashion education just repeats the previous education of basic form of design, it will be impossible to create original value in fashion design. It is necessary to re-establish the characterized program of the basic form of design education. This study develops concrete educational contents of the basic form of design that can be applied to fashion design through the study of the fundamentals and the concepts of the basic form of design. This study is the basis for the cultivation of talented designers with creativity, forming ability, problem solving skills, and critical thinking ability. The research method is the fundamentals, specialty publications, and designs studied. As a result, an education program for the basic form of design to be used in fashion design education was developed. The development of education contents of the basic form of design has been developed as the plane form that aims the perceptual and emotional effects through the expression of the objects, through the use of dots, lines and planes that are the basics in forming practice and the expression of the abstract images. This suggests subjects composed of the various progressive forming conditions with the abstract dots and lines. In this subject and during the process of the idea, development, and fashion design, the overall unity, harmony, and the theory of gestalt (closure, proximity, and similarity) has been obtained. As a result, the content of the subjects was developed from the perspective that comprehensive decision making skills made from the process can lead to an improved sense of the fashion design.